ie Ihe Ws Ts A nace i : ft ate Ua Gah i My ; ieiel Let it we Nike 3 i i Me i Hed FeO bait Batig PHA : ns nies + Hat tt ’ in hy Nh “i on ae ae digas diya eat 3 die hy mde ee { RES its it nih uate Helge Ki Pid Alot | Leben qiieeg im = {he i iy = =o : ial ie t) a i kin Cat a Way ya ry Siac) ‘ i Why! Ny pede dave +f wud Nataly: a ht i ' beta Snare) HD Tr ee ed ate bey tay vibe oy Manone ru | ri is crn si . vi Hea i A uh Wa ne) bee Mayes if mi APOE at Ss each - a aati ‘ot “Ae atarehy Malin) eh ‘ii it est on es has cig At Bais MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition—Prof. Dr. Sorauer In Collaboration with On Dr. G. Lindau And ODr. L. Reh rivate Docent at the University Assistant in the ae seum of Natural of Berlin History in Hamburg TRANSLATED BY FRANCES DORRANCE MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition—Prof. Dr. Sorauer In Collaboration with Prof. Dr. G. Lindau) 4nd Dr. L. Reh Assistant in the Museum of Natural Private Docent at the University History in Hamburg of Berlin TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT [ee EEE oa i.) eiene ia al ‘J 4 na 7 < ; Att i} , a 1 i) ; Pit ‘ a : of | Dt) st 4 , | : a, ee ‘ a i ey uel ty ate. tees a ie 4 = tay sf thas Copyrighted, 1922 By FRANCES DORRANCE ©0.a659795 Z © © oa (\ Ly | Vv ERRATA. Contents, page X, line 23, for Leguminaceae, read Leguminosae. Page 8, line 23, for stems, read shoots. “cc “ec 23; 53; 93; 99, 167, 204, 232. 265, 273; 293; 338, 339; ce ce Fig. line ce ee ee 420-22 430, 442, 461, 498, 548, 696, 723; 765, 802, line Fig. line ce ce iz3 iz3 ce Fig. 855, line 16, “ preventive, read preventative. 5, ©“ Prunualus, read Prunulus. 4, caption, for Schomunzach, read Schonmunzach. 34, for Mucor spinosa, read Mucor spinosus. 22, “ Arahanose, read Arabinose. “cc ay. Fusiarium, read Fusarium. 5, ‘ Leguminoseae, read Leguminosae. 21, “ Dioscora, read Dioscorea. 19, “ Zolites, read Zeolites. 6, “ B. substilis, read B. subtilis. 7-8, “ Clostridium gelatinosa, read Clostridium gelatinosum. 18, after Mold fungi, insert (Mucor stolonifera and Asper- gillis niger). 20, for homogany, read homogamy. “fruit spears, read fruit spurs. 11, “ Fruchtuchen, read Fruchtkuchen. ‘““ Leguminaceae, read Leguminosae. 11, after inner growth, imsert (internal intumescences). 80, caption, for Acacia pendulata, read Acacia pendula. 24, after rough places, insert (scurvy spots). 1, for Chapter XL, read Chapter XI. * psycho-clinic, read psychro-clinic. Bacillus pseudarabinus, read Bact. pseudarabinum. “ce -38, “ Grapholithia, read Grapholitha. 36, “ Boulle céleste, read Bouillie celeste. 186, caption, for formaton, read formation. 11, for Trula, read Torula. ce lel, vernatis, read vernalis. vil TABLE, OF CONTENTS. Page PREPACE forthe (German! CQULIOM 2.0. pie Seieet seine « 34 Section 2. HISTORICAL SURVEY. Blciue rn tenille Qivecaev Age nc ee ae aie Hg Oe RAInE oor tse ain ot ener ato aor 41-70 JNIDIEIBINADID © a ele Be sec eet See per lene aioe Gen oie ters Linc Saas ercitly a cnrcraseecreaiaaon 70 DETAILED EXPOSITION. Section 1. DISEASES DUE TO UNFAVORABLE SOIL CONDITIONS. Chapter Io. Uhe location ot the soil <2 2.2.4.6 eee. eee eee eies u eee ao niall 72 TElevationeabovie Seaulevielusnte cs seeieic a eceine een scr iio rssrs eusiencler= 72 a. General changes in habitat. inenelationatonhenbaceouse plantsue epaerciittertsetietetste elle terete tet oll iliaie 72 Development of the aerial axis of woody plants ......-...--.-.-+++--e y, Adjustment of the root body of woody plants ........-...--2eses+ secrets 7 bieSpecialincases: Of CIS@aSe joie wisi ice ce im ain 153 Effect of drought on field products ............--- cece cece eee e et eees 155 Effect of drought on germination .........--- 2 esse eect tree ene 157 Areatimienite On tieeeSCeCSia ie cvs ire lehauera close ee ores 5 ener efo Lene (=) 91 = 1215) cele nielienane) +) )@heloie 158 Blastime in gotains and, legumies ot... ne) evi 2 ee 2 cites coccinea eines 160 Vill Page Thread formation in the potato: (Milositas). <...<... ces teens ee eee 161 Diaphysis (Growing out sof the potato: 26/44; « > oo eee 163 Formation, of tubers without solange: 235. 22 «ite cea os. 1d eee 164 Aerial potato'tabers 2. J. =. Seren sooo. sia. s ot ake ie oe ee 165 Premature. ripening “or. iruitsis. saat ene ceina.< eas forsee abe eee 165 Rusty “plums : saan sees eee Bsa ahr moan ae asreet ea 166 Further phenomena ‘oi premature: ripening 4.1.7... -..0- 462s 2 oe 166 Mealiness vob iimaite mi. 20 40 ones ia Senta sie hore ke eee Bo ne oe . 166 Bitter pit 1 the-apple 24,csesn.s Seaee Aer Oc Oe nee ee 168 Stoniness ofe pearsand lithiasis 2. sen.snoe sasiem Foie See ee 170 Wanictics onerrattsuitable fotediye sOllS aan meni eee ene eee 174 SEUMbinig OL Mp IAWES 2c --.5 oo = ..ese eee ee eee 196 Burninguor plants inmmOist: sOllsi se yea eee ioe eee eee 199 Delayed seedings oes watncuxse roe teste cae tre Ae eee 200 Sourine ob seed |...) < Seuss mracie sie seaeceine ope eis eile ed ee ee 201 Souringvot; potted: plants: ). ccc. ooeG hele arid hte Cae See eee 203 Inyjudicious, swatering oie Goes ese ocean ee ne eee 206 Use of saucers under potsiizes oon. hho ce sss cece ea eee See 208 Runnings out of potatoes: eet chess scene ch eee Oe eee en nee oe 208 Sensitiveness! of the sweetucherty: | (sh..cne nt tee ee ee oe 2 Tan: ‘diseaSe® q2isics ois’: «biome eon css og BGR cee Per en eae Oe eee 209 Girdling ofthe red: heechw iss pn oe ae ea ee 210 Root disease on the truexchestnimtGMallmeno)) ane ae ae ete ae eeiee 219 Rootblightzofsugarsandstodder beetsims a -eeee eee eee eee ee 220 Tropicaltplants:: iets: ote oe Ca eee oe ee ee eee er Root-fot of -supaf ane» <7.) bck es So ee ee coe eee 227 Diseases: of cotton: #56 css ossin'. 00 21os 6 te We Sie ome Te ee 228 Castor ‘bean: culttineS: Sonus: hoo ee eee er 229 TP OWACCO a acs a:c\o 0.0% 55a aies ete tela on albiab slate Sie beetle ae Rane ne 229 Goth e © 5.45% bus,4 Sirota Sew Rioters Sere Oe ak rae eee 230 Cocoa and tea. ts eee tien lak oc See OEE ee eee 231 Other tropical: plantSi jy neeak sae eee eee ee eee 231 Means for overcoming the disadvantages of heavy soils................. 232 Tarrowite » 5 o.c0i./.2)5 Gas tec la asela ere ek eieletors Cs ee an ee ee 236 Use of lime, marl. and plaster) 52 .tic2 sede srk oe oe eR eters 237 3, Disadvantages: of. moor ‘Soil. .... 2.02. .cc. jms oe ie Ae ete eee eee 240 Acidsin the soul i. 50.5 cso 0c So ao cate ie et ee lee ee 240 Raw, humus. eee. sec. ed cage ot + acre pie sre a tee eg 241 Meadow Ore...) 55 fos 50 0 i eleleods sinyn age cscs amare oe ese te ee 243 Botsoning, of the soil by metallicysuliun =e see eee eee eter err 250 Susceptibilityator irostvot moon wwecctatlon, aenehete ae eee ee eee ere 251 The usefulness. of the spruce) c/o) sees a ieain oe is Rite et eee arse eee tore hole 253 Changes in} moor soil through cultivation: .4--pe0-oe aoe peel eerie 256 Rotten Danke Were. his Sects oo sore sie sla eiedaue ree eee nes Peer 258 Horticultural smoor “plants: 2... 5/1 [a5 ogee eae ieee eet 260 Specking of corchids. 2.4 2....03% so deste er en eee cient ee ciscer- 261 Chapter’ Ill. Unifavotable chemical, soil constitutions) 2... .- .--02 4. eerie 264 1. Relation of the food stuffs to the soil structure ....... ES Aon cusr rcs Serine 264 A. Soil absorption resulting from chemico-physical processes .............. 264 B. Work of the soil-oreanisms 2. 0c sceuss oe «cette ea eee ne 268 ix Page 2. Kelarion of the nutritive Substances to, the plants: oo. ..cc.5-c.nccksscsnevsece 274 A. Lack of moisture and nutritive SUP DSPUNEC SN 0k SISter sok lene nis alenrnd 275 eMC Hed I SHR EM set stacrersoeos « 2 eco Sits Ld ecksa wees hecen eb aaeee 275 influence of the various, plant coverings: i .0.202..000.2.5.000ee0000s 275 AVVi1!| tir) open iny eer eee i Sete eg ame a TN, a ne a 276 Change in production due to lack of moisture......................278 Discoloration OLE MOR yy MIANESHs aa) ry- oS owls oe Stele Moke Aca Yate." see 270 INCOR CONG AMON ME “EAUNY od s.o lated alesis hci eee «oes wid C4 oh tice sum sees 281 “TERSOIS*— OTE TVS eh ape eae ste ec Rae oO 22 “Leaf scorch” of grapes, “Parching” of vines, “Red scorch”........283 Yellowing due to the grafting SiS Sh, St Eee ana 284 Premature: drying .of) the “foliage 25. 42.025. 0.5.0. 0eccsen ds esa nsec 284 BUI OI Oe OL DOIN LASS (reise et a tet A oh 05 5.012 ial eons wg aa eee 285 SUPE SEND 2 elle De ets ain a ge tS es La Eg eg 285 WikerpCoLer Oledp plese certs ae ee ters le oc-e cls cas oolgee PA eae 286 b; Changesi in production due to a lack of mitrogen ........:......06+000: 287 Stagvarloumcondiionse im Cryprosaims. eee see. ei) vasseste sie 287 Production of sterile’ blossoms (Sterility). .... 200. o.' 0.62 lee ne oes 289 SO RGHIESS THRUST RSE Sere ne cnc a RE (0 ehaydo tao lewd Seu Sites eieac ss els aeons sence ok teins ac rae 205 Dropper otmtacwtniite. eyes ta. scot meren cane teee ceeibins s eules 206 Drying of the inflorescences on decorative plants .................. 206 ORAL ONO IMO Sa ccea awe sooo. cin cs eee ks oe mclaren Sl ee ces ek Sine 207 e. Changes in production due -to a lack of potassium ../...:..........--- 208 ds, Changes in “production due toa lack of caleitim {2.020.062 bs ste beens 301 enG@hanges, dye toyal lack of maemesitnd 32) c.. «2 vi cee clcllS sic uae as vores ene 305 f. Changes due to a lack Oilme hl oritiies oct ey ee hI nao eas Oe ee 306 g. Lack rate ifonpand: jaundice! “Gicteris)\i; sos )-scc tieiiea tens sie) Aeas tie 307 h. Changes due to a ‘sek of phosphorus, and sulphur... .cacs<.as sss nas ° 312 in Chancesedierto ca lackrOn.OxyiPEM ber a) oe eto Ge a 403 f excess. of plosphoticvacid! ...c+.acn2 Eee eee we SPE oo on Sasa cls oe 405 Salxcess Ol) Carbon=dioxid: oh ei. cece two olen an eee ee 406 Section 2. INJURIOUS ATMOSPHERIC INFLUENCES. ChantensiVe,” Loo diye ait 50s as Aah ease cies so oe yore dee eee 408 anya Vac EO MDTIAS)-*. 2 ayeeiccisteretd as recente ot eters Dna cece OR Go Ee ners 408 BretOhinkeom die MO) MEAb ac sucess Seein (ele ae te ea te eee ee ee ee eee 4II LENS val\6) 1002), Aan re ie NON: 5. te hah eam, EMRE Nan MaMa RR. picks ta rg RS Lnlg on: A412 Heart rot andidry rotjot. fodder andusnear beets... .....2. ces et scenes po eeeee 415 Bawuty development ok ther plossomsinacc ts sakes te eee he ak eee ee ee ee 416 ELOUS Get P latices toa s 5/5 ois ce A ete calcite oa oc oe Cee aoe EE Oe ee eee 419 Eland: seeds in, the Memumimacetec: c....500s ods oe Game on ee ee ee 420 Chaptem Vo. Excessive ahumidity: 7 a6ser os eterna ue Seow eee eee 423 Mode of growth with continued atmospheric humidity ....................00000% 423 Influence of moist, air.on plants injured by drought >. 272s 022222 ones oe ee oe 425 Carle OUT SRO WES. A5 oan Coe ec ee oo. Cee ocd oes Ree aR Ae ee 426 Gorkatlisedise. Om thevCactl, . X; ‘Blectrical dischatees .25 Ahecsc akc Ste ee ee eee 480 Blasttesiof Uiahiinani ge’. «r,s ste cin ehh ac acyeciscleasecncpee Meee es ool eee ee 480 ldeht Of conker, OPS <4. teicred atc es «ani noes Oe ee eee 487 Differences between lightning and frost wounds in conifers................+..:- 480 hayuries;to-trees' in cities “and “towns: 2s: :... 21. sincen cee ae eee 403 Pttectsob-spray lightning- on erapevines: «as... .-0ee oe ok eee ee 493 Spray: lightning: on fields andmeadows. ...::<.a..ee.c-eee ee ae eee eee 495 Disadvantages in electro-culture ...... A at eae s rine and tioned 6 nacc 406 Chapter Sl ‘Lack of Meat iio ei.s,.2teees bots tee eee ee 408 A General SUrveyiiei oo ois eda os wks fe tod Se Oe ee 408 Lite phenomena at low temperatures’ <5. =.5.. Soce ee eee e eeeee ee 498 AUEMIN ” COMOTALOI » miata Sets sucess no eee 752 Waste water containing iron’ ‘sulfate i... .3 Scenes oe eee ee 753 Waste water containing copper sulfate and copper nitrate ..................00:- 754 Chapter XTX. Injurious effects’ of ‘cultural. methods 5-5.-02 eee oa ae 756 C@atine substances’ ...... . 3: i652 20 2. eae eden Be ee eee 756 Amaesthetica 5. heeds See cak Hates Ge Re eee ee 765 Injuries ‘due to fertilizers :,. 6.20.55 sceseen de bone ee cee eee 767 Section 5. WOUNDS. Chapter XX.- Wounds: to.the-axiall: organs... 22. ateemee nee eee 772 General GiscussiGh ojos. ).< 4 ooa5 oe owe fee oe see eee 772 Scarification woundsso. 50. 6c. 5 £5 5) ae ies oes Be ee eee eee 776 TMISCRIPTIONIGS: «2 52) 0F Secs dicls: stele a iarw ¢ « a uo nee ek eee ene 781 Lajury “due to. wild animals) 3... iv.<.0s nae eiee re ee eee eee 781 Overgrowth of cross wounds in many=year-old tre@s ..J)..0.se205 e050. 05s. ee 783 Overgrowth: processes, im, year-old) branches <. s2a.+e eae oe ee 785 Ksip@lane” calls. oo cee Se ewes ncinckin ate seh Ue oe > Se Cae eee 787 Page nytimteSmt OME em Dak amepres rrr rere serie eter tater sinys ciate eso waccee st) 6 casio ee Baselne cakaoters 797 SEO GICA ES LILV.C VamePeerore axee eiepeena aie aes Serie cae oe GES a lg wae oc vies oop evened Giene e 797 eGSOIA MOUSE RUALMMNGEI NS PREG Gorse cid reels cei de siaids Sm oe ¥ealee bbea ae goes 805 BendingeotetiemDrancne Sarre tccis cei coe ic hoe ees ma cicciseroes oa mie eee amewes 810 wiseires Ob Cer DEAREHESH cet ck ecinscis seals = cla. cicesisice soo hud tice be tidedu lesees 815 EC CEO CONS ERIC UUM MEIC ARIS ies ciharattycctsiefee erste Sie. chspevs a Sicaver ea ela) onde aie aveteue a eels 817 Rranchwcuttin gsr cmc citer cece som els a dcclee ais oo em aid tits a tee eeeoaitin wate 821 Wtlization on wartoussaxial organs for cuttings 4...5...........seesc.+scccesee 825 GE TERS Secs ie aS SS ie cars oi OP a or eee 29 @Culatronmmo tem Uc Cintecele ie crs Niklas oiclap stern miekcleid ain eitig worelns oar eure 833 Copalisenmantorathine. 3 esos 6 wakes eb AMY dd ciaisiebe imide Cade ee vealed eeeta 838 Mongevityoteranted or buddedmndiyiduals)..0---2-...202-e-s.-c22+.--+es00e 839 Mintitialeimbliences.on isctomeand: Stockssrceieciem sce cdse eee e - cece a6 de vce cle ere 841 iINattuiiralmepLrocesses! OfaCOaleSCenCemascisnim acim cnt cise eis Sitters 6s Peels Sele dines 847 Wound protection meraecran dace ees Morin teas no tee) Shh ciisha biesua ide sea ceed shone 850 Wome S resiient Ae a aie beGeclel ochre @ aro orc cre NOC noes 4 Cie Ce I et oe ear re a 851 Shimyprextidationwonetrces mere an ernie sot 1ae erat ae tari a cae aioe state Meee ee 54 ROO tp eLGe S mirpeeeern ene er mem ere lacie low GS pe widin onesie os Ste Sele Gdee wae s Vlees 856 Grange verorow MCG GeS prises ae dh Se sya aise o eRe oe aeliacins Gh elaine eee vee eels 850 Banke cUbecswen cre eect etn 2 ices crac tak. wii ae ye Looe Ae a Hades ewes 861 ILGei TOUTES Biases c 6 8 cILeS Rae aco E CR NCR Cacit ee RIE TROT ee a 871 IL SENT KOT WANES, Sey Shes APS rt SP CG eo IRTP ORL G.C Te CPE 873 Inia yaEO mee eNO ews veto etie ra.dlsi co es aietalde yar ooo aes wee ieis ales 8% oa Siw edocs 879 SHED OIINOTE. 55 rchaeln SetGac SNS COL SOREN EE Bn Cr PE REOL Clone rer err a i or eae 881 XIV LIST OF ILLUSTRATIONS. Fig, Page I72.--Roots. of: Quercus Pedunculaia.erown between.rOcks 24200. /2.005 ot. 0 eee 79 e-33,- Sprucesroot.wath fleshy. conmpensatony hOOt sete eee eee ee 1 ae Scott A>. Stilted sprucesnéar StwonmMlunzach -sasnnadededaeey ass akan aoe sede. eee 93 mad... Stiltedipine=trom JGriewald <5 rcaccavec 20 eed De cis be eee Cake ae ere ire 95 7aO;. Resinvwalias ongstiltslike oats. Of the. pine ts a4 2 240 «ens eal eerste eee orate 06 G, . _ Rye seedling .with too vdeep: Sowing fe). bil. ca ttae en oes nena Dale ieee eee 112 10. - Cross section through the lowest node of young rye plant’./.....:.......... 114 Sie Wheat#erains-with roots from -testa at tip of:séed grain *?. 2.220.054. Lai... 116 Rae eal Microscopical enlargements of igh a0hse rr erties prone cine 117, LL ae DWarEespeciiten: Ol, GI GtODLWSE st suas e's oo aes © 62 25 eh odes hoe ee eee 143 16. Cutting from potato tuber with the flarient diseases 23... 8G: Sha wee ae 162 Mya ser Olina tede+POtatO!. salz soiera sewed soem niealy retheanks 22 iz fre guia ene eee ee rene 163 © 78. Parenchyma cell from ripe apple after treatment with undiluted glycerin... . .169 iQ: + (eats uysensed swith LithiasiS..iss.resscaay ev ede aaa ve rs eae? a3 se ee crs tees I7I 2: - -Crossssection. of stone-cell: from -pear shown ih: Fig. 19.... 007.222... 001.2: 173 “21, 22. Corresponding sections through a cultivated. and a wild carrot............. 181 © 23. Apple. root- with ruptured. tan. spOts.......... eee ee eee e etre deere ene ees eees 210 pa, . Cross-SeCHon. througina.tah-spot iain Apc. tOte ry... 08s cleans. eee ee 20 25. Bark of apple tree “trunk WAL GLAIL SDOLS! piece sees one oe as ee eee renee 212 20m | Cross=scetion-through tam Spot ons thunk Grapple thee maser er -leers ee eie 208 27. Chetry branch with’ tan cushions: . ..s .nqase ss qace-s 1s ~ o ea eect 214 2eF iNew weodon a bane wound of aechernmy tnunkeseen ose see toma + cee err 216 BO. A Ae SiMeAdOW ORG, PINE M.< sds. ayosaisos meme MO mmEDe cae ook ok vane eee an eer 246 20. . ROOLSCOL ane Oak In -MieAdOW “OL ho. syoc 2 routes «© alee @ SRA ogee ronan ne 247 31 Moonupine with flatly extended “roots? ster. SS... os ee ae ee ee ee 248 Bo- (Canker-like. wounded place on, the, moor pille*s <. 55. «222. ae ome oo oe ee ee 249 B32. Sprtice family produced-by natural layetmic 2225.0! aca 5 ceee aetna 254 Sec Oak with a tormation of sinkers Wai, ac. cmt 32 ass mentee ree een 255 mes. Monldy bark scale’ ofa moor pine Bie i.e: vie tee oie ce eeat ie ee 250 Be SCCMIESS (MOAT bu. Sica ee» via dsl bea ecals aac oc ee 660 isc. Twig of cherty with gum cavity. 4-ck oeem.c eee eae) ee 2 eee 701 156, Nuclei of gum-formuing: tisSie: ./101.j. eles oe eo) eleia ice sie = alin ae 704 157. Tracheidal parenchyma of Pinus Strobus with resiniferous layer........... 713 158, 150, 160, 16012. IResin centers it amber frp ete aoe eee te 714-716 162. Oat leaf ‘killed“by chiorin. fumes: =... ise ese eee ee ese one eee 726 163. Beech leaf “affected: by ‘sulftrous- acid: 7.2/2.5 in.2) en oer 727 i64. Birch leavesinjured by Sulfunous acidis > (2%...) slo ee ee 728 r6s. Rose leat injured by chiorin fumes: 122 2.050022 aere- 2 ey erie ee ee eee 728 166. Beech leaves. injured. by. chlorin. fumes... 0..)./)45. Jone ee eee 728 567. \Birch Jeaves injured by chlorm times:..<-)-< 22-20 -cemese tiie ee eee 729 168. Virginia creeper, strawberry and rose leaves injured by tar fumes........... 733 169, 170, 171. Apples injured by spraying with Bordeaux mixture............ 763, 764 172. Apple leaf with dead spots and holes after spraying with Bordeaux mixture. .765 17% WA 175. Searification wounds sos. oe aioe s sre nis clei ete te Ae eae 777, FS 176. Hollow. pine trunk sic. Pies sae soe ote eels s Oe ae ee is ee eee eee 779 177. Section of trunk of Picea vulgaris with overgrowth of the resin channels. ...780 178. Overerowth of the cut surface of a Dramcti..4:. 2 42 eee 872 208. Leaf cutting. of a begOmiia: Siac 5 ccc wealocle secten sae eres ie ete 875 MANUAL a OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Proft);Dr/G. Lindau ‘Aid ~— Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History of Berlin in Hamburg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT Copyrighted, 1914 » By FRANCES DORRANCE zx a9 Fear SEP 29 1914 | Ociasso5oe .— THE RECORD PRESS Wilkes-Barré, Pa. UD 7 PREFACE TO THE GERMAN EDITION. For the third edition of my manual I have requested the assistance of Professor Dr. Lindau and Dr. Reh. In the second volume of the work, the former has treated of vegetable parasites and in the third volume the latter, the animal enemies of plants. Such help seemed necessary because, since the appearance of the second edition, the published results of investigations have been so numerous that too long a time would have been required for mastering the material. _ Other- wise when the last sheets appeared the first would have become obsolete. Even with this division of the work, this unfortunate condition has not been entirely overcome and an attempt has been made to obviate the difficulty by listing some of the more important recent material in a supplementary biblio- eraphy. If the absence of some works, especially of the earlier literature, is noted the explanation lies in the fact that we have emphasized especially those studies necessary for the support of our presentation of the subject. A more detailed bibliography would be possible only if the individual diseases were treated in monographs. ; I kept for my own work the revision of the first volume, comprising the non-parasitic diseases. The fact that this volume is the most extensive is ex- plained by my standpoint, already sufficiently characterized in the preface to the second edition—because I lay the chief weight on a knowledge of the diseases produced by atmospheric, soil and cultural conditions. The distur- bances caused by these factors are not only the most abundant and perma- nent but also often form the starting point for parasitic diseases. On this account, supported by my own studies and the observations of other investigators, I was especially anxious to show how the same plant species could be changed structurally and in habits of growth according to position and the constitution of the soil. Individuals are sometimes more disposed to a definite form of disease or are more resistant to it, according to the difference in their constitutions. This holds good also for their behavior towards parasitic organisms. It is thus evident that not only must the latter be combatted by directly destruc- tive methods but also the chief emphasis should be laid on the possible con- stitutional change of the host plant. Therefore, we will find the most essen- tial task to be the breeding of resistant varieties. At the time the first edition of this work was published, the undersigned stood alone as represen- tative of this theory of predisposition to parasitic attack, but now many of the most prominent investigators are counted among its supporters. And thus I hope that the idea for which I have fought since the be- ginning of my scientific activity, that is, the formation of a rational plant 4 hygiene, will finally come to full recognition. Primarily, we must learn to protect the organism from disease, and then, through force of necessity, may take steps to heal an organism which is already diseased. In the first volume, the first section of the introduction treats of the na- ture of disease, while the second takes up the history of its investigation. It should be understood by the term “historical” that I did not wish to write a history of phytopathology, which would have taken much more thorough pre- liminary study, but did consider it desirable to attempt to sketch the process of the development of this branch of knowledge, in order to show how the present point of view had developed in the course of time. In looking through the specialized part, the reader may also find that even in the present edition conclusions once based on a considerable number of my own investigations have been abandoned. The aid of illustrations, so absolutely necessary in phytopathology, has been made use of to an appreci- ably larger extent in describing diseases. In accordance with the character of the book, new anatomical drawings especially have been added. In the vol- ume on parasitic diseases many tables have been gathered together for the sake of comparison, in order to make clear to the reader the different genera of one family in their distinctive characteristics. The new drawings were made by Fraulein H. Detmann and Fraulein E. Liitke, whom I thank very much for their work. Most of all, however, I wish to thank my collaborators. With me, they iad to solve the difficult problem of presenting the material in a space deter- mined by contract before the revision. During the revision, we found our- selves confronted by the question either of giving to the whole subject a briefer form than was originally intended, or of working up some chapters in detail while summarizing others. We chose the latter course and treated the seemingly most important sections thoroughly and the groups, which had been sufficiently worked over in other books, in a correspondingly limited way. Schoneberg, October, 1908. PAUL SORAWE R= INTRODUCTION. Section I. THE NATURE OF DISEASE. 1. LIMITATION OF THE CONCEPTION OF DISEASE. Our first task is evidently the necessity for defining the province of which we will treat and for expounding what we understand by the term “Disease.” If we call “sick” only those cases in which the organism undergoes such a disturbance in its functions that its existence seems threatened, we will be in a dilemma when we consider the changing developmental forms of our cultivated plants, for we will then discover that the above explanation is in- sufficient. We know, for example, that our species of cabbage, kohlrabi and cauliflower are descended from a plant similar to bank-cress which, in its natural development as a wild plant, shows no tendency toward the forma- tion of large leaf-buds such as cabbage heads, nor of root-like swellings of the stem, as kohlrabi. These vegetables have been produced by selection and cultivation and are characterized by a condition which we term parenchy- matosis, because the woody elements have been replaced by a tender parenchyma, due to the high degree of nitrogen continuously supplied from generation to generation. In dry, hot summers young plants grown on soils poor in food materials begin to show a marked ripening and, in connection with this, a reddish blue tone in their leaves. In case kohlrabi, under such con- ditions, makes any development worth mentioning, it becomes “stringy,” that is, its flesh is traversed by tough, hard fibres, making it “woody.” Investi- gation shows that the kohlrabi plant by the curtailment of the supply of water and food materials is well on the way toward again developing a wood-ring with prosenchymatic elements, as found constantly in the wild plant. Very similar conditions are found in carrots in which our normal uncultivated plant possesses a solid woody root, rich in starch. Our cultivated varieties, on the contrary, have become thick, fleshy structures; the best containing no starch at all but the greatest possible amount of sugar. Only in the so-called fodder varieties, as, for example, the white giant carrot, is still shown an abundance of starch. Hoffmann-Giessen has experimentally developed our cultivated carrot back to the wild form. Now, is the cultivated form a diseased condition since it actually suc- cumbs more easily to certain disturbing influences, or is the reversion of the 6 cultivated plant to the norma! wild one to be considered a disease? In any case this reversion is a condition which must be combatted as it is evidently unfitted for our cultural efforts. In considering such examples we see that, in treating questions of dis- ease, we shall have to follow two lines of work. We must naturally first keep the organism’s aim in sight. And this aim, which the organism derives from its very origin, is to live, and in fact to live as long as possible. Every- thing which has once been originated persists as the effect of the causes leading to its production, until a stronger factor arises which disturbs the fixed order and brings about other groupings of materia!, form and function (an inseparable trinity). But, up to the time of interference of such a factor, the developed individual, with the sum total of the forces inherent in its substance, maintains its then existing order, that is, its individuality, to which a generally definable age limit is set. This necessary mechanical defense of iis individuality against the constant attacks of exiernal factors may be termed the “force of self-preservation.” In following the second line, the aim of cultivation, developed from the relation of the plants to human needs, is an added important factor. These conditions of the vegetable organism opposing our cultural endeavors will be combatted as inexpedient. But such conditions need in no way threaten the existence of the individual and there- fore, according to the above explanation, are not diseases. Yet they belong to the province of the pathologist as disturbances which must be considered and overcome. In limiting the conception of disease, we meet with similar difficulties in double blossoms, in as much as this doubleness is due to the fact that the stamens have been changed into petals and in doing this have deformed the pistil. This leads to sterility. The length of life of the individual plant is not injured in any way by this sterility, but, on the contrary, is actually length- ened as, for example, in double petunias. But tne aim of the species is affected since such double blossoms are no longer able ‘o produce seeds. If this kind of doubling becomes general, such species must die out in case all vegetative reproductive organs are missing. This variation in structural development, threatening the existence of the species, however, is directly sought for in cultivation and any reversion to the normal, seedbear- ing form is selected out. Here indeed the aim of cultivation contradicts the natural aim and pathology tries hard to overcome the natural trend opposed to the momentary direction of the cultivation, although in doing this, it di- rectly threatens the existence of the species. Such antagonisms are very numerous. In the list of cases in which only individual organs become diseased, one such local disturbance can in- fluence injuriously the organism as a whole, but can yet be useful to the individual. We would cal! attention here to the dropping of young fruit due to drought. The cultural aim is naturally interfered with but the economy of the tree reaps the benefit in as much as it saves the reserve materials, which would have been used in maturing the fruit. As a result of this, the Jf tree is not only in a position to develop the next set of leaves, but also to set numerous fruit buds, which would have remained suppressed had a full crop exhausted the store. When late frosts injure the blossoms and young fruit, the individual organs are certainly severely sickened and fall off later; but the tree itself has the advantage of saving a quantity of food material. As often happens, the cultural purpose can also profit in this case, because the blossoms developing after the action of the frost yield. more perfect fruit and thus an increased revenue. This defines clearly the difference between pure and applied science. Pure science studies the process of disease in itself and can be only cellular pathology, while applied science takes into consideration the effect on the diseased individual and its agricultural significance. We must unite both forms of science since we take the purely scientific studies as the basis of our consideration and-explanation of the economic effects of the attack of sickness. The consideration of the cultural needs forces us to the following division of our subject; first of all, we will have to consider all cases which threaten the individual aim of the organism, i.e. its longest possible life ;— these are absolute diseases. Then we must discuss the disturbances which the momentary cultural aim experiences and which we term relative diseases. These relative diseases may vary since what cultivation considers worth striv- ing for to-day may be neglected to-morrow. For example, with savoy, every reversion of the plant to Brussels sprouts is a disturbance of the cultural aim to be avoided by changing the seed. If we intend growing Brussels sprouts, however, each variation of these plants toward the savoy form is a deterioration, undesirable in cultivation. Finally, malformations are usually unimportant agriculturally but must be considered. Such malformations may be a maturing of organs in a manner differing from the usual process of development. These natural occurrences, which, we believe, may often be traced back to changes in pressure conditions and other mechanical in- fluences due to the formation of the organs, constitute a special branch of knowledge,—T eratology. This is, however, to be considered as one branch of pathology and we will have to draw into our discussion these phenomena so far as their causes are known or may be surmised with some certainty. The method of treating the material which falls under the province of the study of plant diseases or Phytopathology, will have to be according to the following scheme :— I. Pathography or symptomatics, 1. e., the description of the disease according to its individual signs or symptoms. II. Pathogeny or etiology, namely, investigation as to the cause of the disease. Only after the causes are known is it possible to bring into use III. Therapy or the study of healing methods and to draw into the discussion IV. Prophylaxis or some method of prevention. 8 2. THE PRODUCTION OF THE DISEASE. If we have said that we must begin with the individual cells when judg- ing a disease, we must know first of all how complicated an organism the cell] is and how its structure and function depend on the constitution, position and action of the micellae composing it. Let us, for example, examine some effects of “swelling.” The cell wall at a given time is saturated to a definite degree with water of imbibition, that is, the cellulose micellae held together by cohesion are provided with a water sheath with a certain amount of distention. The micetlae will be separated further from one another or will approach one another more closely as the water supply varies; that is, the walls will sometimes become more dense, sometimes more flaccid. Such fluctuations are brought about in the protoplasm of the cell by the action of substances which withdraw water osmotically. Similar processes are observed in chloroplastids, for example, in grain leaves if acted upon by weak chlorin fumes or by sulfuretted hydrogen. The chlo- roplasts are seen to shrivel with the use of chlorine while the chlorophyll grains become pale green, doughy, almost gelatinous bodies with sulfuretted hydrogen. In the cell wall, marked phenomena of flaccidity may often be restricted to single spots. The so-called “bead-cells” in winter grain may be taken as examples of this. Individual cell groups near the larger vascular bundles show bead-like convex centres of flaccidity on the inner side of their walls, which later lose their cellulose character. If young, vigorously growing potato stems are exposed to frost, different groups of leaf parenchyma cells will be found later whose walls seem swollen in lines to four times their normal thickness. In this may be observed the browning and decay of the more dense wall lamellae into stripes which lie imbedded in a homogeneous, ~ lighter parenchyma. In the case of very flaccid membranes, however, molecules will be able to penetrate the greatly enlarged micellar interstices, which cannot force an entrance through the smaller ones, because of their size. If changes in the constitution of the protoplasm have been caused by frost, we find substances passing in and out which could not-have been transferred before by the plasma body. The red coloring matter and the sugar in frosted red sugar beets (Beta) pass easily from the parenchyma of the beet into the surround- ing water. This would be impossible in the cut beet, if it had not been frosted previously. The loosening of the structure of the organic substance is a very normal process the intensity of which depends on the action of ex- ternal factors, such as water supply, light, warmth, etc. If these normal processes exceed a certain limit, they lead to disturbances which so alter the structure and function of the cells that they become unable to maintain life. Every other process of cell life may be similarly affected. Under the influ- ence of different factors of growth, the process may be hastened or retarded. We know that each life function oscillates between wide limits, according to 9 the action of each individual vegetative factor. We call these limits the minimum and maximum and the degree of functioning at which a life pro- cess most favors the development of the organism the optimum. The field of oscillation of the functions about the optimum, within the limits promoting development may be called the “latitude of health.” This should not be confused with “the latitude of life,’ for the organism can still live outside the latitude of health, but its functions are so weakened that its development undergoes arrest or retrogression and this condition is disease. If this cessation of the function is temporary, the condition falls under the conception of “check” and we speak of check from cold or from darkness, etc. But we must guard against the belief that the appearance of sickness er a condition of check or of death in any species is connected with any pre- cise numerical values for the separate factors of growth. If, for example, we take two cuttings from the same plant and cultivate them for some time in sand sterilized by heat with the same quantity of food materials hut keep one cutting in a hot house and the other out of doors, in the end the two will show a very different, susceptibility to frost and other atmospheric factors. The specimen grown in the hot house freezes more easily; that ts, its mini- mum for the maintaining of life is raised. Temperatures, at which the speci- men grown in the open air remains within the latitude of health, arrest the life processes of the hot house specimen. Experiments to determine the maximum and minimum of other factors of growth show .very similar variations so that we may arrive at the conclusion that for each habitat each plant has its own scale of needs, its own optimum, maximum and minimum and therefore possesses its own specific latitude of heaith. Further, the circumstance that the different functions are lost at differ- ent times should be considered. If, for example, potato tubers are left for some time at a temperature of about —1°C., it will be found that respiration ceases sooner than the conversion of starch into sugar. This results in an accumulation of sugar in the tuber which is called “turning sweet of the potato.” If the temperature is raised more slowly to possibly +-10°C. the stored sugar disappears through the increased activity of the protoplasm and respiration. If cucumbers, tobacco and other heat loving plants have to withstand a temperature of +5° to 8°C. for some time, they show a yellow- leaf condition, which disappears with continued increase of heat. The plants do not die, but assimilation and growth are so suppressed that proces- ses, such as the formation of gums, may be introduced, leading to the prema- ture death of the individual. As in the preceding case of deficient heat, deficiency in food materials or light,—in short, every decrease of any vege- tative function,—so retards the normal direction of the functions that the in- teraction of these for the purpose of a beneficial metabolism is misdirected. Other combinations and functional directions (for. example, fermentations ) are now produced, which initiate the ending of life prematurely. The same effect will necessarily appeat every time the maximum of any vegetative factor is exceeded, or even approximated. tO In very many cases a sickness which has already set in is indicated by chlorosis, beginning inconspicuously and progressing slowly. Even if it is possible to observe the very beginning of chlorosis, the beginning of the sick- ness itself has in no way been discovered since the first molecular changes, which have led to the yellowing of the chloroplast, still remain unknown to us. The boundary line where any single factor of growth ceases to be bene- ficial and becomes a retarding factor may indeed be determined experiment- ally but in this we see only the final result and not the course of development ; i. e., the processes initiating this final result. So far as our powers of obser- vation are able to discover, healih and disease represent conditions which imperceptibly pass over into one another. 3. THE RELATION OF THE PLANT TO ITS ENVIRONMENT. In the attempt, undertaken in the previous section, to demonstrate how health and disease present interdependent conditions like the links of a chain, we kept in view first of all the so-called constitutional diseases. By this are understood the disturbances in nutrition which influence the whole organism sympathetically and are the results of deficiency or excess of one of the necessary vegetative factors. Local diseases due to accidental interference must be opposed to these general diseases. In them the organism as a whole in its full reactionary capacity is exposed primarily to a disturbance affect- ing only one individual organ. While the action of the necessary inorganic factors of growth come under consideration in constitutional diseases, in local diseases the important influences are those mutually exerted on one another by the organisms. There are insects which seek out the plants in order to satisfy their needs for nutrition or for habitation, or the plants themselves mutually in- fluence one another. We find as the most pertinent example the influence of street trees on the plants growing on the other side of the hedge row. We notice especially in times of drought that the grain and potato plants found within reach of the tree’s shadow are not only weaker in development but wilt sooner and to a greater degree than the other plants in the same field. This disadvantage is due chiefly to the tree which keeps off the rain and its roots which withdraw the soil water. In the field itself we frequently find different places in which the seed has grown very poorly because the wind grass has choked the grain. The seed was not sown too thin but the germi- nation and first development were choked by cold and deficiency in oxygen because of impervious spots in the field. In spring the soil does not dry so quickly in these places and the moisture is retained longer; the soil conse- quently warms up less easily and suffers for need of oxygen. The wind grass (Apera spica venti) which occurs everywhere in grain fields is less sensitive and under such conditions develops more quickly than grain. Because of its greater size, it chokes out the seedling grain. Similar con- ditions arise in connection with other weeds, which, developing more rapidly, not only take food materials out of the soil and away from the cultivated 1a plants, but also injure them by shading. Actually, however, this struggle for room is the factor first manifested in each plant community and makes itself felt in all field and forest plantations. In the grain field and in every forest tract, the individual first growing most strongly chokes out its weaker neigh- bors. It is the universal question of the strong driving back the weak which must find expression in all community life. The kind of community life just described in its relation to spacial sep- aration can be termed neighborhood in distinction from the mutual influenc- ing of organisms when united in space. A relationship of this latter kind (symbiosis) must be the more intimate since one organism lives with the other. De Bary (1866) distinguished a mutualistic symbiosis from an antagonistic, according to whether the influence is mutually beneficial or detrimental. The terms chosen by Vuillemin (1889) for this relationship “symbiosis” and “antibiosis” seem less fortunate to us. We find examples of a mutualistic community also termed commensalism by van Beneden in 1878, as companionship at table, in the little bunches of rocts of the sago palm (Cycadeae) which occur on the surface of the soil, rigidly branching like witches’ brooms and which harbor numerous chains of Nostoc in the large holes in their bark. The genus Gunnera shows similar conditions. Further, the case is often mentioned in literature, in which a water plant, Azolla caroliniana, resembling our Salvinia natans, in the axillary hollows of the leaves, gives shelter to another Nostoc with longish members (Ana- baena). The most accessibie example of mutualism is offered by the struc- ture of the lichen body, in which fungus and alga remain connected per- manently, to their mutual benefit,—Lichenism. In the same way may be explained the symbiosis of certain mycelia and the roots of Fagus, Corylus, Castanea and some conifers, the so-called root fungus or mycorrhiza which is usually considered a necessary and universal arrangement. In connection with the mycorrhiza should be mentioned the protective device called Bacteriorhiza by Hiltnert and Stormer (in Beta and Pisum). Bacteria penetrate from the soil into the outer cell layers of the roots, actually causing a browning of these layers, but otherwise not especially disturbing the health of the plant. According to Hiltner, however, these bacteria prevent the penetration of other injurious organisms (Phoma, Cie): Finally we will consider the arrangement of root tubercles, which may be found in different forms and grouping on the roots of the Ieguminoseae and form those well-known grape-like bodies in aiders, which not infre- quently may be observed as spherical nests of short branched roots as large as one’s fist. The organisms in the tubercles making the nitrogen of the air available for the plant and described by the students of legumes as /[thiz- obium Leguminosarum Frank, or Bacillus radicicola Beijerinck, are bacteria 1 Hiltner and Peters, Untersuchungen iiber die Keimlingskrankheiten der Zucker- und Runkelriiben. Arbeiten d. Biolog. Abt. am Kais. zesundheitsamte. VolIVan Parts. 1904: je? just as the producers of the silver white tubercles in /sopyrum biternatum which, according to MacDougalt develop extensively in soils free from nitrates. On the other hand, the recent investigations of Bjérkenheim? seem to prove that a fungus is concerned in alders. In antagonistic symbiosis, de Bary has used the expression saprophytism and Johow in 1889 defined the idea more closely by distinguishing holo- saprophytes (those lacking chlorophyll) from hemisaprophytes (those con- taining chlorophyll). Bischoff has contrasted with this the conception of parasitism. Ac- cording to Sarauw* the expression “parasite” was brought into use in 1729 by Micheli for the Balanophoreae*. In agreement with the classification of the saprophytes, Sarauw has distinguished holoparasites (those without chlorophyll) from hemiparasites (those provided with chlorophyll). Saprophytism is the ability of an organism to take its nourishment from decomposing organic substances, while the parasite draws nourishment from the living organism. If we test this classification, based on the forms of nutrition, we find that here, as in all branches of science, a sharp systematic subdivision is assumed only by representatives of a young school, while those of the older and more experienced school are convinced that transition forms exist between the different groups. If relative adjacency be compared with nutrient association (symbiosis) each forest and each grain field shows how constantly one organism influences the other, according to whether the one leaves any food materials, water and light, for the other. Just as spacial separation sets no fixed limitation to the form of nutrition, the sub-division of the organisms into those with purely mineral nutrition and those dependent on organic substances should be abolished. Although plants suited for independent self-nourishment can draw their nutrient material from purely mineral substrata, yet the process actually present consists in their taking humus substances which furnish the food materials in an easily absorbable form because of the activity of a rich bac- terial flora in the soil. The advantages of supplying our fields with animal manures should be thought of in this connection. Modern views have strongly modified this distinction between sapro- phytism and parasitism, since they have brought forward numerous exam- ples showing that the organisms called obligate parasites may become de- pendent on saprophytic nutrition in definite developmental phases and con- versely that saprophytes in many instances can assume the parasitic mode of feeding. Miyoshi’s® investigations give us a clear insight into the way 1 Minnesota Botanical Studies 1894. * 2 Bjorkenheim, Beitrige zur Kenntnis des Pilzes in den Wurzelanschwellungen von Alnus incana. Zeitschr. f. Pflkr. 1904. p, 129. 3 Sarauw, G.F.L., Rodsymbiose og Mykorrlizer saerlig hos Skovtraerne. Botan- isk Tidsskrift 1893. Parts 3 and 4. £ But Tournefort in Mém. Ac. Paris 1705, p. 332, speaks of plants which grow on other plants. oe Miyoshi, Manaba, Ueber Chemotropismus der Pilze. Bot. Zeit. LII, 1894, pp. 1-27. T3 in which such a change takes place in nutrition. The experiments under- taken at Pfeffer’s Institute in Leipsic show that fungus hyphae are irritable chemically and that the direction of their growth may be influenced either towards the stimulating substance, (positive chemotropism) or away from it (negative chemotropism). Indeed their mode of growth also can be changed since, for example, a tendency towards sprout formation sets in with a higher concentration of the solution. The commonest moid species, which occasionally become parasitic (Mucor, Penicillium, Aspergillus) show an irri- tability with substances which almost always can be presupposed to be char- acteristic of phanerogamic plants. Besides dextrin and the neutral phosphoric acid salts, sugar especially attracts fungi, in case the concentration is not too high. Thus, for example, grape sugar in a 50 per cent. solution acts repel- lently for Mucor stolonifer, the active agent of decay of fruits. Acids, on the contrary, and alkalis from the beginning act repellingly. The germination tubes of the summer spores of Urede linearis, a grain rust, are attracted by a decoction of plum and wheat leaves. Especially interesting are the cultural results with Penicillium glaucum, whose hyphae bore through the cell walls of a leaf impregnated with a 2 per cent. cane sugar solution. In the same way they penetrated artificial cellulose membranes and the epidermis of bulb scales which lay on a nutrient gelatine. These are especially important clues capable of explaining the numerous case of sickness from Penicillium. It is well known that this mold, the most abundant agent of decay in stone fruits, first begins to spread when the ripening process has converted the starch into sugar. In connection with the penetration of Penicillium into the scales of bulbs, we find abundant examples in the cases of decay in the tulip, hyacinth and lily bulbs which occasionally lead to lawsuits. This decay occurs especially extensively when wet years prevent the maturing of the bulbs or if the bulbs are stored when containing an unusual amount of sugar and then used pre- maturely for forcing. Thus we see how the cell contents and the cell walls of the host plant can determine the penctration of hyphae and the transition of the saprophyte into a parasite. 4. Parasitic DISEASES. Supported by various carefully studied cases of parasitism, many ob- servers so generalized the conception of parasitic diseases that they assumed them to be present wherever organisms are found gathered together. In many cases this is supported by experiments in which the parasitically living organisms were injected into the host and were able to produce a local dis- ease in the tissue. With this method the apparent proofs of parasitic disease were accumu- lated in such a way that one was forced to the assumption that there could be scarcely any disease which was not caused parasitically. Infection ex- 14 periments in the laboratory led gradually to the knowledge that in many cases of'disease no specific parasites were present but universally distributed fungous and bacterial forms. The further the studies advanced, the more cases were listed in which inoculation with spores of the most common molds, as Botrytis, Penicillium, Cladosporium etc., also the most widely dis- tributed soil bacteria, Bacillus subtilis and B. vulgatus, develop disease in healthy tissue. And finally was recognized the importance of the question how organisms universally present could at times be parasitic in their mode of life and, at other times, saprophytic. Corollary to this question is one which was deduced from rapidly increasing discoveries in many experiments with the same methods of infection; certain varieties or even individuals were resistant while others succumbed easily to the parasitic attack. What is the cause of such differences? Some of the investigators brought forward the theory of virulence as an explanation of such cases. It was emphasized that in each separate case parasitism as a struggle between two organisms had depended necessarily upon which was the stronger. If the weapon of attack of the parasite, for instance, be an enzyme, able to dissolve the cell walls of the host, then it would be explicable that this process would take place more quickly in pro- portion to the increase of solvert ferment formed in any given unit of time. Since it was now possible to prove experimentally that the strength of the attack varied in cultures of different nutritive substances, it could be said that, where it became the active agent of disease and its production of enzy- mes especially abundant, it must have been especially virulent. Bacterial cultures furnished the greatest number of examples of change in virulence. Yet such cases were also determined with fungi. De Bary’s statement con- cerning the frequently encountered mold, Botrytis cinerea, is well-known. He states that the mycelium must develop by the customary saprophytic form of nutrition up to a certain strength before it becomes parasitic and successfully attacks the living parts of the plants. I succeeded in getting like results with the conidia of this fungus. Masses of spores were strewn on delicate Begonia leaves and kept very damp. After several days it was possible to observe that, where these spores had lain in thick masses, the leaf had become diseased, showing a browning of the tissue. Where the spores had lain isolated, however, no attack could be discerned. The action of the quantity of ferment excreted by the individual spores therefore proved in- sufficient, while the excretion from a mass of spores brought about infection. It can thus easily be understood that parasites, like every other organism, de- velop most strongly when the nutritive conditions are most favorable and that the stronger and the more abundant the formation of their vegetative organs, the greater the excretion of the enzyme and accordingly the increase in strength of their attack. Therefore their virulence is raised. But these processes are not sufficient to explain the fact that in one field when a number of varieties are grown in a single plantation, certa'n ones may be completely destroyed while others standing next are but little injured, 15 or perhaps absolutely unattacked. Since in such cases the parasite is quickly and extensively distributed on one variety and not on the cther, although the atmospheric conditions and other factors of vegetation are equaliy favorable, the specific constitution of the host plant in these two cases must have deter- mined whether it would become diseased. Thus we arrive at the conclusion that for the production of a parasitic disease the presence of the parasite alone is not determinative but the constitution of the host organism is also a determining factor. The many infection experiments have led to a classification of the living creatures infesting other organisms and capable of attacking the tissue, in which one group is described as obligate parasites when able te attack the host plant in all stages of its normal development. Of this group there have been separated as wound parasites all such organisms as cannot attack the organism possessing normal protective devices but need the changes in tissue offered by the surface of a wound. Ina great many instances, however, we have recognized the fact that the parasite only finds the environment re- quired for its development when the host has been affected and its functions weakened. Such conditions will appear here as were also decisive in the experiments carried on by Miyoshi (see preceding section). This group bears the name “parasites of weakness.” To this last group especially belong the numerous species which during many generations live on dead organic substances. They therefore must be spoken of as saprophytes which occasionally become parasitic,—facultative parasites. Therefore the boundary between parasitism and saprophytism is lost here and even in those species which are always parasites (obligates), such as the varieties of smut, we find developmental phases with a sapro- phytic mode of nutrition. If we now, however, study more closely the families of our closest para- sites among the fungi, namely, the smuts and rusts, we will find one fact brought into prominence by the most recent investigations and repeatedly substantiated ; namely, that the energy of growth of the parasite depends on the host plant. WWe have examples proving that the same fungus occurs in different species of the same host genus in the same habitat, sometimes grow- ing luxuriantly in many large centres, sometimes sparsely in small forms, according to whether the one species has fleshy leaves and the other thin ones. Indeed, the rusts are so dependent upon their host plants that biologic races are formed which, agreeing formally, nevertheless show differences in adjusting themselves to definite host plants and either cannot develop at all, even when carefully injected upon a related host plant, or develop only slightly. Thus we have a special form of the common black rust of grains on rye, another on wheat, another on oats etc. Mycologists cherish the con- viction that this development into individual races through the accommoda- tion to a special host plant is a widespread phenomenon constantly increas- ing. What else can such a race formation indicate than that parasites in their demands have been and still will be most closely connected with the 10 constitution of their substratum? Tf, however, as previously shown, the closest parasite is thus very dependent upon its host plant, it only goes to show how completely it agrees with non-parasitic plants in its demands for very definite nutritive conditions, and that with a change in these the para- cite changes its character and either adjusts itself or disappears. Stahl’s observations' on myxomycete plasmodia show that we must take these phenomena of adjustment into consideration. If the water in the cul- ture glass was replaced by a 14 per cent. grape sugar solution, the plasmodia either died from this sudden change or shunned the sugar solution. Grad- ually, however, they accepted it, having accustomed themselves to a more concentrated solution (perhaps by a certain loss in water) and indeed in such a way, that, replaced in pure water, they showed considerable injury. In regard to the formation of races, Pfeffer? expresses himself thus; “Present discoveries . ~ . make it clear that the tropistic reachiom of the same species of bacteria, flagellates etc. gradually changes in accord with the existing cultural conditions. Thus it should be understood that in the same species in nature and in artificial cultures there is found at times a very appreciable ability to respond to reactions and changes, varying to a disappearing point, according to a definite stimulus. Indeed after wide ex- perience it seems possible to breed races in which a definite reaction to tropism has been partially or entirely lost.” Parasitism is nothing extraordinary. Possibly it is not a factor which has newly appeared since plant cultivation was begun. It should be con- sidered as a nutritive form which arose gradually with the development of organic life and a necessary one, to be looked upon as the last link in the chain formed by the mutual interaction of organisms. This last link begins with those organisms which have the ability of forming organic substances from inorganic material through the action of light. Joined to these are the plants with the lesser need of light, such as are found among the bacteria living in humus where an addition of quickly decomposible organic sub- stances presents essential aid to the nutritive process. As the struggle for light gains in importance with an increasing number of organisms, the more pertinent becomes the development of groups of organisms requiring but little light and an ever greater need of a method of nutrition by which the raw material is offered in the form of organic, easily re-worked substances. Such conditions are found at present in saprophytism. With the struggle for light in the case of a constantly increasing num- ber of individuals comes also the struggle for space. In the course of time the lack of space will lead finally to those forms of adjustment in the plant world which require soil for their habitat only in the beginning, if at all, and have chosen some other organism as a centre of colonization. The mutual interrelations forming under such conditions are partly friendly, partly hos- tile, just as they occur in mutualistic and in antagonistic symbiosis. 1 Stahl in Bot. Z. 1884, pp. 163-66. 2 Pfeffer, Pflanzenphysiologie, 2 Edition. Vol. II, p. 763. Leipzig 1904. 17 Among the species of plants using some other organism as a habitat, we find the formation of very different devices for the means of nutrition. Be- ginning with lichens, the assistance given by thalli acquires greater and greater significance, up to the formation of a mycelium. The mycelium is satisfied with dead bark, or rather that attacked when dying, or with the leaf substance of its host, or it can only eke out its existence when, with the help of the enzyme which it excretes, it attacks the living organic substance and then calls parasitism into existence. But in all these relations the one fundamental law becomes evident that each organism is associated with the definite constitution of its substratum. This substratum must have the exact requirements for satisfying all the de- mands of the organism, otherwise it cannot thrive. Therefore all the organ- isms which we call parasites make very definite demands on some host. How narrowly limited these demands may often be is shown directly by the bac- teria, for which at times slight fluctuations in the amount of heat, the acidity of the nutritive mixture etc., lead to the replacing of certain species by others better adjusted. In order to cite only a few new examples we will mention the investiga- tions of Thomas Milburnt who cultivated fungi as well as _ bacteria. Of the former he found in the case of Hypocrea rufa that an increase of osmotic pressure first suppresses the formation of pigment in the conidia and finally inhibits the formation of conidia. In this fungus the color of the conidia changes with the reaction of the medium. If the reaction is acid, green spores are formed; if alkaline, yellow spores. A well nourished mycelium forms no fruit in the dark but does develop conidia when poorly nourished. The yellow color of the mycelium of Aspergillus niger is very sensitive to light and when exposed to it turns black within a few hours. The Bacillus ruber balticus found on potatoes, the so-called “Kieler bacillus’’? which, according to Laurent, forms acids on certain nutritive soils and al- kalis on others, is so influenced in its production of coloring matter by the nutritive substratum that it develops a violet color on an acid substratum and orange red on an alkaline substratum. Lepeschkin® observed that the strictly aerobic bacteria from the sputum in pneumonia, Bacillus Berestnewi, can develop a branching growth on strongly alkaline and on strongly acid substrata, but gradually acidifies the alkaline substratum. In the presence of sugar (dextrose) a pinkish color appears together with the disintegration of the little rods into oidia. In the presence of larger amounts of nitrogen compounds (aspargin, lecithin, peptone) the whole mass of bacteria turns yellow. The optimum for growth lies probably at 25°C. Even at 35°C. the bacterium grows very slowly and at 38°C. is no longer able to grow. It is killed at 55°C. 1 Thomas Milburn, Ueber Aenderungen der Farben bei Pilzen und Bakterien. ' Centralbl. f .Bakteriologie usw. II. Division 1904. Vol. XIII. Nos. 9-11. 2 See Breunig, Untersuchungen des Trinkwassers der Stadt Kiel, 1888. 3 Lepeschkin. Zur Kenntnis der Erblichkeit bei den einzelnen Organismen usw. Centrabl. f. Bakteriologie usw. II. Division, 1904, Vol. XII. Nos. 22-24. 18 If dependence on ‘the constitution of the nutritive substrata may be proved for parasites, naturally the strongest agent in combatting them is the removal of the favorable nutritive substratum and its alteration into one un- javorable for the special parasite. Since cultivated plants, by the fact of their division into susceptible and resistent varieties, demonstrate that there is a possibility of altering the nutri- tive substratum produced by living plants, the production of such resistent individuals through cultivation is the first aim of our work, in regard to overcoming parasitic diseases. It is more effective than the present method of fighting parasites locally or preventing their attacks, a method which was ceduced from a narrow point of view. At most this may be carried through effectively for small centres of disease but for mechanical reasons is im- practicable for general use. From this point of view parasitism is not such a great menace as it has been represented to be. If parasitism is a definite nutritive form of certain groups of organisms which has become necessary in the natural development of the living being, it must have its stage of equilibrium in the sphere of nature. Arrangements must exist which counterbaiance parasitism. It must be possible to hinder its effectiveness by factors simultaneously effective, for otherwise the nutri- tive organisms could no longer exist. This counterbalance is found in the very definite, often narrowly restricted environment which determines the existence of the parasite. That condition of a living creature which we are accustomed to term “healthy,” without being able as yet to define it, is one such restricting limit which the parasite under normal conditions is not able to overcome. For, since the defenders of the extreme theory have represented such parasitic micro-organisms as dangerous which are con- stantly present everywhere saprophytically and as yet have not killed the host plants as a whole, these plants must thus possess some protective devices in their normal development, which are repeated in the same sense from gene- ration to generation. We constantly find occurring as such, unbroken de- posits of wax and cork, definite acidity of the cell content etc. That we now find more and more adherents to our theory is proved by the statements of one of our most important students of parasitism, Met- schnikoff' of the Pasteur Institute. After giving a number of examples to show that the production of the parasitic disease is conditioned by two causes, first, the parasite and secondly, susceptibility of the organisms, he says, (page 7) “if these internal conditions are powerless to arrest the development of the excitor of a disease, the disease is produced. If, how- ever, the organism firmly resists the development of the bacteria, it is pro- tected and thus proves itself immune.” (Page 6) “One can no longer be of the opinion that, every time an excitor of disease penetrates a susceptible organism, the presence of the same inevitably calls forth this specific dis- eased condition. Loffler’s discovery of the diphtheria Bacillus in the pharynx " aitiaunitat bei Infektionskrankheiten by Elias Metschnikoff, Professor of the Pasteur Institute in Paris. Authorized Translation by Dr. Julius Meyer. Jena, Gustav Fischer, 1902. ! 19 of healthy children has been repeatedly substantiated since that time and yet it is impossible to doubt the etiological significance of this bacillus for diph- theria. On the other hand it has been proved that Koch’s Vibrio, although ~ the real incitor of Asiatic cholera, nevertheless, occurs in the digestive system of healthy people.” The healthy organism thus possesses a natural immunity and any distur- bance of this aids the possible parasitic attack. 5. EPIDEMICS. If we can define endemics as a local malady, whose production is con- nected with definite conditions, narrowly limited locally, then epidemic may be called a community malady. The expression “malady” indicates the mul- tiplicity of the diseased individuals in contrast to isolated cases of disease. Epidemic thus describes that condition in which numerous individuals suc- cumb to a given form of disease, developing over large territories. If an epidemic breaks out, conditions must be present which disturb the functions of the organism in numerous individuals so strongly that their lives are either threatened with a premature end or are finally brought to this end. This disturbance arises from external causes. If these causes are parasitic organisms, their existence, as was shown in the preceding chapter, is dependent on the factors of growth favorable to their extensive increase. Among these factors belongs the breaking down of the immunity of the nutritive organism. Even with the assumption that a parasite not indigenous to the countries which suffer from the disease might have caused the epidemic by its incur- sion, this circumstance in no way changes the fact that the factors of growth already existing are determinative for the production of the epidenic. For, whatever may wander into the country, be it animal, fungus or bacterium, this incursion would not produce an epidemic, if the newcomer found no opportunity for great increase and wide distribution. For example, who does not remember very effective representations of thc importation of the Colorado beetle as the destroyer of our potato crop, or the extensive intro- duction of the San José scale.as the destroyer of our fruit trees? Initiated persons know how often embargo regulations and compulsory disinfection have advanced protection against the importation of parasitic fungi (“White Rot of the Grape” etc.) and they have partially succeeded in getting it. Experience has taught that no theoretically imagined but practically im- possible complete destruction or quarantine of such parasites has possibly protected us from epidemics but the circumstance that they did not find the necessary climate and soil for their increase. Conversely, the Phylloxera plague should be remembered which, despite all human endeavor and the spending of many millions, became more and more widespread. The Phylloxera finds, even in Europe, sufficiently favorable conditions for exis- tence and on this account defies such means for fighting it as embargo, dis- infection, processes of extermination etc. Upon consideration, it becomes 20 gradually clearer that small living creatures, in fact, the smallest which are introduced by means of articles of commerce or can be casily distributed by dust and wind, may be kept cut of small enclosed places but not away from extensive open localities, and that one proceeds better by presupposing the possibilities of a widespread distribution of such organisms although real danger is to be recognized only if an easy capacity for its increase has been proved. If now in all parasitic incursions, not the presence of the parasite but the conditions favoring its spread are proved decisive for the production of the epidemic, then a change in these conditions is the best means for com- batting them. In regard to measures for its suppression and prevention, however, the epidemic furnishes special pointers in that, when it occurs over extensive areas, it excludes as causes all the factors which vary from one another in the different diseased districts. For, since the malady attacks large plan- tations despite the variations in such factors as, for instance, situation, com- position of the soil, agricultural methods etc., these factors cannot be the cause. Rather the cause should be sought in those influences which are the same throughout the whole country. Actually, this can only be the climate. On the other hand, in endemic diseases, conditions of the soil usually act de- cisively. They are to be considered either direct causes of disease since, through unfavorable chemical or physical peculiarities they permanently dis- turb the functions of the plants, or they act indirectly, favoring the increase of the parasites and the strength of their attacks. In this, as a rule, they suppress at the same time the growth energy of the host plant. Soil damp- ness is the condition most favoring this. When the capacity of thick, heavy soils for retaining water is very great on the level or in holiows, an accumu- lation usually occurs which finds no outlet and produces a deficiency of oxy- gen, with an excess of carbon dioxid. The plants indicate this ftinctional disturbance by a change in the chlorophyll apparatus. The leaves, gradually turning yellow, form a suitable growing medium for certain groups of fung!. In all endemics and epidemics a simultaneous sickening of a great num- ber of individuals indicates a considerable period of preparation leading up to the actual outbreak of the malady. For, according to our conception of all the phenomena of life as dynamic processes, each case of disease may be characterized as the immediate or in- direct result of mechanical disturbances exercised by the separate factors of growth on the composition and function of the substance. The life of a cell is a constant struggle between the oscillatory forms momentarily present in the unstable organic compounds and the disturbances constantly exercised upon them by the factors of growth. A change in the substance and with it one in its function appear at once if the disturbance in one factor of growth is so strong that it is able to change the form of oscillation existing up to that time. So long as the dis- turbances as a whole have the effect of contributing to the development of the organism as a whole, that is, the vegetable individual, the plant remains 21 within the latitude of health. Disease follows if the cell or the cell complex is so changed that ultimately the whole structure suffers. Now, however, the fact, always confirmable by examples, that certain cultivated varieties show a tendency to disease not shown by others under similar conditions of growth, furnishes us proof that in the different individ- uals the organic substance may oppose a differing amount of resistance to the same attacks. This would mean that more attacks are necessary for one individual than for another in order to carry it out of the latitude of health. If, in an epidemic, only large numbers of individuals always suddenly become sick, besides the especially susceptible ones there must also be others among them for which a greater number of attacks and therefore a longer period of action is necessary, in order that they may become sick. Therefore a longer period of the influences producing the disease must have led up to the outbreak of the epidemic and these influences are to be seen in the atmos- pheric factors. Therefore, according to our theory, each epidemic is, so to speak, the explosion of a charge which had been slowly accumulating for some time. Its cause therefore is not to be sought, at least exclusively, in the existing factors of growth present at the moment but in the acct:muiation of attacks which for some time previously have been effective in the same way. In parasitic epidemics the extensive occurrence of the micro-organism in no way represents the first stage of the phenomenon but ts a final effect of long preparation. This preparation consists on the one hand in.the gradual pro- duction of life conditions favorable for the enormous increase of the micro- organisms, on the other hand, in the gradual weakening of some functions of the host which we believe are always connected with this and a correlative increase of other functions. If, for example, we study the best known fungous epidemic, potato blight, observation shows that a period of warm, dull, sultry days usually: precedes the outbreak. The fungus Phytophthora infesians is always present. Its astonishingly rapid increase, however, takes place out of doors only if abundant atmospheric precipitation and a warm motionless air con- tinuously favor the production and the scattering of the swarm spores. Dur- ing weather of this kind the potato plant develops a greater amount of sugar, a more rapid stem growth and a great number of young leaves; that is, it produces an especially susceptible environment for the development of the fungus which scorns organs that have become old. In this way we find that whole fields may become diseased in a few days. On the other hand we do not find the Pytophthora epidemic if the same amount of precipitation occurs in the same space of time but in cold weather. The epidemic cannot develop if, with increased warmth and a clouded sky, persistent strong winds keep blowing. A similar relation is shown in rust epidemics of grains. Like the majority of fungi the grain rusts love con- tinuous moisture. Yet by no means do we always have rust epidemics in wet _ years, although there might be scarcely one grain field in which the rusts 22 would not be present every year. The epidemic develops at the time when the leaves are young and only during periods of warm days with frequent even if almost unappreciable showers which make possible a longer retention of moisture among the plants. Cold, wet summers generally prevent the development of rust epidemics. Similar conditions may be observed in bacterial epidemics. Therefore, epidemics are forms of disease which mature only because of far reaching factors. Only certain weather combinations of longer duration may be considered as the initial cause. Naturally the intensity of the epi- demic will vary locally because local factors will produce special favorable conditions. In this way is explained the occurrence of centres in which the malady appears first and disappears last, in case not all the individuals are killed in a short time. In this way is explained further the retrogression of epidemics into endemics; that is, into narrowly confined centres of disease. Among the epidemics produced by animal parasites, those caused by grain flies are the most abundant with us. They usually take place during periods of continued warm, dry weather after the winter conditions have been favor-: able for the individual grain flies which in some regions are always present. So far as statistics now go, preferred centres and points of departure may often be determined for this plague-like distribution. Thus, for example, the province Posen is proved to be especially favorable soil for grain flies. From Posen as a centre an epidemic usually radiates towards Brandenburg, Pomerania and: West Prussia. The whole Eastern part of Germany suffers more from injuries due to flies than does the Western part. North Western Europe is usually visited more frequently and intensely than South Western and South Eastern Europe. According to the point of view here developed any treatment of the epidemics by fighting the symptoms as they appear must offer the least pros- pect of success, because these are only the result of initial stages which existed long before. If the parasites are present in enormous quantities the desire to kill the micro-organisms is seen to be a vain one since no insecticide or fungicide can even approximately reach the main mass and still less cause its death. Thus as the pestilences are induced by general factors acting uni- versally, they must be combatted by broad means which undo the life con- ditions of the parasite and change the constitution of the host, that is, the functional direction. If, for example, long wet periods permit the bacterial rot of potato, which we call “wet rot,’ to appear in epidemic proportions, any other means than increased ventilation of the soil can scarcely be used successfully. So far as specific anaerobic bacteria are concerned, the factor favorable to growth (lack of oxygen with excess of carbon dioxid) is re- moved by an increase of oxygen and also by the decrease for them, as well as for other bacteria, of the condition fundamental to their abundant in- crease, an abundance of water. Nature generally works in this way. If, after the rainy periods, dry, windy weather continues for some time so that the soil dries and the air circulates freely, the progress of the disease comes 28) naturally to a standstill. The recommendation of every regulation for the prevention of infection by the removal of infected potatoes from the field, or by deep subsoil cultivation, or the burning of diseased straw in grain epi- demics, we consider to be a work with insignificant results as contrasted with the effect of changed life conditions for the parasite. The amount of in- fected material in extensive districts does not come under consideration at all. At times in the case of damp rot, soil bacteria co-operate and form a dense condition of the soil. If atmospheric influences make themselves so felt in certain soils that certain bacterial groups are able to attack potatoes or other fruits of the field, the number of the causative agents of the disease originally present is almost of no significance. The last named examples of parasitic epidemics due to such micro- organisms as may be assumed to be constantly present in the soil or the air, make clear to us, however, how little prospect of success is offered for com- batting an epidemic once it has broken out. A greater protection for our cultivated plants lies in preventive methods. Such a preventive process in epidemics, aside from the formation of an universal plant hygiene, can, how- ever, be induced by the drawing up of a chart of pestilences; that is, a sum- mary of plague centres for each individual epidemic. In the correspondence ef certain characteristics for a number of plague centres, single factors are especially distinguished as fundamental for the production of an epidemic ; for example, dryness in light soils is shown to be favorable for fly epi- demics of grain or for the heart-rot of sugar beets etc. Having thus deter- mined weather and soil combinations dangerous for each individual epidemic one can make one’s attack prophylactically by means of cultural regulations as soon as the threatening combination of conditions continues for some time. Direct means which kill the parasites, such as sprinkling with copper sulfate or dusting with sulfur, will then act only as hinderances to the epidemics if used preventively. 6. ARTIFICIAL IMMUNIZATION AND INTERNAL THERAPY. It is quite natural that in phytopathology the same course of ideas has developed as in animal pathology and accordingly it is not strange that there has gradually become evident a theory of immunizing plants artificially; 1. e., of so changing their bodily composition that the parasites will no longer find the nutritive soil necessary for colonization, for their wider distribution. There already exist several works along this line in which, following in part serum therapy, use is made of immunifying substances obtained from the parasite itself, and again where mineral salts are used. Along the former line belong Beauverie’s' investigations with Botrytis cinerea and those of Ray? with very different kinds of parasites. The latter obtained 1 Beauverie, J., Essai d’immunisation des végetaux contre les maladies crypto- gamiques. Compt. rend. Paris 1901. II, p. 107. 2 Ray, J., Cultures et formes attenuées des maladies cryptogamiques. Compt. rend. Paris 1901. II, p. 307. 24 the result that parasitic organisms may be influenced in artificial cultures by the nutritive medium used. In this their virulence is proved always to be less than it is under natural conditions. By leeching the cultures, fluids may be obtained which may be used for the immunization of the host plants against the organism concerned. The author concludes further that the in- fected plants are actually cultures of the parasites concerned. In this maceration and extraction of the diseased plant parts must furnish fluids which would exercise an effect similar to that of the parasite itself. When modified by increased temperature, these fluids can be used for immunization. E. Marchalt should be especially mentioned as a_ representative of the other line of immunization experiments. He worked with mineral substances, some of which were nutritive, while others should be considered poisonous. He sowed lettuce in Sachs’ nutrient solution with the addition of substances which kill fungi. The young seedlings, after the development of the first two or three leaves, were infected with the zoo-conidia of Bremuia Lactucae and then kept in a moist atmosphere. The plants, not rendered immune by the substances in the nutrient solution which would kill fungi, were at once attacked. Of the salts used, the addition of from three to four ten-thousandths copper sulfate to the nutrient solution was clearly proved to increase the resistance. The addition of 1-10000 copper sulfate no longer showed any immunizing effect whatever. Manganese sulfate acted less com- pletely ; ferrous sulfate had no effect at all. Calcium salts also (up to 2-100) could increase the resistance while nitrates and also, curiously enough, phos- phates lessened it. The idea of increasing each individual’s susceptibility to vegetable para- sites by changing the cell sap through the addition of foreign substances was also taken up by zoologists who proceded in accordance with the discovery that parasitic animals, for instance, scale, seek out weakened plants especially. Now, however, was associated with this the thought that universal con- ditions of weakness in cases of constitutional disease as well as conditions of susceptibility to parasitic attack could be healed by supplying salts of some definite kind to the plant body extra-radically. This taking up of substances otherwise than through the roots was called “Jnternal Therapy” and was developed methodically. In 1894, I. Schewyriov? published an article on “the impregna- tion of the wood in living trees with solutions of coloring matter” (Ueber die Durchtrankung des Holzes lebender Baume mit Farbstofflosungen”). In it he describes the apparatus which he constructed for this purpose which we will call nutrition tube and nutrition basin. The tube is of steel, pointed at one end, which is driven into the bark, while the other end is closed by a cork, through which passes a gimlet. The tube is filled with the experimental liquid, through special openings, by means of a rubber tube. Then the gimlet 1 Marchal, E. De Vimmunisation de la laitue contre le meunier. Compt. rend. 1902. CXXXYV, p. 1067. * Schewyrjov Iwan, Berichtigung usw. Zeitschrift fiir Pflanzenkrankheiten. 1904. p. 70. 25 is bored slowly down into the wood to the desired depth so that the liquid but no air can penetrate into the canal thus formed by the gimlet. The author who had constructed other apparatus also mentioned Hartig’s ex- periments which had the disadvantage of letting air penetrate into the wound. He then began experiments on the healing of chlorosis which were carried out in 1895-6 and in 1901, by garden owners in the Crimea. Later Mokrzecki' published a number of successful experiments on the healing of chlorosis in fruit trees carried out according to the above method, in which he also pointed out that the scale had disappeared from the healed branches. He, as well as Schewyrjov, built great hope on this pro- cess, not only for the prevention of constitutional disturbances in nutrition but also especially for the expulsion of parasitic organisms. My personal attitude toward this question is much cooler and I think that the effectiveness of the methods will be very limited. According to my experiments on the introduction of poisonous solutions into the trunk, the effect usually remains local but in the most successful cases radiates grad- ually from the point of introduction to a number of branches and to a con- siderable distance into the trunk. The constitution of the plant, conditioned by root nutrition, was not changed by this. I found in my experiments with oxalic acid that gum was produced on a number of cherry tree branches which later partially died. However, the production of gum did not progress further the following year and the trees, moreover, made a healthy growth. Like this poisonous solution, each nutritive mixture or healing serum remains limited within narrow boundaries and, as in the most favorable case, only temporarily exercises any beneficial influence. The physiological direction of the work of the whole plant will not be changed permanently. ~. PREDISPOSITION. We term “predisposition” that condition of certain individuals which renders them more easily and quickly susceptible to any cause of disease than are other individuals of the same kind. That such cases exist is proved by daily discoveries as to the quantitative growth of cultivated plants. These discoveries have already found expression in the common use of the terms tender and hardy varieties and individuals which have been made less resistant. Observations show that not only differ- ent cultural varieties of the same species but even single individuals of the same variety possess a varying power of resistance to weather extremes, as, for example, cold and heat, or to parasitic attack. In the latter connection, it suffices to mention that practical workers as well as scientific investigators have now set themselves the task of breeding more resistant varieties. At present we are only in a position to indicate the direction in which a greater individual inclination to succumb to any parasitic attack may be pro- 1 Mokrzecki, S. A. Ueber die innere Therapie der Pflanzen. Zeitschr. f. Pflan- zenkrankheiten. 1903. p. 257. 260 duced. In the previous divisions we have considered investigations showing that different groups of substances produced in the plant cells, as, for in- stance, sugar, act attractively for certain fungi in definite concentrations and repellantly in others. The number of these groups of substances is deter- ~ mined by very different factors, as will be shown more thoroughly 1n the next chapter. This metabolism will be found favorable for the nutrition of the parasite or unsuitable for it, according to the quantity produced. In order to cite at least one example in this connection, we will refer to the investigation of Viala and Pacottt on the black rot of the grape. The cultures, undertaken with the fungus Guignardia Bidwell which pro- duces the disease, determined that the development of the fungus is depen- dent primarily on the sugar content of the nutrient substratum and its organic salts. Only young leaves were affected. They contained 1.75 per cent. tar- taric acid and 4.3 per cent. glucose, while the old leaves showed only traces of these substances. The berries were susceptible from the time they began to swell and this susceptibility continued up to the beginning of the ripening stage. During this time they contained 32 to 24 per cent. of acid and 11 to 56 per cent. of sugar. During ripening the acid content falls from 9 to 2 per cent., but the sugar content increases so greatly that the fungus can no longer attack the berries. The conditions for the white rot fungus, however, are exactly reversed. By this relation is explained the strikingly different resis- tant capacity of different kinds of grapes. In the same way is explained the circumstance that black rot epidemics generally occur in summer after periods of cold weather with subsequent light rainfall. At this time the acid content is especially large and the formation of sugar scanty. Similar fluct- uations in the concentration of the cell sap combined with the phenomena of perforation of the membrane, the varying processes of tension in the tissues and other mechanical changes also in the plants cause a state of greater sus- ceptibility to weather extremes. The more recent investigation is endeavor- ing to find more macroscopic and microscopic characteristics also demarking the stages of susceptibility to injurious parasitic attacks. The conditions pictured in the preceding example of the increased tend- ency of the grape to become susceptible to the black rot fungi are entirely normal developmental phases which are influenced by the weather. On this account we may speak of such states as normal predisposition. In contrast with these we should distinguish as abnormal predisposition the case in which the plant or one of its organs has fallen into a condition of weakness or of disease from other influences and in this conception of one cause of disease is first given the desired point of attack. As an example, we will call attention to the infection of leaves affected with honey dew by the black fungi, to the attacks of the so-called parasites of weakness and the migration of wood- destroying fungi from wounded surfaces. 1 Viala, P., et Pacottet, Sur la culture du black rot. Compt. rend. Paris 1904. Voll CXECCVLIE ps 30G: 27 8. PREDISPOSITION AND IMMUNITY. In an earlier part we have pointed out that our theory as to the produc- tion of parasitic diseases has obtained support from the most renowned in- vestigators. Metschnikoff!, who, as professor in the Pasteur Institute for infectious diseases, may be incontestibly considered as an exact con- noisseur of pathogenic micro-organisms, expresses himself as follows, “Exact bacterialogical investigations have led to the knowledge that, in the abundant bacterial flora harbored by the healthy human body, representa- tives of pathogenic bacterial species may also be found. Aside from the Bacillus of diphtheria and the Vibrio of cholera which so often have been proved to be fully virulent in perfectly healthy human beings, it has been shown that certain pathogenic micro-organisms, the Pneumococci, the Sta- phylococci, Streptococci and Colibacilli, are present regularly or almost con- stantly in the microbe flora of healthy persons. This discovery has of necessity led to the conclusion that besides the excitor of the disease, still a second cause of infectious diseases must exist, namely, a predisposition or a lack of immunity. An individual which harbors one of the species of pathogenic bacteria above-named would be resistant either permanently or for the time being. But as soon as this immunity dis- appears, the excitor of the disease becomes uppermost and produces the specific disease.” In regard to the immunity of plants, Metschnikoff calls attention to the investigations of de Bary? on Botrytis, which we have already men- tioned. The mycelium of this fungus penetrates the ceil walls by giving off a fluid “which contains a digestive ferment and the oxalic acid necessary for this ferment. De Bary could prove the presence of this kind of toxin by the maceration of the mycelium of Sclerotinia. . . . Hi the resulting fluid is heated to 52°C. it can no longer digest the cellulose membrane but is still able to cause plasmolysis . . . . The results of de Bary’s investigations have been confirmed and in part completed by Laurent.”* We have repeated Metschnikoff’s words in order to characterize his way of considering the matter. The chief factor under consideration here, viz., the effectiveness of the ferment on young membranes and its ineffective- ness on older ones, gives the author reason for comparing the Botrytis dis- eases with the infantile diseases in human beings (measles, scarlet fever). In other cases the different processes of cork production, or suberization, found, for example, in wounds, act in a way similar to the membrane changes in the ageing of the cells. In regard to these, Metschnikoff, supported by the investigations of Massart*, points out that the organs respond differ- ently to the traumatic stimulus according to their age. Young leaves of Clivia, for example, re-act by forming callus, older ones simply close the Metschnikoff, Immunita&t bei Infectionskrankheiten. Jena, 1902, p. 6. De Bary Bot. Zeit. 1866. Laurent, Annal, de l’Institut Pasteur. Vol. XIII, p. 44. Massart, La Cicatrisation chez les plantes. Briissel 1897. Rowe 28 wound by means of a deposition of cork. Further protective means are oils, resin, balsams, milky juices and gums exuding from injuries. Metschnikoff thoroughly treats of Laurent’st studies which are mentioned in connection with other bacteria in the second volume of this, work. At this point, however. we will emphasize especially the immunity precautions against bacterial attacks. The species of the Colibacillus, with which Laurent worked, secretes a ferment dissolving the cellulose of the potato tuber and produces also sap with alkaline reaction, the presence of which is necessary for the process of assimilation on the part of the bacteria. Now, to be sure, Bacillus Coli communis is naturally not a plant parasite but it can be changed into one. ‘This happens when it is first cultivated on po- tatoes whose resistance has been weakened by having been dipped into alka- line solutions As a result of such cultivation the bacillus can act as a plant parasite when carried over to the same species of potato. The struggle be- tween the Colibacillus and the potato depends therefore really on the chemi- cal action of the alkaline secretion of the bacillus on the acid cell sap of the potato. After fertilization with potassium salts and phosphates, carrots and potatoes resist the bacillus. On the other hand, a phosphate fertilization showed in (Topinambur) that this plant then became more susceptible to the Botrytis form of Sclerotinia Libertimia. Just as clearly by strong nitrogen fertilization potatoes are made less re- sistant to wet rot. According to our observations abundant fertilizing with nitrates, ammonia salts or stable manure, causes even the most resistant | species to succumb to the potato rot. Laurent explains the difference in the action of parasites under the same method of fertilizing by the fact that with bacteria the secreted ferment can attack the cell membrane only in alkaline juices or weakly acid ones. An increased acidity of the cell sap, incited by the formation of acid salts resulting from phosphate fertilization, renders the plants immune to this fission fungus. I obtained the same results for phosphoric acid by fertilization experiments on sugar beets, in which the Bacillus betae was widely disseminated and had produced the bacterial for- mation of gum or tail rot. The rapid increase of bacteriosis with the abun- dant use of fertilizers which contain nitrogen might be explained in this way :—that the acid of the cell sap is thereby decreased. According to de Bary, the conditions for Sclerotinia are exactly reversed. Their ferment dissolves the cell wall only in an acid fluid. Most mycelial fungi act similarly. If, by a change of constitution of the cell sap, sometimes a factor of im- munity presents itself and, at other times, a condition predisposing to para- sitic disease, we are referred by Metschnikoff (1. c. p. 39) to a further pro- cess. He cites the investigations of van Rysselberghe? who found, especially in the epidermal cells of Tradescantia that if these cells were 1 Laurent, Recherches experimentales sur les maladies des plantes. Annal. de l’Inst. Pasteur. Cit. Zeitscher. f. Pflanzenkr. 1900, p. 29. 2 Osmotische Reaktion der Pflanzenzellen. Mémoires couronnés de Academie r. d. Belgique. Briissel 1899. 29 brought into a more concentrated solution than was normal to them, they showed an increase of intra-cellular pressure. I¥ the experiment was re- versed, the pressure decreased. These changes in osmotic pressure are caused by the difference in concentration of the cell sap which may again be considered as a result of chemical changes. If the cell comes in contact with a solution too highly concentrated, it forms oxalic acid which acts strongly csmotically. With Tradescantia, van Rysselberghe proved the presence of malic acid in the normal sap and only in rare cases any traces of oxalic acid. After the plant had been kept some days in strongly concentrated cane sugar solution, oxalic acid was found in clearly appreciable amounts. The plant gradually adjusts itself to the higher concentration of this medium, produc- ing oxalic acid in order to increase the pressure of the celi sap. The acid is supposed to be formed at the expense of grape sugar. The increased acid ‘content will act as a protective means against bacterial attacks. It is also suggested by some investigators as a protective weapon against the attacks of snails and leaf lice. Experiments with Tradescantia made in the opposite direction seem to me to be very significant. If tissues from this plant were taken from the highly concentrated solution and put into some strongly diluted solution, precipitates of calcium oxid crystals were observed in the cell sap, thereby initiating a decrease of osmotic pressure. When the plant was put back into a stronger solution the oxalic crystals were seen to re-dissolve and result in a new formation of acid. I found that part of the calcium oxalate crystals disappeared during the sprouting of potato tubers which also may well be ascribed to the increased formation of acid. Pfeffer' also takes up this automatic regulation of the acid con- tent since he calls attention to the frequent production of turgidity through the organic acids combined with bases. Since this remains constant during and after growth, the formation of acid must be hastened quantitatively in correspondence with the volume increase of the cell and the dilution of the cell sap thereby produced. Each unusual increase of turgor, as, for example in the effort to overcome an opposing higher concentration, will be connected with a corresponding increase in the acid production. Conversely, for exam- ple in the Crassulaceae, the decrease of the acid content has been proved with an increase in temperature and by illumination. In this same sense the experiments made by Charabot and Hébert? have succeeded. In the shade, the quantity of combined organic acid increases very considerably. The free volatile acids also increase. These are found in greater amounts in etiolated plants than in others. The suppression of the inflorescences in- creases in the leaves at the expense of the other organs. In considering predisposition and immunity, we have brought forward the sugar content in addition to the examples of acid content. To what 1 Pflanzenphysiologie, II Edition, Vol. I, p. 487. 2 Charabot, Eug., et Hébert, Recherches sur |’ acidité végétale. Compt. rend. hebd. 1904. CXXXVIII, 1714. 30 fluctuation this is exposed by changes in temperature is best seen in Fischer’s! investigations cited by Pfeffer?. In the so-called starch trees, like the linden and birch, it is found that starch is formed in the bark within a few hours after the branches have been brought into a warm room from a winter temperature. In the cold, sugar is again produced from this starch. This conversion may be repeatedly produced and this kind of sugar forma- tion seems to appear in many plants with a lowering of the temper- ature. If now, for any reason whatever, the sugar formed from the starch is conducted away from the organ the whole tissue may be im- poverished. Pfeffer furnishes proof of this by the experiments carried out in his institution by Hansteen* and Puriewitsch*. By a con- tinued removal of the sugar by diosmosis, it was possible to cause an ejection of starch from the isolated endosperm of grasses as well as the cotyledons of Phaseolus which had been cut off from the plant and a giving off of the glucose from the separate scales of the bulbs of Alliwm Ccepa. If only a little water was present into which the sugar could pass from the organs the ejection came to a standstill because a two to three per cent. sugar solution inhibits the conversion of the starch. Therefore, either a good deal of water must be present or some other means for the removal of the starch if the ejection should be completed. Conversely, a refilling of the organs with starch could be determined if a still more concentrated solution were used. These examples may suffice to show how in the plant body all the me- tabolic processes and all the resulting constructive processes succumb under constant quantitative changes which radiate in ail directions from the first form of attack of the factor causing the change. Each change occurring locally is a disturbance in the condition of equilibrium existing up to that time in the molecular organization. If the disturbance is completed in one cell it must, so far as diffusible substances are concerned, he continued in the neighboring ones as are all dynamic processes. Each place in which a new structure is formed becomes a centre of consumption. The supply of food to this new structure leads to a reduction in other parts. Each local increase in photosynthesis exerts its influence on the immediate surroundings not concerned in this process. The different factors of growth now act uninterruptedly on the plant body and disturb the momentary equilibrium, first in this direction, then in that. We have there- fore a continued fluctuation in all life processes which is increased still more by the capacity for reaction peculiar to the individual, for we dare not forget that in restoring the disturbed equilibrium the organism must endeavor to increase its production of different substances. If, for example, there sets in an increase of the basic compounds conditioned by nutrition, an increased acid content will have to be brought about and conversely. And within the constant fluctuations which are a necessary result lies the condition which 1 Fischer, A., Jahrb. f. wiss. Bot. 1891. Vol. 22. Physiology I, p. 514. Hansteen, Flora, 1894. Supplement. Puriewitsch, Ber. d. Deutsch. bot. Ges. 1896. p. 207. em © bo au we term normal predisposition. Thus the same condition which represents a state of predisposition toward a definite cause of disease can act as a state of immunity to some other cause of disease. Proofs of this are offered by the examples above cited of the hyperacidity of the cell sap which has been shown to give immunity to certain bacterial attacks and predisposition to those of fungi. In the increased sugar content, which is connected with the influence of the acid in increasing the turgidity, we recognize a condition predisposing to injuries arising from frost and, on the other hand, a pre- cautionary means against the disturbing action of drought. In the very natural development of the organism, therefore, we con- stantly face conditions of predisposition and immunity. These are present in varying degrees in each individual since each organism has special nutritive relations and utilizes differently the same factors of growth. This explains the phenomenon that different individuals in the midst of a community of the same species become sick or conversely, in the midst of a centre of disease, remain healthy’. Q. INHERITANCE OF DISEASES AND OF PREDISPOSITION. In the last four decades further experiments have been made by many important investigators to explain theoretically the nature of heredity. In this, special consideration was given to the most juvenile condition—the embryonic plasma—as a transmitter of the capacity for inheritance and the substance which might be indicated as the chief transmitter of inheritance was sought in part in the cell nucleus. The above-mentioned hypotheses of biologists were drawn up to explain especially the repetition of the formative processes in the successive genera- tions of the organism. We will call attention only to Darwin’s “gemmules,” Haeckel’s “plastidules,’’ Weismann’s “germ plasm” as an “heredity plasm,” Nageli’s “idio-plasm,” de Vries’ “pangene,” etc. 1 The parasitic theory as generally accepted at present either still needs an explanation of these facts or is restricted to the theory of resistance. The different capacity for resistance to atmospheric extremes and other non-parasitic influences has remained unconsidered. Thus Alfred Fischer* observes “Individual variations indeed occur often enough even in man; a personal immunity of an inexplicable kind seems to exist which in part falls under the conception of predis- position. Even with age natural immunity varies as shown by infantile diseases. The question may be left undiscussed as to whether even these may not be con- sidered as immunizing diseases which are said to prepare the youthful mortal for an existence surrounded by bacteria and to fortify him.” On the other hand, Alfred Wolft** explains ‘In all essentials the natural power of resistance to toxins advances in proportion to the organ’s capacity to hold the molecules of the poison and to prevent their action on the brain. Thus only quali- tative and no quantitative differences exist between apparently so diametrically opposed phenomena of an innate non-susceptibility and a high grade of susceptibil- ity in individual animal bodies. These differences lie only in the different capacity of the organs in different animal species for the formation of toxin and an eventual neutralization.” ieee A., Vorlesungen tiber Bakterien. 2. Ed. p. 347, Jena, Gustav Fischer, ** Alfred Wolff, Ueber Grundgesetze der Immunitit, Centralbl. f. Bakteriologie, Parasitenkunde usw. Sec. I. Original. Vol. XXXVII. Part 3, p. 701, 1904. ed According to our theory there is needed for the explanation of the pro- cesses of inheritance, neither any special locality such as the embryonic cells, nor any special cell or plasm germ or inheritance mass or any ancestral plasm, for inheritance is a “mechanical must” a necessary universally present me- chanical result of the structure of the organic substance. As soon as the organic substance, like the inorganic, is considered as an atomic union which retains its character and therefore its specific peculiarities, since the atoms in the molecules exist in definite arrangements and fluctuation, then this sub- stance presents the stage of equilibrium of definite forms of motion. If one cannot define the countless combinations of molecular fluctuations and can- not construct the distention and other mechanical results arising from the different arrangement, one may yet characterize each organic structure as the result of a sum of very definite combinations of molecular motions which are conditioned by each other. Accordingly the cytoplasm of the pear is a plasma whose different micellae show in general the molecular fluctuation forms of the plasmatic substances but still possess specific relations of fluct- uation and arrangement which distinguish them from similarly located micellae of the apple cytoplasm. Therefore, im each smallest particle in each biogen of any organic individual whatever, an individual character may be found which must remain constant as an expression of the sum of definite forms of motion resulting from the law of inertia. This constancy is a mechanical necessity ;—for every motion continues in its existing form as long as it is not modified by another demonstration of force and each substance which is the expression and bearer of the motion retains this form and character until other reactions cause molecular changes’. If, for example, we speak of protoplasm, we must be conscious that we do not designate thereby a homogeneous substance with a fixed chemical nature, but a large group of substances containing many forms. The same is true for cellulose, sugar, tannic acid etc. The assumption of the existence of as many variations of substances as there are individuals loses its strangeness as soon as we remember that we see about us daily an equal number of variations of figures,—for, as a fact, no one individual resembles another absolutely. If, however, each biogen is 2 specific unit, it retains its character with the provision that no substance coming from without may change its molecular grouping, no matter where it is located in the plant body, nor whether it occurs in the form of cellulose or as somatic or embryonic tissue. For all these substances are indeed only groupings proceeding from one another. The biogens which are utilized in the formation of the embryo, that is, at the beginning of the new generation, find an expression in the new individual as in the old for the form of fluctu- ation which they represent. This retention of the molecular form of motion 1 This view of the specificity of each biogen in every organism has already been expressed by Noll, since he states that the egg cell of a linden in its totality is already a linden and cannot be anything else nor become anything else. Noll, Beobachtungen und Betrachtungen iiber embryonale Substanz. Sond. “Biolog. Centralblatt.” Vol. XXIII, Leipzig 1903, p. 325. 33 in 'the new generation is heredity. We are not in the least astonished to find carrot substance reproduced from carrot seed. We are also not astonished to find a table carrot produced from a carrot which 1s rich in sugar and not a cattle carrot rich in starch. Thus the same combinations of substances are transmitted which represent the characteristic peculiarities of our cultural varieties. If in practical agriculture we should plant side by side both of the above-named varieties of carrots we would have opportunity to observe that with the appearance of a certain degree of frost, the table carrots would freeze while the cattle carrots would remain uninjured. The susceptibility to cold of the substance of different varieties of the same species is the most easily observed example of the inheritance of such peculiarities as represent predisposition to disease. Each fruit grower can name varieties of fruit which are injured by frost in his orchards while other varieties standing nearby are not affected or injured. The same rela- tions are found among flowers and with grain it is a universal experience that, among the different varieties of wheat, for example, the square-heads winter-kill most easily. The same variation in the resistance of differ- ent cultural varieties is found also in relation to other causes of disease, as, for example, overheating and drought, excess of water etc. A great deal remains to be learned of the cultural varieties and their study deserves greater attention than has been given to it up to the present. Thus cultivation has furnished us with an ornamental plant, coxcomb (Celosia cristata), which has a stem with a broad, much curled vegetative tip. This broad, band-like transformation of the original cylindrical stem (fasciation) has become constant in the seed. Double blossoms are retained from one generation to another. Weak or one-sided formation of the sex- ual organs can become an hereditary peculiarity, as, for example, in the black currant or in the strawberry culture in Alten Lande near Hamburg. From such examples one sees what far reaching differences from the sual mode of development are transmissible through the seed. Each vari- ation indicates a direct thrust against a previously existing peculiarity which is so strong that it is able to shatter this peculiarity permanently. The peculiarities of the organism possess a varying degree of stability, 1. e. the form of motion which they represent is often disturbed by a weak thrust, while in other cases it can not be changed by the strongest attacks of the surrounding factors of growth. Among the least fixed peculiarities belong the colors of the blossoms, the water and sugar content and the size pro- portions of the organs which can vary even in the natural habitat. Hardest to alter or cause to vary are the relative positions of the organs and the com- position of the biogens, viz., the type of substance forming cabbage head or of a pear tree as such, and distinguishable from that ef other plants. No peculiarity of an organism may be considered as indestructible but a num- ber of peculiarities will be retained from generation te generation in their present form because no thrust has existed up to that time of sufficient strength to shake them. These peculiarities, however, which are ac- 34 cessible for factors existing at the time may succumb to the thrust according to the strength of the attack and thus be changed. These changes, because indicative of molecular transpositions, are constant as forms of fluctuation, due to the law of inertia until new thrusts give a new direction to the motion. They are retained also in the organs which we call seeds and must accord- ingly be continued in the new individual and therefore must be hereditary. At times also, conditions contrary to the purpose of the individual, and which therefore initiate the shortening of the life period of the individual, such as a lesser firmness of the substance, will be hereditary. In this sense we will have to reckon with an inheritance of diseases and of conditions which make them especially inclined to predisposition to a disease. Besides the transference of such physiological peculiarities which pro- mote disease in the host organism from one generaticn to the other, the pos- sibility of an inheritance of parasites through the seeds of the host plant has recently been disputed. ErikBson', one of the most prominent investigators of rust diseases, describes a number of instances in rust of grain leaves which have led him to believe that with rust fungi embryonic developmental stages exist in which the fungi as naked plasma, Mycoplasm, appear united with the plasma of the host cell. Such symbiotic conditions can be present during the maturing of the seed and can exist as a dormant germ of the rust disease in the succeeding generation. With weather con- ditions favoring fungous development, the rust disease hecomes apparent by the mycoplasmated spots transmitted by inheritance in the form then known. The extraordinary difficulty of the question as to the existence of parasites in a mycoplasmatic stage has precluded as yet any fixed decision concern- ing Eriksson’s point of view. If the possibility of mycoplasmatic conditions must be admitted, we still think, however, that Eriksson’s assuredly correct observations may have this significance since the forms described have as yet been found only near mature spore centres. 10. DEGENERATION. From time to time, especially in practical work, it is asserted generally that our cultivated plants tend to degenerate, i.e. the quantity and quality of their crops diminish, and that certain varieties run out. The degeneration of such favorite cultivated forms, said to take place simultaneously in differ- erent localities, is often traced to senility since it is asserted that even those groups of forms, which we are accustomed to call sorts or varieties, like in- dividuals, are not able to live beyond a definite age. This point of view is supported especially by observations on our fruit trees, the varieties of which are known to be constantly propagated asexually by grafting or budding. Such varieties as a rule originate from one individual plant grown 1 See Literature in “Zeitschr, f. Pflanzenkrankh.’ Annual numbers for 1903 and 1904. 30 in a definite region, the branches of which are at once distributed as scions. It is now thought that all individuals produced by asexual! propagation act- ually represent only the continuation of the tree first developed from the seed. Now, since each individual has its own life period, this many-headed individual which we call a “variety” must fall victim to death after a definite length of time. In this way is explained the universally simultaneous sick- ening and dying out of many a variety. As examples of this kind are given Golden Pippin and Borsdorfer, two varieties of apple, on the degeneration of which there developed an extensive literature in the seventies of the last century’. Other old fruit varieties (especially apple) are said to suffer simultane- ously from sterility wherever grown, become cankered and die. Potato var- ieties, formerly widely acknowledged to be excellent, are no longer true to type and disappear from the market. The orange trees found formerly in European gardens as most vigorous old specimens become diseased every- where in spite of the greatest care. The celebrated orangeries at Sanssouci, Dresden, Cassel, Versailles etc. have vanished or are represented only by a few often sickly trees. Indeed, even in Italy, large plantations of lemon and orange trees have been attacked by diseases at present apparently incurable. The cause is said to be a weakness of growth which makes itself gradually increasingly felt, together with a diseased condition of the root. The same may be affirmed of grape vines and of olive trees, pomegranates, the Ericas (heathers) of Cape Colony, the Australian Papilionaceae and Myrtaceae, which formerly, as “Javanese” plants in special conservatories, formed the decoration and pride of gardeners. Even in our species of grains, we have noticed the disappearance of the good old varieties. This is the opinion of the representatives of the theory of degeneration. The theory of the continuity of an individual through all the scions, for which the stock, or the parent plant rather, serves only as nurse, is based on the presupposition that this individual retains all its characteristics un- changed during its whole existence as a variety wherever grown and on the different stocks. For, at the moment when it must be granted that the habi- tat or stock may change any peculiarities, a variation in the length of life due to different nutrition must also be considered a possibility. For this reason those who defend the theory of degeneration and a fixed life period of varieties (especially Jensen among botanists) insist upon the fixity of characters and support their theory by the fact that the varietal character always remains constant in seeds and in cuttings as well as in grafts. Def- nite shoot variations produced on any one specimen (variegated leaves, split leaves, forms with weeping branches, fasciations etc.) which can always be transmitted by grafting on new stock are proofs most often stated. 1 “Wearing out of varieties,’ Gardeners Chronicle 1875. “Do the varie- ties wear out?” ibid. “Degeneration from senility’ in the Fruit Manual 1875. “Golden Pippin degenerated” in Gardeners’ Chronicle 1875. Compare “Bericht uber die Verhandl. d. Sektion fiir Weinbau in Trier,’ 1875, etc., etc. 36 Such statements are refuted by the increasing results of grafting which show the mutual influence and change in individuals, incited by grafting. It is known that a form of albinoism, 1. €. the condition of having white leaves, which we can perhaps call “marbled,” is transmissible from scion to stock. Differences in the development of a scion dependant upon its being grafted on dwarf species or wild stock are known. Just as abundant are the examples of changes in size, structure, coloration and taste of the fruit ac- cording to the habitat and climate. Finally it should not be forgotten, that, in extensive cultivation of varieties, we always find some which “do not hold,” that is, which from the time of germination show so weak a growth that they soon disappear. This indicates a dying out of very young varieties. In this instance the theory of senility does not hold. In connection with the statement that varieties of fruit formerly highly prized no longer thrive and simultaneously run out wherever grown, it is interesting to compare some reports dating from the time when the question of degeneration became one of paramount importance, which concern directly some of the varieties of fruit said to be running out. Hogg stated in 1875, in “the Fruit Manual,” that Knight had complained of the “English Golden Pippin” as a variety at that time degenerating because of senility. He says that Mortimer, almost a hundred years before Knight, had spoken similarly of the “Kentish Pippin.” Healthy specimens of both varieties, however, are still found in England. The length of life and strength of cultivated varie- ties (says Hogg) may be proved by the “Winter-Pearmain,” which may be taken as the oldest English variety of apple, since it was mentioned in manu- scripts as early as about 1200. The Borsdorfer apple and the well-known plum “Reine Claude,” are very old. According to Bolle', the “Reine Claude” must have originated in the 15th Century since it was named in honor of Claude, the consort of Louis the XII (1490). These few examples show that the theory of degeneration due to sen- ity of individual cultivated varieties or due to other causes has heen formu- lated because a persistent retrogression has been observed in production and healthfulness from time to time in many localities, from which cbservations general conclusions have been drawn. The fact that in many regions culti- vated, well-preserved forms no longer show a thrifty growth and may be replaced by others, is undeniable. But this fact only proves that, since each cultivated form makes definite demands in soi! and climate, these demands can not be satisfied further in many places. Degeneration may he spoken of when a cultivated variety runs out universally, even in places where suitable conditions have been retained. However, proof of this is lacking. The breaking down of the varieties after long cultivation may be due to twofold causes, either the cultural conditions have been changed or the character of the variety has become different. In the first place, the fact that cultural conditions in any one locality are different every year is one to 1Quoted in Oberdieck, Pomolog. Monatshefte 1875, p. 240, Bouché and Bolle, Monatsschrift d. Ver. z. Beférd d. Gartenb. 1875, p. 484. 37 which we usually pay too little attention. Aside from the fact that the weather of one year always varies from that of the preceding year, the soil too is always different; indeed partly because the time and method of working as well as the fertilization and previous cropping in themselves always effect changes, and partly because this changed arable land is also subjected to changed weather conditions, so that it differs every year physi- cally and chemically for the same variety. In the main portion of the book a sufficient number of examples of the influence of planting, previous cropping, mechanical soil constitution and such factors will be cited and it will be shown how these can influence the character and power oi resistance ; as, for example, to frost. In the second place we think that the running out of a cultivated variety can also arise because the variety itself changes its character. According to our hypothesis, there is, in all organisms, no stability ; there is no strict ma- terial or formal repetition of any process, because the organism changes in the smallest unit of time, at each moment confronts the same factors of growth as a different organism and strides forward to adjustment. Thus each variety, like every term of relationship or of classification, is only a frame work made up of common characteristics in which individuals con- stantly fluctuate because of lesser variations. An excess of nitrogen develops a plant substance different from that produced by moderate nitrogen nutrition, a deficiency of potassium makes an organ different from that grown with an abundance of potassium. Abun- dance of light and deficiency of light develop the cell wall in different ways, great warmth produces more sugar than scanty amounts of heat, etc. Exact examples are given in the chapters on the action of individual factors of growth. Therefore the organism is like wax which, because of the thrusts of the individual vegetative factors, is constantly pressed into other material jorms. The material constitution of the plant body, however, is changed by the variations of the molecular arrangement which we call chemical changes, as well as by the mechanical ones in which the chemical composition remains constant. The mechanical disposition of water in the tissues, the substances carried in in the water, the tension conditions in the cell wall and the cell contents, are all factors which change constantly and as constantly influence each other differently. The slightest increase in the supply of light is a thrust which not only influences the assimilatory process, but must also in- directly exercise an effect on all other functions. This does not depend at all upon whether we can define these effects ;—the proof that they must take place is enough. Let us now consider how the thrusts of individual factors of growth act normally on the plant body. Here we notice a peculiar alternation. At day- break the action of light begins ;—assimilation, evaporation, thickening of the cell wall etc. are increased, the whole structure reflects all the phenomena of the light reactions. At nightfall, when the after effects of the light have 38 ceased, processes of oxidation come to the front, phenomena of increased turgidity, conversion of starch and the like. The same changes may be ob- served in the media surrounding the plant, in the air and soil. A decrease of warmth and increase of water content must act powerfully on the plant body. With the change between day and night is associated the influence of the seasons, which forces upon the plants a period of rest after a time of production. Therefore we find in nature a “corrective periodicity.” Amid these regularly alternating fluctuations of the vegetative factors, the plant balances its growth and completes its normal course of development. Since the duration and action of these periods in each year differ, the production of each plant differs also and the individual years are thus char- acterized. We speak of dry and wet years and know from experience that in the former, the yield of grain is noticeably large, while the straw yield is less on account of the shortness of the stalks. In wet years this is reversed. And although the farmer then complains that the baking quality of the flour has suffered, yet he emphasizes the fact that he finds compensation in the greater straw harvest. This example, taken from general practice, shows how great single vari- ations in the average periodicity at once becomes noticeable since the prefer- ence is shown for different peculiarities of the plant body. As long as this kind of one-sideness in development does not threaten the existence of the individual plant we may leave the results out of consideration and seek to equalize possible cultural variations (as, for example, by the crossing of grains possessing poorer baking qualities with those rich in gluten which come from dry, warm regions). However, the single prevalence of a definite atmospheric factor can also lead to direct disease since the effects are cumulative. Such an accumulation of effects may be compared to the increase in celerity in falling bodies where the distance of the fall equals the square of the time. If, instead of gravity, we assume another factor, such as wet, cloudy weather, it will in one day in- crease the water content of the tissue while the wall thickening remains be- low normal. On the second day, the first day’s action is doubled and the already porous tissue becomes still more porous. The thrust against the plant body, which in itself would not produce disease, is cumulative to an extent ultimately threatening the plant’s existence. Practically we find this even within one vegetative period, as, for example, Jodging of the grain in rainy seasons. The moisture has lengthened considerably the cells at the base of the stalk while the deficiency of light has essentiaily arrested the thickening of their walls. The result is that the weakened base is not able 1o sufficiently resist the strain of the wind and gives way. The development of the grain is weakened or inhibited, according to the extent of this lodging and the phenomena resulting from it, so that the stalk iself is also brought to a premature death. Corresponding to the above mechanical changes in the wall, the cell contents are subjected to changes leading to a diseased condition in the case 39 of other influences on the part of the vegetative factor which accumulate along one line. We find in heavily fertilized nurseries, whole plots of lux- uuriantly growing sweet cherries with open or hidden gum spots and in forests whole tracts and healthy looking beds of conifers which show in their wood-tissue the beginnings of a resinous condition. Jn garden cultures especially, which on an average are worked with the largest quantities of nitrogen, whole plantations suddenly become diseased and are abandoned because the “plants will not grow.” Enough cases of this kind have reached me, in which individual breeders have announced that Begonias, Primula sinensis fl. pl., carnations, lilies-of-the valley, cyclamen and others which at cther times under the same cultural methods had always been produced in the greatest perfection, retrogress from year to year and “degenerate.” Sim- ilar conditions may be observed in field cultures. Entire fields of potato varieties which formerly gave faultless crops now easily become black specked. Sugar beets grown in the soil best suited to them tend to root rot. It has been observed in the root rot of beets that plants grown from trans- plants became diseased especially easily, while seedlings from the best and heaviest sugar beets showed almost no root rot. Cucumbers forced under glass, and those grown in fields in wet, cold years are spoiled by gummosis, and the like. My experience in remedying such occurrences leads to the conclusion that an increase of one definite line of development is concerned in these cases which is usually called forth by excess of nitrogen and water. Our constantly increasing intensive cultivation not infrequently leads to a showy luxuriance of the plants and then to a sudden collapse, if the equaliz- ing factor is not able to act in a corresponding amount. Accordingly in cases of a shown great nitrogen supply, I found the use of calcium phosphate to be very advantageous. Such one-sided lines of development will also appear necessarily in the development of the seed. If it is cultivated from generation to generation under the same nutritive conditions, as when first produced, definite peculiari- ties of its place of growth must become hereditary through habit. Accord- ing to our theory that all peculiarities of an organism represent dynamic conditions and molecular vibration-groupings, the habit would necessarily be explained as inertia. The law of inertia of ali matter requires that it re- mains exactly in the same course and at the same rate of motion. Thus the organism keeps on vibrating as it has once been impelled, until some factor of vegetation changes the rate of its growth or the direction. Practice utilizes this circumstance in the ‘“‘change of seed,” that is, in the use of seed from other places which have developed a definite desirable peculiarity. Thus the use of Swedish grain by Middle-European agricul- turalists has become more extensive because it is desirable to take advantage of the shorter vegetative period of the northern varieties. While an especially developed mealy condition is typical of English wheat, regions with opposite climate conditions produce chiefly hard wheat etc. 40 Just as useful types of grain arise as the products of atmospheric and soil conditions, weakened conditions of the cultivated plants may also be produced locally and transmitted through seeds. If these weakened con- ditions are repeated from generation to generation by the persistence of causes and accumulate, they may lead in the end to a complete decline and to premature death. Yet this is, however, no degeneration of the species or variety, for all these characteristics may be reproduced under other cultural conditions. “We perceive this from the fact that the useful special characteristics introduced by a change of seed, are retained only a few years. Then the imported culti- vated forms become changed and assume characteristics such as are due to the climatic and soil conditions in the place where they are cultivated. Such is also the experience in practice work which constantly attempts in some way to accustom (acclimate) highly productive species of a different climate, to some one cultural region. If it seems desirable to apply the term “‘degeneration” to the above cases of the accumulation of peculiarities leading to a weakening of production and to premature death, it is possible at most only to speak of local transi- tory degeneration of a number of individuals. It is, however, really only a depression of the direction of development, which can be raised again by external factors, such as cultural methods. A persistent depression in growth as a result of the senility of an originally long-lived variety, is not to be assumed within any definite epoch. The disappearance of cultural. varie- ties is explained by a decreased profitableness resulting from a deficient power of adjustment to our agricultural methods, which are constantly be- coming more intensive. SECTION 2 Ful TORICAL SURVEY: In any branch of knowledge so young as phytopathology, any history of the science can scarcely be presupposed. And in fact the date after which the teaching of plant disease was set up as a special branch is so recent that we are still able to survey completely the course of its development. If, however, the form of investigation is still new, the material, viz., 1eports on plant diseases, is very old, extending far back in history. We can not go astray in assuming that there have been diseases since the existence of the plants began and that observations on these began with their cultivation. Tor we constantly see what heavy injuries are produced by atmospheric ex- tremes, and indeed not only by those disturbances which instantly kill the plant, but rather by such as weaken the individual in structure and form, and slowly lead it toward a premature death,—i. e. make it sick. The action of injurious atmospheric conditions must have existed always and have made themselves evident in different forms. One of the oldest names which we find for certain forms of sickness, is “blight.” On this account we will attempt to trace the growth of our branch of knowledge by following the observations of the diseases which this name connates. As the later reports show, at first all those phenomena were character- ized as “blight,” which appeared to the eye to have the color of burned or charred matter, that is, black. Accordingly “blight’”” comprised on the one hand the groups of tree diseases, in which the dead bark assumed a black- ened appearance, on the other hand also the injuries to grain, the causes of which we trace back to smut and rust fungi. If we look first in the Bible for mention of diseases and especially of “blight,” we find, for example, the following:—*“If there be in the land famine; if there be pestilence, blasting, mildew, locust, or if there be caterpillar; if their enemy besiege them in the land ¥ 2“The Lord shall smite thee with consumption and with a fever, and Again :— 1 First Book of Kings, Chapter VIII, 37. Second Book of Chronicles, Chapter VI, 28. 2 Deuteronomy, Chapter XXVIII, 22 42 with an inflammation, and with an extreme burning, and with the sword and with blasting and with mildew; and they shall pursue thee until thou perish.” From these verses Eriksson! concludes that these statements, which are more than two thousand years old, refer to smut and rust in grain. He cites the word Schiddafon (heat) for mildew or blight and Jerakon (yellowness) for rust. The following sentences already quoted by Pammel? point to mildew in grain:—“I have smitten you with blasting and mildew: when your garden and your vineyards and your fig trees and your olive trees increased, the palmer-worm devoured them . .:. . .% Descriptive of the extent of the failure in the harvest is the verse in Haggai*: “Since these days were when one came to an heap of twenty measures, there were but ten:—when one came to the pressfat for to draw out fifty vessels out of the press, there were but twenty. I smote you with blasting and with mildew and with hail in all the labors of your hands zn Among the Greeks, Aristotle (384-322 B. C.) mentions the years of rust and Theophrastus of Eresus (371-286 B. C.) recognized the varying susceptibility of the different varieties of grain to rust’. He reports also a second kind of phenomena termed blight, i. e. the bark blight of trees, since he says (Book 14, Chapter 14) that the cultivated trees are subject to several diseases. Among these, some are common to all trees while others attack only certain tree species. One universal disease is the attack by worms or by blight. Theophrastus, whose statements, according to Kirchner®, are certainly based on his own observations, speaks especially of the blight and canker of fig trees and mentions in this connection that diseases of trees (as of animals) seem to be determined by climate, since in some regions these same trees are healthy. The fig tree, he says further, is attacked mostly by blight and canker. Blight (Sphakelismos), however, is spoken of when the roots become black, canker (Krados) when the branches become so. The wild fig tree, on the contrary, has neither canker nor blight. The statement, that some fatalities are due to the influence of atmos- phere and habitat, indicates to us the cause of the disease. Such phenomena can not really be termed disease, as, for example, freezing and what some call blight. In some places certain winds also kill and burn the plants, as at Chalcis in Euboea, where the northwest wind is cold, if it blows shortly be- fore the solstice. It blasts the trees and dries them, almost more than the sun. 1 Eriksson, Die Getreideroste. Stockholm 1894, p. 8. (Here detailed historical reports on rust). 2 Pammel, L. H., Weems, J. B. and Lamson-Scribner, The Grasses of Iowa. Des Moines, Iowa, 1901. 3 Amos, Chapter IV, 9. 4 Haggai, Chapter II, 16-17. 5 Naturgeschichte der Gewichse. Translated and explained by Sprengel. Al- tona 1822. I. 6 Kirchner, Die botanischen Schriften des Theophrast von Eresos. Sond. Jahrb. f. Klassische Philologie. Leipzig, 1874. 43 It is doubtful whether the disease mentioned here as canker bears any resemblance to the outgrowths at present called canker. It is certain, how- ever, that woody excrescences were also observed. If actual canker swell- ings are not concerned here, yet the phenomena may well have been meant, which we would now call knar!s. Theophrastus found this kind of swellings in olive trees and called them nails or scurf (loxas-lopas) because they represent bowl-shaped nails on the trees. Sprengel says of these nails, that they have occurred recently very abundantly on the olive trees in Italy. They appear as round, warty outgrowths of the bark, depressed in the centre like a bowl. Among them may also be found similar swellings of the wood body. It is scarcely credible that the points of view expressed by closely ob- servant scholars of Aristotle, concerning the phenomena of disease here men- tioned, changed essentially in the course of the following centuries, for other- wise the celebrated encyclopaedist Plinius Secundus', who lived from 23 to 79 A. D. and who possessed a wide knowledge of literary sources, would have brought forward further material at the time he recorded scien- tifically the statements of Cato (de re rustica) and others as to the influence of the stars and the death of trees resulting from cold, heat, unfavorable position, soil, fertilization, incorrect pruning and the like. The discoveries set down in his “Natural History” contain much worthy of notice regarding the influence of atmospheric factors, cultural mistakes, circumstances pre- disposing to disease etc. In the edition of the ‘“Rémischen Prosaiker” by Osiander and Schwab, the translator of Pliny (Kulb) has given a summary of Pliny’s sources and special remarks on the authors instanced in his “Natural History.” There is rich material here for a complete history of phytopathology. We must content ourselves with a reference to these carefully collected Greek and Roman sources and perhaps show by only a few more quotations what exten- sive discoveries had been made at the beginning of our era. According to this, there may be found in the seventeenth book of Pliny’s “Natural History,” Part XX XVIL., his statement of the action of frost. He says, ‘““Not the weak- est trees are endangered by frost, but the largest ones, and, therefore, when they do suffer, the highest tips become blasted, because the sap arrested by the cold can not reach that point.” We find the following note about the phenomena, which we would now call “frost blight,’—‘“The evil influence of the stars depends entirely on the Heavens; on this account there must also be included among these effects, hail as well as blight and the injury caused by white frost. The blight especially attacks tender plants if, enticed by the warmth of spring, they venture to break through the ground and it singes the juicy buds of germinating plants. In blossoms this is called blasting.” In regard to carefully cultivated grape vines, one reads—“Another bad influence of the stars (atmospheric factors) is the covering with dew 1 Plinii Secundi naturalis Historiae libri XXXVII edit. Janus. Book 17, Chap. 37. 44 (roration, the falling on them of cold dew. Kulb) while they are in bloom, or when the berries become hard grains and spoil before they mature. They also become diseased, if they freeze and the blight injures the buds after pruning. Untimely heat has the same results, for everything has its definite measure and goal.” At present we summarize the experiences more exactly in our teaching of an optimum and of minimum and maximum limits for the factors of growth. In reference to defective cultural methods it 1s stated that diseases arise when the vine-dresser ties the vines too tightly or injures the roots when digging around them and barks or bruises the trunk. Under all these con- ditions they (the vines) endure wet and cold much less easily because each injury penetrates into the wound from without. Scarifying is recommended as a remedy because the thickening bark fastens the stems together and plugs them. As a protection against the frosts of winter, 1s mentioned the method by which water-ditches are dug about the grape vines in winter, when the ground is covered with snow, so that the cold can not blight them. The most abundant information as to cultural methods and the evils attendant on them may be found in the collection of excerpts from old agri- cultural authors, which was made in the tenth century, the “Geoponika.”’ We base our discoveries here on the books of the four well-known Roman Geoponicists, Marcus Cato, Terentius Varro, Palladius and Junius Modera- tus Columella, in which special attention is paid to the practice of fertilization and grafting. A compilation of the books on agriculture by the authors here named appeared in Cologne in 1536'. From this work I will choose those places which show that the term “rust” as a cause of disease is of very early origin. Thus Varro mentions in the first chapter, among the gods, “qui maxime agricolarum duces sunt” “Quarto Robigum, et Floram, quibus propitiis, neque rubigo fru- menta, atque arbores, corrumpit, neque non tempestive florent. Itaque publicae Robigo feriae, robigalia, Florae ludi, floralia instituti.” The ex- pression “rust”? was used probably for all rust colored, diseased discolor- ations in plants, for we find the word Robigo used by Columella to designate a disease of grapes which can be avoided, when frost threatens, by smudging the vineyards. In his book, “de arboribus,” Chapter XIII treats of: Ne rubigo vineam vexet. It is recommended “Palearum aceruos inter ordines uerno tempore positos habeto in uinea: cum frigus contra temporis con- cuetudinem ne intellexeris, omneis aceruos incendito, ita fumus nebulam et rubiginem remouebit.” The following place is found in the “Enarratio priscarum vocum” in regard to the interchangeable usage of “Robigo” and “Rubigo” ; “Robigo, deus, quem putabant rubiginem auertere, est aute Rubigo morbus segetum’”’. 1 De re rustica M. Catonis liber I, M. Terentii Varronis lib. III., Palladii lib. XIV. et I. M. Columellae lib. XIII. Priscarum vocum in libris de re rustica enar- rationes, per Georgium Alexandrinum. Coloniae, Joannes Gymnicus. Anno MDXXXVI. 2 Here, as in the following citations, we will follow our sources exactly. 45 The next fifteen hundred years accepted the observations and theories of the Romans, which may be found collected in Pliny. For E. Meyer! teports from Petrus de Crescentiis who wrote his great work in 1305, the first eight books of which treat of agriculture, that since Palladius no one had written anything in Latin on agriculture. Only fragments of the Greek collection of the Geoponika were to be found. The older works of Varro and Columella were no longer suited to existing conditicns, so that there was need of an up-to-date book on agriculture. Yet the book by Petrus de Crescentiis actually contained less than the books of the older authors, al- though he strived for a scientific foundation for agriculture and gave num- erous directions for grafting various kinds of trees, in accordance with the favorite pursuits of antiquity and of the middle ages. In the same way in 16000 Colerus> also only repeated the earlier statements regarding the cutpushings of the bark,—‘Inflammation of trees” (“Schwulst der Bewne’”’) inder which there develops a putrid liquid. In this book the influence of the stars was believed in, with unshaken firmness. For example, in his “Horti- cultura” published in 1631, the renowned Professor Peter Lauremberg* of Rostock relates that certain stars like Orion, the Pleiades and others exert an especially injurious influence and that, as a result of injurious atmos- ‘secret evils” arise, among which belong rust, ‘ pheric influences, the so-catled carbuncle and mildew. We can naturally expect to find progress in the recognition of the sig- nificance of disease among practical workers, whose cultural efforts are most sensitively disturbed by injuries making themselves felt in their work. The book of the “Electoral Superintendent of Gardens,’’— Heinrich Hesze*,— which was famous in its time, is interesting in this connection. He speaks of the blasting of the branches which he calls “blight and cold,” “otherwise there are three chief causes for the blighting of trees. First, superfluous moisture which, with inflammation of the sap, 1s collected be- tween wood and bark, distending the latter and blighting and blasting it. The second is this,—that oftimes, thoughtlessly and with a lack of judgment, the tree is set in a postion different from the one in which it stood before. This is very injurious, since the bark where it is brownish and has been exposed to the east or south, is therefore much harder than on the sides toward the north or west. These are generally green, tender and immature. Therefore, some injury must inevitably arise from this, since the north side is not at all accustomed to the southern sun and is not only blasted by the great heat but in the spring is injured by the hard frosts; the bark is raised, then later in the day dried up and scorched by the sun. From this the blight at once arises, since it is commonly noticed on the southern side.” Here we have posi- tive personal observations. The author relates further that he has never- 1 Geschichte der Botanik. Vol. IV, p. 148. 2M. Joannis Coleri, Oeconomia und Haussbuch ete. Ander Theil. Wittenberg 1600. Book V. Chapter 12. 3 Petri Laurembergii, Rostochiensis Horticultura. Francofurti 1631. Cap. XXXV. 4 Heinrich Heszens, Neue Gartenlust ete., enlarged and provided with three useful indices by Theodorum Phytologum. 1690. Chapter VIII. 40 theless preserved trees thus reversed in position by placing a covering of cow manure, oat chaff, glue and ashes on the side of the tree unwisely turned toward the south. “The third case, however, arises when a bread knife is used in grafting etc.” Perhaps Hesze has in mind here some parasitic in- fection and attempts to explain it. Hesze (p. 312) writes “that canker (“Krebs”) really orginates from the grafting of a tree at the time when the moon lies in the sign of the crab or scorpion....” “This disease may be recognized by the fact that here and there the bark throws up little hummocks under which the tissue is dead and black. This spreads further and further, ultimately infecting the whole trunk. Many scattered causes of canker have been brought forward, but the one given above is the most probable of all.” The Editor makes the following addition to this statement,—“So far as canker is concerned, no one can deny that it often arises high up on the trees, and, in fact, in the accumu- lations of dirt which collect between the trunk and the branches at their crotches. On this account, it is most necessary that the crotches always be kept clean and freed from all dirt. Thus the canker often arises from the same rising sap which produces blight and the two diseases often have but cne cause.” The author clearly describes the phenomenon which we now term limb canker and, instead of “ascending sap,” we insert, injuries due to frost witha subsequent infection by Nectria ditissima; his presentation corresponds with our present conception of blight and canker. About this time in France, de la Quintinye wrote “Le parfait jardinier”’ which is still much sought after. In this we find canker briefly mentioned as a kind of gall (signifie une maniere de galle ou de pourriture seiche), formed in the bark and the wood and often found on pears (Poire ae Robine, Petit Muscat, Bergamotte), on trunks as well as branches. The conception of the swellings of the wood indicated by the term “canker’’ is found further in the writings of later horticultural authors, as, for example, in Fischer’. The boastful Agricola’ (born 1672) stands independent, that is, on his personal, repeated and practical experience. His aciuia! service is found in his numerous experiments, carried out from 1712-1715, on the vege- tative reproduction of plants (especially by roots). He devotes the fifth chapter to “occurrences and diseases” and expresses himself, for example, as follows :—‘“Mildew, Rubigo, however, prevails at times, as a pestilence among trees. In spring, when the earth opens and the enclosed vapors be- 1 Le parfait jardinier etc. Par feu Mr. de la Quintinye. Paris 1695. Vol. L., Dewesils 2 R. P. Christophori Fischeri soc. j, Fleissiges Herrenauge ete. Niirnberg 1719. 5 Section I., p. 168. 3 Georg Andrei Agricola, Philosophiae et Medicinae Doctoris und Physici Ordinarii in Regensburg, Versuch einer allgemeinen Verhmehrung aller Biume, Stauden and Blumengewidchse anjetzo auf ein neues itibersehen usw. von C. G. Brausern. Regensburg 1772. The original title readi—‘‘A new and unheard of ex- periment, well founded in nature and in reason, for the universal increase of all trees, bushes and flowering plants,” 1716. 47 gin to rise, it injures most of them and ts nothing else than a very sharp and biting dew, originating in the earthy vapors and conducted from them . In the third place a disease occurs among trees, which is called sunblight, or blight, wredo, which, however, may be of two kinds. First, when a fine rain or dew falls or settles on the leaves while the sun shines, the ducts or tubes, becoming flabby and distended, are contracted at once by the heat of the sun. Thus the leaves are scorched, begin to turn brown and black and fall. In the second case, the uredo or blight is found in the inner parts of the trees, inthe pith’ @).- . . The true cause, however, for the blighted pith, when the tree is transplanted, may well be, that the common gardeners have the habit, in transplanting, of pruning all the roots and do not understand how much they are injuring the tree. For the smallest roots draw the most sap from the earth, and these are the ones they cut off . . . . Now because the root, together with the pith, is open and exposed, moisture can penetrate and injure the pith Fe In regard to canker, we find the “ascending sap’ emphasized as its cause in the horticultural lexicon by Riedel published in 1751*. “Can- ker, tree-cancer, canker, devourer,’ thus is listed the injurious attack on the trees which appears in the bark,—since it forms hummocks here and there and springs up.—And therefore, if the devouring evil is not overcome in time, one branch after another, and eventually the whole tree, is ruined The real cause, however, of this injurious attack on the trees is cither the evil peculiarity of the earth and the evil juices produced or arising from it which become so inflamed within the bark that this looks black when removed, or the ascending superfluous rank juice, which, finding no escape, must clog and spoil, thus becoming the cause of the out-pushing and bursting of the bark.” Instead of the ascending sap, the expression—‘‘corigestion of the sap,” is used at present. As a remedy for canker, this author recommends cutting out the dis- eased places and coating with grafting wax. If the cause lies in the soil, this should be removed up to the roots and replaced by new soil. When the sap is excessive, the base of the tree trunk should be bored in February, and the hole wedged open for 1 to 2 days with a firm wooden peg or a strong root should be split, “ since the superfluous sap will then be drawn downward.” Philipp Miller? traces phenomena of disease directly back to frost, and calls them “blight.” Miller’s decisions are essentially a repetition of Hale’s theories that by blight (blast) not only frost but also sun scorch etc. are understood. Hale’s* statements are important because he men- tions the transmissability of canker in budding and of its occasional heal- ing by being cut out. The observation of this English experimentor on the 1 Riedel, Kurz abgefafstes Gartenlexicon usw. Nordhausen 1751. p. 420. 2 The English Garden Book or Philipp Miller’s ‘Gardener’s Lexicon” etc. From the Fifth Edition translated into the German by Huth. Niirnberg 1750, p. 136. 3 Statical Essays containing Vegetable Statics etc. by Steph. Hales. 2nd edition. Mondon! Lisle Tssb ht, L47, 369; Ml, 265. 48 influence of the dry spring winds, which scorch the foliage is worth noting :— “The considerable quantity of moisture which is given off from the branches of trees during the cold winter season, plainly shows the reason, why, in a ‘ong series of cold, northeasterly winds, the blossoms and tender young set fruit and leaves are so frequently blasted in the early spring, viz. by having the moisture exhaled faster than it can be supplied from the trees.” Duhamel' pays great attention to injuries from frost and _ states that trees are often attacked by swellings which may be more easily healed in younger than in older trees. At some place on the trunk, the bark is loosened from the wood and a devouring pus occurs between the two. Devouring ab- scesses of this kind are called “canker” which is counted among the diseases produced by a superfluity of sap. Das Niedersachsische Gartenbuch? finds the cause from blight and canker in too thick standing of the trees, in un- favorable soil ete. While in ancient times and in the middle ages observations en plant dis- eases were usually limited to a perception of the mature phenomena visible to the naked éye and the solution of the questions of plant life were sought almost entirely among experiments of budding, we find that the experiment itself attained its own importance with Hales and Duhamel. Simultaneously with experimental physiology came the wider classifi- cation of plant diseases. We follow here Seetzen’s® treatment of the subject and its history. Seetzen states that Tournefort had a finished system*. His first class includes the diseases due to internal causes, as opposed to the sec- ond class, the diseases produced by external causes. To the first class he as- cribes:—1-La trop grande abondance du suc nourricier; 2-le défaut ou manque de ce suc; 3-quelques mauvaises qualités qu’il peut acquérir; 4-la distribution inégale dans les différentes parties des plantes. In the second class belong:—1-La gréle; 2-la gelée; 3-la moisissure: 4-les plantes, qui naissent sur d’autres plantes; 5-la piqueure des insectes: 6-differentes tailles ou incisions, que l’on fait aux plantes. We find Tournefort’s point of view in our modern systems. We group the diseases caused by excess or deficiency of water and food, with injuries produced by weather extremes (frost, hail) etc. In the same way, we treat wounds as a separate division. The parasitic diseases appear for the first time as such in Tournefort’s book. Less fortunate is Zwinger’s® system which appeared shortly after Tournefort’s and which also is formed of two main groups,—(1) General 1 La physique des arbres par Duhamel du Monceau. Paris 1758. p. 339. 2 Caspar Bechsteat, Vollstindiges niedersichsiches Land- und Gartenbuch. Flensburg und Leipzig 1772. I, p. 151. 3 Systematum generaliorum de morbis plantarum brevis diiudicatio. Publico examini submittit Ulricus Jasper Seetzen. Gottingae MDCCLXXXIX. 4 Observations sur les maladies des plantes par M. Tournefort. Mém. de l’Ac. Roy. des Sciences a Paris 1705, p. 332. 5 Jo. Jac. Zwingeri, Diss. med. inauguralis de valetudine plantarum fecunda et adversa. Basileae 1708. 49 and (2) Specific diseases. The first includes:—La gangrene—le desséche- ment—la surabondance de suc-—le branchage excessif—une espéce de galle, qui manche l’ecorce. In the second main group we find:—Le desséchement des racines—la separation de leur écorce—la grosseur excessive des racines, qui retienent tout le suc de la plante—les excroissances—les coups et les biessures. It is evident from this division of closely related phenomena that the author had not fully mastered his material. Eysfarth’st system gives a classification which the layman easily grasps. It uses as its basis the different periods of the plant’s life. In the first class are the diseases of the period of germination; in the second, those of the actual vegetative period and in the third class, the disturbances of the sexual period. Under each class are discussed the influences of weather extremes, injuries due to animals and other wounds. In this book there is also a chapter “a rubigine aut pruina.”’ The thoroughness of the classification shows that the author had well worked out his material. Adanson? returns to Tournefort’s division since he sets up as his first main group the “maladies dues a des causes externes,’ and as the second, the “maladies dties a des causes internes.”” Even the introduction shows the advance in microscopic investigation and the increased attention paid to parasitic fungi; under the first main group, the different chapters take up, for example, Le givre ou Jivre (Erysiphe Fabrici)—la rouille 290é:¢y4 ‘Theophr. (Rubigo)—le charbon (Ustilago)—la pourriture (Caries Fabr.) etc. Adanson often uses the terminology of Fabricius who probably had published his studies in separate treatises before his classification had ap- peared as a whole, for his complete classification did not appear until 1774*. Fabricius certainly based his views on his own observations. This is less noticeable in the formation of the main groups than in the sub-divisions of the different chapters, in which a classification of the cases according to their different causes has been stated, even when the external appear- ance was similar. Thus, for example, we find in the first main group :— “Vfrugtbargiédrende Sygdomme,” i.e. the disturbances leading to sterility ; a section “Dovhed” which may be translated by etiolation or the yellows. This is divided into D. af Regn, af Kulde, af Rog etc. His observation that, besides rain, cold and other factors, ‘‘yellows’” may be produced by smoke is also worth notice. In the second main group, ‘“‘Udtaerende Sygd,” i.e. the at- rophias, there is found under the section “Quaelelse,” etiolation from “stedets Indslutning” (too close planting), from “paa Lys” (lack of light) and from clinging plants and insect injuries. Another group is separated from these phenomena,—‘“Taering” (Tabes, Jaunisse in Adanson) where the yellowing is due to insufficient nutritive substances, unsuitable soil conditions, ex- 1 Christ. Sigismund Eysfarth, Diss. phys. de morbis plantarum. Lipsiae 17238. 4°. 2 Adanson, Sur les maladies des plantes; in ‘Familles des Plantes.’ Vol. I, p. 42. Gon enoc. 8 Forsog til en Afhandling om Planternes Sygdomme ved Joh. Christ. Fabricius; ind der kongelige Norske Videnskabers Selskab skrifter femte Deel. Kjobenh. 1774. Sid. 431-492. 50 cessive evaporation after transplanting etc. The third main group is taken up with “Flydende Sygdomme,” that is, sap-currents, under which is included honey-dew. In the fourth group are found the “Raadnende Sygdomme” which, according to our point of view, might be termed soft rot, putrefying bacteriosis or scrofula. Among the causes figure also the ‘“‘Snylte-Planterne,” i.e, parasitic plants. In the fifth and sixth groups, wounds, frost splits, galls and monstrosities are treated. In 1779 appeared the German translation of the Zallinger’ classi- heation with the evident endeavor to utilize the terminology of animal path- ology in plant pathology. Zallinger makes five classes:—(1) Phlegmasiae or inflammatory diseases; (2) Paralyses seu debilitates, laming gouts or de- bility; (3) discharges and draining; (4) Cachexiae, bad constitution of the body; (5) chief defect of the different parts. In order to characterize his theory, let us look for the disease which, with blight, forms the main example in our entire presentation,—viz. canker. Zallinger puts this in the class of the Cachexiae, in the subdivision of the ulcers, under which he includes rachi- tis or abortive growth, leontiasis or rough warts on the skin and others. He mentions blight, Gangraeno s. Sphacelus as an abnormal Cachexia, together with Phthiriasis or lousy disease and Vermiculatio, the production of worms. From this classification it may be concluded that the author has let himself be guided by the frequently similar appearance of the phenomena, for the dead places in the bark offer a favorable centre of attack by insects. What we now term grain smut is found as Ustilago, or deformity of the seed, under the class of draining. Fabricius had placed ‘“‘Kraebs,” Cancer, in the class of diseases of decomposition. Batsch’, in his introduction to the knowledge of plants, also pub- lished a survey of the diseases which he divided into those based on the “de- composition of the firm and fluid parts,” i. e. on the constitution of the plant, and into those caused by “animals and plants.” Any one, however, looking for our cryptogamic parasites in the latter section would be deceived. These are rather to be found in the first class, in agreement with the conviction already advanced by Zallinger (s. Ustilago), that the parasitic organisms are not independent plants but only develop- mental forms of the higher plants. Thus Batsch under constitutional dis- eases has one group “Brandige Veranderung des Wesens,” change of char- acter due to blight, the first family of which includes the phenomenon, where a decomposition of the tissue into powder “smut, Ustilago” takes place. The second family contains the transformation of the tissues into “a spongy mass (Ergot, Clavus).” These views remained in force for some time, as will be seen from the following section. 1 Abhandlung tiber die Krankheiten der Pflanzen, ihrer Kenntnis und Heilung; translated from the Latin by Joh. Count vy. Aauersperg. Augsburg 1779. 8°. 2» A. J. G. C. Batsch, Versuch einer Anleitung zur Kenntnis and Geschichte der Pflanzen etc. I. Theil. Halle 1787. p. 284. pe By means of the works of the authors mentioned and the discoveries of practical horticulture, as well as the great sensation called forth by the tree wax for injured trees which was discovered by William Forsyth in 1791 and universally overestimated, the conviction of the agricultural significance of plant diseases was extended over so wide a circle that special books could now be published for this branch of knowledge. The year 1795 makes us acquainted with three such works. The first one written by Plenk! treats of the diseases of all cultivated plants of importance at that time and is based on thorough observations. He de- scribes thus :—“a spongy large outgrowth at some place on the trunk from which exudes, even in the most scorching weather, a caustic moisture which corrodes the whole extent of the swelling.” Thus Pyrus Cydonia, standing near a swamp, was attacked by tree canker while other quince trees planted in a higher place were healthy. The sap, it seems, becomes so caustic from the acidity of the standing water that it eats up the ducts. There are two kinds of tree canker determined by the difference in the location of the dis- ease; first, open tree canker, when the canker knots appear on the external surface of the bark; second, hidden canker, when a sharp cancerous pts collects between the bark and the wood but does not escape from the bark in any place. In both cases the tree becomes incurably wasted, when the parts attacked by canker are not cut out at once and covered with wound wax. In this blight Plenk distinguished between a dry and a moist blight. By the first he means “a black and dry wilting of the leaves or of some other part of the plant” and by “moist blight” he designates the “moist and soft degeneration of the plants into a putrid pus.” We find almost the same terminology in the explanation of canker in Schreger’s? book which otherwise gives many of his personal obser- vations. In regard to the phenomena of blight in which the bark or other parts of the tree appear black and soft and are consumed, he says, “Such black spots of the bark grow further and further round about themselves even attacking the wood so that the bark itself at last splits off, as if dead, and the wood appears dry and black, as if burned.’ This explanation cor- responds exactly with the phenomena which we perceive when frost causes considerable injuries to the bark. In fact this observer arrives at the same conclusion as we do in regard to the cause. ‘‘Bruises from hailstones give rise to its production and also cold frosts. This frost is more injurious in low and moist regions than in high dry ones. For this reason there is less injury from frost on windy nights than on clear, cold ones. If the trees {freeze in winter and die, the cause of their death is usually a blight induced by this freezing. This happens sometimes when the severe cold comes too early in the autumn while the sap is still flowing actively ; sometimes in the spring when the sap, so to speak, has begun to run. The latter case is the 1 Plenk, Physiologie und Pathologie der Pflanzen. Wien 1795. ; 2 Erfahrungsmissige Anweisung zur richtigen Kenntnis der Krankheiten der Wald- und Garteniume. Leipzig 1795. 52 most dangerous of all. Even in midwinter with very great cold they rarely freeze; it might be when it has rained the day before.’’ On pages 420 and 500, he says of apple and pear trees that “an excess of fatty, oily fertilizers easily develops blight and canker,” i.e. creates a predisposition: The third one of the books published in 1795, the one by Ritter v. Ehren- felst is even more specialized, for he treats only of fruit trees. He declares that all kinds of trees would be subject to blight and that “this decay which appears first in the bark and then in the wood” is the most common disease of trees and in some books is termed canker. The description which he gives is so clear that it can be identified as the phenomenon now known as Nectria-canker. He says, “the indication of this evil attack is first of all a black or blackish bark which, six or eight days after its appearance, is often pushed out, forms little splits and gradually loses its connection with the trunk of the tree so that it clings only loosely to the shaft. After some time the loose bark is entirely separated from the trunk and exposes the wood. In this new stage the vitality of the sick plant does its very best to help itself and unceasingly throws off the unfavorable or sick parts, but this vitality finally becomes weakened and the tree dies. The tree attempts to form a new bark which grows in folds more or less overlapping and tries to cover the exposed places” . . . . He ascribed the cause to injuries as, for example, from injudicious pruning, injuries due to insects and the like, “even at times the tendency to blight lies in the disposition of the tree itself,—a disposition which the trees obtain from the soil in which they grow, from their descent and from an unwise cultivation.” In the pomological glossary published at the beginning of the last cen- tury, Christ? added to the above by the further statement, that the blight ‘often is due to freezing in winter.” Burdach? also bases his statements on his own observations and says of blight, “this disease is an indirect result of weakness and commonly arises in those trees whose growth has been hastened by strong forcing and fertilizing or which have been transplanted to a poor garden soil where only the upper part of the ground has been improved. In cherry trees, still an- other evil effect arises from the same cause, viz. the exudation of resin or gum.” ; The theory of the influence of the soil and fertilization, as among the most important causes of plant diseases, is now laid aside for some time and attention is given to the manifold and extensive investigation of the province of fungus life. Although antiquity had already recognized a number of edible and poisonous fungi, yet their attentive observation and systematic study began 1 Ritter v. Ehrenfels, Ueber die Krankheiten und Verletzungen der Frucht- und Gartenbiume. Bresslau, Hirshberg und Lissa 1795. 2 Pomologisches theoretisch-praktisches Handwo6rterbuch. Leipzig 1802. 3 Systematisches Handbuch der Obstbaumkrankheiten, Berlin 1818. a2 first in the Middle Ages with the foundation of classification of the vegetable kingdom. According to the statements of Cordat, Andreas Caesalpinus (1583) was the first to gather together the fungi in his celebrated book “De plantis.” He describes sixteen genera, Tuber, Peziza, Fungus, Boletus, Suil- lus, Prunualus, Prateolus, Familiola, Scoroglia, Fungus marinus, Gallimaceus, Fungus panis similis, Lingua, Digitellus, Igniarius and Agaricum. As it seems, even marine animals have been included here. After almost one hun- dred years appeared Joannis Raji’s “Methodus plantarum” Londini 1682. In 1710 Boérhave followed with his “Index plantarum horti Lugdano-Batavi” and in 1719 Tournefort appeared with his “Institutiones Rei herbariae.” The chief work to which modern mycology must refer appeared in 1729 in Micheli’s “Nova plantarum genera” in which the fungi are most carefully described and illustrated in more than 100 pages and with 12 piates. Micheli studied their life phenomena more closely and was the first to observe the attachment and dissemination of spores. Among the genera there described are found those which are considered in plant diseases, Aspergillis, Botrytis, Puccinia (now Gymnosporangium), Mucor and Lycogala. There now follow in quick succession “Methodus fungorum” by Gled- itsch (1753) and the “Fungorum agri ariminensis historia” by Battara (1755), in which a special chapter treats of the usefulness and injuriousness of fungi. The close systematic description of the different genera and species begins with Linnaeus’ “Systema Naturae” (1735), the ‘““Methodus sexualis,” the “Genera plantarum,” the “Corollarium generum” and the “Philosophia botanica.” The third edition of this book, published in 1790 by Willdenow, contains an exact list of all botanists up to 1788. The work also mentions a number of diseases (Fames, Polysarchia, Cancer, etc.). On page 245 of the present edition by Wuldenow, are found the following remarks on parasitic diseases :—“Ervsiphe Th. est Mucor albus, capitulis, fuscis ses- silibus, quo folia asperguntur, frequens in Humulo, Lamio. Acere” etc. “Rubigo est pulvis ferrugineus, foliis subtus adspersus, frequens in Alche- milla, Rubo saxatili .’ “Ustilago, cum fructus loco seminum fari- nam nigram proferunt. Ustilago Horde C. B., Ustilago Avenae C. B.” ... Then follow notes on Ergot, galls and other malformations, changes in color etc. It is of importance to pathology that this exact systematist can not sup- press the fact that really no two individuals resemble one another and that climate as well as soil constantly act in a modifying way on the organism. It is stated in fact in the Philosophia botanica, “Varietates tot sunt quot differ- entes plantae ex ejusdem speciei semina sunt productae. Varietas est planta mutata a causa accidentali: climate, solo, calore, ventis etc.; reducitur itaque in solo mutata.” . . . . Scopoli’s book “Dissertationes ad scientam naturalem pertinentes” (1772) treats especially of subterranean plants. In 1780 the publication of Bulliard’s “Herbier de la France” was begun in Paris, in which the different genera are illustrated on 6co colored plates, (among others Mucor, Trichia, Sphaerocarpus, Nidularia, Hypoxylon). After 1 Anleitung zum Studium der Mykologie. 54 Batch’s ‘““Elenchus fungorum” had appeared in 1783 in Jena and, between 1788 to 1791, Bolton’s “Historia fungorum, circa Halifax sponte nascentium,” in which only Linnean genera are described, there was published in 1790 in Liineburg Tode’s valuable work which abounds in personal observations, “Fungi mecklenburgenses selecti.”’ The extremely careful illustrations include among others, the genera Acrospermum, Stilbum, Ascophora, Tubercularia, Helotium, Volutella, Hysterium, Vermicularia, Pilobolus which we now find among the excitors of disease. A. v. Humboldt, in his “Florae fribergensis specimen” (1793) has also described a considerable number of genera. But all these works, nevertheless, are to be considered only “contribu- tions.” A comprehensive methodical classification was first given by Per- soon’s “Synopsis methodica” (Godttigen 1801), for long a standard. There appeared in England, from 1797 to 1809, a work by James Sowerby con- taining 439 plates of valuable illustrations with the title “Colored Figures of English Fungi or Mushrooms.” Mycologists now tended more and more toward the study of the mi- croscopic fungous forms even if the optical instruments of the time did not make possible more exact observations. This applies first of all to Linck’s “Observationes in Ordines plantarum naturales” published in the “Schriften naturforschender Freunde zu Berlin” (3. Jahregang 1809-1810) and the illustrated work by Nees v. Esenbeck, abounding in copies from earlier books, “System der Pilze und Schwamme,” Wurzburg 1817, which contains a sum- mary “of the theories of the lower vegetation stages in historical fragments.” Here also are the statements of investigators believing in shontanecous gene- vation. The author himself, if we understand correctly his grandiloquent natural philosophical presentation, considers the parasitic fungi in the lowest possible groups as structures produced from the mother plant itself. Thus he says, for example, of the Entophytes, “Their most peculiar characteristic is that they belong to the overloaded or exhausted life and generally, if not always, develop first under the common covering without any mixture ex- tending over the whole, and originally only in isolated places, formed in- dividually from the life of the whole. The dependence of the infusorial cell on the higher organisms is always shown by its superior position, due to its more or less lengthened stem. The cell grows before it has become free and its elongation on this foundation is the expression of the condition of polar- ity which has been brought about, not suddenly but organically, and which passes over into the cell from the main plant.” Under the genus Cyathus (one of the puff balls) (p. 141) it is said “the whole trunk species which we have described is only a thread of dust originating from the earth itself. The dust of the puff balls begets itself s At this time Elias Fries! classic work was published including all the known varieties of the fungus kingdom with clear diagnoses of genera and species. 1 Systema mycologicum T. I to III. Lundae 1821, Gryphiswaldiae 1829 to 1832— Elenchus Fungorum, Gryph. 1828. 59 The literature now begins to be increased by single works, scientific as well as practical manuals and writings on both agriculture and horticulture which treat of diseases (Tessier, Jager, Hopkirk, the text books of Willde- now, Nees, de Candolle, Wenderoth, Reichenbach, Re and Kieser) to such an extent that we can now emphasize only those publications which deal most fully with the history of pathology. Among these belong primarily F. Unger’s' “Exantheme der Pflanzen” published in 1833 and giving the results of the most industrious and conscientious studies. This physician, living in a small isolated Alpine valley, supplements his observations by many very careful original drawings, true to nature, on which he constructs his theory of disease. “Most plant diseases are located in the juices . . . . The faulty formation and the numerous abnormalities in the chemical process of the nutritive juice as well as similar faults in the more highly active life-sap, are the causes of innumer- able diseases which become evident in a scanty formation of the plant sub- stance, the accumulation of excretory substances, the breaking up of the parenchyma, the changed constitution of the secretions ctc., or by conditions of an opposite character. In every case, most of the quantitatively and quali- tatively changed processes of the vegetative “chylopoese” might be taken as the source of diseases which may be recognized from the change in sub- stance rather than from that of form. The position into which a large number of the plants are transplanted often acts so detrimentally upon them that at least the greater part deserve to be called diseased.” Although, according to this presentation, we must suppose on the whole that Unger would consider diseases as functional and formal variations in the life-history of the organism, he, nevertheless, arrives at the conclusion that disease is something foreign. “For just as the cosmic and elementary is related to the organic, child-like, antitypical, as something parental or typical, in the same way the organism is related to the disease which is nothing else than a second lower organism whose elements already lie hidden in some other higher one.” In this theory lies the continuation of the thought ex- pressed by Batsch on the nature of the parasitic organisms. Unger states that “among the plant diseases least betraying any depen- dence upon the organism attacked and which in their root formations are still so intimately interwoven with this organism, there belong indisputably those forms which we designate by etiolation, dropsy (anasarca), jaundice (icterus ), tympanitis, tabescence(tabes), failure of crops, profluvia and others. These form in fact by far the majority. Greater independence is shown by the vast army of malformations, at the basis of which always lie deficiencies in the amount of sap and therefore a retardation in lower developmental stages. Honey-dew (Saccharogensis diabetica) is more important than these. Its pathological course was first recognized by L. Treviranus and its more universal significance by Dr. H. Schmidt. Mildew is indisputably related to 1 Die Exantheme der Pflanzen und einige mit diesen verwandte Krankheiten der Gewachse. Wein 1833. 56 this disease: the straining toward a more complex organization of the exuded juices is made evident here by organic formations which are missing in honey-dew. These organic formations are still more independent in rust dew (Fuligo vagans). Finally the disease organism appears in the excre- tions and the forms nearly related to them as a peculiar, complete entity. Parasites belong here—the highest among them, such as some kinds of Lor- anthus, seeming to have separated themselves entirely from the mother body.” Unger’s views are also shared by Nees v. Esenbeck and A. Henry? who state in regard to puff balls that “the fungi clearly stand here at the lowest level .’ “They are correctly considered as the ma- terial of disease, as secretions of the higher plants.” “The leaf fungus is formed in general by a coagulation of the juices discharged into the inter- cellular passages.” Theodor Hartig also wrote his work on the red and white rots of the pine under the influence of this theory. In this he confirmed first of all the co-operation of fungi (Nyctomyces)*. He traced the production of these fungi to a decomposition of the cell walls. Of the works which take up general constitutional diseases and scarcely touch upon the fungi, we will name those by Geiger* and _ Luindley* which in all essentials are based upon practical experience. On the cther hand, however, Wiegmann’s® statements are evidently based on microscopic studies and the bearings of chemistry, for example, he states that the pus of the blight, as well as that of canker, contains putric and humic acids, but that that of the blight contains more putric acid. To him both diseases appear non-parasitic in nature and he thinks canker (Caries, Necrosis) always arises from “a stoppage and deterioration of the juices, even if these were never present in excess.” Among the causes mentioned are injuries to the roots, or injuries from frost and unfavorable soil conditions, as, for example, “If the subsoil is moist, sour, stony or other- wise unfertile, or contains swamp ore.” Meanwhile, after Corda’s® great work on fungi had. begun to ap- pear, Meyen’s' “Pflanzenpathologie” was published as a standard, which even now warrants consultation. He divides his material into “External Diseases” and “Internal Diseases.” Among the former, besides the injuries due to man and to animals, the formation of gnarls and galls, he includes also phanerogamic and cryptogamic parasites, of which the Ustilagineae and the Uredineae as well as other fungi are treated in detail, according to 1 Das System der Pilze, Section I. Bonn 1887. 2 Abhandlung iiber die Verwandlung der polycotylen Pflanzenzelle in Pilz und Schwammegebilde und die daraus heryvorgehende sogenannte Faulniss des Holzes. Berlin 18338. 3 Die Krankheiten und Feinde der Obstb’ume. Miinchen 1825. 4 The Theory of Horticulture. London 1840. 5 The Krankheiten und krankhaften Mifsbildungen der Gewichse von Dr. A. F. Wiegmann sen. Braunschweig 1839. 6 Icones Fungorum hucusque cognitorum. Prague 1837 to 1854. 7 Pflanzenpathologie. Lehre von dem kranken Leben und Bilden der Pflanzen. Published after the death of the author by Dr. Gottfr. Nees v. Esenbeck, Berlin 1841. 57 the standpoint of the time. Meyen no longer shares Unger’s view that the parasites as excrement-organisms are the product of a formative development latent in each plant, the disease occurring in a more or less developed form and state of independence according to the constitution and strength of the host-organism. On the contrary, his Plant-Pathology, in the discussion of smut fungi, emphasizes especially that “observations on the production of the smut show most clearly that we have to do here with true entophytes: we will find that some smut species are shown as particular parasitic growths in the interior of the cells of the plants attacked by them and that the smut mass is not to be compared with anima! pus.” The whole title of Meyen’s “Plant Pathology” reatly reads :—‘Hand- buch der Pflanzenpathologie und Pflanzenteratologie’ edited by Dr. Chr. Gottfr. Nees v. Esenbeck. Vol. I, “Plant Pathology.” According to this, a second part, Teratology, was to be expected. Meyen himself intended to work up such a volume, but, according to the Editor, left no material for it. Just as Nees v. Esenbeck was about to undertake this himself, there appeared the “Eléments de Tératologie végétale, au Histoire abrégée des anomalies de lorganisation dans les végétaux; par A. Moquin Tandon, Doct. sciéne. et méd. etc., director du jardin des plantes de Toulouse. Paris 1841.” C. F. Jaeger “Ueber die Missbildungen der Gewachse” (1814) and Thomas Hop- kirk. “Flora Anomala” (1817) should be mentioned as forerunners of this work. We learn from the German translation of Moguin Tandon’s book, that the translator, C. Schauer, was able, as specialist, to call attention to many misunderstandings and errors made by the author, especially in the German citations and to make additions from his own observations. Moquin Tandon says, “By the expression ‘malformations’, ‘monstrosities’ (monstra ) is generally understood innate, more or Jess important and complicated vari- ations from the type of a species, which are disfigurations and oppose the regular course of a functioning by hindering or arresting it.”’ We are better satisfied by de Candolle’s definition (Theor. élément. I. éd. p. 406), by which monstrosity is any disturbance in the economy of a plant, which is followed by a change in organic form and arises from an internal disposition, almost never from a visible cause. Moquin Tandon’s book is still indispensible to every specialist because of its admirable bibliographical references. About this time, the science of infectious diseases received a new im- petus because of the rapid spread of the potato disease which is still worthy of especial attention. It is one of the most dreaded enemies of agriculture, and is described in the text books as potato Phytophthora rot. We owe one of the first publications on this subject to Martius? and from that 1 Pflanzenteratologie. Lehre von dem regelwidrigen Wachsen und Bilden der Pflanzen. By A. Moquin Tandon. Translated and supplemented by Dr. J. C. Schauer. Berlin 1842. 2 Die Kartoffelepidemie der letzten Jahre. Miinchen 1842. 58 time on a flood of publications, proportionate to the very severe injury to national property from these diseases. We will emphasize among these pub- lications only those of Focket, Payen?, Schacht*, Speerschneider*, v. Holle’, Kithn® and de Bary’. (Further bibligraphical references may be found in the detailed discussions of the different diseases). It was natural that a phenomenon, such as the potato epidemic, would necessarily bring fungous diseases into prominence and increase the whole study of mycology. At the same time the economic importance of smut fungi also began to receive greater and greater consideration. Tillet*, Tes- sier®, and Prévost!’, had early studied the smut of grains and at present we have acquired a considerably extended insight into the nature of those dis- eases and also into the means of combatting them from de Bary’s! investi- gations and Brefeld’s studies, extending over many years. The prevalence of smut diseases has led to the development of the sterilization of seed. In the second volume of this work, which treats of parasitic diseases, the overpowering number of mycological works will be mentioned,—we will nere mention only some of the most important ones, treating of fungus families as a whole. Elias Fries’ great work completed in 1832, has already been considered. In 1831 the first part of Wallroths ‘““Kryptogamenflora”’’* appeared and in 1833 the second part. In this book the cryptogams were worked up by Math. Joc. Bluff and Carl Ant. Fingerhuth. In 1842 Rabenhorst’s “Kryptogamenflora”!® began and in 1851 Bonorden’s “Hand- buch der Mykologie’!*, which has proved to be very useful because of its cuts of microscopic fungus forms, although these had been sufficiently considered in the illustrations of Schaffer, Persoon, Greville, Sowerby, Sturm, Krombholz and Nees sen. To be sure Corda’s “Icones fungorum” had already been published and his “Anleitung zum Studium der Mykologie’!® which is provided with very small drawings; leaving the peculiarity of his classification out of the question, however, Corda limit- ed himself to the easily visible developmental stages, while Bonorden sought to determine the tissue structure. This author, in opposition to Unger, em- phasized the fact that parasitic fungi are unquestionably independent organ- 1 Die Krankheit der Kartoffeln im Jahre 1845. Bremen 1846. 2 Les maladies des pommes de terre, des betteraves, des bles et des vignes. Paris 1853. 3Schacht, Bericht tiber die Kartofflépflanze und deren Krankheiten. Berlin 1854. 4 Das Faulen der Kartoffelknollen. Flora 1857. .Bot. Z. 1857. 5 Ueber den Kartoffelpilz. Bot. Zeit. 1858. 6 Die Krankheiten der Kulturgewichse, ihre Ursachen und Verhtitung. Berlin 7 Die Kartoffelkrankheit. Leipzig 1861. 8 Dissert. sur la cause qui corrompt les graines de blé, 1755. 9 Traite des maladies des graines, 1783. 10 Mémoire sur la cause de la carie des blés, 1807. 11 Untersuchungen iiber die Brandpilze. Berlin 1853. 12 Flora cryptogamica Germaniae auctore Ferd. Guil. Wallrothio, Med. et Chir. Doctore ete. Norimbergae 1831-33. 18 Kryptogamenflora von Deutschland, Vol. I., Leipzig 1844. 2nd Edition. I-VII. 1884-1908. : 14 Handbuch der Allgemeinen Mykologie ete. with 12 plates. Stuttgart 1851. 15 Anleitung zum Studium der Mykologie nebst kritischer Beschreibung aller bekannten Gattungen. Prag 1842. a) isms, but maintained that “it is the stomata which take up the spores and bring them to development in the air cavities connected with them.” He said that algae, lichens and mosses which have no stomata and, for the same rea- son, young branches and twigs are free from parasites. He expresses his point of view in regard to the action of parasites, as follows:—‘“That they first cause an hypertrophy and degeneration of the parts heavily infested with them but when isolated they do not disturb the growth of the leaves.” Ac- cording to him, dry weather is essentially propitious for the spread of the parasites, “because it favors the scattering of the spores. On this ac- count Caeoma and Phragmidium are never found more abundant than in dry summers, as also the Caeoma cerealium, the yellow corn smut so in- jurious to seeds, which caused such great damage in 1846.” Kuhn in his “Krankheiten der Kulturgewachse” (Berlin 1858) attained, in the happiest manner, the end for which Meyen strove, viz. of uniting scientific studies with practical experience in the treatment of plant diseases. However necessary and important purely scientific investigations may always be in phytopathology, yet they achieve their full significance only by being tested in practical agriculture. Only by practical work can it be decided whether the conditions of nature and of the laboratory favor the develop- ment of the same parasites or other excitors of disease. So it is necessary to build phytopathology upon a practical knowledge of agriculture and horti- culture. The differences which have developed in medicine between the scientific investigator and the practicing physician must also necessarily arise in the science of plant diseases. We term this practical side,—the pro- fession of “Plant Protection.” Mycological studies are a part of the indispensible fundamentals of plant protection and for this reason, we have given them the greatest possible at- tention in the history of phytopathology. Continuing with this in view we will name first of all the masterly plates in the book by the brothers Tulasne “Selecta fungorum carpologia,” Paris. The English work by Berkeley “Outlines of British Fungology,’ London 1860, is most welcome as a col- lective work although it is mostly provided witn very rough illustrations. De Bary’s works continue to be of especial value. His results in this con- nection may be found summarized in the “Morphologie und Physiologie der Pilze, Flechten und Myxomyceten,”’ Leipzig 1866. We owe further important investigations to O. Brefeld, in his “Unter- suchungen tiber die Schimmelpilze,” Leipzig 1871, 1872 and following, and Cohn for his “Biologische Mitteilungen tber Bakterien,” Schlesische Ges. f. vaterl. Kultur, 1873, as well as for his “Untersuchungen tber Bakterien” 1875 and for other studies contained in his “Beitrage zur Biologie der Pflan- zen.” In these Cohn has successfully advanced the history of the develop- ment of Bacteria. His pupil, Zopf, essentially extended these studies in the work “Die Spaltpilze,” Breslau (3rd Ed. 1885). Among the summaries of this time mention should be made of Eidam “Der gegenwartige Standpunkt der Mykologie mit Rticksicht auf die Lehre von den Infektionskrankheiten,” 60 Berlin (2nd Ed. 1872) and further Winter, “Die Pilze Deutschlands, Oester- reichs und der Schweiz,’ Leipzig 1884. Rabenhorst’s “Kryptogamenflora” brings the subject to completion. The most comprehensive systematic summary of all the fungi is con- tained in P. A. Saccardo’s “Sylloge Fungorum.” The eleventh volume with a “Supplementum universale” was published in Pavia in 1895. Sydow’s “In- dex universalis et locupletissimus nominum plantarum hospitium speciarum- que omnium fungorum,” Berolini, Fratres Borntraeger 1898, carries the work further. This book contains all the fungi known up to 1897. Further sup- plemental volumes (XIV-XVI) were published in 1899-1902 and others are to follow. Saccardo supplemented this great work on fungi with 1500 illus- trations which were published from 1877-1886 under the title “Fungi italici autographice delineati,” Patavii. In place of the sketchy drawings of this work, A. N. Berlese began to publish a series of most careful, colored illustrations under the title, “Icones fungorum ad usum Sylloges Saccardianae adcommodatae,” Abellini. The Sphaeriaceae Hyalophragmiae were furnished in parts 1V-V, which appeared in 1894. To our knowledge, the author had not finished the work at the time ef his untimely death. In the same way, we find colored illustrations in Cooke’s “Mycographia seu Icones fungorum,” London :—the first part ap- peared in 1879 with cuts of the discomycetes. The publications on fungi and bacteria now become so numerous that they are no longer to be mastered and make any further citations impossible. This compels us to refer to the “Botanischer Jahresbericht’ which has been appearing since 1873. It is natural that Teratology has also developed further since Moquin Tandon. Among the works treating of the material as a whole, emphasis should be laid on M. Master’s “Vegetable Teratology,’ London 1869 and O. Penzig, ““Pflanzenteratologie,” systematisch geordnet, Genua 1890-94, which may be designated as the most complete book of reference on this subject. Because of limited space we must forego all further citations of my- cological literature. The reader will find the desired supplementary infor- mation in the second volume of this work. However, a brief reference to the numerous publications descriptive of fresh and herbarium material must be made in a presentation of the history of the development of this science. Among the herbaria which pay especial attention to plant diseases, there should be mentioned here, F. v. Thiimen, “Herbarium mycologicum oeco- nomicum,” Teplitz, 1873-79, Rabenhorst, “Fungi europaei exsiccati” con- tinued by Winter and Patzschke; L. Fuckel, “Fungi rhenani exsiccati,” 2nd Edition 1874; Jak. Eriksson, “Fungi parasitici scandinavici,’ Stockholm 1882-1895 ; G. Briosi et F. Cavara, “J funghi parassiti delle piante coltivate ed utili essicati, delineati e descritti,” Pavia, fasc. I-XII (1897) ; W. Krieger, “Schadliche Pilze unserer Kulturgewachse,” fasc. I. 1896; A. B. Seymour and F. S. Earle, “Economic Fungi, Cambridge. Following in close connec- tion with Rehm’s ascomycete collection, published many years ago, are many 61 Herbaria representing the general fungus flora of different countries, as, for example, those by Saccardo, Sydow, Vestergren, J. B. Ellis, Jaap, Bubak and Kabat, Posch etc. Although the science of plant diseases would refer to teratological phe- nomena only when it can prove, or at least suppose as a cause of the indi- vidual phenomena, some definite disturbance of nutritive or structural con- ditions, it has been forced to take the animal world more and more thor- oughly into consideration. The following publications summarize the entire material or the larger part of it, are comprehensive and should be used for further study :—Ratzeburg, “Die Forstinsekten,” Berlin 1839-1844 and “Die Waldverderbnis,” Berlin 1866-1868; A Gerstacker, “Handbuch der Zoolo- gie,” Vol. II., Arthropoden, Leipzig 1863; E. L. Taschenberg, “Entomo- gie fiir Gartner und Gartenfreunde,” Leipzig 1871, and “Die der Landwirt- schaft schadlichen Insekten und Wiirmer,” Leipzig 1865. Further Nordlinger, “Die kleinen Feinde der Landwirtschaft,” Stuttgart 1869. Kaltenbach, “Die Pflanzenfeinde aus der Klasse der Insekten,” Stuttgart 1874, and Ritzema Bos, “Tierische Schadlinge und Niitzlinge,” Berlin 1891. The “Handbook of the Destructive Insects,” by C. French, published in Melbourne in 1891 by order of the Department of Agriculture of Victoria, is less rich in material but better adapted to the practical needs of the layman, because of its colored plates. In the same year H. R. v. Schlechtendal published a smaller special work on gall formations——‘‘Die Gallbildungen (Zoocecidien) der deutschen Gefasspflanzen,” Zwickau 1891. Ten years later G. Darboux and C. Houard published a comprehensive systematic work,—‘Catalogue systeématique des Zoocécidies de 1’Europe et du Bassin méditerranéen,” Paris 19oT. The “Forstliche Zoologie”’ by K. Echstein, Berlin 1897, may be especially recommended because of many careful original drawings. The popular writings of Hv. Schilling are especially useful for horticulture ; we recommend “Die Schadlinge des Obst-und Weinbaues,” “Die Schadlinge des Gemiisebaues,” Frankfort a. O. 1898 and the “Practischer Ungezieferk- alender,” Frankfurt a. O. 1902. The “Schutz der Obsthaume gegen feind- liche Tiere” by E. L. Taschenberg (ard Edition by O. Taschenberg), Stutt- gart 1901, is also well adapted for practical needs. As the science of plant protection develops there is a corresponding at- tempt to produce reference books treating some of the most important culti- vated plants, such as Eisbein “Die kleinen Feinde des Ritbenbaues, 1882, with carefully prepared colored plates and Emile Lucet “Les insectes nuisibles aux Rosiers sauvages et cultivés en France,” Paris 1898, with numerous plates in black and white. Most complete is the work being done in the United States in protecting plants from these animal enemies. The Zoolo- gists in the several State Experiment Stations and the “Bureau of Entomol- cgy” of the Federal Department of Agriculture in Washington, are advanc- ing rapidly the study of the enemies of cultivated plants, by new investiga- 62 tions and by the distribution of popular treatises. More detailed references to zoological literature are to be found in the third volume of this manual. The number of text-books and manuals of phvtopathology has grad- ually been increased since the publication of Ktihn’s “Krankheiten der Kul- rere Ts ” as the understanding of the national economic significance of phytopathology has increased. First of all comes Orstedt’s “Om Sygdomme hos Planterne, som foraarsages af Snylteswampe, navnlig om Rust og Brand,” Kjobenhavn 1863. This work was followed in 1865 by later reports on the alternation of hosts by rust fungi (Gymnosporangium Sabinae). About this time Hallier’s' book appeared which must be given more especial attention in a history of plant diseases because of the author’s stand- toint. Hallier’s views leading to sharp literary disagreements, especially with de Bary, may be found in extenso in his later writings*. In his “Pestkrankheiten der Kulturgewachse,” he gives a list of investigations on the Peronosporeae and believes he has permanently established by these the correctness of his “Plastiden Theory.” At the time of the “Cholera meeting” in Weimar (1868), Hallier first made the assertion that the forms, summarized as Fission fungi (Schizomycetes) by Nageli were net indepen- cent organisms, but represent the products of the plasma of different groups of filament fungi. Hence Nageli’s family of the Fission fungi should be stricken out of the classification and infectious diseases as a whole be traced back to the action of such plasma-products (“Plastiden’’). “In order there- fore to discover the origin of infectious diseases, it is necessary in every case to ascertain by investigation which definite fungus produces the cells of con- tagion from its plasma (bacteria, micrococcus etc.) and in what way this takes place.” In regard to the potato disease produced by Phytophthora, he does not question whether this fungus is the cause of the disease, but only whether it may cause it less directly than would bacteria. “I have proved first and foremost that the bacteria which are the absolute cause of the pota- to pest, are produced by the “Plastiden” of the Phytephthora and that these, when once formed, are absolutely equal to the production of the plague; that there is no further need of the mycelium and buds of the Phytophthora.” His numerous experiments ultimately led him to the view that, in all in- fectious diseases, human, animal and vegetable, three main points undoubted- ly come under consideration: (1) The absolute cause; (2) External or general furtherance (chance causes or predisposition) ; (3) Personal fur- therance (susceptibility of the diseased individual). Sorauer in the first edition of his “Manual of Plant Diseases,” Berlin, Paul Parey, 1874, first introduced into plant pathology the view, that in all diseases not only the direct cause but also the earlier preparatory stages and, in parasitic attacks, the accessory conditions favoring the development of the parasites, including the disposition of the host organism, should be taken 1 Phytopathologie. Die Krankheiten der Kulturgewachse. Leipzig 1868. 2 Die Plastiden der niederen Pflanzen. Leipzig 1895.—Die Pestkrankheiten (Infektionskrankheiten) der Kulturgewachse. Stuttgart 1895. 63 into consideration. This statement was definitely established in the second edition (1886) and in an abstract written especially for the practical agri- culturalist, “Die Schaden der einheimischen Kulturpflanzen,’ 1888. The delayed acceptance of these ideas is shown by the text-books which im- mediately followed. Of these the one especially valuable because of its num- erous personal investigations is “Lehrbuch der Baumkrankheiten”’ by Robert Hartig, Berlin 1882 (2nd Ed. 1889). The third edition, in which the author rather unreservedly acknowledges a predisposition and differentiates local, temporal, individual, acquired and morbid predisposition, appeared in 1900 with the title “Lehrbuch der Pflanzenkrankeiten’”—Berlin, Julius Springer. A study of the phenomena of the decomposition of wood, with the title “Wichtige Krankheiten der Waldbaume,” Berlin 1874, is an intro- ductory work for this textbook. Sorauer’s Manual was followed first by Frank’s detailed elaboration, “Die Krankheiten der Pflanzen,” Breslau 1880 (2nd Ed. 1895). The “Lehrbuch des Forstschutzes” by H. Nordlinger, Berlin 1884, is devoted especially to cultivated forest plants. Solla’s book, ‘Note di Fitopathologia,” Firenze 1888, is more comprehensive and contains an atlas. This was pre- ceded in Norway in 1887 by Brunchorst’s “De vigtigste Plantesydomme.”’ To this decennium belongs also a number of noteworthy articles by Jensen, among which (according to Rostrup) is: “Kartoffelsygen kan overvindes ved en let udforlig Dyrkningsmaade,”’ Kjobenhayn 1882. While up to this time scientists had classified diseases according to their proved or assumed causes, Kirchner in 1890 published “Die Krankheiten und Beschadigungen unserer landwirtschaiftlichen Kulturpflanzen,” Stuttgart, arranged especially for practical use. The diseases are listed here ac- cording to the different cultivated host plants and described according to their visible habit of growth. Systematic scientific supplements are collected at the end of the book. In accordance with the line of investigation of this author there appeared in 1895 a richly illustrated book treating of parasitic diseases only,—‘‘Pflanzenkrankheiten, durch kryptogame Parasiten verur- sacht,” by Karl, Freiherr v. Tubeuf, Berlin, Julius Springer. Parastism was here developed as a form of symbiosis and thereby referred to an “internal and an external” predisposition for becoming diseased. The internal predispo- sition depends on “the energetic condition of the living protoplasm of the host cell,” while the external one “is determined especially by anatomical condi- tions.” In the same year Prillieux published a two volume work abounding in personal investigations, “Maladies des plantes agricoles et des arbres fruitiers et forestiers,” Paris. This, the most comprehensive work in French on the subject, describes only parasitic diseases. They are treated scientifically and yet the practical side receives attention in so far as means for combatting disease are considered. An unlooked-for advance in the studies on bacteria resulting from their many-sided economic significance, made a revision and enlargement of de Bary’s “Vorlesungen iiber Bakterien,” necessary. In 1goo, in Leipsic, Mig- 64 ula, enabled by his own work, produced a new edition to which he added exact bibligraphical citations. Meanwhile, as the necessity of familiarizing practical circles with the nature of plant diseases became increasingly more evident, it led the large German Agricultural Society to undertake the issuing of suitable publica- tions. In 1892 appeared the first edition of Sorauer’s ‘‘Pflanzenschutz,” and in 1896 its second edition, revised by A. B. Frank and P. Sorauer. The authors strived for the briefest presentation possible, classified the diseases according to the host plants and treated each disease under three headings :— Recognition, Production and Control. The text was supp!emented by num- erous illustrations on colored plates. In the same way, Frank published a more detailed work with the title:—“‘Kampfbuch gegen die Schadlinge un- serer Feldfrtichte,” Berlin 1897 and Sorauer one, entitled, “Schutz der Obst- baume gegen Krankheiten,” Stuttgart 1900, provided with numerous figures im the text. Of books in foreign languages, there appeared about this time, W. Kruger’s treatise on the diseases of sugar cane in the “Bericht der Versuchs- station fiir Zuckerrohr in West-Java, Kagok-Tegal,” published in 1896. This treatise took up thoroughly the Sereh disease with a conscientious use of the pertinent literature. Subsequent to it appeared in Leyden in 1898, H. Wak- ker and G. Went’s “De ziekten vom het suikerriet op fava,” which should be recommended because of its many plates. Delacroix treats the diseases of coffee especially in his book, “Les mala- diesyjet les ennemis des Caféiers,’ Paris (2nd Ed: 1900). Two years later D. McAlpine, in Melbourne, published “Fungus diseases of stone-fruit trees in Australia.” The last named publication considered cultivated plants only. The need of a comprehensive treatment of the whole field of diseases was shown and after a long interval, a response, the manual, ‘“‘Plantepatologi” Haandbog i Laeren om plantesygdomme af E. Rostrup, was published at Kj6benhavn in 1902. This book, elegantly gotten up and attractive because of its many careful original drawings, lays emphasis on fungous diseases, the known number of which the author by his many personal observations, published after 1871, had increased. To facilitate the consultation and discovery of the different diseases, a list was placed at the end of the book, arranged accord-_ ing to the host plants. In 1903 the Japanese published ‘a book which should be considered as a significant cultural advance. We have a German translation of this entitled “Lehrbuch der Pflanzenkrankheiten in Japan,’ Ein Handbuch fur Land- und Forstwirte, Gartner und Botaniker. Von Arata Ideta (3rd Ed.) Tokio 1903). This work is provided with a glossary of technical terms in German, English and Japanese and contains 13 plates and 144 text figures carried out in fine line-drawings (mostly after German authors). In a science like phytopathology, in which the results of all investiga- tions are intended for use in practical industry, the need is at once felt of 65 making the forms and causes of disease more easily comprehended by the layman, by means of colored illustrations. On this account, without regard to special works on fungi, we often find the text supplemented by colored pictures of the habit of growth. An attempt to present the most important diseases in the form of a portfolio with short descriptions of the figures on the plates could be undertaken only after a more widely extended under- standing of the importance of this branch of knowledge had insured a suf- ficient number of purchasers. Accordingly, since 1886, Paul Parey of Berlin has issued Sorauer’s “Atlas der Pflanzenkrankheiten,” of which six folio numbers have already been published. The especial care used here, in hav- ing the different colors true to nature, made the price such that the publica- tion had a smaller circulation among practical workers than in scientific in- stitutes, and accordingly a need was gradually shown for the publication of a less expensive work. This appeared under the title, “Atlas der Krankhei- ten und Beschadigungen unserer landwirtschaftlichen Kulturpflanzen,” edited by O. Kirchner and H. Boltshauser and published by Ulmer, Stutt- gart. This is now completed in six numbers. Meanwhile the Deutsche Landwirtschafts-Gesellschaft discovered, by its publication of “Pflanzen- schultz,” that at present the time is ripe for the extension of the knowledge of diseases among practical agriculturalists, and that it can be carried through most successfully by such brief guides. The society published the third edition in 1904, revised by Sorauer and Rorig, with seven carefully pre- pared plates. The “Atlas des Conférences de Pathologie végetale” by Georges Delacroix, Paris 1901, should be mentioned as of special service to the systematic study of diseases. This gives the most important diseases of cultivated plants in 56 plates in black and white. In 1902 Delacroix pub- lished by order of the French Agricultural Department a small work, “Mala- dies des plantes cultivées,” Paris, which was written chiefly for general use and is supplemental to the above. The most significant scientific advance is the publication of monographs covering the separate fields of disease. This method has also appealed especially to recent workers in plant pathology. In accordance with the im- portance of the disease, thorough study has been devoted to the rust fungi, especially of grain. In 1894-95 the German edition of a 463-page work by Jakob Eriksson and Ernst Henning was published—‘‘Die Getreideroste, ihre Geschichte und Natur, sowie Mafsregeln gegen dieselben,” Stockholm. This work, which attracted much attention, appeared as a volume of the “Meddelanden fran Kongl. Landtbruks-Akademiens Experimental falt,” and its 13 colored plates show clearly the diseases due to grain rusts. It proves the specialization of parasitism in the fungi of grain rusts. Besides this, the work takes up the discussion of the determinative factors and tests the posi- tion, the physical and chemical constitution of the soil, the previous cropping, time of seeding etc. In 1904, H. Klebahn published an equally careful work with a larger field and based on his personal studies, entitled:—‘Die wirtswechselnden 66 Rostpilze,” Versuch einer Gesamtdarstellung ihrer biologischen Verhaltnisse. 3erlin 1904. Gebr. Borntrager. A chronological table gives a list of the heteroecious rust fungi discovered since de Bary’s first investigations made in 1864 with Puccima graminis. The text treats in the greatest detail and with pertinent bibliographical references, gradation of differences, limi- tation of species, specialization and theory of descent, susceptibility and transmission of rust diseases in seed. With this is also discussed thoroughly the mycoplasm theory brought forward about 1897 by Eriksson. This point has already been discussed (see p. 34). Eriksson’s latest studies appeared in 1904 in the publications of the Schwed. Akad. d. Wissensch. under the title: “Das Vegetative Leben der Getreiderostpilze.” A further important advance in the creation of scientific foundations is shown in the “Pathologische Pflanzenanatomie” by Ernst Kiister, Jena 1903, published by Gustav Fischer. Guided by the discovery that a distinct sepa- ration of the natural forms into normal or abnormal can not be carried out, Kuster tests the phenomena from the physiological point of view, i.e. as to the functional efficiency of the tissues. “The tissues are prevented from de- veloping into functionally efficient, i.e. normal tissues, by influences of some kind or functionally efficient tissues undergo subsequent changes in which they forfeit entirely or partially their functional ability, or new tissues are produced in the plant body of such a nature that its diseased and deformed organs either accomplish nothing for the organism as a whole, or less than those which we designate as normal.” We find in this work a successful attempt at presenting the developmental mechanics of the vegetable organism. A periodical literature developed along with the attempts to organize the protection of plants. The guiding principle was the practical question, how the spread of disease and the enemies of cultivated plants may best be prevented and how their direct control can be most advantageously accom- plished. This question was considered more closely first in the United States of North America, since in 1887 stations were formed by the Department of Agriculture for the study of phytopathology and of insects. These most active institutes and experiment stations first of all issued annual reports and then later special publications of scientific investigations. The report of 1889" gives a closer insight into the organization of the service. We learn from it that the Phytopathological Division published its investigations in a definite periodical “The Journal of Mycology” and also distributed pop- ular bulletins of some of the most important diseases. Correspondence con- sisting of replies to queries consumes much of the activity of these stations. For example, in 1889 the questions sent by practical agriculturalists de- manded 2500 replies. These scientists desire chiefly to test results of lab- 1 Report of the chief of the Division of Vegetable Pathology for the year 1889. Published by the authority of the Secretary of Agriculture, Washington 1890. 67 oratory studies by field experiments. With the intention of carrying out such practical agricultural experiments, the pathological division has installed cer- tain supervising agents. When the results of such experiments, conducted in the open in different regions, corresponded sufficiently well, general conclus- ions were drawn and the results published as speedily as possible. In Germany the first attempt toward organization was shown at the Agricultural Congress in Vienna in 1890, where Eriksson and Sorauer brought forward a proposition.recommending to the government regulations similar to those already carried out in America. With the intention of work- ing out a special plan and the development of effective activity, an “Inter- nationale phytopathologische Kommission” was formed by representatives of all European agricultural countries and Sorauer, as secretary, was com- missioned to bring out suitable publications. This furnished an incentive for the foundation of the “Zeitschrift fiir Pflanzenkrankheiten” the first annual series of which appeared in 1891. In the same way the interest in establishing experiment stations and similar institutions for the special culti- vation and the protection of plants in different countries, was stimulated and successful. In 1880! Korn-Breslau published in Prussia a very thorough report, “Ueber die Begrundung einer wissenschaftlichen Centralstelle behufs Beobachtung und Tilgung der Feinde der Landwirtschaft aus dem Reiche der Pilze und Insekten.” The Imperial Government should have re- sponded to such stimuli through the German Agricultural Council. In June, 1889, Julius Kiihn, through whose endeavors the experimental station under Tollrung was established in Halle a. S., brought this same subject before the German Agricultural Society and in 1890 the Society established a “special committee for the protection of plants” whose Board of Directors was form- ed by Julius Kithn, A. B. Frank and P. Sorauer. This special committee estab- lished a net-work of information bureaux for practical agriculturalists which covered the whole German Empire, and published successive “Annual Re- ports from the special committee for the protection of plants,”* after Sorauer had begun in 1891 a statistical revision of the rusts of grains. In 1890 the Phytopathological Laboratory at Paris was opened under Prillieux and Delacroix and in Amsterdam on the rrth of April, 1891, the Netherland section of the International Phytopathological Commission was established. This commission called Ritzema Bos to Amsterdam in 1895 as director of the “Phytopathologisches Laboratorium Willie Commelin Scholten.” In this year, at the instigation of the Holland Phytopathological Association and of the Phytopathological Division of the Botanical Society Dodonaea, the “Tijdschrift over plantenziekten,” edited by J. Ritzema Bos and G. Staes was published. Meanwhile, an experimental station was found- ed at the Pasteur Institute for the purpose of combatting injurious animals by means of contagious diseases. In 1894 this was placed under the direction of Metschnikoff. As director of the ‘““Experimentalfaltet’” at Albano, near Stockholm, Eriksson was untiringly active. In 1895 he published test ex- 1 Archiv des Deutschen Landwirtschaftsrates, Part 8, p. 307. 2 Jahresberichte des Sonderausschusses fiir Pflanzenschutz,. 68 amples for the special forms of grain rusts after which, in February 1901, the State granted him a fund of 10,000 Kronen because of these studies. The question of rust which is also of the highest significance in Australia led in 1888 to the annual meeting of a Congress of Members of the Austra- lian Colonies which, for a considerable number of years, published an official report, “Rust in wheat Conference.” In Germany, Sorauer’s “Zeitschrift fur Pflanzenkrankheiten” was fol- lowed in 1892 by C. v. Tubeuf’s Forstlich-naturwissenschaftliche Zeit- schrift’” which devoted especial attention to plant diseases. In 1898 the“Kgl. bayrische Station fiir Pflanzenschutz’’ was founded with von Tubeuf as di- rector. Besides this, reports in the collective work, “Just’s botanischer Jah- resbericht,” published since 1873, became much more abundant, since a greater number of periodicals now included the subject of plant diseases in their programs. Among these belongs first of all the “Centralblatt fiir Bak- teriologie, Parasitenkunde und Infektionskrankheiten” issued by Uhlworm and Hansen, as also “Hedwigia,” edited by Hieronymous and P. Hennings, the “Botanische Centralblatt,’ elaborated by Lotsy, also Biedermann’s “Centralblatt fiir Agriculturchemie,”’ edited by Kellner, the “Naturwissen- schaftliche Zeitschift fiir Land-und Forstwirtschaft” by von Tubeuf and L. Hiltner and the “Practische Blatter fiir Pflanzenbau und Pflanzenschutz” by L. Hiltner. We find thorough reports, especially on tropical cultivated plants, in “Tropenpflanzer,” Zeitschrift f. tropische Landwirtschaft, by O. Warburg and F. Wohltmann as well as in its “Beiheften” (supplements) which form the organ of the “Kolonialwirtschaftliches Komitee zu Berlin.” In the German East-African colonies, Zimmermann is especially active in pathological fields as is shown by his “Mitteilungen aus dem biologisch-land- wirtschaftlichen Institute Amani.” In Austria the “Zeitschrift fiir das Land- wirtschaftliche Versuchswesen in Oesterreich” was founded in 1898. In the following year P. Nypels began a series of publications under the title ““Mal- adies des plantes cultivées” Bruxelles. In 1goo, v. Istvanffi published the first volume of the “Annales de l'Institute Central ampélologique Royal Hongrois” as the report of the Central Vineyard Institute which had been placed under his direction. Here also especial attention was paid to diseases. The same is true also of the “Jahresberichte der Kgl. Lehranstalt fiir Obst-,Wein-und Gartenbau” published by Gothe and later by Wortmann in Geisenheim a. Rh. and the annual reports of the ‘““Deutsch-schweizerische Versuchsstation fiir Obst-Wein-und Gartenbau zu Wadensweil,” Ztrich, revised by Muiller- Thurgau. This list of periodicals which in part review German and foreign litera- fure and in part publish original articles, gives an insight into the unusually rapid growth of material which necessarily demands a unified summary in some collective work. Hollrung devoted himself to the working out of such a summary and since 1899 has been publishing a “Jahresbericht tiber die Neuerungen und Leistungen auf dem Gebiete der Pflanzenkrankheiten,” Berlin, publishing house of Paul Parey. 69 Thus the new science of phytopathology has taken to itself the same literary methods which the older branches of knowledge use and which are undisputably necessary for scientific progress. but the practical side of phytopathology, viz., the protection of plants, has also found a desired de- velopment. The idea of establishing special institutions, suggested in 1880 by Korn, actively advocated in 1889 by Kuhn and further developed by Sorauer at the International Agricultural Congresses and in the “Zeitschrift fur Pflanzenkrankheiten” was brought in 1891 to general attention in the Pruss- ian Abgeordnetenhause (Chamber of Deputies) by Schultz-Lupitz in the form of a motion. On the 27th day of April of the same year the “Reich- sanzeiger” gave out that the motion of Schultz-Lupitz had been referred to the Royal State Administration for discussion and at once the Department of Agriculture attempted to test the question in how far the production of plants could be advanced by the enlargement of the scientific institutions sub- ordinate to that purpose. As the question received a more thorough: con- sideration, it became evident that the best interests of the protection of plants could only be had from an Imperial Institution. Such was now formed in connection with the Imperial Board of Health as a “Biologische Abteilung fiir Land-und Forstwirtschaft” and since 1905 this has been an independent institution of the Empire. The department, at present under Aderhold’s di- rection, possesses in Dahlem, besides the proper laboratories, a very expensive experimental field and has published its results at indefinite intervals since 1900. Besides these scientific works the “Biological Division” also publishes popular bulletins and colored posters and in this way promotes the knowledge of the most abundant animal and vegetable agencies injurious to plants. In- formation as to their contro! is also distributed gratis, directly to these workers. Besides the above mentioned imperial institution which now bears the title, “Kais. Biologische Anstalt fiir Land-und Fortswirtschaft,” we find in the different German States many organizations for the furtherance of plant protection, which in part are associated with the already existing high schools and experiment stations and in part are independent establish- ments. Among these, besides the institutions already mentioned at Halle and Geisenheim, there should be named also the Anstalt fiir Pflanzenschutz in Hohenheim, founded in 1902 and now under the direction of Kirchner. We also find in the other European countries an active development of the study of plant diseases, proved by the publications of many institutions. Among these belong the “Bulletin de la Station Agronomique de |’Etat a Gembloux,” Bruxelles (Em. Marchal), and “Travaux de la Station de path- ologie végétale,” by Delacroix, Paris, the “Tijdschrift over Plantenziehten” (Ritzema Bos) already mentioned and the “Landbouwkundig Tijdschrift,” the “Oversigt over Landbrugsplanternes Sygdomme” Kyjobenhavn, in the “Tijdsskrift for Landbrugets Planteavl,’ Kjobenhavn (Rostrup), the “Upp- satser i praktisk Entomologi,’ Stockholm (Lampa). “Beretning om Skadein- sekter og Plantesygdomme,” Kristiania (Schéyen). “Berattelse ofver skad- 70 cinsekters upptradande i Finland” (E. Reuter), in the “Landbruksstyrelsens meddelanden,” Helsingfors, the “Annual report of the consulting botanist” (Carruthers) in the “Journ. Royal Agric. Soc.,” London. It is a matter of fact that countries outside of Europe have not been backward in the endeavor to increase plant protection. This branch of knowledge has been most advanced in North America where the Department of Agriculture at Washington has devoted special attention as well to animal enemies. Besides establishing the “Division of Entomclogy” which, by its valuable investigations, contributes essentially to the knowledge of animal injuries, the organization of meetings of agricultural zoologists is especially noteworthy. In these meetings questions of general significance are dis- cussed. Besides this, many investigators in the Universities and Experiment Stations are working along these lines with gratifying results. Of the latter, we will mention the Agricultural Experiment Station of the State of New York at Ithaca and the New Jersey Agricultural College Experiment Station. Further statements are made in our detailed exposition in which the different bulletins of the institutions for the advance of plant protection are mentioned. 4 Besides the numerous publications of the United States of North Ameri- ca, the magazines of other countries also furnish noteworthy contributions to the knowledge of the diseases of cultivated tropical plants.. Among them belong the ‘““Mededeelingen van het Proefstation voor Suikerriet in West Java,” the reports of the “Proefstation voor Cacao to Salatiga,” Malang, the “Boletim da Agricultura,” S. Paulo, “Boletim del Instituto Fisico-Geograph- ico de Costa Rica,’ “Queensland Agricultural Journal,” “Australian fungi” (McAlpine), in the “Proceed. Linnean Society of New South Wales,” “Ad- ministration Reports, Royal Botanical Gardens,” Ceylon, “Report of the De- partment of Land Records and Agriculture,” Madras, and “The Journal of the College of Science, Imperial University of Tokio,” Japan. We must refer to the “Botaniker-Adressbuch” by J. Dérfler, Vienna, 1902, for the numerous other institutions and individaul investigators. APPENDIX. In the above statements we have mentioned not only the literature on the subject but also given expression to the leading ideas of the different periods in order to show how the science has gradually developed to its present standpoint. To be sure, changes in the points of view on the nature and role of parasitic organisms are not without interest, but no less interest- ing are the references of the various authors to the influence of the stars, 1. e. the atmospheric factors, which may be traced as a red line through all the reports. On this account we have often restated at length the earlier points of view and find a striking agreement with the oldest periods since emphasis is always laid on the dependence upon climatic and soil conditions and in part FAL also upon cultural habits of those phenomena, which we have learned to recognize as parasitic. This idea, which is also the guiding principle in the present book, has led the author to undertake the first experiments for coliecting the Statistics cf Plant Diseases. These experiments which, as already mentioned, were begun with the help of the German Agricultural Society and continued by its “Special Commission for Plant Protection,’ have now found recognition, for the “Kais. Biologische Anstalt fiir Land- und Fortswirtschaft” beginning with 1905 has assumed the collection of statistics of plant diseases. Doubt is often expressed as to the importance of such statistics for our subject and reference made to the fact that our most dangerous diseases are constantly present and the statements of the statisticians concerning the intensity of the attack and the amount of agricultural loss appear to be influenced so individually that all certain positive figures can never be attained. In opposition, it should be emphasized that I did not undertake the collection of statistics in order to obtain precise figures as to the dis- tribution and agricultural effect of the different diseases. (Besides, in this connection, the making of reports will graduaily, with the increased educa- tion of the body of observers, become as exact as it is in all provinces of organic life). The chief undertaking in the collection of statistics lies in the proof of the relations which the different diseases bear to climatic and soil conditions felt locally or universally, as well as to cultural factors. The study of the extreme forms of disease, easily verified, and the determination as to which factors have produced these extreme forms makes up the productive field of the statistics. In these studies lies the future of pathology. However valuable in themselves the observations as to the formal po- sition and the life requirements of the parasitic micro-organisms may be, nevertheless, they form only one link in the chain of investigations and be- come important only in the determination of their relation in nature and in the usual practice of agriculture. And this we can recognize by means of a carefully arranged statistical office showing the conditions governing the in- crease or decrease of diseases. This knowledge leads to the prevention of diseases by means of an ever- developing plant hygiene and plant pathology must develop further in this direction in the future. DETAILED EXPOSITION. SE CON sn: DISEASES DUE TO.UNFAVORABLE SOIL CONDITIONS: GEA TERS i. THE LOCATION, OF AE SOIL, Even if the diseases which are due to an unfavorable location of culti- vated land are better understood by means of the different factors because of which this position becomes injurious to plant growth, we have still con- sidered it necessary to describe in the following section the general conditions due to different locations. We have done so because it.is of special impor- tance to the guiding principle of this manual and to any reference to a pre- disposition to certain diseases which is developed from this location of the soil that it be shown how the material and formal structure of any plant species changes with the condtions of the habitat, how thereby separate func- tions may sometimes be suppressed, sometimes advanced, and -how accord- ingly the different localities impress their definite characteristics on the plants which, on this account, must behave very differently in relation to the differ- ent injurious causes. 1. ELEVATION ABOVE SEACEEYV EL: a. GENERAL CHANGES IN HABITAT IN RELATION TO HERBACEOUS PLANTS. There is no need of discussing further the fact that the temperature al- ways falls with an increase in elevation of any cultivated surface above sea level and that this fall in temperature is a determining factor for limiting vegetation, on which account the time of harvest in mountains must always be later than on lower levels. It is an universally recognized fact that this later harvest brings with it great difficulties in curing the grain and not in- frequently makes necessary special precautions in high mountains, and that despite these precautions there often takes place a blackening of the grain as a result of the beginning of fungous growth. An example with exact figures a 73 iS given by Angot!, according to whose observations the harvest of winter rye in France is delayed on an average about four days, as the elevation increases about 100 meters. Attention should be called, however, te the circumstance that, with increasing height, the air being thinner is less warm so that there- fore it must have an appreciable effect on the development of vegetation. With this should be reckoned conditions of moisture which, aside from the physical constitution of the soil, are different for plants of Alpine regions in lower latitudes than for those from plains in the Arctic zone. Within the same degree of latitude mountains, as colder bodies, will condense more water vapor and thereby bring about more abundant precipitation than takes place on plains. On this account more snow will fail and the warmth needed to melt this greater mass of snow is withdrawn from vegetation. Even after the snow has melted in spring, the plants in the mountains will nevertheless at first be less able to benefit from the sun’s warmth than those on the plains since the inequalities of the upper surface of the soil become effective. A square meter of very broken ground surface has a much greater upper sur- face, divided into many slanting levels, over which the same amount of warmth must be distributed, than has perfectly level land, the different par- ticles of which are raised to a higher temperature. This is the case in moun- tain chains in contrast to level plains. It is evident from these statements that with increased elevation above the sea these processes of weathering and decomposition must be retarded since they are essenttally favored by warmth. It is also evident that such peculiar combinations of vegetative factors will produce characteristic forms, of which the best known feature is short, repressed growth. Such forms of growth are kept constant, first of all, in the seeds. Climatic forms which have become hereditary in this way lave been termed “Oecological variations’’”. If it was said at first that the temperature of the air at higher levels 1s lower, it must also be emphasized, on the other hand, that at higher levels the intensity of the illumination increases and produces accordingly greater soil warmth. On this account climate of the lower and middle latitudes, on ac- count of the greater intensity of light and greater warmth of the soil, would differ favorably from that of those plains in a Polar zone where the tem- perature of the air is the same. The lesser atmospheric pressure in moun- tains must result in an increase of transpiration as stated by Friedal® and the increased supply of light in an increase of the assimilatory activity of the leaf. Consequently the typical mountain plant works more energetically and in this way is explained its shortened vegetative period. According to the observations of Bonnier*, who made experimental gardens on Mt. Blanc and in the Pyrenees, in Alpine climates with a 1 Der Naturforscher, 1883, No. 24. 2 Lebensgeschichte der Bliitenpflanzen Mitteleuropas, Von Kirehner, Loew und Cc. Schréter. Stuttgart, Ulmer 1904. p. 116. : 3 Friedal, Action de la pression totale sur l’assimilation chlorophyllienne. C. rend. 1901. ‘Cit. Bot. Jahresb. 1901. Section I, p. 221. 4 Bonnier, Etude expérimentale de lVinfluence du climat alpin sur la végétation etc. Bull. Soc. Bot. France. Vol. XXXV. 35. 1888. 74 greater number of herbaceous plants, the shoots became shorter, leading to nanism. In specimens from high mountains, the palisade parenchyma is more strongly developed and contains more chlorophyll. Accordingly, the assimilatory work has been increased. If the leaves of the same species from specimens grown on plains and in mountain gardens, are cut off at the same time and tested, the leaves from the high mountains showed a stronger de- velopment of oxygen in an equal length of time for equally large surfaces. It is said that such Alpine characteristics can be artificially bred in plants by packing them in ice at night while leaving them during the day under normal growing conditions’. ; In a later report, Bonnier* calls special attention to the increase in temperature and assimilation which, taking place in Alpine regions, may easily account for the fact that plants from the plains, brought into an Alpine climate, develop relatively greater amounts of sugar, starch, volatile oils, coloring matter, alkaloids and other products of chorophyll activity. How greatly this specific climatic character immediately influences the mode of development of any plant species is shown by the well-known ex- periments on structure carried on from 1875 to 1880 by Kerner v. Marilaun* with seeds taken from the same parent plant which had been grown with precaution against cross-fertilization. Part of the seeds were sown in an Alpine experimental garden on the top of Mt. Blaser in the Tyrol (2195 m. elevation), others in the botanical garden in Vienna. The germination of the seed on top of Mt. Blaser took place soon after the melting of the snow which had been 1.5 m. deep, between the 1oth and 25th of June. The germination and growth of the seedlings therefore took place when the sun was highest and the days longest. The seedlings were exposed at once to a temperature which was just as high or perhaps somewhat higher than that furnished the experimental plants in the botanical garden at Vienna, when the March day was twelve hours long. At the end of August and the be- ginning of September blossoms were observed on the plants which had not been killed by the several frosts in June, July and even in August, for ex- ample, on Satureja hortensis, Lepidium sativum, Agrostemma Githago, Cen- taurea Cyanus, Turgenia latifolia etc. The plants grown in the Alpine experimental gardens differed from those in the botanical gardens at Vienna in that they were strikingly shorter and their stems developed a greater number of parts. It was found further that in the Alpine specimens, for instance, Viola arvensis, blossoms developed even from the axis of the third and fourth leaves while at Vienna they came only between the seventh and eighth leaves. The number of blossoms was iewer and the petals, like the leaves, were smaller, as a rule. A part of the 1 Palladin, Onfluence des changements des températures sur la respiration des plantes. Revue gén. de Botanique, 1899, p. 242. 2 Bonnier, Gaston, Influence des hautes altitudes sur les fonctions des végétaux. Compt. rend. de ]’Acad. science. Paris. Vol. CXI. 1890. Cit. Bot. Centralbl, 1891. No. 12. 3 Pflanzenleben. Vol. II, pp. 453 ff. Wein. 1898. 79 annual species from the p!ains which had had sufficient time and warmth to develop seeds were longer lived on the top of Mt. Blaser since in the follow- ing year, new sprouts were developed from the lower part of the stems. An earlier blossoming could also be observed. Corresponding to the fact that the intensity of the sunlight increases with increased elevation, the color of the blossom, depending upon the antho- cyanin, also became more intense. Blossoms, which were white on the plains, had in the Alps petals which were violet underneath. The glumes of grasses, green on the plains, or only pale violet, became dark brownish violet in Al- pine regions because of a more abundant formation of anthocyanin’. The leaves of Sedum acre, S. album and S. hexangulare became purplish red. On the other hand, leaves of Orobus vernus, Valeriana Phu and Viola cucul- lata turned yellow from the excess of light in the Alpine experimental gar- dens while in the valley in shaded places their foliage remains green. The mountainous region affects not only temperatures in the annual seasonal average but especially the moisture content of the atmosphere. Warmth and humidity in their total amount and in their distribution during the seasons together with the supply of light are determinants of growth. As already mentioned, atmospheric moisture influences the amount of light available for the plant, for a humid atmosphere absorbs about five times as many light rays as does a dry atmosphere. Since the absolute content of the air in water vapor decreases with the elevation, less light will be absorbed in the mountains, especially since the rays of light have a shorter distance to traverse in order to reach the earth as compared with regions at sea level. The fact that the absolute vapor con- tent of the air decreases with the elevation is a matter of course for, since the temperature becomes lower and lower, the air must condense its water vapor and give it off in a liquid form. But the relative moisture increases in the mountains which explains why we call a mountain climate damp and rainy. Cloudiness is also relative to the moisture of the air. This increase of the relative moisture and the decrease of temperature form the reasons for the rapid ending of our cultural efforts so far as these concern the obtaining of seeds in mountain regions. We know that the for- mation of blossoms and seed requires an increase of warmth proportionate to the length of the growth period. For this reason we find, as mentioned at the beginning, that grain often does not ripen in the mountains and that therefore clover and other legumes furnish an insufficient amount of seed. Yet another condition must be added to those already mentioned, to which Pax has called attention?, viz., that the insects are only half as num- 1 The theory that anthocyanin is developed for the protection of the plant against too strong sunlight is held by many investigators. Kerner (l.c. Vol. I, p. 508) assumes that, in the reddening of blossoms which appears with a lack of heat, the loss to the blossoms of the directly conducted heat is compensated ‘“‘by the heat obtained from the rays of light by means of the anthocyanin.’ Webelieve we have observed that the red coloring matter indeed does develop abundantly with a lack of heat, but can also set in with an abundance of heat if, in proportion to the heat, an excess of light makes itself felt in the tissues which contain sugar. 2 Das Leben der Alpenflanzen. Zeitschr. d. d.-6str. Alpenvereins 1898, p. 61. 76 erous at an elevation of 2300 m. as on the plains. On this aécount labiate plants play a considerable role on high mountains. Also the increased diffi- culty of insect fertilization is partly equalized by the fact that an asexual reproduction also takes place (Polygonum viviparum, Poa alpina, Saxifraga cernua) ; further, ten-elevenths of all kinds of small bushes and even Viola tricolor, an annual with us, become perennial in the Alps. Besides this, reference should be made to the fact that, with unlimited cultural experiments at high elevations, short-lived mountain varieties are formed which, to be sure, furnish seed in smaller amounts but more satis- factory in quality. This offers greater possibilities of yielding a good har- vest in the mountains and (according to Schiebler)' has the advantage of retaining at lower levels its shortened period of growth and there- fore can be used advantageously in Northern climates. DEVELOPMENT OF THE AERIAL AXIS OF Woopy PLANTS. In contradiction to a widespread opinion, it should be mentioned, that dwarf growth in high mountains is not to be ascribed to the pressure of the snow since we have tree-like forms in those regions where the most snow falls. It is known that the snow covering does not become thicker, the great- er the elevation of the mountain, but with us increases up to perhaps an elevation of 2500 m., that is, only to the upper boundary of the dwarf coni- fers, dwarf alders and the Alpine rose. Higher up the amount of precipi- tation decreases. Spruces, larches and the cembra-pine suffer less from snow pressure when they stand alone or scattered because their elastic, slop- , ing older branches let the accumulated snow slip off more easily when the wind blows. Other trees, like Salix serpyllifolia and Rhamnus pumila, fre- quently escape excessive snow pressure by their growth on steep rocky cliffs from which the snow slides rapidly. However, trees exposed to the full pressure of the snow can scarcely be made to grow closer to the earth be- cause of the burden of the snow or of windy weather. Rather, we may as- sume with Kerner that it is the soil warmth which, in the immediate prox- imity of the earth, affords them the best conditions for existence. In the higher Alpine regions the soil is much warmer than the air which absorbs less sunlight on account of its increasing thinness and its rapidly decreasing water content. The above quoted author cites that, for example, on the top of Mt. Blane (4810 m.) the intensity of the sunlight is 26 per cent. greater than at the level of Paris. On the Pic du Midi (2877 m.) a temperature of 33.8°C. was observed in the soil on which the sun shone while the air showed a temperature of only 10.1°C. This warmth of the soil together with the intensity of the light explains the speedier development and blooming of Alpine plants. Vochting’?, in opposition to Kerner, thinks, on the ground of his observations with Mimulus Tilingii, the young branches of which at a defi- 1 Schiebler, Die Pflanzenwelt Norwegens. Allg. Teil. Christiania 1873. 2 Vé6chting, H., Ueber den Hinflufs niedriger Temperatur auf die Sprofsrichtung. Ber. Deutsch. Bot. Ges. XVI. 1898, p. 37. 77 nite age incline downward in spring when the temperature is lower and straighten up later with increased warmth, that the creeping habit of growth of Alpine plants may be ascribed in part or entirely to the influence of the low temperature. We can not agree with this theory. Rosenthal’ made investigations concerning the mode of growth of trees in Alpine regions. He found that in all the species of wood studied the annual ring is narrower in high countains than in the lowlands. The ec- centricity of the branches is usually very great but the direction of the great- est increase of growth varies. The vascular system, on account of the in- creased evaporation, is more extensively developed. In dicotyledons, a higher percentage of the vascular tissue is obtained by a narrower annual ring; in conifers there is a considerable decrease of the late wood ring. The landslides which continually take place in mountains because of storm conditions displace the trees and thereby change their woody develop- ment. Hartig? pointed out the formation of broad annual rings and so-called “red wood” (wood with short tracheids and strong lignification ) on the underside of the trunks and branches of the spruce as soon as they bend toward the horizontal, while slender annual rings and “strain wood” (long tracheids with weak lignification) are formed on the upper side. Ac- cording to Giovanozzi® this difference in the formation of the wood ring of conifers is made use of in hygrometric measurements by the inhabi- tants of the Piedmontese Alps since the small celled, thin-walled red wood possesses hygroscopic characteristics very different from those of the strain wood. The red wood side of a peeled branch becomes concave in dry air, convex in moist air. ; According to the investigations of Cieslar* the lignin content of spruce wood seems to be less near the upper boundaries of the tree zone than in lower positions. It will be concluded from Cieslar’s’ observations, that the suppressed growth in Alpine forms is hereditary for the immediately following generation, according to which spruces from seeds of trees grown in moun- {ainous regions grow more slowly when cultivated on the plains than do plants raised from seeds of trees from the plains similarly grown. Engler has made the same observation in seeding experiments at the forestry experimen- tal station in Ziirich. From germination experiments with the seeds of spruce, pine and other forest trees, M. Kienitz® concludes that the minimum, optimum and maximum germinating temperatures of spruce seed indigenous to lower regions are higher than for seeds grown in higher positions. 1 Rosenthal, M. Ueber die Ausbildung der Jahresringe an der Grenze des Baum - wuchses in den Alpen. Dissert. Berlin. cit. Bot. Centralbl. 1904. No. 48. 2 Hartig, R., Holzuntersuchungen. Berlin. Springer 1901. 3 Giovanozzi, Sul movimento igroscopico dei rami delle Conifere. Malpighia SVs cit. Bot. Jahreshb: 1901. (Secs IL, p: 191: 4 Cieslar, A., Ueber den Ligningehalt einiger Nadelhélzer. Mitt. a. d. Forstl. Versuchswesen Oesterreichs 1897. Part XXIII. 5 Centralbl. f. d. gesamte Forstwesen, 1894. Vol. 20, p. 145. 6 Kienitz, Vergleichende Keimversuche mit Waldbaumsamen aus klimatisch verschieden gelegenen Orten Mitteleuropas, Ref. Bot. Zeit. 1879. p. 597. 78 In plantations in high altitudes, however, it must further be taken into consideration that the elevation acts differently according as it presents iso- lated peaks or high plateaux. Since the earth’s illumination and radiation have considerable influence on the temperature of the layers of air covering it, vegetation at equal heights is exposed to very diverse temperature fluctu- ations. On the high plateau the decrease of warmth with elevation is less, when the sun shines, than on the mountain peak which stands alone. If, however, the sun disappears and radiation becomes determinative, then the lower air layers above the high plateau also cool off more. Thus the daily fluctuations in temperature are much greater here and the seasonal ones as well. On high plateaux the temperature can fall, even to frost, while the isolated peaks remain protected. The same relation is shown between valley and heights; we have recently observed a number of examples from Italy. Passerini makes! the following observations from the neighborhood of Flor- ence and cites, as an especially good instance, the night of April 19-20, 1903, when the temperature, which on the 15th still showed +18.3°C. sank to —1.1°C. and rose again, nine hours later, to +12.2°C. While the vegetables and grains were not injured, the leaves and blossoms were seriously frozen. Only 50 m. higher the injuries were no longer noticeable. In mountainous regions clouds and mist act as a protection from frosts. Thomas? observed in Thtringen that the young beech foliage did not suffer from frost at heights covered by mists while in the valleys and gorges the leaves were injured. The artificial prevention of frost by the production of smoke has been founded on the peculiarity of mists which prevents the sharp fall in temperature. ADJUSTMENT OF THE Root Bopy or Wocpy PLANTs. In mountains the adaptation of the wood body to the rocky soil and the compensatory structures which appear on this account are especially interest- ing. In the following figure 1, we see the root of an oak which has made its way through a fissure in a rock and by its continued growth in thickness within the split has developed into a flattened, board-like form. After leav- ing the rock, the root resumed its cylindrical form. This example shows first that, despite the pressure which the strong root had withstood for so many years, the ability to conduct water and plastic material has not been interrupted in the board-like part. In the second place, we notice above the board-like flattening the appearance of adventitious reots. Both processes correspond to the phenomena caused by artificial constriction. So far as we have been able to investigate roots which had been flatten- ed in the clefts of rocks, we could observe that the board-like flat places in the root body were produced because the wood rings formed every year were very strongly developed on the sides where they could develop freely, 1 Passerini, Sui danni prodotti alle piante del ghiacciato etc. Bull. Soc. Bot. ital. 1903. p. 308. 2 Thomas, Fr., Scharfe Horizontalgrenze der Frostwirkung an Buchen. Thur. Monatsblatter. April 1904. 79 therefore, in the direction of the split surface, but, on the other hand, they were reduced to a minimum on the side where the roots were pressed against the rock and were finally irrecognizable. On the free side of the wood the vascular bundles developed very abundantly, in some annual rings, in fact, the wood was very broad and provided with a thick bark; on the side of the root pressed against the rock, the wood lacked all vascular formation, was short-celled and formed from wood fibres inclined diagonally instead of Migs de Fig. 2 Roots of Quercus Pedunculata grown between rocks. (After Débner-Nobbe.) running vertically. Finally, differentiation into annual rings could not be observed and only a very slender cork layer is seen lying on the occasionally formed short-celled parenchyma, without any recognizable differentiation into medullary rays. Nevertheless, the cambial activity was not lost in the board-like part of the root as was evident when the pressure ceased, for the flattened part grew normally in its cylindrical form. Anatomical changes in the roots pressed between the rocks approximate so strikingly the results obtained by artificial 8o constriction of the aerial axis, that we can refer in this connection to our subsequent studies in the chapter on “Wounds.” Figure 2 shows a different root, also from Quercus pedunculata, which probably has only been pressed between stones. In meeting with this ob- struction to its growth in length it was bent and, when growing further, be- came flattened. With increasing age the pressed root surface again reached the open and with the removal of the pressure came an increased formation of the wood ring in great luxuriance like callus rolls. The squeezing which the roots had undergone, might have acted like girdling and have produced in this a kind of girdling roll above the place of pressure. (See Girdling in the chapter on “Wounds’’). We can get an idea as to the anatomical conditions in the first stages of such flattening of the root from the investigations of Lopriore’. He observed adventitious roots in the germinating plants of Vicia Faba which were forced to grow under the lateral pressure of cotyledons which had not separated from each other. Within the sphere of pressure these tender roots appeared flattened like ribbons but after leaving the region of pressure, they again became normally cylindrical just as was noticd in the oak roots. In the very young roots of the horse bean (Vicia Faba) Lopriore found that the epidermal cells on the sides not pressed upon by the cotyledons had developed into root hairs. On the compressd sides, however, not only the epidermal cells were tangentially flattened but also the two or four outer layers of the bark were considerably pressed so that they formed a kind of peripheral girdle around the root on these sides, whereby the radial walls of these com- pressed cells seem folded zigzag as in a bellows. The cells subjected to the pressure of the cotyledons were also proved changed materially since their membranes either developed into cork or “together with their lumina were impregnated with a kind of protective gum.” We have already called attention to the fact that in figure 1 several adventitious roots had been formed above the board-like flattening. As may be seen, thé root had made a curve here before entering into the split in the rock and under the influence of this twisting, a new formation of adventitious roots had been started on the free convex side. We perceive in this a result of the stimulus of twisting which Noll? has discussed in detail in his work. It is easy to observe that roots which have become twisted because of a pressure, hindering their growth in length, develop new side roots on the convex side at the point of twisting. In water cultures in glass vessels this phenomenon may be observed when strong roots reach the bottom of the vessel and grow against it. In mountains emergency precautions are met wiih in the flatly growing, younger tree roots if the tip of a rootlet has been lost through injury or from 1 Lopriore, G., Verbinderung infolge des Képtens. Ber. Deutsch. 30t. Ges. Vol. XXII, Part 5, p. 309. 2 Noll, Vergleichende Kulturversuche, Sitzungsber. d. Niederrhein. Ges. f. Na- turkunde. Cit. Bot. Jahresber. 1900. II. p. 304. 81 drying out on the rock. In figure 3a, we see such a compensatory root which has been developed above the dead tip of the main root 4d. The compensatory organ is much stronger and fleshier than the side roots which had been formed earlier. The formation of adventitious roots as a result of the stimulus of twisting or of injury to the root is constantly utilized technically in the cultivation of trees. In tranplanting seed- lings of forest or fruit trees the main root is either twisted spirally in the hole where it is to be planted or it is shortened about a third. A stronger cutting back is not advisable because Big. 3._ Branch of a spruce adventitious roots always develop more weakly root on which a fleshy com- pensatory root has been form- the older the parts of the axis which are ed above the dead tip. (After ‘ Nobbe.) twisted or cut back. b. SprcrtaAL CASES OF DISEASE. RETROGRESSION IN THE CULTIVATION OF THE LARCH. As a striking example of the disadvantages developed by the cultivation of plants from mountain climates when grown on the plains, we might con- sider the often noticed retrogression in larch plantations. Kirchner’ mentions, when describing the life history of this forest tree, that it is a true high mountain tree of the European Alpine and Carpathian systems. The natural area of its distribution extends from Dauphiné through Switzerland, past Vorarlberg, the Bavarian and Salzburger Alps to the Moravian-Silician depression, and to the Carpathians, up to the hilly country of Southern Po- land. The upper limit for the larch is about 2400 m., the lower one in the Alps 423 m., in the Sicilian mountains about 357 m. While it thrives in Scotland, Sweden and Norway, it does not grow very well in Middle and Northern Germany or in France. When growing together the spruce usually forces out the larch except in the highest altitudes. When the spruce grows on dry soil it is shorter than the larch. Of all the indigenous conifers the larch needs the most light. It exceeds all conifers and most deciduous trees in its transpiration. Because it is not sensitive to cold, as shown by its natural habitat, it is much more dependent upon the warmth of the summer 1o make its best growth. It lives in regions where the summer is constantly and uniformly warm, where there is abundant circulation of air and a win- ter’s rest of at least four months with a short spring and a rapid transition from spring to summer. Because its leaves come out extremely early, it makes the most of the very short period of growth. These statements are based on the observations of numerous specialists and may on this account be acknowledged to be thoroughly reliable. We ob- 1 Lebensgeschichte der Bliitenpflanzen Mitteleuropas. Vol. I. Part 2. p. 157. Stuttgart, Ulmer 1904. 82 {ain an insight into its material composition from the works of Weber’. He studied sections of the trunk and the needles of the larch picked in October in the Bavarian Alps, in the Spessart, from the plains of the valley of the Main etc. In spite of the soil differences, the results agreed entirely in regard to the influence of elevation. Weber summarizes these as follows: The organic substance of the needles increases with noteworthy regu- larity with the absolute elevation of the habitat while the content in pure ash decreases. The amount of ash becomes absolutely greater if the larch grows on the plains or in moderately high mountains so that therefore to produce an equal amount of burnable substance, more and more minerals are taken up by the plant, as its cultivation descends into the plains. The most im- portant elements of the ash, potassium and phosphoric acids, show a regular increase in specimens from the plains in contrast to Alpine Larches. In re- gard to the calcium content, the larch of the plains indeed excels, yet the, constitution of the soil seems to be very determinative here; magnesia and sulphuric acid show an insignificant increase, while ferric oxid and silicic acid show a considerable increase. It may be perceived from Weber’s investigations how very greatly the life habits of this high mountain tree and its mineral composition change with its descent to the plains and the question now becomes pertinent as to whether the anatomical structure is not also changed by the entirely differ- ent conditions of life on the plains. Primarily the plains offer strong con- trasts from the most intense heat of summer to the great cold of winter. To this must be added a lengthened spring with the summer-like days which sometimes begin in February, always in March, and the subsequent relapses to cold weather. However, the autumns of the plains may be of decisive sig- nificance when a relatively warm, damp period not infrequently lasts into December and does not permit the cessation of vegetation. One needs think here only of our oaks and apple trees which often enough retain their foliage on the tips of the branches throughout the whole winter. In apple trees, especially in trellis and trained forms, many varieties did not develop any terminal bud in autumn but the last leaf simply remains in the winter in an unformed stage of development. In the larch these long, wet and relatively warm autumns stimulate growth so that after the normal summer end of the annual! ring, a few layers of spring wood are formed, as I have often observed. Therefore in such cases on the plains the beginning of an absolute dormant period (which Kirchner emphasizes as necessary for the normal development of the larch) does not take place and the immediate results will frequently be the loss of the normal or usual resistance to frost. The frost wounds make possible the entrance for all wound parasites which, in the often dense growth of larches on the plains and the moist motionless air, find the most favorable environ- 1 Weber, R., Einflufs des Standortes auf die Zusammensetzung der Asche von Larchen. Allgem. Forst-u. Jagdzeitung 1873, p. 368 1nd in Biedermanns Centralbl. f. Agriculturchemie, 1875, p. 336. 83 ments for their growth and distribution. For this reason the fungus of the so-called larch canker, the Dasyscypha (Peziza) Willkommiui, is so abundant in old larch plantations and the trunks of the young copse wood are covered with lichens. The complaint that the trees in northwest and niiddle Gerrmany and in France, on an average, show no satisfactory growth is explained by these conditions of growth on the plains diametrically opposed to the nature of the tree. This is also the reason for the reaction which has taken place in the usual enthusiasm of foresters for the cultivation of the larch. The comprehension of our mistakes in growing the larch and the in- tenability of the widespread assumption that it can be grown in any place has recently been gathering force in forestry circles. A little paper publish- ed by the First Commissioner of Woods and Forests in Hameln* is of the greatest significance. He observed that the larch canker occurs only where the tree is grown under hindering conditions or is crowded by its neighbors. The point which he makes strongly is “that the sun is the nurse of the larch.” Complete agreement with this discovery has come from an extensive inquiry on the part of the English Dendrological Society contained in Sommerville’s reports?. From this report canker seems to be in- creasing in England on the larch and attacks trees from seven to fifteen years old most easily. Dampness in dense growths favors the disease which occurs less often on altitudes than in hollows. Many practical foresters maintain that the disease is inherited through the seed; and, while Sommer- ville does not share this point of view, he cannot disprove the assumption of an hereditary predisposition. Also the assertion that nurseries spread the disease may not be repudiated entirely. We completely understand such statements also heard frequently in Germany. Such predisposition to sickness lies in the changed mode of growth which is a result of the removal of the tree from mountains to plains, thus destroying its natural immunity. It is reasonable that nurseries with their rapid forcing of the seedlings in manured soils, excusable because of agricultural reasons, increase this weakening of the larch. We find simi- lar conditions also for other conifers; for example, we have examined pine seedlings from nurseries and forestry seed-beds which had begun to suffer from leaf cast, and we have always been able to prove that the beginning of resinosis was present even in the first annual ring. Weber! observed in beech foliage conditions similar to the larch in regard to the difference in the ash content. From investigations from eleven different habitats it was found that the percentage of ash in beech 1 Die Lirche, ihr leichter und sicherer Anbau in Mittel-und Norddeutschland durch die erfolgreiche Bekiimpfung des Lirchenkrebses. Leipzig 1899. 2 Report by Dr. Sommerville on the inquiry conducted by the Society into the disease of the larch. Transact. of the English Arboricultural Society. Vol. III, Part IV. 1893-94. : 3 Weber, Einflufs des Standorts auf den Aschengehalt des Buchenlaubes. Allg. Forst.-u. Jagdzeitung, 1875, p. 221, cit. in Beidermann’s Centralbl. f. Agrikultur- chemie, 1875, Il, p. 325. The percentage of ash content and especially of calcium and silicic acid becomes greater the more slowly the plants grow. 84 foliage from altitudes over 1000 m. above sea level was noticeably less than in that from lower levels. The latter showed, however, in its ash, a smaller amount of potassium, phosphoric acid and sulphuric acid, while the leaves collected in altitudes were proved to be as rich in these substances as the young foliage. The distribution of calcium and silicic acid was the opposite. The size and weight of the average leaves decrease with the elevation. In regard to morphological changes, H. Hoffman’ states that the young sprouts of Salix herbacea and S. reticulata transplanted from high mountains to low levels grow erect instead of lying flat on the soil. When moved from low- lands to high mountains, Solidago Virga aurea becomes an aenemic dwarf. Plantaga alpina is a meagre mountain form of PI. maritima not coming true to seed and with short ears: The length of the ears increased in the second generation on the lowland from 15 to 18 mm.; the leaves became broader and even serated; there were fewer blossoms at this altitude but not smaller. Fiieraciun alpinum developed on the lowland isolated specimens with tall, much branched stems. Aster alpinus in isolated examples developed broad- er leaves. Gnaphalium Leoniopodium, the Edelweiss, loses on the plains its little inflorescences and pubescence. The facts ascertained when the larch was brought from the mountains to the plains seem to be a very sharp warning to consider more carefully the natural requirements of the trees and not to believe, because possibly sup- ported by soil analysis, that each tree must thrive where nutritive substances are abundantly present for it. The great physical conditions, such as venti- lation, illumination and dampness, are determinative factors which, taken under due consideration, preserve the natural immunity of the tree and make superfluous a petty local combatting of the parasites. LAcK OF SUCCESS WITH TROPICAL PLANTATIONS. Like every nation at the beginning of its colonizing period, we must recognize that great loses occur in newly organized tropical plantations. An essential factor for the protection from agricultural injury is to be found, we believe, in the insignificant consideration of the native conditions of growth from which the tropical useful plants originate. In regard to the transplanting of plants from the plains into an altitude, the increase in the relative dampness is of especial importance, next to the decrease in temper- ature. These conditions, for example, quickly place a limit for the culti- vation of grain. According to Fesca’s reports (1. c. p. 42) grain species do not flourish at all in the lower regions of the tropics and the ripening of the grain becomes uncertain in the higher regions. In Java and Ceylon, culti- vation of our species of grains and Leguminoseae with a view to raising seeds becomes doubtful, even at elevations of scarcely 2000 m. On the other hand a smaller difference between the temperatures of win- ter and summer is of great value, especially to tropical plants. Many plants 1 Ruckblick auf meine Variationsversuche, Bot. Z. 1881; p. 431. 85 for which the plains are too warm, thrive better in the more uniform cli- mate of the higher altitudes. Thus Fesca’ mentions that cocoa thrives best at an elevation of about 500 m., Arabian Coffee from 600 to 1200 m., and more, and tea from 1000 to 2000 m. For sugar cane, however, places are necessary in which occur periods of high temperature. Accordingly the cultivation of sugar cane on the sub-tropical plains often reaches even to the 35 parallel of latitude, in Mediterranean regions to the 36 parallel of latitude where the heat temperature for two to three summer months rises above 25°C. The cultivation of sugar cane for factories, however, even in narrow tropical zones is seldom successful higher than 300 m. Indeed it is planted higher up but then only used for the purposes of propagation be- cause of the rapid decrease in the sugar content. At such heights, however, the cane escapes the “sereh disease’ so much feared at present and on this account it has been proposed that the plantations for the sugar be regene- rated by making propagating fields with the proper culturat varieties at high elevations and using as stock the material from these for cultivation on the plains. In other tropical plants the uniformity of the climate is not the decisive factor but the high summer temperatures necessary for the maturing of the fruit. Thus in the narrower tropical zone cocoa palms are found at an alti- tude of 1000 m. but fruit is rarely produced at an elevation of 900 m. In the same way Fesca cites the grape fruit which endures cooler winter tem- peratures but requires a high summer temperature to mature its fruit. On this account its fruit will ripen in Japan between 31 and 32 degrees latitude with an annual mean temperature of 16.5°C. while in Bandoeng on Java at an elevation of 714 m. and an annual temperature of 22.7°C. no fruit ripens. In Japan during the months of July and August the temperature is high enough to ripen the fruit when the monthly mean temperature exceeds 26°C. and even in September is more than 24°C. Such temperatures, however, are not found in Bandoeng. Tea is cultivated advantageously in mountain environments. The tea plant loves abundant moisture, hence is naturally a sub-tropical plant. Tak- ing advantage of the climate of high elevations, it can be grown successfully in the tropics. Thus it is found on Java and Ceylon and in India up to an ele- vation of 2000 m.; the highest plantations in the Himalayas often lie at about 2200 m. Tea from the higher localities is in fact more highly prized. To be sure, greater quantities of leaves are harvested on tropical plains but the quality of the leaves is poorer. It is a mistake to attempt the cultivation of coffee on plains without other shade. Coffee is a tropical plant from high elevations demanding uni- formity of climate. The failure of the crops on the plains may often be traced to the great fluctuations in temperature and moisture much more noticeable there the less the care taken for shading. In the sub-tropical zone 1 Der Pflanzenbau in den Tropen und Subtropen von Pref. Dr. Fesca. Vol. L, Berlin, Siifserott, 1904., p. 41. 86 the summer temperature rises so high and the winter temperature falls so low that growth, which normally should be continued uninterruptedly, ceases tor the time being. Cocoa, however, to a more marked degree, requires a uniform high amount of moisture in the air and soil together with shade and protection from the wind ;—it can scarcely ever become too warm for cocoa. Where it is cultivated, i.e. the narrower tropical zone up to an altitude of 500 m., it developes numerous forms but in all ecological varieties, the same re- quirements are felt as to the climate. Fesca (1. c. p. 240) recommends the consideration of its need of shade especially when the piantations are young. Zehntner! describes a disease affecting these plantations. It appears in the form of brown specks on the bark of two or three year-old sap- plings. After transplantation, the little trunks are more exposed to the wind and the sun and the bark cracks open in different places. 2. SEOPE(OF THE SURFACE OF THE SOM. The slope of the surface becomes a factor which must be considered when the local changes due to the influence of the geographical position are studied. Inclinations of from 1° to 10° and at the most 15° are the most im- portant, for greater inclinations are less suitable for fields. Noll’ has reported an advantageous result of the inclination of the soil. His ex- periments showed that, on rolling land artificially made, an increase of the cultural surface is obtained which in growing lettuce increases the yield about 31 per cent. But even a slight inclination has disadvantages since rainstorms gradually carry off the friable earth leaving the sub-soil behind. The point of the compass toward which the cultural land slopes is also very important. Southerly or southeastern slopes are most subject to dis- aster because of the great weather changes. The higher temperature pre- vailing here forces the growth rapidly in spring; in summer the danger of drying is greater, for the soil is exposed not only to the south winds but also to the dry east and southeast winds and anyway to the cool, damp west winds, but is protected from the north wind. Since, however, dry winds prevail during the spring, i.e. the important vegetative period, the southern declivities dry out very especially and consequently in mountains the southern side is replanted with great difficulty, hence is usually bare. The advantages of the southern exposure are most marked in short cool summers. Because of this declivity short lived plants will often ma- ture their fruit only in such positions; hence these slopes are best used for the cultivation of such plants as are grown on account of their fruits and needing the increased action of warmth and light. A colder exposure, however, would be used to better advantage for such plants as are utilized for foliage and wood. 1 Proefstation voor Cacao te Salatiga. Bull. 4. 2 Noll, Vergleichende Kulturversuche. Cit. Bot. Jahresb. 1900. II, p. 304. 87 When cultivating monocarpic plants, such as vegetables, the injury due to an otherwise suitable exposure, viz., injury from spring frosts, is felt only when the small plants are put out early in spring. There is still greater injury to sensitive polycarpic plants to which our nut trees belong. Here, with a favorable, warm exposure, there is a failure of the harvest, while in the same year nuts are produced abundantly with raw exposures. In the first case the young shoots and blossom buds, forced out earlier by the great- er warmth, are blasted by the night frosts which have not harmed the less developed specimens found in high raw exposures. In garden plantations, when taking advantage of such positions, one attempts to avoid the disadvantages of the spring frosts by holding the plants back artificially. This is done by leaving them covered longer, either by heaping snow on them or by increasing the mats and litter. With fruit trees snow, ice and mulching are heaped about the base in order to keep the soil cool as long as possible and thus retard the root activity. The cold northern exposure is best for meadows and forests. Eastern slopes are unsuitable if the soil is sandy because they dry out more quickly. They are therefore more valuable if the soil is heavy. The reverses true of the damp westerly side. Holzner', comparing a slope at 50° north latitude, inclined about 10° southerly, with another with a 10° northerly in- clination, also took into account the difference in warmth which can be called forth by an inclination of 10°, when all other condtions are assumed to be equal. The sum total of the sun’s rays falling upon this soil bears the proportion on the south and the north slopes of approximately three to two. Wollny’s? experiments on the warming of field lands deserve especial mention. In this work Kerner’s? observations are cited, show- ing how differently the several sides of a hill warm up. These obser- vations follow closely upon the preceding ones. The mean found by three years of observation showed that the exposures may be arranged as follows, decreasing according to their warmth. The warmest exposure was S. W. then followed S., S.E., W., E., N.E., N.W. and N. This scale shows that in reality the different exposures do not act as one would first suppose theoretically. It would seem first of all that with the sun equally high above the meridian the heating would be equally strong and that, therefore, the southeast side would receive the same amount of warmth as the southwest side. Kerner explains that this is not actually the case by stating that in the afternoon the sun at the same height acts more powerfully because the satu- ration of the air with water moisture is lower then than in the morning hours on which account the absorption of the sun’s rays is less in the afternoon. Lornez‘ gives still another reason. On the southwest side, the dew 1 Holzner, Die Beobachtungen iiber die Schttte der Kiefer oder Féhre und die Winterfirbung immergriiner Gewachse. Freising 1877. 2 Wollny, Untersuchungen tiber den Binflufs der Exposition auf die Erwarmuns des Bodens. Forschungen auf dem Gebiete der Agrikulturphysik. Vol. I, p. 263. 3 Kerner, Ueber Wanderungen des Maximums der Bodentemperatur. Zeitschr. d. 6sterr. Ges. f. Meteorologie. Vol. VI, No. 5, pp. 65 ff. 4 Lorenz und Rothe, Lehrbuch der Klimatologie. Wien 1874, p. 306. 88 and moisture from the rain have dried up more than on the south and south- cast; it has previously been warmed to some extent and the same amount of warmth falling on a drier soil correspondingly warms it up more. The monthly mean temperature, however, and in any case the maxi- mum warmth in the different seasons, is more important for plants than is the annual average. In this connection Kerner’s thermometer observations show that only in winter (from November to April) is the maximum soil tem- perature found on the southwest side and that conversely, from May until August, the southeast side shows the greatest warmth, in September and October the south side is the warmest. This shifting of the maximum may undoubtedly be explained by the dry east and southeast winds of midsum- mer which, a similar physica! composition of the soil being assumed, dry the soil more quickly and thereby make it more capable of being warmed up. While Kerner’s investigations were made on a natural hill, consisting of alluvial sand and provided with pretty steep, grass slopes near Innsbruck, Wollny experimented with an artificial hill made of sifted calcareous sandy humus whose surface formed an angle of 15°. Here, therefore, the con- ditions were adapted to a land which could be used agricuiturally. Wollny’s observations confirm first of all those of Kerner, that the max- imum of warmth shifts from southeast in summer to southwest in winter. Further, in general, the sou thern slopes (S.W., S.,S.E.) are exposed to great- er fluctuations in temperature than the northerly slopes which respond to the smallest fluctuations. In another series of experiments ascertaining the temperature of the slopes of beds set at different angles to the compass, com- pared during the warmer season with the temperature on a level field sur- face depressed 15 cm., gave the following results. The south side is the warmest, then follows, as the medium, the level worked surface; then in the third place the east and west sides, while the northern exposure of the bed seems to be the coldest. If now the bed is placed east and west, one long surface lying to the south, the other to the north, these two surfaces show the greatest difference in temperature when vegetation can still be found. Therefore, if the field is to be laid out in plots, it is better to have them run north and south. Cultivation on level surfaces with a lower temperature than on the slope inclined to the south but exceeding that of other exposures is the most advantageous on account of the even, and, on an average, higher warming of the soil. Later experiments’, however, show. the advantages of a position inclined to the south, but these are only evident when the moisture is suffici- ent and constant. In dry weather or irregular precipitation the harvest is smaller. Indeed, in extremely dry weather, the greatest yield is from the northerly side, which otherwise gives the smallest. In fact the yield becomes less as the angle of inclination increases. Then follow the west and east ex- posures. The smallest yield was usually on the south side. 1 Wollny, E., Untersuchumgen tiber die physikal. HBigenschaften des Bodens auf das Produktionsvermégen der Nutzgewiichse. Forsch Geb. d. Agrikluturphysik XX, Parts) L809) po 89 Naturally other conditions also enter into the question; thus, for ex- ample, color also becomes a considerable quantity when the soil is sufficiently damp and has a favorable mechanical form. The darker the earth the more plant growth is favored. Mixed soils give better results than clear peat, sand or loamy soils. ds OOtSTEEP: SLOPES. Soil surfaces of more than 15° to 20° inclination in a small area must be used so far as possible for meadow and grazing land if gardening and vine- vards do not warrant expensive terracing. If the inclination of any surface approximates 45° it is urgently advisable to retain all existing vegetation and to attempt forestration or to complete it with suitable planting. This utilization of surfaces, at such an inclination, is not only the best method but also the best protection of the lower adjacent cultivated land. Such steep slopes, only found in mountains, rarely have a deep loam even when covered with forests. Under such conditions only the thickly matted root systems of the trees can keep off the destructive gullying and washings after heavy rains and from storms after continued drought if the soil con- tains much sand. The moss cushions of forests retain moisture necessary for the further disintegration of the rocks and increase the tendency to form springs; which benefit is felt only on the plains. It is easy to observe, that the pith has become eccentric when the trees are growing on steep declivities. Mer‘, studying firs and spruces of the Vosges, ob- served that, in trees growing on steep cliffs, the annual rings are more strong- ly developed on the side toward the upper incline than on that toward the declivity. This occurs especially at the base of the trunk. On cliffs lying toward the north and east, the firs and spruces were not only taller and stronger but the annual rings of the individual trees varied more markedly in the same points of the compass. If the trees have to grow twisted, the annual rings show a stronger development on the convex side at the points of twisting. Unfortunately our cultivated lands show the sad results of the deforesta- tion of steep slopes. The forest was here the product of consecutive pro- cesses many hundred years old, which probably began with the colonization of lichen encrustations on the naked rock. Through the retention of the products of weathering, these and gradually larger plants began to form a surface soil and with their decomposed bodies furnished the first humus substances, making the soil better and better adapted for the growth of higher plants. Once robbed of this covering of vegetation, the bursts of rain sweep the surface soil downward, exposing the stony sub-soil on the heights and filling up the tilled land on the plains. With greater deforestation of the mountain, the water supply of the mountain streams becomes the more irregular and, with more frequent spring floods in the lowlands, covers them with sand; also in dry summers the streams are without water. 1 Mer, Des causes qui produisent l’excentricité de la moelle dans les Sapins. Compt. Rend. Vol. CVI, 1888, p. 313. 90 Aside from the direct injury of the stones carried down with the mass- es of earth, the chief destruction lies essentially in the covering of the parts of the plants which hitherto had been exposed to the free air. Many plants, liowever, die if they are permanently planted too deep and only those can withstand being covered with soil which possess the ability of readily strik- ing adventitious roots. Among herbacous plants the grasses growing on dunes should be emphasized especially as having this quality (Arundo arenaria L., Elymus arenarius L., etc.) ; our quack grass (Agropyrum repens P. B.) also easily works its way out through a heavy covering. Among trees, the willows and poplars withstand such a covering without great dis- advantage, and especially the (Seekreuzdorn) (Hippophaeé rhamnoides L.), which grows on gravel and sand, is found on the coasts of Germany, France and England, and serves, with its flat lying roots, as a means of retaining the dunes. In opposition to this, the bases of the trunks of many trees, as for example, fruit trees, are very sensitive to deep, heavy soil covering. Also in transplanting trees, or in grading, a change in level covers the base of the trunk, which has been exposed to the air, leads to a weakening and shows phenomena of disease which will be treated of more in detail. In potted plants the Ericas are most sensitive to the smothering of too deep planting. It must be assumed that the cause of death isa lack of oxygen for the roots which have been set too deep and covered by large amounts of earth. Landslides, besides covering the lower lands, expose the roots; which fact deserves attention. So long as the forest remains intact, interwoven roots form a network with such small meshes that the soil is held firm. If, however, holes are torn in this by the hand of man or by storms, so that the plants are uprooted, then the soil begins to push down from the higher places and in fact the more quickly, as the soil is more broken and the wind finds the more access to the torn places. Aside from processes of this kind which take place unceasingly in high mountains and before which we usually stand powerless, changes in the forests, even on the plains, take place constantly as a result of the exposure of the roots from the working away of the soil. This is especially the case in forests in hilly places when streets are cut through. The forest soil is usually porous or becomes so by drying and as soon as the street cuts through a hill over- grown with large trees. the free roots are found at the edge of the cut, from between which the soil has fallen out or been worked away. The injury is two-fold since the exposed side of the root crown weakens the anchorage of the trees and the decreased supply of water impairs the formation of the tree top. The statement that the injury caused by such cutting of the forest for shortening the road is compensated for by the increased growth of trees is an error. To be sure this may, under certain circumstances, effect a con- siderable increment of growth, as, for example, Hartig’s* investigations 1 Hartig, Ueber den Lichtstandszuwachs der Kiefer. Allg. Forst- u. Jagdzei- tung. LXIV, 1888, Januar. gl show. He found in pines 147 years old which had been standing free for seventeen years, that the growth had been doubled in the first ten years, especially in the lower part of the trunk, where the amount of wood, that is the dry weight, had also increased. But he also demonstrated that the in- crease fell to the earlier amount, when the food in the soil was taken up by spruces which were set out there. In trees whose roots are exposed on one side, there is a less water content of the soil which also retards the absorption of foods and the influence of light is scarcely able to cause an increase of growth. But even if a considerable increase of growth is ob- tained by the sudden thrusting of the trees into the light, no agricultural ad- vantage is constantly connected with it. In the first place, the branching is increased and, in the second, the wood due to the rapidly increased growth is coarse grained. This is deduced from the observations of Cieslar and Janka' who investigated the spruce wood produced by long-standing cultivation. Produced in great quantity the wood was of strikingly low specific gravity because the autumn wood made a scanty growth and the tracheids, in the main part of the annual ring, were unusually wide. On the other hand, the danger of drying of the top, or blight of the tip, often becomes greater. This applies also to deciduous trees grown in dense plan- tations. The crowns are suddenly freed, their leaves, in structure and func- tion, are adapted to a moderate amount of illumination, can not endure the increased transpiration and the excess of light so that the tips of the branches partially die back. Therefore it is urgently advised in the interest of retaining old tracts of woods, specially in sandy soil, to avoid cutting through the hills to lay out roads, preferably to lay the road out around the hill. According to Hartig? the shock of the sudden opening may also lead to injury if, with the increased supply of light, the top is stimulated to too active growth. This continues some years, while the available quanti- ty of nutriment in the soil lasts. Because the leaf material is increased as a result of the intensity of the light, much larger amounts of mineral stuffs naturally are required than with growth in dense tracts. However, when parts of forests are exposed, soluble mineral food material can not be pro- vided in sufficient quantity by the influence of the atmosphere, consequently after a good growing period there is a decrease in growth due to the “im- poverishment of the soil.” Following a scarcity of material, however, no matter whether due to an actual lack of the substance or to its insufficient absorption on the part of the tree, as a result of injuries to the roots or a lack of water, there is not only a decrease of growth but also the constitution of the wood is weakened. As when growth is forced, only the thin-walled spring wood, the vascular tissue, is formed and but little or no strengthening tissue, which is present in late wood. 1 Cieslar, A. und Janka, G., Studien tiber die Qualitit rasch erwachsenen Fich- tenholzes. Centralbl. f. d. gesamte Forstwesen 1902. Part 8. 2 Hartig, R., Ueber den Hinflufs der Kronengroéfse und der Nahrstoffzufuhr aus dem Boden auf die Gréfse und Form des Zuwachses etc. Forstl. naturw. Zeitschrift VII, 1898, p. 78. g2 b. GROWTH oF STILTS. (ELEVATION OF THE Roots oF TREES. ) In this connection it is advisable to consider still more closely the fact that large forest trees grow with their older root branches above the ground, so that the base of the stem is carried on a number of stilts. This position gives scantier anchorage to the trees and results disadvantageously since they are more easily blown down in wind storms. In addition to this there is a smaller provision of water and the roots are peculiarly sensitive. These stilted growths form two types; first, in spruces, where the base of the trunk is raised high above the soil and the strong branches of the root crown have never been below the top of the earth; second, in pines, not rare on strongly undulating sandy soil, in which the base of the trunk has previously been covered with soil or may even frequently rest on its surface so that part of the crown is covered with earth, while the other part has been uncovered by the washing away of the soil. In extreme cases the soil slides out from under the trunk so that the whole tree stands on stilts. Examples of the first type are described and illustrated by L. Klein’ (Figure 4). He explains the production of the phenomenon as follows :— If spruces or firs have been felled in the mountains a stump is left standing which weathers gradually on its upper surface and becomes covered with moss. Later Vaccinia etc. infest this moss cushion beneath which is produced a thin humus layer. If self-sown spruces or firs begin to grow on the moss-covered surface of the stump, the little young growing roots créep under the moss-covering in all directions over the surface of the stump and then down its sides to the soil, and develop further there, like every other root. In the course of many decades the roots become stronger, the old stump slowly rots away. Klein answers the question, as to why one usually finds spruces much more rarely than firs and never any deciduous trees with this stilt-like growth, when he states that the water needed by deciduous trees is possibly ten times as great as that of conifers and that on this ac- count the seedling of a deciduous tree would not find enough water perma- nently on the surface of the stump for its development. Even if deciduous trees do not grow on stilts, yet similar structures such as the sheath growth, may nevertheless be found. This occurs especially in willows. Where old willows grow along country roads, one finds at times the appearance of a new trunk growing independently out of the decayed heart of the hollow old trunk, so that the woody cylinder of the old trunk surrounds the young tree like a wide sheath. Such cases are easily explained in the pollarded willows when the crown is entirely cut off every year or every second year, in order to obtain as many young shoots as possible. With the rapid rotting of willow-wood on large pollarded surfaces, soil accumulates very quickly from 1 Klein, L., Die botanischen Naturdenkmiler des Grofsherzogtums Baden u. ihre Erhaltung.. Festrede. Karlsruhe 1904, p. 138, Fig. 7. 93 the dust blown from the street into the depressions of the wounded surface, in which seeds of all kinds of weeds find instant lodgment. Now if a wil- low-seed falls into one of these accumulations of soil, the young seedling finds space for development and its roots finally reach the soil through the rotted wood of the old trunk. When an adventitious root of especial length grows downward from the pollarded surface at the crown of the tree, with- in the hollow trunk, it has the appearance of a young trunk. N Fig. 4. Stilted spruce near Schdmtinzach in Stiibewasen. (After L. Klein.) A. case, due probably to the same conditions, which cause the stilt-like growth of spruces, was shown as recently as the 80's of the last century in Kohlhasenbritck near Neubabelsberg (District of Potsdam). The stump of an old oak, about 75 cm. high on the village street, had formed a broad hollow cylinder by the rotting of all of the heart wood. This was half filled with rotten wood and earth and a healthy oak, possibly thirty years old, stood in this as in a sheath. In spruce plantations one finds at times the so-called “Harp-trees” in which a number of side branches have become elevated at right angles to the 94. main trunk which the wind has blown down, part of whose roots, however, still remain in the soil, and therefore are still living. Adventitious roots serve the needs of these growths for nutrition. The spruce is certainly the one of all the conifers which can most easily overcome all injuries by develop- ing adventitious organs. It also withstands pruning very well and can therefore be used ad- vantageously for hedges, only the hedges must be thinned constantly, or they become bare underneath. The ability to form new tips when the old ones have been removed, a characteristic of spruce and Araucaria, is taken advantage of in horticulture, in propagating by cuttings. On the other hand, the regeneration phenomena of the older pine are most stable and fixed. The second type of stilt-growth occurs especially with this tree, if, in a hilly place, the porous sandy soil slides downwards from the effects of grading. In the struggle for existence, however, the pine when grown from seed can withstand much better exposure of its roots than spruces and firs; this is because the roots habitually grow perpendicu- larly into the ground. In the two illustrations which reproduce two examples of Pinus silvestris from the Grunewald (back of Paulsborn) near Berlin, this perpendicular downward growth is shown especially well in the side roots. Figure 5 shows two pines standing back of one another with the bases of their trunks about I meter above the ground. The strong main roots send their side branches (arising directly on the underside) into the ground in parallel and perpendicular directions, indicating that the pine roots deeply. The front tree is possibiy 60 years old; the specimen behind it is younger. Figure 6 is taken from another side and shows the side roots starting at right angles from the main branches which spread horizontally from the root crowns. However, in the middle of the stilt appearance, may be dis- tinctly recognized the original main root which as a prop has grown directly into the earth and which endures the chief strain of anchoring the tree in the sandy soil. The tree is still well covered with needles. One more important phenomenon must be mentioned in connection with this form of stilt-growth, viz., many woody tubers with a dense covering of bark grow in rows on the upper sides of the strong roots. These in figure 7, reproduced natural size, form hemispherical, wart-like prominences up to 1.5 cm. high, with a crater-like depressed centre. They correspond with the rest of the root in color and bark. It is supposed that this arises from an adventitious sprout formation in which the young shoots have died immediately and a heavy scar has been formed. The fact that these growths come only on the upper side lends strength to this supposition. It is well known that when there is this ten- dency toward adventitious growths in trees, the formation of such buds of all sizes occurs most strongly on the side toward the light (Tilia, Acer). This supposition has not been generally confirmed, as the cross-section (Tig. 8) shows. This illustrates a seven years’ overgrowth of a centre of disease formed by a homogeneous magg of resin. This resin gall, produced by resin- SS Fig. 5. Fig: 6. Stilted pine from Grunewald near Berlin. Stilted pine from Grunewald near Berlin. (Orig.) 96 osis of the wood, ruptured on the outside and was overgrown in the follow- ing years. The edges of the over- growth, still connected in the first few years, have grown back farther and ' farther ;—in this way, a crater-like opening was produced at the top of the woody tuber. The new annual rings turn to resin every year and always in the first spring wood, which consists in part of parenchymatically formed cells. The resin holes (H) are pro- duced by the drying up of the resini- fied tissues, in part also by exudation of the resin. The edges of the over- growth are further apart each time so that the last ones (U) are widely sep- arated. In this, they show a most ir- regular construction often changing between every two medullary rays in the same annual ring. In the drawing G is the normal wood in cross-sec- tion and M the regular course of the tracheids in longitudinal section. These are in the same annual ring just as in true enarls Fig. 7. Resin galls with gnarl =) lac growth on the upper side of the stilt- like root of the pine (natural size). For this reason these structures (Onies) must be classed with the resin galls. So far as their production is concerned, it must be assumed that the exposed root shows small centres of injury from extremes of weather on its upper side, i.e. the one most exposed to such extremes.) siiese centres of injury have caused a resinosis of the tissues, or rather, a com- plete resinous liquefaction. We may assume that frost has caused the injuries, and especially late frosts, since these appearances are al- ways found in the first formed spring wood. The production of these resin Fig. 8. Cross-section through a resin gall on the stilt-like root of the pine. (Orig.) galls shows that the roots OF exposed in the stilt-like growth are very sensitive. If this is true, less extreme cases will have to be taken into consideration and a further warning be given; when possible the root body must be guarded from complete exposure. When roots are partially exposed their bark is liable to be breken on the upper side by pedestrians, with the result that much stronger annual rings develop on the under side which is protected from such injuries by the earth. The cultivation of seedlings of the different species of our common coni- fers under the same conditions gives the best demonstration of these root systems. Nobbe! carried his experiments out with the following re- sults :—Six months after sowing, the pines had 3135 root fibres with a total length of 12 meters, the spruces 253 fibres, all together 2 meters in length and the fir, 134 fibres with a total length of 1 meter. In one year, in fertilized sandy soil, the tap-roots of the pine seedling penetrated almost one meter deep, while the spruce and fir, under absolutely the same experimental con- ditions, went down only one third as far. At the same time the young pine developed five series of roots, the spruce four and the fir three. In decid- uous trees, oaks and beeches, Tharandt’s experiments showed that in the same way they form even in the first year a widely branched root system with tap roots nearly a meter long. Spruce and fir with their weaker root apparatus, which almost im- mediately spreads out flat, need a moist soil, while the pine can do without moisture, in fact, easily suffers from it. In seedling plantations, where fir and spruce thrive, the pine very often shows pathological resin ducts in the wood of its young trunk. The deep growth of the pine also explains its so- called “contentment” and its healthy growth in almost sterile sand. Like the lupin it understands how to meet its need for water and food from the deep layers of the soil, but it demands good drainage. This natural advantage of a tap root penetrating at once to great depths is made use of only where seeds are planted in forests without necessity for transplantation. In the controversy in forestry circles as to the best methods of planting, in considering the pine, we would always place ourselves on the side of those favoring sowing in the permanent place. For the spruce and fir, we consider transplanting from the seed bed to be more advantageous. In any event the method of seeding is not the only factor in a healthy devel- opment, but soil and position are often decisive. We can not consider ad- visable the present endeavor to plant pines everywhere, because they give the quickest and therefore the best return from the soil. In our own forests comparisons of the trees in deep lying or marshy places with those on free, dry regions show that in the marshy localities there is an impoverished growth and often a premature dropping of the needles, and that in hilly sandy soil, with deep lying ground water, the trees develop to their full strength, even being well-preserved when their roots are exposed on stilts. Rechinger? 1 Dodbner’s Botanik fiir Forstmiinner. IV Edition, revised by Fr. Nobbe, Berlin. Paul Parey. 1882, p. 130. 2 Rechinger, Bot. Beobacht. in Schur. cit. Bot. Jahresber. 1902, I, p. 387. 98 mentions the occurrence of stilt-roots in marshy forests, in which Alnus glutinosa predominates while isolated Quercus pedunculata, Rhamnus Frangula and Salix cinerea occur. A third cause of the stilt-like growth still remains to be mentioned which is different in that the trees are positively elevated, while, in the cases already mentioned, the base of the trunk remains at the place where the seed was sown. White’ describes occurrences of this kind. He thinks that on rocky soil, where the roots must grow flat, the trees are gradually forced out of the ground by periods of frost and draught to which they are peculiarly susceptible. c. Too DEEP PLANTING. Too DEEP PLANTING OF TREES. Almost all our trees, in their later life, stand in a position different from that of the seed beds in which they develop. For fruit trees must have a sec- ond transplanting when young in order to obtain an abundant ramification of the root body. Since these trees must be so transplanted great care should be taken that they are not planted deeper than they originally stood. Exper- sence teaches that trees can indeed be destroyed through a disregard of this warning. In fact many practical workers recommend that each tree in its new position be oriented exactly as before in regard to the points of the compass, since they think that many kinds of bark injuries from heat and frost can thus be avoided. Otto? has attempted to decide the question whether the branches of apple, pear and cherry trees develop differently in the several points of the compass. By chemical analysis, he found essential differences in the com- position of the differently oriented one year old branches. The water and nitrogen content is the smallest on the east side, while the content in dry sub- stances is the greatest there ; but the water and nitrogen content is greatest on the north side. This would indicate that the branches were not so fully ma- tured here as on the other side of the tree. : Kovessi® considers the cause of a decreased formation of blos- soms to be the greater amount of water and the lesser ripening of the wood of the branches. The number of blossoms and fruit was certainly proved to be dependent on the water supply of the previous vear. The tree bears better, if the water supply is scant. Anatomically, the differences in the maturity of the branches, according to the points of the compass, can scarce- ly be determined since the structure of the same annual ring fluctuates too greatly within the different internodes of a branch’. 1 White, Theodore, Mechanical elevation of the roots of trees. The Asa Gray Bull. Cit Bot. Jahresb. 1897, I, p. 85. 9 2 Otto, Arbeiten der Chemischen Versuchsstation zu Proskau. Cit. Bot. Cen- tralblatt 1900, Vol. 82, Nos. 10-11. 3’ Kovessi, F., Ueber die Beziehung des Wassers zur Reife der Holzpfianzen. Biedermann’s Centralbl. 1902, p. 161. 4 Sorauer, Beitrag zur Kenntnis der Zweige unserer Obsthatime. Forsch. a. d. Gebiete d. Agrikulturphysik, Vol. III, Part 2. 9 Also, we know nothing definite, at least nothing which holds good in general, of the anatomical changes taking place when trees are planted too deep. In some cases it has been observed that the ducts are filled with brown, gum-like stiff masses, in others they are filled with tyloses accom- panied by a brown discoloration of the walls. Gummy swellings of the mem- branes are not infrequent. But these are all only occasional cbservations and experimental study of the question is still needed. We will limit ourselves on this account to the enumeration of the dis- coveries already made as to the influence of the two factors occurring most generally when trees have been planted too deeply—the lack of oxygen and the excess of carbon dioxid. We know that plants without a supply of oxy- gen gradually die. If the living cell can take up no oxygen, it changes the direction of its life-functions. Later it passes over into a state of rigidity, since the phenomena of movement cease in the cytoplasm, the sensitiveness to stimuli is lost and growth becomes inhibited. The plant, however, does not die immediately. It continues to give off carbon dioxid for some time and, with a renewal of the oxygen supply, it can even re-assume its usual functions after a rather long apparent death. In this continuation of life without oxygen (anaerobic) the oxygen necessary for the life pro- cesses must be furnished from the substance of the plant itself and has been called intra-molecular respiration. Lechartier and Bellamy’, in a series of experiments, have proved that alcohol is formed in the parenchyma cells growing without a supply of oxygen, not only in our pitted and other fruits, but also in the roots and leaves. Stocklasa has also proved most recently that there is a forma- tion of lactic acid. Even in fungi (Agaricus campestris), Muntz*? found alcohol and hydrogen in considerable quantities if the fungi were kept for some time in air free from oxygen. The material for this alcohol can have been furnished by the kind of sugar alone present here, named man- nose, while in other fungi, producing only alcohol, (without hydrogen) in an atmosphere of carbon dioxid, the trehalose must have been fermented. If the rungus is not kept too long in the oxygen-free air, it can take up again its normal life-functions, as has recently been proved by Krasnosselsky* tor Mucor spinosa and Aspergillus niger. Adolf Mayer* had earlier expressed his opinion that fermentation produced by yeast, is a_ re- sult of respiration in the absence of oxygen. Pasteur? and Bohm* had really proved already that all more highly organized land and water plants behave in a very similar way, since, in media free from oxygen, they 1 De la fermentation des pommes et des poires. Compt rend. t. LX XIX, p. 949.— De la fermentation des fruits ib. p. 1006. 2 Comptes rend. LXXX TI, p. 178. 3 Krasnosselsky, Atmung und Girung der Schimmelpilze ete. Centralbl. f. Bakteriologie etc., 1904, Vol. XIII. Nos. 22-23. 4 Mayer, A., Untersuchungen iiber die alkoholische Girung. Landwirtsch. Ver- suchsstationen, 1871. 5 Faits nouveaux pour servir Ada connaissance de la théorie des fermentations proprement dites. Compt. rend. 1872, p. 784. 6 Bohm, Ueber die Respiration von Landpflanzen. Sitzungsber. d. k. Akad. 4. Wissensch. 67. Section I. 100 reduce a part of their substance by fermentation to carbon dioxid and alco- hol, as do the yeasts in self-fermentation. The green parts of plants at any rate, with sufficiently intensive illumination, can establish an atmosphere suited to their normal respiration by decomposing the carbon dioxid which had been given off immediately before. Aerobic and anaerobic respiration are interdependent and anaérobic is able to withstand total destruction for some time, even if growth is impossible This retardation becomes greater as the temperature is lower. Thus, for example, Pfeffer’ cites the observations of Chudiakow, that the failure of the carbon dioxid production, 1. e. the pos- sibility of living, begins after twelve hours in seedlings of maize at a temper- ature of 40°C., after 24 hours at 18°C. and only after some days at a lower temperature. If an organism or one of its members always has a lower vitality, it also will keep alive longer in a place free from oxygen. Thus, under such conditions, apples and pears at a moderate temperature have been kept growing and ripening for months while rapidly growing moulds and aérobic bacteria went to pieces quickly. In seedlings of phanerogamic plants (Vicia Faba, Ricinus etc.) there is an increase in the intra-molecular exchange. Stich’s? experiments show that single plants at times, or parts of plants, at first exert no influence on the oxygen content in the air by their respiration since, in a hydrogen atmosphere, they form exactly as much car- hon dioxid as in air. With 8 per cent. of oxygen in the air, the respiratory quotient was still normal,—with a lesser content (2 to 4 per cent.) it was changed in favor of carbon dioxid because an intra-molecular respiration took place. When the plants were kept for a longer time in an atmosphere poor in oxygen, the normal respiratory quotient was gradually produced to- gether with a decrease of the absolute amount of oxygen and carbon dioxid. In a gradual withdrawal of the oxygen, the intra-molecular respiration is first stimulated by a considerably lower percentage of oxygen than when the oxygen diminution is sudden. Brefeld’s* experiments lead to the conclusion that alcoholic fer- mentation in all plants, from the lowest to the highest, takes place as soon as the oxygen supply ceases. A very essential difference is shown, however, in the different organisms which produce alcohol. While generally in yeast (Saccharomycetes) the phenomenon of fermentation is to be considered the climax of the normal activity of the organisms (which actually grow during the process of sugar decomposition), it appears in the cells of phanerogams as an abnormal process ending prematurely in the death of the cell. This differs essentially from the pure fermentation of yeast producing only alcohol and carbon dioxid, by the appearance of further products of decomposition among which fusel oil and acids are especially noticeable. There is a great 1 Pfeffer, Pflanzenphysiologie, 1897, Vol. I, p. 544. 2 Stich, C., Die Atmung der Pflanzen bei verminderter Sauerstoffspannung und bei Verletzungen. Flora 1891, p. 1. 8° \Ueber Garung III, Vorkommen und Verbreitung der Alkoholgirung im Pflan- zenreiche. Bot. Zeit. 1876, p. 381. Tol difference in the ability of fungi to endure alcohol, as is shown among those which still introduce an actual alcohol fermentation. For Saccharomycetes, 12 per cent. of the weight is the limit of growth; 14 per cent. the limit of fermen- tation. In Mucor racemosus, which lives on sugar without ee oxygen, the limit of growth and of fermentation lies between 4% and 5% per cent. alco- hol; Mucor stolonifer, on the other hand, no longer grows and can not be- gin fermentation with 1.5 per cent. alcohol. It should be concluded from these results that under the same external conditions even phanerogams succeed in forming alcohol of very different percentages and endure it in different amounts. Later Muntz' speaks very generally of alcohol as one of the decomposi- tion products of organic substances formed on the surface of the earth as well as in the soil and in the depths of the ocean and distributed in the at- mosphere according to the laws of the tension of gases. It can not be surprising that organic acids, among others acetic acid, occur in the fermentation of alcohol. It is very probable that the accumu- lation of such acids must ultimately act as a poison upon the organisms and that in roots, which are entirely or almost entirely cut off from atmospheric oxygen, there will begin a gradual dying back. When trees have been planted too deep and the roots need an abundance of air, perhaps more than the top part of the plant, the lack of oxygen will be felt more quickly the greater the power of the soil to hold water and the more the parts are cut off by water®. Water near the living roots becomes more and more a source of danger for the larger, healthy roots and for the sunken bases of the trees, since the water becomes more and more charged with carbon dioxid. If healthy plants are set in water containing much carbon dioxid they begin to wilt and the leaves begin to die back’*. Kosarofft’s* studies on the absorption of water in insufficiently drained soils, i.e. those poor in oxygen aud rich in carbon dioxid, are especial- ly interesting. The water absorption and transpiration were proved to be repressed by the carbon dioxid. Plants whose roots remained in an at- mosphere rich in carbon dioxid lost their turgidity immediately and be- came limp; when kept there longer they disintegrated. In experiments in an hydrogen atmosphere where, therefore, only the lack of oxygen becomes de- pressing, it was shown that this circumstance does not act in any way as in- juriously as an excess of carbon dioxid. Therefore, in the roots of trees lying too deep, death by poison begins by attacking first the tender organs, later the older ramifications of the roots. At the same time the putrid products of porcppsilien make the whole soil unfit for the growth of plants. Bohm*® cites an example in the dying 1 From Compt. rend. Vol. LUXXXXII, p. 499. cit. in Biedermann’s Centralbl. 1881, Dp. 109; Mayer, Agrikulturchemie, 5th Edition, 1901, Vol. I, p. 116. Wolf. W., Tageblatt der Naturforscher-Versammlung zu Leipzig, 1872, p. 209. 4 Kosaroff, Einfluss verschiedener usserer Faktoren auf die Wasseraufnahme der Pflanzen. Dissert. Leipzig, 1897, cit. Naturw. Rundschau, 1897, No. 47. 5 Bohm, J., Ueber die Ursache des Absterbens der G6tterbaume und tber die Methode der Neubepflanzung der Ringstrasse in Wein. Faesy & Frick. 2 2 3 102 Ailanthus trees of the Ringstrasse in Vienna which had been planted too deep. These trees years before had fallen off in growth, for in the first year after they were planted, their annual rings were more than 3 cm. broad, in the last year the growth was 0.5 cm. At the time of death the earth about the roots was found to be so injurious that seeds of different plants sown in the soil in the open and under bell jars began to decompose at once. Seeds developed luxuriantly, however, after this soil, repeatedly washed with water, had been exposed in thin layers to the atmosphere for eight warm days in July. Similar experiments were undertaken by Mangin' who, before this time, had ascribed the diseased appearance of the street trees in Paris to the bad composition of the soil. Seeds and tubers sown in soil re- moved from around diseased roots showed an interrupted development. The air tests made rear the diseased roots of Ailanthus showed a de- ficiency of oxygen and a preponderance of carbon dioxid and Mangin? suspects that the lack of oxygen may be traced back to a reduction by sulfids. Certainly numerous micro-organisms co-operate in the decom- posing process of the roots. However, such an attack by the suitable bacteria would not have taken place if the oxygen in the soil had not begun to be deficient. When trees with spongy bark have been planted too deep, as in the above mentioned Ailanthus trees in Vienna, the bark under the soil is found entirely rotted away. According to the age and the bark structure of the tree, as well as the physical constitution of the soil, a disturbance of the ab- solutely necessary circulation of the air will appear sooner or later in the buried base of the trunk. This disturbance will be felt also in both the ven- tilatory systems of the trunk, viz., in the vascular system of the wood body and the bark system communicating with it by means of small hollow spaces. The green bark parenchyma protected by the more or less strongly developed cork is bathed by the atmospheric air; it penetrates through the lenticels into the intercellular spaces where it circulates. The air penetrates the ducts of the wood, partly through the water from the roots, but largely by diffu- sion from the sides and is also in circulation, as mentioned abave. In fact, as may be assumed from the investigations, of O. Hohnel’, a daily periodicity probably takes place in this circulation. The ducts originally filled with water are partly or entirely emptied in the course of the day, since the superior and surrounding tissues draw away the water. The trans- piring leaf body of the tree needs a very large amount of water and draws it from the wood tissues of the branches which make good their losses from the trunk, in which therefore a suction wave advances down toward the base and thence out into the roots. 1 Mangin, L., Sur la végétation dans une Atmosphére viciée par la respiration. ¢. rend. 1896; p. 747. 2 Mangin, L., Sur l’aeration du sol dans les promenades et plantations de Paris, C. rend. 1895, Il, p. 1065. 3 vy. HoOhnel, Beitrage zur Luft- und Safthewegung in der Pflanze. Pringsh. Jahrb. f. wissensch. Bot. Vol. XII, Part I, p. 120. 103 Since more water is drawn away from the ducts than can be replaced instantly, a space partially filled with air appears in these ducts causing a negative pressure (suction) which is so much the greater the less the amount of air present at the beginning or slowly diffused through the membranes, for so much the more must the originally small volume of air be distended to fill out the hollow space which is always becoming greater. In the night, when the evaporation is arrested or very much repressed, the ducts of the trunk again suck up great amounts of water, in fact, this suction 1s often increased by the pressure proceeding from the roots which can press so much water into the ducts that a great part passes through the membranes into the surround- ing cells and intra-cellular spaces. If this liquid drawn up from the root body or pressed up by it is healthy, a considerable infiltration into the intercellular spaces will take place without disadvantage to the body, as has been shown by Moll'. If, however, the water mass is already laden with the products of fermentation from the putrefying root tips, we see that these poisonous substances get into the especially sensitive sapwood and bark and thus the dying back easily spreads. Trees planted too deep, however, usually die only in heavy soil per- manently loaded with water. In light soils they suffer but do not die. If the heavy soil with its water burden surrounds the base of the trunk and pre- vents intercellular ventilation by means of the lenticels, alcoholic fermenta- tion and the formation of acetic acid must naturally appear in the bark cells and lead to a dying back which is continued radially to the cambial zone and the young sapwood which is especially active in conducting water. Thus there remains from year to year a cylinder of heartwood in the middle of the trunk which is always becoming smaller and smaller and which usually has to meet the water need of the aerial part. The heartwood which is poor in water, however, is less suited for conducting it and the dead tis- sues of the wood, which at any rate can still conduct water mechanically, will not be able with their help to meet the need of water in the crown. Con- sequently, the tree ultimately wilts or fails to put out buds in spring. The fact that the non-parasitic processes of decomposition in the buried end of the trunk cease near the upper surface of the soil leads to the theory that processes of decomposition are not able to attack healthy plant cells but only those weakened and functionally abnormal. Such weakening is actually present. It was mentioned at the beginning that cells full of life and rich in content, when shut away from the oxygen of the air, begin at once to de- velop alcohol through the activity of fermentation (alcoholases) which was not present previously and which disappears again if the plant regains its atmospheric air. It has been proved further that the plant, in the absence of oxygen, continues for some time to eliminate carbon dioxid in considerable quantities (respires intra-molecularly) but that these amounts of carbon 1 Untersuchungen iiber Tropfenausscheidung und Infektion, 1880, p. 78. Sep. aus Verslag en Mededeéling d. Koninkligke Akad. Amsterdama, cit. in Pfeffer, Pflanzenphysiologie, 1881, I, p. 159. 104 dioxid are still smaller when the experiments are continued longer than those of plants respiring in air which contains oxygen'. Since the carbohydrates (starch, sugar) furnish the material for respiration, it should be assumed from the above facts that these material contents of the cell are made use of abnormally in the absence of oxygen. With Pfeffer? respiration can be conceived of as a process set up .by two dove- tailing processes. The first is the intra-molecular respiration ascertained in the phenomena of fermentation which Borodin* named internal oxidation. The second process, possible only with a supply of oxygen from with- out, is the immediate further oxidation of the products of fermentation in the moment of their production. If this last act, absolutely necessary for the life of the cell, is suppressed, not only the zone of the trunk of the tree, planted too deep and lacking oxygen, loses its respiratory material, that 1s, always becomes poorer in reserve substance, but it also forms those products which lead to decomposition and the death of the cell. Insufficient respir- ation therefore is a necessary preliminary condition for the dying back and, to the degree in which the buried part approaches the surface of the soil, gradually getting more and more oxygen, the fermentation will become weaker and weaker and pass over into the normal process of oxidation so that decomposition gradually reaches its limit. It is thus only a question whether the tree has the possibility of forming new rocts in the soil above these limits in order to meet the loss of water produced by the transpiration of the foliage. The stunted production frequently observable in early years disappears as the more plastic material can pass downward and be used for the new structures in the wood ring of the trunk and the roots. The more rapid the growth, the greater the energy of respiration (as shown by Saus- sure) and the more the flat new root body is reached by light, so much the more will the production of carbo-hydrates and its absorption of oxygen and production of carbon dioxid increase’*. The behavior of the trees planted too deep or only partially buried de- pends naturally upon their specific character. In willows and poplars, for example, the part ‘sunk in the earth may indeed be found to be dead, but near the top of the soil, the decomposition appears to have been stopped. Numerous adventitious roots have been formed from the trunk which, some time after the tree has been buried, starts a healthy development of the crown. The tree is therefore saved if it is able to produce new roots quickly near 1 Wortmann (Ueber die Beziehungen der intramolekularen zur normalen At- mung der Pflanzen. Inauguraldissertation. Wirzburg 1879) states, to be sure, that the amounts of carbon dioxid are equally large in intra-molecular and normal respiration; it seems to me, however, that the short duration of his experiments also caused the observation of the after effects of a previous normal functioning. He, himself, admits (p. 31) that in a longer period with no addition of oxygen a smaller amount of carbon dioxid was produced by the plants under experimentation than had been the case in the constant presence of oxygen. 2 Pfeffer, Ueber das Wesen und die Bedeutung der Atmung. lLandwirtsch. Jahrb. 1878. 2 Borodin, Sur la respiration des plantes pendant leur germination. 4 Borodin, Mémoires de l’Acad. impériale des sciences de St. Petersbourg. VII série. 1881. 105 the earth’s surface. It is well-known that Ericaceae and Epacrideae are especially sensitive to too deep planting. In these species the base of the trunk dies even when the root has not suffered very much. When the sap- ling shows moss and lichen growths at the base, there is every reason for being careful. In nurseries no one general rule holds good in regard to the depth of planting. Aside from the important physical composition of the soil much depends in grafted trees upon the stock. Fruit varieties grafted on wild stock should be so planted that the root neck remains in the plane of the surface of the soil or even projects a little above it. In fact in marshy soil, with a great deal of moisture, planting is made in hills. Pears grafted on dwarf stock (on quinces) and apples (on Doucin and Paradise apples), on the other hand, must be planted at least so deep in the soi! that the place of grafting is found at the surface level of the soil; i.e., the whole stock under the soil. From this a considerable number of adventitious roots develop which are especially useful for nutrition. Bouché! has given a splendid summary of practical experiments. He refers first of all to the fact that in old healthy trees the strong roots are seen to appear above the soil and that this appearance of the root neck is normal. Many trees can survive deep planting when young, since they put out new roots from the base of the trunk just below the surface (elms and lindens) ; others, on the contrary, are very sensitive, as, for ex- ample, pears, maples, oaks, most of the Rosaceae, plane-trees, walnuts, red and white beeches. Also most conifers require care in planting, as, for ex- ample, the genera Pinus, Picea and Abies and at times also Thuja, especially Thuja (Biota) orientalis and related species, while deep planting has been proved to have been endured by Thuja occidentalis, T. Warreana, T. plicata. - Bouché found trunks 5 to 8 em. thick putting out a number of new roots from their buried bases whereby they were very much strengthened. Juniperus communis must be planted shallowly but J. Sabina and related species sur- vive deep planting with advantage. It has already been stated of poplars and willows that deep planting is counterbalanced at once by the formation of new roots on the surface of the soil. In weak trunks it is often found that the roots formed just below the surface get the upper hand over the older, deeper ones. It is actually even more advantageous to plant many bushes deeper than they stood before because they strengthen themselves by numerous new roots from the buried base of the stems. This is noticeable for example in Calycanthus, Cornus alba and C. sibirica, Ribes, many kinds of Spiraea, Viburnum Opulus, Aesculus macrostachya, Symphoria, Ligus- trum, Rosa gallica etc. On the other hand Caragana, Berberis, Colutea, Cornus mascula and C. sanguinea, Corylus, Cytisus, Rhamnus, Sambucus, should be planted at the old level. 1 Bouché, C., Ueber das Tiefpflanzen von Baumen ete. Monatsschr. d. Ver. 2. Ford. d. Gartenb., v. Wittmack, 1880, p. 212 and Wredow l.c. p. 75. 100 In planting streets, besides the embankment which sometimes becomes necessary, the asphalting and cementing of the street causeways is also very injurious to the roots of the trees. The injury is due not only to the shutting off of the atmospheric air but also the loss of precipitation from the air, upon which trees in large cities become so much more dependent, as the level of the ground water has fallen because of canalization and the workings of the subsoil in building. Young trees which are planted after the falling of the level of the ground water strive to reach this despite the increased depth of the springs. Consequently in order to facilitate this, the holes for planting the trees must be made considerably deeper in such localities. According to Bouché, this increased depth amounts to 60 cm. in Berlin so that now the holes for planting trees must be dug 1. 5 cm. deep. Too DEEP SOWING OF THE SEED. The discovery has also often been made that from a plentiful sowing of good fresh seed a comparatively small number of plants is produced. As is generally believed, the cause lies more frequently in sowing the seeds too deep. When harrowed in or hoed under in places, as is customary with barley’, some seed grains necessarily come to lie too deep, others too superficially. Uniformity can be obtained only by planting with a drill. But even the gardener, who can cover his seeds very uniformly in seed pans, not infrequently obtains only a low percentage of plants in sowing very fine seeds even if the seed was good and of high germinating quality. The processes causing the loss, however, are not always the same, and do not always take place under the same conditions; on this account it is impossible to generalize. In order to protect oneself from injury in this connection, there is nothing to be done except to understand clearly the in- fluence of the different factors to be observed in sowing seed and to see: which combinations exist in every individual case. There are three phases in germination. Each can be disturbed and cause failure. The first stage consists of the swelling of the seed and is a mechanical process, in which (probably by water condensation) an increase in temperature has been observed. This introduces the second stage, the mobilization of the reserve subsiances, a chain of chemical phenomena, and these accompany the third act, that of the formal development. Disturbances in the stage of swelling have often been observed. Nobbe and Haenlein? found especially in Papilionaceae and Caesalpiniacea, that the seed shell at times is so hard that water can not enter, that the seeds retained the embryo for years without development, but always in a healthy condition. The seed did not germinate because it did not swell. In clover seed, the superficial shell or hard layer containing the coloring matter, is 1 EHggers-Gorow, Versuche iiber den Nutzen oder Nachteil einer flachen oder tiefen Bestellung der Gerstenkérner. Mecklenb, landw, Ann, 1874, No. 23. 2 Nobbe und Haenlein, Ueber die Resistenz von Samen gegen die dAufseren Faktoren der Keimung. Versuchsstationen 1877, p. 71. 107 shown to be so impermeable for water that clover seeds can lie from one to two weeks in English sulfuric acid, and for years in water, without losing the coloring matter which in itself would be soluble in water. In such cases cenly mechanical treatment is of any use. Galter and Klose* mixed the seeds of lucerne (alfalfa) and varieties of clover with fine sand and trod for ten minutes on the bag containing the mixture. After this treatment, 13.4 per cent. of the seeds of the lucerne were found to be more capable of swelling, 10.2 per cent. of the white clover and 37.8 per cent. of those of the bird’s-foot, without showing any especial injury. Nobbe cites examples? of an unexpectedly long retention of the germinating power. 32 per cent. of seeds of Pinus silvestris, gathered in 1869, after having been kept 5 years in closed glasses in an occupied room, still germinated, and after 7 years 12 per cent. With red clover seeds (Trifolium pratense), preserved in the same way, 10.5 per cent. germinated after 12 years, peas (Pisum sati- vum) 47.7 per cent. after 10 years, Spergula arvensis 20 per cent. after 12 years, flax (Linum usitarissimum) 49 per cent. after 6 years and 2 per cent. after 11 years. Out of 400 seeds of the locust (Robinia Pseud-Acacia) after ten days, longer than which the time for practical purpose does not last, 71 grains germinated ; at the end of the year, 55 grains; in the next year 18; in the following year 7 and, after 7 years, one seed; all were kept contin- uously in distilled water which was renewed periodically. From these ob- servations it seems credible te us that many buried seeds, unimpaired in life- power, survive for very long periods. Even in the locust seeds mentioned above, the remainder, left ungerminated after seven years, was still perfectly healthy. A slight injury to the seed shell resulted after a few hours in a swelling up and also, as a rule, in rapid germination. Disturbances of the second phase of the process of germination, the stage of chemical action converting the solid reserve substances into the easily transpired constructive matter, are observed very frequently. The tact that many hard seeds such as Crataegus, Rosa, Juglans, Prunus, lie un- harmed for a year in the soil, is not to be confused with real disturbances. The difficulty of swelling may partly be to blame here ;—during the dry time in summer the seeds again become dormant. On the other hand water may have permeated them already and have given rise to the formation of ferments, which lead to the mobilization of the reserve substances. But this action of the ferment is in itself too slow, up to the beginning of the dry summer period, to sufficiently nourish the embryo. In different individuals and varieties of all species which germinate with difficulty, germination and development is found the spring following autumn planting. This takes place especially if the seeds are sown soon after harvesting and when possi- ble with the entire fruit. “Stratification” has been proved still more effec- tive, i.e. the placing of the seed in layers in vessels filled with sand for the 1 Galter und Klose, Quellungsunfahigkeit von Kleesamen. Wiener landw. Zeitschr. 1877, No. 17, cit. Jahresb. f. Agrikulturchemie, XX. Year, 1877, p. 181. > 2 Dobner’s Botanik fiir Forstmianner, 4th Edition, revised by Nobbe, 1882. p. 382. 108 winter. The actual disturbances are found to be the lack of external con- ditions necessary for germination. Besides moisture and warmth there be- long here the unimpeded supply of oxygen and the observance of the time when the seed is capable of re-acting. The time within which the seed responds to the action of the external conditions necessary for germination by a normal transmutation of the re- serve substances and the development of the embryo varies greatly, for the different families and species, even for individuals of the same variety. It is well-known that seeds of willows, poplars and elms must be sown im- mediately after harvesting, since they lose their power of germination after a few days or weeks, while cucumbers and melons often give stronger, more fertile plants, if the seeds have been kept for a year. To be sure, the seeds of many of our fruit and forest trees usually germinate after one or more years, but the number of the slow growing, weakened specimens increases with the age of the seed. Oxygen should be considered the most important factor next to water, necessary for swelling. For germination the seeds never need as much water as their substance can take up; the vegetative activity of the seedling begins before this time’. If in the beginning there is a scarcity of water which can be taken up endosmotically, the seed also takes water up hydro- scopically from the atmosphere*®. Water vapor also condenses on the outer surface; in fact, after the manner of all porous bodies, it condenses also hydrogen, nitrogen oxygen and other gases. Dehérain and Landrin® found that the swollen seeds take up comparatively more oxygen than nitrogen from the atmosphere so that more nitrogen remains in the en- closed space. After three days the seed begins to give off carbon dioxid and this increases so fast that soon more carbon dioxid is present than the oxygen enclosed in the volume of the air would warrant, the oxygen has gradually disappeared. The excessive production of carbon dioxid is therefore to be considered as a product of the processes of oxidation of the inner burning, beginning in the seeds. These authors pictured to themselves the beginning of the chemical actions in the seed in such a way that the rapid condensation of the gas de- termined at first for the various seeds will necessarily free the latent warmth of the gas and this warmth sufficiently increases the temperature of the en- closed oxygen so that oxidation can begin. With this is given the impetus for the normal solution of the reserve substance of the seed; the heat, freed by oxidation, favors these processes more and more and they become evident externally by the production of carbon dioxid. 1 Jahresb. f. Agrikulturchemie, 1880, p. 213. 2 Hoffmann, R., in the Jahresbericht der agrikulturchemischen Untersuchung- station in Béhmen, 1864, p. 6. and Haberlandt, F., in Zeitschrift fiir deutsche Land- wirte, 1868, p. 355. Both works may be found in abstract in the Jahresb. f. Agrikul- turchemie, Jahrg. VII. 1864, pp. 108 and 111. 3 Compt. rend. 1874, Vol. LXXVIII, p. 1488, cit. in Biedermann’s Centralbl. f. Agrikulturchemie, 1874, II, p. 185. 109 The preparation for the germination of the dormant seed, according to this theory, is the loosening undergone by the shell of the seed, as the result of its swelling with water. The broken cell layers which have become per- meable for gases now permit their rapid penetration and their condensation therefore gives the first impetus for the process of oxidation which causes the transformation of the reserve substances into diffusible forms. Since it can be observed with the seed albumen of plants that the breaking down of the starch in the seedling begins in the cotyledons in monocotyledons, it can be assumed that the part richest in nitrogen, i.e. the embryonic tissue, under the influence of oxygen will begin the metabolic reactions and by the develop- ment of abundant enzymes act upon its surroundings. The disturbance in the second phase of germination can result only from a lack of oxygen or also from an excess of carbon dioxid. The state- ments of Th. de Saussure confirmed by Dehérain and Landrin show that no gas 1s so detrimental to germination as carbon dioxid. Seeds which are kept in a mixture of oxygen and hydrogen germinate just as in atmospheric air; vet an addition of a few hundredths of carbon dioxid to an atmosphere of oxygen is enough to absolutely inhibit germination, when only the little roots have appeared. If the amount of carbon dioxid is very considerable seeds will not germinate. Carbon dioxid in excess is very injurious to other dormant parts of the plant. Van Tieghem and Bonnier' found in bulbs and tubers (Tuli- pa, Oxalis crenata) which respired further in air containing a great deal of oxygen, and therefore, produced carbon dioxid, that they formed alcohol in an atmosphere of pure carbon dioxid. Tulip bulbs which had been kept for a month in air free from oxygen were suffocated and remained without fur- ther development. When seed has been sown too deep there is also an excess of carbon dioxid and a lack of oxygen. The thick soil covering brings about injuries and hinders the germination of the seed but can not, however, be expressed in definite figures. Aside from the different requirements of the different species, the optimum thickness of the covering differs for the same species according to the composition of the soil, the amount and distribution of pre- cipitation etc. On this account the results of the experiments often under- taken to ascertain the best depth for sowing differ from one another as soon as a definite statement of figures is undertaken. They all agree, however, that in doubtful cases it is better to sow with too shallow a covering than too deep. The purpose of the covering is to hold the young seed firm and to retain a sufficient degree of moisture. The shutting out of light comes less under consideration. The retention of sufficient moisture for germination must be primarily considered. If enough is present, the roots themselves will pene- trate at once into the soil even when the seed lies superficially. On this ac- 1 Bulletin de la société botanique de France, Vol. XXVII, 1880, p. 83, cit. in Wollny’s Forschungen auf dem Gebiete der Agrikulturphysik. 11 10) count a perfectly superficial sowing of the seed would be advisable if periods did not occur in spring which dry up the surface of the soil to such an ex- tent that a temporary or even a permanent inhibition of the life activity takes place in the seedling. The more porous the soil, the greater is the danger of drying out and therefore the greater the depth at which the seed must lie. In regions where the spring is dry a heavy soil will give a more uniform germination even if the sowing is shallow. The same soil and the same depth of sowing become dangerous when strong rainfall and great heat alternate rapidly and form crusts on the upper surface of the soil cutting off nearly all access of air to the seeds then in a most active stage of metabolism. The air enclosed in the seeds does not last long. Ventilation of the plant body is, however, absolute- ly necessary, even the germinating seed suffers extremely if the air contained in it be removed. The formation of heavy crusts on the soil can make the depth of sowing of the seed become the cause of considerably injury, which in itself would not be injurious. How much the lack of air influences the germination capacity of seeds is evident from de Vries! citations. In this connection Haberlandt injected curly beet seeds with water under an air pump and observed that the seeds took up 71.13 per cent.; of these seeds thus partially deprived of air only 30 per cent. germinated as against 90 per cent. of the normal seeds kept as a control. In a second experiment all the air was replaced by water forced in by the air pump and only 8 per cent. germinated as against 72 per cent. in the control. Also the time required for germination was shorter in the normal seeds. It may well be assumed that the removal especially of oxygen from the seed and the hindered diffusion of this gas in new quantities into the intercellular spaces is the cause of the loss in germinating power. Dutrochet? found even in mature plants that death often occurs if water is injected. In the rapid thawing of frozen fleshy parts of plants which, as a result of an infiltration of the intercellular spaces with water, have a glassy, translucent appearance, the exclusion of the air from the cells by water may contribute essentially to their death. From the many experiments carried out practically in order to obtain precise numerical values for the best depth for sowing seeds, those of Roes- tell, Tietschert, Ekkert and Wollny are the most thorough. Roestell® gives 2 to 4.5 cm. as the most favorable depth for porous, strong, field soil. Tietschert* experiments endeavor to determine the maximum boun- daries of the most favorable seeding depths in soils differently con- structed physically ;—r1o cm. was seen to be the rational maximum depth for 1 De Vries, Keimungsgeschichte der Zuckerriibe, Landwirtsch, Jahrb. v. Thiel S79) pee 20! 2 Dutrochet, Mémorires ete. édition Bruxelles p. 211, cit. by de Vries 1. c. 3 Annalen der Landwirtschaft, Vol. 51, p. 1. 4 Tietschert, Keimungsversuche mit Roggen and Raps. Halle. 1874. Tolar sandy soil, 8 cm. for humus soil and 5 cm. for clay and loamy soil containing lime. The last two kinds of soil suffer from dry weather so that shallow seed- ing gives poor results. The experiments repeated later in the year (August to September) gave for all kinds of soil a depth of 2.5 cm. as very unfavor- able because of drought; in this case clay soil was proved most favorable in seeding at a depth of 10 cm. It is evident from this that definite figures must be accepted with great reserve. [kkert' experimented with rye, oats and barley, in loam, in pond slime (silt), in sandy soil and garden earth. In seeding rye in separate wooden boxes no difference in the growth of the plants was shown between 2 to 8 cm. of covering (as a result of uni- form ventilation from all sides). In experiments in the open ground stem formation seemed more favored by a lesser depth of the seed, yet this refers more to the time of the appearance of the sprout than to its quality. Odats and barley survive a deeper sowing than does rye. In summer a deeper sow- ing of the seed is better than in winter. The minimum covering for grain may be 1.5 to 2 cm.; the maximum favorable for results is 6 cm. Later experiments of the same author? bring another important factor into consideration which for the same soil acts as a modifler of the favorable depth for sowing. The quality of the seed is at times decisive. The quality of wheat seed, however, with which the first experiments were made did not seem to have any influence on the capacity for germination but the development of the young plant with equal depth of sowing was better, the better the quality of the seed. With a medium 5 cm. depth of sowing (experiments with sandy soil) all qualities gave the longest straw and the longest heads. The relation of the weight of the grain yield to that of the straw is lower, as the seed is poorer and the sowing deeper. Experiments with barley confirmed the results obtained with wheat; the less the depth of sowing and the better the quality used for the same depth the earlier the seed sprouted. The sum of the sprouted plants was no less with inferior seed but the influence of the depth of sowing was so felt in this quality that a shallow sowing gave a much longer straw. In general it must be said that the depth of sowing, conditions otherwise being thought equal, will influence first of all those developmental stages which are connected with the early stage. However, the quality of the grain depends upon the early develop- ment in the number of sprouts and the length of the heads as well as the for- mation of the young heads and is therefore influenced by the depth of the sowing. On the other hand the quality of the harvested grain depends upon the nutritive and weather conditions of the current year, and will therefore be scarcely more influenced by the first development or inherited peculiarity of the grain. 1 Ekkert, Ueber Keimung, Bestocking und Bewurzelung der Getreidearten etc. Inauguraldissertation. Leipzig 1874. 2 Ekkert, Kulturversuch mit Weizen und Gerste verschiedener Qualitat etc. Fuhling’s Landw. Zeit., 1875, Part 1; 1876, Parts 1 and 2. 112 Soaking of the seed, which has often been recommended. for light soils when the time for seeding has been continuously dry, should be used with due care. If the weather becomes dry and the water which has been taken up in swelling is not enough to make the primary rootlets grow into the soil, then there is an unavoidable interruption in growth. This is the explanation of Wollny’s discovery: that soaking produces plants maturing later. Wollny’s? studies on the suitable depth of sowing are most thorough; he determined for grain that sowing 2 to 3 cm. deep furnishes the Fig. 9. Rye seedling with too deep sowing of the seed grain. Hlevation of the node of the sprout near the surface of the soil. (Orig.) best results in yield. Over and above this a noticeable retrogression is found already especially emphasized by Jorgensen*. The last named author also found rye to be the most sensitive and wheat the least sensitive. For most of the Leguminoseae the depth of the sowing is less important. In con- trast to this, varieties of clover and rape have been proved very dependent 1 Bot. Centralbl., Vol. XXX, No. 15, 1887, p. 48. 2 Wollny, Saat und Pflege der landwirtschaftl. Culturpflanzen. Berlin, 1885. 3 Jorgensen, S., Versuche iiber das Unterbringen der Saat ete. Annalen d. Landw. in d. Kgl. Preuss. Staaten. Wochenblatt 1873. No. 11. 113 upon the depth to which the seeds are covered. It seems desirable to have this still less than for grain (0.5 to 2.6 cm.). Wollny’s experiments showed that in dry years a deeper earth covering was more advantageous, in wet years, a lighter one. Corresponding to wet and dry weather the time of har- vest was retarded with an increasing depth of sowing, the number of plants, which germinated at all and still more, the number which came to harvest, was decreased. But it must be emphasized again and again that precise figures for the most favorable sowing in the different localities can be collected only directly by the local agriculturalist since not only the composition of the soil and the weather but also the character of the variety must be con- sidered in the matter, as has been shown by Stossner'. This same holds good for tubers, bulbs and pieces of roots which are used for seeds. In these the soil conditions have an especial weight because these fleshy organs which are rich in water are essentially and quickly in- fluenced by the soil supply of oxygen. For potatoes, experiments by Nobbe? and Kithn? have shown that in questionable cases the more shallow sowing will be the most advantageous one. In the forcing of bloom- ing bulbs excessive losses arise at times from the fact that the bulbs (hya- cinths) have been planted too deep in the pot, or when in the pots are cover- ed too deep with earth after the rooting has been sufficient. Especially if the soil covering is heavy and damp and the bulbs have not matured sufficiently the year before on account of wet weather, the “Rotz” (see this in Vol. IT.) usually appears very easily. The automatic regulation of the depth of sowing on the part of different plant races is interesting. In grasses, and in fact, best seen in our grain species, the first internode is the part which is destined, when the seed grain has been sown too deep, to push the second node which hides the stem eye and the side buds, i. e. the node which forms the stem, into the porous, well ventilated upper layer of soil. In the adjoining figure 9 we perceive the seed grain which is already almost empty and its weakly retained (primary) roots which had been formed in the grain. From the seed grain the first (over-elongated) internode has pushed the second node nearly up to the upper surface of the soil. In this favorable position the secondary roots, which exist during the whole life of the plant, have been developed, the eyes of the side shoots have attained a further maturity. In shallow sowing both nodes lie close to one another and give in cross-section such a picture as is shown in figure 10. The nodal tissue seems divided radially by browned vascu- lar strands. The vascular-bundle cylinders are those of the primary roots and become diseased during or soon after the formation of the secondary roots. The ground tissue of the node shows the first circle of vascular bundles (q) of the young blade close to the pith shield (m) with its few cells. Branches of these bundles, recognizable from their wide ducts (g’), may be seen fur- 1 Stéssner, Untersuchungen iiber den Hinfluss verschiedener Aussaattiefen etc. Landwirtsch. Jahrbiicher 1887. 2 Nobbe, Handbuch der Samenkunde, 1876, p. 184. 3 Ktihn, Berichte aus dem physiolog. Laborat. Halle, Part L., p. 43. 114 ther out in the axis. This young blade possesses on the side marked ” uniformly connected bark tissue; on the opposite side D, however, the first sheath-formed leaf (sch) which remains colorless, and the bud of the next higher leaf, the first green one (bl), which is completely developed later, lave been differentiated from the bark tissue. In the axis of this first leaf may be seen the meristematic position of the first lateral bud (kn)which pushes out the green leaf lying in front of it with its already clearly developed epi- ?\ q 30) / ‘ | oan Cf ext Miigetersiscsescts RAN \\ ros AA, D 12@s5@ pues eee Ala VET KAA eee vA Fig. 10. Cross-section through the lowest node of a young rye plant. Explanation of lettering in text. (Orig.) dermis (e’); e is the epidermis of the sheath leaf which is already being differentiated from the axis. If the (dotted) tissue of the bud of the first ereen leaf (bl) be traced backward in this cross-section toward the side marked I’ it is seen that this passes over into a colorless tissue ring char- acterized, however, by its comparatively large intercellular spaces contain- ing air (i), the bark tissue of the young blade. It is seen from this that each erain leaf is a direct continuation of the bark of the blade. This bark ring PART II. MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Prof. Dr.G. Lindau 4nd ~~ Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History Berlin in Hamburg TRANSLATED BY FRANCES DORRANCE Volume I[ NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT ney Copyrighted, 1915 By = FRANCES DORRANCE ” | a ; ff (6) a ©Oaiago1186 yf THE RECORD PRESS Wilkes-Barré, Pa. _ E MAY 291915 115 is connected on the side with the tissue of the sheath leaf and it is worth noting that this sheath, even in so young a stage of blade differentiation, must have finished its work since the tissue is entirely impoverished and begins to be full of holes (J). While therefore in the Gramineae the accessory apparatus, which with too deep sowing brings the vegetative tip into the abundantly aérated par- ticles of soil, consists in the elongation (observed up to 9 cm.) of the lowest internode and, in case of necessity, also of the one above it, we find in the Leguminoseae and other dicotyledons a different arrangement. In beans, for example, we notice first of all an increased elongation of the hypocotyle corresponding to the need, so that finally, with very different depths of sow- ing, the growing tip of the stem in all plants is found at approximately the same height. Naturally the strength of the plant from the same kind of seed is decreased as the depth of sowing is greater. The more the hypocotyle must be lengthened, in order that its upper part, comparable to the curved back of the burden-carrier, can break through the load of the soil and bring the cotyledons to the light, the more reserve substances will be used up. It is therefore very evident that plants coming from greater depths are weaker even if they have not lost reserve substances in the seed through strong intra-molecular respiration. Such will be the case, however, if continued wet weather sets in after too deep sowing so that a shortage of oxygen results. The experiments by Godlewski and Polzeniusz! show what amounts of reserve substances can be !ost through intra-molecular respiration and the formation of alcohol. Sterilized peas, in evacuated air, produced in the first period almost as much carbon dioxid as in normal respiration in the air. The whole amount exceeded 20 per cent. of the original dry substance of the seed. The amount of alcohol formed corresponds to that of the carbon dioxid. Only during the sixth week did the production of carbon dioxid cease in the peas which lay in sterilized water and up to that time possibly 40 per cent. of the dry substances present had been broken down to alcohol and carbon dioxid. This is also the case in grains. In grains the action of the secondary roots on the nodes of the stem counteracts this weakening. In legumes a similar process of self assistance can now take place, since, as Wollny proved, adventitious roots are formed from the over-elongated hypocotyle member. He observed this on the parts of the stem which had been covered with soil, not only in field beans, but also in peas, sweet peas, lentils, lupines and plants of other families,—rape and sunflowers. But the legumes often are not capable of using such an accessory apparatus since, with normal depth of sowing and capacity for germination, they easily suc- cumb to other dangers which will be described in the section on “condition of hard shells.” 1 Godlewski und Polzeniusz, Ueber Alkoholbildung bei der intramolekularen Atmung hGherer Pflanzen. Anzeig. Akad. d. Wiss. Krakau, cit. Bot. Jahresb. 1897, p. 142. 110 Roots From THE Tip OF GRAIN SEEDS. It seems best to add here an account of a case which, because of its peculiarity and rareness, deserves a permanent place in science. The agricultural teacher, Wolfes in Dargun (Mecklenburg-Schwerin), sent me in 1876, fourteen wheat grains in which, through hypertrophy, the embryo did not lie to one side of the endosperm, but occupied a middle position. The grains were sown in the fall and in the spring they had partly rooted but without developing plumules. They were either slender, pear- shaped or even cylindrical at the one end, tapering rapidly at the other like the neck of a violin. In many grains (Fig. 11-12) the elongation of the slender end opposite the embryo was so marked that a neck was formed, possibly 2 to 3.5 mm. long, and twisted toward the upper end. In twelve grains the length of which varied from 34 to 1% cm. the neck bore a large number of very thin, thread-like roots 1 to 2 cm. long, closely arranged like a brush. These were pubescent almost their entire length. Upon attempting carefully with a needle to raise the wrinkled and oc- casionally ruptured testa of the grain it was found to be closely attached to Fig. 11. Wheat grains with roots not originating from the embryo but springing from the hypertrophied testa at the tip of the seed grain. the grain in different places and, when broken off, was usually of a darker color. On the other hand its upper part was firmly connected with the beak- like growth along almost its whole length and could be raised from the grain proper like a straw cap (Fig. 12). The neck therefore at the time of the investigation was not connected with the actual grain except by the testa from the substance of which it also seemed to be formed. In the fresh con- dition of the grain this had been firmly set on the seed since various concave places on the inner wall of the cap, perceptible through the microscope, fitted on to the small convex elevations visible on the seed grains. There was another equally noteworthy phenomenon, namely, that the fissure, normally present, was lacking in these wheat grains. The grain, which had been dug up, also failed to show the seedling which hes at the base of the normal grain and is easily recognizable through the seed coat; it was not noticeable in the seeds observed. The endosperm itself, when cut apart, finally showed only a small degree of the white color of the healthy grain. There were long, glassy, translucent and yellowish streaks extending from the edge.inward. It hada rancid odor. The blue iodin reaction for starch was strong only in those particles of the grain which, on the freshly cut hay is Ys ie me Many ees ‘l ne / ) ah } ss I ay ORAS Masenarcicedsciuy’ Yo Fig. 12. Wheat grain with hypertrophied testa and root formation at its tip. Embryo central instead of lateral. Explanation of letters in the text. 118 surface, were found to be white and mealy, while on the glassy places there was only a slight reaction. The glutinous layer in the Mecklenburg grain was not developed at all, the thin seed shell only incompletely. In place of this glutinous layer (Fig. 12 k) a plate-like parenchyma was found, the content of which did not differ essentially from that of the underlying tissue. The most striking thing connected with this abnormal wheat grain was, however, the position of the embryo on the opposite end from that which bore the roots (Fig. 12 w) and exactly in the middle of the grain (as in Typhaceae) equally surrounded on all sides by the tissue of the starch- containing endosperm. While in the normally constructed wheat grain the seedling lies without, at the base of the grain, and is connected with the endosperm by a special organ, the scutellum (the cotyledon), the seedling lies here (Fig. 12 e) without cotyledons in a central cavity (Fig. 12 h) of the grain. This cavity in some of the grains is elliptical, in others triangular. In some it extends possibly to the middle of the grain, in others, becoming narrower and narrower toward the top, it reaches to the tip, even penetrating into the tissue of the cap. On the inner side it is lined with a layer formed of two plate-like rows of cells of a glutinous content (Fig. 12 a) which clearly resembles the glutinous layer deposited in healthy grains outside* the endosperm. The young leaves of the seedling, folded over one another, show no essential variation. On the contrary, the number of secondary roots formed in whorls at almost equal distances (Fig. 12 7) steadily increases up to 6 to8 and these roots appear to be covered by a parenchymatous layer arranged in the manner of cork cells, 6 to 8 cells thick and free from starch. On this tissue lies the combined and modified seed coat (Fig. 12 sf) which in dry grain becomes thicker walled with more abundant cells toward the tip and develops imperceptibly into the cap which the root bears at its tip” (Ei1g5 12> ww) The vascular bundle is continued into the cap from the roots. Here are often found several bundles united at the tip of the cap into a ring-like, thicker network of ducts running horizontally and resembling a node of the stalk. Still further back from the tip these vascular bundles (Fig. 12 g), iso- lated near the outer edge of the inside of the cap, are seen to run backward (Fig. 12 gg). The endosperm normally has no fully developed vascular bundles and the cotyledons only embryonic ones. Here, however, the vas- cular bundles take an often irregular course through the endosperm and, in the individual grains, surround the seedling in a semi-circle and have not developed even though the grains lay in the soil over winter. By cutting cross-sections from the diseased grains and submitting them to microscopic investigation, the probable cause of this striking mal- 119 formation was seen at once. The inability of the seed covering to free itself entirely from the grain was due to a connected firm, homogeneous, some- what dark mass (Fig. 13); the presence of thick, much ramified mycelial threads, often provided with short skein-like groups of branches, could be proved. The threads of the colorless, strongly refrac- tive mycelium grew trans- versely through the very thick walls (Fig. 13 m) of the fruit cells and seed coat which had been merged into one another. The mycelial threads grew more thickly when the cells were richer in content and thinner wall- ed, entirely filling some cells of the endosperm (Fig. 13 mm). Near such places the starch had been dissolved and the cytoplasm had be- come solid as if it had been dried. In other cells a firm network of protoplasmic material scarcely distinguishable from starch could be seen. These were almost imperceptible in the starch grain but yet were there. This substance was apparently deposited about the starch grains but upon examination there were no grains present, only the corresponding cavities. In some such way originated the yellow- ish, translucent places between which lay groups of cells especially rich in starch. These mixed regions gave the proper iodine reaction under a weak magnification. Fig. 13. Hypertrophied testa traversed by mycelia. The variation in the structure of the diseased grain is best shown by compar- ing figures 13 and 14. The latter repre- Fig. 14. Normal fruit and seed sents a section from a corresponding Boca ae ies ore part of a healthy gain. The seed coat (Fig. 13-14 fs) in the diseased grain is more than three times as thick as in the healthy grain. In the abnormally developed seed coat there is a com- pletely developed vascular bundle with a clearly recognizable sheath (gs). In the diseased grain the growing fruit membrane passes directly over into 120 the endosperm (e), and in the healthy one the gluten layer (Fig. 14 k)lies between the two tissues. ; Investigations of such grains in the “imported” seed show a similar condition. The seeds seem malformed and the fact that the malforma- tion manifests itself in the position of the embryo as well as in the develop- ment of the endosperm and especially in the thickened growth of the seed coat proves that this malformation must have been completed when the grain was forming in the head. Fertilization has nevertheless taken place normally since the embryo displays leaves and growing point as well as roots (the latter in increased numbers). But some local stimulus must at once have incited a cell increase in the fruit tissue and thereby displaced the em- bryo from the side towards the middle of the endosperm. This stimulus was active during the whole development of the seed and increased the vege- tative activity so that the character of the endosperm underwent a change, for the vascular bundles are those of a vegetative axis. We observe a most important numerical increase of the cells in the tips of the seed, assuming the character of a vegetative axis and, by means of the entangled vascular bundles, resembling a stalk node. Abundant roots develop at these stalk nodes ‘and it is not improbable that leaf buds might have begun had there been a greater aeration of the soil layers. We would then have had a case similar to that in dicotyledonous plants when, as has often been observed, vegetative axes develop from their fruit nodes. .For such processes, however, the seed lay too deep. There was no ac- cessory apparatus for raising the seed to the upper surface of the soil, such as the elongation of the first internode in the seedling. As a result bacterial decomposition followed, due to the lack of oxygen, as was shown by the rancid smell of butyric acid. This is the reason for mentioning the present case here. Had it been possible to determine exactly the causative fungus the case would have be- longed under parasitic diseases. As it was impossible to make the my- celium fruit, the case becomes hypothetical as to the nature of the parasite. Only one thing is certain—viz., that the stimulating mycelium did not belong to the black fungi (Cladosporium, etc.). According to Brefeld’s latest in- vestigations on the penetration of the smut into the blossoms, it is highly probable that the smut spores, which have entered the blossom, germinate soon after the fertilization of the grain, and by the slow advance of their mycelia have exerted the stimulus on the seed coat. 3. GREATER HorIzoNTAL DIFFERENCES. The individual development within the same plant species is influenced by horizontal changes in the place of cultivation from north to south, or east to west, as well as by the vertical elevation of the habitat. De Candolle? laid ’ 1 Sur la méthode de sommes de température appliquée aux phénoménes de végétation. Separatabzug der Bibliothéque universelle de Genéve 1875. 121 down the principle that with approximately equal latitude and elevation, the temperatures above O° in shade are higher for the same developmental phase (time of blossoming, defoliation, etc.) in the western parts of Europe than in the eastern ones. Observations show that in Europe the length of the growth period decreases toward the northeast and increases towards the southwest. Because of the many mountain chains and plateau-like inter- ruptions the phenomenon is less clearly evident in western Europe than on the great level plains of Russia. Kowalewski’s' very remarkable work re- ports on this phase. This is based on the statements of 2200 agriculturalists scattered throughout all parts of European Russia, who had reported the time of sowing and harvesting of the grain. Since cultivation must be adapted to climatic conditions, the usual times for sowing and harvesting show the existing vegetative conditions. The sowing of winter rye takes place in the southern part of the Gov- ernment of Kherson on the 15th of September’, at Archangel, on the first of August. The localities of simultaneous plantings of winter rye do not run parallel to the degrees of latitude, but are inclined from N. W. to S. E.; therefore, they run almost in the same direction as do the isocheims. The difference in the time of harvesting winter rye in the far north (Archangel) and in the south (Kherson) extends, like the time of sowing, over a month and a half. The seeding period for summer grain in the far north is one- third to one-fourth as long as at the southern limit. At the western it is two to two and a half times longer than at the eastern. The time of harvesting in the north is likewise one-third as long as in the south; in the west once and a half to twice as long as in the east. The localities of simultaneous ripen- ing of summer grain run from S. W. to N. E., corresponding therefore in their direction with the isotheres. The growth period in southern and southwestern Russia is only 85 to t10 days for rye, buckwheat, flax and barley,—but 110 to 125 days for sum- mer wheat, millet, oats and peas. Sugar beets, maize and potatoes have the longest growth period,—150 to 165 days. Thus, in the south, the longest growth period is almost twice as long as is the shortest. On the other hand, in the north, the periods concerned are not only shorter everywhere but are also more simultaneous. In the far north and northeast the difference be- tween the longest and the shortest growth periods does not exceed 10 to 20 days. For the same cultivated plant, in European Russia, the rate of develop- ment increases on the average with the latitude. Thus, for example, oats in the Government of Kherson (south) have a growth period of 123 days, wheat and barley one of 110 days. In the north, however, (Archangel) the growth period of oats decreases to 98 days, that of wheat to 88 days, of bar- 1 Kowalewski, W., Ueber die Dauer der Vegetationsperiode der Kulturpflanzen in ihrer Abhingigkeit von der geographischen Breite und Lange. Arb. d. St. Peters- burger Naturforscherges., XV, 1884 (russisch), cit. Bot. Centralbl., 1884, No. 51, D730. 2 All dates are given old style as still used in Russia. {22 ley to 98 days. In the same geographical latitude, a longer vegetation period is found in the west than in the east. The causes of the shortening of the growth periods, therefore, cannot lie in the warmth which the plants receive at a corresponding degree of lati- tude, for otherwise the plants in the south would have passed through their development considerably more quickly than in the north, also since the southern black soil is raised to a higher temperature than the heavier, often clayey and damp soil of the north. Besides this, the lack of moisture in the south hastens maturity very greatly. Some other factor must therefore be determinative. Kowalewski states this to be the length of the insolation. He now assumes May 5th to be the mean time for sowing oats and August 2oth as the mean time for harvesting them, finding thereby an insolation period of 2000 hours for the 98 days of vegetation in Archangel. If the period of bright nights be added to this, there is an increase amounting to 2240 hours. Kherson oats are sown on March 20, harvested on July 2oth. In this 123 days of vegetation, however, only 1850 insolation hours obtain. Further, as Kowalewski says, it must be noted that the cultivated species of the north are adapted to a lesser degree of warmth. Therefore, when brought to the south, they ripen comparatively earlier. This result agrees with the one found by Schiibelert which will be mentioned later. Similar observations are said to have been made in Canada also. In further explanation of the change in the length of vegetation, Kowa- lewski brings forward the greater intensity of illumination, the small cloud masses and the greater humidity of the atmosphere and, supported by Fa- mintzin’s investigations, he believes, for example, that the light optimum for assimilation is exceeded in the south and therefore has a retarding in- fluence. This would correspond to the yellowing of the shade-loving plants, when grown in high mountains. It is not necessary to fall back upon the theory of the retarding action of the southern excess of light, if Wiesner’s theory be accepted. In explaining the utilization of light on the part of plants in the far north, Wiesner? emphasizes, according to his investigations, the fact that in regions of the far north (Troms6), with an equal elevation of the sun and an equal clouding of the sky, the chemical intensity of the daylight has been shown to be greater than in Vienna and Cairo, but less than in Buitenzorg in Java. The light factor of the far northern regions is dis- tinguished in its illuminating quality by a relatively marked equability which obtains in no other locality where plants flourish. The plants of the arctic vegetative zone receive the greatest amount of light as a whole. Here, in the low growing plants there is no self-shading due to their own foliage, and even woody plants in adjacent southern regions show only a minimum amount of shade-producing branches. 1 Schiibeler, Die Pflanzenwelt Norwegens. 2 Wiesner, J., Beitrige zur Kenntnis des photo-chemischen Klimas im arktis- chen Gebiete. Sitz. Akad. d. Wiss. Wien CVII, cit. Bot. Jahresb. 1898, I, p. 586. 123 Wittmack has reviewed earlier cultural experiments as to the behavior of plants indigenous to any given locality when artifically introduced to a region farther south’. His conclusions follow ;—plants from the.north de- velop somewhat more slowly in middle Europe, catch up later with the in- digenous ones, however, or even exceed them. It is evident, therefore, that the short growth period, which has become habitual in the north, is often still more shortened by the increased warmth of the southern habitat, pro- vided also that the climate be dry. The damp climate of England with its low maximum temperatures retards ripening. The humidity of the air is a iactor of great power and can delay ripening; just as, conversely, regions with great periods of drought, the climate of the steppes and similar con- ditions, not dependent on the degree of latitude, form limited centres where plants ripen prematurely. Too great drought certainly retards development, as has been determined experimentally. Stahl-Schoder’s experiments, cited in the chapter on “Excess of Water,” treat of soil dryness. The period of the in- fluence of heat is very important and is indeed explicable. Heat in July and August is more advantageous than in May and June but the reverse is true for rain. Wittmack’s summary in general shows the significance of the physical structure of the soil in relation to the early ripening ;—that the vegetative time in eastern regions is shorter for the same varieties of grain than in western ones. Based on the observation that the varieties cultivated in northern climates retain their shorter growth period in the immediately following developmental periods, an active trade in northern seed has been developed. Meanwhile the quantity of the harvest should not be lost sight of. Abundant supply of nutrition being uniformly assumed, the quantity depends always on the length of the vegetative period,—i.e., the time of the formation of shoots. The longer time the grain has for the formation of vegetative organs (as in damp, cool seasons) the more abundant is the growth of shoots and with it the formation of a greater number of ears from the in- dividual seeds. If we should carry into the east varieties produced in the west, which are long-lived and characterized by great productivity, we would run the risk of frosts. This is most strikingly true in the English varieties of wheat, from the squarehead group, which toward the east come less and less true to seed, because they winter kill. Experience shows in regard to frost-resis- tance, that seeds from northern regions give plants in southern latitudes which at times not only ripen earlier, in spite of an initial retardation, but aiso better withstand frost. _ From the result of Schitbeler’s? observations, it should be emphasized, that the quick growth, which has become habitual in northern or Alpine 1 Ueber vergleichende Kulturen mit nordischem Getreide, Von Dreisch, Kor- nicke, Kraus, Vilmorin and others, referred to by Wittmack. Landwirthsch. Jahrb. 1875, p. 479, and 1876, pp. 613 ff. 2 Schiibeler, Die Pflanzenwelt Norwegens, 1873, pp. 77 ff. 124 climates because of a short vegetative period, is lost after four or five years of cultivation in lower latitudes. Conversely, long-lived varieties accustom themselves in a few years to a short vegetative period. Yellow chicken maize from Hohenheim, for example, which ripened in 1852 at Christiana in 120 days after repeated sowings, shortened its growth period to the extent of 30 days in 1857. In Christiana the developmental period of barley is 90 days, but seed brought from Alten (the 7oth parallel) needed only 55 days (see Kowalewski). Of the chemical properties developed in a northern habitat, which in great measure correspond to the changes in plants in high elevations, the fact that the sugar content of the fruits decreases toward the north while the aroma increases is of especial importance. Bonnier and Flahault main- tain also that not only the size of the leaves increases in the darkness of the north but also their green color’. Schtbeler’s experiments in summary” give the following special examples:—In wheat brought from Ohio and Bessarabia, the grain became darker in color each year until it was as yellow brown as the native Norwegian winter wheat. Similar results were obtained with maize, beans, peas, celery, etc. Celery taken from a region extending from the Caucasus to Hindustan, grows in Africa (Egypt, Abyssinia and Algeria) and may be found in Europe from the Mediterranean to the Baltic; it now extends even into Finland up to the 69th parallel. There, however, the root stalks are poorly developed;—the aroma, nevertheless, becoming more pungent®. The greater intensity of color in the blossoms, as already men- tioned, a peculiarity shown to correspond with an increasing elevation above sea-level, also appears in most garden flowers as cultivation advances to- wards the north. In regard to the formation of aromatic substances, be- sides celery, juniper may also be cited as an example. In Norway it is much richer in oil than in Central Europe. Onions also and garlic are uncom- monly pungent in Norway. Strawberries are sour but aromatic, while, according to Gétze, they are exceedingly sweet in Coimora, but almost with- out any aroma. Plums often remain so sour that, compared with fruit brought from more southerly regions, they still seem immature. A similar condition exists with grapes as shown by comparing the sweet Portugese grape with the less sweet but aromatic Rhenish grape. In considering the horizontal differences, expressed in the decrease of rainfall and increase of clearness of the air, from the west towards the east, in the conditions of light between southern and northern regions etc., we should not forget one circumstance, to which de Candolle* has already called attention.. This, to be sure, has not been sufficiently verified experi- 1 Bonnier et Flahault, Observations sur les modifications des végétaux suivant les conditions physiques du milieu. Annal. d. sc. nat. Botanique, t. VII, Paris 1879, p. 93. 2 The effects of Uninterrupted Sunlight on Plants. Gard. Chron. 1880, I. p. 272. 3 Hansen, C., Der Sellerie. Gartenflora, 1902, p. 18. 4 de Candolle, A., Sur la méthode des sommes de température appliquée aux phénoménes de la végétation. Archiv. des se. physiques, ete. Nouv. ser. LIII. LIV. Genf 1875, cit. Bot. Jahresber. 1875, p. 585. 125 mentally, but finds repeated substantiation in practical experience. It is namely the greater, more complete dormant period of plants. According to Ihne!, trees which thrive normally in Central Europe and in Coimbra put out their leaves possibly a month earlier in Coimbra and their autumnal change of color occurs about a week and a half later than with us. Thus their dormant period is about six weeks shorter there. The length and com- pleteness of this dormant period, however, must influence greatly the rate of subsequent development. It may indeed be assumed that, with the con- tinuation of a temperature which does not stop the functions entirely, a number of vegetative processes continue with a slow but steady consumption of materials (process of oxidation) and without any compensation to the plant through newly assimilated substances. Besides this, it seems that many enzymes, which affect the energy of metabolism, either succeed in de- veloping to the necessary amount only during a complete dormant period, or are made ready for it. If no complete rest takes place it may be observed especially in the two or three year old bushes and in the buds on branches of woody plants. These are forced earlier and produce weaker organs (smaller leaves, a greater number of sterile blossoms). The increased weight of the seeds in northern latitudes has already been considered. There are, however, some experiments by Petermann* which prove a higher germinating power of Swedish seeds of clover varie- ties, timothy (Phleum pratense L.), and of spruces and pines as compared with German, French and Belgian seeds. The Swedish seeds, which actually, on an average, possess a greater weight, show greater power of germination, not only in the number of fertile seeds which can germinate, but also in the energy with which germination takes place. These results may be explained very well by a greater developmental energy in the plants, due to a more complete winter rest. These observations have a very noteworthy practical bearing in so far as they affect the culture of seeds obtained in exchange. It is not enough merely to introduce seed from other regions, but it will seem necessary to ask above all, what characteristics it is desired to improve in the cultivated plant and in what climates these characteristics attain a higher development. Taken from such localities the seed will then give the desired results. The cultural results, obtained by using plants of other climates, hold good as a rule, however, only for a very few growth periods. Often the in- fluence of the present habitat is felt in the second generation when the plants of foreign importation have assumed the habits of the native varieties. Fruit trees taken from Angers grew and bloomed on Malorka even at the end of February, while the native ones did not blossom until a month later®. A shipment made two years later from Angers showed the same phenom- 1 TIhne, Phanologische Mitteilungen. Cit. Bot. Jahresb. 1898, II, p. 409. 2 Petermann, Recherches sur les graines originaires des hautes latitudes. Extrait du t. XXVIII. des Mémoires couronnés et autres Mémoires publiés par lAcad. Royale de Belgique, Bruxelles, 1877. 3 Gartenzeitung von Wittmack, 1882, p. 374. 126 enon. The fruit trees of the first shipment were now, however, blossoming later, i.e., simultaneously with the native ones. The transition from the hereditary form of growth to the new one determined by the climatic con- ditions is rarely effected as rapidly as it is lost when returned to its former habitat. “Yet, in our vegetables, we have examples of a rapid change in pecularities. In a tropical climate these keep approximately their own char- acter only in the first year. Already in the second year the seeds of these imported plants produce elongated, lignified specimens’. These are our cul- tivated forms which are beginning to vary from the normal. No rapid changes are noticeable in species growing wild, as has been shown by Hoff- mann’s experiments with parallel seeding of certain forms of Phaseolus and Triticum in Giessen, Genoa, Montpelier, Portici and Palermo?. On the other hand, Hoffmann mentions slow changes, first taking place in the course of many generations. Thus Ricinus communis becomes tree-like and perennial in the tropics, in the same way Feseda odorata becomes more or less persistent in New Zealand and, conversely, Bellis perennis becomes an annual in St. Petersburg. Among the changes in mode of growth, which are only slowly com- pleted, belongs the formation of the annual rings in our trees. At any rate the distribution of vascular spring wood and the slightly vascular summer wood within the same degree of latitude fluctuates in each year according to the amount and distribution of precipitation. But in the changes of the average weather, due to changes in latitude, the same dif- ferences become constant and form thereby ecological varieties. Bonnier® treats thoroughly such anatomical differences in the development of the same species in northern and southern positions. He compares examples of the linden, red beech, acacia and others from the region of Toulon (with its 260 days of active growth) with those at Fontainebleau (growth period 178 days) and found that the spring wood develops better in the south, having more abundant, often wider ducts. In this the abundance of precipi- tation in the spring in the Mediterranean district surely has a definite bear- ing. The summer wood of the south, however, is richer in libriform fibres and often consists only of these, while at Fontainebleau numerous ducts are formed, even in summer. The leaves of the Toulon plants were shown to be one-third to one-half thicker and provided with more layers of palisade parenchyma in comparison with the plants grown in the north. The stomata are more numerous, the sclerenchyma is greater and the cuticle strength- ened. The Toulon plants exhibit the character of Mediterranean flora in general. The greater intensity of the color of the blossoms, as the plants advance from the plains to the mountains and from lower latitudes to northern 1 Deutsche Giartnerzeitung, 1883, No. 17. 2 Hoffman, H., Riickblick auf meine Variationsversuche von 1855 bis 1880. Bot. Z., 1881, p. 4380. 8 Bonnier, Cultures expérimentales dans la région méditerranéenne, etc. Cit. Bot. Jahresb. 1902, II, p. 299. 127 regions, has already been considered. Recently attention has also been di- rected to the increased change of color in foliage leaves and its peculiar significance as a protective adaptation has been suggested. MacMillan* treats of these conditions very fully. He speaks of “warming-up colors’ meaning especially the red coloring substances which are more abundantly represented in colder regions. Alpine and arctic plants are more often found with blue or violet blossoms than with yellow; the ends of the twigs are often reddened. The temperature is somewhat raised by the red coloring matter and the influence of cold somewhat weakened. If one thermometer be covered with a green leaf and another with a purple one, while both are exposed to the sun, in a short time the thermometer protected by the purple leaf shows a rise of 6° to 10° of temperature. In the same way he found that a thermometer, stuck in a bunch of violets, shows a higher temperature than one in a bunch of cowslips, after an equal exposure to the sun. The autumnal coloring may be conceived as a definite reaction of the plant to the lowered temperature. The plant provides warmth for itself in its red coloring matter. On this account so many spring flowers are red and violet and autumn flowers blue or red. In warm climates plants often assume peculiarities directly opposite to those of arctic or alpine plants. In tropical plants the storage cells are less strongly developed than in related species from colder regions. The buds are less protected, pubescent coverings more rare on leaves and twigs (with the exception of desert plants). Many winter habits disappear. There are fewer biennials. The warming-up colors recede more and more, while white, yellow and spotted blossoms (Orchids) predominate. Nature would develop red coloring matter to prevent loss of the super- fluous light and to transform it into warmth and to use it as a stimulus to growth. We cannot support this theory of the premeditated utility of the red coloring matter as an apparatus, producing warmth and weakening the light, even if we had such an inclination. If the red coloring matter has once been produced, it will be effective in the way given. The idea that the plant can produce it as a protection against cold, when the temperature be- comes lower, is not plausible, because in the hottest summer temperature leaves can be reddened. In the Rosaceae which are rich in tannin (Crataegus, for example), I have been able to produce the red autumnal coloring after a few weeks in the middle of summer by girdling the twigs. The fact that in summer the underside of many leaves, when reversed, becomes red within a few days is universally known. Parasites furnish further instances. On the same cherry tree, for example, the leaves of branches attacked by Exoacus Cerasi turn glowing red, while the healthy ones remain green. In many spot diseases the circular fungus centre appears surrounded by red. Amaryllidaceae, whose leaves die down in summer (Hippeastrum etc.). develop carmine spots and stripes. "1 MacMillan, Conway, Minnesota Plant Life Saint Paul, Minnesota, 1899, p. 417. 128 Thus we believe that the red coloring matter may be looked upon as a necessary reaction of the cell to the influence of different factors connected with a relatively over-abundant supply of light. One of these factors may be the lowering of the temperature due to a change in the latitude or longi- tude of the place of growth. If we look back to the many changes undergone by the plants in their morphological and chemical structure because of any change in latitude of the place of growth, we cannot shut our eyes to the conviction, that not in- frequently in these changes of place may be sought the reason for a predis- position toward disease or, on the other hand, toward greater immunity. We have mentioned that the western squarehead wheat grown in eastern regions has greater susceptibility to frost and now remind the reader that parasitic diseases may also be dependent on the different mode of development of the host plant inherited in the seed. One should con- sider, for example, the fact that many parasitic fungi appear or are especial- ly abundant at definite periods. In case such fungi only attack young leaves, the presence of young leaves when the spores are ripening will determine an epidemic. The rapidity with which a plant passes through its develop- mental cycle in any given climate is a determining factor in this question. If it develops slowly, its leaves are young and remain susceptible for a longer time, giving a greater danger of fungus infection. If a variety matures quickly (for example, one introduced from more northern or eastern regions) then the leaf may be fully matured at the time of the actual distri- bution of the spores and therefore be resistent to many parasites. Such circumstances deserve greater consideration than has been given them as yet. They will also be a factor in the discussion of the “biological races’ of individual parasites, for it is most probable that often infections of the most closely related host species fail because the host plant at the time of infection is already in an advanced developmental stage, in which the leaf is more mature, i. e., has thicker walls and less cell-content. The fact that the fungus infection is connected with a definite developmental stage of the host plant is shown, for example, in the rust fungi of grains. Eriksson" states that the rust occurs earlier in the varieties ripening early and recent observations show that the different forms of Puccinia have defi- nite periods for attacking grain. Thus it was shown in 1904? that Puccinia glumarum appeared first and foremost in wheat, then followed P. dispersa which, however, attacked only those organs and varieties which were still immature. Later, slowly ripening varieties of wheat were found badly at- tacked by P. dispera and slightly by P. glumarum, while the converse is true for varieties maturing early. P. graminis was found in stored grain. 1 Eriksson, J., Sur l’origine et la propagation de la rouille des céréales par la semence. Ann. scienc. nat. Bot. VIII. sér, Vols. XIV. and XV. Paris 1902. 2 Jahresb. d. Sonderausschusses f. Pflanzenschutz. Deutsche Landw. Ges. 1905 Getrciderost. GLASSY GRAIN KERNELS. These must also be considered as the result of climate influences. Grains are called glassy when their endosperm is hard, almost trans- lucent and grey or reddish in cross-section, while in the normal mealy kernel the endosperm appears soft, white, porose and easily friable. . _ This glassiness of the kernels occurs usually more abundantly in the north and east of Europe than in the west, which fact points to the influence of atmospheric dryness with a higher light intensity. In damper, western regions the vegetative organs obtain a greater ascendancy. Thus Lieben- berg! states, for example, that the otherwise excellent northern barley has two disadvantages ;—viz., too large a percentage of glassy grains and too dark a color which is caused by rain falling on the grain when ready for harvesting. These gusts of rain at harvest time naturally play no part in the development of grains which mature during the dry season. With the lengthened light action, varieties of rye also become intensively colored. The same author reports that at the grain exhibition in Sweden, the oat samples, on an average, possessed only 22.66 to 32.04 per cent. of chaff by weight, while in the Austrian and French varieties it fluctuated between 25.23 and 38.37 per cent. In general there is truth in Haberlandt’s’ state- ment, that a continental climate produces glassy grains, but that, on the other hand, cool, wet summers or an artificial abundance of nutritive sub- stances and water produce mealy, specifically lighter grain kernels, poorer in nitrogen. The glassy condition of the grain, according to Gronlund’s* investiga- tions on mealy and glassy barley, exists in the fact that the cells of the albu- men in the mealy grain which contain the starch show that the spaces between the starch cells are filled with cell-sap, while in the glassy grains these spaces are filled with protoplasm. Johannsen’s* work assumes a greater air content not only between the walls of the mealy grains, but in their whole mass. In germination, the glassy grains become mealy. Ac- cording to Gronlund, who, moreover, acknowledges no relation between weather and the production of the glassy conditions, glassy kernels germi- nate more easily and better and give stronger plants. Although he assumes as incontestible that glassy kernels may be produced from soil containing much nitrogen, yet he believes that poorer, sandier soil, poorly cultivated, pro- duces this peculiar formation much more certainly. He found that mealy grain was produced by pure potassium fertilization. Moreover, both forms occur at times in different stages in the same head. I would like to assume for the production of glassy kernels that the process of starch formation is 1 y. Liebenberg, Bericht tiber die allgemeine nordische Samenausstellung etc., 1882, cit. Bot. Centralbl.. 1882, No. 43, p. 115. 2 Haberlandt, Die Abhingigkeit der Ernten von der Gréfse und Verteilung der Niederschlige. Oesterr. landw. Wochenbl., 1875, p. 352. 2 Nach einer Preisscheift des Verf. cit. im Jahresbericht f. Agriculturchemie XXIII (1880), p. 214. 4 Allg. Brauer- und Hopfenzeitung, 1884, Nos. 78 and 79. 130 shortened in sandy soil, which dries quickly, and, since potassium makes the corn mealy, I would much sooner believe that the action of the potassium is stopped too soon and indeed because other processes, viz., those of ripening, take place too early and too intensively. This will happen much more quickly with strong action of light and warmth and when the water con- tent is less. Sanio’st statement that in East Prussia the glassiness of wheat is due to its becoming overripe on the stalk supports the theory of the predominance of the ripening process at a time when starch formation should be taking place. This opinion is analytically supported by R. Pott’s investigations? who found on an average a higher percentage of ash in glassy varieties of wheat than in mealy kernels. The kernels, in the too rapid ripening, had not completely consumed the mineral substances in forming organic substances. Compare here the high percentage of nitrogen in the grains of oats plants, which suffered from a scarcity of water or from its excess (see chapter, “Excess of Water”). Petri and Johannsen* have made investigations which throw much light on the nature of glassy kernels. The former, as early as 1870, stated that glassy kernels, when softened by water, become mealy and the latter substantiated this observation. Two hundred kilos of barley. were moistened with half that amount of water, until they had taken up 15 per cent. They were then dried immediately, spread and turned until the original weight was again obtained. The percentage of mealy kernels now was 50 per cent., while in the original material it amounted to only 19 per cent. In cultural experiments it was found that, in early seeding, a mealier barley, poorer in nitrogen, had been formed, while in later sowing the harvested product was richer in nitrogen. This discovery indicates that in this glassiness of the kernels there is only a mechanical difference, which develops if ripening is very much hastened by a scarcity of water with an excess of light and warmth. A gradual ripening process gives a longer time for developing an increased starch content with the retention of a larger water content in the substance which is later partially replaced by air. This refers especially to the protoplasm in the endosperm cells. The starch grains lie embedded in this. With quick ripening, the cytoplasm sticks close to the starch grains, making the kernels appear glassy. With slower ripening and greater water content the cell is more loosely constructed, while between the starch grains more cell sap and later more air are present, and then, because of the larger intercellular air spaces, the grain is opaque and mealy. As the protoplasm predominates, the tendency is toward glassiness, and on this account, even normally, the outer layers of the seed, as, for example, in maize, are glassy, the inner ones mealy. These conditions explain Schindler’s observations* that, in wheat grains, mealy and glassy portions can alternate. 1 Botanisches Centralbl., 1880, p. 310. 2 Jahresbericht f. Agriculturchemie 1870-72, II, iy Dy 8 Johannsen, Bemerkungen tiber mehlige und glasige Gerste (Ugeskrift for Landsmaend), 1887, cit. Biederm, Centralbl., 1888, p. 551. 4 Schindler, Lehre vom Pflanzenbau auf physiologischer Grundlage, Wien 1896. 131 The above explanation of the production of glassiness is substantiated by the experimental results, which have been obtained by the Deutsche Landwirtschafts-Gesellschaft'. The report states:—The glassiness of the kernels depends more on the conditions of growth than on the variety. Varieties with a shorter vegetative period are glassier—such as Lupitzer, Strube’s bearded and Galician club wheat in comparison to Schlanstedter and Noe wheat. The productive power of the varieties in general stands in inverse relaton to the glassiness of the grains. 4. CONTINENTAL AND MARINE CLIMATES. The characteristic distinction of regions influenced by the ocean con- sists in the lesser fluctuation between summer and winter temperatures,— | since the summers are longer and cooler, the winters warmer. We find that, under the influence of the Atlantic Ocean, spring comes earlier, while au- tumn is delayed longer than in regions with a continental climate. Yet the effect on vegetation is not the one expected, in spite of the earlier spring, for the blossoming time of wooded plants is at most only a few weeks earlier, because of a cooler spring temperature and the ripening of the fruit is scarcely earlier, indeed, it is often delayed and occasionally does not take place at all. Consider, for example, grapes which do not ripen out of doors in England. Throughout the year, the air is more moist and in the change of season extensive heavy mists often prevail. Haberlandt’s opinion has already been mentioned, according to which early maturity of plants may appear with the same ease in northern latitudes as in southern ones, and thus lead to the production of corresponding varie- ties. Conditions of humidity also act determinatively in this and all become evident in the great fluctuations in a continental climate in contrast to an uniformly damp coast climate. Haberlandt’s culture experiments” gave results as follows. Seed brought from damp climates gives proportionately more straw, but less grain,—the grain is also more easily subject to lodging. On the other hand, in seed from dry regions, with a short spring and hot, dry summer, there is a production of less straw and greater grain crops, and plants from such seed better withstand drought. When exchanging seed it is more advantageous to take it from countries with a continental climate. The hard winters influence the grain product in such a way that the plants produced are less apt to winter kill than those which have been transplanted to the East from the moister west with its milder climate. The continental climate produces smaller but specifically heavier grain, while a cool and damp summer or an artificial abundant supply of water and food substances increases the size of the grain, to be sure, but at the same time causes more porous contents, since, instead of the glassy con- 1 Mitteilungen der Saatzuchtstelle iiber wichtige Sortenversuche. Saatliste vom 6. Dez, 1914. Deutsche Landwirtsch.-Ges. 2 Haberlandt, Fr., Ueber die Akklimatisation und den Samenwechsel. Oesterr. landw. Wochenbl., 1875. No. 1. 132 dition, a mealy one appears, together with a decreasing specific weight and decreasing nitrogen content. Finally an important observation bearing on the exchange of seed is the fact that winter grain coming from regions above the 45th parallel of latitude and cultivated by us in the spring, does not produce shoots, while on the other hand, that taken from lower latitudes behaved with us like summer grain. Because of the great interest on all sides in the colonies, it is necessary to take tropical conditions into consideration. Here the differences of tem- perature on the land and between land and sea attain a greater significance. Thus, for example, Fesca' reports, in regard to the great warming of the land in direct sunlight as compared with that of the sea, that the tempera- ture of the tropical ocean rarely exceeds 30°C. while the rock is heated up to 60° to 70°C. Pechuel-Loesche observed a soil temperature above 75°C. on the west coast of Africa in the 5th parallel of south latitude, not less than 36 times between January Ist and March 4th. In contrast to this, however, stands the nightly cooling down to 15°C. and less. Daily fluctua- tions of the soil temperature from 30° to 40°C. are very frequent in the tropics while, on the other hand, the daily fluctuations of the sea might at most reach 1°C. As a result of the differences in the morning quality of land and sea, a low barometric pressure must be produced on land in the day with the in- tensive sunlight, so that the air from the sea streams in that direction and, conversely at night. These sea and land breezes are considerably more in- tensive in the tropics and sub-tropics with the stronger contrasts in warm- ing land and water and form a factor to be reckoned with. According to Saito? the air above the sea is almost free from mould fungi, bacteria and yeast germs, while the air above the land (street and garden air in Tokyo was investigated) was especially rich in germs in wet and warm periods. Thus the sea breezes act as purifiers of the air. The sea breezes decrease towards the poles, since the sea gradually assumes a higher mean heat than the land and also because the daily fluctuations of the soil are less. For the same reason the changing annual winds, the monsoons, corres- pond to the periodic daily winds in the strong warming of the great conti- nents to which vegetation must adapt itself. The amount of precipitation occurring as rain depends also on the re- lation to the sea and the temperature and, accordingly, it is most abundant in a warm sea climate, scantiest in a continental one. An annual mean of 9°C. approximately holds for all the German North Sea coasts. With an So per cent. saturation, the air would contain 7.26 g. water vapor in a cubic meter. If the air cools down to 4°C. it can hold only 6.9 g. water vapor per cubic meter and the difference must therefore be eliminated as precipitation. 1 Pflanzenbau in den Tropen und Subtropen, p. 23. a 2 Saito, Untersuchungen iiber die Atmosphirischen Pilzkeime, Journ. College of Science, Tokyo. Vol. XVIII. 133 If tropic air reaches 25°C. with the same saturation (8o per cent.) it con- tains 18.48 g. water vapor and eliminates 1.18 g. water per cubic meter when cooled down to 5°C. This amount of precipitation therefore is more than three times that of air at 9°C. when influenced by the same decrease in tem- perature on the North Sea coasts. Thus are explained the heavy tropic rains and especiaily the heavy fall of dew which, in places, must suffice for a certain period in hot climates as the only source of water. Just as in cultivation experiments, soil analyses and mean temperature offer no sufficient insight into a possible utilization of food substances on the part of cultivated plants, just so little can the annual rain fall indicate the moisture conditions of a region. For it depends essentially upon the soil conditions and the distribution of the precipitation in the different months. Over a greater part of the desert of Sahara (see Fesca) the same or a greater amount of rain falls than that sufficient for Germany’s agriculture (60 cm.) without its having there any essential effect. For, on a highly heated soil, moisture exaporates immediately. The most desirable distribution of rain in the tropics is not the one extending uniformly throughout the whole year, but, viz., at the beginning of the vegetative period an abundant precipitation and then a time of dryness. The abundant clouds in the rainy season con- tribute essentially to the production of a cooler temperature which is es- pecially favorable for the development of the vegetative organs. Along the coast the climate is cloudier than it is inland. In regions of great atmospheric dryness, as in the Mediterranean basin, often there is only 20 per cent. cloudiness as an annual average: in the dryest months often only 10 per cent.,—in the moist tropics not infrequently more than 80 per cent. Since, however, the cloudiness decreases the taking up and giving off of heat, the temperature of the lower latitudes is less and that of the higher, greater. Many cultivated plants require these lower temperatures and cloudiness. We believe, with Zimmerman’, that many diseases in coffee plan- tations, especially the excessive production of fruit, may be due to insuf- ficient shading. In the same way it may be that the great susceptibility to fungous diseases which has appeared in the last 15 years” since tea has been cultivated in the Caucasus, has been due in part to the difference of the Caucasian climate from that of the regions from which tea was introduced. The development of the plant body is of course adaptable to the climatic conditions and factors of growth. The more recent biology takes these cir- cumstances into consideration as is shown by the work of Hansgirg*. He speaks of stenophyllus wind leaves (as in the willow type); of leather (coriaceous) and wind leaves (palm type); of xerophyllus leather leaves (Myrtus, Laurus), of dew leaf types (Bromeliaceae, Pandaneae) ; thick 1 Zimmermann, Sonderberichte tiber Land- und Forstwirtschaft in Deutsch- Ostafrika. Vol. I, Part 5, 1903. , 2 Speschnew, Travaux du jardin bot. de Tiflis VII, 1 Verhandl. d. Internat. landwirtsch. Congresses in Rom 1903. 3 Hansgirg, A., Phyllobiologie nebst Uebersicht der biologischen Blatttypen ete. Leipzig, Borntraiger, 1903. 134 leaves (Crassula and mesembryanthemum types) ete. The most conspic- uous example is the vegetation of the sea shore with its halophytic character. Brick? explains the fleshy and glassy constitution of the vegetative organs as due to the abundance of sodium salts, which makes the parenchyma ex- tremely turgid. The greater the number of examples showing the adaptation of the plant to climatic conditions, the more marked will be the untenability of the theory, that the climatic relations formed in each place of cultivation can be changed at will without causing injury. If the whole sum of the climatic factors should correspond in two widely separated localities this would be no guarantee that the given plant would thrive as well in the new home as in the old, since the distribution of light, heat and moisture can be proved to be very different in the different periods of growth. The diseases of the New Holland and Cape plants which, adapted to a dry climate, must pass their lives in our sunless, damp conservatories, give the most abundant proof. Decay of stem and root, dying of the twigs caused by Botrytis etc., constantly cause injuries to the successful cultivation of these plants. The so-called damping off of the shoots of Pimelea, Chorizema, Pulteneae, Cor- rea, Boronia, Agathosma, and Borosma, of Helichrysum, Humea etc., is a result of the great humidity in our conservatories which can not be over- come. 5. INFLUENCE OF ForEsTs. The forestration of a locality modifies the influences of the position and soil constitution and to this point pathology must pay especial attention. The influence of forests is like that of surfaces of water, for, since organic substances possess a higher specific warmth than do mineral substances, the overgrown soil will be cooler, with an equal exposure to the sun, than the naked rock or sand. The summer heat is also moderated by forests. With the abundant evaporation of the foliage, the air becomes more moist, the thicker the growth and the less motion in the air. Corresponding to the greater evaporation, there is a more abundant cloud formation over forests which is not so easily dispersed. Since the relative humidity of the air is greater in and above the forest, much more dew is formed. The force of the rain gusts is decreased. Since torrential rains, especially on slopes, cannot be taken up as quickly, the mass of water runs off from the naked earth and at the same time carries away the fine humus from the higher fields to the lowlands. The annual repetition of this process so changes the conditions of the fields that the higher places become impoverished and retain only a slightly fertile soil skeleton, while on the low lands the humus layers keep on growing. The power of the soil to retain water decreases with the loss of humus and injuries due to a scarcity of water show themselves. In heavy soils the steady beating of the rain drops in severe storms tends to form a crust. 1 Brick, Beitrage zur Biologie und vergleichenden Anatomie der baltischen Strandpflanzen. Cit. Bot. Jahresb. 1888, I, Ds UGb: 135 All these unfavorable conditions are overcome by the forest, the tops of the trees catching the rain and partially retaining it. Nevertheless the water, which passes through and runs down along the trunks, is retained by the moss and the dry leaves in deciduous forests, forming the upper surface of the soil or the humus, thus becoming of benefit to the vegetation. Furst’s' “Tllustriertes Forst- und Jagdlexikon” gives some positive figures on these theoretical discussions. Based on the observations of the forest meteorologi- cal stations, it is stated that the temperature of the air in the annual average is possibly 0.8°C. lower under the close roof of tree crowns of the forests, than in the open. The difference is greatest in summer (up to 3°C.) while it approximates the annual average in spring and autumn and almost dis- appears in winter. “The fluctuations in temperature are less under the shelter of the tree crowns than in the open.” The temperature of the forest soil is from 1 to 3°C. lower at all seasons of the year than that of open land. The absolute moisture does not differ in the forest and in the open; but, on account of the lower temperature, the relative moisture in the forest during the winter, spring and autumn is from 4 to 8 per cent. higher than in the open, and in summer from 12 to 20 per cent. The evaporation from a free surface of water in the forest is from 50 to 60 per cent. less than in the open; “the evaporation of the water from the soil is reduced from 80 to go per cent.’”’ Of the precipitated moisture, 10 to 50 per cent. will be retained by the crowns of the trees, according to the species, the age and dimensions of the forests as well as the amount of precipitation, and in light rains it often amounts to 100 per cent. In general 60 to 80 per cent. reaches the soil in the forest. “In Central Europe the annual and the summer temperature will be lowered 1° and 2° to 3°C. by the dimensions of the forest and the relative moisture raised ca. 5 per cent. and 15 per cent.” Since the amount of the distant action from extended forestration has not yet been determined, the question as to the influence of the forest on climate must remain open. But one effect of the forest on the immediate vicinity cannot be denied and this phytopathologists must consider. Differences in insolation are felt slightly in the forest, but very quickly and strongly in the open field. The soil is warmer; the layers of the air lying above it must necessarily produce an equalizing air current which is most significant in spring when vegetation awakens. Hesselmann’s* investigations give an insight into forest vegetation. He observed the regular dying of the twigs which takes place within the crowns of the trees and found that in birch and mountain ash the leaves were still strongly active in assimilation; but in the hazle-nut markedly less so. If well-lighted branches die, phenomena of correlation are at fault. Trees which can live in shade develop distinct sun and shade leaves; trees 1 Tllustriertes Forst-und Jagdlexikon, 2nd. Ed., revised by Dr. Hermann Fiirst, Berlin 1904, Paul Parey, p. 384. 2 Hesselmann Hendrik, Xur Kenntnis des Pflanzenlebens schwedischer Laub- wiesen. Jena, Fischer, 1904. “Cit. Bot. Centralbl. v. Lotsy, 1904. No. 49. 136 which require light do not show this difference. The assimilation activity of the flora of the forest floor is very rapid in spring when. the trees and trunks are still bare and decreases with the foliation more slowly in shade trees, because of their structure, until it finally ceases entirely. The respira- tory intensity decreases with the decreased “food consumption.” Detached shade leaves of Convallaria majalis etc., form more starch in the sun as well as in the shade than do sun leaves treated in exactly the same way and they also fix carbon dioxid more rapidly in the same amount of light than do these. Moreover in Convallaria the storage of starch was found to be less, the drier the soil. Equally large leaf surfaces containing palisade cells tran- spire much more strongly than do those leaves having the structure of shade leaves. It is evident from these statements that changes of great importance must take place in the economy of trees accustomed to shade, when suddenly exposed to light, viz., when left standing by removing parts of forests. In parks too strong and sudden an exposure to light by the removal of num- erous trees not infrequently results in the partial or total death of the crowns of the specimens left standing. We must turn our attention to still another point. If plantations of fruit trees along streets on level land, especially cherries, be examined, many cases will be found wih trunks split open on the south or southwest side, with the bark torn into tatters and often showing lumps of gum on the wounded surfaces. These injuries are very evidently due to frost. The ex- planation lies in the fact that the level, cleared lands are exposed in spring to extreme temperatures. The February and March sun shining intensely on the trunks, and strengthened in its action by the reflection from the soil, starts the reserve plant food prematurely and the tissues, being richer in water and sugar, at once succumb to the action of the frost. A moister atmosphere in the neighborhood of water or wooded areas equalizes the temperature and serves as a protection from frost. Naturally in regions with greater soil elevations and more noticeable differences between valleys and mountains these factors co-operate determi- natively and often decisively, but on the plains the forestration is a very considerable factor. Cutting considerable forest tracts on wide plains often is a source of injury avenged not only on the owner but on the whole neigh- borhood, since it increases the chance for damage from late frosts. In this connection many small forest tracts, scattered over a large plain, would be of use since no considerable distant action from one single large forest may be reckoned upon. There is a further advantage to be derived from forests,—that of protection against the wind (windbreak) when there are no mountains. Just as every bright side has its shadow, forests can exert an injurious influence on the adjacent fields. The forest properly located can withhold the summer rains, usually coming from the west, from a given field so that there will be dry, windless streaks across the fields in its immediate prox- 137 imity,—or, on the other hand, the forest may make streaks across the field accessible to rains and prevent the rapid drying off of the seeds. In the first case, the forest may become a harboring place for injurious insects. It has often been observed in the case of dwarf cicades that they begin their de- vastation of the fields from the dry edges of the forest. The more severe attacks of Puccinia, Ophiobolus and Leptosphaeria herpotriahoides serve as examples of the influence of moisture, near the border of the forest, upon fungous diseases. Goethe’s discoveries! as to the influence of the place of growth upon the canker of fruit trees, caused by Nectria ditissima, must be considered. The tendency to disease from canker is favored by an in- creased humidity as offered by higher regions or also by cold valley soils. “The trees show in such places a meagre growth and are covered with mosses and lichens. Similar conditions are observed also near extensive forests, out of which cold, damp air streams even in the summer.” 1 Goethe, Rudolph, Ueber den Krebs der Obstbaume. Berlin 1904. Paul Parey. CHAPTER It UNFAVORABLE PHYSICAL CONSTITUTION OF THE SOTE r LIMITED SOIL MASS: Roor CURVATURE. For practical agricultural and forestry purposes, the question as to the limitation of space in the soil plays a subordinate role when there is no scarcity of food stuffs, since disturbances in nutrition, arising from the overgrowth and rubbing of roots pressed tightly against one another, or by their growth in crevices of rocks, have no agricultural significance. The matter is quite different, however, in gardening and the cultivation of house- plants by the plant lover. In these circles, however, opinions as to the influence of too small soil space on the spreading of the roots are divided. Predominant and also clearly expressed on the part of many agricultural chemists is the opinion that the mechancial effect on roots, closely pressed on one another and tangled by repeated curvature, has no influence on the thriving of the plants. They think that in limited soil space only a scarcity of food may ever be involved which would make itself felt very quickly and could be corrected advantageously by fertilizing. The best proof should lie in the cultivation of the so-called “market varieties’ by commercial growers in large cities, who, conforming to public taste, grow very vigorous specimens of all blos- soming plants (Fuchsias, Pelargoniums, Begonias, etc.) in relatively very small pots. The fact is correct, the explanation, however, inconclusive. The restriction of a large root mass in a small space results first in the increased production of lateral roots. This may be observed easily in water cultures. If one of the large roots reaches the bottom of the glass container and its tip is forced to bend around, new lateral roots are produced im- mediately. Noll* has given special study to this. He found that on the bent portions of the main root, the lateral roots were formed only on the con- 1 Noll, F., Ueber den bestimmenden Einfluss der Wurzelkriimmungen auf Enststehung und Anordnung der Seitenwurzeln, Landwirtsch, Jahrbiticher XXIX (1900). p. 361. 139 vex surface, the concave surface remained free. This is true of both main and lateral roots and not only under mechanical influences, but also as a result of geotropic and hydrotropic stimuli. Pollock' has pointed out, in this connection, that twisted roots contain more water in the cells of the convex side than in those of the concave side. Noll ascribes this growth of new lateral roots at the point of curvature to a perceptive power of the plant to the formal relations of its own body (Morphaesthesia). This expression may be accepted if by it is understood a mechanical transfer of material resulting from the stimulus of curvature on the affected tissues. The process is similar to the one occurring after direct injury when the cytoplasm has accumulated in the cells adjacent to the wounded surface. Of course laterals are found also on concave parts of twisted roots, but, in such cases, the buds of the laterals were present before the twisting of the mother root had taken place. In trees grown in the open the development of lateral roots on the convex side can be of practical advantage, since the plant is thus more firmly anchored and extends over a greater area of soil containing food stuffs, where otherwise the root branches might not have penetrated. But where the whole root ball has only a definitely limited soil space at its disposal, as in potted plants, disadvantages arise which must find expression in the pro- duction of organic substances. We can perceive these disadvantages at once, if we observe more closely a pot said to be “root bound.” The greatest number of young roots have grown out towards the periphery and been so pressed against the porous sides of the flower pot, that many fibres are broken off when the pot is removed. Part of the root fibres have stuck fast like bands or membranes and have died. The latter circumstance is especially apparent in palms and Dracaenae, in which the dead roots consist only of the stele and the outer bark, which has shivelled up like a papery covering. The straining of the roots toward the side of the pot may be attributed to the need of oxygen. Naturally this demand is less easily satisfied as the network of roots fills the ball of earth more closely. To this must be added the secretions of the root itself. Czapek* determined that these secretions may be ascertained in moist air as well as in water cultures. In air saturated with vapor they are frequently observed as drops on the root hairs, the re- sult of a strong internal pressure in the cells. Minimum amounts of potassium, calcium, magnesia, sulfuric, hydro- chloric and phosphoric acids are eliminated. Potassium phosphate, causing the well-known reddening of litmus paper, is somewhat more abundant. In regard to acids, Czapek found that the presence of lactic and acetic acids could not be proved, but that,on the contrary, formic acid is found not in- frequently in its potassium salt as a diffusion product of the living, youngest 1 Pollock, James, The mechanism of root curvature. Botan. Gaz. Chicago, XXIX, 1900. pp. 1 ff. 2 Czapek, Fr. Zur Lehre von den Wurzelausscheidungen. Jahrb. ftir wiss. Bot. 1896. Vol. 29. Part III. 140 parts of the roots. Potassium oxalate was eliminated by hyacinth roots. Carbon dioxid, however, must be considered primarily and causes the rock etchings, as it occurs dissolved either in the water of the root-hair cells or of the soil interstices. Monopotassium phosphate and carbon dioxid among the root secretions must be especially considered. In pot cultures the latter is of especial importance. It is retained in the root balls in great quantities, the more thickly matted they are and the wetter they are kept by the grower. The production of carbon dioxid is greatly increased by the respiration of the soil micro-organisms which in their metabolism decompose the carbo- hydrates and other organic substances. For instance Stocklasa’ found alcohol, acetic acid and formic acid in forest soil and finally carbon dioxid and hydrogen. The hydrogen often unites with oxygen to form water. Lack of oxygen and the excess of carbon dioxid kill part of the roots and the process is gradually evidenced when plants are grown in small pots, even if over-abundant foodstuffs be given them by fertilizing. However, if fertile earth alone is used, without subsequent additions of fertilizers, the roots, becoming thickly matted on the walls of the pot, do not touch the ball of earth actually as they develop on top of older roots. In such cases, they cannot further draw from the soil the food materials needed in growth. Early investigations by Hellriegel’ prove that excessively limited soil space in itself limits production. To perform these experiments many annual and perennial agricultural plants (barley, peas, buckwheat, clover, etc.) were sown in glass containers of different heights in as uniform gar- den soil as possible and were grown with an observance of all the precautions used in sand and water cultures. In order to prevent any question as to the exactness of the results obtained due to a different amount of soluble nutri- tive elements control experiments were made with an abundant addition of fertilizers, under otherwise similar conditions. The result was, that no difference in production whatever was shown in favor of the fertilized plants, that those not fertilized must thus have found in the unfertilized garden soil all the nutritive substances that they needed for their production. An indirect proof lay also in the results of the experiments given by the unfertilized plants when compared with one another. The yield showed in fact, that clover in the first year had produced about as much dry material as the other varieties of plants. This did not prevent the clover, however, from producing in the second year on the same soil a second crop and in fact a crop two or three times as great, and even in the third year it produced as much as in the first year. From this it is evident that the amount of nutritive substances could not play a réle in any of the experimental pots, since they were everywhere present in excess. If now, however, the amount of dry substance increased with the size of the container, this result could be ascribed only to the influence of the 1 Stocklasa and Ernest, Ueber den Ursprung, die Menge und die Bedeutung Shae Sac aip does im Boden. Centralbl. f. Bakteriologie ete. Section II, Vol. XIV. 2 Hellriegel, Beitrige zu den naturwissenschaftlichen Grundlagen des Acker- baues. Braunschweig. Vieweg, 1883. pp. 184-224. eT IAI volume of the soil. The plants under experiment stood in glass cylinders of the dimensions and contents given below, received steadily from 30 to 60 per cent. of the water required by saturation of the soil and resulted with clover, as follows: Height of the Cylinder. Diameter in the Clear. i, 496 10;09).) Cm. 14 cm. ES Ob eto; 07. “cm: I4 cm. Pie e4etor-35" . \Cn, 14 cm. IV. 18.0 cm. 14 cm. Earth content. Harvested dry substances, Air dry. Absolutely dry. in the years 1872, 1873, 1874. 19,500 g 18,600 g. 417.2 g. with 6.92 per cent. pure ash 13,000 g. 12,400 g. ZOMG porns: OOS eae a i 6,500 g. 6,200 g. PP OU Sas Wit) SOLOOy tyes ee 2,250 o 3,100 g. ROO it, or arn Cells Be ae Since, in the containers with a very large soil volume, too great a con- solidation, therefore somewhat abnormal conditions for some plants, has appeared, because of the sudden addition at first of great amounts of water saturating the soil to 60 per cent. of its water capacity, Hellriegel, in his harvest tables, explained especially the results for the sizes III and IV. From this it appeared that, with peas, an amount of soil of 3,100 g. gave on the average, 29.97 in dry substances. ce “ce ins “ee cc “ce ce 6,200 g. 47.94 For peas, therefore, the proportion of the soil was 12 eek Se oMbarvest wast) rer.6, For beans, therefore, the proportion of the soil was ees “ce (a9 ia harvest was 1:1.8. In 1872, exactly the same proportions in harvest results were found for barley as for beans. We omit here the repetition of the figures, since those cited show clearly enough that, in two equally wide, but unequally tall ves- sels, both containing nutritive substances in excess, and steadily receiving the favorable amount of water, the harvest came out as 1:1.6 up to 1.8, if the amounts of soil bore the proportions of 1:2. Thus a strikingly evident influence of the soil volume may be confirmed and the question now is, how this influence may be explained. Hellriegel found that the height of the yield stood in inverse ratio to the amount of the mechanical resistance, which opposes the development of the root-network of the plants under experiment. If commercial growers get apparently opposite results and find that the growth in small pots is great and quick, the explanation lies in the fact that they use a very rich earth and highly concentrated solutions are present in the soil. Comparative measurements showed, however, that the root development in rich nutrient solutions is essentially shorter than in weakly concentrated ones. Hence the demand of the root fibre is actually smaller. 142 However, in the same length of time, the root makes a stronger growth when kept under glass, or in hot beds, than where the plants are in the open ;— for these glass cases all have bottom heat. Finally, the aérial axis finds itself under conditions making possible an especially rapid and abundant develop- ment. The atmosphere rich in water vapor and carbon dioxid develops the largest individual cells possible with comparatively little transpiration, hence, the turgid and significant large size of the foliage. Therefore, in garden cultures in small pots, the root is better and earlier formed and utilized, so that the injuries due to root curvature and bruising make them- selves first felt at a time when the aerial axis has already made a consider- able growth. That growers, however, clearly recognize the disadvantage of small pots and, when possible, do without them is evident from the so-called “feeding cultures” (forcing). In this the specimens are shifted into larger pots as the root branches penetrate to the sides of the pot. DwarF-GRowTH (NANISM). The dwarf conifers found in trade under the name “Japanese or Chinese Trees of Life” show an interesting effect of the influence of a limited soil space. The figure on the next page illustrates a living specimen which has been classified by the well-known firm J. C. Schmidt (Berlin) as Thuja obtusa and kindly placed at our disposal. The tree, with the pot, is 86 cm. high in all,— and 60 cm. high above the soil. At its greatest width the crown is 80 cm. across. The base of the trunk, divided into several pro- truding ridges, has a diameter of 19 cm., the trunk at the height of the crown, where the branches appear, one of 12 cm. This healthy specimen, with a dense crown, whose age is estimated to be 100 years, cost $87.50. In literature, notes may often be found referring to the skill of the Japanese and Chinese in growing dwarf specimens of trees, hundreds of years old for table-decoration?. Our examination of the trunk from a dead tree destroys the halo of the miraculous, with which these productions of Japanese and Chinese hor- ticulture have been surrounded. A section 8 cm. long and 6 cm. at its widest diameter showed most excentric annual rings. The distance of the pith from the bark amounted to 1.5 cm. at one side of the trunk and to 6.5 cm. at the other. Counting with a magnifying glass showed 30 annual rings on the wider, but only 15 on the narrower side. On the side favored in growth, a great variation in the breadth of the annual rings was noticeable. Four 1 In an article on “dwarf growth in the vegetable kingdom,’* Grube quotes a report by Sir Geo, Staunton, from “des Grafen McCartney Gesandtschaftsreise nach China,” Berlin 1798. Staunton saw in Ting-hai, spruces, oaks and orange trees none of which were more than 2 feet high and on which fruit had set abundantly. At the base of the trunk the soil was covered with layers of stones weathered and covered with moss giving the pots the appearance of great age. “Throughout China, there is a great liking for these artificial plant dwarfs for we found them. as a rule, in every house of any pretention whatever.’ It is there further related that the “liliputian”’ trees were propagated by binding loam or garden soil around different branches. This was kept moist until the branches developed new roots in the earth ball; they were then cut off. We still use this process in the layering of branches or top shoots and the covering of the cut places with moss, This plan 143 zones could be distinguished. Each of these ended with very slender rings, the tracheids of which had especially narrow lumina and had become browned through resinosis. Otherwise the wood was healthy. In its dimen- sions the bark corresponds to the section,—1. e., on the side of the narrower rings, it was 1.5 mm. thick, on the other side 4 mm. On the narrower side, a depression was found, in which a scantier development of the wood had been equalized by a thicker formation of bark,—up to 5 mm. There was shown here a tendency to loosen the individual bark scales between the flat cork layers resembling full cork. Fig. 15. Dwarf specimen of Thuja obtusa, 60 cm. high and 80 cm. wide. (Orig.) At the base of the trunk may be seen the division of the aérial axis into a number of root branches projecting above the pot. Thus the statements as to the great age of the trees are seen to be erroneous. These cannot be more than some thirty years old and their dwarf growth, in our opinion, can be obtained by keeping the plants in the very was followed in China, because it had been observed that an artificially produced dwarf character is hereditary. When the tendency has become hereditary it is strengthened in the new individual by turning down the end bud of the main shoot and bending it with wire in another direction. “If it is desired to give the dwarf tree the appearance of an old, already half dead tree, the trunk is often covered with syrup to attract ants and these, after they have eaten the sweet, immediately injure the bark, giving it thereby a brownish, half-weathered appearance.” Rein** describes the Japanese process which is somewhat different. They call the dwarfing or “Nanisation” “Tsukurimono.” This expression is not used in the new book by Ideta***. According to Rein, the dwarf growth is secured by choosing 144 smallest pots until they are root-bound ; then transplanting into a large pot, in which the root crown is raised up above the pot in order that the root ball may have full benefit from the soil. After the year of transplantation, wide annual rings are produced at first, which become narrower as the plant be- comes root-bound until the growth has become very slight and the last annual ring formed is made up of a few, browned autumn-wood tracheids. In this way the stilt-like trunk bases, borne on the freely exposed root branches, are produced. The crown is probably kept thick by a light cutting back of the tips of the branches, obtaining thereby a greater ramification. In the same way the root balls might have been pruned at each transplanting. We conclude from the porous places filled with full-cork, which occur scattered in the bark, that the trees have been kept wet. At any rate we would have no difficulty in growing trees in such decorative dwarf forms from the genera Thuja, Thujopsis, Biota, Cupressus and similar ones by limiting the soil content. A corresponding treatment is recommended here and there for de- ciduous trees and plants. In forcing woody blossoming plants it is desirable to have for sale small specimens as full of bloom as possible. To attain this end, the bushes are planted in small pots, cut back and kept until spring, as long as possible, in cool dark cellars in order to retard the growth beyond the natural time of awakening. Ice cellars serve best in this connection. When vegetation has advanced considerably out of doors the plants are brought out. They now find a very different combination of vegetative factors for the maturing of their growth. Instead of moist spring air, a comparatively slight warmth of the sun and long, cool nights, the plant finds dry, bright, long days with little precipitation. As a result the branches re- main short and the eyes easily develop blossom buds. It will not be out of place to call attention to the fact, that in keeping the bushes in warm cellars, an opposite result is obtained,—namely, abso- lute unfitness for forcing. The warm, dark place where they are kept pro- duces deformed, very premature shoots, which, when brought at last into the open air, either dry up or gradually and slowly lengthen to whip-like, blossomless wands. The stored-up material has been wasted in the cellar in forming the deformed shoots. especially small seeds from under-developed plants. These little trees are pruned and transplanted frequently into as small pots as possible. The cross-section described above in the text shows this. Further, the trunk and branches are twisted and bent toward the horizontal. It is said that the root ball is cooled. Among varieties of plants used especially in Japan for the growth of dwarfs are mentioned the toy varieties of Acer palmatum, which are budded, “greffe par approache.” Further Pinus massoniana and P. densiflora, Podocarpus Nageia, Sciadopytis verticillata. Among fruit trees the Kaki plum. Diospyros Kaki, is suitable for this, the Mume-plum, Prunus Mume and Sakura, Prunus Pseudocerasus, as well as Amygdalus Persica. Among decorative plants are mentioned Evonymous Japonica and the bamboo. * “Zwergbildung im Pflanzenreich”’ Gartenwelt, 1904, No. 49. ** Rein, J. J., Japan nach Reisen und Studien. Leipzig, Engelmann. Vol. II., p. Siib: *** Tdeta Arata, Lehrbuch der Pflanzenkrankheiten in Japan. 3rd Ed. Tokio, Shokwabo, 1903. 145 The most frequent occurrence is dwarfing due to scarcity of water. Like every other organism, the plant has the ability of adjusting itself with- in wide limits to different conditions. An individual, accustomed from its youth up, to a very scanty amount of water, can pull through with half the amount of water used by a plant of the same species and variety, which had developed with excessive water. Naturally the structure of the whole in- dividual is adapted to these conditions. More thorough investigations have been made with barley’, which was cultivated with a varied water content in the soil (10, 40, and 60 per cent. of the soil’s capacity for absorbing water). The most favorable water content for growth might be found possibly be- tween 50 and 60 per cent. of saturation. In the experiment it was shown that the plant even with only 10 per cent. of water had regulated its organization. Little leaf and root substance had absolutely been formed, but the proportion between grain and straw was normal; therefore about as much dry substance in the form of grain as in the form of straw. With the same amount of food in the soil, the dry substance increased as the roots obtained additional water. With too much water, i. e., more than 60 per cent. saturation, very little dry substance was produced absolutely and this small amount was worthless since the pro- portion between straw and grain was changed,—to the detriment of the latter. Measurement of the leaves showed that the grains grew longer and wider, when water was supplied regularly and more abundantly. These larger leaves, found with a greater water supply, are due partly to the in- creased number of cells, partly to their greater distention. If the individual cells of the upper epidermis are larger, it may be assumed from the very beginning, that the respiratory apparatus (the stomatal cells) will share in the greater stretching of the upper epidermal cells and will also appear to be the more widely separated thereby. Direct measurement confirmed this assumption, so that therefore for each square centimetre of a leaf grown with abundant water, fewer but larger stomata will be found, than when plants are grown with a scarcity of soil water. H. Moller has determined by experiments? that plants dwarfed by lack of water (Nanism) are structurally different from plants whose dwarfishness is due to a scarcity of mineral substances in too weak solutions. In the latter the narrower leaves are probably not due to narrower cells, resulting from water scarcity, but to a smaller number of cells, since measurements show the same cell breadth and the same size of the stomata in plants from a satisfactory nutri- ent solution and from an insufficiently concentrated one. These differences are easily explained. When the mineral substances are insufficient the cell increase will suffer only from water scarcity. The cells are less distended. As shown by some of Moller’s experiments with Bromus mollis, this nanism is not hereditary, since specimens of huge size can be grown from the seed 1 Sorauer, Hinfluss der Wasserzufuhr auf die Ausbildung der Gerstenpflanze. Bot. Zeitung 1873, p. 145. 2 H. Moller, Beitr’ge zur Kenntnis der Verzwergung (Nanismus), Landwirt- schaftliche Jahrbticher von Thiel. 1883, p. 167. 146 of dwarf plants. Yet, with equal vegetative conditions, seed from normal plants produces more vigorous specimens than that from dwarfed plants. The case of nanism due to scarcity of nutritive substances, which Moller studied, is not rare in sandy soils. The lack of nitrogen plays the chief part here. This nanism is usually characterized by the fact that, be- sides the general reduction, the relations of the separately produced organs have been changed. In proportion to the whole growth, the root undergoes a greater distention; but the sex organs suffer a greater retrogression. The number of blossom eyes is very small. Instead of a cluster or a head, there is often only a single blossom. Where a greater number of blossoms are formed single seeds develop which can germinate. It is easy to understand that the leaf-forms are simplified. In discussing dwarf growth, the phenomena of bud variation must be considered. These have no connection with soil conditions or other external vegetative factors. The form of growth up to this time is so changed by some impulse or stimulus, acting temporarily or persistently, that the organic substance is used up in the form of more numerous, shorter, usually thicker, short-leaved branches instead of fewer slender, large-leaved ones, in this way producing witches-brooms. In many cases the incitement to such a changed direction of growth may be found in parasitic attacks. The fungus genus Taphrina (Exoascus) especially irritates the branches of various deciduous trees resulting in the formation of witches-brooms (see Volume II, page 179). In other cases we find rust fungi or mites of the genus Phytoptus. Besides these forms due to parasites, however, some surely exist in which other organisms are not active. We find especially in her- baceous, quickly growing plants (Campanula, Pelargonium) the occurrence of a bud disease (Polycladia) as a correlation-phenomenon. In sickness or loss of blossoming branches, small fleshy bunches are formed, at times, at the base of the stem, made up of closely set bud-eyes, some of which grow out into sickly branches. In diseased thickets growth is often exhausted by a continued new formation of short branches, because the blossoming axes no longer lengthen, but stop growing and turn yellow. In Calluna vulgaris, instead of long blossoming branches, we find blossomless bunches of twigs, pyramidal in form, which might also be called witches- brooms. In other cases polycladia and bushy forms are produced by the develop- ment of normally formed but still dormant lateral eyes, when the buds of the tips have been injured. This takes place when wild growths choke out cultivated ones. In conifers, the heart buds grow out and form bushy crowns, which are called “rosette-growths.” The so-called “cow-bushes’— due to injury to beeches, alders, etc., from the grazing of cattle, are similarly explained. Pure bud variations are numerous. In them the growth in length of the individual branches is restricted without any recognizable cause, result- ing in a greater and more rapid development of lateral branches, Among 147 the actual forms of witches-broom, the tendency at present is to place under this head of bud variation the numerous spherical bushes of the spruce witches-broom’. The greatest number of examples is furnished by the many cultivated plants of our gardens in the so-called globe forms of coni- fers and in the dwarf forms of blossoming bushes. In the short-lived sum- mer plants (Ageratum, Zinnia, Tagetes, etc.) we find that the dwarf growth can become an hereditary peculiarity, persistent in the seed. Too Turck S£EDING. A limitation of the soil space and a struggle for water and nutritive substances is always produced by too thick seeding. The struggle of the plants with one another for their food appears earliest and sharpest in sandy soils. Besides the dwarfing of individual specimens, the weakening of repro- duction deserves especial consideration. This becomes evident not only in the decrease of the blossoms, but also in the change in their character and becomes especially perceptible in horticulture, because staminate blossoms are produced predominantly. The unavoidable scarcity of nitrogen is also a factor. The greater the amount of nitrogen supplied, the more abundant the meristem, rich in cytoplasm. Hoffmann? gives the results of many cultural experiments in pots and open ground, to determine the influence of too thick seeding for different plants. In this, for every 100 pistillate blossoms there developed the follow- ing number of staminate ones :— With a more scat- In With Too Thick Seeding. tered position of the plants. MEN CMTS CWT WG A005 oo ni0'5 oho’. oss 233 125 Se ot te a are Ore 200 77 Sef CCS PETUMG: og oxn 3.0. s15¥s 150 73 Mercurialis annua .......... 100 go ReumecACerosella® 2635. ee 152 8I Spinacia oleracea (average of Several SOWINGS)) &. os cases 283 76 In Cannabis his results were contradictory, which may be explained by a consideration of Fisch’s statement® that the proportion of the sexes in hemp is already determined in the seed,—that, therefore, external in- fluences can bring about no further changes. Belhomme maintains that the form of the hemp seeds admits of conclusions as to the sex of the future plant, since the longer or the more spherical forin, as in bird’s eggs, indicates a staminate or a pistillate individual. Since the phenomena appearing with too thick seeding may be traced essentially to scarcity of food substances, further examples will be cited when the scarcity of nitrogen is discussed. 1 Tubeuf and Schréter, Naturwissensch. Zeitschr. f. Land- u Forstwirtschaft. 1905, p. 254. Hoffmann, H., Ueber Sexualitat. Bot. Zeitung. 1885, No. 16. Fisch, Ber. der Deutsch. Bot. Gesellsch, 1887. Vol. 5. Part 3. co bo 148 2: AUNSUITAB EE SOM SPRUCE Ee a. WiLicHt Sores: DISADVANTAGES OF SANDY SOILS. The way in which the individual soil particles are related to one another, is termed the structural condition. If the constituents of the soil are simply laid one above the other in separate grains we speak of a separate granular structure. In soils under cultivation, however, the individual soil particles are found united into different kinds of aggregates, called a friable structure. While, in the first case, each soil grain has a homogenous constitution, the soil grains in the second case are porous and not homogenous, therefore can be more easily transformed. The content in soluble salts, the activity of the animal world in the soil and the action of plant roots and their se- cretions, as well as the physical processes of working the soil, determine the formation of a friable structure. The amount of space between the indi- vidual grains will vary according to their size and arrangement. Ramann calculates the porosity volume of equally large soil particles, according to whether the particles are arranged regularly in rows on top of one another or between one another, as fluctuating between 47.64 per cent. (greatest porosity) and 25.95 per cent. of the whole volume (closest stratification) +. While in the friable structure, because of the different individual par- ticles, a continuous change in size and arrangement takes place, due to me- chanical and chemical influences, in the separate granules, most distinct in stony and gravelly soils, the physical relation is more regular and therefore more significant. We have already spoken of the influence of actual sandy soils and the changes which roots can experience when growing in cracks in rocks. The injuries to vegetation, which are caused by too loose a structure of stony soil at the disposal of the root, seem lessened when the blocks of stone are weathered to rubble. Fine, earthy particles are produced, especially when the stones are easily decomposed (many granites, Gneiss, Syenite, etc.) af- fording the roots more abundant food and firmer support. Next to the great possibility of being rapidly heated through, the factor acting most injuriously is great dryness, which prevents a decomposition of organic substances lead- ing to the formation of humus; this, under certain circumstances, forms moors. Forestry in mountains must take such conditions into account. Sandy soils come under consideration for field cultures on the level. As soon as these possess greater admixtures of clayey substances (loamy sand) or of humus, they form most productive soils and therefore find in this discussion no further consideration. Sandy soil is unfavorable for cultivation only when the sand is truly quartz sand and is either pure or is present in a very high per cent. (70 to 90 per cent.) 1 Ramann, Bodenkunde, 2nd. Ed., p. 222. Berlin, J. Springer, 1905. 149 In such cases, the slight absorptive capacity should be mentioned first of all as a hinderance to cultivation. The diseases caused by scarcity of water and food substances are pre-eminently peculiar to sandy soil. The more clayey and humus admixtures present, the more the danger disappears, in so far as it is not brought about again in another way by the washing away of considerable amounts of easily soluble mineral substances. Such an erosion takes place much the more quickly when the decom- position of organic substances, which occurs easily under the influence of warming and aération, is increased by other conditions. On this account one must be especially careful in removing forests and litter. In deep, sandy soils, the removal of the litter holding its moisture is disadvantageous since the organic substances present are but very little decomposed by atmospheric influences and bacteria, and accumulate as raw-hwmus, which can finally give rise to the formation of meadow ore. According to Ramann, in lower positions the deposition of raw-humus gradually leads to complete marshi- ness, as in the large moors of North Germany, which almost without excep- tion have originated from land which at one time was covered by forests. The humus is beneficial only when mixed with sand, since the friability of the soil and its water content is increased and its capacity for heating re- duced. This capacity for heating and giving off heat of sandy soils is an essentially harmful quality. Pure sand possesses the greatest capacity for giving off heat and consequently the greatest capacity for becoming wet with dew. The process of taking up and giving off heat decreases as the sand is finer grained and whiter. Sand of the latter kind, for example, is that rich in calcium, while, of colored sands, the ones rich in iron hydroxid are very warm and cool off slowly, behaving therefore like sand mixed with some clay. Associated with the great fluctuations in temperature peculiar to sand is the poor capacity for conducting warmth. As a result of difficult equali- zation its subsoil has a more even temperature, since it is warmer in winter and cooler in summer than under more binding soil coverings. The danger from frost is increasedly greater and more injurious. The rapid warming in spring days forces vegetation prematurely and the great drop in tem- perature at night is injurious, while the plant would be uninjured if it started later in a soil containing water and rich in clay. The sandy soils of fine constitution and slight coherence present the greatest possibilities for injury to crops. The injurious effects of drifting sand are shown in the sand dunes. Even if the dunes reduce the severity of the sharp sea winds for plants near the coasts, they are nevertheless injurious since they advance further and further inland, covering all plants. The inability of the land breeze to blow back during the night the sand which the sea breeze has swept over the land by day is due to the fact that the land breeze is heavily laden with dew and tends to compact the sand again. If the danger of being covered with sand threatens and artificial protection is 150 too expensive, one must try to bind the movable sand hills by some natural method. Sand grasses are here most valuable, since, by the rapid root de- velopment of the nodes of the buried stolens, they constantly advance over the upper surface and bind it together. Arundo arenaria, L. and Elymus arenarius L. are most frequently used. Besides these, Arundo baltica Schrad, and Carex arenaria L. should be recommended, and, with sufficient moisture, even our quack grasses as well. Among the dicotyledons, Hip- pophaé rhamnoides, L. is very good. Depending upon the admixtures in sandy soil, experiments may be attempted with Salix arenaria L., Lycium bar- barum, L., Ulex europaeus L. and the lime-loving Genista species. No matter whether we are concerned with sandy soil in the interior, as in the Mark Brandenburg, Oldenburg and Hanover, or with the sand of dunes, the first planting must always take place with the idea of binding the sand with low, rapid growing vegetation. Where nature, in the course of years, has spread out a thin vegetative covering, this should be protected by every possible means, since, in it, we have a basis which cannot be valued highly enough for the ultimate aim of all cultural endeavors, viz., to obtain a protective forest. Even if the vegetation is ever so thin, it still restrains the sand and makes the planting with young conifers possible. With their deeply growing roots they are better satisfied with poor nutritive conditions. In the beginning attention should be paid to the production of a bushy growth and only later extended inland to the cultivation of tree forms. At the sea shore, on all woody plants, a great many branches will always be found which have been killed back by the action of the wind. The most important cultural method is to leave these dead branches on the plants. They break the force of the sea wind and form a natural protection, keeping the foliage alive. LOWERING OF THE GROUND WATER LEVEL. The building of canals and the regulation of rivers tend to lower the water level in sandy soils and act most disasterously on plant growth. In contrast to the “soil moisture’ of the upper masses, the ground water trickles down in the depths, collecting on the impervious soil layers and forming the reserve supply for roots in times of continued drought. In regions like the Alpine provinces and the Bavarian plateau, which have a high absolute amount of precipitation and smaller evaporation, the fluctuations of the ground water level controlled by the annual precipitation are of scant significance for vegetation. In regions, however, with scanty absolute amounts of precipitation, and great evaporation, where the annual fluctuations of the ground water level depend on the amount of evaporation, as, for example, on the flat lands of Northern Germany, and where the reg- ular slope of the ground water curve indicates a gradual flowing away through springs and rivers (see Ramann loc. cit. 275) a lowering of the water level by canals and rivers will have the most serious influence. The soil dries out very greatly towards the autumn and vegetation becomes de- Tet pendent on the water of capillarity. This becomes scantier and scantier, the sandier and coarser grained the soil. Without the supplemental ground water tree growth cannot persist. If, in the course of years, the level of the ground water fluctuates a half metre in average height the plant growth will adjust itself to the change when an equilibrium has been reached. Both the water content and the water requirement of plants are correlated with the soil moisture, as Hedg- cock’st comparative cultures in quartz sand, loam, salt soil, humus, etc., show. Root activity depends also on the water content of soil and plant and this activity is by no means passive but, as Sachs” and more especially Molisch* have shown, is essentially active because the secretions of the roots decompose the inorganic and organic substances in the soil. The last named investigator calls attention, in this connection, to the circumstance that un- injured roots, in contact with a dilute solution of potassium permanganate, become covered with a precipitate of brown stone, removing the oxygen from the solution. The experiment is unsuccessful with stems and leaves. With easily oxidizable bodies, as, for instance, guaiacum, pyrogallic acid and humus, the root secretion acts as an oxidizer. A guaiac emulsion is turned blue by it. Molisch considered the root secretion to be a self-oxidizer by passive molecular oxygen, thereby making the oxygen active and bringing about the oxidation of substances which are readily oxidized. In the presence of tannic substances (pyrogallic acid, gallic acid, tannin,) which are more easily oxidized than the guaiacum, the blue color does not appear. In the same way it is absent in the presence of rapidly oxidized humus sub- stances. When absolutely uninjured roots were dipped into dilute cane sugar solutions, a reducing sugar became evident after some hours—probably this transversion is caused by a root-ferment. Starch paste, put on the growing roots of seedlings, did not give the starch reaction after a few hours, but was turned a reddish violet by iodine. The starch on touching the roots had been changed to erythro-dextrin and was soluble, passing over into the reducing sugar. The root secretions, perceptible on the tips of the root hairs, not only impregnate the membranes of the cells but can pass in the form of drops into the deeper tissue of the roots when much water is supplied and trans- piration reduced. They can erode minerals with their acids (they turn blue litmus red) and decompose organic substances. This action of the roots becomes less with increasing dryness. Roots, accustomed to a wet place, when brought into a dry one, do not absorb as energetically even after water has been supplied, if the plant has been wilted, as if it had not been wilted. Hedgocock thinks that the root hairs actually die. 1 Hedgcock, G. G., The relation of the Water Content of the Soil to certain Plants, etc. Botanical Survey of Nebraska. VI. Studies in the Vegetation of the State. 1902. 2 Experimentalphysiologie p. 189. Bot. Zeit. 1860, p. 188. 3 Molisch, H., Ueber Wurzelausscheidungen und deren Hinwirkungen auf organische Substanzen: Sitzb. Kais. Akad. d. Wiss., Wien, Section I, October, 1887. 152 The production of carbon dioxid forms a measure of the energy pro- duced by a root in raising water, boring into the soil and other life-functions. Kossowitsch has furnished quantitative determinations on this point'. He found that mustard plants in water cultures assimilated about three times as much carbon for the life processes of their roots, as was necessary for the formation of the roots themselves. The strength of the root activity, especially in lifting water, might de- pend also on the differences in temperature between the atmosphere and the soil. The greater this difference, the more energetic the work done. MacDougal’s? experiments in the New York Botanical Gardens prove how great such differences may be. He found in June, that the soil temperature at a depth of 30 cm. was at times 20°C. lower than that of the air. Naturally the water content of the soil here becomes a decisive factor and the differ- ences decrease as the soil becomes drier and more accessible to the air. The moisture holding capacity and, in sandy soils, the amount of production will depend, in the same soil, on its granular structure and will be the greater as the sand is finer grained. Livingston and Jensen* experimented on this subject. They cultivated different plant species under similar conditions, in soils which contained admixtures of different sized quartz grains in the different experimental series. It was shown that the best growth always -occurred where the quartz sand was very fine. By means of the above observations we get an insight into the distur- bances which must take place, in the activity of the roots, if the water supply of a region is less, because the ground water level has been lowered. An old tract of trees survives, because part of the deep growing roots reach the ground water level and are able to compensate the loss by evaporation of the tree crowns, when the soil water is reduced to a minimum during periods of extended dryness. The roots lying in the earth, permeated by the ground water, are adapted to these conditions. When these roots are per- manently exposed to drought they are destroyed or function feebly. Not only the economy of the tree suffers from the insufficient water and food supply, but even the soil itself, since, entirely aside from the paralysis of bacterial activity, the secreting ability of root hairs and tips affecting the decomposition of the soil also ceases. The soil becomes “Jean” and the trees begin to show dead branches in the periphery of their crowns. Since parasites settle on dying parts completing the destruction of the tissues, this blight of the tree tops is explained in the majority of cases as a purely parasitic disease and treated as such. 1 Kossowitsch, P., Die quantitative Bestimmung der Kohlensaure, die von Pflanzenwurzeln wiihrend ihrer Entwicklung ausgeschieden wird. (Russ. Journal f. experim. Landwirtschaft, 1904, Vol. V, cit. Centralbl. f. Agrikulturchemie, 1905, lek (Oy Toy Sk) a 2 MacDougal, D., Soil Temperatures and Vegetation. Repr. Monthly Weather Review for August 1903, cit. Just, Bot. Jahresb 1903, II, p. 557. 3 Livingston, B., and Jensen, G., An Experiment on the Relation of Soil Physics to Plant Growth. Bot. Gaz. Vol. XX XVIII, cit. Bot. Centralbl. 1904, No. 50, p. 617. ———— EO 153 THE DyiInc or ALDERS. Alders are most sensitive to a lowering of the ground water level and it is easy to find diseased tracts of alders near newly cut canals or regulated river beds. In the works of the Royal Biological Institution for Agriculture and Forestry at Dahlem, near Berlin (1905), Appelt has published a study of the death of alders well worth consideration. He found on the dying branches a species of the genus Valsa known to attack diseased or dead branches,—namely, alsa oxystoma—and stated that the fungus is parasitic only when the alders become susceptible, owing to abnormal circumstances. Drought is the chief determinative factor. Other disturbances in nutrition (injury to the roots, girdling, etc.) can also create a predisposition to fungus attacks but, if the alders are enabled to make a healthy growth, the disease disappears. When alders are found dying on apparently moist, imperme- able, ferruginous soils, drought may be considered to be the cause. On such soils, the alder spreads it roots only very superficially and in continued dry weather there is a very marked scarcity of water in the upper soil layers, which at once makes the alder foliage wither and dry. The beautiful tracts of trees in the Tiergarten in Berlin, especially the oaks, unfortunately show similar results from surface drought, and to an ever increasing degree. Naturally canal and river bed regulations do not always necessarily cause the lowering of the ground water level. In the old Botanical Garden in Berlin, for example, the building of the subway dried up the water in the ponds and as a further result the tree crowns rapidly became blighted. In other instances we found that the spread of brick-paving and clay- diggings near forest tracts accelerated the death of the alders because the deep clay pits had withdrawn water from the forests. The dangerous effects of lowering the ground water level often fail to impress us sufficiently, since, in some tracts of woodland, the same tree species (suffering from blight of the crowns in soils from which the water has been removed) thrive in very dry places. Under such circumstances the fact that the lack of water in itself does not cause the death of the trees, but the abrupt transition from a previously well-watered condition to great drought in the deeper layers of soil is overlooked. We may plant all our trees in very dry soils and the individuals will adapt themselves to the existing vegetative factors and the leaves will become small and coarse, the internodes short. But a sudden great change in this condition will have most serious results. If, however, such changes are unavoidable, our theory gives only one line of action to preserve the plantation,—namely, to plant young trees between the old ones. These will adapt themselves to the changed vegetative conditions. STREET PLANTING. The preservation of trees along the streets and small parks is of the greatest importance for the hygiene of cities. The greatest injury results 1 Vorlaufige Mitteilung in d. Naturwiss. Zeitschr. f. Land- u. Forstwirtschaft. 2 Jahrg. 1904. 154 from the present methods of street paving which fill the spaces between the stones with a binding material, and even at times the asphalt covers the soil entirely. The injury to the trees is two-fold; on the one hand, the air is cut off, on the other hand watering is insufficient. This affects the older trees principally. For young trees, the circle of sod around the tree is sufficient, especially if an iron grating laid over it prevents passers-by from tramping the soil. We find that old trees die much more quickly when a regulation of sidewalks and a lowering of the ground water level is com- bined with street paving. In large cities another factor must be added, 1. e., laying pipes for gas, electricity and sewers. In all this work, the chopping off of the larger root branches is unavoidable. Therefore, the root space is not only limited by the pipes, and the soil dried, but also the trees’ organs for the absorption of water are decreased. To this cause may be ascribed the gradual break up of old trees as shown by the dying branch tips. Different varieties of trees sufier in varying degrees and the linden, a favorite and most frequently planted species, is among the most sensitive of varieties. In it the dryness of the soil, with which is associated also dryness of the air, is expressed by a premature defoliation. The large leaved linden suffers more quickly than does the smaller leaved variety, and it is a well known phenomenon, that, in the summer months, when the in- habitants of the city want shade most, the linden and chestnuts often for some time have leaves only on the outermost tips of the branches. The older leaves, covered with red spider, have dried up and fallen. The city adminstration endeavors to overcome this condition by abundantly watering the ground about the tree thereby favoring a second leafing out in the late summer, which is produced even without artificial watering when the trees have lost their leaves prematurely. In this buds are forced to unfold which should develop in the following year; under such conditions a second time of blossoming is also often produced (Aesculus, Robinia). Many of the shoots artificially produced by this watering do not mature sufficiently and are injured by frost. Thus in different years, in the middle of the favorable early summer, the twigs die off accompanied by fungous infection. The winter, therefore, did not kill these less mature twigs, but made them susceptible to fungous attack, thus giving the primary cause for later death. This theory also explains the death of the cherry trees along the Rhine, which has occupied the attention of investigators during the last few years'. A Valsa (V. leucostoma) plays a part here as in the case of the alders. We will return to this case in the chapter on injuries due to frost. Such bad conditions in street planting may be avoided by a choice of less sensitive varieties. First of all, the elm should be recommended as such; this has the added advantage of being very resistent to the acid gases of smoke. Also oaks and plane trees are used with advantage according to the kind of soil present. In broad, airy streets Acer platanoides also 1 Cf, Deutsche Landwirtschaftl. Presse 1899, Nos. 83, 86, and 1900, No. 18. 155 thrives well, but suffers often from honey dew. The Robiniz, especially the so-called ball acacia, retain their foliage well even in great drought, but offer only a little shade and put out their leaves late, usually losing them early in autumn. Therefore, when Robinia is planted, arrangements for watering should be made, in which drain pipes perhaps 1% metre below the pavement are put at the distance from the trunk where the newer roots lie. These pipes can be filled when necessary from hydrants. However, atten- tion should be called to the fact that watering through drain pipes can be used only in the hot summer months, because otherwise there would be an excess of water in the soil with much more disasterous results than those due to a scarcity of water. Finally, we think that a sprinkling of the tree crown at night should be recommended especially where watering may be carried out only through the ground about the tree. We must emphatically state that watering by means of water drains can be recommended only for light soils with a permeable subsoil. By constantly watering heavy soils with a large water content, the soil will be- come baked and compacted, resulting in a scarcity of oxygen and an excess of carbon dioxid as elsewhere described, which combination will bring about the decomposition of the roots. Mangin’s' studies will be cited here as a single warning example. He worked especially on the meagre growth of trees in city planting and found the soils choked to such an extent that the carbon dioxid content of the soil air increased from. 1 to 5 and 8 per cent. and even to 24 per cent., while the oxygen content fell to 15, 10, 6 and even o per cent. Asa matter of course all the trees with such an environment will die. (Compare “Too deep planting of trees,” p. 98.) EFFECT OF DROUGHT ON FIELD PRODUCTS. The results of continued scarcity of water, felt most quickly in sandy soils during great heat, are determined naturally by the time the dry period begins. If it sets in in May, as in 1904, i. e., when growth is most rapid and the activity which should furnish the material for maturing of fruit is re- duced, the effect is most serious. In grain, sowing of summer seed suffers most under our cultural con- ditions, when planted at the usual time. This is easily understood when we consider that winter seeds sown in the autumn can, during the whole autumn and the early spring, fully develop their roots and obtain a sufficient formation of shoots. They thus utilize the undisturbed activity of their lower leaves. In this way the winter seed meets the dry period in a strong and well-prepared condition, while summer seed, even where it sprouts normally, enters upon the hot, dry period at a much younger developmental stage. Accordingly the leaves ripen prematurely, their period of work is therefore more limited and even if the plants develop blossoms and the ovaries, comparatively little organic matter is present for filling out the 1 Mangin, L., Vegetation und Durchliiftung des Bodens. Annal scienc. agro- nom. 2 sér. 1896; cit. Centralbl. f. Agrikulturchemie, 1898, p. 638. 156 grain. The endosperm is only scantily filled with starch; the grains slender and light. A second injurious effect is the shortness-of the straw. This appears especially in summer oats, which on light soils have red stalks and grow scarcely a foot high, maturing only a few small heads instead of the full ones. Barley shows less injury, wheat comes next and finally rye, the most resistent. If the dry period makes itself felt as early ‘as seeding time, the plants come up late and unequally. This leads to a double growth, i. e., to a very irregular maturing of the grain. At the time of harvest many green blades are found among the ripened ones. The former come from the seeds which were left on top at the time of sowing, and which at first did not start, while those more deeply placed found moisture enough for a speedy germi- nation. In this, limited local conditions often become effective. Thus, for ex- ample, one early crop may have drawn more water from the soil than an- other, or a potassium fertilizer is irregularly distributed and keeps the soil more moist in the spots where it has accumulated. The whole development of the plant is also changed by this. I found under otherwise equal conditions that the root shortened when the concentration of the nutrient solution in- creased and the plant’s need for water became less. This is of great signifi- cance in soils imperilled by drought. In the cultivation of sugar beets and all vegetables, grown as seedlings in small spaces and then planted out in the field, the dryness of the soil makes itself felt most of all by preventing the growth of the seedlings since no new roots can be formed in dry soil. Next under consideration is the drying of the foliage, which stops the development of the beets. Experience teaches! that, as with grain, well fertilized fields survive drought better. Varieties also show differences in this regard. It has been observed that varieties of sugar beets with outspread leaves wilt more easily than do those with erect petioles. The influence of long continued drought on potatoes shows more in its effect on the maturing of the tubers than upon their setting. The tubers remain small and ripen prematurely. As a rule, this premature ripening of early potatoes is of less consequence economically because they are adapted by nature to a shorter vegetative period and because, in the second place, they are rapidly consumed. Only the premature ripening of the later varieties is disasterous, because the tuber has a small content of starch and its keeping quality is much impaired. Leguminoseae suffer greatly from continued drought when they are grown for fodder. Clover and alfalfa burn out in spots or the second crop fails. The most frequent results with fruit trees are the premature ripening and poor keeping quality of the fruit and premature defoliation. 1 Jahresberichte d. Sonderausschusses fiir Pflanzenschutz. Deutsche Landw. Ges, 1904. 157 Among the special forms of injury which can set in during long con- tinued, intensive drought, especially in light soils, one especially deserving more thorough discussion is THE Errect oF DroucHt Upon GERMINATION. When the water scarcity occurs after the seed has passed the first stages of germination, the results are less serious, if dry seed has been sown on open ground than if seed previously soaked has been used. These dis- advantages affect the development of the young individual in varying de- grees dependent upon the kind of seed and the age of the seedlings when the drought takes place. According to Will’s repeated experiments' with seeds of monocotyledons and dicotyledons, the seeds of the former seem in general to be somewhat more resistent. The cereals without glumes (wheat and rye) are very little sensitive to a period of drought, if it occurs during germination. Barley and oats, however, are injured more easily, and the horse-tooth maize has very little power of resistance. Saussure? found that maize, beans, poppies and garden campion are very susceptible to drought during germination. Nowoczek* in his experiments repeatedly in- terrupted the supply of water, until the power of germination of the seeds was quite lost, and found that the seeds of grains resist the changing con- ditions of moisture and drought better than rape, flax, clover and peas, which lose their germinating power earlier, but even after a period of drought these seeds can be revived. Experiments on the Gramineae showed that after each drought period the fibrous roots, already formed, died, and the outermost leaves dried up, but that, when water was again supplied, new adventitious roots were formed from the first node (see Vol. I, p. 102) and the last leaves developed further. This statement applies especially to oats and to a greater or less extent to barley, wheat and maize. It should be considered as universally well-established that soaked and then carefully dried seeds, when put again into water take it up more quickly than do air dry, non-soaked seeds of the same size. Such seeds in fact germinate a few days earlier. Tautphous* and Ehrhardt® made experiments giving results which were expected at the start,—viz., that plants suffer so much the more, the further germination has advanced; i. e., the more developed the plumule is when the drought begins, the greater the damage. Will found the seed of peas in part especially sensitive to drying out. The testa was broken by many small cracks in most cases reaching into the inner layers. With re- peated soaking, the palisade layer was broken into unequal pieces, the 1 Will, Ueber den Hinfluss des Hinquellens und Wiederaustrocknens auf die Entwicklungsfahigkeit der Samen, sowie tiber den Gebrauchswert “ausgewach- sener”’ Samen als Saatgut. Landwirtsch. Versuchsstationen XXVIII, Parts I and 2 (1882). 2 Annales des sciences nat. Bot. 1827. Janv. 3 Ueber die Widerstandsfahigkeit junger Keimlinge. Wissensch. prakt. Unter- suchungen ete. von F. Haberlandt, Vol. I, p. 122; cit. Biedermann’s Centralbl. I, p. 344. 1876. 4 Freiherr von Tautphé6us. Die Keimung der Samen bei verschiedener Be- schaffenheit derselben. Miinchen 1876; cit. Bot. Jahresber. 1876, p. 882, 5 Deutsche landw. Presse, Jahrg. VIII, No. 76; cit. von Will. 158 testa became slimy and shortly decomposition set in, affecting the cotyle- dons, which hindered the development of the seedlings. The production of these cracks is due to the increase in volume of the seeds, when soaked, to more than 100 per cent.!. This produces a pressure on the testa and dis- tends it, making it porous. This porosity can lead with. drying even to: rupturing. Through these cracks in the testa, the embryo, when moistened a second time, gets much more oxygen for the food-reserve already be-. ginning to decompose, and also large quantities of water are more quickly absorbed. Further, the dissolved organic materials are transferred more easily osmotically. These may act unfavorably on further development. A testa slowly and equally distended, remaining uninjured, will there- fore probably more completely utilize the reserve substances of the cotyle- dons and perhaps indeed force the fluids into the tissue of the cotyledons and the dissolved réserves into the embryo by the turgidity produced by soak- ing. We cannot enter here more closely into the enzymes occurring in ger- mination and their action, but refer in this connection to the works of Newcombe? and Griiss?. From these experimental results it can be safely asserted that the use of seeds, which have been soaked until germination has started and then dried off, should be avoided. I am also of the opinion that soaked seed is to be used sparingly every time especially in dry regions. In the first place, in dry regions, the conditions already brought about artificially by drying soaked seeds can be repeated most easily in nature by continued heat and drought and act much more injuriously than if the seed, in such a condition, lay ungerminated in the soil. In the second place the plants become ac- customed from the beginning to an excessive water supply. The tissue be- comes more porous, richer in water and, requiring more moisture, dries up much earlier with the occurrence of great periods of drought than if the plants had developed with a scanty supply of water. The evaporation in the former condition is greater than in the latter. On this account, growers often follow the rule that for vegetable plants developing rapidly (cucum- bers, beans and cabbages) watering must not be discontinued, if the plants have had abundant water when young. I have often found that plants from soaked seeds are less thrifty than plants grown from the same seed which had not been soaked, but which depended upon the natural moisture of the soil. TREATMENT OF TREE SEEDS. If the germination of tree seeds is interrupted by drought, the results are very disasterous. This is felt most in planting trees whose seeds retain their germinative power only a short time. Nobbe* found that the seeds of 1 Nobbe, Handbuch, p. 122 2 Newcombe, F. C., Cellulose-Enzymes. Annals of Botany 1899, No. 49; cit. Bot. Jahresb. 1899, If, p. 179. 3 Griiss, J., Beitrige zur Enzymologie. Berlin 1899. Festschr. f. Schwendener, . Ueber Zucker- und Stirkebildung in Gerste und Malz, III u. IV. Wochenschr. f. Brauerei 1897, 1898. 4 Dbbner-Nobbe, Botanik f. Forstmianner. 4th. Ed., 1882, p. 382. 159 willows lose their power of germination in 5 to 6 days after they have been blown from the parent tree. The seeds of poplars and elms are also proved to be very short lived. Acorns and beech nuts, as a rule, are capable of germination only until the following spring. On an average, ash, maple and fir come under the same head. On the other hand, a large percentage of spruce and pine seeds germinate after 3 to 5 years; however, the seedlings are apt to be less vigorous. The maturing of the seed and the care of it after it has been gathered are important factors. For example, Nobbe found that seeds of Pinus silvestris, which had stood in closed glasses in a living room, germinated after 5 years to about 30 per cent. and after 7 years, to 12 per cent. In fact, even after 10 to 11 years, individual seeds were still found capable of germinating. Under the same conditions, seed of Trifolium pratense, after 12 years, germinated to Io per cent., Pisum sati- vum, 47 per cent. after 10 years and in one experiment, Spergula arvensis 25 per cent., another year 67 per cent. It is stated that cedars and Italian pines (Pinon) have germinated after 30 years‘. It is advisable to sow fine seeded conifers soon after ripening. The time of planting, whether summer, autumn or spring, is a question of practical importance. The summer is the most difficult season because the moisture fluctuates to a great extent in the soil; therefore, with trees whose seed must be sowed immediately, as willows and poplars, propagation by cuttings will obviate this difficulty. Autumn sowing is much better and necessary with oaks, chestnuts, hazel nuts, etc. It is recommended for very hard shelled seeds like those of Crataegus, Prunus, Ilex, Sorbus, Rosa, Cornus, Berberis, Ribes, Carpinus, Staphylea, Clematis, etc. The last named kinds often do not germinate for 2 to 3 years, especially in sandy soils. Spring sowing is best because the danger of winter and all injuries due to animals are eliminated. In order not to lose the time between the autumn and spring, the seeds are placed in layers between sand, which is kept damp. This process is called stratification. The importation of seeds of prized decorative trees from their native countries has become a large business. It is important to know the loss of germinating power during transportation. Count von Schwerin? in the German Dendrological Society has called attention to the fact that maple varieties cannot withstand any long transportation, so that, for years, not one of the maple seeds brought from the Himalayas had germinated. Also, the seed bed should not be broken up too soon, since many seeds retain their vitality for a long time in the soil. Thus, for example, Chamaecyparis Law- soniana often lies 4 years in the soil, especially in dry years. For years, in the trade in Magnolia hypoleuca from Japan, either no seeds germinated or so few that the costs of transportation were not paid. The seeds dried during the journey. Very encouraging results have been obtained recently by leav- ing these seeds in their fruit and packing them in powdered charcoal. tand2 Ueber das Keimen von Gehélzsamen, Der Handelsgirtner 1905, No. 14. 160 To the statement made heretofore that the seed of Acer retains its germinating power until the following spring, the qualifying statement must be added, that maple seeds of the Campestre group (Acer obtusatum, A. italum, etc.), as a rule, germinate only in the second year. Only occasional seedlings may be found after the first year. In many botanical gardens, how- ever, trees of the Campestre series are said to furnish seeds usually germinat- ing early. The explanation of this is that in seeding in such places, the first seedlings are used for propagation. From this it may be concluded that the peculiarity of producing seeds, which germinate promptly, may be made constant by selection. This point of growing the earliest germinated seed- lings separately as seed bearers, when making large seedlings, might be recommended for the consideration of plant breeders. BLASTING IN GRAINS AND LEGUMES. Under these circumstances the seeds do not mature since the plants do not have enough water. Such a condition of great drought is most often found on soils of a very porous structure where evaporation is very great and the capillary movement of water from the subsoil is slight. Yet great scarcity of water will not always produce a blasting of the blossoms. This depends essentially, as Hellriegel’s experiments with grains show, on the development of the plant when the water scarcity makes itself felt. If, following the experiments’, a grain plant has had only a scanty amount of water at its disposal, beginning at the time of its germination, it reaches maturity in a period of the same length, or perhaps somewhat longer, yet the whole growth is weak. The proportion of the harvested grains to the dry substance, however, is always normal; 1.e., approximately half of the dry substance is harvested in the form of grain. As in all vegetative conditions, there is here also a minimum; if the water supply is kept below this, no product worth naming takes place. If great scarcity of water occurs immediately after germination begins, the grains remain alive for a long time (in the experiment up to six weeks) and later develop vigorously, when the water is supplied in abundance. A period of drought. appears to be still less injurious if the grains are still in the milk stage, i.e., have reached their normal size, but have not finished their inner development and become hard. The work of the plant, which now forms no new dry substance, consists in transposing the sub- stances produced in the leaves to the storage organs, the seeds. In all periods of growth between sowing and ripening, a longer scarcity of water acts more injuriously the younger the plant is at the beginning of the drought. When the long drought sets in while the seeds are sprouting vigorously, the setback resulting therefrom cannot be overcome. The results of continued drought are the more severe, the more water the plant has had in its youth. If a plant has grown luxuriantly with abundant soil, up to the 1 Hellriegel, Beitrige zu den naturwissenschaftl. Grundlagen des Ackerbaues. Braunschweig. Vieweg 1883, pp. 589 to 620. 161 setting of the bloom, and then receives a check from a long drought, the grain is not set; a greater or less extensive failure of the harvest takes place, which we may call the blasting of the grain. Ritzema Bos’! experiments with “Maartegerst,” or winter barley sown in March, are very interesting. A sowing was made on a field where autumn sown winter barley was frozen out. Only a few of the autumn sown plants came through the winter and produced stalks during the summer so that the same field produced autumn and March sown barley. The plants from the March seeding suffered dur- ing the hot summer from blasting, while the plants of the autumn sowing, scattered among them, bore a full harvest of grain. With us, besides grain, peas suffer most. Naturally in other plants as well, a failure of the seed harvest can take place, due to the blasting of the blossoming parts. THREAD FORMATION IN THE Potato (FILosiTAs). In this disease (‘‘mules’—of the French) the eyes are deformed; from them grow slender, thread-like stems as thick as medium sized yarn. Not infrequently the eyes of tubers comparatively rich in starch did not sprout at all, or if they did, the sprouts were weak; they are unable to break through even a shallow soil covering. The tubers decay usually with the appearance of dry rot, yet the disease has occurred extensively only where the soils, being easily heated, have to withstand long droughts. Fig. 16 shows the basal part of a cutting grown in a water culture from a potato affected by Filositas; the proportions of the stem, leaves and tuber correspond to the natural size and it is seen that the stems actually are only as thick as a strong thread of yarn. The stolons (st.) are also more delicate and have formed tubercles (k), some of which have lengthen- ed at the tip and grown out to green sprouts (b) or developed scale-like green leaflets (d). 4 The cutting here reproduced came from an experimental culture, the results of which are given in precise figures in the second edition of this manual and lead to the conclusion that in the thread disease of the potato we have before us conditions of premature ripening which had become hereditary. Reports from the localities where the disease has occurred, especially from the Marchfeld near Vienna’, of the cultural methods fol- lowed there, substantiate this theory. The potatoes, which were of the earliest varieties, were forced artificially and planted as soon after as possi- ble. Sandy soils on the Marchfeld near Vienna, lime soil near Poitiers®, had a small water capacity and heated rapidly, consequently with the in- creasing summer temperature and the superficial position in the upper soil layers the growth of the aérial axes stopped at once. Tubers are formed about this time, but they do not mature, they are filled with starch so that they can be marketed very early and command high prices. 1 Zeitschr. f. Pflanzenkrankh, 1894. p. 94. 2 Altvatter, Das Marchfeld und seine Bewiisserung. Oesterr. landw. Wochenbl. Sipeue INOW pal. ® Journal d’Agriculture pratique; cit. Biedermann’s Centralbl. f. Agrikultur- chemie, 1873, No. 10 und Annalen d. Landwirtsch., 1873, Wochenbl., No. 16. 162 When young tubers are checked, ripen prematurely and are harvested, the eyes have not developed normally. Shoots developing from these eyes must naturally be weak. If such tubers are used the following year as seed a K a Fig. 16. The basal portion of a cutting grown in water from a potato tuber with the filament disease (natural size). (Orig.) for similar cultivation, these phenomena of weakness must gradually in- crease and result finally in the growth of thread-like stems only. According- ly the disease is the result of a continued unwise cultural method; viz., an 163 admissible shortening of the vegetative period of growth. To overcome this difficulty the seed must be changed since the method of cultivation will not permit the return to normal seeding. DIAPHYSIS (GROWING OUT) OF THE POTATO. In summers with little rainfall, as, for example, in 1904, one of the most frequent complaints was that the potatoes remained small or when ap- proximately normal size, showed an uncommonly large formation of sec- ondary tubers (“Kindelbildung’). In Fig. 17 is illustrated one of the most bizarre forms, which shows two kinds of diaphysis (growing out), viz., the actual “formation of secondary tubers” and “water ends.’ The stem end of the tuber (at the left side in the drawing) shows two daughter tubers Fig. 17. Prolificated potato; at the left the beginning of complete lateral tubers; at the right, subsequent elongation of the tip end (water ends). (Orig.) growing on either side at about the same relative position like the arms of an armchair. Toward the tip we find the daughter tubers becoming smaller and smaller, until near the conical end of the tuber (right side of the picture) they are recognizable only as small hemispherical processes. This malformation is caused by Prolepsis, 1. e., a premature or hurried development of the eyes. The explanation of this phenomenon is easily found. After prolonged foliage development the underground eyes of the potato plant develop tubers which store the already manufactured starch. The drier the summer, the more quickly the tuber ripens, since, with the regular enlargement and increase of its cells, the starch grains enlarge and the cell walls thicken. The cells (except the youngest about the eyes) grad- ually lose the ability to increase in size to any extent. If now, after prolonged drought and advanced ripening, a considerable amount of water is forced up into the tuber, this abundant absorption of 104 water increases the cell pressure, especially in the young eye cells with their still elastic walls, so that the eye begins to grow. Young shoots sprout from these eyes ultimately reaching the upper surface of the soil. This more un- usual condition occurs only after continued wet weather. As a rule, only passing periods of rain force the water into the tubers, an effect lasting but a short time; then the sprout remains short and thickens to the secondary tuber (Kindel). The cork layer (the skin, smooth in young tubers) shows very clearly how the cells of the ripening tubers lose their elasticity. When the tubers are very ripe the skin becomes rough in most varieties of potato, especially red ones. At first the cells of the cork layer are closely connected-with one another but, with the increasing pressure of the swelling parenchyma, the cells are forced apart, tearing the skin. Under these tears new cork cells are formed. This splitting of the skin is greater or less with different varieties. The more split a tuber of an otherwise smooth-skinned variety is, the riper it is and the richer in starch. Diaphysis of the tubers in many cases has a bad influence in that the quantity of starch which may be regarded as influenced by the soil, is de- posited in a less available form than in normal development. Together with the large tubers a great many small ones are formed, which are less mature and therefore poorer in starch. According to the investigations of Kthn* and Weidner’, the tubers already present do not become poorer in starch when the secondary tubers are formed. The starch of the secondary tubers does not come from the original tuber, but directly from the leaves. Only in plants, whose foliage is dead, does a suddenly renewed supply of water pro- duce secondary tubers at the expense of the starch content of the older ones. Both old and young tubers have only the starch content of the healthy tuber, which has not grown out. So-called “water ends” are nothing but the result of a renewed growth of the apical parts of the tuber excited by a subsequent supply of water. These are thereby lengthened into a conical form and are filled with new starch (see the right side of Fig. 17). The starch filling is just as scanty as in the real secondary tuber, “Kindel.” FORMATION OF TUBERS W1THOUT FOLIAGE. If tubers, at the time they would sprout naturally, are not put in the earth, but are kept in a dry, poorly lighted room until the next period of harvesting, a number of small tubers will sometimes begin growth. These stand either close against the mother tuber or hang from short stolons, which have developed from the eyes. While, with a timely supply of water and light, these eyes would have grown into leaved, green sprouts, in the dry, dark store-room, the sprouting eye has developed into a thread-like runner (stolon) beset with scales instead of leaves, the tip of which has thickened into a tuber. 1 Zeitschr. d. lJandw. Centralver. der Prov. Sachsen 1868, p. 322. 2 Annalen des Mecklenb. patriot. Ver. 1868, No. 39. 165 AERIAL PoTAtTo TUBERS. When tubers are not planted deeply, nor hilled up, the plant remains green, while the root is liable to be greatly injured by drought or animals. If subsequent rains cause the weakened roots to function sufficiently to keep the aérial axes alive, small, colored tubers are developed on them from the lateral eyes. This process is possible also under different conditions, yet the root must be diseased and able to convey only very small amounts of water from the soil to the leafy stems. If cuttings are taken from the older parts of the stem, they can be forced to form tubers in the leaf axils. PREMATURE RIPENING OF FRUITS. In years of continued drought, as, for example, 1904, complaints be- come most numerous that fruit does not keep. Summer fruit indeed ripens more quickly and can be brought to market one to two weeks earlier, but the flavor leaves much to be desired. Winter fruit remains smaller, as a rule, is less juicy and well-flavored and decays more quickly, or it needs a much longer time in storage in order to become fit to sell. The former may be observed with light soils, the latter has often been found! when, with heavy soil, rains occur after a period of drought, causing a further growth of the fruit which, until then, had been retarded by a scarcity of water. The condition here pictured is explained in the discussion of the fact that the quality and keeping qualities of the fruit depend upon two factors. First of all, each fruit must have sufficient time for the penetration of the water and food substances necessary for its maturity; this takes place at the time of swelling. Then the oxidation processes of ripening set in grad- ually, in which the reserve material, stored in the form of starch, is used up in respiration. The longer time the fruit has to store up the material sup- plied by the leaves, the better provided it is for the process of ripening and the better are the keeping qualities. If this process is interrupted ahead of time by drought, the processes of ripening, the conversion of starch into sugar, find comparatively little material present. In normal summer weather, i.e., alternate sunshine and rain, the fruit during the process of ripening also takes up mineral elements besides water, as Pfeiffer and I have proved. An absolute increase in mineral substances takes place shortly before complete ripening. This naturally appears relatively small in com- parison with the greater increase in organic substances. With a continued scarcity of water this increase does not take place and the fruits quickly use up the scanty materials. The acid store is scanty, the formation of sugar still less, which accounts for the insipid. taste and the poor keeping qualities. In winter fruit, processes of ripening are completed only in storage. But in all other respects the same point of view holds good. If the weather during the summer is favorable for the absorbing of large amounts of re- 1 Monatsschrift fiir Pomologie und praktischen Obstbau yon Oberdieck und Lukas, 1863, p. 272. 106 serve substances, the fruit is well prepared for storage and keeps sound a long time. If the reserve substances are scanty, the fruit rapidly spoils. In seasons after a long period of drought, which has practically stopped the development of the fruit, if a time of continued cool, dry weather comes, the fruit may start its growth again and renew its life processes. If the fruit must be harvested in the autumn, it is put into storage in a compara- tively immature condition and thus needs more time to become ripe. These are the cases (on the whole less frequent) in which the fruit must lie dis- proportionately long in storage and does not become mellow, but remains tough. Rusty PLuMs. Fox red discoloration of plums setting in some weeks before the normal time of ripening is a phenomenon of premature ripening. The fruit is still absolutely hard and, on an average, about half as large as that normally ripened. As a rule, the rusty plums fall prematurely. The phenomenon occurs only in continued hot, dry periods and is found especially on sandy soils. This discoloration occurs at different times for different varie- ties and is similar to the premature coloration, which takes place in wormy or otherwise injured fruit. It should be emphasized that the dry locality it- self is not the cause of the rustiness of the fruit, but it is due to a scarcity of soil water succeeding a period of normal precipitation. Trees whose water supply is scant, adjust themselves to conditions by dropping the fruit, which they cannot develop, shortly after blossoming. The disease only ap- pears on those trees which have held their fruit until summer under normal moisture conditions, which are then followed by a long, dry period. An abundant supply of water must be provided to overcome this, and should not be too long delayed, else not only the rusty fruit but often all the fruit, will fall. FURTHER PHENOMENA OF PREMATURE RIPENING. As a matter of course, the results of continued soil dryness after a nor- mal spring moisture are observable in all kinds of fruit. The dropping of leaves and fruit is of frequent occurrence. The scanty maturing of the organs remaining on the plant is a less common phenomenon. This produces also poor keeping qualities in stored fruits and potatoes and small grains in the cereals. We will return later to the discussion of other cases, when we consider the results of unusual dryness of air. MEALINESS OF FRUIT. Especially in hot summers on sandy soils it has been observed that fruit, especially early varieties, does not become juicy and crisp, but is tought, poor in sap, insipid rather than aromatic in taste, and when put under pressure, makes a mealy paste. In cooler years and in other localities even the same varieties do not become mealy, but change at once a firm con- dition to a liquid, winey, doughy or a decomposed condition. 167 I know of no special investigations of the case at hand. On this account it can be stated only hypothetically that the mealiness of the fruit depends upon a definite act in the ripening process, which has been directed into other chan- nels because of the scarcity of water. This change in direction might not be as- sociated with the connection of the fruit and the tree, but may set in late in the development of the fruit, about at the time when the intercellular sub- stances generally dissolve. In normal ripening of fruit, after passing the stage of great sweetness, in which the fruit is already “mellowing,” i. e., the cells of its flesh are easily separated from one another, there occur at the expense of the sugar first an alcoholic and finally an acetic acid fermen- tation. The fruit becomes winey and doughy with a constantly advancing oxidation or browning. According to Fremy', a part of the alcohol thus formed is combined with the fruit acids to form the ethers, which condition the flavor of the fruit. A cool temperature prevents the rapid oxidation of the sugar. The supply of water from the branch to the fruit, becoming less with ripening, explains the fact that, in great summer heat, the fruit develops with extraordinary rapidity and in this gives off carbon dioxid and water abundantly. In fruit, however, the flesh is poorer in water and is very easily warmed through; the reduction of the intercellular substances, which we reckon among the pectines, cannot take place in the usual way. A. Mayer” considers the pectines as condensation-products of Galactose and _the pentoses, Arahanose, and calls attention to the peculiar fact that they are jelly-like because of a special enzyme and are hydrolized by another to the pentoses. It may indeed be assumed that these processes are changed quantitatively and qualitatively when the fruit becomes mealy. This is indi- cated by the circumstance that in mealy fruit a firm connection always exists between the outer skin and the flesh of the fruit, while in the normal winey- doughy condition the outer skin can be raised easily from the flesh, i. e., the intercellular substance is dissolved. The insipid taste of mealy fruit is ex- plained by the scanty content of acid and the quick destruction of the sugar. When establishing the theory that an excess of warmth can cause a relative lack of organic acids in fruit, attention must be called again to the fact that the acids formed in the leaves during the night are in great part used up again during the following day. This process of oxidation will also take place in green fruit and it is indeed conceivable that in the long, hot summer days, this is so intensive that a large part of the acids already pro- duced disappears. Under such circumstances no vinous fermentation takes place. The fact that I was able artificially to produce the mealy process in apples favors the theory that the mealiness of fruit appears with the scarcity of water in the cells and a pasty decomposition of the cellular substance, if the conditions necessary for a vinous fermentation are not present. Fruit of various sorts was packed in layers in dry sand after ripening normally 1 Compt. rend. LVIII, p. 656. 2 Agrikulturchemie, 5th. Ed. Vol. I, p. 141. Heidelberg 1901. 168 on the trees and was kept from autumn until the next summer in a cool, light cellar, in order to let the fruit mature as slowly as possible. In this it was proved that some fruit with an absolute uninjured wax coating was still sound in August, but absolutely insipid in taste and of a mealy consistency’. BITTER PIr. In the flesh of fruit, especially of apples, brown, tough, scattered spots are produced, which sometimes taste bitter. If these are found just beneath the skin they become noticeable as somewhat depressed tough places, which, at first paler in color, finally become brown. The phenomenon is most fre- quent with porous soil in dry years, such as 1904. The firm fleshed varieties suffer less. Although a fungus Spilocaea pomi Fr. is given by some in- vestigators as the cause, I still would like to consider the phenomenon as the result of a too rapid maturing in individual cell groups in the flesh. In each fruit the tissue of the flesh seems unequally filled with reserve substances. If premature dryness of the soil prevents the accumulation of the proper amount of organic material for the complete maturity of the fruit, different tissues will remain especially poor in contents and actually complete their life 1 In mealy fruits, as well as in those normally juicy, the state of ripeness is characterized by the appearance of peculiar substance groups becoming visible immediately after the sections have been put in undiluted glycerin. The adjacent figure shows a cell from an apple (Gloria mundi) when the section had been placed immediately in glycerin. The delicate plasmatic primordial utricle . which had been contracted into folds is partially omitted in the drawing. The content is pushed together more or less. Also the very large vacuole at once notice- able in most cells, usually lying in one corner (which I would like to call an acid vacuole), is omitted in the illustration so that the substances appearing with the glycerin reaction may be more clearly apparent. Emphasis should be laid upon the fact that all cells do not show this response. The outer flesh of ripe apples, pears and peaches reacts especially well. The investigations indicate that a substance closely related to sugar is present in the cells in various transitional forms. This substance is found between isolated larger vacuoles or the numerous very small ones; it might be imbedded in the cytoplasm or be free in the cell sap, either as separate cloudy drops or in rectilinear masses which, from their appear- ance, may be dough-like in consistency. Often they are found in more strongly refractive and solid forms as tuberous, warty, irregular growths. This most solid state appears also in the form of very small, sandy grains imbedded in the cell wall, attention to which is first called when they swell up to drops or (by forming vacuoles) to small bubbles in the glycerin. All three forms have a capacity for swelling in glycerin. When observed under water, the drops become indistinct and disappear, but in extracted apple juice they remain visible and may be distinguished from the different vacuoles. The radiating middle structure of the figure shows the most marked results of the swelling, while the doughy condition of the substance is indicated by the shaded surface with curved outlines lying below this. The sur- roundings represent the part of the cytoplasmic sack, which lies in the same plane and which encloses the grains of coloring matter and two vacuoles. The process of swelling is the same in the three masses described above, but occurs in different intensities. It appears most rapidly and furthest developed in the drop form and decreases the firmer the substance becomes. With the addition of water the drops disappear first, in their place there remains at times a finely ground residue at the edge of the cytoplasm; somewhat later the doughy masses become invisible and the dividing line formed through the cytoplasm becomes circular. The polyp forms become slowly transparent; the warty masses gray grained and cloudy without dissolving entirely in one day. If, at the beginning of the entrance of water, cloudy balls, generally lying along the walls imbedded between the vacuoles, are observed, there is frequently noticed a swelling of different groups of cell contents beginning at the inside, which increases up to the formation of vac- uoles. A similar phenomenon is found with glycerin where the process sets in more slowly and the changed conditions are retained longer. By this process of swelling of the substances imbedded in the cloudy drops, the inner part of these appears at times filled by one or more vacuoles in such a way that an actual cloudy mass occurs only as a slender ring enclosing the vacuoles. This becomes more and more 169 cycle so much the more quickly. The beginnings of the disease must be sought in a rather early stage of the fruit’s development. I often found in diseased cell groups, recognizable by browned and corked membranes, many grains deposited on the cell wall. These slowly colored blue with iodine and therefore must be spoken of as starch. Some of them showed a warped seam which remained whitish. Further, a splitting of the browned tissue is observed often in the tough fleshed early apple, varieties which are most inclined to become specked. These splits are explained by the fact that when transparent in water until it can no longer be recognized. No actual dissolving of the substance has been observed. If fresh sections are laid first in water, cloudy drops do not appear, from which it may be concluded that the substance is taken up by the water. Indeed, in several cases, it was observed (in Reinettes) that if the drops had disappeared after a rapid temporary action of the water there was left a fine grained residue. With the addition of glycerin the solid grains either form drops or separate filament-like pouches. Per- haps it is only these grains which, imbedded in the drops and the remaining, above-mentioned forms claimed to be different aggregate conditions of some ground substance, swell up to polyp-like radiations. It is seen especially in the drops which are enlarged to a thick-walled vesicle by a vacuole that only some places may be elongated like pouches or chains of beads which in individual cases can reach the wall layer and thus transverse the cell as knotted bands. With the continued slow swelling in glycerin the figures change constantly whereby the substance, which becomes more and more doughy, more weakly refractive and stringy, shows an attempt to return to the drop form. Hither some of the chief arms of the aboye represented polyp-figure take up more and more substance and become broad bands which finally draw together into spherical drops, or separate beads of the chain show a stronger growth with a constant increase in size and decrease in refractive power, whereby the smaller spherical links of the chain and the thread-lke substance possibly connecting them becomes more slender, finally tearing apart and be- coming drawn into the larger drops. In most pro- nounced cases these drops were recognizable after 96 hours, but later could no longer be found nor pro- duced again by reagents. The reason that I place the substance mentioned Fig. 18. Parenchyma cell in the list of sugars, or between sugars and ferments, from the flesh of a ripe is their occurrence in the same cells, which contain apple after treatment with large, strongly refractive drops capable of being undiluted glycerin. (Orig.) drawn together by glycerin, or separated by alcohol and showing a copper reaction into which it seems to me pass over the small, above-mentioned drop forms. The large syrup drops which may be drawn together in certain parts of the cytoplasmic sac by glycerin and which gradually disappear again, may be partially fixed by the use of the potassium bichromat since a persistent brown-grained precipitate is formed. In pears I found this phenomenon after the action of dilute sulfuric acid on the glycerin preparation in which the walls of the stone cells became the color of wine. Ferric chlorid gives no special color reaction. If a piece of caustic potash is put in the glycerin prepar- ation the syrup balls color an intense yellow and the remaining cell content a lighter yellow. Chemically pure grape sugar behaves similarly but, dissolved in pure water, it gives only a weakly yellow liquid. The addition of calcium chlorid or calcium nitrate will hold the drops in form somewhat longer. They then retain their strong refractive power from 2 to 4 days. With the use of silver nitrate a brown grained precipitate is produced in many syrup balls, which consists either of many very small grain bodies or less numerous larger tuber-like ones. A part of the drops disappear without giving any precipitate. It seems to me that we are concerned here with an extremely easily changed substance, easily soluble in water and alcohol, but less soluble in glycerin, which occurs in the same cell in different transitional stages, thus howing different re- actions Even exposure to the air brings about a change, since an apple, which shows a quantity of drops on its freshly cut surface, does not show any drops on this same cut surface after a few hours when acted upon by glycerin, and these may only be found again deeper in the tissue. 170 the fruit was attacked by the disease, while the cork layers were swelling, the specked tissue had already lost its elasticity. The dying of single tissue groups of this kind as the result of an in- sufficient storage of reserve substances will take place so much the more " easily as the deposition of starch is made more difficult by the one-sided in- creased nitrogen fertilization. In fact, practical fruit growers have also observed that this specking is especially abundant, if the trees have been excessively fertilized with sprouted malt, hornshavings, etc. Wortmann! substantiates our theory in regard to the non-parasitic character of the specks and of their occurrence with a scarcity of water. He ascribes the appearance of the dead cork cell groups to an excess of acid which is brought about by the concentration of the cell sap of the fruit as a result of unreplaced water loss. The absolute acid content decreases with the ripening of the fruit, but the relative acid content becomes increased with scarcity of water in the cells. Wortmann concludes from his investi- gations of the epidermis that the larger fruits evaporate more than the smaller ones and the specked varieties (reddish Reinette, Goldgunderling, King of Pippins, Landsberger, green Stettiner, Danziger) evaporate more than do the varieties not inclined to specks. He found a greater thickening of the outer walls of the epidermis in the non-specked varieties, the peeled specimens of which evaporated more than did peeled specked apples. If the fruit of non-specked varieties was pricked with a needle and laid in acid or alkaline solutions (potassium, tartarate, limewater) specks were pro- duced which could not be distinguished from natural ones. The phenomenon of the so-cailed “fly specks” should not be confused with this. Very fine little black points united into groups are found on the apple peel, which appear to the naked eye like a cloudy bloom and under the microscope look like accumulations of fly specks. Fungi, especially Leptothyrium pomi Mntg. and Fr. and Phyllachora Pomigena (Schw.) Sacc. are given as the causes. Often actual insect secretions are found in which fungi grow. Since the skin under the “fly-specks” does not seem to have been injured in any way, rubbing with a damp cloth is enough to make the fruit again fit for sale. Another phenomenon, often called specking, is the “rusting of the peel.” This term comes from the change in color of the outer skin. During the process of swelling, the skin gets stellate or den- tritically-branched tears, which are closed by the formation of cork. STONINESS OF PEARS AND LITHIASIS. When pears are grown on poor soils, in dry years the flesh is solid, but grates between the teeth when eaten, in wet years the flesh is tender and does not grate between the teeth. This grating is due to the extraordinarily large amount of stone granules formed in the years of drought. Practical workers often maintain the theory that the formation of stone cells in pears is the direct result of great drought. 1 Wortmann, Jul., Ueber die sog. Stippen der Aepfel. Landwirtsch. Jahrbticher 1892, Parts 3 and 4. tyt Investigations of young fruit show, however, that in each variety of pear in normal development aggregations of coarse-walled schlerenchymatous cells are always present unequally distributed. These stone cells are in fact an anatomical characteristic differentiating pears and apples'. Therefore, it is not the occurrence of the stone cells but only the greater thickness of the walls already formed which is the result of the drought. In many varieties they remain relatively thin-walled. To this should be added that their con- nection with the surrounding tissue is tougher and closer in dry years. In the so-called stoniness of pears, only the increased wall-thickening? of the normally deposited schlerenchy- ma cell centres is concerned and there- fore no increase of the elements, while we find in Lithiasis an accumulation of stone cell elements produced subse- quently by cell increase. These finally | may also extend over the surface of the fruit and then form light brown circular specks, either equally distrib- uted or clustered on the sunny side or even map-like etchings due to the run- ning together of the specks (Fig. 19), the upper surface of which shows a crumbly construction. Not infrequently the same yarieties’-of peari7 sitter also from Fusicladium (see Vol. IT). Nevertheless, the Lithiasis specks may be easily distinguished from the smooth, usually blackened, fungous specks, be- cause of their crumbly constitution and the raised edges of the wound. So far as observations have shown as yet, only certain varieties suffer from Lithiasis. Many, in fact, form predominantly roundish specks, while 3 : : Fig. 19. Pear diseased with in others usually zigzag gapping cracks iiehiasia: © COrie) are produced. Stone masses are not always depressed, often they occur on the upper surface as pale cork-colored cushions. An entirely normal construction may be found in the healthy parts of the pear attacked by the stone disease; i. e., underneath the small celled, not 1 Turpin, Memoire sur la difference qu’offrent les tissus cellulaires de la pomme et de la poire etc. Paris. Compt. rend. 1838, I, pp. 711 ff. 2 The substance, of which the stratified thickened walls of the stone cells con- sist, has received the name of glycodrupose from Erdmann*. He used this name because he thought that the chemical composition of these cells is the same as that of the tissue of stones of plums and cherries (Drupaceae). The substance, decom- posed by moderately concentrated hydrochloric acid, gives half its weight in grape sugar in solution. The half remaining undissolved is called drupose; when boiled 172 very thick-walled, colorless epidermis (Fig. 20 ¢) lie three or four layers of usually tangentially elongated or cubical parenchyma cells (~) which are richer in cytoplasm than the deeper lying tissues and contain chlorophyll, but no starch. The starch is found to appear gradually first in the inner flesh and its grains usually increase in size toward the core. Underneath the outer cell layers, rich in chlorophyll, the deposition of the stone cell centres begins (st). These form groups of a few cells in the normal flesh; in the coarse fleshed fruit they are separated only by small intermediary areas of delicate parenchyma (zp). From the periphery toward the in- terior of the fruit, the stone cell groups become more scarce and the sur- rounding parenchyma assumes a stellate arrangement. In the first stages of the disease, we find in fruit, which is always green and hard, that, underneath the uninjured and colorless epidermis, individual cells contain no chloroplasts, but have a brown, strongly refractive cell con- tent, which is massed together in lumps. The number of these browned cells gradually increases and ruptures the outer skin. Beneath the ruptured place which, by the drying and crumbling decomposition of the tissues forms a depression (gr), a brown-walled dying tissue (br) is found in the midst of the flesh, which later may rupture and form cracks. Often in these cracks, and always in the open peripheral pits (gr), may be found a colorless slender mycelium which is a subsequent infection and may hasten the decomposition of the tissues. . A most striking phenomenon is the fact that when the pit has been formed the flesh tissues no longer die and closed masses of newly formed schlerenchymatic tissue begin to push out like cushions with a radial struc- ture (f). These cushions of stone cells force the dead bark (t) tissue out and off. In cross-section the individual elements of the stone cell cushions are square or rhomboid, and lie almost unbrokenly upon one another. Even in with nitric acid and washed with water, ammonia and alcohol this leaves behind a yellowish white cellulose. Erdmann concludes from his investigations that the substance of the stone cells may be produced from a carbohydrate by the loss of water and nitrogen from starch or gum, while in the normal process of ripening, water must be taken up for the formation of the sugar. The theory that the formation of sugar and of cellulose are most closely connected is given expression by DeVries**. He says that usually an accumulation of grape sugar is found in those young cells which later strongly thicken their walls. For example, the bast fibres of clover as well as fibres of the inner fibrous sheath of the vascular bundles, which appear to be very thick walled in a mature condition, are rich in grape sugar in their younger, still thin walled stage, while the surrounding tissue is poor in sugar or lacks it entirely. DeVries found the same conditions in the young bast fibres of potato and maize. Even in the hairs, which are thick- walled later, an accumulation of sugar takes place before the thickening of the walls, thus, for example, in the hairs of young clover leaves, in whose parenchyma, however, no sugar could be proved. In the same way, according to DeVries, sugar can not be found in the root parenchyma of this same plant, while in the young root hairs it occurs abundantly. The possible transversion of cellulose to dextrin and sugar by the action of dilute sulfuric acid after heating is well-known. With this the recent investigations on the Hemicelluloses; mannen, galactan and araban, should be compared. * Liebig’s Annalen, Vol. 138, p. 101; cit. im Jahresbericht f. Agrikulturchemie 1866, p. 99. ** Wachstumsgeschichte der Zuckerriibe, in den Landw. Jahrb. 1879, p. 438. 173 While the normal stone cells usually remain yellow will dissolve easily in sulfuric acid without any observable precipitation early stages they color a bright yellow with Anilin sulph. and when oldest of gypsum crystals. One Reeser WS HO meena s \y PINE S eos a ay. 26 yi Some Be GOs 5) (Orig. ) Cross-section of a stone cell cushion from a pear diseased with Lithiasis. Explanation in text, 174 from the effect of zinc iodid of chlorid, the elements of the schlerenchyma cushions, which were formed later, turn blue after some time, either throughout or in the innermost lamellae of the walls. The growth of these schlerenchyma cushions takes place in a meriste- matic layer (m) formed underneath the dead bark and appears at first as if it would develop into a flat cork layer, cutting off the centre of the diseased tissue, as may be observed in the Fusicladium cushions. This, however, is not the case. The meristematic layer is active as long as the fruit is green and growing. Toward the periphery it forms new thin-walled bark cells (usually in small numbers) which again are gradually attacked by bacteria and fungi, while on its inner side, toward the (usually seedless) core, the thick-walled elements of the stone cell cushions are increased. The radial arrangement of the cell rows in these is explained by the tension of the tissues which the swelling of the unripe fruit causes. If, in this, the new formation of stone cells is greater than the distension of the parenchymatous tissue of the fruit flesh, the stone cells are pushed out like cushions. As a rule, however, both processes keep step and finally, by the death of the pathogenic meristem itself and the breaking of the connection between the outermost stone cells, is produced the crumbly constitution of the stone spots. It is a matter of course that fruit attacked by Lithiasis is unfit for consumption. Since this phenomenon is not found in all varieties, and not every year even in the same varieties, but is a destructive factor only on dry soil in dry years, the supposition, that the stock used in grafting influences the problem, seems probable. Weakly growing stock which cannot take up sufficient amounts of water from a dry soil for a rapidly growing top, because of its small root area, will favor this stony condition. If, on this account, the dis- ease should occur repeatedly in the case of dwarf trees on light ground, an attempt should be made to graft pears on the most rapidly growing varieties of quince. When standard trees are in question, an attempt to overcome the difficulty should be made by renewing the soil, fertilizing the sub-soil and watering abundantly; in obstinate cases, by means of renewal of the top by pruning after fertilization. Some method of forcing the fruit to swell as rapidly as possible might best protect it from an excessive formation of stone cells. VARIETIES OF FrRuIT SUITABLE FOR Dry SOILS. The guiding idea of our manual is that many diseases of cultivated plants may be prevented by a more careful consideration of the relation between the character and habits of the plant and its environment. In accordance with this plan in treating diseases favored by drought, we men- tion a number of well-known varieties suitable for dry soils’. 1 Oberdieck, Deutschlands beste Obstsorten, Leipzig, Voigt. 1881. L. indicates that the variety is recommended to the agriculturist. Str. suitable for planting along streets. The name of the month after that of the variety indicates the time of complete ripening. 175 Apples: Summer Rose, End of July. L. Str., Scarlet Pearmain, Au- tumn. L. Str., Landsberg, Autumn. L. Str., Dantziger, Autumn. L., King of Pippins, Winter. L. Str., Orleans, Winter. Str. (For the agriculturalist where the soil is better), Yellow Bell flower, Winter. L. Str., Alant, L., Deutscher Gold Pepping*, Winter. L. (must be left on the tree until the middle or end of October), Kassler, keeps from winter until summer. L. Str., Purpurroter Cousinet*, winter till summer. Pears for dry soils: Hannoversche Jakobsbirne*, end of July. L. Str., Clapp Favorite. August. L., Archduke, August. L., Yat, beginning of Sep- tember. L. Str., Kuhfuss*, beginning of September. L. Str., Treyve, Sep- tember. Autumn Melting (Downing), end of September. L. Str., Bosc, end of October. L., Marie Louise, beginning of November. L. Str., Mecheln, December. Madam Korté*, January. Kemper, cooking pear for the whole wanters 1!) Str: Cherris, as is well-known, prefer a well drained, dry soil; on the other hand, plums, on the average, flourish best in a moist, heavy soil and also they bear sweeter fruit. It is desirable to know a number of varieties re- quiring less water. Biondeck, beginning of August; early Apricot, middle of August; Lawson, end of August; Bunter Perdrigon, end of August; Berlepsch, beginning of September ; Altham, beginning of September ; Jerus- alem, beginning of Septembr; Anna Spath, middle of September; German prune, end of September. As a street tree, the plum is not very desirable because of its habit of growth. As varieties which grow well on dry, light soils in the climate along the coast, should be mentioned': 1. Apples: Landsberg, Purpurroter Cousi- net*, Oldenburg, Geflammter Kardinal*, Bauman; the Prinz (Downing) is especially suitable for the provinces along the Baltic and the North Sea. 2. Pears: Yat Bosc, Red Bergamot, Summer Doyenne. 3. Plums: House Plum. 4. Cherries: The common sour cherry. STUNTING. Since almost everywhere in nature similar effects are obtained by different means, a limited soil space may be only one cause of dwarf growth; another is the lack of available nutriment due to either a scanty supplying of raw soil solution to the roots or to the decrease of organic reserve nutriment. This latter case we will have to consider again later in the “Pincement Grin,” i. e., in the pruning’ of leaves to prevent the sprouting of the buds found in their axils and in the production of dwarf seedlings by cutting off the cotyledons which are rich in nutrition. In nanism, however, caused by soil physically unfit because of too great porosity, water scarcity alone must be considered. Given a soil rich in mineral or organic food substances, the size of the plant depends upon the distension * Name of variety given in the German original, not reported in the United States of America. 1 From a written communication of Mr, Klitzing (owner of a nursery) in Ludwigslust. 176 of the individual cells, due to the turgor produced by the water from the roots, and the conclusion is at once reached, that a scanty supply of water during the time of growth must produce small dwarf specimens. Each excursion through sandy regions, in which a damp subsoil is either lacking or lies very deep, furnishes examples enough for this fact. I have published detailed measurements concerning the shortening of cells due to a scarcity of water'. Moller? furnished experimental proof of dwarfing due to scar- city of other food substances with an excess of water and also confirms the principle that in slightly concentrated nutrient solutions the root increases relatively in size. Mobius* has arrived at the same result in his comparative cultures with Xanthium in sand and loamy soil. He found the roots and stalks of plants grown in sand branched more than those of plants grown in loamy soil, while the leaves were more slender and the glandular hairs fewer in number. On the other hand, in plants grown on loam the content of calcium oxalate crystals seemed smaller. The thorns were smaller on sandy soil, but the walls of the lignified cells seemed considerably thicker. Comparative studies of the influence of dry or wet localities were made by Duval-Jouvet. These proved that in dry, hot places, a formation of the hard, bast bundles is especially favored, but is retarded in shady, wet posi- tions. Volken’s observations’ on Polygonum amphibium in the forms grown in sand, heath and water, are very thorough. In the sand form the circum- ference of the stem is smaller, at the expense of the central air canal; the bark cells are more heavily thickened, while between the bark and the phloem, a rather broad ring of uncommonly thick mechanical cells is en- closed. A closed wood cylinder is formed, the vascular system in which is almost 2 to 3 times as strongly developed as in the water-grown stem; in the latter, the absence of thick-walled elements and the occurrence of large air holes facilitate floating. The petioles of the water form, which have no mechanical reinforcement, may become six times as long as in the land form, the midribs of which are strengthened by strong collenchyma cords. The palisade cells are more strongly developed in the water plants, but these lack, on the other hand, the strongly developed bristles on the upper sur- face and here also the somewhat larger epidermal cells which in the land form contain a slimy content, explained by Volkens as a water reservoir in times of great drought. In the well-known Rose of Jericho (Anastatica hierochuntica), that plant of the desert which closes together like a head when dry, the inclination of the branches toward each other arises from the fact that the wood cells on the different sides of each branch possess a different capacity for swelling longitudinally, which goes hand in hand with an unequal lignification. 1 Sorauer, Bot: Zeit. 1873. 2 MOller, Beitrige zur Kenntnis d. Verzwergung. Landw. Jahrb. 1893, p. 167. 3 Mobius, M., Ueber den Einfluss des Bodens auf die Struktur von Xanthium spinosum usw. Ber. d. Deutsch. Bot. Ges. 1905, Vol. XXII, Part 10. 4 Duval-Jouve, Anordnung der Gewebe im Blatte der Griaser. Bot. Jahresb. v. Just 1875, p. 432. 5 Volkens, Beziehungen zwischen Standort und anatomischem Bau der Vegeta- tionsorgane. Jahrb. d. Kgl. Bot. Gartens zu Berlin, Vol, III, 1884, p. 46; cit. Bot. Centralbl. 1884, No. 46. 177 From the beginning one must note that every limited supply of nutri- ment which leads to nanism must express itself mostly in the amount of additional growth, i. e., in the formation of the secondary tissues. An ana- tomical proof of this has been furnished by Gauchery®, who cites cases when the cambium has formed anew only a few rows of cells. Often he could no longer determine any meristematic zone whatever between phloem and xylem; therefore, the original cambium must have passed over at once into permanent tissue as the result of deficient nutrition. In the plants which are forced to grow in sandy or stony soil, often with a lack of water, a form of hyperplasia’ (arrested developments) appears. It is not so much the number of the cell elements which seems to be decreased, as their size. Thus specimens are formed which we would like to call “stunted plants.” By this is understood woody plants, the growth of which is not retarded to dwarfing but which, by the striking shortening of their axial organs, show a repressed, knarly habit of growth. In this habit of growth the very evident, increased spiral twisting of the woody elements of the trunk counts as a typical characteristic. The finest examples are seen in Syringa and Crataegus. We can explain the production of the increased spiral twisting if we think of the direction of the woody cells as the diagonal of the parallelogram of two forces. At the apex of each elongating axis there is, on the one hand, an effec- tive striving toward growth in length in which the elongation of the pith body becomes a decisive factor of swelling; on the other hand, the general enlargement of the young cells acts also as the cause of the radial enlarge- ment of the trunk. In considering a very young wood cell in the cambial layer, stretching longitudinally, we see that, as the growth in length predomi- nates over the growth in thickness, it is relatively difficult to divert the cell from its longitudinal growth. However, as the abundantly formed young wood cells, during elongation, are pressed outward by the growth in thick- ness of the medullary cylinder in the direction of the radius of the trunk, proportionately just so much the sharper will be their spiral twisting. On this account we find long slender shoots with a slight spiral twisting in plants on moist nutrient soil, and on sandy soils poor in water, or with other checks to growth in length, plants having short axes with strong twistings. Confirmation of the hypothesis is found in the “enforced twisting” to be mentioned later. The more the stems are distended like barrels, the sharper is the spiral twisting of the cords of the leaf spur. We mention this point because the occurrence of such strongly twisted stunted plants is valuable as a symptom in judging the soil conditions. PILOSIS. Plants grown on dry soil soon have a hairy appearance, even if no more hairs are formed than on specimens of the same variety growing in damp 6 Gauchery, Recherches sur le nanisme végétal. Ann. sec. nat. Bot. 1899. VIII. ser. t. EX: 1 Kuster, E., Pathologische Pflanzenanatomie, Jena 1903, p. 21. Here abundant bibliographical citations. CO 17 places. If a definite number of hairs are formed on a leaf, these are closer together in a given small area, because the epidermal cells separating them are shorter. This partially explains why alpine plants appear to be less pubescent when grown on plains. These plants grow more luxuriantly, the dimensions of their organs become larger and the hairs are separated further from one another. But, in fact, even in dry localities, an increased hair for- mation takes place. Thus Moquin-Tandon!’ cites observations by Linneus, that the Lady’s Thumb (Polygonum Persicaria L.) seems very smooth at the edge of bodies of water, but beset with hairs in dry places. Our field thyme (Thymus Serpyllum L.) loses its glaucous surface at the sea shore and acquires a short, hairy covering. Our Turk’s cap lily (Lilium Marta- gon L.) when cultivated for some time in gardens is glaucous, but becomes pubescent again, like the wild plant, when grown on poorer soil, etc. Such phenomena may be observed also in garden plants which, self-sown, grow on sandy places in the fields. An unusual hair growth takes place, further, in many parts of plants when they no longer develop normally. According to Moquin-Tandon, the stamens of the triandrous bindweed are covered with thick wooly hairs. The stamens of several kinds of Mullen (Verbascum) behave similarly if the anthers become deformed. The peduncles of the smoke tree (Rhus Cotinus) are almost without hairs before blossoming and if they bear seed. If, on the other hand, the fruit does not mature, the stems of the sterile blossoms grow longer and numerous, long, violet colored hairs appear on them. The last-mentioned formation of hair does not belong among the phenomena connected with drought, but should be considered as a process of correlation. The water and nutritive substances, which should be utilized in the maturing of the anthers or seeds, are used in a greater measure for the benefit of other parts of organs, when the sexual organs are destroyed. Possibly the phenomena recently observed in parthenogenesis belong in part here, where the micropyle is stopped up as the result of the hair-like elon- gated cells of the style tissue or of the integuments’. Also, we find in the root system that pubescence varies according to the place where the root is kept. In the same varieties, the whole system can develop into the form of long, slender, whip-like, scantily branched, bare, or almost bare roots, if the root axis dips into water or into porous sand saturated with water. The root branches become shorter, more knarled, branched and pubescent, the drier the soil is in general ;—the more, therefore, that the root is obliged to depend only on the moist air of the soil interstices. In air which is absolutely dry, the roots (according to Per- secke*), do not develop any more hairs. If the roots are exposed to moist air, the young tips, just behind the growing apex, become very hairy, be- cause almost every epidermal cell has pushed out into a hair. 1 Pflanzen-Teratologie, translated by Schauer, 1842, p. 61. 2 Winkler, H., Ueber Parthenogenesis bei Wikstroemia. Ber. d, D. Bot. Ges., Jahrg. 1904, Vol. XXII, p. 573. 3 Persecke, Ueber die Formverinderung der Wurzel in Erde und Wasser. Inauguraldissertation, Leipzig 1877. In the aérial parts of plants, which are accustomed to dry air, the de- gree of humidity must be strikingly low if the formation of hair is to be greatly stimulated as C. Kraus’ states when writing of potato sprouts. In very moist air potato sprouts from the same variety are hairless, or have only a few shortish hairs. Therefore, in aérial organs, it is the influence of moist air in contrast to dry air which prevents pubescence. In roots, de- pending mostly on water, the same effect is obtained by a continued supply of water just as the influence of moist air favors pubescence. An extreme formation of hair on aérial and subterranean axes is there- fore the result of causes acting in the same way; the usual necessary amount of water is withheld from the plants at the stage in which they are develop- ing. In explaining the fact that greater dryness of the environment favors the formation of hairs, Kraus and Mer? have cited the phenomenon that the organ’s growth in length is modified or arrested with the formation of hairs. Both investigators are of the opinion that the material saved by the arrested elongation of the cells of the axis, is utilized for the formation of hairs. Besides the examples of Rhus, etc., cited above, Heckel’s* observa- tions support the theory that a scanty formation of other organs goes hand in hand with a very abundant development of hairs. Heckel found speci- mens of Lilium Martagon L. and Genista aspalathoides Lam. with an un- usual hair covering together with a reduction of the blossoming parts. Kraus emphasizes the fact that, with the decrease of growth in length, an increase in turgor takes place transversely in the whole organ (as we have assumed in the development of the pith of stunted plants) which extends to the epidermal cells and excites these to the pushing out of hairs. Vesque’, like Mer and Kraus, states that increased transpiration favors hair for- mation. Attacks of parasitic animals often excite the epidermal cells to an enormous, fine growth of hair, for example, such as mites which injure the young leaves with their mandibles and thus produce the so-called felty dis- ease. These hair formations are described under galls. In the older my- cology, such hair felts, produced by the sucking stimulus of mites, are de- scribed as fungi (Erineum Pers. Taphrina Fr., Phyllerium Fr.). LIGNIFICATION OF Roots. The lignification of tuberous roots is due to the return to the original prosenchymatous woody condition of cells in the vascular bundles which, under cultivation, have become parenchymatous. The carrot, for example, which serves us as food, descends from a plant whose root consists of a 1 Kraus, Beobachtungen itiber Haarbildungen, zundichst an Kartoffelkeimen. Flora 1876, p. 153. 2 Mer, Recherches expérimentales sur les conditions de développement des poils radicaux. Compt. rend. LXXXVIII (1879), p. 665. 3 Heckel, Du pilosisme déformant dans quelques végétaux. Compt. rend. t. XCI, 1880, p. 348. 4 Sur les causes et sur les limites des variations de structure des végétaux. Cit. Bot, Centralbl. 1884, No. 22, p. 259. 180 strong, hard, wood body with a thin, tender bark. The cells of the wood tissue, like all the other wood cells, are thick-walled, spindle-shaped and wedged between one another. In the cultivated root, instead of these wood cells, thin-walled, short cells are present, ending almost bluntly against one another and even the ducts which lie in scattered groups between the par- enchymatous cells are but little lignified. The latex tubes already formed in the bark, when spiral porous ducts are produced in the wood body, have broadened like all the cells of the bark. Instead of the starch which, in the wild carrot, fills out the whole bark tissue, occurring here and there in the wood body also and increasing to 70 per cent. of the dry weight, sugar has been formed usually in good table carrots so that only traces of starch may be found. The better the variety, the less the starch content as in the Dutch pale yellow and the Duwicker carrot. Gradual transitions are found back toward the wild plant in other cultural varieties used as fodder, such as the Altringham carrot and the white horse carrot. Specimens of all varieties found on poor soil go to seed as a rule in the autumn and are dis- tinguished by a thin, often divided, root which, because of its lignification, recalls clearly the ancestral wild carrot. The same behavior is character- istic of the turnip-rooted cabbage, Swedish turnip, radishes, Kohlrabi, etc. These differences are best made clear by comparing the anatomical structures. In Fig. 21 is shown a longitudinal section through a two-year old wild carrot. In this figure a is the vertically elongated parenchyma of the pith-like central part with scattered spiral, porous ducts; b the xylem, made up of spindle-like wood cells together with ducts and the part of the medul- lary ray which extends toward the secondary cortex; c the cambium which has become an elongated, thin-walled parenchyma; d the secondary cortex with its resorption spots which follow the course of the latex ducts; e the primary cortex; f cork. Fig. 22 is a corresponding section from a two-year old cultivated carrot. The letters in both figures indicate the same parts and a comparison of the similarly designated tissues makes very clear the change in the wood tissue and the increase in the dimensions of the secondary cortex in the cultivated carrot. In all tuberous vegetables lignification also occurs normally when they grow too old and then this process, as in individuals lignifying prematurely, is accompanied by a partial disappearance of the sugar. It is well-known, from experience, that many of our vegetable plants lignify in hot climates. Precautions against this latter condition will be hard to find since the tropical warmth and excess of light favor rapid lignification. In cultivation in temperate climates, lignification can certainly be avoided by abundant watering and fertilizing ;—only care should be taken in this that the land is deep and the seed good. Special attention should be given to the choice of seed, because seeds from dry localities carry with them a great- er tendency to lignification and to a repeated division of the root. Batt DRYNESS OF THE ERICACEAE. The peculiar sensitiveness of the roots to drought must be taken into consideration when growing the numerous species and varieties of the Ericaceae as Erica, Azalea, Rhododendron, etc. These plants cannot endure 5) a ie to " re = govegegiore atatabat ‘JO1IVO PIIM PIO Teak OM} ysnoayy yno yeurpnyLsuo'yT ‘OLIV pe}BA[No plo «ved OM} V YSNOAYI JNO [eUIpNyLsuo'T -~ 5 Ee ~~ 59 i —— = — i} Q PF oe TURAN Aretoimarap re OUT CRN STI tig ge a a ee cE OAM TINT EMA IN MGA A! LOT ACH vu pw eae se a Anan == SRE ESS es a complete drying out of the roots. While other plants can survive lack of moisture, even repeated wilting, without showing any noticeable injury, and even continue growth after being again supplied with water, the fine root branches of the Ericaceae do not seem able to resume their functioning when once entirely dry. In one case I investigated the roots of an Erica 182 gracilis which, after they had dried out, had been subsequently soaked 24 hours in water, and found that the fine root ends were still shrivelled despite the soaking. The character of most Ericaceae, as moor and heath plants, is shown by the fact that (with the exception of a few varieties) they thrive best in a freely watered, easily drained, aérated soil. In growing plants in small pots the need of roots for air must be given the greatest possible consideration. The Ericas soon become root bound. The plants easily become sour in large pots. The Erica and Azalea drop their leaves when dried out. It is wrong, however, to try to repair the previous mis- take by setting the pot in water and, after soaking up the earth, to place the plants in closed cases in order to reduce evaporation as far as possible and to cause turgidity. The plants should be left, on the contrary, in their customary place, but strongly shaded during the middle of the day. MEANS OF OVERCOMING LACK OF MOISTURE IN THE SOIL. If a lack of soil moisture is manifested by the failure of vegetation or by its degeneration, as usually occurs more frequently in sandy soils, one naturally seeks relief in irrigation when possible. This artificial supply of water not only refreshes the tissues, but also, by dissolving the nutritive substances in the soil, it is possible for the plant to utilize and distribute these. IRRIGATION. With the frequent lowering of the ground water level, irrigation be- comes a vital question and an acquaintance with the results of Konig’s' investigations on the effects of irrigation water is interesting. One learns accordingly that when a meadow is being irrigated the water loses much of its nutritive material and appreciably more during the warmer seasons, than in the colder ones. This loss, however, is not true of all nutritive substances. If the carbon dioxid content of the irrigation water rises, the calcium and magnesium nearly always increase instead of decreasing. As in the case of carbon dioxid, this quantity seems to rise and to fall with the intensity of the oxidation in the soil. In contrast to the above-named nutritive sub- stances, potassium appears to be absorbed at any time by the soil since, with irrigation, even in the winter, a slight reduction of this important mineral can be proved in the water. Sodium, or rather sodium chlorid, just like nitric and sulfuric acids almost always showed a slight increase during winter irrigation, while during the growing season they decrease, 1. e., they are taken up directly by the plants. Konig concludes that the oxygen of the water acts as a purifier of the soil by oxidizing the organic soil contents. This oxygen content varies according to the kind of water used in irrigation and the season. Konig found it greatest ‘in spring, smallest in summer, increasing again in the autumn. Spring water is much richer in oxygen than river water which has passed through inhabited places. The opposite is true of the suspended 1 Journal fiir Landwirtschaft. Jahrg. 1280. Vol. 28. Part 2. 183 organic substances which are taken up from the soil by impoverished spring water, which has a small oxygen content, but are deposited, on the other hand, by the richly saturated river water. At a depth of 40 cm. during the colder seasons temperature observations show that irrigated land is warmer by varying amounts, even up to 2.8°C. To this increase in temperature may be ascribed the fact that in irrigated meadows, growth begins earlier in the spring and continues later in the autumn. Konig showed by an experiment in which he artificially mixed sewage with the irrigation water, how quickly the subsoil shows its absorption qualities, if the soil is not saturated and the irrigation water is heavily charged with fertilizing matter. After the water had been used once, it could be proved that the soil had taken up 84.5 per cent. of the organic substances ; 74.2 per cent. of the ammonia; 81.6 per cent. of the potassium and 86.8 per cent. of the phosphoric acid. After the same water had been used twice again the presence of these substances in it could not be proved at all. Of course these figures hold good only for this experiment and vary according to the saturation of the soil and water; they have therefore, for example, no value in irrigation with liquid manure, in which the soils must become surcharged with nutritive substances in a comparatively short time. Nevertheless, experiments show what varied advantages can be obtained with the right use of irrigation. The importance of watering the soil arti- ficially is becoming more and more acknowledged. The best proof is found in the transactions of the land cultivation division of the German Agricul- tural Society’ in which questions referring to the direct supplying of water, raising of the ground water level, have already been brought up. The sys- tems known at present have been partially explained by means of illustra- tions. The transactions have led to a direct commission from the Directors of the society, “that they should take up the question of the watering of land with the greatest possible energy.” CULTIVATION OF THE SOIL. At present, in large plots of land, it is possible only in the rarest cases to provide for irrigation without considerable expense and therefore cheaper, if less effective, means are more often utilized. Such resources are found in working the soil. The breaking up of the soil is most advisable. Some practical workers maintain that cultivating the field soil cannot possibly aid in the retention of soil moisture, but that this manipulation must rather be considered as the quicket way to remove more water from the soil. This point of view is erroneous, as is shown by many experiments. The most thorough are Wollny’s*, who has worked with control experiments and has found that if the uppermost layers of the soil are broken up, they dry more 1 Die Méglichkeit der Ackerbewasserung in Deutschland. Arbeiten d. Deutsch. Landwirtsch.-Ges., Part 97, 1904, p. 75. 2 Wollny, Einfluss der Bearbeitung und Diingung auf die Wasserverdunstung aus dem Boden. Oesterr. landw. Wochenbl. 1880, p. 151. 184 quickly, to be sure, but, by this means, save to a greater extent the water supply in the lower layers of the soil. The warming of field soil by insolation, its aération when winds blow over its surface and all such influences, remove the water from the upper layers of the soil to a greater extent than can be restored by capillary at- traction for water from the lower layers. If now, by breaking up the sur- face, the interstices between its particles become considerably enlarged, the capillarity is decreased and the water no longer rises into the larger in- terstices of the now crumbly soil. The more quickly the soil is broken into coarsely friable pieces by chopping, hoeing and removing the turf, the more the drying out of the lower layers, where the roots are found, is delayed. The opposite result is obtained by rolling the field land. In this case most of the spaces, where capillarity did not act, are rolled close together. Capillarity at once becomes active and the upper surface remains moist for a longer time. Under certain circumstances, however, rolling may also be recommended as a means of retaining moisture in the soil. This will be expressly suitable for all very porous soils with a scanty water capacity and an abundant subsoil moisture, since, by hardening the surface, its evaporation is reduced, while the conducting of water from below is increased. In heavy soils, with a high saturation capacity, rolling would naturally be di- rectly injurious. MULCHING OF THE SOIL. Instead of breaking up the soil, its surface may be covered with a more porous material. In this connection advantageous results can be obtained even, by covering the surface with sand. This changes favorably the con- ditions of moisture and of warmth at the same time, for, according to Wollny’s investigations’, the temperature of the soil is considerably re- duced by breaking it up, since the conducting of heat in the friable layer is decreased by the considerable amounts of enclosed air. In the same way soil provided with a sandy covering is colder in the warm seasons than un- covered soil, because the light color of the surface decreases the absorption of the heat rays, and the considerable amount of water held back under the sand is warmed with greater difficulty. If the upper surface of the soil itself dries up, its temperature must increase because the evaporation which uses up heat is at once prevented. Breaking up the soil and covering it, therefore, modify the extremes of temperature, but are also valuable in still another way. According to Wollny (loc. cit. p. 337), it is shown that during the warm seasons con- siderably more water from the same amount of precipitation can filter through the soil when covered with sand than through uncovered soil. This takes place because the soil covered with a layer of sand (even if only one 1 Wollny in Oesterr. landw. Wochenbl. 1880. p. 214.- Nessler, Bad. Landw. Corres- pondenzblatt 1860, p. 230.- Wagner, P., Versuche tiber das Austrocknen des Bodens bei verschiedenen Dichtigkeitsverhiltnissen der Ackerkrume. Bericht der Ver- suchsstation Darmstadt 1874, pp. 87 ff.- v. Klenze, Landw. Jahrb. 1877. 2 Hinfluss der Abtrocknung des Bodens auf dessen Temperatur-und Feuch- tigkeitsverhiltnisse. Forschungen a. d. Geb. d. Agrikulturphysik, 1880, p. 343. 185 centimetre thick) remains richer in water, i.e. becomes saturated more quickly and therefore lets more water flow into the deeper layers of the sub- soil. The same result is shown by covering with ochre, such materials as stable manure, straw, tan bark, and even with stones. Soil covered with growing plants is even less pervious than the naked earth. Some practical workers recommend the use of peaty earth on sandy sous.. Thus Walz' made use of the upper layers of a peaty deposit which were 6 to 8 cm. deep and useless for fuel, in order to cover a field of poor sandy soil 2 cm. deep, in February. Later this surface which had been covered with peat and one adjoining it, but not so covered, were richly fertilized with stable manure. In the heat and drought of summer, maize planted on the field mulched with peat showed a better growth and furnished a higher percentage of yield. In the same way, later crops were found to be more luxuriant on the plat of ground mulched with peat. The value of the peat, which Nerlinger? has demonstrated in exact har- vest results, arises from its ability to soak up and retain the fertilizing substances which otherwise, in sandy soil, would be washed away. I have determined experimentally* that fertilizing makes it possible for the plants to give a better yield with less water, which explains the more favorable be- havior in time of drought. So1Its W1TH A PLANT COVER. It has already been said that soils with a cover of living plants allow the least water to drain through. This is explained by the fact that plant roots absorb the water. Comparative experiments* prove that the water in the soil is more quickly exhausted with a thick stand of plants, even if this exhaustion does not increase proportionately to the density of the plant growth. From these results, the difference between a bare, broken soil and one covered with a dense turf during hot, continued dry weather, can be ascer- tained. Therefore, in nurseries on porous soil, it is by no means a matter of indifference whether it is often hoed or whether turf and weeds are al- lowed to form a dense covering. It is not a theoretical conclusion but an often demonstrated fact that occasionally premature ripening and sterility are produced in fruit trees, because the weeds and turf have taken up the scanty supply of water. In forestry and trees in beds, if the seedlings do not make a dense growth, their development is threatened. Gravelly soils without sufficient humus content are also a menace for older plants from 10 to 15 years of age, especially if protection is not given on any side by larger plantations. 1 Zeitschrift d. landw. Ver. in Bayern 1882; cit. in Biedermann’s Centralbl. 18838, p. 136. 2 Fiihling’s landw. Zeit. 1878, Part 8. 3 Sorauer, Nachtrag zu den Studien iiber Verdunstung. Forsch. auf d. Geb. d. Agrikulturphysik, Vol. VI, Parts 1 and 2. 4 Wollny, Der Einfluss der Pflanzendecke und Beschattung auf die physikalis- chen Higenschaften und die Fruchtbarkeit des Bodens. Berlin, Parey, 1877, p. 128. 186 The forester considers turfed land as a favoring factor, since it retains the water of precipitation and by the quick evaporation withdraws the water of the subsoil. Places almost circular are sometimes found in forests about the base of the trunks where no second growth lives. This circumstance is ascribed to the reflection of the sun’s rays from the smooth barked, branch- less trunks (beeches, birches, firs). The sun rays flashed from the mirror- like bark dry the soil to a great extent. This condition can be overcome by various means, among which growing plants by natural seeding is recom- mended, since the plants so produced will adapt themselves to the locality. In places, which must be planted, material should be used which has been transplanted once in the nursery and, after the plants are set out, the soil should be shaded most carefully. Besides this, all conditions should be con- sidered which in general may be recommended for overcoming the lack of moisture, such as the protection of seed beds by walls, fences, rows of trees, or by closely set brush, hilling and especially breaking up the soil, or even fertilizing, since this means a saving of water. Sprinkling with water is advisable only in the most extreme cases of necessity. In brushing the edges of the beds the use of conifers, especially the Weymouth Pine, is most to be recommended, for spruce brush sheds its needles too quickly and makes a warmer cover. Fir may easily be set too densely and the leaves on branches of deciduous trees wilt too quickly, hence they do not afford shade to the soil which dries out too rapidly. Wollny has shown by experiments that seed and turf burn out if sown too thick, while vegetation on the same plot of land remains uninjured if the growth is more broken. He found that when the seed had been sown with a drill the soil be- tween the rows lost less water than that in the rows themselves and the further the plants stood from one another, the more water was retained in the rows as well as between them. Therefore, the proper adjustment of the quantity of seed to be sown on soils poor in water, will also assist in correct- ing injury due to drought’. Only in very definite cases can an overplanted soil be proved more ad- vantageous than bare soil. By an open growth of short-lived plants as a cover crop, water can be retained on sandy soils for later seeds. If seeding of the quick growing plants takes place in the autumn or early spring, the time these plants most need water will come during the autumnal or spring wet season, so that when the dry season comes, they are ready to set fruit and require relatively little water ;—rather, by shading the soil and by the forming of dew, they retain for the more superficial layers a pretty even moisture in which seeds sown later, and also delicate seedlings, can be developed which otherwise would have dried up on bare soil. Forest LITTER. It should not be forgotten that any covering of the soil retards the aération of the land and therefore, for the maintenance of fertility, the 1 Oesterr. landw. Wochenblatt. 1880, p. 233. 187 supply of carbon dioxid in the soil must be depended upon to disintegrate and dissolve the fragments of rock; hence great care must be used in the choice of the soil covering. How much the mulching disturbs the circu- lation of the air is shown by Ammon’s experiments’. \Vith 40 mm. of water pressure in an hour there passed through a layer of earth 19.6 sq. cm. in cross-section and 0.5 m. deep, the following amounts of air :— With a Grass Covering. Straw Covering. Uncovered. 12607 1. Gs0 ripe Mal In better aérated soils more carbon dioxid will also be produced and this, in spite of its increased elimination into the air, will make itself felt 10 an increased amount in the soil. The result of letting the soil lie fallow con- sists directly in the greater production of carbon dioxid due to the action of micro-organisms and to the greater decomposition of the rock debris. Another disadvantage of mulching is the lessened availability of the precipitation for such covered soil. The amount of this disadvantage will vary according to the kind of covering. It will increase with the increased sponge-like substance of the covering. Riegler’s” statement may serve as an example of this diversity. He tested various forest litter and peat moss (Sphagnum) as to permeability. Of the 500 g. of water, sprinkled daily in a fine stream on the air-dry litter, the following amounts were absorbed or ran throught :— Beech Litter Hemlock Litter Sphagnum Turf Ran through-absorbed. Ran through-absorbed. Ran through-absorbed. Ist day... 400.3 99.7 441.3 58.7 210.0 284.0 g. 8th day.. .487.6 12.4 499.6 0.4 493.5 6:56. This sprinkling corresponded to 10 mm. of rain and accordingly possi- bly 20 per cent. of the falling water was retained by beech litter, 12 per cent. by fir and 57 per cent. by moss. The mulch was 8 cm. deep all over. From Riegler’s other tables it is found that, in the next 3 or 4 days, still greater amounts were absorbed daily, gradually up to the 9th day the litter became so saturated with moisture that almost all the water which fell upon it ran off. Ten mm. of rain setting in after hot, continued dry weather, wet the earth under the beech mulch only to a depth of 8 mm.; under the fir mulch, 8.8 mm.; and under the moss, 4.3 mm. Besides this, the conditions vary according to the strength with which the water falls on the mulch. If the water, finely distributed, was sprayed on the moss cushion, 70 per cent. of the given moisture was soaked up, while of the same amount of water, supplied in the form of a fine running stream, only 14 per cent. was retained. FORESTS. The proximity of larger tracts of trees, viz., forests, must be considered as a means of saving the moisture in the soil of cultivated land. According 1 Biedermann’s Centralbl. 1880. p. 405. 2 Forsch. auf. d. Geb. d. Agrikulturphysik, 1880, pp. 80-96. 188 to Matthieu’s' observations, extending over I1 years, the air in forests, 1.5 m. above the soil, is on an average colder than above bare ground, the difference being the greatest in summer. The forests exert the same de- pressing influence on the mean air temperature as they do on the temperature extremes, which are less in forests. When the temperature differences amount perhaps to only 0.5°C., they are perceptible when a rain cloud passes over the region. Air will become saturated above the forest sooner than above uncovered land. Thereby the rain will begin sooner and be more abundant than on the land which is not forested. In fact measurements of Matthieu and Fautrat? prove greater amounts of rain above forests. Hygro- metric determinations have shown that the weight of water vapor in one cubic meter of air above a spruce forest amounted, on an average, to 8.66 g., while above forests of deciduous trees it amounted to 8.46 g.; above un- covered soil at the same height (104 to 122 m. high), at a horizontal distance of 100 m. from the conifer forest, to 7.39 g.; at the same horizontal distance from the deciduous trees, to 8.04 g. Thus the proximity of the forest in- fluences the moisture vertically and may also exert the same influence horizontally. FaLLtow Lanp. “Fallow Land” has less effect on the retention or increase of the water supply in the soil than on the accumulation of nutritive substances. Accord- ing to Wollny’s’ statements, the peculiarities of fallow land may be sum- marized as follows :—Soil lying fallow is warmer in summer and colder in winter. Fluctuations of temperature are greater everywhere in fallow land than in soil overgrown with plants. During the time of growth the soil covered by plants has always a lesser water content than when lying fallow. This greater moisture content is retained in bare soil even when worked more frequently. Bare soil also gains more from atmospheric precipitation since, during the time of growth, considerably larger amounts of water per- colate through soil lying fallow, than in fields provided with a growing plant covering. From the standpoint of nutrition the carbon dioxid con- tent of fallow land is most noteworthy. Wollny’s researches show that the air in fallow soil contains approximately 4 times as much carbon dioxid as in grass land. Therefore, the means for the solution of mineral elements in the soil are present much more abundantly; which explains in part the greater accumulation of nutritive substances in fallow land. This greater enrich- ment also depends partially on the quicker decomposition of the organic substances because of the greater temperature fluctuations, the increased moisture and the more vigorous activity of the micro-organisms. It should, however, be pointed out finally that soils with less power for holding water and in greater depths (sandy soils) with their greater permeability lose 1 Matthieu, Météorologie comparée agricole et forestiére. Paris 1878; cit. in Forschungen auf d. Geb. d. Agrikulturphysik 1879, pp. 422-429. 2 Fautrat. Ueber den Hinfluss der Wilder, den sie beriihrenden Regenfall und die Anziehung der Wasserdimpfe durch die Fichten. Aus Compt. rend. 1879, Vol. 89, No. 24; cit. Biedermann’s Centralbl. f. Agrikulturchemie. 1880, p. 241. 8 Wollny, Die Wirkung der Brache. Allgem. Hopfenzeitung 1879, Nos. 55, 56. 189 considerable part of the plant nutritive substances which are washed away into the subsoil. Such soils therefore, conversely, must be kept under a covering of plants. Local conditions must show which one of these means can best be used to prevent a lack of moisture. In any case it is evident that we do not stand powerless in the face of drought. b. Loamy SoILs. GENERAL CHARACTERISTICS. In considering physical influences injurious to vegetation, we need not distinguish between loam and clay soils. We are concerned always with mixtures of clay and sand and only the proportions of these two elements differ. The sand content decreases more and more from sandy or “mild” loam to strictly loamy soil and to clay soils, which are plastic in a damp con- dition; in them predominate the fine particles so easily washed away. In our agricultural land, mixtures of lime and humus will also be of importance as modifiers. Lime will make heavy soils more open by increasing their friability. Fertility is directly dependent upon friability, hence plastic clays are sterile. Non-friable clay soils are impervious to water, and, in level places, easily give rise to the formation of swamps. The smaller the size of the soil particles, the greater will be their water absorptive power so that very significant changes in volume occur with extensive, rapidly successive differ- ences in the supply of water. Upon this depends the characteristic cracking of clayey soils when drying out. Soluble salts can be washed out of clay soils only with difficulty. This drying out is much more dangerous as the soil approaches pure clay. When once dry, clay takes water up again very slowly since it can penetrate only with difficulty between the closely packed soil particles. These peculiarities decrease proportionately as the admixture of sand in- creases. Drying out in summer becomes at times more dangerous in heavy soils than in sandy, especially if a vigorous growth of trees has developed in regions which at best are poor in precipitation. The summer rains do not then suffice to make good the loss of water. These soils are dependent on the winter moisture. Hence the plant growth suffers here much more in dry springs, in years when the winter moisture has been less and the snow covering has failed, than on sand. This explains the fact that, after hot, dry summers and winters, poor in precipitation, a blighting of the tops of old trees (i.e., a drying of the branches) sets in because of the lack of moisture, even if the spring has abundant rain. Sandy soils with moderate spring rains are saturated more quickly and the water is at the disposal of the roots. Heavy soils remain “cold.” This is explained by their high water con- tent which increases with the fine granular structure. In many regions im- ported conifers (Abies Pinsapo, Biota orientalis aurea, Taxus hibernica, 190 Picea orientalis) die quickly. This is ascribed to winter frost but upon closer observation it is discovered that low temperatures become harmful only when the soil is very wet’. A deficiency of soil aération is the most harmful factor since upon the aération depend the phenomena of decay in the decomposition of organic masses. Thus in judging loamy soils as to their fertility not only the de- gree of friability, but also the depth to which this extends, becomes decisive. Since the firm loam layers of the subsoil are aerated only with difficulty, the spreading out of the root system takes place only in the friable layers. Therefore a special value should be laid on the maintenance of this friabil- ity. This must be taken especially into consideration in forests, where the litter is constantly raked away. Ramann’s investigations? show that, in re- moving litter, the soil becomes densely packed and works harm to the forest tract. The packing of soil and the necessity for loosening it should especially be considered in growing all tropical plants, as Vosseler® has proved. He describes the soils characterized by Koerts as “older red loam,” and especially the primeval forest soil of East Usambara thus ;—‘‘The red soil consists mainly of fine loam and clay which is pervious but too finely porous to take up small humus particles; besides, chemical action takes place possibly in the upper surfaces alone and thus prevents their penetration into the lower soil. Since the soil itself is the final pro- duct of decomposition, it lacks the advantage of processes of loosening up which possibly take place during such action.” Here also, therefore, the loosening of the soil is given as the first requirement for successful culti- vation. The more clayey the soil is, the more slowly the vegetable refuse will be decomposed because of the lower temperature. While in sufficiently friable soils, a normal decomposition takes place, masses of raw humus collect on thick clay soils, i.e., particles of plants, which are only slightly decomposable, remain deposited on the soil because the conditions are un- favorable for decomposition. If very fine grained soils with a greater moisture holding capacity, i.e., ability to retain large amounts of water without giving it off in the form of drops, acquire so much water that it overcomes the continuity of the substance particles by penetrating between them, thus forcing them apart, the soil becomes softer. This condition is especially peculiar to strong clay and red soil; such a disintegration occurs less frequently in loamy soil. Such reduction of the soil is doubly dangerous, if it takes place in the autumn or spring. On the one hand, the soil washes away at once and the seeds are soon exposed to drying or to freezing as the case may be. On the 1 Cordes, W., Beitrag zum Verhalten der Coniferen gegen Witterungseinfitisse. Hamburg 1297. 2 Ramann, E., Untersuchung streuberechter Biden. Sond. Z. f. Forst- u. Jagd- wesen, XXX Jahrg; cit. Bot. Jahresb. 1900, II, p. 415. ° Vosseler, Ueber einige Higentiimlichkeiten der Urwaldbé6den Ostusambaras. Mitteil. a, d. Biol. Landwirtsch, Institut Amani, 1904, No. 33, 191 other hand, this condition also retards working the soil and planting the fields, thus becoming a cause of poor harvests. Especial consideration should be given to the fact that, for all our cultivated plants, the usual planting time has been determined by observing the behavior of the plants in our climate. It can be shown at any time that variation in the periods of cultivation pro- duces changes in the character of the plants (the change from winter to summer grain). Such a delay of the seeding time often acts injuriously, as, for example, in peas. The same seed that furnishes a fine crop of healthy plants, when sown early in spring, very often produces low plants with small pods, greatly injured by mildew, if sown in summer. Kohlrabi, planted too late in spring, easily become woody, etc. Similar phenomena may be observed in fine sandy heath soils (loose loam). Grabner' characterizes this form of soil as consisting of sand grains almost as fine as flour with only small clay admixtures. The whole mass when wet looks like loam. In a dry condition, however, it may be dis- tinguished from loam proper by its porosity. Thus, as a result of its very fine granular structure, it can become as hard as stone. In places which are cultivated constantly and kept loose by means of animal manure, such soil is often valuable but in forestry it is not, for, after the usual single loosening, the fine sand is at once packed together by rain and too little oxygen from the air can get to the roots of the trees. THE COVERING OF SOIL WITH SILT. In heavy rain storms and floods soils with a large content of very finely broken particles are washed together and, after the evaporation of the water, are left in the form of a thick, close crust. The moisture holding capacity of a soil increases with the fineness of its pulverization, as has been men- tioned above. Increased pulverization of the particles deepens the upper surface and the power for retaining water depends on surface attraction. By pulverizing a soil mass, consisting of coarse pieces of quartz from 1 to 27 mm. in size, which had an absolute saturation capacity of 7 per cent., the capillary absorptive power was so increased that a fine sand produced from the quartz, the size of its grains being 0.3 mm., held back more than 6 times as much water. One sees that under certain circumstances the kind of mineral may be unimportant and only the mechanical constitution of value; that, therefore, even quartz dust can assume the réle of clay. Naturally this dustlike sand has no coherance whatever, and can therefore never in itself take over the rdle of a binding substance such as clay. Principally, however, it is clay soils which suffer from erosion in the form of silt and, by making air tight layers, cause the decay of seeds and plant roots. At times the roots form accessory organs in order to find the necessary air in marshy soils. In this connection, attention should be called to the knee-like outgrowths of roots which struggle to the upper surface of the soil, as those 1 Grabner, Handbuch der Heidekultur, 1904, p. 200. 192 of Taxodium distichum and of Pinus serotina which are not Hote on dry soils, and are described by Wilson’ as aérating organs. An example of the injury to vegetation, due to a direct deposition of silt, is furnished by Robinet? of Toulouse, where the nurseries had stood for only two days under water. At the base of some plants very little mud was deposited. These remained healthy. But when the mud covered the base of their trunks, possibly 10 to 12 cm. deep, the damage was great. Almond, acacia, cherry (even the mahaleb cherry) mountain ash, Ligustrum, Ma- honia, Evonymous and most conifers were killed. Individual specimens of Crataegus, Pirus Communis (of which those grafted on the quince suffer less) Pirus Malus, Castanea, Mespilus, Catalpa, etc., which had stood 8 to 10 days under water, blackened at the base and died when the silt was not removed. Platanus. Alnus, Ulmus did not suffer, and Populus, as well as Salix (weeping willow), developed many roots from the base of the trunk out into the silt. All the specimens of Sophora, Fraxinus, Carpinus, Fagus, Betula and Robinia did not die; the Jeaves of the survivors, however, turned yellow. The linden and chestnut lost all their leaves. Evergreen plants, and even a part of the conifers, lost their leaves when they had been covered by water. Of double importance is this change in the physical constitution of the soil in regions exposed to frequent inundations and, among them, the soils suffer most which are flooded by sea water. Aside from the injury to vege- tation from the large salt content of the. soil, there is found, according to A. Mayer’, as a resulting phenomenon of a dense covering, noticeable at times only in the second year, a formation of a black layer, strongly im- pregnated with iron sulfate, which may further injure vegetation. Von Gohren* also emphasizes the formation of such kinds of ferrugi- nous layers called “Knick” in West Friesland in very humus, loamy and clayey mud deposits of sea and river marshes and explains their production by the fact that the ferric oxid in the loam is reduced to ferrous oxid by the organic substances in the absence of air. This ferrous oxid combines with the crenate acid to form crenic ferrous oxid. Crenic ferrous oxid, distributed in every direction, is gradually oxidized again, cements together all parts of the soil as ferric hydroxid and co-operates in the formation of meadow ore of such ill-repute. We will finish considering the formation of meadow ore when discussing the peculiarities of swamp soil and now turn first to the phenomena of silt covering under the influence of salt solutions found in the use of fertilizing salts. Mayer’s experiments show that particles of clay suspended in water are precipitated differently when they are in suspension in pure water or in water containing sodium chlorid and other admixtures. In pure water 1 Wilson, W. P. The production of aérating organs on the roots of swamp and other plants; cit. Bot. Jahresber. 1889, I, p. 682. 2 Revue horticole; cit. Wiener Obst- u. Gartenzeitung 1876, p. 37. 3 Mayer, A., Ueber die Einwirkung von Salzl6sungen auf die Absetzungsver- haltnisse toniger Erden. (Forsch. auf dem Gebiete d. Agrik.- Physik. 1879, p. 251.) 4 von Gohren; Boden und Atmosphire. Leipzig 1877, p. 56. 193 the particles are deposited according to size (more exactly, according to the proportion of their surface to their mass). The finest particles remain un- commonly long in suspension since they are held by the attractive power of the water, which is almost comparable to a chemical solution. The at- traction of gravity for these particles is powerless in opposition to this attraction. After the clay, which has been dissolved in a glass cylinder for the experiment, precipitates from a salt solution, it is noticeable that a layer consisting of close, fine clay particles has formed with a comparatively very clear fluid above it. Because of the presence of sodium chlorid, all fine clay particles are precipitated more as a whole (coagulated, according to Schlosing). “Flocculency” is thus produced. The fall of the somewhat coarser particles among these appears to have been held batk, while that of finer ones has been somewhat hastened. It has been assumed that probably the presence of the salt has decreased the attraction between clay and water, since the water then lets the clay fall more completely. On the other hand the attraction of clay to clay must have been increased, and it is therefore more compact. Durham? explains the process by the fact that every bit of the attraction of the water otherwise required entirely for the suspension of the clay is satisfied by the salt of the solution. According to him, sulfuric acid acts like the solution of sodium chlorid, and, according to Mayer, all mineral acids behave in the same way. The same is true of mineral salts even in an excess of fixed alkali or ammonia. According to the theories now prevailing, electrolytes act flocculently, i.e. all bodies which in an aqueous solution are partially split up into “Tons.” Non-electrolytes have no action. At any rate, an electric current precipi- tates the flakes. It should therefore be assumed that the particles distributed in the water are charged with electricity and the cause of the oscillation may be sought in this electric charge’. The chief point, worth considering for all cultivated clay soils, lies in the fact that the nitrates, so far as deposition of the clay is concerned, ap- proximate the chlorates and, on account of the ease with which they are washed away, rapidly cause the packing of the soil. By this is explained the mechanical destruction of soils rich in clay, when repeatedly fertilized ex- clusively with nitrates. At first fine crops are obtained but later retrogres- sion takes place. Sodium chloride fertilizing used for certain plants has naturally the same destructive effect. Behrens? calls attention to the real disadvantage of an excessive use of fertilizing salts. Their osmotic action comes especially under consideration. Because of this osmotic action of the soluble salts in the soil, it 1s more difficult to supply the water needed by the plant and the plant responds by a suitable modification of its organs. In correspondence with the physiolog- ical lack of moisture, the plant reduces its evaporation by forming fleshier Biedermann’s Centralbl. 1883, Nov., p. 786. Chem. News; cit. “Naturforscher” 1878. p. 112. Ramann, E., Bodenkunde, 2nd. Ed., Berlin. J. Springer, 1905, p. 225. Behrens, J., Ueber Diingungsversuche. Jahresb. d. Vertreter d. angewandten Botanik, II Jahrg. Berlin, Gebr. Borntriger, 1905, p. 28, 1 2 3 4 194 leaves with smaller intercellular spaces; this may be found in plants near salt springs and on the sea shore. Among our cultivated plants, tobacco suffers most; it reacts exactly as in hot, dry summers and forms fleshier leaves with a reduced burning quality. Hunger' confers these observations, made in Europe, and says of the cultivation of the Dehli-tobacco on Sumatra, that the leaf most valued, most grown and most carefully selected, is large, thin, poor in oils, and develops only in the presence of abundant water as in continued rainy weather, while in dry weather small, thick, less valuable leaves, covered with many glandular hairs, are formed. THE IMPROVEMENT OF SoIts WHICH ARE BECOMING COMPACT. The improvement of the easily packed clay soils will have to lie in the increase of their ability to be worked. Heavy soils are unyielding, 1. e., they offer great difficulty by sticking to the farm implements, when damp, and by hardness, when dry. Great clods are produced which generally do not fall apart easily if the clay or red clay soil is poor in humus. It is well-known that the best plan for working soil for spring planting is to break it up in the fall and let it lie in rough furrows. The freezing of the water in the interstices during the winter months reduces the tough clods to a mellow crumbling mass. These advantages are available only for spring planting and disappear after the heavy rain storms of the summer. Therefore care must be taken to prevent caking by supplying humus or marshy earth; fertilizing with long strawy manure is very greatly used. However, liming and marling the soil have given very effective results. Practical experience has shown that the addition of calcium, which is in solution in the soil as the bi-carbonate, will hinder its caking. A definite amount of all salts, even of the most effective, calcium and magnesium, must be kept in solution in excess of the amount necessary to start action if any deposition of the clay particles is to take place. Even in rivers the flocculent action of dissolved salts makes itself felt since, for example, the sediment in rivers flowing from lime regions is more quickly deposited than in those from regions poor in lime?. For agriculture, fria- bility becomes directly important since upon this depends the proper state of tillage. The small bits of the soil behave similarly to the clay flakes. Hil- gard proved the action of lime by tempering solid clay soils with 1 per cent. quicklime. While the original clay soil became as hard as stone after drying, that mixed with lime was found to be crumbly and mellow. Since, besides a continuous mechanical working of the soil, the salts also condition its looseness, this must be the case, to an equal extent, in forest soil also. If the soluble salts, determining the friable structure, are decreased, as by excessive use of litter, covering with raw humus, the leaching of the upper layers, etc., a packing of the soil must take place. 1 Hunger, F. W. T., Untersuchungen und Betrachtungen iiber die Mosaikkrank- heit der Tabakpflanze. Zeitschr. f. Pflanzenkrankh, 1905, Part V. 2 Ramann loc, cit. p. 226. 195 A top dressing of waste lime from sugar factories is often made use of in the cultivation of beets. The mechanical effect makes itself felt not in- frequently by the fact that, as a result of increased capacity for being heated and the scanty supply of water, these soils later cause heart rot and dry rot. Hilgard’s statements! on the “alkali soils’ of California are of great interest. The alkali places often found between excellent cultural lands con- tain so much salt that they become noticeable by efflorescence on the surface. Those which contain alkaline carbonates (and partially also borates) are dis- tinguished by the difficulty or almost impossibility of producing a really friable soil. After each rain, a coffee brown, clay water, colored by dis- solved humus, stands at times for weeks on those places, recognizable be- cause of their lower position. The same working of the soil which gives good soil the consistency of loose ashes makes the alkaline land a mass of rounded clods varying in size from a pea to that of a billard ball. After evaporation, heating and saturation with carbon dioxid, the blackish brown solution, leached from alkaline soil, gives 0.251 per cent. in- combustible residue. Of this 0.158 per cent. was redissolved in water and this soluble part consisted of 52.74 per cent. sodium carbonate, 33.08 per cent. sodium chlorid, 13.26 per cent. sodium sulfate, 1.83 per cent. sodium triphosphate. The 0.093 per cent. insoluble residue from the heated water extract con- tained 14.02 per cent. calcium carbonate, 5.37 per cent. calcium triphosphate, 5.77 per cent. magnesium triphosphate, 24.37 per cent. silica soluble in Na,Co,, 50.47 per cent. of ferric oxid, aluminium oxid and some clay. In this case, as well as in many other alkaline soils in California, the ad- dition of a sufficient amount of gypsum (land plaster) produces a striking effect. The caustic action of the alkaline carbonates on seeds and plants stopped at once so that where previously only “alkali grass” (Brizopyrum) and Chenopodiaceae grew, maize and wheat were produced without difficulty. The gypsum naturally requires a longer time for the mechanical change of the soil surface and its greater loosening. INUNDATIONS. In opposition to the frequently widespread anxiety when volumes of water break over cultivated land, it might be emphasized that, naturally, aside from the washing away of nutritive substances and the mechanical injury due to the pressure of the waves, vegetation is not extremely sensi- tive to a water cover over the soil for some time. Woody plants especially, as floods show, possess a great power of resistance, which continues as long as the water keeps moving. Stagnant water, remaining for a long time on the surface of the soil, works the greater harm; for a shorter time, inundations in the form of 1 Hilgard, Ueber die Flockung kleiner Teilchen und die physikalischen und technischen Bezichungen dieser Erscheinung. American Journal of Sciences and Arts. XVII, March 1879. Forsch, auf d. Gebiete d. Agrikulturphysik, 1879, p. 441. 196 dammed up water may come under the head of useful factors of cultivation. At any rate inundation will always be more dangerous than those methods of irrigation where the soil always remains accessible to the air. The oxygen content of irrigation water increases oxidation in the meadow soils since water filtering off through the soil shows a lesser amount of oxygen and, at the same time, an increased amount of carbon dioxid and sulfuric acid in comparison with water in use for irrigation’. So long as sufficient oxygen is present the slow phenomena of oxidation of organic substances into carbon dioxid, ammonia and nitric acid, which we term decomposition, are accomplished chiefly by the action of micro-organisms. If a scarcity of oxygen occurs, however, due to continued retention of the water, that process of decomposition begins, partly of a purely chemical nature, partly with the co-operation of bacteria, which we call decay, whose final products are compounds which may still be oxidized. If the water accumulates in places where impervious layers of soil entirely prevent any vertical flowing away and all horizontal flowing away is also made difficult, the land becomes marshy. With the excessive wetting of the soil, the symptoms are again seen, which usually appear gradually with root decay. In deciduous trees, especially fruit trees, and with grapes a premature yellow leaf (chlorotic) condition becomes noticeable, which advances from below upward. This advancing death and falling of the leaves from the base of the branch to- ward its tip bear witness tu the fact that the growing branches strip off their older leaves in order to mature their younger ones, which happens also in a gradual drying up. By this means, yellow leaves may be distinguished from the pale leaves resulting from the action of frost, in which the young leaf apparatus is disturbed and its normal chlorophyll action retarded. CONVERSION OF LAND INTO SWAMPS. R. Hartig’s* observations show that stagnant water is most injurious in forest plantations since the sensitiveness of the trees to frost is increased and freezing and heaving occur in the seed beds. Hartig* observed decay of the roots to a devastating extent in the tracts of the young pines in Northern Germany. It begins between the 20th and 30th years when, after a short period of weak growth, the trees, still covered with perfectly green needles, topple over as soon as a weight of snow touches them or a high wind acts on them. It is found that the tap root (see Growth of Stilts, p. 92) is wet and rotted up to the base of the trunk while most of the lateral roots appear to be healthy. Such a decay of the roots may indeed be found in. spruce plantations, but it is less noticeable because the superficially extended 1 Wollny, E., Die Zersetzung der organischen Stoffe und die Humusbildungen. Heidelberg 1897, Carl Winter, p. 351. 2 Hartig, R., Lehrbuch der Pflanzenkrankheiten, 3rd. Ed. Berlin, Springer 1900, p. 263. 3 Die Wurzelfaule, Zersetzungserscheinungen des Holzes, Berlin, Jul, Springer, 1878, p. 75. 197 root system makes the tree less dependent on the few roots growing down deep into the soil. It may be observed, especially in the province of Brandenburg, that the healthy condition of pines ceases if the sand flats most suitable for this growth have depressions in the ground where the accumulated water forms marshy pools. Up to the edge of these marshy places the trees stand erect and are comparatively long needled. At the point where the black moor begins, the growth becomes weakened, the needles shorter and the tree shows very small annual rings which not infrequently cease entirely. In the increased planting of the very profitable pine trees, carrying them even on to damp soils, it is not surprising that root decay is found there to a very marked extent. It is advisable to limit the culture of pines to sandy, open positions and to choose for heavy, wet soils, such species of trees as are found by experience to best endure moisture. In places where no definite agricultural system regulates the tracts, the suitable kinds of trees make a natural appearance in the course of years, because of their greater power of resistance in the struggle for existence. It is approximately the same as the gtadual control of the position in frost holes by the kinds of trees which resist frost (hornbean, birch, aspen). The red alder can best endure the strain of stagnant water. Besides this, black and silver poplars, as well as most willows and the sweet birch, thrive on moist soils. The ash is often found also, but under these conditions the trunks are entirely covered with moss and canker-like swollen spots. In order to overcome the injury due to turning land into swamps, its cause must be determined exactly. At times the condition is due only to a lack of air circulation, and here the partial clearing of the land of its tree vegetation by the removal of the undergrowth and the lower branches of the trees, together with proper thinning, would be beneficial. Even when the land only becomes slightly swampy, especially in mountains, it may be re- stored by planting with conifers (Spruces). This holds good for the cases when increased evaporation of the upper surface is sufficient to overcome the accumulations of water in the soil. As the trees grow, and because of their close proximity, their evaporating surface not only increases but also less and less water can fall to the soil, because of the thick shelter of leaves. The very radical means of removing the water by drainage or ditches should be used in forest tracts only after careful consideration of all local conditions since this method is often attended by greater disadvantages than advantages. This is especially true in mountain forests where the lowering of the water level of one district may easily have wide spread effects on the surrounding region. In some cases, areas, especially slopes, with a strong tree growth, where there is no excess of water, become drier. Trees accus- tomed to the former amount of moisture deteriorate and may partially die. On plains such sharp changes due to drainage are less to be feared. It would not be necessary to further discuss the formation of marshes if, aside from the exhalation of gases, injuries to cultivated land did not 198 follow attempts to drain the marshes and boggy places. The injury to meadows should be considered especially in this connection on account of the frequent use of injurious marsh and boggy water for irrigation. The conversion of irrigated meadows into marshes by overfilling the soil with sewage may be considered only in passing. The statements of Bischof and Popoff' should be cited in connection with the exhalation of gases. The gases produced are often rich in hydro- carbons, especially methane or marsh gas (CH,). Popoff investigated the gas developed in a cylinder which contained a slimey mass consisting of kitchen refuse and substances of similar character. This slime was kept 3% weeks in the cylinder, at first at 17° C., later at 7 to 10°C., and gave gas mixtures of the following percentages of composition in the successive investigations which took place usually at intervals of 2 to 4 days :— i Eres (EO. ZAG (GHy 4.7 O; 81.06 N. ON 2. MLOZE, = 508.5 81.70 3: SaOo y= 29103) 2 O01, OF 35.98 N. ZS Bisa) tad ABS Wie olnae a neO5 tos Bi 1pQ007 4 4270 werk O10), 140 123031 Gi ASO s. BAcL. fhe GLO OO nay en Aamo eee 3 ONSEN 0:04." Ost ete These figures show that at the beginning of the experiment part of the air found in the cylinder was driven out, and part used up, while the oxy- gen oxidized the organic fragments in the slime. So long as free oxygen was present, the formation of carbon dioxid exceeded that of marsh gas,— on the other hand, this proportion was reversed as Soon as the oxygen was exhausted. Proceeding with the hypothesis that it is the cellulose in the slime which is decomposed, assisted by the action of the lower organisms, Popoff put clean filter paper with a small quantity of slime into a flask. On investi- gating the gas formed after some little time, he found its composition to be 34.07 per cent. carbon dioxid, 37.12 per cent. marsh gas, 1.06 per cent. hy- drogen and 27.75 per cent. nitrogen. Near marshes, however, we also frequently detect the odor of hydrogen sulfid. This comes partly from the decay of protein bodies which form leucin, tyrosin and other substances by their decomposition and finally car- bon dioxid, marsh gas, ammonia, etc. Erismann’s? observations, cited by Detmer, make possible the determination of the quantitative composition of the gas given off in 24 hours from 18 cubic m. of excrement placed in a poorly ventilated cess pool. The whole mass gave 11.144 kg. carbon dioxid, 2.040 kg. ammonia, 0.033 kg. hydrogen sulfid and 7.464 kg. marsh gas. In this decomposition oxygen and nitrogen were also set free. 13.85 kg. of oxygen are said to have been taken up by the 18 cubic m. in 24 hours. 1 Bischof’s Lehrbuch der chemischen und physikalischen Geolcgie, 2nd. Ed. Popoff in Pfliiger’s Archiv f. Physiologie, Vol. X., p. 113. 2 Zeitschr. f. Biologie, Vol. XI, pp. 233 ff. 199 Thus a comparatively very slight development of H,S is found and it must be assumed therefore that, if large amounts of H,S are formed in marshes and other places, they must owe their origin to a reduction of sul- fates in the soil, conditioned by the organic substances present. Pagel! and Oswald summarized the results of their investigations on such reduction processes in the substances of marshes and found that, in the absence of air, sulfur metals occur, as well as hydrogen sulfid, and that, together with this reduction of the sulfates, ammonia is set free from the marsh substances containing nitrogen. The authors do not state defi- nitely whether these substances are produced only in the absence of air, but in their production may lie the harmful quality of stagnant water. Tue BuRNING OF PLANTS IN MotstT SOI. In summers, remarkable because of great temperature extremes, it has been observed that on hot, clear windy days, plants of rapidly growing, large leaved crops, such as hops, wilt greatly, particularly when grown in damp places. The lower and middle leaves of plants growing in damp hollows are sometimes seen to turn yellow and brown at the edges and partially to dry up so that they can be rubbed to a powder in the hand. These specimens have been partly burned by the sun. The noticeable feature is that the burning takes place directly on those places in the field, in which, through- out the whole year, sufficient moisture is present, while in higher, drier portions, still more exposed to the wind, the plants usually suffer less. My comparative experiments” throw sufficient light on such cases. They prove that plants, which from the beginning produce their roots in a soil contain- ing much water or even in water cultures, evaporate much more water per square centimetre than do plants of the same strain grown under conditions exactly similar except with a lesser water supply. It is an interesting but not very well-known phenomenon that many of our cultivated plants from very different families grown under optimum conditions, in producing one gram of mature, dry substances, evaporate approximately equal quantities of water,,—indeed the transpired water varies from 300 to 400 g. in amount. If the plants grow in localities which, like soils with an impervious subsoil, constantly have a great deal of water at their disposal, a constant nutrient solution will be present in the interstices of the soil, more or less highly con- centrated according to the soluble materials present. If the concentration exceeds the amount favorable for the plant species, the plant grows less vigorously, remains short-limbed, small-leaved, but usually dark green. If the concentration is exactly right, the growth is very rich and luxuriant and the absolute water requirement is very great, but is small if reckoned per gram of dry material produced. Under such conditions the plant finds the soil water of great value. In excessively damp places, however, it often happens that the soil solution is poor in different nutritive substances. 1 Landwirtsch. Jahrb., Vol. VI, Supplement, p. 351. 2 Sorauer, Studien iiber Verdunstung. Forschungen auf dem Gebiete der Agrikulturphysik, Vol. III, Parts 4 and 5, pp. 48 ff. 200 The weather requirement is greatest under such conditions just as if the plant made the greatest struggle to produce as much as possible from the very scarce nutrient substances present. The leaves, then formed, are very large and well spread, but are very little resistent to cold as well as to heat. They react unfavorably to influences which pass over other plants without leaving any ill effect. Such disturbances occur earlier in plants in moist localities. On hot and especially windy days, evaporation is enormously increased, the amount of water transpired is then considerably greater than that supplied by the axial organs. Consequently the leaves on many plants wilt. The smaller the normal transpiration per square centimeter surface, the longer the amount of water brought by the stem, even on extremely hot days, will compensate for the loss of transpiration. The plants of damp localities which, as ex- perimentally determined, evaporate much more water in the same unit of time than do plants from dry places, have thereby first of all reached the limit when lack of moisture in the cell acts injuriously. In these plants the leaves dry up first and not the very youngest nor the very oldest but, as a rule, those working most actively and in part still elongating.. Proper drainage to remove the water from those particular tracts of ground is the surest method of overcoming the trouble. DELAYED SEEDING. As a result of damp soil the time for planting is frequently delayed. The following are the results of experiments by Fr. Haberlandtt and H. Thiel?. The most detailed experiments were made by Haberlandt in 1876 with four kinds of summer grain in which, on the 1st and 15th of the months April, May and June, the seed was sown on a bed 3 sq. m. in size. The results may be summarized as follows: The amount of harvest in all sum- mer grains decreased more and more as the seeding was delayed. This was based first of all on the considerably weaker growth of the grain planted late and was most evident in the smaller number of fertile stems. A de- crease not only in the quantity, but also in the quality was very noticeable. The weight in straw increased with delayed sowing. In general the chaff and roots of the crop increased disproportionately to the weight of the grain. The quality of the grain itself also decreased greatly. Barley and oats from later sowings had a greater amount of chaff by weight; the smaller the in- dividual grains were, the greater this disproportion became. The later sowings were attacked to a greater extent by ergot, mildew, rust and especially by leaf lice. Besides this, up to the time of forming the blades, as well as blossoming and ripening, they required a greater amount of heat than did earlier sowings. Even the germinative power of the har- vested grain was affected and of a lowered quality in seed from plants of 1 Haberlandt, Fr., Die Beziehungen zwischen dem Zeitpunkt der Aussaat und der Ernte beim Sommergetreide. Oesterr. landw. Wochenbl. 1876, No. 3; 1877, No. 2. 2 Thiel, H., Ueber den Hinfluss der Zeit der Aussaat auf die Entwicklung des Getreides. Ref. in Biederm. Centralbl. f. Agrikulturchemie, 1873, p. 47. 205 late sowings. In the first place, the percentage of germination was lower: in the second place, the grain from late sown and late harvested seed also required a longer time for germination. From Haberlandt’s earlier investi- gations in this line, showing a lesser development of grain in bulk as well as in absolute and specific weight, it is further seen that the amount of soil moisture alone is not the only cause of the difference between late and early sowing. In these experiments the plants had a sufficient water supply, from the beginning, and yet showed these different proportions. Thiel’s experiments with late sowings were made at various times in the autumn. The time of harvesting for all the plants, even of widely different periods of sowing, was approximately the same, but very late sown seed had a very small yield so far as it remained alive at all. Indeed Thiel rightly calls attention here to the fact that late sown seed sprouted simultaneously with that sown earlier with corresponding spring weather, without, however, having had time to collect sufficient material for an abundant development as did the plants grown from seed sown earlier. Naturally the constitution of the seed plays a considerable réle here. The older the seed, the more slowly the reserve substances are mobilized. With ripening and subsequent maturing, the amounts of sugar and amido nitrogen compounds decrease! and do not become prominent again until germination. The more or less favorable sprouting of the seed depends on its age and the soil constitution. At this point we will insert the warning that no reliance should be placed on the results of other germinative tests, but one’s own soil must be tested di- rectly as to its behavior with different seeds. Seed which keeps well, accord- ing to common germinating tests, may give poor results, especially in heavy soils and, conversely, a light soil may often help seed to make a good growth, which developed only a moderate quality in the germinating bed. Hiltner’s? report, for example, on newly harvested rye, which had suffered from a thunder storm, showed that it grew well in some fields, but absolutely would not grow in heavy soil. In another case, rye, developing 97 per cent. seed- lings in a germinating test, molded almost entirely on one field, while in an adjacent one it gave normal growth. SOURING OF SEED. In the section on too deep sowing (p. 106) we have already considered the disadvantages to which seed is often exposed in heavy or in incrusted soils with a large water content. Even germinated seed has to struggle against difficulties due to physical constitution of the soil; viz., from an excess of water in heavy soils. Here is found also souring of seed, which, to be sure, can occur also in light soils, but has been observed usually only in heavy, tough soils. The souring is due to a decay of the roots which have been longer in contact with standing water, charged with organic substances. Most roots 1 Johannsen, W., Studier over Planternes periodiske Livs yttringer, I; cit. Bot. Jahresb. 1897, I, p. 143. 2 Hiltner, L., in Prakt. Blatter f. Pflanzenbau u. Pflanzenchutz, 1903, Part I. 202 withstand very well a continued contact with running or standing water, which is free from organic substances, as can be seen in the different water cultures. Here, however, all living or dead vegetable particles in the culture vessels are avoided, for the decomposing organic substances take up all the oxygen which is present in a small supply. The roots of the growing plant must be killed because of a scarcity of oxygen and excess of carbon dioxid. Also, under ordinary conditions, seeds can survive contact with water, lasting for weeks, if the temperature is low. Thus Feige’ states that wheat which had stood for 5 weeks under cold water at 5°C. still lived. On the other hand, wheat kept 8 weeks under water, the temperature of which in- creased to 7°C. had disappeared without leaving a trace. Corn, which had previously been healthy, withstood water at 3°C. for 4 or 5 weeks, but was injured somewhat more than the wheat mentioned above. In the same way, alfalfa and clover withstood standing in water better than did corn. According to Kuhn, rye suffers especially from souring, while under the same conditions brome grass and others develop very luxuriantly. To this circumstance is due the erroneous belief, which even now occasionally appears, that rye can change into brome grass. According to our view, “Arrabbiaticcio” of wheat in Marengo and on the Roman Campagna be- longs under this head. Peglion® explains the disease as a general deteriora- tion of the plants due to being overrun by the luxuriant growth of weeds, which thrive better than the wheat on unsuitable soil. In Southern Italy the disease is called “‘calda fredda” and “‘secca molla.”’ The souring of the winter oil seeds, especially rape, is the most serious of all. From standing continually in water the roots decay from the tips backward so that in spring only the crown of the root and the leaf rosette remain. ‘These appear to be healthy as long as the moist spring weather prevents their drying out, yet, as the season becomes dry, the plants turn brown very soon and may be drawn from the soil by one leaf. An investigation by E. Freiberg and A. Mayer* serves to explain the fact that under continued wet conditions the character of the vegetation changes, so that phenomena appear like the above mentioned predominance of brome grass when rye had been sown. This experiment proved that the roots of marsh plants need much less oxygen than those of cultivated plants. This proves, as might have been supposed from the very beginning, that the individual plant species make different demands on the oxygen of the soil and, accordingly, must adjust their habitat to existing conditions. From the result of the experiments, however, another conclusion may be drawn which may serve in general when judging the demands made by different plants on soil; viz., the amount of air needed by their root systems. It is found that the more oxygen the plant needs for respiration, the greater is its nitrogen content. Marsh plants show a strikingly low nitrogen content and 1 From Oesterr. landw. Wochenbl. cit. in Biedermann’s Centralbl. 1877, p. 76. 2 Peglion, V., Sull’ arrabbiaticcio e calda freddo. Annuar. d. R. Stazione di Patol. veget. Roma. Vol. I, 1901, p. 37. 3 Freiberg, E, und Mayer, A., Ueber die Atmungsgr6fse bei Sumpf- und Wasser- pflanzen. Landwirtsch. Versuchsstationen 1879, p. 463. 203 have an open inner structure, permitting the storing of larger quantities of air within the body and suggesting the facilitation of internal respiration. Real water plants respire with a lesser intensity than land plants, as Bohm! found in his experiments, by measuring in a hydrogen atmosphere the car- bon dioxid given off during internal combustion. Since it may be assumed that the amount of respiration is determined by the amount of protein burned in the plant’s body, the oxygen needed by the root system will be greatest in cultivated plants, rich in nitrogen, and the most suitable soils will be those which most completely satisfy this need together with the other demands of the plant, i. e., rich field soil, which is loose or has been loosened. Those lands, therefore, which are repeatedly subjected to an oxygen scarcity, through the formation of crusts from rain action and the deposition of silt by floods, will have to be improved by corresponding changes in their physical structure. In the cases of souring, on the other hand, in which the air supply is not necessarily cut off by the physical constitution of the soil and in which only an excessive supply of water can fill the large interstices in the soil, we will have to turn to the removal of the water.. Here deep drainage or at least drainage canals 120 cm. deep, lowering the ground water level by this amount, are the most advisable precautionary regulations. The development of so deep a pervious layer is necessary because many Leguminoseae, like alfalfa, and sainfoin, with their deep growing main roots and fewer fibrous roots, are apt to die when they reach the ground water. SOURING OF PoTTED PLANTS. The souring of potted plants occurs chiefly when loamy or peaty soils are used. If the drainage hole of the flower pot is stopped up and excessive amounts of water given by some inexperienced laborer, the roots of the potted plants die completely, since they become brown and soft. The sour soil can be recognized at once by its characteristic odor. In this the process of decomposition of the abundantly present organic frag- ments, always contained in nutritive pot soils, takes place very differently. Probably acid compounds and also free acids are produced from the but imperfectly understood humus elements. If iron is present in the soil the uninjurious ferric salts can be reduced to the injurious ferrous ones, since, when the soil spaces are enlarged with water, a perceptible scarcity of oxygen must occur. The water is saturated with carbon dioxid from the secretions of the roots and also from the decomposition of the organic matters in the soil, and, with continued action, the carbon dioxid is sufficient to kill the plants. W. Wolf? proved experimentally that healthy plants, set in water contain- ing carbon dioxid, at once began to eliminate it in very greatly reduced quantities. The result is a wilting of the leaves which die later. 1 Boéhm, Ueber die Respiration von Wasserpflanzen, Sitzungsber d. Kais. Akad. d. Wiss. zu Wien. 1875, May Number. 2 Tagebl. d. Naturf. Vers. zu Leipzig 1872, p. 209. 204 Even if we cannot yet explain with certainty the mechanics of wilting which take place here (the explanation given by W. Wolf! does not seem to be sufficient) we will, however, scarcely go astray in assuming that, as the result of the excessive accumulation of carbon dioxid in the soil water, the normal elimination by the roots of carbon dioxid, which is con- siderable in vigorously growing plants, is at once arrested. An unusually high gas pressure must therefore be produced within the plant, increasing to a positive pressure in the ducts and reducing their ability to conduct water to the aérial parts. The-power of the ducts to conduct water will be decreased by the amount taken up by the negative pressure in the ducts. If thereby this conduction of water is weakened without corresponding re- duction of the use of water in the leaves, wilting results immediately. If the plants are placed in distilled water, as in Wolf’s experiments, a normal appearance and normal functions again set in. The distilled water in this case is like a sponge, absorbing the carbon dioxid and other excretory pro- ducts of the roots. Finally the result is the same for the root, whether the carbon dioxid appears dissolved in water, or as a gas resulting from an insufficient soil absorption. For the aérial parts of the plant, however, conditions are differ- ent and it is very important whether they come in contact with water rich in carbon dioxid or in air containing the gas. At least Bohm’s experiments?” on the leaves of green land plants have emphasized this. He immersed leaves of different land plants under water containing carbon dioxid and found that the plant no longer gave off oxygen if the part concerned was prevented from surrounding itself with an atmosphere containing carbon dioxid which would cut it off from direct contact with the water. The results of excessive watering in pots with the drainage stopped and the consequent cessation of plant and soil activity are best determined by a microscopic comparison with the soil in a pot containing a healthy growing plant. What intense activity is found in the soil! From the upper surface down to the bottom of the pot (in leaf and heath earth) are found fragments of leaves and stems, on which many kinds of the so-called mold forms with sterile mycelia, or with mature conidia, exercise their power of decomposition. According to the nature of the vegetable matter, Sepedon- ium (chrysospermum?), Verticillium ruberrimum, or Penicillium glaucum, Acremonium, Acrocylindrium, Cladosporium penicillioides, different kinds of Fusiarium and many others are found. On the upper surface often still other genera occur, especially the aérobic ones together with living diatoms and other forms of algae. The schizomycetes go deepest of all. Starch granules and bits of cytoplasm are found surrounded by. colonies of rod bacteria radially arranged; colonies of bacteria have often been established also on fragments of crystals. All this active life is engaged in reducing the plant substance and favors the processes requiring oxygen, which we 1 Jahresber. f. Agrik.-Chemie, 1870-72, II, p. 134. 2 Anzeigen der Wien. Akad. d. Wiss., 1872, Nos. 24-25, p. 163. 205 term decomposition. All this active life will either be stopped, by closing the soil interstices with water, or be turned to those destructive phenomena of decay, decomposition in the absence of oxygen. Every soil has its my- cological as well as its bacterial flora, which decomposes the organic sub- stances. According to Oudemans and Koning", these are approximately typical for definite kinds of soil. In potted plants it is safe to assume the beginning of stagnation when the upper surface of the soil is covered with a hard white or reddish colored lime crust, firmly attached to the edge of the pot. From the uncommonly large amount of carbon dioxid developed by the addition of acetic acid, it is evident that the incrustation of the uppermost soil layers in the pot, and at the edges, results especially from calcium carbonate. Magnesium carbonate is met with and also ferrous carbonate, which later through oxidation, produces as ferric hydrate different colors in the crust. According to the microscopic examination, the characteristic swallow-tailed crystals of gypsum and the octahedrons of calcium oxalate, as well as the rhombic forms of calcium phosphate, soluble in acetic acid, occur. The presence of the last named salt can not always be demonstrated and never in large amounts. On the other hand, calcium carbonate and probably magnesium carbonate, together with very fine particles of quartz sand, make up the usual substances of the crusts, between which is per- ceptible at first an abundant fungous growth with a formation of conidia on the humus. The production of these crusts may be explained by the fact that the water, given in large quantities in watering, becomes charged with the carbon dioxid, abundantly produced by the process of decomposition within the soil interstices. Hence water is a splendid medium for dissolving the calcium carbonate present in the soil, the magnesia, the ferric phosphate, the ferric silicate, etc. The more quickly the superfluous water is drawn away by good drain- age in the pot, the less will the minerals be dissolved and washed away. On the other hand, if the water stands in the pot and once becomes charged with calcium, which is soluble in the form of calcium bi-carbonate, it can only be removed by evaporation from the saturated upper surface of the pot and, when the pores of the pot are not closed by a green, slimy algal growth, this excessive water also evaporates slowly through its sides; it leaves behind the dissolved substances. The pots “become coated.” The calcium remains behind as calcium carbonate just as on the edge of a kettle in which water containing lime has been boiled. Thus the usefulness of the two processes, the frequent washing of the flower pots and the breaking up of the upper surface of the soil, is dem- onstrated. In the increasing desire to attain our ends by fertilization, different fertilizers are added to water soaked plants, but the main need,—sufficient 1 Oudemans, C. A. J., et Koning, C. J.. Prodrome d’une flore mycologique obtenue de la terre humeuse du Spanderswoud ete. Extr. Archiv. néerland.; cit, Z. f, Pflan- zenkr. 1903, p. 60. 206 aération of the soil,—is overlooked. The plants have not improved with this treatment. The best results are obtained by transplanting when growth starts and the application of heat to the roots to stimulate growth. Eichhorn’s' investigations prove that fertilizing may be injurious rather than advantageous with acid soil, in the presence of free humus acid. He states that earths, rich in humus, which contained free humus acid, liberate the acids from solutions of neutral salts. The acidification thus produced is stronger than it would be without these salts and, therefore, fertilization with neutral salts will increase the acid in such soils. This happens with calcium phosphate or any phosphate where the phosphoric acid, or calcium phosphate, passes over into solution. The addition of neutral potassium salts, especially alkaline sulfates, favors decomposition. If the humus acid is combined with a base, such acidification does not take place. The addition of manure, liquid manure, etc., will act only disadvantageously with such chemical decomposition and is to be avoided as are marly earths. INJUDICIOUS WATERING. The frequent dying of house plants makes necessary a reference to in- judicious watering. Excessive watering may be due to the fact that in- experienced people assume a lack of moisture in the soil as soon as the plant wilts. The fact that frequently, after watering, the plant becomes turgid during the course of the day gives weight to this assumption. If wilting follows this second turgidity, water is added until the plant is permanently wilted and the roots decay. Such conditions arise especially in the autumn when the more tender plants are put in conservatories with but little heat. The coldness of the soil then causes the wilting. We know froma number of cases cited by Sachs? that different plants require definite temperatures for their roats to keep them working, i.e., taking up water. Tobacco and pumpkins wilt in a soil at 3° to 5°C.; but if the same soil is warmed to 12° to 18°C., the root activity is re-established. In the examples cited above, when the previously watered, wilted plants become turgid during the day, this result is attributed to the influence of the watering. The real cause, however, was the diurnal rise in temperature of the air and of the soil, caused by the sun, whereby the roots were again stimulated to take up water. With the coming of night and the corresponding fall in temperature below the limit at which the roots are still to take up water, the wilting is repeated. The plant can therefore die of thirst even when the soil is very moist, if the soil be too cold. On the other hand, in moist air, the plants can remain alive a long time with wholly decayed roots, as is shown by water cultures. This is also the reason why, in root diseases, symptoms of dis- turbance are noticeable in the aérial organs only at a late stage. Another cause of the’ wilting becomes noticeable in midsummer. If plants transpiring rapidly are exposed for some time to the hot sun and to 1 Landwirtsch, Jahrbiicher 1877, p. 957. 2 Lehrbuch der Botanik, 1st. Ed., p. 559, 207 currents of air, they begin to wilt in spite of sufficient soil moisture, because the quantity of water evaporating through the leaves cannot be replaced quickly enough by the root. To be sure, the supply of water will be in- creased as the temperature rises simultaneously with the increased sunshine. According to De Vries", imbibition of the cell walls is increased and thereby their ability to conduct water, but the increased supply, nevertheless, cannot make good the loss through evaporation and the leaves must droop. If the pots are then watered, without having been tested, the earth will become sour. The same result is found in the so-called New Holland and Cape plants belonging to the families of the Epacrideae, Ericaceae, Papilionaceae, Rutaceae, etc. The loose, fine, sandy, but little decomposed earth, such as heath mould, cannot be pressed very firm into the pots, because the unde- composed pieces of roots and leaves form a very loose consistency ; with too heavy watering, however, the fine grains of sand and clay are first stirred up and then washed down so that only the long, loose fibrous elements re- main at the upper surface of the pot. These naturally retain but very little water and let it run down very quickly to the bottom of the pot. On this account the upper surface of the pot is always almost half dry. If now the gardener lets himself be led astray and waters the pots under such con- ditions, and if the pots have no good drainage, the very fine roots will decay. (It should be remarked in passing, that the so-called soured pots quite fre- quently show an alkaline reaction. I found with potted plants, whose roots had decayed, that moist red litmus paper turned blue as far as it lay upon the surface of the pot). As a means of overcoming this, transplanting into very sandy earth and sinking the soured plants in beds with warm soil has already been recom- mended. As a matter of course the roots must be cut back to the healthy part when transplanted. As a precautionary measure, the pots may be plunged into the ground and similar methods may be recommended. In doing this, how- ever, a stick or a piece of wood, turned like a cone, should be used to make a deep, funnel-like hole, whose upper edge is exactly the size of the edge of the pot. The pot then hangs in the hole. Below the pot the lower part of the conical hole forms a cavity and prevents the earth worms from crawling into the drainage hole in the pot and stopping it up. In flower pots stand- ing in a room, or on flower racks, the soil will not sour if only some little care is taken. The water content of the soil may be judged easily and com- paratively accurately by tapping the pot. If the earth is full of moisture, the water lies between the individual particles of soil and the sides of the pot and the sound resembles that of a dense mass ; when the amount of water is scanty, however, the pot rings hollow. According to the above, therefore, one should consider not only how much to water, but in what way potted plants should be watered. In order to avoid washing away the finest particles of clay and sand and thereby 1 Bot. Zeitung. 1872, p. 781. 208 forming crusts, or choking the drainage of the pot, the water should never be poured quickly through the spout of the watering pot. In plants set in pots and sunken, a hose should be used, or, in pots set on forms in con- servatories, a slender and long spout, giving only a gentle stream of water. One should avoid holding the stream of water at the base of the stem, which is often entirely white as a result of incrustations of lime. UseE oF SAUCERS UNDER Pots. In house plants the use of saucers under pots is general. This saucer is necessary for preserving cleanliness on the window sill and on the flower table, but is usually injurious for the plants themse!ves. No matter whether the pots be watered from above or by soaking up water from the saucers, the soil will almost always take up too much water. Many plant lovers con- sider this condition advantageous. The result, however, is a choking of the roots at the bottom of the flower pot. The decay of the roots continues gradually upward and finally shows itself in the dying of the edges of the leaves. If these symptoms appear, the plant is, as a rule, lost to the ama- teur, but the gardener can often cure it. For the amateur, who has no warm bed at his disposal, we would recommend setting the sick plant in pure sand and placing it in a warm, half shady place. THE RUNNING OUT OF POTATOES. In discussing the disadvantages of heavy soils, we should consider the point of view, repeatedly brought forward in practical circles, that our potatoes “run out,” i.e., gradually lose their good qualities and degenerate. Some people would explain this by holding that, in the customary method of propagation by planting tubers, one really propagates asexually, without interruption, an individual once produced from seed and that, thereby, an organism so long lived must at last show the weakened condition of old age. A proof of this is found in the retrogression in the starch content of our favorite older varieties as, for example, in the Daber potato. According to our point of view, the cause of the supposed running out lies in the lack of foresight of the agriculturalist in growing varieties on heavy soil which have been produced on light soil. We refer in this connection to Ehrenberg’s work' on the results of 15 years experiments at the “Deutsche Kartoffelkulturstation.” The average vield of all the varieties grown seemed to increase constantly from 1889 to 1903. In regard to:the “Daber” potato, the yields decreased only on heavy soil which is easily explained since in Daber a very light, dry, sandy soil predominates. If newly grown seed of this variety was planted in heavy close soil, it gave better results than the form which had been cultivated there for some time. The same new seed, however, planted in sandy soil, usually gave a poorer result when compared with the naturalized plant. We find 1 Mhrenberg, B., Der Abbau der Kartoffeln. Landw. Jahrb, Vol, XXXIII; cit. Centralbl, f. Agrikulturchemie, 1905, p. 235. PART III. MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Prof. Dr. G. Lindau And Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History of Berlin in Hamburg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIGC DISEASES © -BY PROF. DR. PAUL SORAUER BERLIN ‘WITH 208 ILLUSTRATIONS IN THE TEXT , ‘ { , . ‘ * a ne yi Ve . ‘ , nt ey | Copyrighted, 1915 By: FRANCES DORRANCE | . Ae ¢ ou — © a401187 THE RECORD PRESS Wilkes-Barré, Pa. MAY 29 1915 ign , ae i 209 proof in these experiments that newly introduced seed retains at first the char- acter developed in the place where it has been bred. If, for instance, heavy soil reduces the starch content, the reduction does not take place in the first year with new seed and therefore this seed contains more starch than the native seed. On sandy soil, however, a variety has been bred which contained the largest amount of starch possible under the conditions. The newly intro- duced varieties with the peculiarities brought with them, however, had not as yet adjusted themselves sufficiently to these conditions and therefore gave a lesser yield. Exhaustion or degeneration will therefore take place only where a variety does not find the cultural conditions it requires. The cir- cumstances may be similar in all phenomena of supposed exhaustion or degeneration. Our cultural varieties are the products of breeding under very definite conditions of position, soil and weather, and are kept pure only if they again find conditions similar to those where they are grown. [If it is desirable to make use of valuable peculiarities of any definite species in another locality, good results are obtained only by frequently renewing with seed from the native habitat or from habitats similarly situated. SENSITIVENESS OF THE SWEET CHERRY. The complaint in different places that the sweet cherry every year suf- fers increasing injury from frost, the exudation of gum, attacks of fungi etc. is often due to the failure to observe the fact that the cherry does not like a heavy soil. This circumstance has been especially emphasized recently by Ewert? and deserves to be repeatedly borne in mind by the fruit breeder. Naturally here also some cultural varieties are able to adapt themselves better to heavier soils, but in general the rule holds good that the sweet cherry likes a light, deep soil and flourishes especially well on alluvial sand and loose soils. The amount of nutrition in the soil is a far less decisive factor than its physical constitution, especially its granular condition. Often a scarcity of lime is given as the cause of poor growth,; which can be overcome by supplying lime. The improvement in growth, however, may not always be traced back to the nutritive action of the lime but to the change in the physical soil condition due to it, viz., greater friability and thereby increased aération. Ewert’s statements throw light on lime as a nutri- tive substance. He states that the sweet cherry flourishes even when the lime content'is from 0.04 to 0.15 per cent. Soil with possibly 80 per cent. of easily washed away particles is not suited to the growth of cherries even with 40 to 45 per cent. CaCO,, if this is chiefly present in so fine a condition that it also can be washed away. The cherry is peculiarly sensitive to stand- ing water and it grows best in dry soil in open places. THE Tan DISEASE. Trees standing on damp ground may show decreased growth, especially if their early growth was rapid. The older bark cracks or, after the outer- 1 Ewert, Das Gedeihen der Siifskirschen auf einigen in Oberschlesien haufigen Bodenarten. Landw. Jahrb. 1902, Vol. XXXI, p. 129. 210 most cork layers have fallen off, blister-like or flat, warty swellings put in an appearance and later these have a diseased wooly outer surface. If the place becomes somewhat dry, a reddish yellow to a brownish yellow powder may be brushed off which in color resembles fresh tan bark. This may have given rise to the term “Tan Disease.” In introducing the subject of this dis- ease into scientific discussion I have re- tained the name used by practical growers. The same process takes place also in roots and young branches. Young bran- ches with knotty tan pustules may be found in cherries. Up to the present this disease of the bark of the older trunk and roots has been observed most frequently in apples. Plums seldom suffer. Similar processes, resulting in the falling off of larger pieces of bark, have been found in elms and will be treated under growth disturbance due to marshy soils. In figure 23 is seen a piece from an apple root, natural size. Its bark has been broken open by cross-tears varying in size, the edges of which have been forced back; the open places are covered with an ochre powder or (when first taken from the soil) with soft, moist, brown masses. Figure 24 represents a cross-section through such a callus place. We find the wood (c is the cambial zone) of a practically normal structure traversed by the medullary rays (m), most of which show no variation whatever. Only in some (m’) it is notice- able that in the younger portions they be- gin to broaden, thereby causing a looser construction. This process of loosening, however, finds its evident expression only Fig. 23. Appleroot withrupturea in the bark where the rows of medullary tan spots, natural size. (Orig.) ray cells, beginning to separate from one another, form loops. While the younger inner bark, with its hard bast cords, still shows no change from a normal structure, the older layers (at left side of the illustration) display an impoverishment of the cell contents and some radial stretching (k’). This excessive elongation of the bark parenchyma becomes greater, the fur- ther toward the outside the cells lie, and it increases within the cork zone in such a way that the cells lying free on the outer surface take on a pouch- like form (s) and are only very loosely united with one another. ZAI If the outer surface of the root dries off, the cell pouches shrink and, in the outer layers, are entirely separated from one another. Then a tan- colored, powdery mass forms which may be wiped away with the finger. Even the lamellae of plate cork (¢) which are present at the edge in thick layers (of equal size. under normal conditions) and, gradually dying back from the outside, fall away at the place of the tan disease, are also drawn into the process of loosening. These split off because some of the middle layers round off their cells and show a tendency to assume the structure of cork as will be described more fully later under the cherry. uth. UG Ui 1 8 ad Non mec Jost (ta 3s) weer ae of, i. {) 4 Hi Hy Lr) 9 ry yy) (148 ++ i ona YE i yh fl op, x LH ge 0 y} 4) Wy i Dn Mp (] BHT PeHOPga 1 Bary DY nog TRA YY HP i) a) BOK ae } NCH INOS: . ‘ Sap UA en aaaltes yo aaa et SO "S799! [SJ 2a DESAY ene ee (Ss OY, PA PEG) oo gy) se a) SS SS 3 Suey a —= tel Be oF C) Se as ‘Za DS. aS ig) @ iS) rs S Fig. 24. Cross-section through a ae a in an apple root. (Tan disease.) rig. If the outgrowth of the bark at the edge of the tan canker and the emp- tying of the cell have reached maturity, the well-known hourglass arrange- ment of plate cork layers occurs (¢’) which cut off the hypertrophied bark parenchyma, finally becoming cork, and it becomes an eletnent of the bark scales. The cell elongation meantime advances laterally and further toward the inside. Thus at w we see the beginnings of this since the bark cells, normally elongated tangentially, are becoming square in cross-section and in- crease in number by division in order to round off more toward the diseased side, to become more open by enlargement of the intercellular spaces (17) and finally to pass over into the radial elongation which increases to pouch- 212 like outgrowths. By this advance of the process of over-elongation into constantly younger bark parenchyma layers, the activity of the root is finally exhausted at the place of the tan disease. The injury is not so intensive in the aérial axes Sometimes in larger trunks the phenomenon is not noticed until the bark is closely examined. It is then found that some bark scales stand out raggedly. If these are re- moved, which may be done very easily, it is observed that the outermost layers of the succulent bark tissue form irregular blister-like swellings which rupture later and decompose into dust-like masses which may be wiped away in dry weather. Figure 25 shows the fresh bark sur- face of an apple tree which has been laid bare by the removal of the outer bark scales. On this greenish brown, juicy surface hemispherical or elongated warty excrescences (a) appear very clearly. Figure 26 shows a cross-section through such a boil-like swelling in which, however, the wood, cambium and youngest inner bark have not been drawn. We recognize at the first glance the corres- pondence in structure with that of the tan spot of the root. At the lower part of the figure -6 we find the bark parenchyma with three hard bast bundles of a normal arrangement and position, but close above these hard bast bun- dles is noticeable a change in position since the tangentially elongated bark cells, rich in chlorophyll, begin to increase in length radially | (rv), to divide and to be arranged in parallel ‘a lines broken by large intercellular spaces (7). Fig. 25. Piece of the bark Lhe fact that this change in tissue must have from the trunk of an apple-’ taken place very eafly, at the time of pushias tree with the tan disease. a thecallusesof thetan disease, dfrag- OUt fom the cambium, 1s evident becausesmae fo gE Oye eae permanent tissue of the collenchyma (cl) has developed only one layer within the tissue of the excrescence. The chief part of the swelling has come from the peri- pheral layers which have developed into cushions (w) of elongated, finally pouched cells (s), which have raised the plate-cork cell layers and finally split them. SSS i: rd SEZ yg = SEZ, Ss = CH = ———F hel) In explaining this phenomenon we must not forget that these tan places arise underneath the old bark scales, and, with a formation of full cork, finally become bark scales by suberization. Thus we find that the organization of the bark into constricted and constricting cell layers, as they alternate in the bark, has taken place in the young bark tissue, for we find that, in young fresh bark tissue, cross bands of plate-like cells, varying in structure and the 253 constitution of their walls, transverse in curves (up) the hypertrophied tis- sue, which, at the beginning, contains starch. This formal and functional organization of the bark parenchyma which determines the formation of the bark may be found also in other tree barks, but first occurs, so far as I have observed, in the older axes in which the bark parenchyma has been influenced by the pressure of the bark ‘scales lying above it. On this account I have called these bands of tangential cells --74 ‘ . pM ES » [ROMP LL, ) . Ma Wipe oll AB Appaasis PED) 1 SS} iy 'Y) ee /? M FI — SS ==e =a eee CS ligjasy Tari me melee 6 \TH$ Ce Fig. 26. Spot on the trunk of an apple tree with the tan disease. Explanation of the letters in the text. (Orig.) (np) “Pressure bands,” which later suberize, often also developing plate cork cells and cutting off the bark scales. I have had opportunity to study the tan disease in young cherry branches in a wet summer on very vigorous young trees in a nursery. Figure 27 shows that on these cherry branches the outer bark had split or been torn open in broad, irregular stripes (e¢). An intense yellow ochre colored mass~ (f) could be recognized at the ruptured spot, which, when tapped vigorously, gave off a powdery dust. The whole impression given by these branches was as if they had been very thickly covered with rust fungus. 214 The first indication of the disease occurred in July, when, among nor- mally growing trunks, the leaves of some specimens turned yellow and fell off. Nevertheless the terminal buds of the branches developed a vigorous August growth which held most of its foliage until fall. In September the outer bark covering split and the surface appeared like yellow ochre velvet beginning at the lowest part of the branch and decreasing in in- tensity toward the tip. Further, the fact is worthy of notice that practically only the luxuriantly growing wild trees appeared to be diseased. The phenomena of the tan were only sparsely noticeable in grafted trees. It was seen at once that branches, where they had re- tained their leaves, had only a few really torn spots in the bark, indeed only closed, warty excrescences, i. e. the younger stages of the disease. In the axils of two year and much older diseased trees, ruptured places in the bark (7) occurred less fre- i} quently. Usually the individual iailk--* centres of disease appeared there in the form of very broad, very high yellow ochre cushions running crosswise. The investigation of these cus- hions and of the broad, ruptured, discolored surfaces on branches one year old showed at once marked correspondence with those on the older ones; only it could not be seen that the lenticel cushions give off any dust. The discolored mas- ses were found to be light brown, Fig. 27. One year old and two year cylindrical, wrinkled cork cells with old cherry branches with tan cushions , between the split bark stripes. (Orig.) | rounded corners, which were broken off individually or in small groups. The branches, giving off this dust, seem with a few exceptions to be otherwise healthy, only their primary bark is very much broken by the considerable separation of the parenchyma cells. Places with loosened structure are found in the wood as well as in the bark. Cross bands of duct- less parenchyma wood may be noticed in the stages produced toward the 27s . middle of summer. These are filled full of starch, while the normally constructed wood, excepting the medullary rays, has none. Within these cross bands the medullary rays are broadened and have gummy spots. The beginnings of the tan formation are found close under the terminal buds of the topmost branches, where the epidermis is still uninjured, but is already underlaid with cork, possibly five layers thick. In places, this pro- tective layer, consisting of comparatively thick walled cells, corresponding to plate-cork, shows a change even in its first stages, so that the cells lying directly beneath the epidermis have developed into parallel rows of cylindri- cal, radially elongated, brown-walled, full-cork cells. There is present here, therefore, the character of lenticel growth which Stahl’ has already de- scribed thoroughly for the cherry and which only differs from his descrip- tion in that here the full cork cushions are rarely produced under the stomata. It is seen that an extensive formation of full cork can take place in- dependently of the stomata in the development of a plate-cork layer, since several layers of lenticels are produced in which the cork formation ad- vances inward into the primary and, in fact, into the secondary bark. As the shoot of the current year becomes older, a second layer of plate- cork appears very normally, directly beneath the one first produced. It has | been found just as thick (viz., 5 to 7 cells) as the first whose cells gradually collapse with the apparently lessened swelling and the browning of the walls. During this process the normal cork covering of the cherry trunk appears to be differentiated into two layers. The upper, older one is very dense, since the cells usually have so collapsed that their cavities are recognizable only as fine lines; this layer passes over gradually into the second, later formed cork layer. In the latter, the plate-like cells are very uniform and their wide lumina are filled with a watery content or even with air. They border on a browned cell layer, with a clearly protoplasmic wall lining, which, as cork cambium, assumes the continued formation of the cork layer occurring in places. When treated with sulfuric acid, the composition of the oldest, sunken, collapsed brown cork layer is easily recognizable, since the cells are often distended and show in places their original height and width, at times almost square in cross-section, while the full cork cells are not changed. With this treatment the layer, produced later, rounds out its youngest cork. cells into hemispheres after the cork cambium has been destroyed. In the formation of the many layers of lenticels, the development of such elements is repeated in the secondary cork layer underneath the first centres of full cork. : The second case of lenticel formation, not connected with stomata, is illustrated in figure 28. This shows the cross-section of a new structure on 1 Stahl, Entwicklungsgeschichte und Anatomie der Lenticelle. Bot. Z. 1873, No. 36. 216 the barked cherry trunk. We must imagine that all the tissue here shown in the form of a callus covered with bark rests upon the old wood cylinder from which the bark has been removed. Since reference to the anatomical processes, leading to the formation of this new tissue on the exposed wood, is made in the chapter “Wounds” (bark wounds), we will mention here only the fact that, if at any given time the bark is removed from a tree, the newest cambium, thus exposed, begins to grow again and covers the wounded surface with a parenchymatous tissue layer. This parenchymatous covering is increased by the later appearance of a constant meristematic layer. The inner surface of this layer forms i ty Ht i re | y ii 1009" Hy y \ \ AN i \ eS Wiese NN ASs VARS We TL 2 eS 9 @, 8 — oy “gy yaa Oy \ fl oN {? \ s aps Z ROEes Wenae RS ay wire P SAAN . (Ee \\, FE eo ae \ xa eel \N \\ : cu rst NANNY ai i \\ \p ar, } )! ie amv is Ae sees Wi ORS SOUO oA SS PReae s elol ane y ee Wy Hh, ms a DAY Haan) My : De RN Un ea SOE a i ais ae () OVA ayy I] TER i wae pele? Wieay Us, Eee ay, hp Fig. 28. Newly formed wood and bark body on the bark wound of a cherry trunk. The bark shows a lenticel excrescence. (Orig.) normal cambium, which gives rise to woody tissues toward the centre and back towards the periphery. Figure 28 is a new structure several months old which, in the form of a broad wrinkled callus, has grown on the cambium of an experimentally barked sweet cherry trunk. The old wood of the barked trunk has been omitted in the drawing; it would join on at hp. The cambial zone (c) has sharply differentiated this tissue into wood and bark. The wood, where it rests on the old trunk, has a parenchymatous structure (Ap) ; which later passes over into a vascular new wood (nuh) forming libriform fibres. The structure of the bark is at first irregular and corresponds to the formation of wood which only gradually obtains its normal structure, for the hard 217 bast bodies begin in the form of individual, short elements (Ab) with wide lumina and only later grow out from the cambium as connected groups of elements (ib') elongated like fibres’. The bark of the new structure has formed a protective cork layer in its peripheral parenchymatous layers which has gradually grown very thick. At first only plate cork was formed; but later, in different places, full-cork masses (/k) developed instead of the plate cork cells, splitting the covering (k) composed of the latter cells and pressing the cork cambium inward (kk) by their increase which extends further and further backward. The full cork began to form when the whole peeled surface, for the purpose of further investigation, was enclosed in a glass cylinder, partly filled with water. While this lenticel out-growth, produced from the phello- gen, was only slightly noticeable in those parts of the bark which remained in the air, it had developed an unusual luxuriance below the surface of the water. The tan disease of the cherry is therefore an abnormal increase of the normal lenticel formation. So many and such extensive full-cork cushions are produced close to one another that they unite, pushing off the epidermis in large connected tatters and appearing as uniform velvety surfaces cover- ing a large part of the branch. The outermost layers of the full cork cush- ions are so loose that the connection between the peripheral cells is broken by a slight blow when the air is dry; this explains the discoloration and the dust flying from places affected with the tan disease, if the spots be touched or shaken vigorously. This scattering of the dust increases with the num- ber of full cork cells lying above one another and cushions composed of parallel rows of full cork, 20 cells deep, have been observed. In this case the process of elongation has included the entire thickness of the primary phelloderm so that the later formed, secondary full cork lies directly under- neath this, i.e., no separating plate cork layer is left between the different generations. The appearance of the tan disease will have to be traced to the super- abundance of water in the bark body. This local excess of water may be due, on the one hand, to supplying the roots abundantly with water, especially 1 Reference should be made in passing to the illustration of the beginnings of tuber gnarls not in any way whatever connected with the tan disease but shown in the drawing at B. They are produced by a local accumulation of plastic material as, for example, the isolated wood in the bark of the new structures formed near the wounds of various trees (cherry, apple, pear and pine). At the centre of such wood formations with a spherical wart-like structure may be recognized one or more hard bast cells. The case in which hard bast cells (especially diseased ones) are overgrown by tissue is of very frequent occurrence in injuries of very different origin. This over- growth consists usually only of a covering of plate-like cork cells several layers thick. In some cases, however, instead of the rapidly transformed cork cambium, a persistently active cambial layer is formed which deposits wood elements toward the inside and bark elements toward the outside. Such a case is represented in the wart-like tissue excrescence (B) at (u’) while at (u) in the left part of the figure (A) may be seen only a cork covering around one of the isolated hard bast cells first produced. The bark rays pass around these new structures on both sides as if around some foreign body. 218 those of vigorous individuals; on the other, by the lessened transpiration of the bark because of greater humidity. Such conditions in the cherry lead to lenticel excrescences as is proved by experimentally producing an accum- ulation of full cork in parts of the bark kept under water and further by observing specimens naturally diseased. In this way it was discovered that the cork excrescences preferred the youngest, well-leaved internodes in which the bark formed folds. Such folds were produced, for example, in places where the vascular bundles of the leaf left the axial cylinder and pushed out the bark when passing into the petioles. ; Some other observations have been made showing that the decreased evaporation due to increased moisture favors lenticel formation. Thus Stapft, in his studies on the potato, mentions that stomata develop into lenti- cels if transpiration is arrested. Further, Haberlandt? found that in the horizontal branches of different trees (the linden, elm, honey locust, etc.) the lenticels always occurred in greater numbers on the under side than on the upper side, although counting the stomata on both sides gave approxi- mately equal numbers. The under side of the branch, inclined toward the earth, will surely transpire less than the upper side, because of the greater proximity of the soil and the lesser supply of air. The tan cushions in plum trees are essentially similar to those observed in the cherry. As yet they have been observed only on old specimens with diseased roots. I have known of only the initial stages in apricots. In all varieties of stone fruits the cork excrescences were accompanied by marked processes of bark loosening which in part resulted in the shoving of the bast cords towards the outside. In young wood a weakly developed wood ring and a reduction of hard bast bundles to isolated wide bast cells, filled with a brownish-red gummy substance, was often noticed where the tan disease had not broken out. Traces of gummosis were present everywhere, and at times rich gum centres were found. In cherries, the especial sus- ceptibility of certain varieties to the tan disease may be recognized when different varieties are planted close to one another, as, for example, in the ’ “black ox heart” and in ‘““Winkler’s white ox heart.” All the cases which I have known originated on heavy soils or marshy meadows. The history of some cases showed that the diseased trees had been fertilized with stable manure or liquid manure. These statements in connection with the anatomical conditions lead me to explain the tan dis- ease as the result of an excessive water supply from the soil. When trees are attacked during vigorous growth, they undergo such a disturbance that the evaporation from the top is not sufficient to remove the excess of water. The decreased leaf activity, or a partial loss of foliage due to atmospheric influences or to pruning, should receive especial consideration. These cork 1 Stapf, Beitrage zur Kenntnis des Hinflusses geanderter Vegetationsbedingun- gen etc. Verh. d. Zool-Bot. Ges. Wien; cit. Bot. Jahresb., VI. Jahrg., Section I, p. 214. 2 Haberlandt, Beitrage zur Kenntnis der Lenticellen. Sitzungsber. d. Akad. d. Wiss. in Wien, Vol. LXXII, Section I. July No. 1875. 219 excrescences and phenomena of loosening of bark and wood occur also in healthy trees, with corresponding conditions in the place of growth, but in- crease in the tan disease to an extreme manifestation. The remedies are apparent, and extensive aération of the soil chiefly promises success. THE GIRDLING OF THE RED BEEcH. According to the description given by Th. Hartig', the disease named in this heading, which I have not known from my own observation, should be included here. Hartig found in a beech grove, 20 years old, that many trunks, beginning about one to two metres above the ground and extending to the top of the tree, were surrounded at intervals of 30 to 100 cm. with an almost circular, somewhat spirally running roll as thick as a quill. These rolls were proved to be overgrowth phenomena in wounds caused originally by lenticel excrescences. The formation of cork had extended further and further backward into the bark until it reached the wood and for a year or two years the formation of wood was arrested at this point. No appreciable injury due to the disease, which occurs only in very well grown sapling groups and there especially on trunks of the first or second class, could be confirmed. Root DISEASE OF THE TRUE CHESTNUT (Mal nero). This disease, very common in France, manifests itself, according to Delacroix?, most strikingly in damp, impervious soil and in grafted trees. The leaves lose their dark green color and the branches begin to dry up at the tips. The nuts only partially ripen and remain in the burrs. Delacroix found that the mycorrhiza of the fine roots had changed, as if diseased, and had assumed, as he thinks, a parasitic character because the amount of humus was deficient. The mycelium then grows into the larger roots up to the base of the trunk and then, in the trunk, upward to the branches. A secretion containing tannic acid results from the injuries to the roots and trunk. In this weakened condition, the trees offer a suitable centre for in- fection by other parasites, as, for example, Polyporus sulfureus and Armil- laria mellea as well as Sphaerella maculiformis. I include this disease at this point because of the results of a thorough investigation which I had an opportunity to make with material from Ren- nes. The explanatory letter sent by M. Crie stated that the dying branch- wood had an odor indicating fermentation if broken, or the bark removed, and he suspected a conversion of the tannin, whereby glucose and alcoholic fermentation took place. The pieces of branches sent were thickly covered with lichens and the leaves showed a browning which extended from the edge deep into the intercostal fields. 1 Hartig, Th., Vollstandige Naturgeschichte der forstlichen Kulturpflanzen, p. 211. Berlin 1852. 2 Delacroix, G., La maladie des chataigniers en France. Bull sec. mycol. de France XIII, 1897, p. 242, 220 The roots decided the matter. They had a rough appearance due to a great many black, hard cushions, differing in size and flattened into hemi- spheres, which covered the upper surface. If treated with a solution of caustic potash, when the tannin, occurring as a flocculent precipitate, turned a wine red to brown, cross-sections show that the bark excrescences were covered by a normal cork layer. The primary bark had developed parenchymatous ex- crescences the cells of which, arranged in radiating rows, had colorless walls, apparently dissolving with difficulty in sulfuric acid, and had a very firm brown content. These bark excrescences were later cut off by an hourglass- like, plate cork lamella, distending the outer cork layer, and were forced out over the upper surface of the root as calluses by the subsequent growth of the inner bark. The healthy bark was filled with starch. In the material sent me the branches had only very slightly raised bark excresences, possibly 44 to % mm. broad, flattened and hemispherical. In them was found the beginning of a many layered lenticel excrescence such as had been observed in great numbers in the cherry with the tan disease. The constitution of the leaves, still remaining on the branches, had already indicated the diseased condition of the roots. They showed a browning and drying up of the parenchyma in the intercostal fields, extending from the edge toward the mid-rib. Finally, the parenchyma was green only in the immediate proximity of the ribs. The black, yellow-edged, roundish spots, scattered over the sick leaves and containing various fungi colonies, must be considered as secondary phenomena. The condition found in the branches in connection with the excrescences on the roots brings the disease, which has been termed “Mal nero,” into the group of the tan diseases. Ac- cordingly, the choice of fibrous or good friable land which has a constant, abundant soil ventilation will be the best precaution against the disease. THE ROOTBLIGHT OF SUGAR AND FoppER BEETs. As rootblight we designate a disease of the tissues which can set in even when the young seedlings unfold their cotyledons or begin to open the first leaflets. A black spot appears on the stem below the seed leaves which spreads further toward the root end (less toward the cotyledons) and be- comes depressed. Even if the young seedling has not reached the upper surace of the soil, the first stages of the disease can be recognized. Vanha observed that the tissue becomes glassy before turning brown. The little plants begin to wilt and usually break at the diseased point. Death results at once. If the disease is limited to a small area on the hypocotyledon stem and the plant does not succumb, the depressed place will heal and a normal, later growth follows. Because the diseased place blackens and often shrinks to the size of a thread below the seed leaves the practical grower also calls the appearance “black leg” or the “threads.” The same term is used as well in the blackening and softening of the hypocotyledons of cab- bage plants, which arise, however, from other conditions. 221 It is noteworthy that often great numbers of beet seedlings are diseased, and yet frequently perfectly healthy plants may be formed close to the dis- eased ones. It should be emphasized further that, when the disease develops at all it is found simultaneously in all parts of the field, and that, as a rule, iso- lated spots are not attacked in the middle of diseased fields. As the plants be- come older, the rootblight ceases. The healed plants usually, however, remain below the healthy ones in size and sugar content and show a tendency to- ward root splitting and other deformities. Stoklasat emphasizes the fact that all varieties are not equally susceptible to rootblight. The disease has been known since the increase in beet culture in the 30’s of the last century and, according to Stift?, the discussion as to the cause of the phenomenon began in 1858 at the meeting of the beet sugar manufacturers of the Zollverein. At that time the opinion was expressed by practical growers that the trouble was due to the physical condition of the soil, i.e., a too great solidity of the soil. It was emphasized that root- blight was found only where the upper surface of the soil was hard and had not been loosened on which account a thorough cultivation and stirring were advisable. At the time scientists took up the question, the parasitic theory was already at the crest of its development. At first Julius Kuhn in 1859 gave expression to the opinion that the moss button beetle (4tomaria linearis Stephn.) attacked the plants, and, where it had eaten, the rootblight made its appearance. I have observed something similar*. The centipede and such animals were also cited as causes. This theory which prevailed for manv years was first upset when Hellriegel found that the disease could be pro- duced without animal injury and in many cases came from the beet- seed. As a result he advised a soaking of the beet-seed for 20 hours in a one per cent. carbolic acid solution*. Karlson, at about the same time, ascribed the phenomenon to a special fungus and in this emphasized the fact that only weak specimens succumbed to rootblight. Seedlings from very good seed or those which were strengthened by an energetic growth, would not be overcome by the fungus carried in these seed balls (Scleranthus)?. The experiments in sterilizing with carbolic acid and with copper sulfate showed a decrease of the rootblight. In spite of the advantage due to ster- ilization, Karlson lays especial stress on the selection of especially strong seedlings and lays the responsibility for the spread of rootblight on our present cultural methods®, which aim only at obtaining large amounts of seed and neglect the quality. 1 Stoklasa, Jul., Wurzelbrand der Zuckerriibe. Centralbl. f. Bakteriologie. Sec- tion II, 1898, p. 687. 2 Stift, Anton, Die Krankheiten der Zuckerriibe. Wien 1900. Verlag des Cen- tralver. f. Riibenzuckerindustrie. 3 Zeitschr. f. Pflanzenkr., 1892, p. 278. ‘ 4 Hellriegel, Ueber die Schidigung junger Riiben durch Wurzelbrand etc. Deutsche Zuckerindustrie, Jahrg. XV, p. 745. Biedermann’s Centralbl. 1890. p. 647. 5 Hollrung also found a lesser degree of disease in sowing large beet seed balls (Scleranthus). Dritt. Jahresb. d. Versuchsstat. f. Nematodenvertilgung. 1892, 6 Blatter fiir Zuckerriibenbau, 1900, No. 17. 222 The theory of seed sterilization was further developed by Wimmer, one of Hellriegel’s collaborators. Of the different substances used in sterilizing, carbolic acid was proved to be the most advantageous and, in fact, when used in the one per cent. solution of “Acidum carbolicutm crudum 100 per cent. Pharm. Germ. II.” To one part by weight of seed should be reckoned about 6 to 8 parts by weight of liquid. A warm water solution was proved favorable as well as a cold water solution’. While Wimmer left the question undecided as to the influence of the weather and the soil constitution Holdefleiss held to the theory that this and not parasitism caused rootblight. In soils favorable to the disease, he usually found an abundant amount of ferrous oxid, but comparatively little calcium. In this the tendency to choking with mud and incrustation of the soil are unmistakable and the discovery that rootblight was cured by abun- dant hoeing was in accordance with this. On this account Holdefleiss recommends, in addition to a continued, open condition of beet soils, a rich addition of burned (quick) lime (12 to 15 centner German per acre)* which is given with the best results to the first grown crops and not directly to the beet. Loges* had good results from the addition of 7 cent. of quick-lime per acre. As a further contributory factor, Hollrung emphasizes a lower temper- ature and the fact that rootblight never extends above the surface of the soil to the aerial parts of the axis which are exposed to air currents. He asserts definitely that rootblight is brought about by physical and chemical causes making themselves felt in cold soil, impermeable to air currents. The theory that the soils, in which black leg of the beet occurs, are easily choked with mud and become hard is substantiated by Marek and Krawezynski. Ac- cording to Stift’s statement (loc. cit. 10 to 20) in such a soil 77.25 per cent. fine sand was found. Opposed to these theories, shared by many other investigators, the par- asitic theory was still maintained and found its most active defender in Frank. Frank, with Kriiger, from 1892 on, made various experiments and determined that, besides the Pythium de Baryanum found by Lohde, and oc- curring in many diseases of seedling plants from very different genera, be- sides the Rhizoctonia violacea mentioned by Eidam, there was a specific beet fungus, Phoma Betae Frank, “which not only causes heart and dry rot of the mature beet, but also the rootblight of the young beet roots.” Re- peated discoveries in field experiments, however, soon showed even this investigator that weather and soil conditions exert a decisive influence. “It is still undecided whether the seedling thereby becomes more susceptible to the fungus attack or whether this is not sufficiently explained by the fact that cold weather delays the growth and the plant remains unusually long 1 Hollrung, in Zeitschr. f. Riibenzuckerindustrie i, D. R. Vol. 46. Part 482. 9 ee Centner in German weights equals 50 kg. or approximately 112 English pounds. ‘ 2 ’ Bericht. d. Landw. Versuchsstation Posen. 1891. * Frank, A. B. Kampfbuch gegen die Schidlinge unserer Feldfriichte. Beriln, Paul Parey, W89is) p. jaz 223 in an immature condition which is especially susceptible to the disease, while seedlings forced by heat pass rapidly through the susceptible stage and thus escape the danger.” In this explanation, after many modifications of Frank’s original state- ment, is expressed the theory that besides this specific excitor of disease, Phoma, a definite degree of susceptibility of the beet seedling must exist for {he production of rootblight. Sorauer held this point of view earlier since he proved that rootblight can exist without the presence of Phoma and that, instead of this, bacterial growth accompanies the disease. We owe the most thorough investigations of the bacteria of rootblight to Hiltner, whose recent studies we will consider with great thoroughness after sketching Stoklasa’s theory. According to Stift’s statements (loc. cit. p. 17) Stoklasa admits that bacteria can produce rootblight in beets, and he considers the following species capable of doing so:—Bacillus subtilis, B. liquefaciens, B. fluore- scens liquefaciens, B. mesentericus vulgatus and B. mycoides; Linhardt de- clares the latter to be the essential cause of injury. Recently Pseudomonas campestris has been added to these. Stoklasa considers that the above men- tioned atmospheric and soil conditions produce a predisposition in the beet seedlings. He turned his attention especially to oxalic acid, normally formed by the life process of the plant as potassium oxalate. Soluble oxalates, which act as poisons, are transformed into an insoluble calcium oxalate, if calcium oxide can be taken from the soil by the root hairs. By thus neut- ralizing the oxalic acid its retarding action on the process of assimilation ceases and the plant recovers. If much nitric acid is present in the soil or is added in excess (strong fertilization with nitrate of soda), an hastened de- velopment takes place at any rate, but at the same time the oxalic acid con- tent increases. In such a case, if the young beet plant cannot take up suf- ficient calcium, it becomes predisposed to rootblight. As already said, we owe the most thorough study of the relation of bac- teria to this disease to Hiltner and Peterst. These investigators made a number of experiments and found that there are soils which almost never show any rootblight and, conversely, there are others in which the disease al- most always appears. They concluded from this, that many soils are in a con- dition to lend a certain protective power and they perceive that this pro- tective peculiarity is the ability of the immunizing soil to provide the outer- most cell layers of the roots of the beet seedling with such micro-organisms as can prevent the penetration of fungi and bacteria producing rootblight. Hiltner and Peters call this protective sheath, which they had observed similarly in peas, “Bacteriorhiza.” If its formation be prevented by steri- lizing the soil and killing the protective soil organisms, in case the seed had not been previously sterilized, the fungi and bacteria causing rootblight could enter the young seedlings and destroy them. 1 Hiltner, L., and Peters, L., Untersuchungen iiber die Keimlingskrankheiten der Zucker- und Runkelriiben. Arb. d. Biolog. Abt. f. Land-und Forstwirtsch. am Kais. Gesundheitsamt, Vol. IV, Part 3, 1904, p. 207. 224 The words of Hiltner and Peters themselves best show how little the organisms per se are to be feared and how the chief cause of the disease is to be sought in the conditions making the plants susceptible. In speaking of the results of their experiments, they say (loc. cit. p. 249) “this result, how- ever, shows that the production of diseased seedlings in the seed bed presents a rather complicated phenomenon. This cannot be laid exclusively to the fact (heretofore almost universally accepted) that parasitic fungi or bacteria ac- cumulate on the seed balls, then passing over to the roots, for these organ- isms in themselves cannot cause the diseased conditions of the beet. Only after the resistance of the roots has been weakened by the influence of cer- tain substances, viz., oxalates, can otherwise harmless parasites attack them.” According to Hiltner’s theory, the substances or circumstances predis- posing a plant to disease are produced by the decomposition of the tissue in the seed balls, either on the field as a result of unfavorable weather, or later in storage because of too great warmth. A work by Sigmund! reports upon the advance given to the occurrence of rootblight by the fact that the micro-organisms especially concerned in it (Phoma and Bacillus mycoides) find certain organic compounds in the nutrient solution of the host. After he had emphasized the fact that the parasites are not able alone to increase the disease, he mentions that the number of diseased beet seedlings can be increased if glycocol, uric acid, asparagin, hippuric acid, leucin, etc., are found in the nutrient solutions of the micro-organisms named and the beet balls are soaked in this nutrient so- lution. In this important disease we have simply listed, first of all, the various theories and results of investigations as they have appeared from time to time, in order to show that with all observers, in spite of their very different points of view, one statement is found running through all their discussions like a red line, viz., the influence of the soil’. This influence shows itself most distinctly in heavy, binding soils. It can make itself felt also on other soils if they are encrusted for any reason whatever. The prime factor under such conditions is the scarcity of oxygen. At present we cannot say defi- nitely what processes are started in the soil, seeds and the young plants. In the same way, no definite decision can be made as to whether rootblight is a constitutional disease, i.e. a deflection of the normal life functions leading to tissue decomposition, or a parasitic process, i.e. a process producing the . same result but caused by the co-operation of micro-organisms. If, as we believe, in the majority of cases the latter should be granted, we must bear in mind emphatically the fact that these organisms, no matter whether fungi 1 Sigmund, Wilh. Beitrige zur Kenntnis des Wurzelbrandes der Riibe. Natur- wissensch, Zeitschr. f. Land- und Forstwirtschaft, 1905, p. 212. 2 Further material from practical sources may be found in the annual reports of the Special Committee for Plant Protection. (Jahresberichte des Sonderaus- schusses fiir Pflanzenschutz. Deutsch. Landw.- Gesellsch. 1892-1905). 225 or bacteria, can only destroy the seedlings where they have some predis- position to take up such organisms. This predisposition is the product of the soil in which they are grown under definite atmospheric conditions. Therefore, the soil condition is always the first cause affecting the as- similatory process and inducing rootblight. The question whether this affec- tion always takes place with an excess of free oxalic acid and whether the abundance of the acid acting poisonously is due to the formation of more acid by the plant body or that less acid is oxidized because of a scarcity of oxygen, may be left for later investigation. It is enough for our purpose to know that the disease is a result of a binding consistency of the soil under unfavorable atmospheric conditions, i.e. cold, wet weather. We will now return to the statements of practical workers, who, from the beginning, have insisted that the cause of rootblight lies in the condition of the soil. When citing these expressions, we come to the self-evident regulations for fighting it. Briem reports a case from the years 1904-1905*. On a newly broken field near Prague in 1904, with cold, wet weather, and a consequent slow growth, beets were extensively root blighted although until that time the phenomenon had been rare. Also, the beets did not revive completely until later. The same field in the following year, after a rich fertilizing with potassium, nitrates and phosphates, was again planted with commercial beets. As a result of the very wet, cold weather, the seed sprouted only at the end of two weeks (on the 24th. of April). It was feared that, with the weakened growth resulting from the cold nights, rootblight would again set in. Fort- unately this did not happen and the warm days, coming at the beginning of May, soon caused the rapid, vigorous unfolding of the first pair of leaves. However, when, on the 20th of May, a violent rain had beaten the field down unusually hard so that water could only soak in very slowly, many seedlings showed the beginning of rootblight after five days. This example of the result of a sudden exclusion of the air from soil, beaten hard by rain, shows therefore that it is primarily advisable to\ keep the upper surface of the soil constantly open by cultivation. Secondarily, even if the soil contains lime, a further supply of quick lime must be given. The effect of the lime must not always be considered as a nutritive means, but as a mechanical one for improving the soil since it increases its friability. Superphosphate has given good results’. In fields liable to these conditions, increased attention should be given to the use of as vigorous seed as possible. If one wishes to sterilize the seed which, according to our theory, is of very little advantage®, a carbolic acid solution should be used. For the sterilization of one hundred and twelve pounds of beet seeds 1.5 k. carbolic 1 Briem, H., Wurzelbrandentdeckung und kein Ende. Blatter f. Zuckerrtibenbau v. June 15, 1905. 2 Zeitschr. f. Pflanzenkrankh., 1896. p. 54 and p. 340. Landwirt, 1896, Nos. 15, 17, 21. Jahresber. d. Sonderausschusses f. Pflanzenschutz, 1902. 3 Hiltner in Mitteil. d. pflanzenphysiolog. Versuchsstat. Tharand. Sachs. landw. Zeit. 1904, Nos. 16-18. 226 acid (Acidum carbolicum liquidum crudum 100 %) or the more expensive, pure crystallized acid in 3 hl. water. To test the acid’s desired solubility, 0.5 grams should be shaken thoroughly in one litre of water; this should dis- solve in from 5 to 10 minutes. When the sterilizing solution is ready, the seeds are poured into it and stirred about repeatedly and _ vigor- ously in the course of the next few hours. Then the seed is pressed down with weighted boards so that it remains entirely covered by the solution. After about 20 hours it is taken out and spread in a thin layer in an airy place and stirred often with a rake. As soon as it is sufficiently dry it can be planted with a drill, but it may lie for some time, when completely dry, without being injured. If it is desirable to use the sterilizing solution several times, it is neces- sary only to replace the liquid lost by pouring in the needed quantity of a stock solution. However, considering the cheapness of the material, it is well not to use the solution too often’. Instead of sterilization, the coating of the seed with calcium carbonate seems to us to be advantageous. But the main thing is to work the soil, for even the most carefully handled seed, found to be faultless in the germinating tests, can become dis- eased. Hiltner, in his above-mentioned work, gives some suggestions in this connection which are well worth consideration. Up to the present in trade, the quality of the seed has been tested according to its behavior in the seed bed, by means of a suitable method. It is now seen, that the number of diseased seedlings increases, the longer the seed is left in the seed bed. - Ex- periments show that if, for example, the seedlings are taken from the sand seed bed on the 9th day, often more than ten times as many are found to be diseased as when taken out on the 6th day. To this it should be added that if the seeds lie close to each other the mutual infection is considerable. Be- sides this, the number of diseased seedlings differs greatly, depending upon whether the seed was soaked or not and whether distilled water, water free from calcium, or water containing calcium, was used for the. soaking. if finally it is taken into consideration that the constitution of the soil de- cides the subsequent behavior of the seedlings, it will be concluded that the methods at present used for judging of the quality of the seed give no pro- tection and no standard for beet seed. In order to obtain an insight into the germinating power, the best seeds will have to be tested in as many germi- nating seed beds as possible and with different methods”. The best germinat- ing results, however, in no way give a guarantee as to rootblight. This depends upon whether the micro-organisms present in the dried blossoms, containing the seeds, find an opportunity of so developing in the soil that they can attack the young seedlings. "1 ~Wilfarth, H., and Wimmer, G., Die Bek’ampfung des Wurzelbrandes der Riiben durch Samenbeizung. Zeitschr. d. Vereins d. Deutschen Zuckerindustrie, Vol. 50, Pant 529; 2 For the difference in germination of the seed treated in the same way but sown in sand and in soil, compare the reports by Marek in the year Book of the German Agricultural Society. (Jahrb. d. Deutsch, Landwirtsch. Ges. 1892.) 227 TROPICAL PLANTs. In consideration of my standpoint, that in much of our cultivation too little account is taken of the soil conditions, especially of its physical consti- tution, I think it necessary to refer also to the demands of tropical plants on the physical peculiarities of the cultivated land. In regard to tropical plants, I base my theory on the statements of Fescat who has often given his own experiences, and further, on the recent publications of the Biological Agri- cultural Institute at Amani’. As we shall see, in these injuries, as in those in temperate climates, phenomena are often involved which are due to scarcity of oxygen mani- fested in heavy soil or in soils which have become compacted through culti- vation. Many plants in the tropics can develop accessory organs with a scar- city of oxygen, like the adventitious roots from the trunks of trees buried or covered with slime. The palms (Phoenix, Kentia, Chamaerops etc.) can develop root branches growing perpendicularly out of the soil which have a peculiar respiratory arrangement (Pneumathodes) ; this appears as a mealy coating extending backward for a certain distance from the tip of the root. This mealy condition is produced by the increase, enlargement and breaking up of the outer layers of the rootbark with a rupturing of the epidermis and an almost complete suppression of the schlerenchymatic ring. Jost* deter- mined experimentally with Phoenix that these pneumathodes remain in the soil when it is well aérated, but, on the other hand, are raised above the sur- face of the pot if it is submerged in water. Similar arrangements were found also in Pandanus, Saccharum and Cyperus. Root-Rot OF THE SUGAR CANE. Among the numerous diseases of sugar cane, root-rot plays a prominent part. In Java it is considered the worst enemy of sugar cane culture. Nat- urally growers have not failed to cite the micro-organisms (Verticillium (Hypocrea) Sacchari, Cladosporium javanicum Wakker. Allentospora rad- icicola, Wakker, Pythium etc.) colonizing on the diseased roots as its cause. Nevertheless Kamerling’s* recent experiments have now confirmed beyond all doubt the supposition that a constitutional disease is concerned here, : a Fesca, Der Pflanzenbau in den Tropen und Subtropen. Berlin Siisserott. Vol. ; 4, 2 As said above, the statements on the phenomena of disease in cultivated tropcal plants serve chiefly as proof of the necessary consideration of soil and at- mospheric conditions as a cause of disease. In the descriptions we can sum up the material more briefly since abundant literature easily makes possible special studies. Besides the magazines already mentioned, pp. 65 to 67, the recent publica- tions of the Usambara-Post furnish valuable material. ‘‘Der Pflanzer,’ Adviser for Tropial Agriculture” issued with the co-operation of the Biological Agricultural In- stitute, Amani, by the Usambara-Post, 1905. (‘“Der Pflanzer,” Ratgeber fiir tropische Landwirtschaft unter Mitwirkung des Biologisch-Landwirtschaftlichen Institutes Amani, herausgageben durch die Usambara-Post, 1905.) eae ocst Ein Beitrag, zur Kenntnis der Atmungsorgane der Pflanzen. Bot. Zeit , No. 37. 4 Kamerling, Z., Verslag van het Wortelrot-Oenderzoek, Soerabaia, 1903, 209 pages, with 19 Plates. 228 resulting from compacting the soil. Raciborski with Suringar’ has expressed the theory, earlier proved, that by transplanting sugar cane, which had suf- fered from this root disease, known as Dongkellanziekte, to other soil, the plants would become healthy. The disease occurs especially on heavy clay soils and manifests itself in Java, when at the beginning of the spring mon- soon the plants die with alarming rapidity after they have already shown for some time an abnormal branching of roots and also deformed root hairs. He investigated the soils in which the disease occurred and found that they did not have sufficient friability and easily became compacted. The permeabil- ity of the soil can be increased by supplying humus, since this, as also ferric hydroxide, or silicate rich in iron, favors the formation of friable soils. Since the humus is gradually lost by oxidation, care must also be taken to retain the porosity of the soil by a renewed supply of stable manure, rice straw or green fertilizer (compost). According to Wakker’s® studies, many leaf spot diseases seem either directly produced by moisture in the soil (if of a parasitic nature) or favored by this moisture. Wakker found in the vicinity of Malang “a yellow streak- ed, banded disease,” “rust,” “ring spot disease,” as well as the red and yellow spot disease. While he considers the first named as a parasitic phenomenon favored by moisture, he explains the yellow spot disease, in which the leaves acquire somewhat elongated, greenish yellow spots running into one another, as a hereditary constitutional disease. 39 66 DISEASES OF COTTON. The majority of the cotton diseases may be considered at present to be of parasitic origin, but I doubt if this will always remain the case. With the conviction that many of the micro-organisms already found are to be con- sidered parasites of weakness, naturally the first existing factor must be considered as decisive, viz., the disturbance in nutrition causing the weak- ness which first offers the possibility of infection by the fungus. This will have to be sought primarily in weather and soil conditions. Examples of disease, in which only the soil is considered as the cause in the rainy season, are reported by Vosseler* from our East African col- onies. In 1904, in the district of Kelwa, there occurred a “browning of the stems,” which produced greater damage in that region than all the other diseases which had appeared up to that time. Brownish black spots were produced in the bark below the tip of the main shoot, as a result of which followed the dying of this part as well as of the upper lateral shoots. The disease appeared, however, only on so-called sour soil. 1 Kamerling, Z., en Suringar, H., Oenderzoekingen over onvoidoenden groei en ontijdig Afsterven van het riet als gevolg van wortelziekten. Mededeelingen van het Proefstation vor Suikerriet en West-Java, No. 48; cit. Zeitschr. f. Pflanzenkr., 1901, p. 274, and 1904, p. 88. 2 Wakker, J. H., De Bladzeikten te Malang. Archiev voor de Java-Suikerindus- trie, 1894. Aflevering 1. 3 Vossler, Zwei Baumwollkrankheiten. Immune Baumwollsorten. Mitteil. Biolog.-Landwirtsch. Institut Amani, 1904, No. 382. 229 The red spot disease of the leaves, occurring to a devastating extent along the whole coast, was a second phenomenon. A pale border appeared along the edge of the leaves; the zone was distinctly cut off from the inner portions by a zigzag line. Dark red spots, or a uniform red coloration with which a deforming of the leaf surface was often connected, then appeared. The disappearance of this trouble with the appearance of drought indicates that the soil during the prevailing wet weather had unfavorably affected the growth of the cotton. Vosseler seems to suspect that the dreaded “wilt dis- ease” should be included among the climatic diseases and refers in this to the possibility of producing immune races by growing plants from seed of healthy stock in diseased fields. According to Schellmann', cotton cannot grow on stiff clay soils and sour humus soils. Castor BEAN CULTURES. Although Ricinus thrives in subtropical and even in temperate zones, according to Zimmermann’, it is extensiVely cultivated only in the tropics where it grows from sea level up to possibly 1600 m. The oily seeds are the desired crop. At any rate an abundant supply of nutriment is needed for Ricinus, since it makes very great demands on the soil. The plant also re- quires large amounts of water while growing. Later, however, the physical constitution of the soil has a determining value in the matter, since the plants do not thrive in all soils which, not well drained, remain constantly wet. These observations in the tropics correspond with our experience in growing Ricinus as a decorative plant. Only the plants develop well which have plenty of room and a porous soil, rich in nutriment. When grown in pots, to which much nutriment is added by fertilizing salts, the earth becomes encrusted and the plants remain small and weak. TOBACCO. Very instructive examples of the determinative influence of the soil are furnished by Hunger’s* observations on the development of the Delhi- tobacco and its different behavior toward the “Mosaic Disease,’ which will be reported more fully in the section on enzymatic diseases. Hunger says that a soil of white clay in which much sand has been mixed, is the best for thin-leaved tobacco if the amount of precipitation is favorable, but at the same time this also favors most the abundant appear- ance of the mosaic disease in the form of the so-called “gay-head.” Here, after topping, the plant gives the impression of having made too rapid growth; long internodes, a yellowish-green foliage, a great many lateral shoots, all of which are sickly. 1 Der Pflanzer, Usambara-Post, 1905, No. 1. Here also older literature. 2 Zimmerman, A., Die Ricinus-Kultur. Der Pflanzer, Ratgeber ftir tropische Landwirtschaft unter Mitwirkung des Biologisch-Landwirtsch. Institutes Amani, herausg. durch d. Usambara-Post 3 Zeitschr. f. Pflanzenkrankh. 1905, Part 5. Hunger, as Botanist at the experi- mental station for Delhi-Tobacco (VIII Abt. d. Bot. Gart. zu Buitenzorg) has had at his disposal most extensive material for observation. 230 If the clay soil lacks sand, however, and becomes loamy, it is useless for tobacco culture. The roots of the plant develop scantily and are often deformed. The leaves are not of the right length and are of poor quality. The mosaic disease appears a week or two after transplanting. The red, atmospherically disintegrated soils of Ober-Langkat are pretty compact and here the plants are squatty; the leaves standing close above one another are not especially thin while the mosaic disease occurs rarely. It only appears exceptionally on the shoots which, after topping, develop sparsely. On dark soils rich in humus, tobacco has an enormous, well-proportioned development; the very large leaves are dark green and thin. The mosaic disease abounds. This disease scarcely, if ever, occurs on the peaty, porous, Paja soil, which has a high water-holding capacity. The enormous leaves almost never wilt in the soil containing much water, but are very thick and rich in oil; with fermentation they become dark colored and are therefore not very valuable. On fresh Paja soil the mosaic disease cannot be produced even by topping. COFFEE. The tree, which of all our tropical plants deserves the most consider- ation, coffee, is extremely susceptible to soil conditions; although droughts are not favorable and it likes best to grow in soil which even at a time of drought keeps fresh, yet it withstands drought much better than too much moisture. If, during the rainy season, it is covered with water for only a few days, it becomes irretrievably diseased. A sufficient capacity for water in the soil, combined with abundant aération, is therefore its chief need. Freshly cleared forest soil is found to be especially favorable for its culti- vation. Black rust (swarte roest) and canker diseases (Natalkrebs and Java- krebs) (Djamoer oepas) with their diseased cambium are probably physiolo- gical disturbances introduced by unfavorable soil and atmospheric conditions and result later in fungus attack. The Liberian coffee is said to be less sus- ceptible to impervious soil than the Arabian, and flourishes where the latter fails?. The leaf disease described by Zimmermann as “Blorokziekte’’* seems io me also to belong here. The leaves develop convex, yellow spots. Later, the epidermis ruptures on these spots and the cell contents turn brown. The trees in Java, to be sure, are not killed by this disease, but their fertility is greatly reduced. As the result of an excessive water supply, Zimmermann observed? the so-called “‘little stars,” occurring rarely in Coffea liberica and more frequently in C. arabica; i.e. blossoms which open prematurely when incompletely developed and therefore remain sterile. The disease should 1 Delacroix, G., Les maladies et les ennemis des caféiers. II édit. Paris, Chala- mel, 1900, p. 8. 2 Teysmannia 1901, p. 419. 3 HMenige Pathologische en Physiologische Waarneminger over Koffie. Mededee- lingen uit S’Lands Plantentuin, LXVII. 231 not be confused with the black discoloration of the blossom buds passing under the same name. These buds finally fall off unopened. Different kinds of root moulds have been described and considered as the cause of root-rot’. I think it will be necessary to study here the question whether parasitic fungous forms can attack the plant injuriously only when the roots have already been weakened by unfavorable nutritive conditions. Cocoa AND TEA, Fesca says in regard to the cocoa tree “extremes of soil structure, poor sand, as well as tough clay, are not favorable to the cocoa tree. Rather it demands greater soil depth and freshness, without the necessity of enduring standing water, as well as greater humus and nutrition content, than does coffee.” The same author, who himself has analyzed good tea soils in Japan, say of tea, that he found in a more compact soil, 30 to 40 per cent. of water as capillary water. Tea demands a sufficiently deep soil which is free from standing water, to which it is very sensitive. Here too a still little understood fungus is described as the cause of a root disease. It is said to result in the early death of the bushes, especially when growing on damp soil. Neverthe- less Fesca? assures us that he has never yet seen the disease on well aerated soils. We might also trace the diseases of young tea plants described by Zimmermann? to an unfavorable place of growth, although a fungus bearing iobed haustoria has been observed at the disease centres. The leaves become flabby and discolored ; the stems turn brown at the base or higher up where the root seems healthy. Often only the leaves show brown spots, especially on the midrib. The fungi developed from the diseased parts of the stem (Nectrieae) could not produce the disease even in infection experiments. In dry weather the disease decreases considerably. Also transplanting the seedlings from the closely planted seed bed arrested the disease. If we have considered here with the greatest brevity the soil demands of our most impor- tant cultivated tropical plants, it must still be added that naturally the climate remains the decisive factor. Among these climatic factors especial attention must be given to humidity since the quality of the harvest often depends considerably upon this. In cocoa plantations in Kamerun, for instance, it may be observed that the quantitative production of the trees is unusually abundant, but the quality of the fruit is only mediocre as the result of great dampness. The trees also are short-lived here. OTHER TROPICAL PLANTS. Of grains, Maize requires, first of all, a deep, mellow soil free from standing water and cannot thrive on tough clay. Sorghum behaves similarly, but is still more sensitive to cold and dampness and, because of its deep root 1 Bolletim del Institto Fisico-Geographico de Costa Rica, 1901, 2) NGOC! Cit Ds aio. 3 Zimmermann, Untersuchungen iiber tropische Pflanzenkrankheiten. Sonder- berichte tiber Lan- und Forstwirtschaft in Deutsch-Ostafrika, Vol. II, Part 1, 1904. 225 system, is very resistant to drought. This accounts for its growth on tropi- cal and subtropical steppes. The Negro or brush millet (Pennisetum spica- tum) is entirely unsuitable for firm soil, but is excellent for porous soils in dry localities. The other millet varieties behave similarly. The Leguminoseae, which are suitable for growth as a second crop be- cause of their usually short vegetative period, may, in the tropics and sub- tropics, acquire great importance not only as collectors of nitrogen and as an excellent nutritive substance, but are also valuable on account of their close shading of the soil, preventing it from hardening and ‘as soil loosening, green manuring plants. The plants make good growth in dry soils ;—accordingly -heavy soils, in regions with abundant precipitation, are not suitable for them. Busse? has given more detailed studies of sorghum diseases and their rela- tions to atmospheric conditions. Of tuberous plants, the sweet potato requires about the same cultural conditions as our potato. The cassavas (Manniok) require deep, loose, dry soils, but rich in humus. The moisture-loving Maranta species, furnishing arrowroot, also requires looseness of the soil, on which account virgin soil is found to be less suitable because of its compactness. Even Jaro, the tubers of the different Colocasia species, which requires a great deal of moisture, flourishes only when the soil is pervious. The same is true of the Yam, which is derived from different species of the genus Dioscora. In regard to poppy culture and the harvesting of opium, reference should be made to Braun’s? work, and in regard to rubber plants and especially the Liana, root and herbaceous rubber plants, to studies by Zimmermann’. MEANS FOR OVERCOMING THE DISADVANTAGES OF HEAvVy SOILS. Drainage. In this we have to take into consideration not only soils rich in clay, but also those sandy ones whose graular structure is so fine that they can become as closely compacted as clay soils. Of the practical means used to increase soil aération, drainage deserves to be named primarily. It facilitates the exchange of air in the soil inter- stices as well as removing stagnant water accumulations after every rain. The drainage pipe acts as an apparatus for sucking up air. When the rain fills the soil, it forces out the air which has a less oxygen content than the atmosphere, but is richer in carbon dioxid. But since the rain is quickly soaked through the drains, air rich in oxygen streams just as quickly from the surface down into the pores increasing, thereby, the processes of oxida- tion in the soil and the activity of the roots and micro-organisms needing oxygen. The fear that drainage will impoverish the fields has rarely any founda- tion, since the numerous analyses of drain water show only slight traces of 1 Busse, Walter, Untersuchungen tiber die Krankheiten der Sorghum-Hirse. Arb, d. Biolog. Abt. f. Land- u. Forstwirtschaft a. Kais. Gesundheitsamte, Vol. IV, Part 4. 1904. 2 Der Pflanzer, 1905, No. 11-12. 3 Ibid, Nos. 8-10. 233 potassium and ammonia as well as phosphoric acid, which had been ab- sorbed by the friable soil. Nitrates, because of their easy solubility, at any rate, are lost in larger amounts, but they are also partially washed away from undrained soil into the subsoil. Further, the soil capacity for heat, increasing with drainage, should not be underestimated as well as the improvement of the crop produced, of which it may be said in general that damp, and therefore cold, soil produces crops poorer in nutriment. The reason why damp soil is cold is evident from considering the fact that if water has a specific heat equal to one, the highest specific warmth ever shown by soil is only equal to 0.5; i. e. at most half that of water. If this water which is the hardest to warm is removed by drainage, the soil must become warmer. Previous to drainage, the soil remained cold until late in the spring, thus causing a later awakening of vegetation and a later germination of the seed. A cold place of growth is especially disturbing to young plants, since it holds development back in a developing phase, which is determinative for the whole later plant. The root system becomes poor, the appearance sick, and later favorable temper- ature conditions are not able to overcome the bad condition. One of Stock- hardt’s! experiments with winter rye may serve as an example. The ex- perimental plots differed in drainage and soil porosity. One plot was traversed at a slight depth by a drain possibly 2.5 cm. wide and in such a way that the pipe, bent at right angles at one end of the drain, opened like a chimney toward the upper surface of the soil. The soil of this plot, as well as that of the undrained one, was broken up 50 cm. deep, while a third plot was dug only 25 cm. deep and not drained. In corroboration of earlier results obtained with lupin, oats and the like, the harvest showed an ap- preciable excess on the drained lot, although the young plants showed no difference before spring. Reckoned per acre this crop amounted as follows: Grain Straw Totals and Chaff kg. kg. kg. Part 9) 1, drained and: dug: 50 cm deep 539 1470 2009 Part II, undrained and dug 50 cm. deep All 928.5 1339.5 Part III, undrained and dug 25 cm. deep 338 859.5 1197.5 Grain content Nitrogen content per bu. of the grain otek: 40.80 kg. 2.16 per cent. Let IL. 39.85 kg. E83 ine. 7 ot ELE. 37.70 kg. LiG2ieaviras: Patz”, referring to the use of drainage for removing iron from newly broken soil, says, “usually iron is found directly under the surface of the soil and at the height of the usual ground water level. The ground water 1 Chemische Ackersmann, 1859, p. 232; 1861, p. 100; 1864, p. 22 2 Hannoversche landw. Zeit. 1280, No. 45; cit. Biederm. Centralbl. f. Agrik.- Chemie, 1880, p. 911. 234 carries the iron upward and in many cases cements the sand grains in the soil at the usual height of the ground water level in such a way that often in laying a drain, a hard, stone-like, red soil is found. By laying drains cor- rectly and systematically, with the horizontal drains intersected at right angles by the absorbing drains, the latter having at least a depth of 1.2 m. and the distance between every two drains being kept 10 times the depth, the level of the ground water will be lowered to the depth of the drain and no more iron will be carried to the soil above the pipes. The iron already present in the soil will be dissolved by the atmospheric precipitation and led to the dainage pipes or it will remain in the soil as the non-injurious oxid.” Working of the soil. Where there is no need of carrying away excessive water, furrowing and deep plowing, instead of drainage, will often serve the same end. In this care must be exercised if, with fertile, friable soil, there is a prospect of bringing a dead subsoil to the upper surface by the furrowing or plowing. In addition to fertilizing each time, the gradual deepening of the friable soil should take place at least over a period of several years. Since, with the deepening of the friable soil, the root surface becomes extended and, accordingly, an increased harvest takes place with a greater utilization of the soil, an increased supply of manure is demanded with the increasing loosening of the soil. In soils inclined to crust, but otherwise not unfavorably constituted physically, hoeing and hilling suffice for increasing the soil aération. This cultivation, which can scarcely be sufficiently recommended to the agricul- turist and the gardener, and which can be used in any soil, regulates the soil moisture. Some good, practical experiences as to the advantages of loosening the soil, may be found in the reports of the German Agricultural Society’s special committee for the protection of plants (Landwirtschaft-Gesell- schaft). We will cite a single example which is supported by comparative experimental cultures. In Skollment (East Prussia) Mentzel divided into two parts a field planted with mixed Swedish wheat, Epp wheat and Kas- tromer wheat, and kept one half of it loose by harrowing after every rain,—, i.e. by working with the narrow bladed cultivator,—but did not work the other half. Although its soil was better, the latter half yielded only 2160 ke. per acre, the former, however, 2650 kg. A green manure fertilizer turned over deep in light soils and super- ficially in heavy soils, acts in the same way as this loosening of the soil sur- face. By means of this green manure the capillary raising of the water from the underlyng soil layers especially is interrupted. On the one hand, the moisture is thus retained in the deeper layers of the lighter soil; on the other hand, in heavy, wet soils, a well aérated, friable surface is formed so 1 Jahresb. d. Sond.-Aussch. f. Pflanzenschutz. Arb. d. Deutsch. Landwirtsch.- Ges., Part 107, 1905, p. 64. 2 King, F. H., Tenth Annual Report of the Agric. Exper. Stat. of Wisconsin, 1884. p. 194. 235 that the seeds can germinate normally. The stronger, more sturdy plants, which have passed through the most critical germinative stages, are then better able to combat the soil moisture, which rises capillarily higher and more rapidly after the green manure has decomposed. Freezing. The loosening of heavy soils in winter through a suitable freezing is of the greatest importance in their cultivation. If we take into consideration that water, when converted into ice, expands about one- eleventh of its volume, it is evident that the more closely lying soil particles are forced apart by the ice crystals. Also, since rocks are covered with a network of fine cracks, into which the water gradually soaks, the frost is constantly decomposing them and in fact the effects are greater as the freezing and thawing alternate during the winter. Naturally the rapidity of the action will depend upon the composition of the soil, i.e. on its water content. The smaller this is, the more quickly and deeply the frost can penetrate. Therefore, heavy and humus soils will freeze and thaw most slowly. Wollny’st experiments show the advantage accruing to the soil from the loosening action of the frost. He had two plots of land loosened up in the fall and left lying in open furrows, while a third was not worked. This plot and one of the two others were turned over in the spring while the third was worked only superficially. It was then proved that for the various plants cultivated, the yield was smaller from the plot which had not been left fallow in the fall, while the largest harvest was given by the one in which the open furrows froze during the winter and were broken up once more in the spring. Mulching. We now come to the advantage derived in heavy soils from the covering of the friable surface with litter, after having considered earlier the protection given light soils by such a covering. The greatest advantage is that the covering substance prevents the compacting of the soil particles since it takes up the force of the rain drops and, conducting the water slowly, spreads it over the surface of the soil, thereby keeping the friable surface more porous. In nurseries the seed also germinates more uniformly in covered beds. The weeds do not grow so vigorously and can be more easily and completely rémoved, since they root more superficially in the looser soils. The great air variations between day and night produce a heavy for- mation of dew in the porous covering material. This runs off to the benefit of the underlying soil and increases its fertility. If bark is used to a depth of 1 to 1% inches, it furnishes a covering for the seed beds in winter and, in the spring, a protection against the penetration of frost and the cracking of the soil. Seed and seedling beds should have water given them in June or July. In August the ground is harrowed and, in case the bark should then be covered too deeply, the exposed soil is covered with new bark. Snares for the control _1 Wollny, E., Ueber den Einfluss des Winterfrostes auf die Fruchtbarkeit der Ackererden. Biedermann’s Centralbl. 1902, p. 301. 236 of the unevitable June bug are made of heaps of scattered, moist bark which heats itself. The June bugs lay their eggs in these heaps which later, with a part of the underlying earth, are put in a wagon and worked up with peat, or lignite, ashes, lime, plaster and organic refuse to a compost pile, which, after a year or two, kills the grubs. HARROWING. Harrowing is a process which should find mention here. Anderegg* has published very noteworthy results of harrowing meadows. A meadow of uniform soil composition and mould was divided into four eaually large lots. These yielded,— (1). Unharrowed and unfertilized....... 377 kg. hay (2). , Unharrowed but ferulizeds- en. 833 kg. hay (2). “elatrewed but- unfertilized. 73.22. 770 kg. hay (4)2 ) Harrowed and tertilized ate eee 1503 kg. hay Harrowing winter sown grains not only re-opens the encrusted soil, but also increase considerably the formation of young shoots. Director Con- radi?, however, justly points out the fact that the harrow is usuable only if the crust is not too thick and the soil not too binding. Also, if an encrusta- tion in spring may be foreseen, the seed must be more thickly sown since harrowing destroys plants and the sand is thinned. For that reason har- rowing is very useful occasionally in thinning the plants. The increased standing room for the plants left in place gives a greater supply of light to the basal nodes and starts the lateral shoots into a rapid growth and pre- vents their too rapid lignification when these buds obtain moisture from the earth heaped up by the harrowing. If the earth is not pulverized sufficiently by the harrow, the roller, and preferably a wheel roller, must be used in ad- dition. In the majority of cases the roller will have to follow the harrow, because binding soils are not made absolutely fine by the harrow, and also because it is desirable that the earth torn away from the base of the plants may be pressed back again. The best time for harrowing depends on the development of the plant and the water content of the soil. If the plants have grown too far or continuous dry weather prevails, the harrowing should be omitted or, in the latter case, should never be carried out without a subsquent rolling. A few words also might be pertinent here as to the significance-of stones in the soil. In this connection, Wollny’s? experiments have shown that with a high, constant air temperature (during the warmer seasons) soil covered with stones and mixed with them is slightly warmer than is that free from stones. With a falling temperature comes the reverse. During the daily minimum soil temperature, soil containing stones is for the most 1 Tllustr. landw. Vereinsblatt, 1880; No. 8; cit. in Biederm. Centralbl. f. Agrik.- Chemie. 1880, p. 693. 2 From “Der Praktische Landwirt” in Fiihling’s landw. Zeit., 1880, p. 151. 3 Wollny, Fiihling’s landw. Zeit. 1880, p. 314. ws 237 part colder than that free from stones, while during its maximum it is warmer. In regard to conditions of moisture, field soil covered with stones is found to be wetter during the warmer seasons than uncovered soil of otherwise similar composition. Soil covered with stones lets more water slip through than does one not so covered. Tue Use oF Lime, MARL AND PLASTER. The importance of lime arises from its chemical action as a direct nutritive substance as well as from its properties, which change the mechan- ical constitution of the soil. Aside from favoring friability, it should be emphasized that the lime attacks the silicate in clay soils and sets free sol- uble potassium compounds. By its more rapid destruction of the organic substances, it causes a better decomposition of humus. In regard to the technique in using lime, it is advisable to keep burnt (quick) lime in baskets under water until no more air bubbles arise (possibly 2 to minutes) and then to heap up the pieces in layers. They decompose (slake) of themselves and the lime stone, which lost its carbon dioxid in the previous burning, now becomes the white powdery calcium hydroxid (Ca(OH),) and as such represents slaked lime, which is soluble in 730 parts of cold water, and only in 1300 parts of boiling water (lime water). 100 parts of quick lime correspond to 132 parts of slaked lime. The lime should be uniformly spread over the field in quiet weather by hand, or with a suitable shovel. It is well to spread it in the fall on the stubble and then to work it under the surface. If it is necessary to wait until spring, it must be spread as early as possible before seeding, as soon as the soil has dried. Smaller doses (750 kg. to 1500 kg. per hectare) repeated about every five years, are more advisable than a single heavy liming, because, in the latter, the decomposition of the humus is so violent that the subsequent increase in the harvest is at the cost of a later production. It is said in practice that fer- tility is difficult to maintain on a lime-stone soil, because organic matter dis- appears rapidly. Naturally the amount of lime depends upon the soil. Tough clay soil will bear most, while great care must be used with poor sandy soil. Soils which are lacking in organic matter or have water standing on them, may not be limed at all. The results which become evident most quickly are given by a humus soil poor in lime ;—Sorrel (Rume-x acetosella) indicates a scarcity of lime. Lime will act here splendidly as a fertilizer. If local lime deposits be used, such as possibly meadow-lime or marl, or the so-called waste lime (gas lime, lime ooze, lime ash), it is distinctly ad- visable, before using it, to let the air pass through in order to decom- pose it, or still better, to let it freeze. When using waste lime one should convince oneself first of all, by a simple experiment, that no injurious sec- ondary action can take place. According to Hoffman’s experiments’, it 1 Mitteilungen der Deutsch. Landwirstchafts-Ges, 1905, p. 367. 238 should also be taken into consideration that the more lime used, the less should fertilizing with potassium be neglected. In using stable manure, it is well to put the lime in the soil sometime before the manure is added. Bone meal should be avoided on soils containing lime. In the same way, it is not ad- visable to use ammonia and ammonia superphosphates together with lime. Pulverized quick lime should be used on binding, clayey soils ; lump or slaked lime on better loam soils. In regard to the need of lime by the different plants, Hoffmann states that the Leguminoseae in general are distinguished as the most responsive to applications of lime, but that the Lupines and Serradella may be con- sidered as hostile to lime and sweet peas also do not like the direct use of lime or marl. In the use of marl also, the lime is the most active principle and hence it follows that a clayey soil, rich in humus, bears marling better than a poor sandy soil which in turn can be more benefited by a clay marl than by a lime or sand marl. The sometimes dreaded “impoverishment” from the use of marl will take place only if fertilizing with stable manure is delayed. The last is indispensable for all soils and especially for heavy ones in keeping the fields productive. Nosmineral fertilizer can replace stable manure. The influence exerted by the lime contained in marl upon decomposition of the humus substances is illustrated very clearly by Petersen’st experi- ments. He determined the amount of carbon dioxid produced in different soils by the process of decomposition with and without the addition of cal- cium carbonate. In using a heavy clay soil, known to be perfectly sterile, with 1.98 per cent. humus and 36 per cent. of its water holding capacity in water content, he obtained in 16 days 0.07 per cent. of the weight of the dry soil in carbon dioxid. On the other hand, the same soil under the same con- ditions with the addition of ™% per cent. of calcium carbonate, mixed in the clay as marl, yielded 0.20 per cent. carbon dioxid, or per liter of dry soil, without addition of lime, 0.9153 g.; per liter of dry soil, with addition of % per cent. lime, 2.6167 g. A leaf mould with strongly acid reaction consisting of 58 per cent. humus and 30 per cent. of the absorptive capacity in temporary water con- tent, yielded after 16 days, without and with the addition of T per cent. cal- cium carbonate (when the earth still gave an acid reaction) : per liter of dry soil, without the lime addition, 0.8911 g. CO,; per liter of dry soil, with the addition of I per cent. calcium carbonate, 3.386 g. CO,. With the addition of 3 per cent. calcium carbonate, the soil yielded 5.3470 g. carbon dioxid, while the series of check experiments, free from lime, produced only 0.9664 g. CO,. The addition of the lime, therefore, had caused 3 to 4 times as great a production of carbon dioxid, i. e., humus de- composition, as in the soil in an unmarled condition. Heiden, in Pommritz, summarizes thus the effect from the use of marl: The chemical action arises primarily from its content of calcium carbonate 1 Jahresbericht f. Agrik. 1870-72. Landwirtsch. Versuchsstationen, Vol. 13, p. 155, A359 and consists in the hastened decomposition of the organic elements of the soil, in the combining of the free acids so injurious to plant growth, in the conversion of ferrous oxid into ferric oxid, and in bringing about the ab- sorption of the basic nutritive substances by the soil. The bases are held in the soil as hydrated silicates and as the salts of humic acid. In the absorp- tion of the bases by the humus body, these must be present combined with carbon dioxid. The lime promotes the formation of carbonates. Further, the mineral elements of the soil are decomposed, whereby the basic nutritive substances are freed and made accessible to the plant. Every marl does not suit every soil,—clay soils, where possible, must have a lime or sand marl. Aside from these indirect advantages, the direct effect of the use of marl is shown in the addition of potassium, soluble silicic acid, magnesia and phosphoric acid, which, together with lime, are present in every marl. A few words should be added here as to the use of plaster or gypsum. Franklin’s words,—‘“This has been plastered,” are well-known. He wrote this in plaster on a clover field in order to recommend to his countrymen the process which had been known with great advantage by the Romans (Knop, Kreislauf des Stoffes) and the Greeks. According to Knop’s experi- ments and those of Déhérain and Liebig, a solution of plaster in soils con- taining absorbed potassium, frees it in the form of sulfate, while the lime it- self is precipitated. The method of spreading the plaster on clover plants freshly covered with dew or rain, recommended by experience, is found to be advantageous, since a solution of plaster is formed on the moist plants; dripping from them, it acts at once in the immediate vicinity of the roots. It thus rapidly becomes of advantage to the bacterial flora, for Pichard’s' researches and those of others show that plaster and other sulfates (potas- sium and sodium) exercise a most favorable influence on the process of nitrification. Plaster should be used in an unburned state and indeed for clover and lupines from 2 to 5 centner per acre in the spring. Although the influence of calcium hydrate or carbonate, favoring de- composition, was discussed above, it must still be emphasized, that, as shown by Wollny’s? work, this is only of value when the substance is already de- composed and contains humic acid, while the addition of calcium on unde- composed organic substances rather hinders decomposition. This is especially true for calcium sulfate (gypsum) which comes under consideration as a conservation material for animal manure. In a mixture of quartz sand (300 g.), powdered peat (5 g.), and 60 ccm. water, Wollny* found Volumes CO, in 1000 Volumes Soil air— without the addition of gypsum with the addition of gypsum eee Sate ree Ae cheers oie 0.05 g. Ont gs: GO} 3.194 3.029 2agte 1 Annales agronomiques X, p. 302. 2 Wollny, E., Die Zersetzung der organischen Stoffe ete. Heidelberg, Carl Winter, 1897, pp. 133 ff. 3 Journal f. Landwirtschaft, 1886, p. 263. 240 The addition of the plaster had accordingly reduced the loss in organic substances and also in nitrogen; i. e., had exercised an arresting influence on decomposition. The use of calcium compounds as a remedy against dis- eases, in which an excess of nitrogen comes under consideration, will be discussed under the individual cases of disease. 2. THE DISADVANTAGES GF, MOOR esos: THE ACIDS IN THE SOIL. Ramann' explains as moors,—the formation of more moist regions in temperate zones, in which soils poor in nutritive substances, with an acid reaction, are covered with dwarfed bushes, grasses, mosses and peat-moss (sphagnum), and also lichens. The humic acids* act freely here, and cause the acid reaction of the soil. Acids are formed by the decomposition of the organic substances in the soil to which fungi as well as bacteria surely contribute a share (Cepha- losporium, Trichoderma, etc., according to Koning*). Formic acid, acetic acid, butyric acid, etc., are produced which decompose rapidly in well aerated soils. Besides these, however, the humic substances also form the still little known crenic acid with its salts (crenates) which, widely dis- tributed in soils and water, form a yellow, strongly acid solution. drying to an amorphous mass. While its salts with alkalis and alkaline earths are soluble, its ferric oxid remains insoluble. With the entrance of air aprocrenic acid is produced from it, the salts of which are either in- soluble or dissolve with difficulty. A great influence on the weathering and the transportation of the accessible mineral salts may be ascribed to these acids and their compounds*. Raw humus, peat and other soil substances with a strong acid reaction lose only a part of their acids even after lying sometime exposed to the air. Since even well aerated forest soil often shows an acid reaction, it may be concluded that scant oxidation either does not cause the production of the soil acids, or only at times produces them. We must consider here also the work of definite bacteria in this acid for- mation. Free acids are often absent in good soils, but poorer moor soils are frequently rich in them and become even poorer because extensive leaching and weathering processes constantly take place, due to the free acids. 1 Ramann, Bodenkunde, 2nd. Edition. Jul. Springer. 1905. 2 Koning, Arch. néerland. sc. ex. et nat. 1902 II, .9, p. 34. 3 Ramann, loc. cit. p. 144. * In the light of recent investigations on the nature of the organic matter of the soil it seems that we must revise some of the older terminology. The term “humic acids” is rather to be regarded as a loose generic term applicable to a group of organic compounds found in the soil.—Vide:— Mulder, The Chemistry of Vegetable and Animal Physiology, trans. by From- berg, 1849. Schreiner, O. and Shorey, E. C., Bulletins 53, 74, and 88, Bureau of Soils, U. S. Department of Agriculture. Jodidi, S. L. Jour. Amer. Chem. Soc. 34: 94. 1912; Jour. Franklin Inst. 175: 245. 1913. (Translator’s note) 24I In regard to the sensitiveness of our cultivated plants to free acids, Ramann cites Maxwell’s' experiments with 1-10 and 1-50 per cent. solutions af citric acid. He found that all the Cruciferae were quickly destroyed, the Papilionaceae more slowly. Grain suffered greatly, only the pearl millet and maize could withstand it. Tolf made discoveries in regard to humic acids, according te which seedlings suffer in acid moor soils. In the acid moor, the diffusion of the salt solutions is sharply arrested. According to Reinitzer and Nikitinsk, pure humic acids are unsuitable for the nutrition of bacteria and fungi. On the other hand, most of the higher plants can endure a moderate amount of these acids. We discover from our cultures of Ericas, Azaleas, Rhododendrons and other Ericaceae in moor soil that a number of plants indeed seem directly adapted to acid soils. The dark colored humus parts consist preponderately of Humin and humic acid (Ulmin, according to Mulder). The humus substance must be considered as a mixture of closely related bodies with and without nitrogen, which can be separated into two groups according to their behavior with al- kalis. The brown humin substances, insoluble in the most diverse solvents. swell up in alkaline liquids and pass gradually over into humic acids. The humic acids (their chemical composition is insufficiently known), containing possibly 59 to 63 per cent. C, 4.4 to 4.6 per cent. H. and 35 to 36 per cent. O, are easily dissolved in alkalis and are re-precipitated from their solutions by stronger mineral acids. If they are withdrawn from acid soils (moor soils) with alkalis or ammonia and precipitated with hydrochloric acid, a voluminous, jelly-like substance is obtain which, in drying, forms a brown or black amorphous mass. The humic acids are separated from their solution, by freezing, in the form of a dark colored powder, which gradually passes over again into solution. Ramann emphasizes the fact that humic acids are * somewhat soluble in pure water, but not in water containing salts. The salts of the alkalis and of ammonia with humic acids are soluble in water, but not those of the alkaline earths (calcium and magnesium). Yet the latter also seems to become soluble with an excess of acids. Calcium humate will decompose quickly into calcium carbonate which will combine into new masses of humic acids. On an average, the nitrogen content of humus substances is greater in dry regions than in moist ones. By the advancing decomposition, the nitro- gen, which in organic combinations is accessible to plants with difficulty, is carried over into compounds easily absorbed. Raw Humus. Humus is beneficial and indispensible only where, in pure deposits or mixed with the mineral skeleton of the soil, it is exposed to constant aeration and to sufficient moisture. Its chief action on plant growth does not lie in its nutrient content or in the carbon dioxid formed by its decomposition of minerals, but in its physical properties. "1 Journ. Amer. Chem. Soc. 1898, 20, p. 103. 242 If humus is mixed with dense soils, they are loosened and made warmer and more easily worked. In sandy soils the humus acts as a binder and in- creases the water capacity, whereby the fluctuations in temperature become less marked. These favorable peculiarities, which arise from the mixing with mineral elements in the soil, disappear as soon as the humus is de- posited on the soil in impervious layers, i. e., is not broken up by abundant decomposition and the micro-organisms. In compact humus layers, the con- tent in free acids is almost always greater. The forest soils, which are most rapidly decomposed and worked up, are the best. In warm climates the work progresses very quickly of itself. With a favorable humus decomposition, we find that in forest soils the porous forest débris, which forms the layers of litter, is not so thick and merges gradually into a friable, strongly decomposed, structureless humus layer. If in any region the factors contributing to decomposition are ab- sent, these layers of litter are retained, settle only gradually and become a firm, fibrous humus mass, which is deposited on the subsoil and remains more or less sharply separated from it. Such cases may be observed in poor sandy soils, especially those containing meadow ore. This process, in which therefore the organic substance acquires no earthy composition, will occur everywhere where conditions unfavorable to decomposition exist,—as, for example, when the air is excluded by water, or conversely, with too great drought in the hot seasons or in places exposed to constant strong winds. Our forest tracts, where heather (Calluna vulgaris), cranberries and huckleberries (Vaccinium) the pteris and aspidium brakes and the cushion- forming mosses grow, are most inclined to the formation of such fibrous and but slightly earthy humus layers, the undecomposed elements of which are - deposited in dense masses on the soil and in this way form the so-called “raw-humus.” The upper layer of such raw-humus deposits still shows the interwoven structure of the plant débris, the lower layer, in which the plant parts are but slightly distinguishable from one another, has a fibrous dark humus substance interwoven with roots. In moist beech, pine and spruce tracts, such raw humus may become peat-like. Ramann (loc. cit. p. 162) states as his opinion of the change in the soil beneath a covering of raw humus,—that, besides the exclusion of air, the humic acids especially form the injurious factors. These act on the un- weathered silicate, decomposing it energetically, bringing into solution al- kalis and alkaline earths and, since at the same time the amount of acid solutions absorbed in the soil is slight, Jeaches the soil, i.e., the soluble sub- stances are carried down to greater depths. If raw humus lies on sandy soils, the grains of the uppermost layer appear to be strongly bleached and milk-white, the intermixed silicate rock is greatly weathered and usually transformed into white kaolin, The humus admixture still richly present on the upper surface decreases more and more from the top downwards so that 243 the soil becomes light gray in color and, because of this color, is called gray or lead sand. Below this light colored layer is found, sharply separated from it, a yellow to brownish looking soil, the deeper layers of which gradually be- come lighter. Here, the sand grains show mixtures of ferric-oxid or ferric hydrate. Then comes the white raw sand, still but little affected by weather- ing. The uppermost humus soil layer is found to be most weathered and the layer most impoverished by leaching. If the leaching of such an upper soil layer, under the influence of the raw humus deposited on it, be carried to a given stage, the action of the salts in the soil on the soluble humic acid must cease, the salts then remain in solution and can penetrate to the lower layers of the soil. If they come in contact here with soluble salts, they are precipi- tated and coat the separate soil grains with a structureless layer of organic substances. Under the microscope, I found the sand grains covered with brown, chart-like etchings. If this process keeps up, the precipitated or- ganic substances finally cement the separate sand grains into compacted layers below the lead sand,—meadow-ore has been produced. “MEapow-OReE. According to Ramann’s explanation of the production of meadow-ore, given in the previous section, this is a humus sand stone. It occurs in var- ious forms and first of all as “Branderde” or “Orterde,’ which has a white easily pulverized form and shows a large content of organic substances. This is formed in rich soils which are but little changed unfavorably. The real swamp ore is a firm, stone-like, hard mass, deposited on easily pulver- ized or loose soil layers, with a medium content of organic substances and a brown to black color. This is the form most widely distributed in North Germany (Liineburger moor). Besides this, there is a lighter brown swamp-ore which is very firm and tough and holds but small amounts of organic substances. This is the hardest form, offering the greatest resistance to a working of the soil and frequently occurring in great thickness. In judging the processes of leaching, an analysis taken by Graebner* from Ramann’s? work may be useful. The swamp ore soil in the Main Forestry District Hohenbriick in Pomerania contained in its different layers :— (a) Lead sand, which was 15 to 20 cm. thick and contained 1.05 per cent. of organic substances’. Soluble in Residue insoluble in Hydrochloric acid. Hydrochloric acid. POLASGIUTAN cussed ee terete ett t 0.0076 per cent. of the soil 0.618 CSOGTR ee ek Ma Mae en a ssi eyy ORC IIL Ata ea 0.167 ) CHUN set Nee? Nae arcs wae oe OMCs tee 0.060 Mine aesia ina ctimn cote at, sao MOOZO PA eR eM Urs: Abe 0.020 GManeanous*omid i525 Ses Grooe2uty ain eh. a 0.060 ) Pierre ;Omide aot Bsc tstyul ssid sie COOOL etic Sherr eine 0.450 IMAI, OXIA: 5 5 0% eco eich GO26S ryt i ch ae 0.650 Phosphoric acid wo 5 wera ete ae GOOGOM es. 4) te eae 0.043 Total content except silicic acid.0.1645 2.068 1 Paul Graebner, Handbuch der Heidekultur. Leipzig, Wilh. Engelmann. 1904, p. 194. 2 Die Waldstreu, Berlin, 1890, p. 30. 3 Ramann in his “Bodenkunde” 1905, p. 166, gives the same analysis without the elements enclosed in parantheses. 244 (b) Swamp ore, 5 to 8 cm. thick with 7.28 per cent. of organic sub- stances: Soluble in Residue insoluble in Hydrochloric acid. Hydrochloric acid. Pofassiimayes) monster 0.0178 per cent. of the soil 0.754 (Sodium evn. ole cae aoe 0.0033 TREN 0.360 ) Galician Sens estar uae ence GlOMOA ites eo ay see 0.170 Maenesiale cs Oo a kaenoe eens O1OTS7 whe een he ae 0.028 (Maneanousvoxid:. (ae OOO Ae! Pie le seen 0.047 ) PetHiC GiGi. ack. aaa ean Olt 30h na ea ees 0.690 Aulgamnatiia (oxide 7302.52 ene tease Me SOO oe ser eae eet 2.220 Phosphoric acid: :1 vo wee eae ee O2O56 ee te eae ~ 0.042 Total mineral substances except SHICIC CIE: Vets seen ee 2.0744 4.411 (c) The yellowish brown sand underlying the swamp ore: Soluble in Residue insoluble in Hydrochloric acid. Hydrochloric acid. Petassitin huts amaretee . le 0.0085 ‘per cent. of the soil 1.103 ESTO Nib hance ht) Mauna Mame ee este e O23. 5/7 eevee er 0.528) Wallin eno caer sia able ren OL0254 iis Sea 0.225 Whalealesia one etere os S78. 8 Sean O-.040Iks “255, am aeons 0.004 (Moaneanotisioxid, x 01). cree G20G08e sere eae 0.020) eT GER OSM gg siias Cie as ttate th ete OLA AG ie, ene 0.760 (ALUM CORA A. ade ae O4CO0O™ ls eee tine 3.210 Phosphoric acid is res c..c2h, 4 sae O:0281- 1 arate ey ees 0.043 Total mineral substances except SINGH y-ACId pices tae pee 0.8750 5-959 We perceive from the above figures that, by leaching, the lead sand has not only lost in soluble substances, but that the greatest part of all the rock débris containing nutritive substances has been decomposed by weathering and being washed deeper down. It is therefore a fact that cer- tain soil layers in forests and in open moors (usually formed from such soil layers) become impoverished. This is very significant agriculturally if the impoverishment exceeds the supply of nutriment furnished by weathering and the annual rain fall. Meadow ore must be distinguished fain the real swamp ore; the for- mer is insoluble in an acid solution, such as hydrochloric acid, while the swamp ore is abundantly dissolved. Especially in humus moor soils, where the deposition of raw humus leads to the formation of swamp ore, do two chief injurious factors come under consideration :—the lack of oxygen due to the density of the soil and the content in humic acids. The processes taking place, with an exclusion of oxygen, have been considered in another place (for example, p. 99). We have here to take only the humic acids under consideration. Graebner pays the desired attention to this point’. Continuing Wolf’s? investigations on Loc cit, “p. 226: 2 Tagebl. Naturf, Vers., Leipzig, 1872 245 the wilting of the leaves and their ultimate death, resulting from the de- tention of the plant roots in water excessively charged with carbon dioxid, Graebner cites Maxwell’s experiments! with citric acid and those of Tolf and Blank with humic acids, all of which lead to similar results. This is the place to record Ramann’s statement as to the cause of retarded diffusion in acid soils. Either the colloidal composition of the moor-substances can re- duce the capacity for diffusion and the colloidal substances are precipitated by neutralization with lime, or some direct action of the humic acids is present. If one thinks of the discoveries showing the influence exerted by slight acid increases on the protoplasm”, whereby its currents are arrested, one must consider the direct action of the acid to be of the chief importance. Special proof already exists of the retarding of transpiration by acids (tar- faric, oxalic, nitric and carbonic acids, etc.) and its hastening by alkalis (potassium, sodium, ammonia)*. It can therefore be said, with Schimper, that plants in a strongly acid soil will suffer from physiological drought even in the presence of abundant water. To this must be added that the great power of humus to retain water makes the mechanical withdrawal of the water from the soil particles much more difficult for the roots than if in sandy soil. Plants are found to wilt in peaty soil or loam with a percentage of water sufficient to keep them perfectly fresh in sandy soils, as Sachs” experiment has already shown. All these injuries due to the soil find expression most of all in the culti- vation of pines, which subject Graebner® has treated with especial thorough- ness. He found in young pine plantations, which had grown tolerably well for some years, that the shoots formed in May at first developed normally, but, with the appearance of the summer drought, became grayish green in color. If the dry period continued, the shoots begin to curl, the needles of the previous year became blunt and brown and in many cases the little trees dried up in a few weeks. By digging in the soil, it was found that swamp ore had been formed below the roots or even around the still rather slender ones. To supplement his description, Graebner pictures in the figures here reproduced root development on swamp ore soils. We see in figure 29, that the strongest and longest roots are spread out not far below the surface of the soil and parallel to it, so that its nutrition must take place through the raw humus and the lead sand, which is poor in nutritive substances. Since root development is greater in solutions poor in nutritive substances than in concentrated solutions, this results in a wide reaching out of the root branches, which, in the present case, according to Graebner, seem several meters long and but little branched. The aérial axis, however, is scarcely a Journ. Ann. Chem. Soc. XX (1898) p. 103. Pfeffer, Pflanzenphysiologie II Vol. 1904, p. 798. Pfeffer, Pflanzenphysiologie I Vol. p. 2381. Sachs, Handb. d. Exp.-Physiol. Leipzig, 1865, p. 173. Graebner, R., Handbuch der Heidekultur, Leipzig, 1904, W. Engelmann, p. 231. aor ON 246 meter high. Poverty in nutritive substances in combination with the lack of moisture, easily becoming great in lead sand, are the causes of an ultimate blighting at the tops. Figure 30 shows the root growth of an oak. The oak was planted after the layer of swamp ore had been broken through artificially. But this layer of swamp ore had later re-united and the portion of the root in g, nearly shut away from an air supply, had practically stopped growing. No mycor- rhiza, or scarcely any, could be found on this part of the root. Graebner attaches the fol- lowing significance to such phenomena. If the swamp ore is deposited below the roots, the earth lying above it © is naturally exposed to great fluctuations in moisture, and in times of drought becomes so dry that the plants die from a lack of moisture. In cases of this kind, however, the plants forming their roots en- tirely in the lead sand, exhibit a very weak growth, grad- ually making itself evident by short, yellow needles. If the swamp ore, however, lies di- rectly around the roots, which are about as large as knitting needles, and have penetrated in to the better soil, it presses against them, causing knotty swellings. This takes place if the roots reach the better sub- Fig 29. “A meadow ore pine” from the Liine- 1 tl 1 k : : fe burger moor, grown after the formation of the sol through an opening 1n the meadow ore. swamp ore layer. Such me- vy raw humus, 4 lead sand, 0 meadow ore. Below the meadow ore the yellow sand begins. (After Graebner.) chanical constrictions disturb further root growth. The tree is therefore essentially dependent on the roots lying above the swamp ore layer. Growth and vital activity are normal during the spring dampness, but all activity stops if a hot summer dries out the soil. Graebner found the root iips shrivelling, turning to resin or dying entirely. In larger trees, with a renewal of moisture, time and material are necessary for new root growth. This loss in time and substance becomes evident in the growth of the aerial axis and, in combination with the results of the period of drought, causes in great part the weak growth of the moor pines. The plantations improve as soon as the fluctuations of moisture are less extreme. | 247 Usually pines on high moor: soil develop a very crooked form?. Yet the seeds of these crippled pines, after the moor has been drained dry, grow ito erect trunks. Schroter and Kirchner? also state that, on too wet places in the high moor, Pinus montana makes a reduced cripple growth (“Kusseln”), but recovers after the water has been drained from the soil. Our pines form such (‘“Kusseln’’) also on wet meadows. In the cases I have observed, this form of growth was produced by the resinification of the terminal bud of the main shoot, because of insect and fungus injury; there then develops below this bud a number of shoots which remain short (and in part some rosette shoots). Figure 31 shows a pine 48 years old which came from the Lunebur- ger moor and which Dr. Graebner most kindly placed at my disposal. The height of the whole tree,—including the tops and measured from the root neck up, amounted to 74 cm.; the length of the trunk up to the first branch, 39 cm.; the girth of the trunk below the lowermost branch, 8:3 cm.; the average length of the needles, 2 cm. The foliage of the whole tree Fig. 30. An oak from the Liineburger moor planted 1S Veby Sparse: The after the meadow ore had been broken through. : The layer of meadow ore had closed later. needles have remained : y raw humus, 4 layer of sand 20 cm. thick, 0 meadow ore, only on the latest shoots, g yellow sand. (After Graebner.) all the older ones have fallen. The branches are greatly thickened in places and cracked open as a result of injury from frost. The perpendicularly growing tap root is 8 cm. long to its: place of horizontal bending; the largest horizontal root branch, 18 cm. The branch growth is sparse and the branches have sharp angles (k) and often dead tips (a). These sharp angles or bow-like curves (k) arise because the branches and the main trunk have received one- sided, canker-like frost wounds to which correspond an increased wood for- mation and a stretching on the opposite side. Greater frost wounds, exten:l- ing over more than half the circumference of the axis, are found at f and /’. 1 y. Sievers, Ueber die Vererbung von Wuchsfehlern bei Pinus silvestris. Forstl.-naturwiss. Zeitschr. 1898. Part 5. 2 Lebengeschichte der Bliitenpflanzen Mitteleuropas, Part III, 1905. p. 222. 248 In figure 32 f’ on the main trunk is reproduced in natural size, in order tc show that, like “open canker,” the wounded surface consists of many very small, over-growth edges of different years which recede like terraces. In accordance with the paltry branch growth in figure 31, the root is also small; it cannot follow its natural tendency to send its tap root downward a abgestorbene Zweig- spitzen, k scharfwinklig gewach- sene Zweigstelle, k' bogig gekriimmte Pip alietelic. f Frostwunde am Ast- ablauf, f Frostwunde in Form des offnen Krebses mit gezontem Holzkérper, auf die Ortsteinschicht aufgestofseneWurzeln, Fig. 31. A moor pine with flatly extended roots from the Liineburger moor. (Orig.) a dead tips of branches, # parts of the branch which have grown out at sharp angles, %’ parts of the branch curved like bows, / frost wound where the branch leaves the trunk, / frost wound in the form of an open canker with a distinctly limited wood body, # roots which had grown against the layer of meadow ore. perpendicularly (compare figures 5 and 6, p. 95), but must extend its root branches in the upper soil layers and moss cushions. Part of the lowest root branches are partially bent upwards at a sharp angle, probably because they have met with a layer of swamp ore or some similar impenetrable body. 249 In his study of the high moor of Augstumal in the Memel delta, Weber" gives very interesting illustrations of the crippled forms of pines. corresponding to the Pinus silvestris f. turfosa, Willk. Here he describes also the crippled birches, whose roots, like those of the Scotch fir, always show splen- didly developed mycorrhiza. The trunk, usually only a few centimetres thick, is most- ly bent and knarled, and covered below with a seamed bark, a very striking feature in such small trees. To this it should be added that these small birches usually only about 1.5 m. high form a well set top. On an average, the main root penetrates only 15 to 20 cm. in- to the soil, then bends to one side, to run parallel with the surface. The roots, spreading sidewards, attain to 3 to 4 times the length of the trunk. The vegetation on the high moor is best characterized by a specimen of Betula pubescens described by Weber*. The upper trunk, which had white rot at the top, was 1.8 m. high; the wood from which the bark had been removed was possibly 34 mm. in diameter above the root neck and had 51 annual rings, the last eleven of which alto- gether were only 0.9 to 2.6 mm. wide. The little tree was just beginning to become blasted at the top and was overgrown for 30 cm. above the root neck with Sphagnum medium and S. acutifolium. In cultivation, it is not only necessary to break through the swamp ore layer, but also to bring it up to the surface of the soil. In the air, it decomposes to a brown sand, which gradually becomes lighter in color be- cause the organic elements have weathered. Freezing the swamp ore hastens this process greatly. The decomposition usually takes place more quickly when the content in or- ganic substances is higher. Brown colored swamp ore (rich in humus) is usually de- composed in a year; on the other hand, Fig. 32. Canker-like, wounded place on the moor pine. c the (deepest lying) wood centre, t edges of the wound rising like ter- races in which the most recent, 7, are the most rolled back and the old bark, ry, covering it, which is breaking loose in squarrous pieces, zw dying, outer- most edge of the wound, / lichen growths. (Orig.) the light colored (which is poor in humus), only after 2 to 4 years. 1 C. A. Weber Ueber die Vegetation und Entstehung des Hochmoors von Aug- stumal im Memeldelta, ete. Berlin. Paul Parey, 1902, pp. 40 ff. 2 Loe:, cit.. p:, 47. 250 PoISONING OF THE SoIL BY METALLIC SULFUR. In considering factors injurious to plant growth ferric sulfid as pyrites (and rhomboidally crystallized as markasit) must be noticed primarily since it is one of the most widespread precipitates produced in the formation of moors. Ferric sulfid is found less in moors themselves than in the under- lying sand and on the line between the organic deposits and the subsoil. If pyrites weathers, there is produced by oxidation and absorption of water sul- furic ferrous oxid,—ferrous sulfate, copperas, and free sulfuric acid (FeS,+ 70+H,O=—FeSo,+H,SO,). The ferrous sulfate oxidizes with the formation of basic salts to ferric oxid. In the presence of sufficient amounts of calcium carbonate, calcium sulfate (gypsum) is produced. If ferrous carbonate occurs, it passes over into ferric oxid or ferric hydrate with the loss of carbon dioxid and the taking up of oxygen. As is well known, the ferric hydrates cause the yellow to brown color of the soils and are able to absorb gases (carbon dioxid, nit- rogen, etc.) to a very marked degree. Among them is the brown clay iron ore (limonite Fe,[ OH],) which cements together the surrounding sand’. In moor regions, however, the layers containing pyrites are often not oxidized at all; because of the presence of water and the strongly reducing action of the moor substance they cannot obtain any oxygen. The most disasterous effect of the iron sulfid is its inhibition of the com- bining of the bases present in the soil and the free sulfuric acid formed by weathering. As a rule, calcium carbonate is present in the soil, so that gyp- sum can be formed, often alum or magnesium sulfate are also produced. An excess of the last can act injuriously. When experimenting with an exces- sive supply of alum, I found spotted necrosis appearing in barley. However, if the bases are absent, the free sulfuric acid will act directly as a plant poison. If, in improving the soil, the layer containing the pyrites is brought to the surface, the soil will at first remain infertile. ; Minssen* shows that at times the upper layers of the moor also contain iron sulfid. In a sample from Silesia he found 7.286 per’cent. of the dry substance of the surface soil to be sulfuric acid, soluble in water, 3.940 per cent. ferrous sulfate and 3.346 per cent. free sulfuric acid and approximately twice as much in the deeper layers, aside from great masses of still un- weathered iron bisulfid. The top of the sulfate here analyzed was later re- tnoved 62 cm. deep, so that the lower layers richly impregnated with iron sul- fid were laid bare. The oxidation of the pyrites gave such large amounts of compounds injurious to vegetation that any agricultural use of the moor within a conceivable time seemed impossible. Such a case shows the neces- sity for the use of foresight in opening up lowland moors. 1 Ramann, Bodenkunde, 1905, p. 87. 2 se 2 Mitteilungen d. Ver. z. Forderung der Moorkultur im Deutsch. Reich, 1904. Oumke 251 The question as to the injuriousness of the black colored water flowing on to the meadows from the alder bogs of forests has been treated in detail by Klient. In one especial case which gave rise to complaints against the forestry commission, the water coming from the forest was viscid, brown and at times smelled bad. In 100,000 parts, it contained 31.28 parts organic sub- stances (humic acids, etc.) and 17.59 parts mineral substances, among others 7.81 parts calcareous earth, 3.07 parts ferric oxid, etc. The humic acids formed the injurious factor here. In similar cases it depends on the kind of soil overflowed by such bog water. It will be especially injurious if it flows over ferruginous soils or those with a clay subsoil, while a soil rich in lime can more easily withstand overflowing from the alder swamp, such as oc- curs in spring floods, because of the hastened decomposition of the humus, peculiar to such a soil. Nevertheless such water should be avoided for irri- gation and back water. The formation of ferruginous sand depends on the precipitation of fer- ric hydrate and iron silicates. Mixtures of ferric hydrates with varying amounts of ferric silicates and phosphates also give the so-called meadow- ore. This combination occurs in moors, standing bodies of water and other places, where water containing iron comes in contact with the air, together with the co-operation of bacteria (iron bacteria according to Winogradsk1)’. One is inclined of late to lay stress on the co-operation of the micro-organ- isms’. SUSCEPTIBILITY TO FROST OF Moor VEGETATION. In moor soils which have been brought under cultivation, their especial sensitiveness to frost as compared with other kinds of soil has been proved by repeated experiments. In this, important differences are found if the moor soil has a sandy covering or if it is mixed with sand. Wollny* found in his experiments that the latter is more fertile than the former, in which the ground water was higher. Instead of the sand, a covering with clay has also been proved to be beneficial. In meadow cultivation when too much water has been removed, Fleischer’? recommends covering with sand, rich in feldspar, or loam, or clay to avoid too great drying out. Jungner® gives fur- ther examples from the province of Posen. In them moor fields which had not been covered with soil containing clay, showed also a second total freez- 1 Klien, Die nachteilige EHinwirkung des aus Eller-Briichen und Torfmooren kommenden schwarzen Wassers auf die Wiesen. K6nigsberger land- und forst- wirtschaftliche Zeitung 1879, No. 28; cit. in Biedermann’s Centralbl. f. Agrik- Chemie, 1880, p. 568. 2 Winogradski, Ueber Eisenbakterien. Bot. Zeit. 1888, p. 260. 3 E. Roth, Die Moore der Schweiz, unter Beriicksichtigung der gesamten Moor- frage. Leopoldina, 1905, No. 3, p. 34. 4 Wollny, Untersuchungen iiber die Beeinflussung der physikalischen EHigen- schaften des Moorbodens durch Mischung und Bedeckung mit Sand. II. Mitteil. Forsch. a. d. Geb. d. Agrik.-Physik. 20, 1297-1898, p. 187. 5 Fleischer, M., Ueber die zweckmifsige Behandlung von Moorwiesen; cit. Biederm. Centralbl. f. Agrik.-Chemie, 1888, p. 137. 6 Zweiter Jahresber. d. Sond.-Aussch. f. Pflanzenschutz fiir 1904. Arbeit. d. Deutsch. Landw.-Ges, Part 107, Berlin, 1905, p. 61. 252 ing back of potatoes and pasturage, while those which had been covered had suffered no especial injury. This discovery indicates that we have to look for the chief period of: injury in spring, so far as frost phenomena in moor soils are concerned. In cultivating trees this becomes clear, if we consider that the humus soils in cold seasons usually contain an excess of moisture. The fine pored humus, saturated with water, will cool more slowly in the fall than do soils less rich in water, but will warm up much more slowly in the spring. However, the longer the roots are in a warm location, the longer they remain active and the more water will be forced up into the aérial axes. Trees growing poorly on moor soil with its diluted nutrient solutions start the winter with a large water content in their tissues. The more water the tissues contain and the less cytoplasm, the more susceptible are they to frost, no matter whether the effects of winter or spring frosts are concerned. Hence the frequent and great injury from frost in moor pines, as is shown in the example from the Lutneburger moor. For short-lived field plants the most disasterous are the spring frosts which are produced in rays of cold. This may be easily recognized from the fact that the phenomena of discoloration produced on the leaves and stems by the cold are abruptly cut off, if such a part of the plant is partially cover- ed by overlying leaves. It is now pertinent to ask when cold, due to radiation, will be greatest and how much of it is due to evaporation. If both factors become effective to a high degree, the air layers close above the surface of the soil will be noticeably colder than the average temperature. Polis has proved such a lowering of the temperature of the air layers above a covering of snow. This will be the greater, the less the movement of the air. Hence May frosts in still, clear nights. The moor soils and those bordering on moors with their wealth of water will evaporate strongly in the early spring when the soil and subsoil have not been warmed through, even if, as cultivated land, they have been mixed with sand and accordingly more cooled down. Evaporation will also be still more increased by the dark color of the soil, as Wollny’s? experi- ments show. Covering with a layer of sand from 6 to to cm. deep acts as a preventive. Then but little water can reach the sand from the humus layer and, correspondingly, only small amounts will,be evaporated. For the same reason the dead layer also acts as a protection against drought. One dis- advantage of the sand covering is found when fine, surface-rooting grasses, are sown which are easily stunted in sand, poor in nutrition’. If the cultivation of fruit trees on moor soils is involved, the following may be recommended for protection against frost: (1) The planting of trees on the west and southwest side of the orchard, in order to modify the temperature differences in spring. The bark cracks almost without ex- 1 Meteorologische Zeitschr. 1896, Part I. 2 Blatter fiir Zuckerrtibenbau, 1899, No. 9. 3 Mitteil. d. Ver. z. Férd. d. Moorkultur, 1895, Nos. 5 and 6. 253 ception on the sides turned towards these points of the compass and the nor- mal phenomena of loosening bark scales (for example, on plane trees) also begin earlier and to a greater extent on those sides of the trees. (2) A strong liming and supply of Thomas slag with a sufficient provision of other nutritive substances. (3) Above all, however, those varieties of fruit should be chosen, which endure moor soil. Huntemann! recommends the common house plum, from practical experience. Of apples, the following have stood the test: Bosbook’s Beauty, Golden noble, Double pigeon, White winter apple, Orleans, Parkers Pippin, Purple red Cousinot. The winter Yellow Pearmain, Gravenstein, Prince and Alant apple should not be planted, since they are too susceptible to frost and also to canker. According to the experiences of Mr. Klitzing, a nurseryman, the following apple var- ieties are adapted to cultivation on moor soils,—red Eiser apple, Burchardt’s Reinette, and Cludius’ Autumn apple. Of pears, he recommends Charneux Delicious, St. Germain and New Poiteau. If cherries are tried at all, sour varieties should be chosen rather than sweet ones. THE USEFULNESS OF THE SPRUCE. In considering forest plantations on moist soil, we only reiterate our opinion that it is a mistake to plant pines so extensively as is now done. The example cited on p. 248 from the Liineburger moor shows clearly enough what disadvantages arise. If they are not so distinctly noticeable in other places and especially if frost injuries do not appear so sharply, yet a weaken- ed growth is always induced, which sooner or later becomes evident. For the plains in northern Germany we should return to the spruce. We use the term “return,” for Conwentz? has actually proved that often, in moor regions, spruce was the original covering. Even now in Pomerania and Hanover, even on the Litneburger moor, original spruce woods are often still in existence, and the various cases especially studied by Conwentz give excellent indication that the spruce is still found in a developmental stage, resembling the primeval forests, on soils where wide stretches are covered with peat moss and the moisture in usual years makes access to the soil impossible. This opportunity should be taken to consider the /ayering formations of spruces, which at any rate may be found only in forests not touched by for- estration and it is advisable on this account to preserve accounts of especially good examples of increase by means of Jayering. Hence an illustration and description of a spruce family should be given here, which has been obs2rved in the vicinity of the city Krager6é on the south eastern coast of Norway (see Fig. 33). Schiibeler® describes it as follows. The parent trunk, which stands at the foot of a hill, had a height of approximately 9.4 m. and, about 1 Huntemann, Das Erkranken der Obstb’iume auf Moorboden. Mitt. d. Ver. z. Ford. d. Moorkultur. 1898, No. 7. 2 Conwentz, H., Die Fichte im norddeutschen Flachland. Berichte d. Deutsch. Bot. Gesellschaft 1905, Part 5, p. 220. 3 Schiibeler, F. C., Die Pflanzenwelt Norwegens. Christiania 1873-75, p. 164. 254 6.6 cm. from the ground, a circumference of 94 cm. Ata height of 31 to 36 cm. three branches left the main trunk, and took root in several places. At a distance of 1.6 to 2.5 m. from the present trunk, six regular spruces have gradually developed with a height of 2.5 to 4.7 m. Fig. 33. A spruce family produced by natural layering. Three of the branches at the base of the trunk have rooted again in several places and their buds have there developed into secondary trunks. (After Schiibeler.) The spruce stands by itself in its easy formation of adventitious buds, giving rise to gnarls, and in the ability of parts of its aérial axis to form roots quickly. To be sure Schtibeler (loc. cit. p. 163) has also observed rooting in low branches of Juniperus and also in Taxus baccata, which have been bent to the earth, and certainly such conditions will occur also in other conifers which grow well from cuttings. But cases of this kind will always remain isolated. 255 The capacity for increase, explained here by means of the one example, has a greater significance in moor regions, where the spruce will have to be grown as the only possible means of forestration. Only very few varieties of conifers possess this facility for forming layers and developing new regular top growth from lateral sprouts. Gar- deners make abundant use of this peculiarity in propagating young individ- uals from cuttings. In other conifers, cuttings from the lateral branches retain the structure of laterals and do not form handsome trunks. The Fig. 34. Oak from Rogau (Upper Silesia) with a formation of sinkers. (Orig.) genus Araucaria also has a great tendency to form head shoots and this is often shown in individual lateral branches, which remain on the parent plant, when the top shoot has been lost. In connection with this layering formation of the spruce, occurring on damp soils, we give in figure 34 the sketch of a case of root formation from a branch of an oak, which has been observed only once. In the 80’s of the last century, I had an opportunity in the castle park at Rogau (Upper Silesia) of seeing the very hollow trunk of an old oak which stood on a low lying meadow, liable to be overflowed by the Oder at flood time. The tree 256 had already lost most of its leaves on the lower branches. The upper parts of the two lowest branches, probably at some time bent down intentionally, lay deep in the earth, but their tips had been turned upward. At the point where the branch was bent (at the right in the figure) a strong root was traceable which might have been produced when the still young branch tip was covered with silt by the first floods. The increased nutrition, produced by this root, showed itself in the development of a considerable number of younger shoots, resembling an independent bushy growth. I noticed noth- ing especial in the vigorous spruce plantations standing at some distance. CHANGES IN Moor Sort THROUGH CULTIVATION. One must determine finally how far the injurious factors of humus soil show in cultivation and what changes it undergoes with cultivation. “Sanding” has been discussed already. Fertilizing comes next under con- sideration, since the nutriment content especially in highland moors is so scanty that only plants needing little nutriment and highly resistant to humic acids thrive there (Sphagnum, Eriphorum, many Carex varieties, Calluna, etc.). All fertilizers must act, first of all, by increasing those micro- organisms which can decompose the soil, since in soils containing humic acid, the bacterial flora is very scanty. Fabricius and v. Feilitzen gained much information on the methods to be used in increasing the bacterial flora of moor soils. Stalstrom? had already determined that draining the water from moor soil, very poor in bacteria, naturally will increase the number of organisms. ‘This is especially significant for highland moors, since they have not nearly as many bacteria as the lowland moors ;— a fact related to the scanty nitrogen content of the highlands. Moor soil mixed, with clay or im- proved by fertilizing, has a higher bacterial content. The bacterial flora re- mains almost exclusively in the upper soil layer, 15 to 25 cm. thick. Fab- ricius and vy. Feilitzen also tested the moisture content in the upper soil layer and found that, in uncultivated highland moors, this fell only from 90 to 87 per cent. by draining, while, on the other hand, it could fall to about 64 per cent. with other cultural measures. These consisted in mixing the friable soil with sand, with the result that vegetation of a different character de- veloped. The soil temperature was lowest on the virgin moor. Simple draining exerted but little influence (-+0.3°C.), but cultivation gave a per- manent increase of almost 2°C. In regard to the chemical composition, it was found, as was to be expected, that the calcium content was very small in natural highland moors and the nitrogen content equally scanty, while in the lowland moors the latter was found to be satisfactory. The disappear- ance of the humic acids through cultivation is very interesting. In the Z 1 Fabricus, O., and Hjalmar von Feilitzen. Ueber den Gehalt an Bakterien in jungfraulichem und kultiviertem Hochmoorboden auf dem Versuchsfelde des Schwedischen Moorkulturvereins bei Flahult. Centralbl. f. Bakteriologie ete. II Section, Vol. XIV, p. 161. 1905. 2 Om lerslagningens betydelse. Finska Mosskulturféreningens arsbok. 1898. p. 44. 257 natural highland moor the content amounted to more than 2 per cent. and through sanding, liming, and fertilizing became reduced to possibly 0.3 per cent. These same investigators found the bacterial flora only sparsely de- veloped, as a result of the acid soil in the highland moor, and also but little increased by draining. On the other hand, a great increase was found after sanding, liming and fertilizing together with the necessary attendant work- ing of the soil. Sand introduced new bacteria, stable manure furnished rich nutriment of such a kind that the bacterial content become as great as in a lowland moor under the same cultural conditions. In both the bacterial con- tent increases and falls directly with the soil temperature. The experiences of practical workers disagree greatly as to the use of stable manure. In many places there has been failure. But, on the other hand, reports are found, which determine a very beneficial effect from stable manure even on moors with a large nitrogen content, as Count Schwerin reports’. This contradiction can be explained as follows. Even in moors, which contain nitrogen in excess, fertilizing with stable manure can act very bene- ficially if the moor is but little decomposed, the nitrogen in it therefore being probably still in a form not easily taken up (for example in organic com- pounds). On cultivated moors, however, the yields after fertilization with manure are actually poor and the weeds grow in excessive quantities because an excess of nitrogen probably makes itself felt, due to the addition of ma- nure without the sufficient counterbalance of a phosphate and calcium supply. Potassium is a factor primarily involved in the cultivation of moors. This holds good also for moor-meadows, on which, however, a good hay harvest, according to M. Fleicher?, requires the addition of phosphoric acid (Thomas slag) besides potassium. (In this connection, he warns against over-fertilizing if the ground water level does not lie deeper than 20 to 40 cm.). The form in which the potassium is given may also be determinative in the majority of cases, for Tacke* obtained the best results for potatoes with potassium chlorid. While the tubers contained 17.67 per cent. starch without fertilizing and 17.02 per cent. when fertilized with kainit, and only 16.48 per cent. with karnallite, they contained 18.02 per cent. with the ad- dition of potassium chlorid. The fertilizers were added in the fall; spring fertilizing reduced the quantity and quality of the tubers. Hensele* found in his potato cultural experiments that kainit on meadow moor soils considerably repressed the starch content of the potatoes. In comparative cultures on mineral and moor soils, the yields from the for- mer were larger and the starch content of the moor potatoes never equaled that of the tubers from a mineral soil or that of the seed. 1 Mitt. d. Ver. z. Ford. d. Moorkultur, 1895, Part 6. 2 Milchzeitung 1887, No. 8. 3 Mitt. d. Ver. z. Ford d. Moorkulture 1895, No. 6. 4 Hensele, J. A., Bericht der Moorkulturstation, ‘“Erdinger Moos,’ 1900-01. Cen- tralbl. f. Agrik.-Chemie, 1903, Part 3. 258 In regard to the injuriousness of spring fertilizing, reference should be made to the reports of the General Assembly of the Society for the Advance- ment of the Cultivation of Moors'. Here it is especially emphasized, that kainit and Thomas slag must be scattered in the fall because spring fertiliz- ing reduces the sugar and starch content in vegetables which require hoeing. For Thomas slag, the fall fertilizing is said also to be more beneficial because the acid of the moor can then act as a solvent for a longer time. Chili saltpetre in cultural experiments had decreased the sugar content in edible roots about 1.5 per cent. The preceding crop also seems to have an influence on moor cultures, as is shown by a case from the province of Posen*. There sugar and late grown fodder beets became diseased when grown after mustard. In regard to beet cultivation, Hollrung® arrives at the conclusion that pure moor land should be avoided entirely and even that which has been sanded should be used only with care. ROTTEN BarK. Up to this point we have learned to recognize the characteristic starved types of growth on acid moor soil; these are due not only to the scarcity of nutriment but to moisture conditions as well, either a lack of water arising from the fluctuations in the subsoil, or an excess. These manifest themselves in older treés by a greater formation of bark, when high cushions of heather and moss surround the base of the trunk. These dense cushions store up water, in part retaining that of the moor soil, in part collecting that of the atmosphere, and in this way forming a moist felt constantly growing up higher around the base of the trunk. Such damp cushions decrease the temperature variations necessary for the pushing off of the old bark scales. However, they hinder the supply of air especially and cause the decom- position of those cell layers in the bark scales, which are especially loosely constructed, into a deep brown mass, powdery in a dry condition and slimy when very damp, which is called “rotted bark.” In these are found the brooding places of many animal and vegetable organisms which carry on and hasten decomposition. An investigation of the younger layers under the old bark scales throws light on the production of these rotted masses. One of the pieces of bark furnished by Dr. Graebner from the Litneburger moor was 3.5 cm. thick and differed from equally old, healthy bark in that it could be peeled with un- usual ease into separate layers varying in thickness. The upper surface of the different bark layers, as they fell apart, was rough like a relief map and covered in places with hard, woody processes in the form of broad cones up to 2.5 mm. high and often with crater-like depressions. Such processes, just 1 Berichte der Generalversammlung des Vereins zur Férderung der Moorkultur Jahrg. 1895, p. 123. ° Elfter Jahresber. d. Sonderausschusses f. Pflanzenschutz. Arb. d. Deutsch. Landw. Ges. Part 71, p. 130. a Hollrung, Die verschiedenen Bodenarten und ihre Hignung fiir den Riibenbau. Blatter f. Zuckerriibenbau, 1905, No. 14, p. 217. 259 like the tissue cushions on the various deciduous bark layers, which are like warts and occur in lines, were found always on the inner side of the layer which was being raised up and had exactly the appearance pictured later under the section “Bark Refuse’ in the elm. This section should be con- sulted. The greatest possibility of separation of the lamellae from one another was found where a rotted tissue layer, 1. e., in a condition of humifaction, be- gan to disintegrate and formed a surface of separation. The rotted bark con- sisted of cork cells, as shown on the upper side B in the accompanying cross- section (Fig. 35), while H shows the bark which lay nearer the wood, and rf 2, 2) oem wie a Z = 27-4 wan ! ! ! 4 > = 1, ee J oa Sip) cD Zieh yy us : i Ly a e a To44 Oae BOND yee ena SEE. + al Sy Oty ss g, bees ones ie Dy LD LD DY SQ) Dam ie ine, EM) iy, iiss 23a | ine be tena (; 34 Bip Ih LY ley pp Qre2S xe Dw ; Z 7D : : ‘ LR Wy) () Ly Le ee FRED ae {> 5 ae i ais meiiiitee wal 1) FA eal amy ng ag VES Sei) ali) UP (HY 3 Une, DB bs YS 19D te oS _ W ne VA B Y) s 1 «@ Oy Bot , IK tee SS ps2 D>. 9 see, eh, a <0) al. C{ ry . ry Ra i) 7 if is 1 (e) oe ) \ AN aAy ox Pe ay acs mad ee, CI (2 See CATHIE NS Saeagte: ETT SSE OEE SRR GEE seo LEIS Hp Haracrsey # Fig. 35. Mouldy bark scale of a pine from the Liineburger moor. (Orig.) therefore was younger; rp is corked, firm bark parenchyma while k is the full cork, loose bark parenchyma and ¢ the plate cork. The bark scales were therefore composed of bark parenchyma elements, which advance further and further toward the fresh bark and the cambium. They are separated by layers of sheet cork and become suberized. Besides this, we also find clus- ters of loose cells, which are more abundant the deeper the base of the trunk has stood in the moss. The spongy constitution of the underside of the dif- ferent bark lamellae arises from the morbid luxuriousness of the parenchyma and full-cork masses. As a result of the moisture and the scanty supply of oxygen, these excrescence tissues become slimy and form the rotted bark, which facilitates the separation of the lamellae. 260 The great part which the bark parenchyma, with its abnormal phenom- ena of stretching, plays in the formation of the bark shows that this de- velopment of rotten bark in the moor pine is related to the “bark refuse” of the elm and distinguishes both cases from the actual tan disease (see page 215) in which the formation of full cork has the upper hand, as in the many- layered lenticels. HorTICULTURAL Moor PLANTS. The growers, probably because of their study of the natural habitat of our heather plants, have used for imported Ericaceae the soil in which our Calluna grows splendidly :—i. e., heath moor. The properties of Sphagnum peat, thus ascertained, have made this a desired article in trade. Its ad- vantages consist in its loosening properties. The results of experiments in cultivating Ericaceae led to the mixing of the so-called moor soil with heavier nutritious soils as a loosening substance. In this way, the moor soil has been introduced as a necessary element in soil mixtures for most of the finer horticultural plants. Since no standard was known, however, for a good moor soil, many kinds came into trade, with the growing demand. Some were either over rich in raw humus, or resembled the character of the meadow moor. ‘The dark color of the meadow moor led to the incorrect opinion that a very nutritive earth was present. The results of this mis- conception were very evident. The complaints of gardeners about acid heath soils are almost universal and the degeneration of many favorite plants, such 2s the so-called new Holland, or “Cape plants,” could not be arrested. Where meadow moor was used as an admixture in soils for potted plants, its properties quickly manifested themselves. In a dry condition, this moor soil seems to be easily pulverized, decomposing into a powder, or remaining crusty. When wet, however, it becomes smeary and cements the other particles of soil into dense masses with a poor air content. Since meadow moor heats greatly, the upper layers in the flower pot dry out easily, become lighter colored and suggest to the gardener that the whole ball of soil is dry and should be watered. Here is the danger, jor meadow moor deceives as does no other soil. If such moors be investigated in nature, the smeary condition is found directly under the dusty surface, a few centi- metres deep, since the very binding substance retains the water unusually long. Potted plants are often killed by a lack of oxygen at the roots, even if the humic acids are not taken into consideration. These, however, play a disasterous réle and often cause the injury arising in many cases from the use of loose, fibrous marsh soil. Sphagnum peat is the most beneficial be- cause the leaf is so constructed that it makes a very porous soil, giving rapid moistening and as rapid an aération of the soil in the pot. The excellent re- sults obtained in growing orchids with sphagnum are well known. Good re- sults will only be had with fibrous moor soils, full of fragments of Vaccin- ium and other moor plants and taken from forest soils, if the raw humus is 261 removed and the decomposed layers used ; even an admixture of lime, or still better, of calcium phosphate is advisable. I have mentioned the poor growth of plants in moor earth in a special section, because I am of the opinion that a very considerable number of phe- nomena of disease may be traced to the acids in the soil,—the gardener says that the soil smells sour. Even those specific plants, such as Rhododendron, Azalea, etc., only thrive when, as in their natural habitat, they stand in fibrous earth which is easily aérated. In the moment when a mixture of moor soil with more nutritive solid soils is used for potted plants, we find root-decay, which is indicated by the brown edges of the leaves. I consider the theory of the necessity of an admixture of moor soil in cultivating the majority of our finer potted plants to be erroneous. As far as my experience goes, sand can give incomparably better results as a loosening material. The gardener should work with well decomposed leaf mould or compost earths and add large amounts of sand. If care also is taken to have good pot drainage, there will not be so many complaints about root diseases in the future. SPECKING OF ORCHIDS. A special illustration of the advantages of the use of sphagnum, de- scribed in the previous division, is found in the peculiar black spotted con- dition of the leaves of epiphytic orchids. In our green houses there are many leaf diseases which frequently arise from fungus infection (Gloeo- sporium and Colletotrichum, Phoma, Phyllosticta, etc.). We find many cases however, in which fungi take no part or occur only secondarily and among these an infection should be emphasized especially which may be found in Cattleya, Laelia, Dendrobium and the members of the group of the Vandeae. The course of the disease is explained best by the description of a special case, which, occurring in Phalaenopsis amabilis var. Rimenstadiana’, has re- cently been studied more closely. All except the youngest leaves of plants grown in leaf mould in pierced pots and watered with tap water were spotted yellow to black.. The disease advanced apparently from the older to the younger leaves and manifested itself, in its early stages, by the appearance of irregularly round or oval, pale, translucent spots. These were scattered over the whole leaf, but usually appeared first and most abundantly at the tip. When such leaves were cut off and lost water by evaporation, the spots which became pale at the beginning of the attack, could be felt like warts over the healthy leaf. These conditions changed, however, as the disease ad- vanced, since the yellow spots at once took on a whitish appearance and were depressed like saucers. In’ this it was seen that different adjacent cen- tres of disease coalesced, forming connected, thin surfaces, which finally turned a deep blackish brown and were enclosed like a wall by the healthy tissue. After turning brown, however, the spots did not increase in size. 1 Sorauer, Erkrankung von Phalaenopsis amabilis. Zeitschr, f. Pflanzenkrankh., 1904, Part V. 262 There were also centres of disease, which remained restricted to definite groups of tissues. When one of the browned spots, covered with longitudinal bands due to the darker veining, was cut through, it was found that its paper-like consis- tency was not produced by a possible atrophy of the tissues, resulting from an injury due to insects, or from bacteriosis, but only by the drying together of the mesophyll cells, which have been almost entirely depleted of their contents. The boundary between the dead and the wall-like convex bordering healthy tissue was sharp, with no transitions. The collapsed brown or (mostly) light walled tissue when treated with iodine, showed only iso- lated flakes of cytoplasmic contents together with little drops of a colorless or golden-yellow substance. With the entrance of water, the cell walls, like the folds of an accordion, were raised somewhat from one another, without the cells having been brought to their previous size. In the absolutely dead tissue isolated, colorless, slender mycelial threads were found at times. If glycerine was allowed to act on the fresh sections, which, moreover, also gives a strong acid reaction at the diseased spots and shows no oxydases and peroxydases with guaiak and hydrogen peroxid, large, irregular or usually spherical masses were drawn together in the cell contents. This phe- nomenon was often found in especially sappy tissue, rich in sugar. At the periphery of these masses lay the chloroplasts. In the badly diseased parts these groups of substances could not be found at all, but only numerous very small or somewhat larger drops. Just as little can this contraction of the cell contents into strongly refractive drops be proved in the healthy part of the leaf. We might place it in the list of glucoses because, with the Trom- mer test, they show in places precipitates of cuprous oxid. Further anatomical investigations led to the discovery that, in the var- 1ous yellowish tissue centres, the cell content was used up too strongly, and the mesophyll cells had grown out wider. The diseased place thus became somewhat swollen up over the healthy surface, but at once the diseased tissue, which had lived out its life very rapidly, showed this by the appearance of carotin drops; it collapsed, turned brown, and dried up. This process of drying, however, is limited, in all cases observed as yet, to the Jeaf region characterized in the beginning by the turning yellow. In this the phenome- non is distinguished from fungous infections. Since now enormously in- creased formation of sugar can be proved and the absence of parasites de- termined in the majority of spots, we have under consideration a constitu- tional disease which set in, where the orchids named were cultivated in leaf mould. This cultural method has been especially recommended in the last few years by Belgian and English gardeners and introduced into Germany in part with the use of Flemish leaf mould. After the rapid spread of the dis- ease, the old process of growing the plants in a mixture of sphagnum with bits of moor soil was again followed and the earlier results were again ob- 263 tained. From this it is evident that leaf mould, an extremely favorable sub- stratum for most other plants and in which the orchids named at first grow very well, gradually becomes slimy when copiously watered (especially with water containing algae) and does not let the necessary supply of oxygen reach the roots of the orchids. Much better results have been obtained with the so-called Jadoo fibre, a very porous moss peat saturated with nutritive salts. Yet the result does not justify the increased expense and the old sphagnum culture always proves to be the most advantageous. The modern endeavor of growers to force the orchids to an earlier and more luxuriant development by abundant- ly supplying nutritive substances, high temperatures and great moisture, gives actual good results only for a limited time. Usually a reaction sets in in the over-stimulated plants, which can be prevented only by a dormant period in a relatively cooler, drier place. Cooler, drier sand is also in many cases the best protection against decay from fungus. Klitzing observed a very instructive example in a spot dis- case of Vanda coerulea, called forth by Gloeosporium which is now pretty universal on the continent and in England, as well as even in our country. The statements of the collectors show that this Vanda is found in the Himalayas on Gordonia, which grows in moderately warm, windy habitats. Here, in our conservatories, the plants are cultivated, on an average, more than ror. warmer and kept year in and year out in closed, moist greenhouse air. Nat- urally the plants become more tender on this account and succumb within a few days when artificially infected with Gloeosporium, while, in their native habitat, the fungus is restricted and the plants develop further and increase, despite its presence. CHAPTER EL, UNFAVORABLE CHEMICAL SOIL CONSTITUTION. I. RELATION OF THE Foop STUFFS TO THE SOIL STRUCTURE. A. Sort ApsorPTion RESULTING FROM CHEMICO-PHYSICAL PROCESSES. Injuries to vegetation can take place either because the capital of nu- tritive substances in the soil takes a form quantitatively or qualitatively un- favorable for the nutrition of the plants, or because, with an abundant sup- ply and normal composition of the nutritive substances, the plant’s capacity tor taking them up will be arrested by other factors of growth. Thus, either a lack or an excess of the nutritive substances can make itself felt, or, be- cause of modified conditions of absorption, one single nutritive substance can be present in amounts too scanty or too great for effectiveness, and thus disturb the equilibrium in the organism. This second form of nutritive disturbance will be treated in the following division under the headings, “Lack of moisture and nutritive substances” and “Excess of moisture and nutritive substances.” The consideration of the supply of water in this connection, together with nutritive substances, is justified by the fact that the water not only furnishes these by its decomposition in the plant body, but also, as a transporting medium, causes weak or strong concentrations of the nutrient solutions according to the amount of water present, thus influencing beneficially or disadvantageously the process of nutrition. In view of the constantly changing concentrations, the influence of the water will therefore have to be taken into consideration, when studying the relation of the nutri- tive substances to the soil structure. The soluble salts produced by the decomposition of the minerals or in- troduced by fertilization, serve as a basis for soil absorption. The retention and giving up of the salts, as also their transformations continually taking place in the soil, were thought at first to be predominantly physical processes, while they now, in substance, are considered chemical processes’. In any 1 See Ramann, Bodenkunde, 2nd. Edition, p. 21, Berlin, 1905, Jul. Springer. In the remainder of this section, if other authors are not cited, we rely chiefly on the work here named. 265 case, it is difficult to draw a line between physical combination (absorption) and chemical combination. Absorption becomes of importance, only where large absorptive sur- faces are offered, as in organic substances and certain inorganic ones, to which belong the colloidal silicic acid and the colloidal ferric oxid of the tropical red soils. Those humus substances, capable of being swollen, seem of the greatest significance which are precipitated in soils rich in nutritive substances, such as salt-like compounds, but remain to a great part in solution in impoverished soils. In the absorption of humus substances the first rdle is played by their capacity to take up free bases and their carbonates. The acid humus substances are especially effective for the ammonia found in the soil and for ammonium carbonate and we take advantage of this fact especially when using a peat mulch. Besides colloidal substances, the finely distributed mineral elements should be kept in view as a means of absorption. Of the minerals, how- ever, quartz always and kaolin, when not combined with alkali silicates to form the absorptive double silicate, have no capacity for absorption. The chief bearers are the hydrated silicates, especially the double silicates of aluminum, which, crystallized as Sblites, are found in rocks, and also those of ferric oxid. They make possible the exchange of bases observable in the soil. This becomes effective with the exhaustion of the soluble nutritive sub- stances in the soil as is made clear by the following experiment carried out by Lomberg*. A hydrated silicate was kept for three weeks in contact with water containing carbon dioxid, and, after some time, the following compo- sition was found :— if II. Original silicate. After treatment with water containing carbon dioxid. UIC HACIC Cite ee 46.64 per cent. 54-03 per cent. Aluminum” oxid’ 2... . 2O20N0 BolOsrrge Shs IZOLASSUUMIE acl tee on DOS wee we ey Eee 'SOYO UT ba (ye. BUSA irae le a cea COO wi vn If this leached silicate II. was again treated with a solution of caustic potash, the following composition was found,—silicic acid, 46.60 per cent.; aluminum oxid, 35.67 per cent. ; potassium, 17.73 per cent. Therefore, in the silicate skelton, the greatest part of the potassium had been taken up again, so that a new condition of chemical equilibrium had been set up. If ammonium chloride was added to the original silicate I, the reaction resulted in,—silicic acid, 56.17 per cent.; aluminum oxid, 34.59 per cent.; potassium, 0.89 per cent.; ammonia (NH,) 8.37 per cent. If a very large excess of calcium salts had been present, instead of the ammonia, the cal- cium could have replaced the potassium entirely in the silicate, as has act- 1 Zeitschr. d. Geol. Ges. 1876, p. 318.. 266 ually been shown by Riimpler’s experiments and later those of Schloszing Such processes are constantly present and show how quickly a soil can be leached by continued abundant precipitation, or can be impoverished in the supply of its other valuable food stuffs by a one-sided supply of fertilizer. The addition of fertilizer and the consequent increase of nutriment does not always give the expected increase in the yield. This occurs especially in rich soils and is explained by the fact that such a soil is no longer in a con- dition to absorb, as a direct result of its wealth of nutriment. Soils poor in clay are especially able to cause such phenomena because of their small ab- sorptive power. A further painful surprise, connected with absorption, is the poisoning of the soi from metallic salts. All heavy metals combine actively and, on this account, for example, the failure of crops, observable near smelting works, may not always be ascribed to the sulfuric acid of the fuel alone, but often also to the larger accumulations of metallic compounds. The fact, as shown by experience, that plants will live in soil containing small quantities of copper, lead, zinc, etc., has, up to the present, prevented paying the neces- sary attention to this kind of soil poisoning. With potassium and ammonium, both of which combine actively, ab- sorption often takes place by exchange in equivalent amounts (3 parts K,O for t part NH,), whereby sodium, calcium and magnesia pass over into solution. The easily dissolved, salt-forming sodium is only weakly absorbed and, to a still lesser degree, the calcium, present in the form of its humate, carbonate or phosphate, which can easily be replaced in the silicates by other bases. Magnesium acts similarly. Acids are combined only when they form insoluble salts. This is especially the case with phosphoric acid, which forms insoluble compounds with calcium, magnesium, ferruginous earth and aluminum oxid. Sulfuric acid is very weakly absorbed, nitric acid and chlorin not at all. The latter case deserves consideration in the chlorin poisoning near hydrochloric acid factories. By the different absorptive capacity and the constant exchange of nu- iritive substances is explained the effect of many fertilizers which have a two-fold action,—disintegrating and thereby increasing nutriment and ex- hausting the supplies. Thus an abundant supply of potassium salts and Chili saltpetre exhausts the calcium and magnesium in the soils. The ex- pression, ‘soil impoverished from marling” indicates that marl, as well as gypsum, can prematurely exhaust the nutritive stores in the soil by a disin- tegrating action. In this disintegration lies also the value of sodium chlorid (common salt). A greater source of poor production is found in the acid content, especially in the abundance of humic acids which greatly weaken the absorption and are in a condition to dissolve all the elements in the soil. This subject has been treated more thoroughly under the disadvantages of moor soils and under the formation of swamp ore. 267 The less the various nutritive substances are retained and the more soluble their compounds, the more easily they are leached out. At best, they reach the deeper soil layers, and in regions of strong sudden precipitation, they can be carried away. The chlorids present in small amounts in most soils are most easily removed, then the nitrates, later the sulfates. This takes place slowly with carbonates of calcium and magnesia and the phos- phates are the most persistent of all. Chlorids are dangerous for agriculture in regions of very slight precipitation, where they accumulate in low lying places, and produce highly concentrated soil solutions. Under the same con- ditions, the so-called “alkali soils” are produced by carbonates and sulfates. The question of nitrogen is the most important. The nitrates are so very soluble that the upper soil layers, containing the superficial roots, can be leached of all their nitrates even if the subsoil contains abundant nitrogen. This can only be made available by means of deeply rooted plants. In the face of general practice, not enough emphasis can be laid on the great losses occurring with unsuitable fertilization of the fields. Of the calcium salts, gypsum must be considered since it contains sulfuric acid. With calcium carbonates in damp climates, even on soils made from disintegrated lime stone, the calcium content may be poor because the carbonate is slowly leached out!?. On the other hand, all the potassium phosphates as well as the phosphoric compounds (with the exception of the alkalis) belong among the most persistent minerals. An exception takes place only in soils with free humic acids. Here the phosphates and also the iron compounds be- come soluble and even the resistant silicates are decomposed and carried over in a soluble form. In this way moor soils are exhausted of all their mineral elements, excepting quartz. The natural process of enrichment of the soil by weathering and by the action of wind in moving soil masses, by the decay of organic substances, etc., which effectively counteract leaching, is of value only in long-lived plantations. Here the fact, that the deep growing roots get the nutritive sub- stances from the subsoil, again made available for the upper soil layers by the falling of the leaves, is surely of great importance. In our plantations of one and two-year old plants, we find this help only in the use of green manuring. Finally, soil impoverishment from draining must not be passed over. However useful this practice is, as already acknowledged under soil aeration, in places it can act most injuriously. This refers especially to the leaching of nitrates from the soil in localities, where the fertilizer cannot be exten- sively supplied. Naturally the loss reaches a significant amount where an abundant supply of nitrogen is present, as is shown, for example, in Lévy’s analyses of the drain water from the Parisian sewage fields’. In a liter of 1 (if water containing carbon dioxid comes in contact with calcium carbonate it forms calcium bicarbonate, which is much more soluble and passes off in the drainage waters. This always occurs in soils containing organic matter.—H. S. R.) 2 2 Wollny, E., Die Zersetzung der organischen Stoffe, etc. Heidelberg 1297, p. 4. 268 the drainage liquid, as it flowed away, were contained 0.8 to 0.9 mg. of nitro- gen in the form of ammonia and between 19.1 to 27.1 mg. of nitrogen in the form of saltpetre. The liquid sewage used for the irrigation contained 24.9 mg. ammonia nitrogen and 0.9 mg. saltpetre. A comparison of these figures shows that the fertilizing nitrogen introduced in the form of ammonia is oxidized almost entirely to nitric acid by bacterial action during its filtering through the soil. Way’s investigations' show that, on an average, no very large amounts of mineral elements may be detected in drain water. He found in 1000 parts only 0.003 parts of potassium, 0.186 of calcium, 0.138 of sulfuric acid, 0.002 of phosphoric acid, etc. Nevertheless we should not forget that continued reductions are involved which are added to one an- other, in case there is abundant drainage. A comprehensive summary of lysimeter experiments in Rothamsted, which covered 35 years, and more recent investigations in Holland? show how rapidly, as a rule, the nitrification of the fertilizers, such as the ammonia: salts, takes. place of itself. Even in the fall and winter the nitrification is so active, that great nitrogen losses may be expected. On this account it is ad- visable to use ammonia salts as a top fertilizing in the spring. When using sulfates and chlorids of ammonia, the calcium combined with the sulfuric and hydrochloric acids is washed away in large quantities in the drain water. This process is necessarily preliminary to the combi- nation of the ammonia in the soil and the subsequent nitrification. If the calcium carbonate does not suffice for this conversion, the ammonia salts easily become dangerous for the plants. Since the sulfates and chlorids of potassium, like those of ammonium, form gypsum and calcium chlorid, which are not absorbed by the soil, the necessity of a periodic liming is evident. B. THE Work OF THE SOIL ORGANISMS. The activity of animal life in relation to the changes in the soil is men- tioned in the third volume of this work. In this is concerned primarily the work of the soil bacteria, the agricultural significance of which has been shown in a very comprehensive short summary by Behrens* and Hiltner*. According to the chief work performed by the bacteria, we could speak of those which set free the nitrogen and others which attack the carbon compounds (as, for example, the pectin and cellulose ferments) and finally those forming humus and those decomposing it. But not only the action of these organisms on their substratum is of importance here, but, especially, their influence on each other. Some genera or species disintegrate one an- other, others nourish each other. 1 Further analyses by A. Mayer, Agrikulturchemie, 5th. Edition, 1902, Vol. 2, Section I, p. 118. 2 Beleuchtung der Bodennitrifikation durch Drainwasseruntersuchungen. Mit- teil. d. D. Landw. Ges. 1906, Sttick 13. 8 Behrens, Die durch Bakterien hervorgerufenen Vorgange im Boden und Diin- ger. Arb. d. Deutsch. Landwirtsch.-Ges. 1901, Part 64. 4 Hiltner, L., Ueber neuere Erfahrungen und Probleme auf dem Gebiete der Bodenbakteriologie ete. Arb. d. Deutsch. Landwirtsch.-Ges. 1904, Part 98. 269 The influence of carbon disulfid serves as an important example, for, besides a poisonous action, a stimulus directly beneficial to growth has been assumed for it. The latter is thought to be recognized in the fact that a clearly recoghizable increase of fertility sets in after the disappearance of the carbon disulfid and its influences which arrest growth. Hiltner suc- ceeded in proving that the carbon disulfid chiefly conditions the changing phenomenon by disturbing the equilibrium of the bacterial flora of the soils. By means of its ability for dissolving fats, it suddenly forces back the bac- teria which had prevailed up to that time, just as it also stops entirely the increase of all species, so long as it is present unchanged in the soil. If the poison become diluted, or disappears through conversion, the long repressed numerical growth of the soil organisms increases in such a way, that, for example, an increase of 9 millions of the species growing on meat-pepton- gelatine to 50 millions in one gram of soil could be proved in one case. Thus an increase in the nitrogen production and with it of the potato harvest could be determined chemically by Moritz and Scherpe. With reference to the behavior of the nitrogen bacteria described in the second volumet under soil bacteria, we will here only supplement the facts stated there. After Winogradski especially had proved the con- version of the ammoniacal nitrogen to nitric nitrogen to be the successive achievements of two different groups of bacteria (builders of nitrites and nitrates), it was determined by Omeliansky that the nitrogen of the organic substances must have been previously converted by other bacteria to am- monia. Disturbances can easily occur in this work, since these bacteria are most sensitive to dissolved substances. Thus, for example, the activity of the organism forming nitric acid stops absolutely if any traces of ammonia are present. In contrast to the above, numerous other species of bacteria (more than twenty have already been identified) possess the ability of denitrification, 1. e., the reduction of the saltpetre to free nitrogen which passes off into the air. People have wanted to trace to this process the fact that fresh stable manure, under certain circumstances, injures the saltpetre contained in the soil and that straw fertilizing acts disadvantageously. This phenomenon is now chiefly explained by the fact that protein forming organisms have laid hold of the available nitrogen in the soil. (Pfeiffer and Lemmermann as well as Gerlach and Vogel). These bacteria transform the saltpetre first into the nitrite and then into protein-like compounds. That definite secondary con- ditions belong here is shown by Hiltner’s experiment in which straw fertiliz- ing was proved to be very injurious for potted plants, while the same amounts on open land had a beneficial effect. This contradiction may prob- ably be traced to the fact that the protein thus produced can be transformed more quickly in open ground to products which can be utilized again. 1 (Page 89 in the German edition.) 270 In studying the conversion of nutritive substances and their transfor- mation by soil bacteria, the process of the storage of nitrogen, 1. e., the assim- ilation of free nitrogen by bacteria, is to be considered. Besides the anaerobic Clostridium Pastorianum (Pasteurianum), determined some time ago by Winogradski, which with sufficient amounts of carbo-hydrates can make use of the atmospheric nitrogen for its nutrition,—aerobic species have been found by Beijerinck such as Azotobacter chroococcum. This species, present in every field soil, consumes extremely large amounts of carbo-hydrates by its nitrogen assimilation (according to Gerlach and Vogel 8.9 mg. nitrogen in I gram grape sugar). The changes in forest litter should be included here. The nitrogen en- richment due to them has been caluculated by Henry’. He emphasizes that nitrogen is stored up with the decomposition of dead oak and beech leaves and spruce needles. This decomposition is very active on damp soil in summer, but scarcely noticeable in winter, or when mixed with soil. Ac- cording to his calculations, fallen oak leaves accumulate 20 kg. of nitrogen per hectare within a year. On dry soil the dead foliage either does not be- come enriched at all (in the red beech), or only very insignificantly (white beech, spruce). In no case, however, was any loss of nitrogen noticed. The active enrichment of the soil by the symbiotic tubercle-forming bacteria should also be mentioned here. Cultures of these bacteria have been introduced into commerce under the name “Nitragin”? and cultures of non- symbiotic nitrogen gatherers are sold under the name “Alinit.””. More recent investigations indicate that not only bacteria of the same species adapted to individual host plants may be assumed, but that even different species may be distinguished. Hiltner contrasts two species chiefly on account of their morphological and physiological differences ; viz., Rhizobium radicicola and Rh. Beijerinckii. The activity of these tubercle bacteria in their relation to the Leguminoseae begins only when the Leguminoseae have suffered for some- time from nitrogen hunger and they are inactive when nitrates are present in the soil. This should be mentioned only in passing to illustrate further the dependence of bacterial life on various factors. The root secretion of each plant must also count as such a factor. Even the very healthy seeds which get into the soil and the green parts of healthy seedlings have a specific bac- terial flora, which can increase greatly and swarm out into the soil. Other micro-organisms can be pressed back by these*. From such inequalities of the growth conditions in the soil must arise necessarily significant fluctua- tions in the individual number of each species of bacteria and thereby in the whole achievement so far as the production of nutriment favorable for culti- 1 Henry, E., Ueber die Zersetzung der abgefallenen Blatter im Walde ete. (Annal. Sc. Agron. franc. VIII). cit. Centralbl. Agrik. Chem. 1904, p. 793. 2 In regard to soil inoculation, it should be taken into consideration that bac- teria, like all plants, will thrive only when the soil is so constituted that it favors their increase. As Remy has very characteristically expressed it, “they must find their proper soil climate.” 8 Duggeli, M., Die Bakterienflora gesunder Samen ete. Centralbl. f. Bakt. II. 1904, Vol. XIII, p. 198. Cyl vated plants is concerned. If now, for various reasons, as, for example, specific root secretions, certain species of bacteria, which are attracted to any definite plant variety and incited to great increase, carry over various nutritive substances, primarily, nitrogen, in a form unfavorable for the culti- vated plants, it can happen that chemically the supply of nutritive substances may be sufficient, perhaps even abundant, and yet the product may fall off. We then face the phenomena of soil exhaustion or “fatigue.” Hiltner men- tions experiments in reference to this. He perceived definite indications of soil exhaustion in the third generation of peas, which during a period of three years were grown seven times in pots in the same soil, but differently fertilized. “The plants became sick, were easily susceptible to attack, turned yellow prematurely and gave poor seeds.” In the later generations, the dis- eased conditions were overcome in this experiment. ‘The roots of the pea plants were now noticeably browned, but were perfectly white and healthy inside, and it could be proved that a regular bacteriorhiza was present, which, formed by well-adjusted, beneficial bacteria, prevented the further penetra- tion of the injurious organisms.’’? In regard to the exhaustion of the grape, Behrens (loc. cit., p. 110) cites the observations of A. Koch, according to which it could be produced by an accumulation of injurious micro-organisms. After sterilizing the diseased soil (not the healthy soil), the growth of the vines improved. If such a change in the composition of the bacterial flora takes place in a direction injurious to cultivation, it explains the increase of soil exhaustion due to the repeated growth of the same plant on any given piece of land, with short intermissions. And this accumulation of destructive elements is of importance not only for the bacteria, but also for other vegetable and animal enemies which can cause soil exhaustion. Among the bacteria which accumulate in the soil with repeated culti- vation of the Leguminoseae, Hiltner found that the pectin fermenting organ- isms became active. He found that in soil greatly exhausted by peas, per- fectly healthy pea seed rotted especially because of these bacteria known as acid formers. Another variation in the normal work of soil bacteria is the turning the fertilizer to peat. In heavy soils, often after some years, the fertilizer has been found pretty much undecomposed. In the same way green manure turned under too deep, turns to peat. As a result of the limited supply of air, the formation of raw humus is completed. The end and aim of working the soil, however, is the production of a suitable humus covering, for by the humus we obtain an equalization of the extremes of heat and cold, mois- ture and drought and the suitable nutritive soil which alone makes the exis- tence of most bacteria possible. If this is present, field soil can develop its actual life, which, to a certain degree, is measurable by the production of car- bon dioxid. How the bacteria co-operate in this, is shown by some statements 1 Bodenpflege und Pflanzenbau. Arb. d. D. Landwirtsch.-Ges, Part 98, p. 74. 272 of Stoklasa and Ernst’, who reckoned the respiratory intensity from 100 g. of dry substance of the Bacterium Hartlebi, a denitrifying bacterium, to be 2.5 g. of carbon dioxid per hour; in the same amount of dry substance of Clost- vidium gelatinosum, an ammonia former, the culture gave 2.0 g. carbon dioxid. The fact that the carbon dioxid production of a field is actually de- pendent primarily, on bacterial life, is demonstrated by the circumstance that no carbon dioxid was produced in observable quantities after experimental earth had been sterilized. We find the following statements in the work of the above named authors on the influence of aération. Forest soil taken from a deep position gave 59 mg. per kilo. of carbon dioxid within 24 hours in aérobiosis 0 mg. in anaérobiosis, while peat soil yielded 41 mg. in aérobiosis and 7 mg. in anaérobiosis. Naturally, heat and moisture also act determinatively. The greater the production of carbon dioxid in a field, the more completely does the chemical process of the combination of the free ammonia take place, as Schneidewind? has observed. This question comes under consideration here in as much as the losses in nitrogen with an addition of animal manure rep- resent an impoverishment of the stores in the soil. If stable manure with ordinary treatment is left in a manure pit, it shows a nitrogen loss of 30.31 per cent. after lying three months. If it lies, however, on an underlayer of old manure, producing a great deal of carbon dioxid, the loss amounts only te 16.64 per cent. Here the abundant carbon dioxid must have combined the free ammonia or have prevented the disassociation of the ammonium carbo- nate already formed. Among the most serious injuries, because the most frequent, be- longs the so-called “unripe soil.” This is distinguished by its lack of elasticity from the ripe soil which, under the influence of the soluble salts in the soil and the micro-organisms, takes on the friable structure al- ready described. In consideration of the great work which the bacteria per- form in soil decomposition, we can assert that the ripeness of the soil is due to their work. If we do not know by far all the processes taking place in ripening soil, we do know that we may consider the ripening up to a certain stage as actual fermentation. Attention need be called here only to the special pectin fermenting organisms (Plectridia) which seem of importance in germ- inating seeds of the Leguminoseae and further to the cellulose fermenting organisms with the great formation of hydrogen and methane (marsh gas CH,). Further, the Streptothrix species come under consideration as humus fermenting organisms, but especially the granulose organisms forming acids’, which produce chiefly butyric acid and carbon dioxid. In this, the Plectri- dia take over the chief share in the mineralization of the organic substances. ut Stoklasa, J., and Ernst, A., Ueber den Ursprung, die Menge und die Bedeutung des Kohlendioxyds im Boden. Centralbl., fiir Bakteriologie etc. Section II, 1905; Vol. XIV, Nos. 22 and 23, p. 725. ° Schneidewind, Zur Frage der Stalldiingerkonservierung. Deutsche landw. Presse 1904, No. 73. se Lohnis, F., Ueber die Zersetzung des Kalkstickstoffs. Centralbl. f. Bakt. II, 1905, No. 3-4, Dy Oils 273 The nitrogen collectors (Bacillus radicicola and B. megaterium, Clostridium Pasteurianum, Azotobacter) as also the ones forming ammonia (Bacillus ureae, B. albuminis, B. proteus vulgaris’, B. butyricus, B. mycoides, B. sub- tilis, B. mesentericus vulgatus, B. foetidus, Bacterium coprophilum, etc.) the nitrifying Bacterium nitrobacter, etc., and the denitrifying genera (Bacillus mycoides, B. substilis, B. liquidus, B. nubilus, B. vulgaris, B. coli, B. prodigiosus, B. liquefaciens, Bacterium fuscum, Clesteridium gel- atinosa, etc.), have been considered and attention should now be called to the specific organisms of decomposition. All these biological processes are enacted in ripe soils, supplementing or combatting one another, according to the climatic conditions of the soil at the time. Besides bacteria, green algae, the appearance of which counts as a sign of good ripening, have been considered to be nitrogen collectors. According to Koch*, however, this is not the case, but their value lies in the fact that by their chlorophyll activity they furnish carbon for the soil bacteria, which combine nitrogen. Beijerinck, Schlosing and Laurent insist that the blue- green algae can assimilate free nitrogen and, according to Saida*, a number of mold fungi should also have this ability. As Treboux* has recently emphasized, the activity of the nitrite and nitrate bacteria may frequently be lost, but the ammonia retained in the soil is always at the disposal of the plants and used up by them; this may still be taken for granted for many cases. Other investigators have also proved the usefulness of ammonia. Ultimately, however, the formation of the ammonia in the soil is based on the decomposition in which bacteria participate. The growth of the majority of micro-organisms affecting the fertility of the soil is connected with an abundant fluctuation in moisture, and the passage of heated air over the soil with its drying effect. These conditions are lacking in heavy soils in wet periods,—i.e., the soil remains unripe. Here the cultivation of useful soil bacteria succeeds only with a constant working of the soil. Acknowledged practical workers recommend the quickest possible turning over of the grain stubble on loamy soils in order to obtain a greater nitrogen gain by an earlier soil ripening. In the Lauch- stadt experiment station about the same results were obtained by early ploughing as by a green manuring. In spring planting on all heavy soils, a fall ploughing is the best precaution against unripe soils. Recently, letting the ground lie fallow® has again come into use for heavy soils. In light soils it should be considered a wasteful process. The benefit of letting ground lie fallow is its disintegrating action; no final de- 1 Stokiasa, J., Ueber die Schicksale des Chilisalpeters im Boden ete. Blitter f. Zuckerrtibenbau 1904, No. 21. 2 Koch, A., Bodenbakterien- und Stickstofffrage. Verh. d. Gesellsch. deutcher Natur. zu Kerlsbad. 1903. Part I, p. 182. 3 Vogel, J., Die Assimilation des freien elementaren Stickstoffs durch Mikro- crganismen. Centralbl. f. Bakteriol. IJ, 1905. Vol. XV, p. 174. 4 Treboux, O., Zur Stickstoffernihrung der griinen Pflanzen. Ber. d. botan. Gesellsch. 1905. p. 570. 5 Hillmann, Bedeutung der Agrikulturphysik ete. Nachrichten aus dem Klub der Landwirte, 1902, No. 453 and Mitteil d. D. Landw.-Ges, 274 cision has been reached as yet as to how this effect is produced. It is thought that in this, physical, chemical and soil bacteriological processes interact supplementarily. The frequent thawing and freezing in the winter serves to break and loosen the soil. Thus the action of the atmospheric processes is favored and the soil opened for the beneficial species of bacteria. It has not been determined with certainty to which genera these belong. Hiltner has proved first of all, that they are not the Alinit bacteria. In the end the usefulness will be decided by the greatest accomplishment of the nitrifying bacteria; for, according to Reitmair’, the nitrification in good mild soils with sufficient heat begins immediately after the fall harvest in such a way that the nitrate requirement of the subsequently planted grain will be met until the next spring. In this, however, a suitable friability and a definite calcium content is taken for granted’. (See also the statements under Drain Water.) Naturally it must be emphasized with Stutzer® that the land may be al- lowed to lie fallow only under certain fixed circumstances. It is thought that this may be done if it seems financially most advantageous for the agri- culturalist to do without the field for the long time while it is lying fallow, rather than to use the more quickly acting green manure and stable manure. When working with soils tending to unripeness, emphasis should be laid on this lying fallow only because it loosens the soil mechanically and does not affect the fertilizing salts. The nitrogen of the organic fertilizing masses seems, as Pfeiffer* especially emphasizes, to be held fast in the soil, capita- lized as it were, and then shows a long subsequent action. This author is, however, an opponent of the theory of letting ground lie fallow, which he characterizes as a robber cultivation, so far as the stock of nitrogen is con- cerned. He sees in this an incomplete restitution of the amounts of nutri- ment removed from the soil by the crops. In Pfeiffer’s opinion, the soluble nitrogen compounds obtained by letting the land lie fallow are lost again in great part from uncultivated soils by the water which soaks through. Such considerations, in my opinion, are entirely justifiable for light soils, but do not hold good for heavy soils provided with an abundant absorptive power by the clay and weakened by the harvests. 2. RELATION OF THE NUTRITIVE SUBSTANCES TO THE PLANTS. The phenomena treated in this and the following division, are rarely the result of only a lack or an excess of the nutriment in the soil. They are usually the result of the co-operation of numerous factors, among which atmospheric humidity plays an especially decisive réle. We will not forget that almost all diseases are produced by an unsuitable combination of the 1 Reitmar, O., Die Stellung der Brache und der Griinditingung in unsern moder- nen Fruchtfolgen. D. Landw. Presse. Sond. 1903. 2 Wohitmann, F., Fischer, H., and Schneider, Ph., Bodenbakteriologische and bodenchemische Studien aus dem Poppelsdorfer Versuchsfelde. Journ. f. Landwirt- schaft 1904, p. 97. J 3 Stutzer, A., Die Nutzbarmachung des Stickstoffs der Luft ftir die Pflanzen. D. Landw. Presse 1904, Nos. 10-19. 4 Pfeiffer-Breslau Stickstoffsammelnde Bakterien. Brache und Raubbau. Berlin, P. Parey, 1904. cit. Centralbl. f. Agrik. Chem. 1905, p. 599. 275 normal vegetative factors and are disturbances in the equilibrium of the interacting nutritive processes whereby certain ones are repressed while others predominate. If we now speak of diseases due to a lack, or an excess of moisture and nutritive substances we also involve in this the phenomena in which atrophies and hypertrophies occur in various parts of the plant body. These need not arise from an actual lack or excess of moisture and nutritive substances, but are simply produced by the unfitness of the plant, from the combination of the factors of growth, to nourish all its organs advantageously for the de- velopment of the whole. The absolute phenomena due to lack and excess are approximated on this account by the relative ones in the form of dis- turbances of the local equilibrium. A. Lack or MOISTURE AND NUTRITIVE SUBSTANCES. a. Lacxk or MoIsTuRE. INFLUENCE OF THE VARIOUS PLANT COVERINGS. After having considered the physical processes leading to a lack of moisture in the soil, and after having discussed a number of phenomena of diseases arising therefrom, we must consider supplementarily the influence which the covering of vegetation itself exercises on the water content of the soil. On the same soil, with the same atmospheric conditions, a cultivated plant will find a supply of moisture sufficient for its development on one part of a field, and not on another part, if on the former some species has been grown which makes a small demand on the water content. Therefore the preceding crop is of significance for each planting. As Wollny' has determined, the water content is less in the root region of a planted field than in the corresponding layers of the naked soil. The more luxuriant the plant growth and the thicker and longer lived, the more water is lost from the soil. Experiments have not determined any fixed scale for the use of water, yet they indicate that, on an average, the ever- green conifers require the greatest quantities while deciduous trees and perennial fodder plants follow in a descending scale and the superficially rooting field plants make less demand on the whole supply of the water in the field. Of the latter group, the large, richly leaved, erect Papilionaceae, such as the field and bush beans, seem to require the most water at the time of their chief development, while the roots and tuberous plants cultivated in wide rows should be named last. In summer the perennial fodder plants use somewhat greater quantities than field plants and conifers. This is re- versed in the spring and fall. In winter the requirements of the different plants equalize, except the conifers, which in mild winter weather constantly withdraw definite amounts of water from the soil. 1 Wollny, E., Ueber den HBinfluss der Pflanzendecken auf die Wasserftihrung der Fliisse. Vierteljahrsschr. d. Bayer, Landwirtschaftsrates 1900, p. 389. 276 v. Seelhorst' treats the same subject and comes to the conclusion that so far as moisture is concerned, rye exhausts the field much less than wheat. This circumstance is very important when planting possible subsequent crops for green manuring, for, after wheat, which is cleared later from the field, this crop not only reaches the soil later, but also finds the soil much drier. Clover exhausts the water in the soil very greatly so that, aside from the fact that the soil easily becomes loosened by the clover stubble, in dry years, the’ winter crops following the clover can only develop slowly and unevenly be- cause of the lack of moisture. On the other hand, the potato, at least the variety ripening moderately early, seems to form a very good early crop, since it leaves the soil fairly moist. Peas also form a good early crop for winter grain. Oats are con- sidered by v. Seelhorst to be especially unfavorable, not so much because they exhaust the nutritive substances as because they remove water to so marked an extent. In connection with field plants, we should consider also the injurious influence of grass. It is easy to understand that a close turf keeps water from the roots of plants, especially fruit trees and impoverishes the friable soil, but recently a direct poisonous effect of grass? has been mentioned which may possibly be due to the fact that beneficial bacteria species are suppressed by it and injurious ones favored. In the case given, the roots of the apple trees were long, abnormally thin and browned, the leaves were very light in color and dropped 4 days earlier. The foliage was sparse, the wood growth scanty. As soon as the roots or even only a greater part of them reached soil not covered by grass the phenomena of disease dis- appeared. These phenomena agree essentially with those produced on heavy, impervious soils, with a scarcity of oxygen, so that it seems in no way neces- sary to assume any poisonous action. We find, in many cases, especially on light soils, that the turf does no injury, if care is taken to have nutritive sub- stances within reach of the roots. On close clay soils, the grass is kept green for a long time by the water rising by capillary action from the subsoil, thereby removing a great deal of moisture from the subsoil without return- ing it in quantities worth mentioning during the period of vegetation, since the grass uses the atmospheric precipitation itself. WILTING. In discussing “physiological wilting,’ mention was made of the fact that the phenomena of wilting can appear even with an abundance of mois- ture in the soil, since the roots function incompletely. In soils with a high content of soluble salts, the water, under certain circumstances, can be held so fast that the roots meet their need only with great difficulty. Phenomena 1 y. Seelhorst, Untersuchungen itiber die Feuchteigkeitsverhdltnisse eines Lehm- bodens unter verschiedenen Friichten.” Journ. f. Landwirtsch. 1902. Vol. 50. cit. Cen- tralbl. f. Agr. Chemie 1903. Part 6. 2 Bedford, Duke of, and Pickering, Spencer U., The effect of grass on trees. Third report of the Woburn exper. fruit farm. London, 1908. : : 277 then become evident, which can also be produced experimentally by the use of highly concentrated nutrient solutions :—short internodes, smaller leaves, short roots having a great tendency to decay, reduced production and trans- piration. A further cause of wilting is a lowered soil temperature. If a de- gree of heat is not reached which is required by a certain plant so that the roots can begin absorbing the water, while the temperature of the air permits evaporation by the leaf apparatus, this disturbed equilibrium between water demand and supply makes itself felt by wilting. A special, not rare case, is the wilting of hot bed plants when the pots are cooled during the re-working of the hot beds or during transplanting. Inexperienced gardeners then water the plants abundantly and the turgidity is restored if the water, previously warmed, awakens root activity. By a repetition of the cooling, the same experiment can be carried out until finally the pot is overloaded with water and the roots break down from a lack of oxygen. Another case of the wilting of potted plants was observed by Hellriegel. He found that plants wilted in large pots, which held three or four times as much water as small pots of plants of the same species, which did not wilt. This circumstance is explained by the relative water content of the soil, which in the small pots amounted to 14 to 20 per cent., while the absolute larger quantities of water in the larger amount of soil in the large pots was so disturbed that it represented only 11 to 15 per cent. of soil moisture. In this case, absorption was made more difficult for the roots in the larger pots, by the less easily transported water held more firmly in the capillaries of the soil, so that evaporation was in excess. In contrast to this physiological wilting we might term mechanical wilt- ing those phenomena due to an actual lack of soil moisture be- cause the mechanical transportation of water slackens in the ducts. Nat- urally with the great demand for moisture in the leaves and the scanty re- inforcement in the ducts, the air content increases and in this increase of the air content above a certain degree may be seen the arrest of the water cur- rent in the axial organs, as Strasburger' emphasizes. In this, the air in the tracheal elements will be more dilute, as the transpiration and assimilation on warm days” are stronger, and the result is that a moistening of the soil becomes so much the more quickly effective. In general, watering exerts a lesser influence, the greater the turgidity of the plant*. The great tracheal air dilution shows itself also in the well-known fact, that field plants, wilting rapidly in hot weather, will stiffen from the dew on the soil at night,— especially since leaf evaporation is repressed at this time. 1 Strasburger, Ed., Ueber den Bau und die Verrichtungen der Leitungsbahnen in den Pflanzen. Jena 1891. cit. Bot. Zeit. 1892, p. 261. 2 Noll, Ueber die Luftverdiinnung in den Wasserleitungsbahnen der hdheren Pflanzen. Sitzungsber. d. Niederrheinischen Ges. f. Natur- und Heilkunde. Bonn 1897, Il. p. 148. 3 Chamberlain, Houston Stewart, Recherches sur la séve ascendante. cit. Bot. Jahresb. 1897, p. 73. ; 278 CHANGE IN PropucTION DUE To LAcK oF MoISsTURE. The difference in the harvest yield, resulting from a lack of moisture, has also been considered in previous divisions, so that here we need cite supple- mentarily only a few other cases. Hellriegel’s' experiments are most de- cisive. Two tests of clover were taken from a field, in which, in places, the plants had begun to wilt. There was found :— In, wilted alants.s. 2 2tee.< Leaves 71.0 per cent. water, petioles 78.4 per cent. Lgavess7i.1. °°" > water, spetioles+o0.c anes In turgid leaves among the wilted ones....... Leaves 82.5 ce ce ce ce water, petioles 90.0 The wilted leaves contained in the leaf-blades ca. 29 per cent. of dry substances; in the petioles, 19 to 21 per cent.; while the turgid leaves con- tained in their leaf-blades 17.5 per cent. and in the petioles 10 per cent.,—1. e., only about half that of the wilted plants. An example of the influence of drought on grain is given by Prianisch- nikow’s* investigations, according to which the nitrogen content increases in corn, if the moisture decreases. Stahl-Schroeder’s* studies give a more detailed representation of the influence exerted by the taking up of nutritive substances and their assimilation in dry years. After mentioning the well known fact, that phosphoric acid hastens ripening, while nitrogen and potas- sium delay it, he notes the importance of the months before blossoming for the taking up of the nutritive substances. If the soil moisture is deficient at this time, the organic substances will be in smaller quantity. But the nitric acid, which penetrates easily through the cell walls, will find its way into the plants and in its turn again incite the taking up of phosphoric acid, in order to effect the formation of the proteins. In this way, in dry years, scanty harvests are produced with a high nitrogen and phosphoric content. The nitrogen increase becomes the more evident, since, with drought, the grain stores up the starch with much greater difficulty. The reverse may be de- termined in the Norwegian corn tests, the high absolute weight of which is caused by an abundant starch deposit. This is explained by the growth of the grain with abundant moisture under the influence of the long days. In Hellriegel’s experiments with barley, in pots filled with sand, we find, expressed in exact figures, the lowering of production, as the amount of moisture at the disposal of the plant is reduced. Soil moisture in percentages Dry Substance of saturation capacity. in Straw and Chaff in Grain 80—60 7394 mg. 4896 mg. )averages 60—40 5988 “ AT 33) 5" os 40—20 4842 “ 1942 "9". 9)'3- ames 1 Loe. cit. p. 544. 2 Prienischnikow, Ueber den Einfluss der Bodenfeuchtigkeit auf die Entwicklung der Pflanzen. Journ. f. experim. Landw. 1900. Vol. I, p. 19. 3 Stahl-Schroeder, Kann die Pflanzenanalyse uns Aufschlufs tiber den Gehalt an assimilierenden Nahrstoffen geben? Journ. f. Landw. 1904. cit. Biedermann’s Centralbl. f. Agr. Chem. 1905. Part 2. 279 The pots with a soil moisture under 20 per cent. of the saturation ca- pacity of the sand suffered so much from the summer heat, that the heads in the upper leaf sheaths stood still, without advancing to the formation of kernels. In apparent contradiction to such results stand the observations of practical agriculturalists that in perfectly dry, so-called dust-dry soils, the plants can keep on growing, although nutritive substances are entirely lack- ing in the subsoil (it is sterile). Such cases are explicable as soon as the sterile subsoil contains water and the roots remain in the moisture. Haber- jandt! studied this case experimentally. He let the lower part of the roots of his experimental plants dip into distilled water, while the upper roots re- mained in soil layers, which, as shown by control experiments, were so dry that plants wilted in them. The plants of which the outermost roots dipped into distilled water showed a marked increase in dry substances ; from this it is evident that the roots found in the dry soil must have taken up the mineral substances. This division of labor by the roots explains the growth of our cultivated plants in spite of dry surface soil when their roots reach deep into a sterile, but moist, subsoil. According to Hellriegel, these changes in production, so well shown in grain, take place in the same sense in other cultivated plants. DISCOLORATION OF Woopy PLANTs. The typical result of a lack of moisture and abundant illumination is the vigorous development of the mechanical tissues. We need refer only to the conditions found in dry climates. For example, Jonsson? reports that, among other characteristics of arid plants, the walls of the epidermal cells often become slimy. In Haloxylon, Eurotia, Calligonum, Halimodendron, layers of slime cork alternate with those of common cork. The slime cork is very capable of swelling and is laid bare after the protective cork splits, so that it can take up water and hold it. Cells containing slime are found also in the assimilatory tissues. In Halimodendron, the secondary bark often becomes thick and spongy, thereby modifying the temperature extremes and easily storing up water. In the peripheral parts, abundant secretions of salts form a protection. These characteristics vary in regions where the water supply is abundant in the soil and in the air. Thus, for example, no slime cork is found in Halimodendron when grown in Copenhagen. Swanlund® reports from new Amsterdam on the extremely thick outer walls of the epidermis, the frequent depression of the stomata, the rolling in of the leaves with the resulting restricted transpiration. We have touched upon this subject earlier in the divisions on differences in latitude and on the defects of sandy soils and at the same time have considered the nature of 1 Cit. Biedermann’s Centralbl. f. Agr. Chem. 1878, p. 314. 2 Jénsson, B., Zur Kenntnis des anatomischen Baues der Wiistenpflanzen. Lunds Univ.-Arsskrift XXXVIII. Bot. Jahresb. 1902, II, p. 292. 3 Swanlund, J., Die Vegetation Neu-Amsterdam’s und St. Pauli’s in ihren Beziehungen zum Klima. Dissert. Basel 1901. 280 the red coloration. By artificial interference, a localized lack of moisture and thereby a formation of anthocyanin is stimulated if the leaves of plants, of which a red autumnal coloration is characteristic, be nicked or the branches girdled. Then in the middle of summer a red color appears on the © upper parts above the injury. In regard to the phenomena of discoloration produced by heat and drought, I will give some observations from 1892, in which year, in August, unusually high temperatures occurred together with hot winds. I found on, the 19th of August a temperature of 52.7 C. on especially heavy loam soil. All the plants wilted and the majority gradually lost their foliage. Naturally great individual differences were also noticeable. The leaves became discolored and fell, the lowest leaves of the branches being the first affected. In the Alder, the leaves fell without losing their green color. Acer Pseudoplatanus var. Schwedleri, the under side of the leaf is red. From the tips backward the intercostal fields of the leaves turned a reddish brown to leather color. Besides this, deep brown, perfectly dry rust spots were scattered irregularly over the surface of the leaf. The injured leaves remained in place. Acer Negundo. The upper leaves were somewhat flabby. The edges of the leaflets were curled upward. The leaves next below were a pale yel- iowish green, the lowest light yellow, uniformly rolled up on the dry edges. Acer plantanoides. The leaves show on their under side naie yellow, irregular, small rust spots running into one another and extending vetween the ribs. The dried tips bend upward like hooks. Fagus silvatica. On the various leaves, not always tlie lowest, but the most exposed, were irregular, dry places with yellow, faded edges in the in- -tercostal fields. At times, the whole upper surface is eavally lightly browned. There is never any outlining of the edges. Vitis vinifera. At the beginning of the drought, among the normal green leaves are found yellowish ones. The lemon yellow discoloration, red in other varieties, begins at one place on the edge and advances into the intercostal fields until only the veins seem green. In spite of the drought, I found on various lower leaves the dry, angular spots of Plasmopara viticola. Prunus Persica. All the leaves are somewhat languishing, some (but not always the lowest) turning yellow from the tips backward. On some trees, the discoloration advances more quickly along the veins so that at first the veining and then the rest of the surface of the leaf colors yellow-red to wine-red. Then the leaves drop. (Peculiarity of the variety). Prunus domestica. All the leaves are flabby. The majority, however, are still uniformly green with the exception of the lowest, which on many branches have become a whitish yellow and have slender, brown, reflexed, dry peripheral spots. Easily shaken off by the wind. Prunus avium. The lower leaves, especially on the short shoots (brachyblasts), turn a uniform lemon yellow and fall. 281 Prunus Cerasus. Only a few leaves turn yellow, otherwise the entire foliage is still fresh. A proof that the cherry loves drought. Pirus communis. According to the exposure rust spots are found in greater or less numbers showing, however, no yellowing. At times dry areas appear on the edges of the leaves, but more frequently the whole surface is a dark umber brown (the under side lighter in color with a still fresh green or lightly brownish mid-rib). The edges strongly rolled upward. Because the petioles remain green, the injured leaves do not fall at all or only much later. . From these and numerous other observations it is evident that, on an average, the parts of the leaves furthest from the veins discolor and dry first and most. When periods of heat follow one another rapidly with a strong ‘sun action, the rust spots become very conspicuous; with a lesser intensity of the sunshine, a general discoloration in the form of spots prevails. Here belongs also the especially strong development of anthocyanin in dry, poor localities, which becomes noticeable even in the arctic regions, where the red coloration with the strong illumination is a_ prevailing phenomenon. Wulff! cites a very characteristic example. He found in places, fertilized by the excreta of birds, that the formation of anthocyanin disappeared in plants of which the vegetative organs seemed strongly redden- ed in arid regions. Finally, there must be considered the decrease in the power of move- ment of clover leaflets and related organs, with a continued lack of moisture In Mimosa pudica the periodic irritability is lost and the leaflets remain open,—‘‘drought cramp.” THE RED COLORATION IN GRAIN. The red coloration in grain in continued dry, hot summers has often called forth the theory that parasitic influences participated in it. Klebahn? tested more closely a special case, which was universally striking because of its wide distribution and intensity. He found that the red coloring matter appeared gradually in place of the cholorophyll. While the alcoholic ex- tract of normal leaves appears green, it is colored orfly slightly yellow in red 1 Wulff, Thorild, Botanische Beobachtungen aus Spitzbergen, Lund. 1902. In regard to the theory at present generally held that anthocyanin is said to form a protection for the chlorophyll against an excess of light, Wulff (p. 67) calls attention to Engelmann’s investigations from which it is evident that the light absorption of the red anthocyanin is complementary to that of the chlorophyll and accordingly does not retard the decomposition of the carbon dioxid. ‘‘This fact has moreover proved most fully the untenability of the Pringsheim-Kny-Kerner theory of pro- tection from light.” Wulff sees the advantage of the anthocyanin in its greater storage of heat. As I have mentioned already, I am unable to accept the above utility arrangements or the expressions of a “finality” in the organism and I per- ceive everywhere the necessary phenomena resulting from definite combinations of the factors of growth. The formation of anthocyanin seems to me to be the result of an excess of light on the cell content, rich in free acids, at the disposal of which there is no assimilate containing sufficient nitrogen. This condition can be pro- duced, as in plants of cold regions, by a lack of heat; in other cases by a scarcity of water, a decreased supply of nutriment, etc. 2 Klebahn, H., Hinige Wirkungen der Diirre des Friihjahrs 1893. Zeitschr. f. Pflanzenkrankh. 1894, p. 262. : 282 leaves in which the cholorophyll has been destroyed. The red coloring mat- ter is soluble in water and glycerin, insoluble in alcohol and turpentine, turning blue with potassium and ammonia and again red with acids. It is in combination with the cell sap, partly in the epidermis, partly in the assimila- tary tissue. In oats, the development of the reddened plants and their grain production was proved to be less than that of green ones. We have just made a study of the reddening of grains* and, in agreement with Klebahn, have come to the conclusion that in this redness only phenomena of a premature ripening are to be seen, together with a lack of moisture and great intensity ef light. In our treatise will be found also anatomical details as to the blasting and the appearance of the so-called “drought spots.” A yellow coloration of the walls of the bast fibres is worth noticing, which increases to a yellow brown, as is also the hardening of the cell contents in various groups of the assimilatory tissues. The death of leaves, due to sudden heat periods, should be distinguished from a normal death. The ieaf does not shrivel up as completely as the nor- mally ripened one,—1. e., a leaf, the contents of which are nearly exhausted— or it can do so only in places. In the normally ripened leaf, only the entirely impoverished cells of the leaf tissue, which therefore collapse to a waved folded layer, are found between the epidermis of the upper and of the lower sides, while in the former leaf just the remaining, more abundant contents stiffen the walls by drying, thereby more or less preventing the collapse. I also found the same discoloration phenomena in wild grasses (Arrhen- atherum) and expressed a warning against deceptions from anatomical in- vestigation. Especially angular or spherical masses appeared in the contents which reacted with iodine like starch and thereby could give the appearance of a still existing, greater assimilatory activity. The other reactions prove, however, that “residue bodies” of the chlorophyll decomposition are here in- volved which belong to the carotin group. They could be compared with adipocere. “Rebs” oF Hops. The disease, called by practical growers “summer rust,” “Fox” or “red tan,” consists in a spotting of the leaves, which advances from their bases. The spots attack the peripheral parts as well as the tissue groups lying between the different veins. By a partial destruction of the chlorophyll, the diseased places at first appear yellowish, then reddish and finally dry and browned. In the meantime the leaf continues longer in a wilted condition, finally, it shrivels and drops off, while the upper, younger parts of the vine are still fresh, green and developing. The new structures produced during this time are smaller in comparison with those of other plants which are un- affected and have not lost the lower leaves. If the disease remains restricted to the lower parts of the vine, the injury is not important; but, if it attacks 1 Sorauer, P., Beitrag zur anatomischen Analyse rauchbeschadigter Pflanzen. Landw. Jahrb. 1904, p. 596, Plates XV to XVIII. 283 the upper portions with the blossoming catkins, the harvest will be very light and an immediate gathering is advisable. The disease may be confounded easily with the “copper rust,” caused by the weaver moth, but is distinguished by its location since the copper rust colors the leaves on the upper part of the vines a reddish yellow and is recognizable from its finely spun threads on the underside of the leaf, while the summer rust causes a yellowing and drying of the leaves, beginning at the base of the vine. It is a sapping of the older organs by the younger ones, which require the organic material there present for their further development. The so-called “Pole Red” seems to correspond to the “blast” of grain and to be the result of a sudden dry period when the catkins mature. In this and the related diseases of reddening the lack of atrriospheric moisture plays an especially decisive réle, because watering only the soil rarely proves a remedy. It is better, if possible, to water regularly in the evening. But for larger areas in practical cultivation the necessary number of laborers and the great quantities of water may rarely be had. Hence re- sort must be had to preventative measures, in which either the excessive evaporation is reduced by extensive shading, or the saturation capacity of the soil is increased by the supply of fertilizing salts (not animal manure). Fr. Wagner! cites an example for the later case. He found in his cultivation that hop vines, without having been given nitrates, did not resist drought and vegetable or animal parasites so well as those fertilized with chili salt- petre and also their lower leaves turned yellow earlier. In the same way it has often been observed in practical agriculture that fodder and sugar beets withstand drought better when the soil has been fertilized with potassium salts or nitrates, or even with abundant stable manure’. Similar discoloration resulting from a lack of moisture has been ob- served in flax. This is described partly as the “Reds” (le rouge) and partly,— when the points of the stems turn yellow prematurely,—as the “yellows” (le jaune). “TLrar ScoRCH”—‘‘PARCHING OF VINES”—“‘RED ScoRCH.” The above are collective names for a group of phenomena distinguished with difficulty from one another, in which the leaves are colored red. Asa rule, the discoloration is followed by a partial or complete drying up of the foliage, which begins to fall prematurely. Recently Miiller-Thurgau’® has determined a parasitic cause for a definite form of reddening* and takes pains to emphasize the characteristics, apparent to the naked eye, distinguish 1 Waener, Fr., Salpeterdiingungsversuche des Deutschen Hopfenbau- Vereins Wochenbl. d. Landw. Ver. in Bayern 1904, p. 182. 2 See, for example, Jahresb.-d. Sonderausschusses f. Pflanzenschutz fur das Jahr. 1904. Arb. d. Deutsch. Landw.-Ges. 1905, p. 91. 3 Miiller-Thurgau, H., Der rote Brenner des Weinstocks. Centralbl. f. Bakt. H, 1903. Parts 1-4. 4 Another form of Red Scorch connected with Botrytis vegetation is described by Behrens (Untersuchungen tiber den Rotbrenner der Reben) in Ber. d. Grofsh. Bad. Versuchsanstalt zu Augustenborg 1902, p. 43. 284. ing this disease from others. With reference to the form of “Red Scorch,” described in the second volume of this manual and caused by Pseudopeziza tracheiphila (see Vol. I1., p. 278*) in which the discoloration often begins in the form of spots in the angles of the veins, it should be emphasized here that the leaf scorch, which is due to a lack of moisture together with strong sunshine, begins as a rule with a discoloration of the intercostal fields start- ing from the edge. The phenomena vary greatly, according to the variety and habitat, and at times only a shining yellow color is found instead of the reddening. The edges of the leaves often dry up. The kind of discoloration runs parallel with the progress of the summer blight in other woody plants, whereby it may usually be observed how the deficient moisture supply be- comes evident at first on the parts lying furthest away from the petioles and the mid-rib and then advances until finally only the immediate surroundings of the veins remain green. (See Changes due to place of growth.) In regard to the physiological activity, Muller-Thurgau had proved earlier that the formation of starch and its solution took place the more slowly, the less the water content of the leaves’ ; irrigated vines formed more sugar. A phenomenon manifesting itself like the parasitic scorch has been de- scribed by Sauvageau and Perraud? as the pectin disease (maladie pectique), the result of continued drought. In this, the leaf blades are loosened from the petiole. YELLOWING DUE TO THE GRAFTING STOCK. In our species of fruit there is often a lack of water, because a rapidly growing variety grafted on a dwarf stock, in times of great evaporation, is not able to convey the necessary water to the graft. On good soils pears, grafted on quince stock, often turn yellow, while trees on wild stock thrive well. In dry summers I found with such dwarf {runks that well grown scions, inserted later in the bark, formed strong but yellowish shoots, while the older top was green. In this too I see phenomena of the lack of moisture due to the quince stock which (especially if planted shallow) cannot obtain the necessary water. Pears on shallow planted quinces ripen their foliage more quickly and lose it earlier. PREMATURE DRYING OF THE FOLIAGE. When the foliage dies as a result of the summer drought, in which it usually hangs on the branch, because the petiole has remained fresh, the injury suffered by the tree is far greater than is generally understood. It is thought that the injury consists primarily in the premature stopping of leaf activity and the lessened formation of wood. Kraus’* investigations ' * Paging in the German original. 1 TIT. Jahresber. d. Versuchsstat. Wadensweil. Ziirich i894, p. 56. 2 Sauvageau, C. et Perraud, J., La maladie pectique de la vigne. Revue de viticulture 1894, p. 9. 3 Bot. Zeit. 1873, Nos. 26 and 27. have proved, however, that, besides this lack of additional growth, a positive loss in substance takes place, which is much greater than in normal fall de- foliation. The leaves killed by blight do not behave as do those which drop off in the fall. These have gradually given up to the trunk most of the sub- stances still utilizable for the plant body and in the end have been loosened by a round-celled layer of separation. The dried leaves, in which no such layer has been formed, retain the elements which contain nitrogen together with phosphoric acid and only the starch with the potassium reaches the trunk before the death of the leaf. By the premature drying of the foliage approximately twice as much nitrogen and phosphoric acid are lost to the plant as by the autumn leaf-fall. This is proved by analvsis of the leaves of a syringa carried through by Maerker. In percentages of dry substances, there was contained in Summer blighted leaves Autumn fallen leaves TSS G0 Sg RW ogee ne APs PR eR 1.947 1.370 Fes PIGIdG ACI ues bc a4 Ge anche Ot BPS cis 0.522 0.373 OU AGSIUEMNON ates ce ayece esas RR oie 2.998 3.831 CIS KIN UT Odie Paoli SC a ee atl 1.878 2.410 All mineral substances (iret tron carbon, dioxid )-:.).. ys... 8.028 9.630 The above amounts, if expressed in percentages of the whole ash, would be as follows :— Summer blighted leaves = Autumn fallen leaves INITIO Cte ame Unrate tiny xtlane pte: Ware lyse 24.0 14.0 PNOSMHGING Oldie ce ahs «cals sak Sine. toe 6.5 3.8 EZOnbeAGSIUME NG rahe Sie aya op east cocks ete Sede ee 29 39.7 THE BuRNING OUT OF GRASS. With the drying of the turf, as the result of hot periods in summer, the loss of nutritive substances must be considered especially in- meadows. Where there are no irrigating arrangements, there is no possibility of avoid- ing the injury. In ornamental planting, however, it may be avoided if the action of the light and thereby evaporation is repressed at the right time by mulching with hay or other light shading material. Sprinkling the grass surfaces is effective only when it can be carried out repeatedly during the day. In other cases, shading must be resorted to. SILVER LEAF. The “Silver Leaf” belongs among the phenomena which have not yet been tested experimentally in regard to their causes and therefore can be classified only provisionally. The disease so manifests itself in fruit trees that the leaves, otherwise normally developed, lose their dark green appearance and give a silvery, whitish reflection. As a rule only individual branches suffer and possibly 286 after June or July. In the following year, or in the second, at the latest in the third year, after the appearance of the silver leaf, the branch dies. In the specimens which I could examine after the lapse of a year, the phenomenon appeared often on the other branches after the dead branch had been removed, so that, for the present, I have formed the hypothesis that the silver leaf is an absolutely certain precursor of the death of a branch. It is found most wide-spread among apricots. I found the came also in plums and apples. The change begins in the older leaves of the spring growth, the youngest more often escape; likewise the late shoots developing suddenly in old wood from preventative eyes. First of all only a certain dullness of color is found, a loss of the gloss in places and, as it seems to me, an increased amount of air in the intercellular spaces between the various palisade cells or between them and the epidermal cells. Gradually the dull places become whitish, in fact because of a glandular breaking up of the epidermal cells between the finest ramifications of the veins which remain green. This loosening up consists of a dissolving, in places, of the connection between epidermis and palisade parenchyma. Aderhold', who also observed the disease in cherries and found that the cells of the epidermis mutually separate from one another, could prove that the variations from the healthy leaf, in places displaying the silver leaf, were found in the solvability of the intercellular substances (middle lamellae). He surmised that the intercellular substance in the diseased organs consisted of more soluble pectin compounds than in the the healthy leaf and, since the calcium compounds of pectic acid represent insoluble conditions, the theory is pertinent, that the disease may be due to a lack of calcium. According to this theory, the disease would also belong in the group of phenomena, due to deficient moisture and nutritive substances; only it must be emphasized in this, that the content of moisture and nutritive substances in the soil cannot come under consideration here, but that only in the plant itself can it be manifested locally. And this circumstance points to dis- turbances in the vascular system. This is favored also by the fact that the branches with silver leaf die prematurely. The apricots and plums which I observed showed gummosis and the apple trees suffered from the gnawing of bark beetles. It might be possible to strengthen the whole organism by rejuvenescence of the diseased trees and by supplying calcium. THE WATER Core oF APPLES. In the same way the phenomenon may be traced to the local vascular disturbances in which individual fruits of a tree in part, or as a whole, re- main hard and become glassy and transparent,—develop less color and are tasteless. 1 Aderhold, R. Notizen iiber einige im vorigen Sommer beobachtete Pflanzen- krankheiten, Zeitschr. f. Pflanzenkrankh. 1895, p. 86. 287 In investigating an apple, which was only partially glassy, I found in longitudinal section, that the particles of the skin were most intensively glassy and that, inside the fruit, the white, normal flesh extended from the base pretty nearly to the bud end. The glassy zone had a whitish marbling due to wedged-in groups of normal flesh. The seeds were mostly deformed, not ripe and still white. The healthy part contained abundant starch and intercellular spaces strongly filled with air. These spaces were poorer in air in the glassy part and there was no starch except in isolated, wedged-in cell groups. The glassy part turned brown more quickly in the air; some dex- trin could be found together with abundant grape sugar. In dry substances there was found in The healthy half The glassy hali Wiithiabiereheias ws Guba lhyig earn soa gs 21.48 per cent. 19.43 per cent. NVA CIbEHNe (GEO Sh oa a Galle aha ave 20.24 ce LEO gris qui Aderhold' found in Healthy fruit flesh Glassy fruit flesh SS OY ELE TI Se 0 ye Pe ER 0.718 0.925 ' Dry substances in percentages of the PGCSIMONVCROULES orga choc astic «Sh es Se 14.44 per cent. 12.60 per cent. Ash in percentages of the dry “RST 0 ee ae AR ee eee ee 2.093 per cent. 1.76 per cent. Malic acid in’ 190. ccm, jmice.'.... 0.92 g. 0.53 g. The most recent determinations come from Behrens”. He found in roo ccm. of Water Invert sugar Acid Pressed juice of the normal apple...... 87.38 g. 5.05 g. 0.50 g. Pressed juice of the partially glassy SWE 1S: the Mar Re Ae ee Ke 88.06 g. 4.40 g. 0.47 g. In agreement with my statements, the above figures show that the flesh of the glassy apple is considerably poorer in acid, dry substances and ash. The glassy appearance and the smaller size is explained by the fact that the intercellular spaces of the glassy part are filled with water and the cells are smaller. Practical growers believe they have observed that the following varie- ties tend especially to the production of glassy fruits:—Zurich Transparent apple, Gloria mundi, white Astrachan and Virginia summer Rose apple. On an average, in the first year of bearing, the little trees were more disposed to the production of such fruits than in later years. b: CHANGES IN PRODUCTION DUE To LACK OF NITROGEN. STARVATION CONDITIONS IN CRYPTOGAMS. In reference to the parallelism of phenomena in lower and in more high- ly organized plants, an example may be cited first of all from the fungi. 1 Aderhold, loc. cit.. p. 8 2 Behrens, J., Bericht d. Grofsh, Bad. Landes-Versuchsanstalt Augustenburg 1, J. 1904, p. 538. Karlsruhe 1905. 288 Fliorow!' tested the effect of starvation on respiration in Mucor and Psalliota campestris. In Mucor, respiration immediately falls to a great extent be- cause in this fungus there exists no storage of reserve stuffs in the mycel- lium. In the fruiting body of the basidiomycete, however, there is a great deal of reserve material and, for this reason, it is very independent of the nutritive substratum so that its respiration only falls very slowly with star- vation. In regard to the exchange of the proteins, Fliorow concludes from experiments with Amanita muscaria that the percentage of nitrogen as a whole increases during starvation chiefly because the substances free from nutritive substratum so that its respiration only falls very slowly with star- takes place, which is simultaneous with the periods of spore formation and ripening. A rapid decomposition of the protein follows at once. To be sure, the production of carbon dioxid and the taking up of oxy- gen gradually decrease in the starvation of fungi, but in unequal propor- tions, as was observed by Purjewicz*, with Aspergillus niger. Prantl® has given very good experimental observations on the prothallia of ferns. His experience. shows especially that, in the seeding of fern . spores, the most diverse variations occur in the prothallia. Some of them have a tissue capable of developing further (meristem), while others lack it and therefore are ‘“‘ameristic.” [Earlier investigations* had shown Prantl that the ameristic condition can occur with too small supply of air as with a scanty supply of water and indeed also of mineral substances’. The ob- servation, that under the most favorable conditions of illumination, ameristic individuals appear when the prothallia grow too close, led to the experiment of testing directly the influence of the nitrogen supply. Spores of the rapidly germinating Osmunda regalis and of Ceratopteris thalictroides were sown on different nutrient solutions. It was thus shown that the spores, germinated in distilled water, produced ameristic prothallia. They formed surfaces of 15 to 25 cells of pretty uniform size and similar content. The chlorophyll grains were poor in starch. On the other hand, the prothallia grown in a nutrient solution, free from nitrogen, but otherwise normal, were dis- tinguished by an extremely large starch content, but otherwise resembled the individuals grown in distilled water. Only the specimens grown in a nutri- ent solution with a nitrogen admixture (0.64 per cent. ammonium nitrate) were meristic. If specimens of meristic prothallia were transferred into a nutrient solution free from nitrogen, the meristem disappeared after 14 days, while the cells as a whole increased, had divided here and there and had been filled with starch. If, on the other hand, ameristic prothallia were placed in 1 Fliorow, A., Der Hinflufs der Ernaéhrung auf die Atmung der Pilze. Bot. Cen- tralbl. 1901. Vol. 87, p. 274. 2 Purjewicz, K., Physiolog. Untersuch. tiber die Atmung der Pflanzen. cit. Bie- derm. Centralbl. 1902, p. 180. 3 Prantl, Beobachtungen tiber die Ernaihrung der Farnprothallien und die Ver- teilung der Sexualorgane. Bot. Zeit.. 1881, p. 753. 4 Flora 1878, p. 499. 5 Reed has shown (Annals of Bot. 21; 501, 1907) that prothallia of G. sulphures were unable to form archegonia where calcium was absent. Translator. 289 a complete nutrient solution, they at once formed a meristem on their outer edges by a repeated cell-division, while the starch supply decreased. The distribution of the sexual organs varies according to the nutritive conditions. Ameristic prothallia bear only antheridia, never archegonia, which are associated with the presence of a meristem. Of especial impor- tance at this point is Prantl’s observation that ameristic prothallia of Os- munda, which had borne isolated antheridia, developed abundant archegonia after nitrogen had been supplied; besides the archegonia, antheridia also appeared. ile 4 % YT ayo “Aity Pp Othe Tae sarelaieote ye ; iii ale ie Rlectetiitenic - py are ¢ (oe ace A a A i @ PAs pA The? COPD a ; at © Pee ib riba tele OR Me fitor. 15 J uA oe fr ee ae as ei 7. ae aa a os Ci oe ho =i he? SK ath ap ony wel H ver Millar lisig ses Dil papas eer NS wy eee a. ace): » \ \ eee | , eos es 2a i a ‘ = - ¢ ‘ ah pi oar yale | she xi? a PART IV. MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Prof. Dr. G. Lindau And Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History of Berlin in burg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT j i i } i r.§ W . =4 ne a 2 * LE ‘ = Yon vem pe ae 4 ' ! i t iy is ey ; ‘ a t ’ Voptie Nia Fol sf ae Pie tg t 1 e ; =. j rap erat ah t Tay ates 4 “ . eo ae ne rte 4 ? ; Copyrighted, 1915 all = ¥ \ E opyng LeGs, iat ene, 5 By Res i ‘ ine Baye ae een : 5 } i wy 3 ‘on Bie ' 4 a bn vs ext. «fs FRANCES DORRANGE: ~-- « L ‘ ‘ rn ant ? : * ey ed Sccu tnd te alts 4 feat we 8 van Be Ce AERC LP One ME Te YEE Fs fe he tatiae « pad. ris z ee 7 , as Soar HAR Ph cl r Fi Ate > ‘ iy p| = . * aed « 2s " =z it re att isn « 2 F : hee Pa Pa I ae e ‘ THE RECORD PRESS” Bape nny of igltes 3 WWil ness Bemré, Pact tae 289 a complete nutrient solution, they at once formed a meristem on their outer edges by repeated cell-division, while the starch supply decreased. The distribution of the sexual organs varies according to the nutritive conditions. Ameristic prothallia bear only antheridia, never archegonia, which are associated with the presence of a meristem. Of special impor- tance at this point is Prantl’s observation that ameristic prothallia of Os- munda, which had borne isolated antheridia, developed abundant archegonia after nitrogen had been supplied; besides the archegonia, antheridia also appeared. From these changes produced by the nutritive substances is explained without forcing the tendency to “dioecia’ ascribed to some ferns by various authors ; by Millardett for Osmunda, by Bauke’ for the Cyatheaceae and for Platycerium, and by Jonkmann®* for the Marattiaceae. H. Hoffman‘ cites further notes pertinent here; first of all, Von Hof- meister, who assumes that in Equisetum the prothallia produce decidedly more antheridia in the light and in a dry locality, i. e., bear more male plants since the prothallia are almost entirely dioecious. Borodin found that germinating spores of Allosurus Sagittatus de- veloped antheridia when placed in the dark. THE PRODUCTION OF STERILE BLossoMs. (STERILITY. ) Sterile blossoms in phanerogams are due primarily to a lack of nitro- gen. This may manifest itself in very different ways; as already mentioned in the blasting of grain, a sufficient supply of nitrogen may be present in the soil but as result of a prolonged, intense drought there is lacking the carrier, the water, to bring to a further normal development the already differentiated stamens and pistils. On the other hand there may be in heavy seeding a struggle for nitrogen in which the plants that earliest attain most vigorous vegetative development take the nutriment from the less vigorous ones. In a consideration of sterility there must further be taken into ac- count the cases where the existing nutritive material is used up in some other way, so that a one-sided increase or decrease of a growth factor favors the vegetative utilization of the elaborated organic material to such an ex- tent that nitrogen sufficient to mature the sexual organs is lacking. Finally it not infrequently happens that the material is abundantly used in the de- velopment of the lesser nitrogen requiring male organs and no longer suffices for the development of the ovary. The cases among phanerogams where starvation conditions induce blossom development are not in opposi- tion to this view. Examples of this are found in our fruit trees, where dis- eased specimens with a pronounced decrease of shoot development “bloom themselves to death.” In horticultural practice plants are purposely starved in order to attain flower production (Kantua dependens, Correa, etc.) 1 Pringsheim’s Jahrbiicher, X, p. 97. 2 Bot. Zeit. 1878, p. 757. 3 Extrait des Actes du Congrés international. Amsterdam, 1877. 4 Hoffmann, H., Zur Geschlechtsbestimmung, Bot, Zeit. 1871. Nos. 6 and 7. 290 Lovers of cacti sometimes pull their plants from the pots in winter and let them shrivel, so that they may bloom more freely. In this case nitrogen is not lacking but the scarcity of water causes the plants to make use of the elaborated food in flower production. In treating of the bearing of sterile blossoms, due to insufficient water, Oberdieck' reports that, as a result of drought, the blossoms of large- flowered pansies drop prematurely while, with sufficient moisture, they develop the seed capsules. Double zinnias behave in the same way, like- wise the red flax and often, indeed, Phlox Drummondi. Garden beans do not set so well in dry years. Raspberries and strawberries give small, poorly seeded fruits. In the case of the ever-flowering wood strawberry there is a degeneration with continued drought, making the plants resemble the “Vierlander strawberries,’ since they no longer develop fertile blossoms. Zacharias* states that the latter variety of strawberries is one which is usually either staminate or pistillate, but rarely monoecious. He is of the opinion that pollination is incomplete where only a few staminate, so called “wild” plants, distinguished by their weaker growth, weaker runners and lower growing inflorescences with larger blossoms, are present on the fields. He emphasizes the fact that invariably few pistils develop, so that only a portion of the swollen receptacal is covered. We would lay the chief weight on the latter point and advise remedially a change of soil and variety. Zacharias recommends putting more staminate plants among the pistillate ones. Phenomena similar to those in the Vierlander strawberry have been observed in the black currant*. The sterility is said to be caused neither by dryness nor by a shady position, but is ascribed by practical workers to a varietal peculiarity. Likewise complaints are made as to the scanty setting of fruit in the Schattenmorelle (shadow Amorelle cherry). The “Praktische Ratgeber” (Practical Adviser) advises in grafting the taking of scions only from the trees of that variety which experience has proved to bear well. We often meet with such indications of the inheritance of undesirable peculiarities. Numerous statements may be found in regard to the increasing pre- dominance of staminate over pistillate blossoms. One of the earliest is the statement by Knight, that melons and cucumbers at higher temperatures without sufficient light almost always produce only stamens. Manz’, in his experiments, comes to the conclusion that in monoecious as well as in dioecious plants drought favors the development of male plants, while moisture and good fertilization favor female plants. It is said that male - plants can be made to bear perfect blossoms by removing whole branches. This might then indicate that the nitrogen taken up by the roots is now dis- tributed among a lesser number of blossoms and thus better nourishes these. 1 Oberdieck, Deutschlands beste Obstsorten, p. 9 footnote. Leipzif, 1881. 2 Zacharias, E., Uber den mangelhaften Ertrag der Vierlander Erdbeeren. Verh. d. Naturw. Vereins, Hamburg, 1903. 3. Folge, XI, p. 26. 3 Prakt. Ratgeber im Obst- und Gartenbau. Frankfurt a. O., 1904, No. 10. 4 Vierte Beilage zur Flora, 1822, Vol. V (after Hoffmann loc. cit.), p. 88. 201 Conditions are similar with our fruit trees, most of which rest a year, that is to say, bear one year a smaller crop and then the next a larger one. After a heavy crop the trees are usually so exhausted that they need one year in order to store up sufficient nutritive substances for the next crop. Hoffman* mentions further that many trees (the horse chestnut and the Scotch Pine) exhibit a normal alternation of sexes, since they bear staminate flowers one year and perfect ones the following. The increase of carpels in the giant poppy (Papaver somniferum forma polycarpica monstrosa) occurs only in the most vigorous plants. During his travels Karsten? found that the palms growing in swamps and damp woods, as a rule, bear perfect blossoms, but become polygamous again from a lack of nutrition. The genera growing on dry cliffs or arid plains have ordinarily but not naturally separated sexes, and these bear staminate and pistillate flowers on separate branches. At the beginning of the dry season the fruit ripens, requiring a great deal of nutritive material, and then only staminate flowers develop; while after the dormant period, at the beginning of the rainy season, pis- tillate blossoms are formed in great abundance. Cugini® found in starved plants of maize, which he obtained by heavy seeding, that various individuals bore only staminate flowers. De Vries* was also able to demonstrate the inheritance of sterility in the case of maize. He took seeds from plants in which the pistillate inflorescences were entirely wanting or extremely weak and obtained in the first year 12 per cent. of such imperfect plants. The sowing of the following year yielded 1g per cent. of sterile plants. A case described by Muller-Thurgau’® shows that aside from nitrogen hunger sterility can often be due to a lack of moisture alone. He found the stigmas on fruit trees so dry that the pollen grains could not germinate. In comparative test experiments with pears, trees which had been abundantly watered during the time of blossoming exhibited an evident increase in yield. Not only did numerous blossoms on the unwatered trees fall, shortly after the time of blossoming was past, but even the young fruits, when about the size of cherries, fell in strikingly large numbers. On trees standing in dry places, usually one fruit remained to each umbel, while in the case of water- ed trees, on an average, three developed. But sterility occurs even with good pollen and with stigmatic conditions favorable for germination. Waite® in his experiments on pear blight kept insect visitors away from the flowers and found that the fruit set to a very small extent. Further investigations convinced him that certain varieties of pears and apples cannot be fertilized at all by their own pollen (nor by that from other individuals of the same variety), but that the pollen from an- Bot. Zeit. 1882, p. 508. Linnaea, 1857, p. 259. Cugini, Intorno ad un anomalia della Zea Mays. cit. Bot. Centralbl. 1880, p. 1130. de Vries, H., Steriele Mais als erfelijk Ras. Bot. Jarbook II, p. 109. Ill. Jahresber. d. Versuchsstat. Waidensweil. Ziirich, 1894, p. 56. Cit. Galloway, B. T., Bemerkenswertes Auftreten einiger Plflanzenkrankheiten in Amerika. Zeitschr. f. Pflanzenkrankh, 1894, p. 172. ant O&O ND 292 other variety was necessary for this. This would explain the observed sterility in large fruit orchards composed of a single variety. Ewert! acknowledges that self-sterility has been determined for many species, but is of the opinion, nevertheless, that large plantations of only one variety do not fall behind those made up of mixed varieties, because cross- pollination will be secured promptly by honey and bumble bees. The setting of the fruit fails only if, because of unfavorable weather, the insects are unable to fly. According to our theory there should also be noted in this connection the alternation between chasmogamic flowers (sterile with large petals), and cleistogamous flowers (fertile with aborted petals). With E. Loew’, we perceive in these conditions no mutations in de Vries’ sense, but simple variations which depend on the form of nutrition. Goebel found that cleistogamous flowers formed earlier and he was able, by keeping them dry and exposed to abundant sunshine, to force violets which had previously borne cleistogamous flowers, to form chasmogamic blossoms in July, which is a very unusual occurrence at that time of year. The alternation was called forth by the postponement of the use of the plastic food material at hand. The cleistogamous bud cannot develop with a lack of moisture and abundance of light and the plastic building materials then remain at the disposal of later produced blossoms. Since in these the pistils are rarely formed and do not mature, the material is free for the especially vigorous development of the petals which need the light. SEEDLESS FRUITS. Sterility is often connected with the appearance of seedless fruits, and can in the same way become a peculiarity of the variety. In a new American variety of apples (the “Wonder of Horticulture”) this charactistic has recently been considered an especial recommendation of the variety*, since the blossoms yield fruit without having been fertilized. In this way, the harmful agents threatening other varieties at the time of blossoming, such as frost, mist, rain, drought, poor insect pollination, ete., are avoided. The new variety has no corolla and to this fact is attached the hope that blossom pests and other insects, which would be attracted by the petals, may spare such flowers. Seedless varieties of fruits, i. e., those in which poorly matured seeds are found, have been known from the earliest times as, for example, the pear “Rihas Seedless,’ (“Rihas Kernlose’) and the Seedless Father Apple (““Vaterapfel ohne Kern”) It is said that it frequently happens that vari- eties free from seeds appear from grape seedlings, unfortunately dis- tinguished, however, by their small size and the great hardness of the grapes. 1 Ewert, Welche Erfahrungen sind gemacht in bezug auf geringere Frucht- barkeit, etc. Proskauer Obstbau-Zeitung, 1902. 2 Loew, E., Bemerkungen zu W. Burck’s Abhandlung iiber die Mutation als Ursache der Kleistogamie. Biol. Centralbl. XX VI, 1906, Nos. 5-7. 3 Janson, A., Der kernlose Apfel. Gartenflora, 1905, p. 490. 293 The production of seedless fruits is mentioned often in the more recent works. Kirchner!, who also cites Waite’s* observations, declares that typically and normally developed fruits are obtained only by crossing with the pollen of a different variety. The largest fruits are always produced by cross-pollination. Pears produced by self-pollination developed at times almost no seeds. The flowers exposed to the visits of bees, or artificially cross-pollinated, on the contrary, yielded fruit with abundant healthy seeds. Thus it would be advisable to grow a mixture of varieties. In opposition to this theory, Ewert*, even in his latest papers, holds to his point of view, advocating for practical reasons the cultivation of a single variety in blocks. In regard to seedless grapes, we will refer to the investigations of Miller-Thurgau*. Ewert emphasizes, in reference to seed-bearing fruits that, for the setting of the fruit, the amount of organic material at the disposal of the individual blossoms is of especial importance. In various cases a better nutritive condition for the individual blossoms can be obtained artificially by ringing, since they vary in their development. The pistils are either greatly developed and project as much as one centimeter above the anthers (protogyny), or both sexual organs are equally long (homog- any), or the pistils are shorter than the stamens (protandry). , Ewert’s experiments do not confirm absolutely the conclusion that the stronger pro- togny is developed, the more the blossom, which is consequently self-sterile, demands the pollen of some other variety, and, conversely, the more homog- any and protandry manifest themselves, the greater the possibility of self- pollination. It is evident that the organic nutriment is carried first of all to those fruit buds, in which cross-pollination has made seed formation possible. In comparing fruits containing seeds and those without seeds on the same tree, the seedless ones are smaller and are often malformed. If seedless fruits alone are produced on a tree, by keeping away all foreign pollen, they attain the same size as do those bearing seeds. Probably fruits can also be pro- duced without the action of pollen. In some cases fruits can be observed in which the core does not exist, or is scarcely indicated. In reference to the former, Burbidge’ reports that pears without seeds and core represent very solid parenchymatous fruits, said to be larger, better flavored and’ possessing a better keeping quality than pears containing seeds. I, myself, some years ago, received a branch of pears, one specimen of which is given half-size in Fig. 36. The fruits were perfectly hard and 1 Kirchner, O., Das Bliihen und die Befruchtung der Obstbiume. Vortrag. Ref. Zeitschr. f. Pflanzenkrankh, 1900, p. 297. 2 Waite, Merton B., The pollination of the pear flowers. Washington, 1894, U. S. Dept. Agric. Bull. 5. 3 Ewert, Bliitenbiologie und Tragbarkeit unserer Obstb’iume. Landwirtsch. Jahrbiicher, 1906, p. 259. 4 Miiller-Thurgau, Folgen der Bestiubung bei Obst- und Rebenbltiten VIII. Ber. d. Ziiricher Bot. Ges. 1900-1903. 5 Royal Horticultural Society of London. Cit. Bot. Centralbl. 1881. Vol. VIII, Deol; 294 healthy until injured by the autumn frosts. At A we see a normal woody branch; at B a branch, the terminal bud of which is swollen up to a seedless fruit; at C is shown a fruit grown from a lateral bud with primordia of core; ” is the scar of a fallen leaf; s an undeveloped lateral bud; k a per- fectly matured leaf bud on the fruit stem; sch scale-like leaf on this stem; at g are the normally extended vascular bundle fibres, arranged about the compartments of the core (f) enclosing the rudimentary ovules. At c are visible the dried remains of the calyx and at st the branches of the style. This case differs from the one described by Burbidge and from most others described as yet, in that the fruit is the product of the buds of the current, not of the previous year. It is not rare for the pear to bear occasional fall flowers. They can, in fact, arise from buds set the previous year, as is often stated, but, as yet, I have had opportunity to observe only such blossoms as were produced on the branches of the current year, ma- tured in the summer, a fact which could be determined easily from the wood ring of the branch bearing the fruit. The proleptic blossoms had, with the relatively scanty nutritive supply and the short time granted them for development in the fall, naturally little opportunity to develop the parts of the cortex into well fla- vored fruit flesh. This explains, on the one hand, the lack of size and, on the other, the lack of flavor of the pears here described. If the fruit buds had not been stimulated by the un- usually increased supply of water at the then autumnal season, they would probably have yielded perfectly normal fruits the following year. Fig. 36. Seedless Pear. While the fruit remained seedless in this case, because in the proleptic development the accumulated building materials are insufficient, other cases also occur in which enough material is present, but is utilized in some other way because of the destruction of the normal embryo. Thus Muller- Thurgau! states that pears whose carpel layers had been destroyed by a late frost, produced fruit then exhibiting in place of a core a hollow chamber in which tissue excrescences had grown out from the side wall. The appearance of seedless fruits is, therefore, to be treated primarily as a question of food supply. The organic building substances are not 1 Miiller-Thurgau, H., Eigentiimliche Frostschaden an Obstba’éumen und Reben. X-XII. Jahresb. der Deutsch-schweizer. Versuchsstat. Wadensweil, 1902, p. 66. 295 sufficient to nourish the embryo, no matter whether this arises from a fail- ure of the stimulus of fertilization, from the poor position of the various blossoms, from the exhaustion of the tree as a result of a previous heavy crop, or from a proleptic development of a fruit bud. In consideration of the fact that seed-containing fruits develop better than seedless fruits from the same tree, it is more advisable agriculturally and horticulturally, as long as seedless varieties cannot be cultivated with absolute certainty, to en- courage the possibility of seed formation. Even if Ewert has proved that although in orchards of one variety the number of seedless and poorly seeded fruit is large, the fruits producing seeds still predominate, on which account he has asserted that “pure planting” is advisable, yet tor the present we would give preference to mixed planting. The practical disadvantages in regard to the protection and harvesting of varieties growing and ripening differently may be decreased by cultivating each variety in rows. In avenues of trees at all times that variety which is most nearly ripe should be especially watched. THE BEHAVIOR OF WEAK SEEDS. The causes, which have affected the failure, or the poor maturing of the seeds in seedless fruits, have been felt more or less in other cultivated plants, so that we must also consider the behavior of poorly developed seeds. The scanty amount of nutriment must manifest itself in the specific gravity and, in this connection, Clark’s' experiments show that seeds of low specific gravity do not germinate at all while those somewhat heavier germinate sparsely and often produce weak plants. The highest percentage of germi- nation is found in seeds with the highest specific gravity. According to Hosaeus’* experiments, normal plants can be produced even from immature, i. e. specifically light, seeds by carefully providing very favorable conditions. But the death rate is considerably larger in compari- son with that of normal seeds. This refers especially to the use of grain, for example, which had necessarily been harvested in the milk stage. Some- times the immature seeds undergo a sufficient subsequent ripening, outside of their fruit covering, and can then, under certain circumstances, germi- nate more quickly than the incompletely matured ones. According to Kinzel*® this may occur in parasites of silk varieties (Cuscata) and is very well worth consideration in combatting them. At times, with a poor quality of seed, a careful soaking is beneficial in order to shorten as much as possible the time the seed lies in the soil before its germination. Immature seeds especially decay much more quickly, par- ticularly in heavy soils. But this soaking of the seed is disadvantageous because the seed must lie longer in the soil ungerminated if a period of 1 Clark, A., Seed selection according to specific gravity. New York Exper. Stat. Bull. 256. 1904. 2 Deutsche Landwirtsch. Presse, 1875, No. 4. 3 Kinzel, W., Uber die Keiming halbreifer und reifer Samen der Gattung Cus- cuta, Landwirtsch. Versuchsstat. 1900. Vol. 54, p. 125. 296 drought occurs, than if it had been sown naturally. Zawodny' has proved this experimentally for cucumbers. In this connection reference must be made to the already discussed interruption of germination by drought. DROPPING OF THE FRUIT. Besides the dropping of pears already mentioned, which Muller-Thur- gau observed as the result of drought at the time of blossoming, fruit-bearing trees have an annual house cleaning during which poorly nourished blossoms or young fruits are dropped. The flowers developing last at the tips of the inflorescences, especially those at the ends of branches, are the ones cast off. There is not enough plastic nutriment at hand for development. The fruits nearest to the source of supply, the trunk axis, take up the nutritive sub- stances at the expense of the organs further out. For fruits cultivated on trellises, these nutritive relations can be regulated artificially, since a large part of the unfavorably placed specimens can be removed with shears soon after the fruit is set. In growing fruit for market very exact consideration must be given the moisture requirement, especially that of peaches and apricots. When the stone begins to harden, the most water is needed, and the dropping is often caused by a single dry period. Before and after this stage of development, however, more care must be used in watering, since otherwise sprouts are produced too early, which divert the material necessary for the maturing of the fruit. Then, at a later stage, the fruit will drop from a lack of nutri- ment, or, at least, be injured by it. We have already mentioned in previous chapters that mature fruits may drop because of a late dry period, and it is now necessary to recall that fruit, injured by a late spring frost, is sometimes found in great quantity on the ground. All causes which lead to the sudden lost of function of an organ ultimately effect its dropping. THE DRYING OF THE INFLORESCENCES ON DECORATIVE PLANTS. This phenomenon is often met with especially by amateur growers of potted plants. Aside from the effect of dry air which will be treated later, and the dryness of the soil already mentioned, there are two circumstances that come under consideration here. Both represent a starving of the blos- som buds. In one case it is actually a lack of nitrogen which manifests it- self when the plants stay in the pots too long, in the other case it is a lack of food for the blossoming organs, since other organs have taken it. Our azaleas and camellias serve as the most usual example of the latter case. Plant lovers complain very frequently that the plants which have a great many buds do not open their buds in the house. In azaleas the buds become dry, in camellias they fall. In both cases fresh, rapidly and vigor- ously growing shoots develop prematurely directly under the blossom buds. 1 Zawodny, J., Keimung der Znaimer Gurke. Cit. Bot. Jahresber. 1901, Part II, p: 236, 297 In this premature breaking forth of the young branches lies the cause of the “fall of the blossoms.” The error in treatment is that the plants are kept too warm and moist and insufficiently lighted for the given stage of their development. While the flower, to be sure, needs warmth and atmospheric humidity for its development, too great moisture in the soil injures it. This incites the leaf buds near the blossoms to a premature exfoliation and these attract the current of nutritive substances to themselves, squeezing out the functionally weak blossom buds. In forcing bulbs, especially tulips, we also find such conditions of star- vation of a flower bud resulting from too vigorous a development of the vegetative organs. In the newer cultivated varieties we often find that the flower stalk is not leafless, but has one or two leaves borne on clearly marked nodes. In such examples, the bud is so weak that, when forced in winter, it cannot develop at all, but dries up, because of preponderating leaf growth, resulting from the excess of moisture and warmth. An experiment made with Veltheimia glauca may be cited as an ex- ample of the drying up of the flower buds, due to a lack of nitrogen. A vigorous double bulb had been divided several years previously and each daughter bulb had bloomed regularly every winter after this division. When later one of the bulbs was not transplanted, while the other was set in new, rich earth, the inflorescence developed earlier in the former, to be sure, and was more slender, but the flowers dried up before being completely formed. This plant was now given hornshavings as a source of nitrogen, without changing the soil in the pot. In the following year the inflorescence appear- ed to be more vigorous and the flowers more numerous; part of them de- veloped and became colored, but not so deeply as those from the bulb which had been transplanted each year. It is well known that a supply of nitrogen will increase the product of agricultural plants. THE FORMATION OF THORNS. The formation of thorns, i.e., the replacing of a bud on the end of a shoot by a woody, pricking tip, may be perceived as an indication of the lack of nitrogen. A comparison of figures 37 and 38 (cross-sections of Rhamnus cathartica) shows what changes have taken place. The tissues, indicated in both figures by the same letters, should be compared. We see that in the formation of thorns, the thick-walled elements gain the upper hand, and that even the parenchyma cells of the bark and of the pith have unusually thick walls. A young branch ending in a thorn, can at times form lateral buds at its base, if enough nitrogen is still present for the formation of the meriste- matic centers. But these lateral axes begin to assume thorn-like character- istics early in their development. Ducts may be found as far along on the thorns as leaf buds can be recognized and even for a distance beyond them. These usually disappear in the apical region. The elimination of thorns is especially desirable horticulturally because, for example, the thorns of such plants as Crataegus, Pirus communis, Fig. aw, MS RU : LIU VA A Z i pO A ew ‘el 2), ES Cap) om NSS ea Ct_\ Ae 2D Sere nes cuuy S O\ VAN) Muy ou As 7) aisha ) : ile branch of Rhamnus cathartica. -------- # Cross-section through a one-year old Prunus spinosa, etc., are very apt to injure people working among them. The transfor- mation of the thorns into nor- mal leafy shoots, ending with a terminal bud, results from pruning and transplanting the wild plants to rich, loose, well drained soils. c. CHANGES IN PRODUCTION DUE TO A LACK OF POTASSIUM. By way of introduction, reference must be made once more to the fact that a lack of potassium in the soil condi- tions a lack of moisture. Holl- rung’s' recent experiments: have proved that a soil mixed with potassium salts contains much more moisture than the same soil under otherwise similar conditions. The potassium enters the plant in the form of potassiuin nitrate, sulfate and phosphate, chlorid or even silicate. In the plant it may be found in combination with organic and inorganic salts and especially in the tissues in which carbo- hydrates may be.found. Hell- riegel and Wilfarth proved ex- perimentally that the amount of carbo-hydrates deposited as reserve substances (starch and sugar) in potatoes, grain and sugar beets, depends directly on the amount of potassium supplied. Thus it is. evident. that a Jack of potassium must manifest 1 Hollrung, Vortrag im An- haltinischen Zweigverein fir Zuckerriibenkultur. Blatter f. Zuckerrtibenbau 1905 p. 76. a Cuticula, 6 Epidermis, c Cork layer, d Phellogen (cork cambium), e Collen- chyma, fand/! Bark parenchyma, g and eg! Bast bundles, 2 Secondary bark, z Wood, and on its periphery, the cambial zone, k Pith, m pith disc. (After Dobner-Nobbe) 299 itself in a scarcity of the reserve substances. Besides this, the lack of potassium explains also the fact, already observed, that shoot formation is retarded, since the cellulose, necessary for the formation of the parenchyma, is likewise a carbo-hydrate. Without potassium, the plant becomes green, to be sure, but does not grow much beyond the amount of material furnished from the seed. All other nutritive material, therefore, can not have been used (law of the minimum). According to Nobbe’s studies, if the very valuable com- ‘¢& pound, potassium chlorid, was given to potassium hungry plants, even after they had lain dormant for months, an increase in growth was produced in two or three days. The formation of starch began immediately’. An addition of potassium becomes fully effec- tive, however, only when it is not rendered inactive by calcium. Ad. Meyer? emphasizes the especially favorable action of potassium chlorid, but he found this con- siderably weakened when calcium bi-phosphate was also present. With sugar beets potassium chlorid, as well as calcium chlorid, when used alone, worked very well, but not if added simul- taneously. Hellriegel found in grain that 1( with a scanty potassium supply, & LE the green parts matured at the @))NS VE expense of the kernels. This is = ( IC) ‘) not the case with a lack of nitro- : gen; the plants then develop com- Fis. 38. as Steer Mee ge thorn of pletely but remain small. In trees ° 1 a0 Explanation of letters as in Fig. 37, only here the phello- a continued lack of potassium gen (d) and secondary bark (/) are lacking. They appear always leads toa weaker develop- transformed into permanent cells. (After Dobner-Nobbe) ment of the end shoots and finally to “tip blight’ and Janson®* states that he has cured this disease by a direct addition of 40 per cent. potassium salt. Naturally tip blight can be produced by very different causes, and on loamy soils especially other causes must often be sought primarily. 1 Nobbe, Schréder and Erdmann, Die organische Leistung des Kaliums in der Pflanze. Landwirtsch. Versuchsstat. XIII p. 321. 2 Jahresber. f. Agrik. Chemie 1880 p. 269. ; : 3 Janson, A., Kalidtingung gegen die Spitzendtirre. Prakt. Ratg. f. Obst- und Gartenbau 1905 No. 38, 300 Agriculturally worth consideration is the fact, confirmed experi- mentally’, that with a lack of potassium, as contrasted with complete nu- trition, a larger part of the nutritive substances taken up (excepting the phosphoric acid) will wander back into the soil at the time of ripening. This was observed, at least, in summer wheat, barley, peas, and mustard. Potatoes formed an exception. The manifestation of a lack of potassium in fungi is very interesting. Molliard and Coupin? found in Sterigmatocystis nigra a malformation of the conidia which were produced only very exceptionally and matured incom- pletely. As under other conditions due to starvation, the conidia germi- nated at once, but their contents grew into a chlamydospore form. The most important question for agriculture is, whether positive ex- ternal characteristics may be found which indicate with certainty the lack of potassium? We owe the most important experiments along this line to Wilfarth and Wimmer*, who set up comparative cultures of sugar beets, potatoes buckwheat etc. They tested also for scarcity of nitrogen and phosphoric acid and found that with a lack of nitrogen leaves took on a light green to yellowish coloration and finally dried up with a light brownish yellow color. With a lack of phosphoric acid they were colored a deep, dark green, cor- responding to the occasional excess of nitrogen, and in extreme cases black- ish brown spots were formed at the edges and later distributed over the entire surface of the leaf, which sometimes had a reddish color at first. Finally followed a drying up accompanied by a dark green to a blackish brown coloration. If, however, sufficient potassium lay at the disposal of such starved plants, abundant quantities of starch and sugar were formed in spite of this; even with a lack of nitrogen, this process seems to be in- creased rather than decreased. If, however, in an otherwise normal nutri- tive supply, the potassium is lacking, the above-mentioned increased forma- tion of straw in grain as against the formation of kernels becomes manifest. Under these conditions the amount of green growth in edible roots, or tuberous plants, was increased in proportion to the containers of the reserve substances, which possessed appreciably less carbo-hydrates than with a lack of nitrogen and phosphoric acid. Since the plants use first of all the potassium supply in building their vegetative skeleton, they retain longer, by their habit of growth, the appear- ance of normally nourished plants with a lack of potassium than with a lack of nitrogen and phosphoric acid, but then the internodes are shortened and the leaves curl upward convexly. At first near the leaf edges and then later scattered over the whole surface of the leaf, appear yellowish spots which rapidly turn brown or often change to white, while the petioles and 1 Wilfarth, ROmer and Wimmer, Uber die N&ahrstoffaufnahme der Pflanzen in verschiedenen Zeiten ihres Wachstums,. cit. Centralbl. f. Agrik.-Chemie 1906 p. 263. 2 Molliard et Coupin, Sur les formes teratologiques du Sterigmatocystis nigra privé de Potassium. Compt. rend. 1903. CXXXVI p. 1659. 3 Wilfarth, H. W. and Wimmer, G. (Ref.) Die Kennzeichen des Kalimangels an den Blattern der Pflanzen. Zeitschr, f, Pflanzenkrankh. 1903 p. 82. 301 veins together with the immediately adjacent tissue remain green. Finally the leaves dry up, beginning usually at the edges, with a dark brown color (see the adjoining Fig. 39). Flower and fruit formation are scanty. With a lack of potassium, not infrequently, individual plants go to pieces prematurely’, while, with a lack of nitrogen and phosphoric acid, even the smallest plants can be maintained until the end of the time of growth. Of especial importance is the observation of the above-named authors, that the roots as well as the tubers of plants grown with a lack of potassium tend very easily to decay and that plants lacking any nutritive substance are always more predisposed to attack from animal and vegetable parasites. Von Feilitzen? made the same observation on timothy grown on moors. It was attacked by fungi only after it had been weakened by a lack of potas- sium. He noticed in clover that the lots sown without potassium, or with a slowly soluble compound of it, were “scorched” as if grown on poor sandy soil, after long periods of drought. When experimenting with different fertilizers, Moller found that with a lack of potassium the seedling plants of the Scotch pine had less growing power, their needles had a faded appearance. Valuable as are these attempts to find positive characteristics due to a lack of potassium, I still think that for a long time we will have to make use of these characteristics only with great care in diagnosis. In the first place, we do not know whether the same characteristics always,—1. e. with all vari- ations of the factors of growth,—become visible in the same species. In the second place, we still know too little of the phenomena of starvation which make themselves felt with other nutritive substances. In the third place, the influence of injurious gases at times gives such deceivingly similar effects, aside from parasitic attacks, that it might be difficult to draw definite con- clusions from the changes in habit alone. It should be taken into consider- ation that almost all injuries to the leaf manifest themselves first in the regions lying farthest away from the veins conducting water, hence the fre- quent beginning of the diseased condition at the edge of the leaf or in the middle of the intercostal areas, upcurved between the larger veins. d. CHANGES DUE To A LACK OF CALCIUM. It is well known that the plant uses calcium as stiffening for the cell walls and as a means for combining the poisonous oxalic acid produced. In the phenomena of disease, the fact that an excess of oxalic acid can re- dissolve small amounts of calcium oxalate is important*. The calcium oxa- late produced is re-dissolved only in a few cases*. Usually the organism | } 1 Compare also, v. Seelhorst, Die durch Kalimangel bei Vietsbohnen (Phaseolus vulgaris nanus) hervorgerufenen Erscheinungen. Zeitschr. f. Pflanzenkr. 1906, p. 2. 2 vy. Feilitzen-Jénk6éping, Wie zeigt sich der Kalimangel bei Klee und Timothee- gras? Mitt. d. Ver. z. Ford d. Moorkultur. 1904. No. 4. p. 41. 3 Wirtz, Dictionaire de chimie II, p. 647, cit. by de Vries in Landwirtsch. Jahrb. 1881 p. 81. 4 Sorauer, P., Bertrage zur Keimungsgeschichte der Kartoffelknolle. Berlin. Weigandt & Hempel. 1868, p. 27, and de Vries, H., Uber die Bedeutung der Kalkab- lagerungen in den Pflanzen. Landwirtsch. Jahrb. v. Thiel, 1881, p. 80. Fig. 39. Lack of potassium. I, Deformed tobacco leaf, resulting from a lack of potassium, with partially split, brown edges; only the veins are still green while the intercostal fields appear discolored yellow to white; 2, Leaf of a normally nourished potato plant; 3, that of one starving for potassium. In this the leaflets stand closer to one another and are curled under. The places drawn in light are yellowish, the intercostal fields are flecked with brown, as also the edges of the leaves; 4 and 5, leaves of the buckwheat plant with spots which are yellow- ish, then brown, and finally white. (After WILFARTH and WIMMER). 393 does not possess the ability of re-dissolving the calcium already deposited in old tissues in appreciable amounts and transporting it where it can instantly become effective for new structures, when there is a lack of calcium. At least the experiments of Bohm', Raumer and Kellermann’ and Benecke* prove that no calcium, or very little passes from the containers of reserve substances into the young tissues when the plants are grown in distilled water, in solutions free from calcium, or in quartz sand. The fact that no calcium is necessary for the formation of starch itself has been proved by Bohm. He found that primordial leaves free from starch with shrivelled petioles became filled with starch when grown without lime, but under otherwise favorable conditions. In order to dissolve the reserve substance and to transport it chemical combination with calcium is necessary, for an investigation of plants grown in media lacking calcium proved that the organs (leaves, cotyledons) had not given up all the starch, the leaf body or the adjacent internodes retained considerable quantities, while the young plant starved to death despite its sugar content. My own experiments‘ also led to the conclusion that the plant needs new mineral substances originating from the solution in the soil, even at a time when it is working up the re- serve material into cellulose, etc. Thus in the germination of seeds an addition of calcium acts bene- ficially ; in fact, it often seems necessary. The statement that calcium 1s disadvantageous for germinating seed® may have arisen from a use of too highly concentrated solutions. Loew and May declare that definite excess of calcium in the soil over the magnesium content can produce starvation symptoms in the plant (see Lack of Magnesium). An earlier assertion of Dehérain and Breal® that, with a lack of calcium the plants can better utilize the lime stored in their bodies, if the temperature is raised, has not held’. Molisch, as well as Portheim, has also proved the error of these statements®. Among the older observers’, Nobbe describes the phenomena due to a lack of calcium in water cultures. Buckwheat, peas, Robinia, etc., grew but little beyond the germinating stage. The pale leaves exhibited spots, simi- lar to those produced by the action of acid, which dried up gradually, and then the petioles often broke. On conifers, the tips of the first year needles became yellow to brown. 1 Bohm, ther den vegetabilischen Nahrwert der Kalksalze. Sitzungsber, d. k. Akad. d. Wissensch., Vol. 71, 1875, p. 287 ff. 2 y. Raumer and Kellermann, Uber die Funktion des Kalks im Leben der Pflanze, Landwirtsch. Versuchsstationen XXV, 1880, Parts 1 and 2. 3 Benecke, W., tiber Oxalsiurebildung in griinen Pflanzen. Bot. Zeit. 1903, Part 5. 4 Sorauer, Studien itiber Verdunstung. Forsch. auf d. Geibiete d. Agrikultur- rhysik, 1880, p. 429. 5 Windisch, R., Uber die Einwirkung des Kalkhydrates auf die Keimung. Landwirtsch. Versuchsstationen. 1900, p. 283. 6 Annales agronomiques, Vol. IX, 1883, No. 52. 7 Kriiger, W., und Schneidewind, W., Zersetzungen und Umsetzungen von Stick- stoffverbildungen im Boden durch niedere Organismen, ete. Landwirtsch Jahr- biicher, 1901, p. 633ff. 8 y. Portheim, L., Uber die Notwendigkeit des Kalkes ftir Keimlinge, etc. Cit. Bot. Jahresber. 1901, Section II, p. 141. 9 Ddobner-Nobbe, Botanik fiir Forstméanner. 1882, p. 314. 304 Recent cultural experiments with grain, buckwheat and Elodea cana- densis in nutrient solutions, free from calcium, showed that after a five day retention in a solution free from calcium, the root growth became less and later ceased entirely. The roots turned brown and the root cap died. Pe- culiar, brownish spots were found on the leaves, which soon went to pieces. The content in acid potassium oxalate and in starch was greater than in normal plants. The death of plants, in a nutrient solution without calcium, has been traced by Loew to a poisonous action of the magnesium salt. Bruch’s cultural experiments with magnesium sulfate, nitrate, carbonate, and phosphate in aqueous solutions showed that the roots, to be sure, soon stopped growing, but the aérial parts developed further perfectly normally and even blossomed. Wheat plants in solutions free from calcium and magnesium died far more quickly than those in solutions lacking only the calcium. Amar? observed the absence of calcium oxalate crystals in those leaves which were formed after the plants had been put in a solution free from calcium. A further insight into the conditions due to a lack of calcium is given by Krtiger and Schneidewind through Schimper’s statement that, when the calcium is removed, all the symptoms of poisoning from an enormously large content of acid potassium oxalate are indicated. In Phaseolus these authors, to be sure, could prove no especial increase of a strong organic acid. They succeeded, however, in keeping the plants until all the reserve substances had been used up by painting dying seedlings with a calcium solution either on the kypocotyles or at the place where death usually begins. This sub- stantiates Bohm’s observations that seedlings of the scarlet-runner bean take up calcium as well as water through the outer skin of the petioles and leaves. The experiments of Moisescu® confirm the above observations. He found in different cultures in nutrient solutions that those seedlings had be-_ came affected earliest and most extensively which had grown in solutions free from calcium. In Platanus orientalis, the leaves of which partially became brown and dry along the veins, it was found that the diseased ones contained twice as much acid as the healthy ones. Gloeosporium nervisequum in- fested the diseased leaves. On this account it must be assumed that the parasite named attacks only weakened leaves. This weakness would con- sist here of “Calcipenuria,” that is to say, a lack of calcium. In the author’s opinion, not enough calcium was present to convert the excessive potassium oxalate into calcium oxalate. . Besides cultural experiments of this nature, a large number of practi- cal results point to the injuriousness of calcium poverty. At least we find in many cases a cessation of the phenomena of disease after an addition of 1 Bruch, P., Zur physiologischen Bedeutung des Calciums in der Pflanze. Landwirtsch. Jahrb. 1901. Suppl. III. p. 127. 2 Amar, Maxime, Sur le réle de l’oxalate de calcium dans la nutrition des végétaux,. Annal. sc. nat. bot: 1904. XXX, p. 195. 3 Moisescu, N., Hin Fall von Calcipenuria, Zeitschr. f, Pflanzenkr. 1905, p. 21. 395 calcium. In this, the calcium may often act beneficially on the constitution of the soil and often directly on the composition of the cell sap. According to our explanation of the matter, a considerable number of cases of disease exist which are called forth directly by nitrogen excess, and for which the ad- dition of calcium and phosphoric acid remains the only effective remedy. In the division “Enzymatic Diseases,’ we will also have to consider the beneficial action of calcium fertilization. There we will also touch upon the subject of the over-abundant formation of acid in the plant which cer- tainly sometimes influences unfavorably the mode of production. Thus, for example, with a lack of calcium in the soil, the sap of sugar cane con- tains a great deal of acid and but little sugar’. We will mention later special cases of oxalic acid poisoning. e. CHANGES DUE To A LACK OF MAGNESIUM. Plants grown in a nutrient solution lacking magnesium often live longer _ than when the nutrient solution does not contain calcium. It might be con- cluded from this that the plant is able more easily to remobilize the mag- nesium compounds already deposited in its tissues and to make them partially accessible again for the young organs. If the grain becomes diseased slowly from magnesium hunger, the leaves are a light green and appear limp, but not directly wilted. From the beginning it is possible to imagine a very considerable effect on the formation of seeds, if one considers that, for ex- ample, the globoids enclosed in the protein grains may be assumed to be calcium and magnesium compounds of, a double phosphoric acid. In reality, with a lack of magnesium, there is a decrease in the formation of fruit, as stated by Nobbe*. He gives the following symptoms. The leaves become pale in color, with yellow to orange red spots here and there. The chlorophyll grains are pale yellow green and contain, as a rule, small amounts of starch. Diminished cell division is noticeable in the epidermis. Nobbe found that plants grown with a lack of magnesium correspond to those from nutrient solutions free from nitrogen, in that red spots are present on the petioles and the leaves fall prematurely. The latter character- istic may well be present in all starved plants, since the young organs ex- haust the older ones when the supply of nutriment is insufficient. Moller® also observed an orange red coloring in his cultivations of Scotch pine seedlings with a lack of magnesium. He says that the needles in October had bright orange yellow tips but farther back passed through a bright red zone into a normal green one. The discoloration appeared when the seedlings had been given magnesium in the second year. Ramann analyzed the orange tipped needles of two-year old Scotch pines and found that these contained 0.2791 per cent. magnesium (calculated on the dry weight), while the adjacent normally green specimens showed a content of 0.6069 per cent. 1 Semler, Tropische Agrikultur. II Edition. Vol. III, p. 236. 2 Débner’s Botanik fiir Forstminner, edited by Nobbe. 4th Edition, p. 315. 3 Moller, A., Karenzerscheinungen bei der Kiefer. Sond. Z. f. Forst- und Jagd- wesen, 1904, p. 745. 306 In regard to the action of magnesia, Loew and May' have expressed the opinion that a definite quantitative proportion between soluble calcium and magnesium compounds is necessary for favorable growth (corres- ponding approximately to their molecular weights, i.e. 5 to 4). Magnesium in the soil in great excess over calcium is injurious. Plants which in so far lack magnesium, as that calcium is present in excess, exhibit symptoms of starvation. A small excess of calcium arrests the poisonous action of the magnesium. In the use of fertilizers containing magnesium, calcium should also be given at the same time. This advice should be taken to heart. Even if plants can well endure magnesium, and even actually need it, any excess is certainly injurious, as has also often been proved in fertilization with raw potassium salts. f; CHANGES DUE To A LACK OF ‘CHLORINE: It should perhaps be assumed that chlorine and calcium are antagonistic in plants. Mayer’s conclusion, mentioned under potassium, that the action of potassium chlorid is weakened by calcium and, conversely, would indicate this. In the same way Knop® found that less calcium is taken up when the nutrient solution contains chlorine, and the calcium did not appear to be represented in any corresponding way by potassium or any other base. Thus the chlorine compounds (by the retention of the calcium) cause an essential increase in the acid content of the plant sap. Since, among the acids ab- sorbed, the phosphoric acid predominates, Knop thinks it permissible to ascribe to this acid the greater fertility with a use of nutrient solutions con- taining chlorine, which was observed by Nobbe. Accordingly one would like to explain the process thus,—the chlorine which accumulates* in greatly different quantities in the plant body, according to the amounts offered the roots, can increase the transportability of the phosphoric acid, since it clecreases the absorption of calcium and thus prevents the appearance of the phosphoric acid in the slowly soluble form of calcium phosphate. If the phosphoric acid, co-operating in the formation of the proteins, reaches very easily the meristematic areas of the growing tips, an abundant forma- tion of cytoplasm occurs together with cell increase and, in connection with this, a plenteous streaming of the carbo-hydrates for the protein regenera- tion. Accordingly, vigorously growing shoots with but little stored up reserve substances will necessarily be found in plants, fertilized with chlorine. Actually, the many fertilization experiments show a decrease in starch ard reserve sugar in the luxuriantly growing cultivated plants. 1 Loew, O., and May, W., The relation of lime and magnesia to plant growth. U. S. Department of Agric. Bull. I. cit. Bot. Jahresber. 1991. II. p. 141. 2 Chemisch-physiologiscne Untersuchungen iiber die Erna&hrung der Pflanzve von Knop and Dworzak. Aus Berichte d. Kgl. sichs. Gesellsch. d. Wissensch. vom 23. April, 1875. Cit. Jahresber. f. Agrikulturchemie, 1875. p. 267. % Pagnoul, Sur le rdle exercé par les sels alcalin sur la végétation de la better- ave et de la pomme de terre. Compt. Rend. 1875. Vol. LXXX, p. 1010. Fertilizing experiments carried on for five years with chlorids showed for beets a fluctuation in contents from 1 to 50. In potatoes, the smallest yield in tubers coincided with the least amount of potassium carbonate in the ash but with the greatest amount of chlorides. Besides the probable increase in the transportability of the phos- phoric acid, it can be proved that chlorine has a favorable influence on the transference of the starch prepared in the leaves. According to Nobbe’s experiments, the plant starving for chlorine continues to grow, exhibits a very dark green color and gives a considerable pro- duction of substances rich in carbo- hydrates, but sooner or later,—at any rate before the time of blos- soming,—there occurs a_ peculiar change in form and _ structure. Nobbe found the dark, abnormally fleshy leaves crammed full of starch (in oak and buckwheat) rolling up, becoming brittle and dropping. The stems and petioles seem puffed up, the internodes of the stems always are shorter and many finally dry from the tips backward. If the plant reaches the blossoming stage, only scat- tered, unusually poor small fruits develop, despite the abundant starch material in the leaves. The effect of a lack of chlorine is best recognized by a comparison of a normal buckwheat plant with one grown with a lack of chlorine (figures 40 and 4I). g. Lack oF IRON AND “JAUN- DICE” (ICTER- WS). iimevexpres- sions, “jaun- dice,’ “yellow- sickness, “white- leavedness,” Fig. 40. Blossoming buckwheat plant grown in a normal ry: aes: i nutrient solution. (After Nobbe.) UatT 1 egation, 308 39 66 Id 66 “chlorosis,” “albication,”’ “‘etiolation,’ are the most common names for the condition in which a leaf loses its green coloring matter in spots, or over the whole extent of its surface. The causes for this change in color are very different, but always represent a condition of weakness. In order to survey the manifold causes of the disease, we will endeavor to group them into 1. Induced and non-transmissible conditions. (a). The discoloration attacks the whole surface of the leaf, which has matured in the light. After having been green in its young stages, the whole leaf assumes a yellowish, yellow to yellow- white color tone. Icterus or jaun- dice. Cause: usu- ally a lack of nu- tritive substances. (b). The pale discol- oration is present in the young organ and the leaves re- main in a con- dition resembling youth until their premature end. Cause: la clkion light and at times of heat (see these topics ). 2. Innate and transmis- sible conditions. Portions of the Fig. 41. Buckwheat plant grown in a solution free from chlorine. (After Nobbe.) plant show yellow to pure white spots or stripes. Those plants suffer especially in which pure white leaves appear near the ones spotted with green or all green. The spots have usually a sharp demarcation. W hite-leavedness, albication, variegation, sometimes transmissible through seeds or by grafting. Cause: probably enzymatic dis- turbances (see these). Of course there are intermediate stages between the types named, since the individual causes often work together. ' In the present division we will examine only the icteric conditions and treat them under lack of iron because, since the investigations of the Gris’, father and son, it is customary to consider jaundice as caused especially by 1 Gris, A., Ann. scienc. nat., 1875, VI ser. Vol. VII, p. 201. 309 a lack of iron. The authors named found jaundiced leaves turning green where painted with a soluble iron salt. A change to green may also be ob- served if the roots of such plants have a dilute iron solution at their disposal. The experiments on the effectiveness of the iron solution were often re- peated; as, for example, by Knop* and Sachs’, who observed in cultures of maize in nutrient solutions free from iron, that the plants remained green only as long as the reserve material from the seeds lasted. After this time, leaves developed which were green only at the tip and were already yellow at the base, until the next leaves appeared uniformly icteric. Similar dis- colorations, at first appearing in stripes, were found on mature plants which had developed normally at first, and then were placed in a nutrient solution free from iron. The blossoms then became sterile and the production in dry weight was considerably less. Frank* observed that there occurred with a lack of iron an universally noticeable phenomenon of starvation, viz., the newly produced leaves exhausted the older ones, which lost their color and died. In icteric organs, the chlorophyll grains have a normal form, but their number and size is possibly smaller and their color pale. Although the chlorophyll pigment contains no iron*, the whole nutritive condition of the chlorophyll grain will become weakened by the lack of iron. But at first the chloroplast exists in a normal form which is not destroyed until later. In this lies the difference between the phenomena of starvation and enzymatic albication. In order not to be obliged to separate the phenomena whose similar symptoms lead to confusion, we will mention here icterus due to cold. We find in cold, wet seasons a gradual yellowing in most cultivated plants, which disappears of itself with a rise in temperature. Often in spring, the leaf points of our flowering bulbs are yellow when they push out of the earth and the young leaves push out gradually with a normal green color only as the weather becomes warmer. From this transitory jaundice must be distinguished the chronic form, in which the yellow leaves always remain yellow. This may be observed if sudden great cold affects the young cells and destroys the chloroplasts. Then, in place of these, are found only fine grained yellowish groups and at times also yellow drops. These cells do not recover later. At the place of transition to the parts of the leaves which, protected by the earth, have become green, colorless, swollen and also light green chlorophyll grains which later partly turn green may be found at the place of transition to the portions of the leaf, which, protected by the earth, have become green. 1 Knop (Jahresberichte f. Agriculturchemie, 1868-69, p. 288) observed in such experiments that the iron which got into the plant could not be proved in the cell sap, and, therefore, must be present in a combined form. In 1860 (Bot. Z. p. 357), Weiss and Wiesner determined that iron occurs only in insoluble compounds and in the contents of the older cells as well as in their walls. 2 Experimentalphysiologie, p. 144. 3 Krankheiten der Pflanzen. 1895, I, p. 290. 4 Molisch, Die Pflanzen in ihren Beziehungen zum Hisen. 1892, p. 81. 310 With the action of sudden cold, lasting for several hours, Haberlandt' found that a noticeable change occurred at a temperature of minus 4 to 6 degrees C. and only at minus 12 to 15 degrees C. does the destruction of the chlorophyll grains become complete (with the exception of those in ever- green plants). With the formation of vacuoles there was produced a dis- tortion of the form of the chloroplasts which were either passing over into the position along the side walls (apostrophe) or were rolled up in lumps. Of these the ones inclosing starch grains were destroyed more quickly than those without starch. In the leaves of Vicia odorata no difference could be perceived in the destruction of the chlorophyll, dependant upon the age of the leaf. We will touch upon this subject again under autumn coloring. A yellow leaved condition in spring is found often in pears growing in nurse- ries, as the after effect of frost disturbances. The grape is very susceptible to icteris. Different factors have been recognized here as the cause. In the cases observed by Mach and Kurmann’® in the Tyrolean vineyards, the analyses of green and icteric vines, growing close together, showed: Water Content of the yellow leaves...... 77.97, Deel cent: Water Content of the green leaves...... 732.17 per cams Based on dry weight, the green leaves possessed a higher percentage of organic substances and of nitrogen, but considerably less ash. The ash of the yellow leaves contained six times as much of the elements insoluble in hydrochloric acid as did that of the green leaves. On the other hand, there was less potassium in the former. Watering with liquid stable manure acted beneficially. A similar case is described by E. Schultz’. The leaves and woody portion of the diseased vines contained only half as much potas- sium as those of the healthy plants, which were found, however, to be poorer in calcium and magnesium. Besides this icterus due to a lack of potassium, a jaundice of the grape, resulting from an excess of calcium, has been determined by numerous observations. It seems to me that the amount of calcium in itself is not the injurious factor, but chiefly the lack of potas- sium, since calcium soils, as a rule, are poor in potassium. We will return to this case in the section on the excess of calcium. Nitrogen starvation is also a frequent cause. This, differing from the phenomena due to a lack of other nutritive substances, does not manifest itself in the death of the plant in an early stage but only retards the growth and reduces all the organs to a minimum. The oft repeated experiments with the cultivation of non-leguminous plants in nutrient mixtures without the addition of nitrogen have shown that under otherwise favorable conditions, with certain races, a new min- 1 Haberlandt, tiber den Hinfluss des Frostes auf die Chlorophyllkérner. Osterr. Bot. Zeit. Cit. Jahresbericht, 1876, p. 718. 2 Biedermann’s Centralbl. 1877, p. 58. 3 Zeitschr. d. landwirtsch. Centralver. fiir das Grossherzogtum Hessen. Cit. Centralbl. f. Agrikulturchem. 1872, p. 99. 311 iature plant can be produced from a seed, developing even to the production of a few blossoms and new seeds. The entire nitrogen content of the whole plant, however, does not in this case equal that of the original seed. It is evident from this fact, firstly, that the plant is not in a condition to make use through its leaves of the nitrogen from the air in quantities worth mentioning; secondly, however, we perceive that nitrogenous substance stored up in the seed enables various individuals to run through their whole developmental cycles, that is to say, to perform all the life-processes, in a minimum compass. This demonstrates further that the nitrogen stored in the seeds is easily mobilizable and capable of transportation, indeed, that the same molecule may probably be utilized more than once for the same pur- pose in the construction of the cell cytoplasm. A consideration of the growth of plants, with a lack of nitrogen, indicates such a condition, for it is found that the lowermost leaves are exhausted to the amount of growth of the tip of the stem and begin to dry, beginning at the edge, or at the tip. In the rapid convertibility and capacity for transportation of the nitro- gen a lack of this nutritive substance occurs very rapidly and manifests itself in jaundice. In our cultures such cases can also occur, if the supply of nitrogen in the soil is still abundant but not in a form available for the special requirements of the definite plant under cultivation. The best ex- ample is found in our sugar beets, to which, besides stable manure, nitrogen is given chiefly in the form of Chile saltpetre. The frequent, very favor- able results of fertilizing various other cultivated plants with ammonium sulfate have now led to the use of this fertilizer in beet culture. But in a practical way these results have not been satisfactory, since the polarization of the beets was far from normal. In a thorough discussion of this point Hollrung', Kruger and Schneide- wind emphasize that the sugar beet is a pronounced nitrate plant, but since the ammonia is not converted so rapidly and directly to nitric acid by the micro-organisms of the soil, a lack of nitrogen compounds may occur and the beets suffer although enough nitrogen is present as ammonia. The phe- nomena of a yellow leaved condition may be due to the constitution of the nitrogen fertilizer which is unsuited to beets, although it may be suit- able for grain and potatoes. An older note has already pointed to the difference in effect secured according to the form of nitrogen provided. Analyses by Lagrauge? showed that in beets fertilized with ammonium sulfate, twice as great an ammonia content was demonstrable as in those fertilized with sodium nitrate. It is a well-known fact that a yellow color can be caused in beet leaves by drought alone, so that we need to cite only a very characteristic example. In 1896 (according to Troude*), the beets in France, especially in the northern part, suffered extensively from a yellow leaved condition. The 1 Hollrung, Inwieweit ist eine Diingung mit schwefelsaurem Ammoniak geeig- net, bei den Zuckerrtiben eine Schadigung hervorzurufen? Vortrag. Blatter fiir Zuckerritibenbau, 1906, p. 70. 2 Biedermann’s Centralbl. 1876. I, p. 258. 3 Cit. Zeitschr. f. Pflanzenkrankh. 1897, p. 55. 312 phenomenon appeared in June after a longer period of intense drought and became widespread especially in sunny positions and on light soils, while regions with a damp, sea climate showed the disease only slightly. The sugar content of the slowly growing beet was from 2 to 3 per cent. less than that of healthy specimens. By a survey of the individual cases just cited, we are led to the con- viction that icterus is one of the most widespread symptoms of disturbed assimilation. No conclusion as to any definite cause has been furnished as yet, however, in the occurrence of jaundice. h. CHANGES DUE TO A LACK OF PHOSPHORUS AND SULFUR. The distribution of phosphorus in the various parts of the plant, de- termined earlier by Ritthausen’s macro-chemical studies, was proved later micro-chemically by Lilienfeld and Monti, as well as by Pollaccit. The last found that, in general, the cell walls are free from phosphorus while the proptoplasm, and especially the nucleus, with the chromatin bodies, con- tain this element in abundance. Among the aleurone bodies the crystalloides and globoids likewise contain phosphorus. The proteins depend especially on the amount of phosphoric acid at hand and a lack of it will make itself felt especially in the blossom buds and in the maturing of the seed. Accord- ing to Nobbe’s cultural experiments’, phosphorus does not seem to play any part,in the formation of the chlorophyll pigment ;—the foliage of oaks which had stood for three years in nutrient solutions, free from phosphoric acid, was still green. In other plants Nobbe ultimately observed that a deep orange red color appears in the leaves and petioles. There is no production of any new dry substance, or only a small amount. Moller* observed in the needles of his pine seedlings a blue-red- (dull violet) color due to a lack of phosphoric acid. In two-year old plants the violet color tended more to olive brown. In the reports on discoloration phenomena, which set in with a lack of various nutritive substances, the results obtained with one plant species cannot be applied to a different species, since discoloration is not every- where the same. In regard to phosphoric acid, I found that when plants of beets, peas, and seradella were grown without phosphoric acid they dried a gray green when they had previously been a faded green, but not yellow, while, with a lack of nitrogen, the same species turned a pure quince yellow. Nobbe found a somewhat better development with a lack of sulfur in the nutrient solution, yet his experimental plants scarcely attained half the normal height and the yellowish green leaf blades exhibited a correspond- ingly scanty development. The starch was scanty and small grained. Cell division was considerably impaired. The forming of fruit either did not take place, or only very scantily. 1 Pollacci, G., Sulla distribuzione del fosforo nei tessuti vegetali. Malpighia. Vol. VIII. Cit. Zeitschr. f. Pflanzenkrankh. 1895, p. 299. 2 Débner-Nobbe, Botanik fiir Forstmianner. 4th Ed., p. 317. 8 Karenzerscheinungen ete. Zeitschr. f. Forst- u. Jagdwesen, 1904, p. 745 313 {a CHANGES DUE TO_A LACK OF OXYGEN. GENERAL PHENOMENA. It is to be assumed as well known that, with the cessation of the supply of oxygen, the protoplasmic currents gradually come to a standstill (oxygen rigor.) Kihne* observed that in an atmosphere of hydrogen the motion in the stamen hairs of Tradescantia virginica stopped after 15 to 20 minutes. Wortmann?’ found that the parts of plants in air free from oxygen respired at first exactly as much carbon-dioxid as those with an unimpaired supply. Later a difference made itself felt in favor of the latter plants. Like the gradual cessation of the cytoplasmic currents, this gradual retrogression in the amount of carbon-dioxid with the exclusion of oxygen (intramolecular respiration) indicates that the oxygen stored in the plant body is consumed at first. Death from suffocation, therefore, takes place slowly, especially since the green plant with sufficient illumination still decomposes carbon- dioxid and water and thus forms oxygen for some time. Bohm* detected a small amount of oxygen in the volume of gas evolved when he enclosed the green leaves of land plants in an atmosphere of hydrogen with sufficient illumination. Aside from the cases which have been observed already in the divisions on “Loamy soils” and “Too deep planting of trees,” we will consider a few occurrences of bad aération as a result of closing the lumina of the ducts forming the main water system. Such stoppage is especially serious for the sap wood*. With Bohm® we may picture to ourselves the process of aeéra- tion as follows: There is not only a difference in pressure between the outer air and the diluted air inside the ducts, but also a difference in con- stituents. The enclosed air will give up its oxygen in. the respiratory pro- cesses more rapidly and take up the carbon-dioxid produced. This is either soaked up, by the filling of the ducts with water, and carried off in the rising sap current, or, since it penetrates the moist walls rather easily, is given out in a radial direction by diffusion. The new and necessary oxygen which ‘n lesser amounts may also enter through the roots with the air rich in oxygen, dissolved in the water, will, nevertheless, under normal conditions get into the plant mainly through transverse conduction. It diffuses more easily through moist walls than does the nitrogen of the air, because water absorbs it more abundantly than it does nitrogen. Since now the oxygen within the plant body is utilized most but is also most easily capable of moving from part to part, there results a prevailing diffusion stream of oxygen from with- out inwards in each horizontal plane of a trunk. 1 Untersuchungen iiber das Protoplasma. 1864, p. 89 and p. 106. 2 Wortmann, Uber die Beziehungen der intramolekularen zur normalen At- mung. Inauguraldissertation, Wurzburg, 1879. 3 Bodhm, tiber die Respiration von Landpflanzen. Sitzungsber. d. Kais. Akad. d. Wissensch. in Wien, Vol. 67 (1878). 4 Elfving, Uber die Wasserleitung im Hoize. Bot. Z. 1882, No. 42. 5 Bobhm, J., Uber die Zusammensetzung der in den Zellen und Gefafsen des Holzes enthaltenen Luft. Landwirtsch. Versuchsstationen Vol. XXI, p. 373. 314 Wiesner! made further observations on gas exchange. He shows that the periderm, the cork covering, is completely impermeable to air even with great differences in pressure. The exchange takes place only through the lenticels which are permeable even in winter. In wood free from ducts the equalization takes place through the cell walls, especially through the deli- cate pitted walls in which, besides the diffusion, absorption through the col- loidal walls comes into effect. In woody bodies, rich in ducts, transpiration and the penetration of gases through the ducts, functioning as capillary tubes, should also be taken into consideration. The equalization of the pressure takes place more quickly axially than transversely. The more turgid a parenchyma or wood cell is, the more slowly does the equalization of the pressure occur. This relation is reversed in the periderm cell. If it incurs the loss of its aqueous contents and is filled with air, whereby its wall becomes dry, the cell loses its permeability for gases. In parenchyma which conducts air, a part of the air flows through the intercellular passages during the equalization of the pressure, another part passes through the closed membranes and, indeed, most easily through the places which have remained unthickened. A statement by Mangin® throws light on the processes taking place in trees, with poor soil aeration. He found that the ducts in Ailanthus were filled with tyloses, and, in explaining the process, states that, correlative with a lack of air in the soil, a deficiency in the supply of air in the ducts takes place. Consequently the air in the ducts becomes diluted beyond the opti- mum and the tyloses of the adjacent cells push into the tube of the duct and, on their part, also hinder the conducting of water. In regard to the influence of a lack of oxygen on seeds, Bert’s* investi- gations should be considered first of all, according to which germination progresses more slowly in a lesser air pressure. Many years ago Corti* observed that a dilution of the air had an arresting influence on the cyto- plasmic currents. Since, however, with a normal air pressure and only de- creased oxygen content, germination takes place more slowly and, con- versely, with a lowered air pressure but increased supply of oxygen the seeds germinate more rapidly, it is evident that even the partial pressure of the oxygen alone is a decisive factor. In the phenomena due to lack of oxygen, opportunity is again offered of pointing to the fact that sudden changes are more disturbing than gradual changes. Stich® found that in an atmosphere poor in oxygen the normal respiratory quotient is recovered by decreasing the absolute amounts of oxy- 1 Wiesner, Versuch iiber den Ausgleich des Gasdruckes in den Geweben der Pflanzen. Sitz. d. Kais. Akad. d. Wissensch. zu Wien am 17 April, cit. in Oesterr. Bot. Zeit. 1879, p. 202. 2 Mangin, Influence de la raréfaction produite dans la tige sur la formation des thylles gommeuses. Compt. rend, 1901, II, p. 305. 3 Bert, Recherches expérimentales sur l’influence que les changements dans la pression barométrique exercent sur les phénoménes de la vie. Compt. rend LXXVI et LXXVII. 4 Meyen, Pflanzenphysiologie, 1838, II, p. 224. 5 Stich, C., Die Atmung der Pflanzen bei verminderter Sauerstoffspannung und bei Verletzungen. Flora, 1891, p. 1. 15 gen and carbon-dioxid. With a gradual removal of oxygen, intramolecular respiration is aroused only with a considerably lower percentage of oxygen, than it is when the oxygen is suddenly decreased. The discovery that phenomena of suffocation occur also in seeds if their tissue is entirely filled with water is of great value to the practical worker. Usually when seeds are soaked they get the water necessary for germination ‘vithout having all the air pressed out of the intercellular spaces. If, how- ever, the seeds are kept too long in water, decomposition sets in, in which often a distinct ordor of butyric acid, a result of bacterial decay, becomes very evident. In the same way experiments, like those of Just', for example, ' show that when air has been removed by a pump from the tissues ordinarily containing air and the space filled with water, the percentage of germi- ration is very greatly reduced. When seeds have been put in layers on top of each other while damp, it is not the excess of water, which so quickly destroys the germinating power, but the excessive heating and formation of carbon-dioxid. Wiesner? found also that the carbon-dioxid is developed later than the heat. Hence its development is not the only source of heat; this is to be sought also in the absorption of water. The seed, coming in contact with water, con- denses it as it enters the tissues and thereby frees heat. That an excess of oxygen is just as injurious as a lack of it, is natural. 3ert found that the oxidizing processes in plants are arrested by too high a tension of the oxygen. A mimosa died at 6 atmospheres in common air, hav- ing lost its irritability because of a lack of oxygen. If the air was made richer in oxygen, a pressure of 2 atmospheres was sufficient to cause death. THE BRUSONE DISEASE OF RICE. The unusually dreaded brusone disease which manifests itself by the appearance of rusty spots in the leaves together with a blackening and drooping of the blades, has often been the subject of earnest study, ever since Garovaglio in 1874 began investigating it. The majority of investi- gators considered the phenomenon parasitic. Some thought it necessary to assume bacteria to be its cause, and some held various fungi responsible,— among others, Piricularia Oryzae Br. et Cav. Recently, however, Brizi® has made comparative cultural experiments from which it becomes evident that an exclusion of air from the roots in high temperatures in water cultures induces disease of the plants with the phenomena of the Brusone disease. With these experimental results agree very well the discoveries which have beer made in Italy and Japan. It has been especially observed that the Brusone disease usually appears if com- pact, only slightly pervious soils are heated greatly and a rapid change of temperature sets in. There then follows an affection of the root which 1 Bot. Z. 1880, p. 143. 2 Landwirtsch. Versuchsstationen, 1872, No. 2, p. 133. 3 Brizi, U., Ricerche sulla malatti del riso detta Brusone. Ann. Instituto agrar. Ponti. 1905. Milano. Cit. Zeitschr, f. Pflanzenkrankh. 1906. 316 brings disease of blades in its train and only later do parasitic organisms infest the diseased parts. We consider Brizi’s experiments as decisive and think that suffocation of the roots during high temperature, which greatly increases the leaf activ- ity, is the first impulse to the disease. The soil should be aérated at once. THe DISEASES OF GLADIOLI. A phenomenon of disease, not rare in cultivating gladioli in heavy soils, or on pieces of ground with a lighter soil, but a higher ground water level in wet years, may be traced to a lack of oxygen. The disease manifests itself in the often sudden aeath of the plant at a time. when the inflore- scence is already developed. At first the lower leaves seem marbled with yellow (noticeable at first only when the light falls through them). The chlorophyll bodies decompose and leave yellow drops which look like oil. While this process advances apparently in stripes between the veins in the aérial parts of the leaves, brown, depressed places are found on the leaf bases still below the soil which initiate a complete decomposition of the leaf parenchyma. No real weakening takes piace, but the decomposition repre- sents a process of humification. Bacteria, and often also fungi, small worms, mites, etc., are always found in these tissues which smell sour like humic acid. The aerial parts of the leaves dry quickly and become covered with black pits of Cladosporium and Alternaria. Despite the wealth of parasitic organisms present, the disease should not be characterized as parasitic, since the first stages, viz., the brown coloring of the ducts and of the parenchyma, lying close to them, are produced within the healthy tissue without the co-operation of such organisms. Later a number of the duct tubes are filled with a cloudy, brown mass which be- comes firm like gum. The latter phenomenon has been observed also in other plants, the roots of which were injured by continued moisture in the soil and the lack of oxygen thus produced artificially. Gladioli like a great deal of moisture in the soil but it should not be long continued. In dry years the mistake is often made of watering bulbs and tuberous plants every day. This is wrong, the excessive drying of the soil must be prevented by mulching with litter. k. CHANGES DUE To A LACK oF CARBON-DIOXID. Despite the small content of possibly 0.036 to 0.040 volume per cent. of carbon-dioxid, which the air’ possesses, while consisting of nearly 79 parts of nitrogen and 21 parts of oxygen, it suffices everywhere for a high rate of growth; if this important nutrient substance is entirely lacking, the other factors of growth are without value, even in a most favorable com- bination, as may be observed experimentally by placing vessels of caustic 1 According to Jolly’s investigations (cit. in Forsch. a. d. Gebiete der Agrikul- turphysik. 1879, p. 325) the oxygen content of the air varies not inconsiderably (between 20.538 and 20.86 per cent.). The largest oxygen content is found with a prevailing polar current and the least with a prevailing equatorial current. 317 potash under closed bell-jars. Corenwinder' found that buds and young leaves do not develop further in air free from carbon-dioxid. In Bous- signault’s* experiments two maize kernels developed into plants of which the dry weight itself and the carbon and oxygen contents were less than in the seed, while the nitrogen content was just as large. Hydrogen and ash had undergone a slight increase. Bohm* found in leaves of the scarlet runner bean, cut off from the plant during growth, from which the starch had been removed by darkness, that these leaves not only formed roots from the petioles in full daylight and in an atmosphere containing carbon- dioxid, but also increased in breadth even if they were watered only with distilled water. On the other hand the seedlings of the scarlet runner bean grown in distilled water and exposed to the action of full daylight under bell-jars with caustic potash showed only an increase in length up to 10 cm. while the stems shrivelled below the primordial leaves which as a rule were free from starch. Seedlings of the scarlet-runner bean which had been grown in garden soil rich in humus but were robbed of all but a small amount of their starch by weak illumination, did not form any new starch but went to pieces when later strongly illuminated in an atmosphere robbed of its carbon-dioxid. Therefore, the carbon-dioxid in the soil and the other favorable conditions for growing were of no value. (Godlewski* found that the starch also disappeared in plants exposed to full daylight if the carboa- dioxid of the air was kept from them. A further irsight into the method of growth of plants from which the carbon-dioxid of the air had been removed is given by my own experiments’. Young cabbage plants were left in a 0.5 per cent. nutrient solution, part under bell-jars with caustic potash, part under others without caustic potash and the remainder left free between the bell-jars. After ten days the har- vest yielded :— Bell-jars Bell-jars Uncovered plants with Potash without Potash ad —_—_ vas == ‘om ae Plant NiOts swore 2: I. iif Niele IV. Whe VI. AVATIR, eV GlUiTe rer Iexe: Fresh weight of root and SCM eerste eiee shane’ seeks O45 0:36 (0:44 (0:470" Ona ~ 02305) 0:297%" Orsis 0r232 Fresh weight of leaves... 1.598 1.494 1.564 1.682 0.765 WADE alexis alae elses 5y(0) Upper leaf surface in SOMERS (O00 es Sia eed CS 50.6 47.5 50.1 47.3 25.4 26.6 50.4 54.1 Beal Total dry weight...... 0.2755 0.2510 02.685 0.2760 0.0760 0.0985 0.1705 0.1740 0.1765 Percentage of the fresh weight in dry weight 13.4 ses oes 12.8 8.4 7.9 8.1 8.6 8.4 Total evaporation in STAINS eects cave tar onse 69.3 74.4 82.5 75.0 27.4 34.4 43.1 40.4 43.3 Evaporation per gram CGV Welt Ut niceniiee me oleD) 2904s oOleen ziilet s60.6 349.2 252.8 232:2 245.3 The table shows that the production in fresh and dry weight was the smallest under the bell-jars with potash. The absolute amount of evapora- 1 Recherches chimiques sur la végétation. Fonctions des feuilles. Compt. rend. t. LXX XII, 1876, No. 20, p. 1159. 2 Boussingault, Végétation du Mays. commencé dans une atmosphére excempte d’acide carbonique. Compt. rend. Vol. LXXXII, No. 15, p. 788. 8 Bohm, in Sitzungsber. d. Wierner Akad. 1876, cit. Bot. Zeit. 1876. p. 808. 4 Bibliographische Berichte tiber die Publikationen der Akademie der Wissen- schaften in Kraukau. Part I, cit. Bot. Zeit. 1876, p. 828. 5 Sorauer. Studien tiber Verdunstung. Forschungen auf dem Gebiete der Agrikulturphysik, Vol. III, Parts 4 and 5, 218 tion is greater or less according to the amount of newly produced dry sub- stance; it is smallest in the plants under the bell-jars with potash. Naturally the effect of the bell-jars, i.e., the humidity prevailing under them, is to be taken into consideration. This factor manifests itself, when compared with the uncovered specimens, by the lower percentage of dry weight in the plants, i. e., by a loose structure and longer petioles. If the specimens from the bell-jars containing potash are compared only with those of the other bell-jars, the result is more certain. The lack of carbon-dioxid manifests itself most by the lessened total production, especially in the leaf apparatus; the upper surface is only about half as large. The most striking effect is the amount of evaporation, which is cal- culated per gram of dry substance present. This is greatest in the plants deprived of the carbon-dioxid supply. The same condition is found in the calculation of the evaporation per square centimeter surface in the plants grown under both conditions. This fact should be associated with the re- sults of other experiments, according to which it is evident that the amount of evaporation increases also in plants which lack other nutritive substances. Tf, for example, plants from a normal favorable nutrient solution are placed in one of too low concentration, or in distilled water, evaporation is in- creased ; it increases also in seedlings after the removal of the organs con- taining reserve food, the cotyledons. It may be assumed that the plant must force itself to a greater transportation of water through its roots, 1. e., to a greater one-sided kind of labor, in order to meet lesser amounts of re- serve substances contained in the solution due to their increased absorption by the roots from the surrounding soil. For practical work, the above investigations suggest an attempt to in- crease production by increasing the supply of carbon-dioxid. Experiments actually show that a much more rapid formation of starch is obtained by increasing the carbon-dioxid. In many plants an increase up to 6 to 8 per cent. was possible. Of course,‘a different absolute quantity of carbon-dioxid is necessary for each plant and in the same plant for every other combination of the vegetative factors in order to obtain an optimum production. The strengthening of the vegetative processes by the addition of carbon-dioxid manifests itself in the more compact growth and thicker leaves’. While previous experiments have taken up the results of a lack of car- bon-dioxid for the whole plant, V6chting? tested the behavior of various branches, which were left on the normally growing plant, but transferred to an atmosphere free from carbon-dioxid. It was found thereby that each branch and leaf must be maintained by its own work and that their life activity gradually dies away if this work is prevented by a lack of carbon dioxid. The plant can, indeed, develop further the branches in the atmos- phere free from carbon-dioxid, but the leaves on these branches are a faded 1 Feodoresco, E., Hinfluss der Kohlenséure auf Form und Struktur der Pflanzen. Cit. Centralbl. f. Agrikulturchemie, 1900, p. 137. 2 Véchting, H., tiber die Abha&ngigkeit des Laubblattes von senier Assimi- lationstatigkeit. Bot. Zeit. 1891, Nos. 8 and 9. 319 green and form no starch. They also do not recover, if the branch, is brought back to air containing carbon-dioxid, but go to pieces after a short time. It thus becomes evident that each leaf has its independent existence and that any disturbance of it cannot be adjusted by the organism as a whole. The organ which has become functionless is thrown off from the body. Ba Ep xGHSsS OF WADERS AND NUTRITIVE SUBSTANCES. a. Excess oF WATER. MOISTURE. The phenomena of yellowing and decomposition connected with stag- nate water have been considered when discussing the disadvantages of heavy soils. We are thus concerned here only with proving by example, how an excess of water, like a lack of it, retards production. Thus Stahl- Schroeder’s! experiments with oats in sterile sea-sand to which the nutrient solution had been added, gave the following results. With the addition of water there were produced: % of the No. Weight of Weight of | Medium Phos- | Nitro- entire water] of 1000 kernels straw and| length of Ash phoric gen capacity ker- chaff the plants acid of the sand | nels g gs cm. % % % 35 84 | 15.5(caleulated) 6.2 49 2 ve 3.7b2 50 1723 21.6 (exe) 102 2.933 1.444 2.915 70 2074 18.5 101.8 140 2.712 1.090 2.501 90 1827 16.3 115.0 157 3.007 Or 2.407 95 469 | 11.1(calculated) 90.8 162 5.892 1.847 3.444 Thus only the vessels containing a medium amount of water yielded a good harvest in grains. With a larger water content, the harvest of grains fell, while the yield in straw increased. With a lack of water in the sand (35 per cent.) and with an excess (95 per cent.) none of the grains ripened. The poorer the growth of the plants, the greater their percentage of ash con- tent, and wealth of phosphoric acid and nitrogen. CLOGGING OF DRAIN TILE. Wherever flat lying drains extend through the root systems of perennial plants, an unusually luxuriant root growth may stop up the drains. The long whip-like, very slender and comparatively thin roots lying side by side, like cords, in this way form mats ten or more meters long and as thick as the width of the drain allows. The most dangerous tree seems to be the wil- low for most of the drain mats seem to be formed by it, yet all plants may form similar root-growths and Magnus? once found, for example, the rhizome of the horse tail (Equisetum palustre, L.) growing very luxuriantly in such a mat. Cohn* found a drain mat which came from a pipe laid 125 ef. Biedermann’s Centralbl. f. Agrikulturchem. 1905, Part 2. Sitzungsber. d. Bot. Vereins vom 26 Mai, 1876, Vol. XVIII, p. 72. Verh. d. schles, Gesellsch. f. vaterl. Kultur, 25 Oktober, 1883. co nm 320 cm. deep and was formed entirely from the ramifications of the root of a single Equisetum from which a piece 12 meters long could be separated. Muller-Thurgau experimented with roots from one plant, putting some in a nutrient solution, others in distilled water; each experiment showed a stronger growth in the solution. These experiments showed that root growth increases locally when the roots reach places containing food sub- stances. If the drain mats return after removal, it is advisable to take out care- fully both trees and roots by uprooting and not by chopping down. If the trees must remain it is better (especially with double lines of drainage) to lower the surface laid pipes (as a rule between 80 to 90 cm.) to the level of the pipe system lying deeper (1.5 m.). SPROUTED GRAIN. In the phenomena to be cited here which are connected with an excess of water, injury is caused either by the fact that water from outside acts mechanically on the tissues at an unsuitable time, or the water taken up by the roots cannot find utilization and be carried off in corresponding amounts. To the first group belongs grain sprouted on the field during the harvest because of rain. The disadvantage is the greater in this instance, since the sprouted kernels can neither be used for nutritive purposes nor are they suitable for seed. Of course the germinative capacity for subsequent use as seed decreases according to the amount the kernels have sprouted. Ehrhart! found that the weakness and thus the mortality of the seedlings increased as their development had already advanced because of the pre- mature sprouting. We owe to Marcker and Kobus* thorough investigations of the changes in the seed due to sprouting. The former investigated barley, half of which was harvested uninjured, but the other half was left standing for almost 14 days, wet through by rain. The differences were shown by a determination of the elements soluble in water, for they amounted to the following in Sprouted and in well-harvested barley Solublesstanch (cy. oa eae Lay per cent: L7ocper cent: IDOE AG 4\ 7 hc. a Rie 0.00 per cent. I.10-per cent. IDExiROSE Ry fee eer A.Q2) per icent. O.0O5pEer Cent WMaltose? uot 28. se weet F522) Per ecent. Ale. peu cent Other soluble substances... 5.23 per cent. 5-04 per cent. 18.64 per cent. TT.02*perscent: We thus see that the vigorous diastase action has resulted in a very abundant sugar formation from the starch and dextrin. The starch con- tent had fallen from 64.10 per cent. to 57.98 per cent., because of the sprouting. If the kernels are used for making starch, the great amount of SSS ll 1 Deutsche landwirtsch. Presse, 1881, No. 76. 2 Aus Braunschweiger landw. Z., 1882, No. 22, cit. in Biedermann’s Centralbl. f. Agrikulturchemie, 1883, p. 326. 321 diastase would now presumably convert more starch into dextrin and sugar, when softened, and result in appreciable losses in manufacture. The great- est changes due to sprouting, however, are found in the nitrogen-containing elements of the grain. While especially the ammonia content had remained unchanged (nitric acid was not found in quantities worth mentioning in either of the two kinds of grain) the scluble proteins had decreased to a great extent, the insoluble to a lesser one. This decrease is explained by the relatively great increase of the amides. Thus, in sprouting, first the soluble proteins had been consumed in the formation of the amides and later even a part of the insoluble ones. Kobus arrived at the same results in his investigations of sprouted wheat, whose gluten content had decreased from 20 to 25 per cent. This fact explains the well-known loss in baking quality of a flour made from sprouted grain. The germinating capacity in the experiments carried out by Marcker had fallen from 98 per cent. to 45 per cent. It thus becomes evident how worth while are the great efforts which must be exerted in any case to make possible harvesting the grain while dry. Similar losses may befall other field crops as well, as, for example, lupines, rape, beet roots. The cases in which the seed germinates inside the fruit without being noticeable externally are interesting but not of importance agriculturally. I found such cases in pears, apples, melons, and pumpkins. Other observers found the same phenomena in oranges, as well as pumpkins, and indeed in other fruits also which had remained very long on the trees, and in that which had only colored late. Further statements on this subject may be found in the section on germination interrupted by drought. THE RUPTURING OF FLESHY PARTS OF PLANTS. Fleshy roots, stems and fruits frequently crack open in long periods of dampness. Among vegetables, kohlrabi, carrots and parsley suffer especially. Hallier’ proved that the rupturing is due to excessive water supply, for by hanging parsley roots in water he found after three days that all the part which was in the water had cracked open. Boussingault? observed the rupturing of cherries, mirabelle plums, pears, grapes, and blueberries after the fruits had hung in water. I obtained the same results by imbedding them in wet sand. Of herbaceous stems, those of rape crack open very freely shortly before the time of blossoming. The figure here given shows the change in a bean, which I had planted too deep in wet sand. In July, 1882, in Proskau, I found ruptured potato stems and Beta vulgaris roots. At that time a very rainy July had followed a dry spring after a small amount of winter moisture. The phenomenon was apparent at first on light places in the soil and in the best developed plants. I found similar cases in roses and in plum seedlings, which had been taken from the sand and 1 Hallier, E., Phytopathologie, p. 87. 2 Compare Bot. Jahresbericht, 1873, p. 258, ee 322 placed deeper in a nutrient solution than they had been in the sand. The base of the stem split in those specimens previously exposed to the air. In the souring of crops in fields planted with horse beans, peas, + -vetches,) tebe; the base of the stem is rup- tured at times above the places where the (rotted) roots arise, and it is found that a spongy, loose tissue protrudes from the torn place, as in) the, bean here aiis- trated. All these phenomena have one characteristic in common —that they are initiated only when, after a considerable period of normal develop- ment, or still more after a previous dry period, an un- usual supply of water is given suddenly. If the plants are in contact with water from the beginning of their de- velopment, they adjust them- selves to their surroundings. The same adjustment can be observed especially in those varieties which develop in water as well as on dry land. Levakoffski’s' experiments on Epilobium hirsutum, Lycopus europaeus and Lythrum serve as examples. The compari- son of water and land speci- mens shows that in the water plants, two rows of colorless 1 Levakoffski. De linfluence de l'eau sur la croissance de la tige ete, Cit. Bot. Zeit. 1875, p. 696. Bean plant split at the base as the result of excess of water, The torn place has scarred over. 323 cells, free from chlorophyll, 3 to 4 times as long as they are broad, exist between the cambium and the bark parenchyma which are not present in the land specimens. This difference becomes greater, when the older parts of the plant are compared with one another. Below the surface of the water these cell rows become a thick, lacunar tissue Epidermis and bark soon go to pieces here. The cells which form this special tissue are de- veloped from the cambium. The sudden excess of water, which causes the rupturing of part of the plant, destroys the equilibrium in the epidermis, or the cork layer present instead of the epidermis, and in the fleshy parenchyma body. Especially after previous periods of drought, the elements of the upper epidermis be- come thicker walled and less elastic and are not able to accommodate them- selves rapidly enough to the swelling inner tissue. If the rupturing takes place in succulent organs without any previous dry period, due to a long continued supply of water in damp surroundings, the torn places, as a rule, differ from those due to drought, in that, in the latter, the wounded surface turns to cork or is cut off by a new cork layer. In the former, on the other hand, the parenchyma cells, exposed by the rupture, remain thin walled, at times elongated into pouches and decaying easily. Boussingault found that the fruits lost sugar to this excessive water. This loss of sugar together with the increased absorption of water may explain the watery taste of the fruit after rainy weather. Some blossoms, left under water, also lost sugar. On the other hand, in sugar beets, rape, in the seedling roots of wheat, barley and maize no sugar was lost although the tissue was rich in sugar. There is a method of storing winter apples which is well worth recom- mending, viz., placing the fruit in layers in sand. If the sand is kept too moist, a large percentage of the fruit may lose in selling value because the skin ruptures. Muller-Thurgau' made similar observations in related experiments. After apples had lain eight months in boxes of earth he found the fruit was wet, some of it ruptured, some mealy, and its acid and sugar content much lower. The percentage of decaying apples was much less, however, than in fruit lying free in the cellar. The rupturing of fruits and vegetables, due to storage methods, can be overcome by supplying a dry, well ventilated place. In fruit on the tree, especially the egg plum which is very delicate, it is advisable in longer periods of rain to shake the water from the tops of the trees. Finally, attention must still be called to the fact that the tendency to rupture can also become hereditary. An observation of this was made with cucumbers’. In forcing these, the owner always chose for his seed the finest specimens of a variety which ruptured easily, and observed that this bad condition manifested itself more abundantly and earlier from year to 1 Fiinfter Jahresb. d. deutsch-schweizerischen Versuchsstation zu. Wadensweil. Zurich, 1896. 2 Zeitschr. f. Pflanzenkrankh. 1899, p. 183. 324 year. He then planted half of his greenhouse with the forcing variety pre- viously used and the other half with an outdoor variety. The latter gave healthy fruit up to autumn, while the half planted with the first variety produced ruptured fruit from the beginning of May on. Such observations give hints well worth noticing when choosing seed of vegetables which tend to rupture. THE Woo.L_Ly STREAKS IN APPLE CORES. In describing apple varieties the expression “The carpels of the cores rupture,” is found stated here and there, as a characteristic of the variety. According to the illustration here given, a condition of membranous carpels is said to be indicated in which the inner walls of the core divisions are not uniformly smooth and solid, but show a surface crossed by streaks which Fig. 48. Cut apple, the core of which shows woolly streaks (w). look white and woolly, and extend slantingly from the centre to the outside. The phenomenon occurs frequently and is considered to be normal,—which deduction I do not care to hold to. Aside from the fact that under certain circumstances all the fruit in the same variety does not show such woolly streaks and that, in different years, it is developed to a different degree, even appearing in isolated cases in varieties which, as a rule, have a smooth core, the conditions found microscopically also prove splendidly the ab- normal nature of these streaks. If a carpel with such streaks is cut through, as shown in Fig. 43 at w, the appearance is found as given in Fig. 44. In this the side designated by K is the inner wall of the core, while F indicates the outer side bordering on the flesh of the fruit. In varieties of apples with smooth carpels, the inner lining of the core is formed only of such cell elements, as are shown 325 at p. These are very much elongated, extraordinarily thick-walled cells, traversed by many, frequently branched canals; they turn yellow with chloriodid of zinc. Single layers of such cells may cross one another. Ac- cordingly, besides such cells seen in full length at p, the same horizontal section also exhibits parts of elements in cross-section g. It is evident that, because of the close arrangement of the cells on the one hand and because of their very strong walls on the other hand, a very great firmness is ob- tained in the core tissue, increased by the transverse course of the cells. It is evident further, that in fruits with a larger calyx depression, through which fungi may grow easily into the core, the spread of fungi, which pro- duce decay, is limited by the parchment-like, solid carpels. [ye pe Ww lo allf 4 i 4 5 ib mes - y J Sy yy ee) eee OE ( vie Soop Fig. 44. Rupturing of the papery carpel of the apple, due to the excrescence tissue of a woolly streak. (Orig.) This protection from internal decay is destroyed by the woolly streaks (Fig. 43 W) for they consist of very loose tissue, which breaks through the solid walls. We see in Fig. 44 that these woolly streaks are formed of thick bunches of cell rows elongated like threads, which differ strikingly from the sur- rounding ones because of their thinner walls, and very gradually pass over into the tissue of the fruit (Ff), while others are quite sharply and suddenly cut off from the thick-walled cells (~) below the places in the core which have remained membranous. Only at the base of this bunch of threads do short, schlerenchymatous cells (sk), isolated or lying beside one another in mats, recall the elements (~) to be found in the normal wall. Although these 326 thin-walled cell rows approximate more nearly tissue of the fruit in form and by the blue coloration from chloriodid of zinc, they still do not corres- pond to it entirely. The difference consists chiefly in a wart-like thickening of the cell wall w which is most strongly developed in the outer cells of the thread bunch, but in the inner cells is often only weakly indicated and generally is not present at all in the schlerenchymatous elements. These cell wall thickenings which push outward and look like buttons, show, with the action of chloriodid of zinc either a pale blue color or remain uncolored, or even appear yellow. The latter case is found most distinctly in the very thick-walled cells (sk) in which the whole membrane is also colored yellow. Fig. 44, at the left, is a more strongly magnified section from a cell row of the bunch filament. It is seen here that the wart-like protuberances of the wall which I would also like to consider phenomena of the swelling of various points in a fine middle lamella, often have mushroom forms (kn)'. Thus it should be assumed, that at the time of the chief swelling of the fruit, the tension of the tissues in the carpel has become so great, because of a sudden, great supply of water, that the connection in the membranous tissues is broken in stripes and loosened and the elements now freed from pressure, and not thick-walled, extend like pouches into the hollow of the core. Varieties inclined to have woolly streaks are especially easily exposed in damp years to the formation of moulds, i.e. phenomena of decay in the core. It is, therefore, advisable to use these fruits quickly. THE RING DISEASE OF HYACINTH BULBS. This disease is very serious for growers of hyacinth bulbs. It manifests — itself by the browning and loosening up of a scale in the midst of healthy bulb layers. The decomposition of the tissue progresses from the neck of the bulb downwards into the bulb centre. If it reaches the latter, the bulb is as good as lost. The disease is often transmitted to the bulblets. All the diseased parts become covered with Penicillium, which here has actually taken on a parasitic character. The reason for the extremely rapid spread of the fungus is to be found in the change of the substratum which proves unusually favorable for it. Analyses show especially that the fresh, healthy substance of the ring-diseased bulb possesses more sugar than that of healthy specimens. The former resemble younger scales in contrast to the older ones. Since now a reduction of the sugar takes place with the increased ripeness of the bulbs, we shall have to conclude from the greater amount of sugar that diseased bulbs are less ripe. In fact it may now be proved that by their cultural methods our bulb- growers often run the risk of harvesting unripe bulbs. In taking up the bulbs, the grower sometimes does not wait until the leaves have completely dried up in summer. This holds good primarily where the hyacinths serve 1 The same or similar phenomena have been observed very recently by various scientists. I found them also in the hair-like cells, clothing the interior of beets which had become hollow; in the leaf parenchyma cells of fallen oat plants, etc. 327 as decorative plants in gardens and public places. There a bed of old flowers and slowly yellowing leaves is very unsightly. Consequently the bulbs are lifted and let ripen in another place. The resulting great injury to the root prematurely checks the vegetative growth of the bulbs. The leaves dry before they have lived out their life and their bases, i.e. the scales of the bulbs, remain immature and rich in sugar, thereby forming the desired centre for convenient infection by the fungus. In the large field-grown commercial bulbs, the supply of fertilizer enters into the question, since it is desirable to produce very strong bulbs in the shortest possible time. The fertilizer so lengthens the time of growth that many varieties have not finished growth at the fixed time of harvest. The leaves, still green, then possess in every case unique scales and during the storage of the harvested bulbs on the “bulb floors,” up to the time of the autumn sales, Penicillium has ample time to attack the scales, which remain rich in sugar, and to destroy them. It is a matter of course that varieties ripening especially late will exhibit this bad condition and the growers, therefore, speak of “ring diseased races.” The testing of the bulbs is accomplished by cutting superficially through the tip of the neck during the dormant period. If the cross-section shows a brown ring between the white scales of the buibs, these bulbs should not be sold. Stock suffering from the ring disease can be cured by putting the bulbs in sandy soils, not freshly manured, with a deep lying ground water level, where, with scarcity of nutriment and moisture, they can ripen early. The fact still remains to be mentioned that a phenomenon has been con- fused with the real ring disease, which is very similar to it judging from its habit of growth’. The cause is known to be a nematode (Tylenchus Hyacinthi Pr.) which can wander into the scales from the leaves. In this disease, however, a gall-like distension of the cells takes place, also the formation of cork walls like little islands and other differences, as has been described more in detail in the second edition of our manual. SPRINGING OF THE BARK. In illustrating the ruptured bean plant (Fig. 42), we noticed that a soft tissue mass had protruded through the gaping split in the cracked stem. This is the new formation of bark tissue, which may be considered a re- action of the organ to the wound stimulus and the decreased tension. Other cases, however, occur in which matters are reversed, viz., that the increase of bark tissue is the primary process and the splitting, the secondary one. Such an increase in growth can arise from different causes. Hartig? con- siders one of these to be the increase in size caused by a sudden isolation of forest trees. He describes cases of hornbeams in a beech grove, where, 1 Journal de la Soc. nat. et centrale d’Horticulture de France. April, 1881. Sorauer, Zur Klarung der Frage tiber die Ringelkrankheit der Hyacinthen. Wiener illustrierte Gartenzeitung, 1882. April number, p. 177. 2 Hartig, R., Das Zerspringen der Hainbuchenrinde nach pl6étzlicher Zuwachs- steigerung. Untersuch. forstbot. Inst. Vol. III, p. 141. 3228 after isolation,—“the breast high growth, measuring 1.2 sq. cm. in cross- section, in a few years increased in cross-section growth to 13.7 cm. ann- ually’.””. The cork was split thereby in numerous places and resulted in a rupturing, indeed, in places it lifted the bark body from the wood-cylinder. Hartig found similar conditions in oaks and explained this by a greater soil activity, resulting from the isolation and increased action of light?. Phenomena of this kind may be found also in other trees, especially in parks and gardens. SHEDDING OF THE Bark. Hartig describes a case in which the splitting of the bark is due to an increase in the normal growth. I observed a splitting and shedding of the bark from an ab- normal cell - elongation in the bark parenchyma. In 1904, I found in an avenue of elms a num- ber of trees standing side by side at the bases of which a great many pieces were perhaps as long as one’s hand. Upon closer investiga- tion, loosely hanging strips of bark 25. to 50 cm. long were found on the lower end of the trunk, which could easily be removed. The trunk, thus exposed, was coy- ered with greenish tis- sue in spots which proved to be new for- Fig. 45. Inner surface of a fallen piece of elm mations of bark. The bark, with cushion-like, protruding tissue islands. : i (Orig.) loosened pieces of bark (Fig. 45), exhibited on the inner side flat, light brown cushions irregularly distributed and differing in size and thickness. Having a spongy consistency, they easily gave way to the pressure of a finger-nail. Here and there, between them could be seen crater-like, harder, small protuberences. The upper surface of the cushion was smooth; it was rough and sometimes woolly in places because of prominent, hair-like processes. The part of the bark remaining on the 1 Lehrbuch der Pflanzenkrankh, 1900, p. 261. 3 Unters. Vol. I, 1880, p. 45. 349 tree appeared a yellowish green and juicy. It consisted of bark parenchyma, which had originated from a healthy cambium. The subjoined Fig. 46 Se. pictures the bark aboutto %____ ITH PRIERS -~-.- YO? Os) be shed. At hf is shown P RerHaLea INN Sean the old wood; at nh the “~~ Sen last produced new wood; = ne g smmdicates ducts; c the WY le he ete NWO 72 cambiuait Next tins, Ines “Ss<2-—,- 22-1 WU the normal, young bark “Tho, RY which — gradually passes sp--- SNe asd over towards the outside WU P| into the broken older bark. \ Vea \ < In reality the extent of \\y 1) IVES loosened older bark is Pea \\ Cae : b<-.., much greater in proportion > \\\ to the normal young bark Cee K hee Space Gasp) Bee ona than is shown in the draw- 1--- Th) me, because of lack * of 4 N PL] Se ky @ DN STH . : “| w= l ® AS nD | space. The normal inner “GE lees yh: Op) Se. eo pp ey SC ERAS RSP bark has a very regular mm .._ S34 aes Sas WA U} o. ps 5 h] structure, in which layers ; a A, ‘ACI, of porous bark parenchyma spicata er i pas alternate regularly with Ose se ae | C7 Ts ms iS A gan 3" sus flat bands of slender cells Rah Reed | po Nese eel . . . Can ‘Q eT) (1) which might be differ- b-.-Seeer Te Nise | LES abate i . , an aT eh Se entiated as “wedge-cells.’ seell ly é 82 - -- SHAS 2 These slender cell bands ee W Sesess al would correspond to the AX \ eseaill | } SES) | secaill “pressure wedges” men- rp. \ . . . . ae, a tioned in connection with Ee ih the tan disease. The cells Co eS i forming these wedges ap- ie 22S pear m longitudinal section ~~ ——-—~ Ss=2S " ; : a= FOOD Le) as long as in cross-section, Trees Ail\inesoaraase’ i 3 LABIA Poa nearly colorless, with pe- Pe ex ae Wc =i : : So an) = Onn BAe culiar, wide-meshed wall e salt Ne HOU ) Paar Nine a dal Cee va g og . OOK, : ‘ thickenings, looking like % ___ el ¢ Bil irregular wedges. The ee At AS sasull parenchyma lying between ag every two such thin, slen- der bands of wedge cells is proportionately large-celled, porous and rich in starch. Deposited in it are large, hard bast bundles, (b) with the rows of calcium oxalate crystals accompanying it (0) and the cells (s/) containing mucilage. Vig. 46. Elm bark with bark excrescence. (Orig.) 330 These alternating tissue layers are separated by broad curved medul- lary rays (mst) which even in the entirely healthy bark can exhibit a wavy course, but in the diseased bark may often be displaced and take a hori- zontal course. The sharp curvature is caused by the spreading apart of the parenchyma cells which, containing chlorophyll and lying between the slen- der bands of wedge cells, elongate into pouches, and for a long time contain a great deal of starch. They also press outward the hard bast bundles and the rows of oxalate crystals. This great layer of separation is covered by a plate cork layer extending irregularly into the tissue and often accompanied by full cork (¢) and the suberized bark tissue cut off by it which belonged to the earlier period of growth (k). The cork layer often curves spherically into the pouch-like spongy tissue (sp) and forms the hard, crater-like points on the under side of the loosened bark scale, which were mentioned at the beginning of this description. The process of loosening the bark tatters is completed on the boundary between the hard tissue of the suberized cortex of the previous year, and the soft pouch-like parenchyma. The upper sur- face of the separating cushions appears woolly and rough, or smooth, according to whether the pouch-like parenchyma clings more or less strongly to the separating surface. In the elongation of the parenchyma these out-pushings differ from the tan disease in which cork excrescences are concerned essentially. von Tubeuf! describes a case of the Weymuth pine very similar to that on Ulmus, only no shedding of the bark strips could be observed because of the smoothness of the bark. The pine was diseased and covered with cushions of Xanthoria parietina. Among these lichens were found blister- like processes, of which part appeared to be split and were produced by a distention of the bark tissue. The resin ducts were enlarged, the deeper bark parenchyma cells elongated into pouches and poor in chlorophyll. von Tubeuf’s statement that he had produced very similar knob-like processes on a branch by wrapping it with cotton wadding which was kept constantly moist, warrants the assumption that, in the cases above described, we perceive the action of a local excess of water. The same kind of processes as these in the bark have been observed on roots also. Some years ago a serious disease of the grapevine was re- ported from near Lindau’. Its effects were similar to those caused by the rust fungus, but it could not be proved to be of parasitic origin. The part of the trunk beneath the soil and the older roots exhibited tears 1 to 3 cm. long from which protruded calluses, white at first but later turning a chocolate brown. The lateral roots near these calluses died. The calluses consisted of bark parenchyma cells abnormally lengthened radially and scarcely connected any longer. The American varieties, scattered among the diseased European vines, were found to be unaffected. As is well- 1 y. Tubeuf, Intumescenzenbildung der Baumrinde unter Flechten. Naturw. Zeitschr. f. Land- u. Forstwirtsch. 1906, p. 60. 2 Kellermann im Jahresber. d. Sonderausschusses f. Pflanzenschutz. Arb. d. Deutsch, Landw.-Ges. 1892-93. oot known, the extremely luxuriantly growing American vines consume much greater amounts of water. Tissue warts of this kind are much more abundant than is generally assumed and occur also on decorative plants’. They are reactions of the plant body to a wound stimulus or internal disturbances of equilibrium in the supply of water and nutritive substances. W ATERSPROUTS. By the term watersprouts, watershoots, or suckers, are understood ex- ceedingly vigorous foliage shoots with long internodes, which grow up perpendicularly from old branches or trunks. Often trunks covered with lichens are distinguished by abundant sucker formation. Since the suckers grow up into the crown of the tree, they produce wood, and, indeed, un- fruitful wood, at the very places which it is desirable to keep free from branches in order that sufficient light and air may reach the inner part of the crown. It is not advisable, however, to remove the suckers, if the cause of their formation is not removed at the same time. In many cases the cause may be found in an impervious subsoil. The roots of the vigorous tree reach this impenetrable layer sooner or later, which not infrequently is a vein of closely cemented sand containing iron. The absorption of food stuffs is limited by this, the tree forms orly short shoots and smaller leaves, but still bears fruit. In a warm and damp spring, when all trees make a strong foliage growth, the energy of the weakened tree also appears to be increased by the favorable vegetative conditions. The strong upward force of the water causes the formation of adventitious buds or stimulates dor- mant buds, especially those not too far distant from the central trunk, since the upward force of the water and the nutrition is much more energetic in a perpendicular direction than in the more inclined position. Gardeners know how to turn this to use in growing plants on trellises. The horizontal branches on one side of the main trunk, which are weaker than the corres- ponding ones on the other side, are held in a perpendicular position for a year. This treatment results in a much greater and more rapid growth and development. With the production of water shoots a gradually in- creasing inequality in nutrition sets in, at the expense of the older, more horizontal branches which now suffer from scarcity of nourishment. This explains the death of the tip twigs of older lateral branches which begins with the appearance of the water shoots. One part of the tree starves when some other part develops very luxuriantly. As has been said, it is scarcely advisable to remove the water sprouts during such a disturbance in the equilibrium of nutrition, rather, it is more advantageous in older trees to graft them with valuable varieties and, at the same time, to saw off a part of the older branches, so that the tree is thus rejuvenated. In places where the sub-soil cannot be opened up easily 1 Sorauer, P., Uber Rosenkrankeiten, Zeitschr. f. Pflanzenkrankh. 1898. p. 220. oo6 the evil can be checked for a considerable number of years by using ferti- lizers at some distant from the trunk. The tree in its endeavors to reach the fertilizer develops a new vigorous root system. Young trees can be entirely cured by transplanting. It must also be emphasized that the formation of suckers disappears of itself from many trees after a few years. This is the case where such water sprouts have been induced by an excessive pruning of the tree or the sudden dressing of the trunks. In avenues of trees, or along streets with telephone wires, and in tree plantations, through which a street or railroad line has been cut, a strong development of suckers is found on the sides of the trees toward the street. In such cases large branches are often sim- ply chopped off on the side toward the street. Since the root system remains unimpaired, it pumps up just as much water as before the tree top had been reduced. By the removals er the branches, however, there is less consumption and consequently dor- mant buds are awakened Fig. 47. Fasciated branch of Picea excelsa. which mature into slen- ee oP ; der shoots, becoming fhe original band-like shoot (7), in one year, has developed three suc- ; cessive stages which sprout out from one another (2, 37,7). (a) Bud water sprouts whose seales. (% natural size. After Nobbe.) buds often sprout even in the year of their pro- duction. . Th. “antiga has observed that these Cross-section of the fasciated spruce branch. Premature shoots de- velop no basal buds. A through the upper part of the branch; & through the lower part: (a) bark with needle cushions; (4) wood; (yv) pith. (Natural size. After Nobbe). If suckers are pro- duced by the sudden re- moval of large branches from the crown, their formation may be retarded by creating other diverting centers by scarification. In the spring pruning of branches, scarifying will, indeed, prevent the formation of the water shoots. In the same way, chopping into a vigorous root near the base of the trunk at the side where the tree crown has been greatly thinned out, will decrease the supply of water and prevent the sucker formation. 1 Vollstiindige Naturgeschichte d. forstl. Kulturpflanzen, p. 176. Boo UNION OF PARTS. We may likewise consider as due to local over-nutrition the con- dition arising when a cylindrical branch becomes broad and flattened. It then looks as if a number of branches had grown together; nevertheless, this is only rarely the case, for almost always only a single branch is in- volved which, by broadening its vegetative point, no longer has a vegetative cone at its apex, but a comb-like vegetative surface’. In the illustration of a spruce fasciation here given (Fig. 47) we recog- nize the fact that the broadened axis is a single unit, first by the continued { Fig. 49. Fasciation of Alnus glutinosa. (4% natural size. After Nobbe). spiral position of the needles, especially at 7 and 2, and further in the cross- sections A and B (Fig. 48), of which the pith and wood form a single connected, uniform surface, and do not show any possible coalescence of many single adjacent rings, as must be the case where fasciation is produced by the coalescence of many branches originally separated. This theory is not changed by a consideration of the fasciation of the alder (Fig. 49), in which, besides the unusually characteristic crook-like bending of the 1 Uber Pflanzen-Verbainderung. Referat in Bot. Zeit. 1867, p. 232. 334 branches, resulting from a one-sided increase of growth, we can also per- ceive the splitting of cylindrical branches from the band bodies which occurs more frequently in deciduous trees. Thus the material for many axes, which can be isolated, lies accumulated in the fasciated stem, while the stem itself is a unit. We can speak only hypothetically as to the production of the fasci- ations, which are characterized as hypertrophies by the great increase of the leaves and cords of the leaf spurs. An axis, which fasciates later, must originally have suffered some arrestment. We have seen already in roots held fast between split rocks that pressure from two opposite sides may give the axis a band-like form. Under certain circumstances such a changed direction of growth may continue if the cause of arrestment itself has dis- appeared. Thus Treviranus cites an observation on the stem of Tecoma radicans which had become band-like from pressure against the wall, but still remained band-like, after it had grown far out over the wall. Here the branches, which developed further, also became band-like in places. Besides such lateral pressure, in other cases a transitory pressure from above may also probably cause a broadening of the vegetative point into a vegetative surface, and such pressure can possibly be produced by the ab- normal behavior of the bud scales (delayed loosening due to resinification, drying, etc.). In case no abnormal increase of pressure occurs, direct in- juries to the vegetive tip may cause the increase of the vegetable points. If the fasciation has once been produced, it can be propagated by cuttings ; even under certain circumstances it can be proved constant in the seed, as is seen in the favorite garden plant, cock’s comb (Celosia cristata). The capacity for fasciation may be presupposed in all plants and actually observed cases have been reported in great numbers (150) by Masters’. As mentioned already, the fasciated growth produced by a band-like fasten- ing together of isolated axes, should be distinguished from real fasciation. Lopriore® has produced such cases artificially in roots. CoMPULSORY TWISTING (SPIRALISMUS Mor.). A. Braun* characterizes by the above name, those malformations of the stem which corsist of barrel-like distended places in which the grooves, extending down from the leaves and representing the vascular bundles be- longing to them, exhibit an extreme, spiral twisting. At times the barrel- like swelling is so great that the stem splits in the direction of the spiral twisting and divides into a number of spiral bands at these diseased places. Schimper has named this disturbance in growth “Strophomania.” The ma- jority of cases are known in the families of the Dipsaceae, Compositae and the Rubiaceae. Single examples are described also. for the Labiates, 1 Masters, Vegetable Teratology, 1869, p. 20. (Compare Penzig and the isolated cases in the Bot. Jahresberichten.) 2 Lopriore, G., Die Anatomie bandartiger Wurzeln. Cit. Zeitschr. f. Pflanzen- krankheiten, 1904, p. 226. 8 Sitzungsberichte naturf. Freunde z. Berlin. Cit. Bot. Zeit. 1873, p. 11 and 20. 399 Scrophulariaceae, Cruciferae and, among monocotyledons, Asparagus, Lilium, Orchis, Triticum, etc., and also in Equisetum. We think it justifiable to consider the compulsory torsion: as a fasci- ation which has swollen up like a barrel. The cases have no agricultural significance. Differing from them is the increased spiral twisting of normally con- structed woody trunks, which we trace to an arrestment of the growth in length (usually resulting from a lack of water and nourishment). Dropsy (OEDEMA). a). In SMALL FRuits. Since the propagation of standard gooseberries and currants by budding on vigorous shoots of Ribes aureum has found wider distribution, there has been a great increase in the complaints of a disease of the stock which makes doubtful the success of the budding. This disease has been called “dropsy” by growers and consists in the appearance of closed bark tumors, i. e. of bark swellings entirely covered by the outermost cork layers, or of swellings rupturing later (Fig. 50 4). These swellings of the bark are sometimes small, but they may reach an extent of several centimeters. They are formed either on one side of the trunk or surrounding it, spreading into one another. They appear most abundantly on wood two or more years old, yet they can also occur in great numbers on branches one year old and directly cause their death, while the wood of the older branches may become diseased, to be sure, but does not directly die. When, as is the custom at present, Ribes is grafted indoors in the spring, rupturing tumors are found frequently directly below the place of budding. In such cases the bud does not grow. But in extreme cases the same kind of swellings may also be found further back from this place, on the trunk between every two buds, as well as near the buds or, rather, the branches already developed from them. Cases are observed in which the base of a shoot left standing on wood one or two years old, has swollen up like a barrel and is covered by loose, hanging strips of bark. The branch above this place is dead. As soon as the bark layer, which forms the outer skin of the branch and covers this fresh swelling, has split, the swollen place, pushing out from under it, exhibits a yellowish, spongy, soft, callus-like tissue-mass con- sisting of cells, elongated to pouches, very poor in contents but rich in water. (Fig. 50 B s). This is the former normal bark of which the cells beginning in the region between every two groups of bast cells (Fig. 50 B b) have elongated extraordinarily in the direction of the trunk’s radius at the expense of their contents, otherwise rich in green coloring matter. They have partially separated from one another, and, by their constantly in- creasing extent, have finally ruptured the outermost oldest bark layers 336 (Fig. 50 B e k) which no longer participate in the changes and are sep- arated prematurely by the cork layers (k) from the tissue lying beneath them’. The full thickness of the bark is not always attacked by the pouch-like elongation; in very severe cases, however, even the cells of the cambial region are deformed (c). The wood is no longer normal. Instead of normal mature wood, consisting of thick-walled, elongated wood cells and ducts, Fig. 50. Dropsy in Ribes aureum. (Orig.) with cross walls broken through like ladders, a wood is produced, composed of short, broad, comparatively thin-walled, parenchymatous cells (hp). The cross-section (Fig. 50 B) shows the transition of the healthy side of the branch (NV) into the dropsical side (W) ; h indicates the normal wood. At the time when the layer st was produced, the disease manifested itself in the 1 Compare Sorauer in “Freihoff’s Deutsche Girtnerzeitung”’ August 1, 1880, and Goschke in Monatsschrift d. Ver. z. Beférd. d. Gartenb, October, 1880, p. 451. Jo7 cambium and the result was that, from there down on the diseased side, parenchyma wood (/ p) was formed which at the left ended in a medullary ray (m). Still further towards the left, normal wood was produced at the same time. The same difference is found in the youngest bark parenchyma (rp). Because of the great radial elongation of the cells on the dropsical side (W) the hard bast cords (b) are pressed out like bows and the cell rows, containing calcium oxalate (0), which accompany the bast body, have also been correspondingly misplaced into steeply ascending, irregular rows. At chil are groups of parenchyma which have remained rich in chlorophyll. It is evident that this loose structure of the tissue, rich in water, which forms the swelling, has no great permanency. In dry places and with increasing dryness in the air, this tissue turns brown rapidly, shrivels, collapses and forms a soft, brown mass, part of which remains clinging to the wood, while part sticks to the outer bark tatters which roll back in times of drought and spread out, gaping, from one another. Such stems of such plants then have a rusty appearance and are best excluded from cultivation. Because of the ease with which such stock can be grown on strong soils, the loss from the disease would be less important, if it did not attack directly the potted specimens which have been budded and if the number of budded plants was not considerably decreased thereby. I am not of the opinion, often expressed in general practice, that an over-abundant feeding of the plant is to blame, but I think that an excess of water makes itself felt in some places on the axis. If there should be an accumulation of plastic food material here at the same time, it would manifest itself preferably by an abundant cell increase. But this is not the case. If the cells on the healthy and on the diseased sides are counted, only an insignificant preponderance is found on the side attacked. Accordingly, an abnormal cell elongation is chiefly concerned here. This is explained by the treatment of the Ribes stems during the preparation for budding. In order to obtain slender stems, growing tall rapidly, the other sprouts, produced at the sides, must be removed and even the lateral branches on the young stock must be cut back. If now the stock is well rooted, it will grow rapidly in the greenhouse and the buds, scantily present because of the earlier pruning, are still fur- ther decreased by the fact that the shoots developing from them are cut back or entirely removed. By cutting off the branches, the amount of water forced up by the water pressure is increased in the main axis and manifests itself in a pouch-like elongation of the younger bark cells and in the forma- ion of tumor swellings which finally rupture. My attempts to produce dropsy by abundant watering and the rapid forcing of well-rooted specimens in the greenhouse, together with a con- tinued removal of the developing lateral shoots, gave very favorable results. The disease will be prevented if the budded stock is not forced too rapidly and the sprouts from the bud are cutting back carefully, but not 338 entirely removed. Maurert has recommended the use of Ribes nigrum in- stead of R. aureum for budding stock. However, I have also known of cases of excrescences on the axes of the black currant, especially after the transplanting of such plants as tend to sterility. b). In STONE FRuvITts. It may be foreseen that, with the present methods of culture, phenom- ena ‘similar to those observed with Ribes, will also appear in other vari- eties, for our fruit trees are becoming more and more delicate, due to the great increase in nutrition supplied them. The mass of the parenchy- matous branch substance increases constantly in comparison with the prosenchymatous. tissues. Between unbudded, wild stock, and budded varieties there are considerable differences. Direct measurements have shown me that the branches of the cultivated varieties acquire a fleshier bark while the wood ring decreases considerably in thickness?. I have called this increasing tendency of our fruit trees to form soft, parenchy- matous tissues, storing up reserve substances, at the expense of the breadth of the wood ring, “parenchymatosis.” In special cases this change in development acquires such extreme pre- ponderance that diseases arise. I observed such diseases especially in the fruit wood of pears which is often shortened up to barrel-like fleshy swell- ings; growers call these “Fruchtkuchen.’ The morbid disturbance con- sists either in the shedding of the cork layers and outermost bark layers in shield-shaped pieces from the side of the branch, thus showing a greenish yellow callus-like tissue mass, or in the uplifting of the bark itself in stiff, crumbly scales, like rings extending almost around the whole branch, with similar changes in the tissues. In the latter case, all the branches found above such a place are dead. If the diseased condition manifests itself in a less luxuriantly developed fruit wood, which may be distinguished from the “Fruchtkuchen,” as fruit Spears, a complete casting of these twigs was often found resembling that of the normal dropping of the twigs observable every year in poplars. In the present abnormal dropping in pears, the exposed surface was not smooth but uneven and woolly, light colored, however, like the cross-section of healthy wood. A cross-section through a place in the branch which is found in the first stages of the disease, shows that the bark has developed strongly on one side, especially within the primary bark. Its parenchyma is thin-walled, vesiculated in places or pouch-like and extremely porous. A comparison of the pith in a branch which has split and in a healthy one of equal age shows that the former is one-third larger than the latter, while the wood ring is only one-third as wide. Significant structural differences are connected with these misproportions. While a healthy shoot shows l Der Obstgarten, 1879, p. 182. 9 2 Sorauer, P. Nachweis der Verweichlichung unserer Obstbiume durch die Kultur. Zeitschr. f. Pflanzenkrankh. 1892, p. 66, Jo normal libriform fibres and an abundantly developed vascular system, the wood of the diseased branch is made up almost exclusively of parenchy- matous thin cells, between which the vascular cords are deposited. In normal trees, under certain circumstances, the weakness of the wood ring can be compensated for by schlerenchymatous elements in the bark’. The dropsical branches of pears differ from those of Ribes in that the wood body is also involved in the parenchymatosis and entirely broken up. By the rounding up and dilation of the wood cells, which have become par- euchymatous, the ducts are gradually curved, displaced and finally torn. Just as soon as the loosening process has affected the whole extent of a fruit spear, or a ““Fruchtuchen,” dropping follows. The diseased branches came from trellised trees in a well watered garden, richly fertilized with cow-manure. Even if such extreme cases are less frequent, yet the first stages, con- sisting of the widening and excrescence of the medullary rays and the pro- cesses of elongation in various groups of bark cells, are often observed. SWELLINGS ON THE ST. JOHN’s BREAD TREE. Swellings often appear as a result of cell elongation and cell increase. Savastano” reports thus, for example, of the outgrowths on the branches of Ceratonia Siliqua. Conical outgrowths, rich in tannin, are found at the tips of the flower stalks, causing atrophy of the blossoms. In an earlier study®, he describes the production of larger swellings on the St. John’s Bread tree. On normally developed fruit branches, in the beginning of the disease, the fruit falls in the first stages of development and the remaining basal part of the axial cone begins to swell. The repetition of this process in succeeding years produces a knotty swelling which can attain a very con- siderable size and a height of 6 to 10 cm. The bark of this hypertrophied tip of the fruit twig is often seven times as thick as that on the normal fruiting wood and the wood itself consists of ductless wood parenchyma. In the almost pithy bark, the bast fibres have wider lumina and take an unusual course. The medullary rays are twisted, the wood ring is often bent. In the parenchyma, various cell groups with discolored walls and a gummy content are recognizable. From the beginning of the disease, the tannin content of the swelling increases, causing a distinct disturbance in lignification. | A case described by Vochting* in Kohlrabi plants may be mentioned here. If all the vegetative points were removed, the leaf cushions swelled to extensive structures. In the normal wood of the axis, as in the leaf cushions, the cambium developed thin-walled xylem elements. In similar 1 Pieters, A., The influence of fruit-bearing on the development of mechanical tissues in some fruit trees. Ann. of Bot. Vol. 10. London, 1896. P. 511. 2 Savastano, L., Tumori nei coni gemmarii del carubo. Boll. d. Societa d. Naturalisti in Napoli. 1888. Vol. II, p. 247. 3 Savastano, L., Hypertrophie des cénes & bourgeons (maladie de la loups) du Caroubier. Compt. rend. 12. Janv. 1885. 4 Vo6chting, H., Zur experimentellen Anatomie, cit. Bot. Jahresb. 1902. II, p. 300. 340 experiments with Helianthus annuus Vochting found little tubercles formed on the roots. I observed barrel-like thickenings of the sharply bent roots of sweet cherries. The swellings, described by Warburg" in the branch canker of the kina tree on damp soils, may also represent such correlation phenomena. RETROGRESSIVE METAMORPHOSIS (PHYLLODY). If the organs of a morphologically higher developmental stage seem transformed into those of a lower one, we speak of a retrogressive meta- morphosis. The change in the blossoming organs is pathologically of mo- ment only if the sexual apparatus, by changing into a group of vegetative organs, loses the purpose for which it was designed and thereby initiates sterility. These cases are listed under the group of phenomena caused by excess of water and nutriment, in accordance with the following theory. The development of the vegetable organism depends upon two factors, the con- stitution of the organic building materials and the way in which they are utilized. With the assumption that the first achievement of the organism,— assimilation, i. e., the formation of new dry substance,—takes place in a normal way, the development of the plant depends upon the way in which this organic building material is utilized. In this we recognize two directions which we will keep separate as the vegetative and the sexual generations. © The latter is initiated usually by the appearance in the organism of an often clearly recognizable dormant period in the production of its vegetative apparatus. As a rule, new leaves are not formed at this time, the apical growth of the twigs stops. In place of this the process of the storage of reserve building material becomes conspicuous. We find this storage process initiated and favored by a decrease in - the absorption of water with increasing light and heat. An increased con- centration of the cell sap is required, if the reserve substances, for ex- ample, are deposited in the form of starch. If such a concentration cannot be obtained under any circumstances whatever and the building substances remain in a diluted form,—for example, sugar,—only a slight impetus is necessary to start up vegetative activity. Thus, a certain antagonism pre- vails between the two developmental phases, which we may consider as transmissable adaptations to atmospheric conditions. After a cool wet period when the plant takes mineral substances from the soil and through the production of the leaves causes the chlorophyll apparatus to attain to its richest possible development, a warmer, drier period follows which makes possible the greatest amount of light. In this period the sexual organs are formed from the finished, plastic building materials prepared in the leaves and develop further, after a shorter or longer dormant period. 1 Warburg, O., Beitrag zur Kenntnis des Krebses der Kinabaéume auf Java. Cit. Bot. Centralbl. 1888. Vol. XXXVI, p. 145. 341 The more the plastic material is worked up by the leaves, the more numerous and perfect are the sexual organs formed within this dormant period. The manner in which these primordial buds subsequently develop depends on the nature of their further nourishment. If influences make themselves felt which are necessary for the maturing of the vegetative organs, foliage leaves will develop and, indeed, either from the newly formed centres or from the already existing primordia of the sexual gene- ration. Thus “phyllody” takes place. From our experience in horticulture, we know that an abundant supply of nutritive substances with a simultaneous increase in warmth and mois- ture, usually at the time of a lesser light action, are conditions initiating and favoring the process of phyllody. This becomes especially apparent in the production of double flowers, in which the stamens are transformed into petals. Since this process can become hereditary, like all changes in the di- rection of growth, where conditions remain equal, and may be increased, it is evident that we will find examples in which the tendency to the retro- gression of the sexual organs into forms of morphologically lower develop- ment, has affected all parts of a flower, and then the whole blossom turns green, Of course, the influence of the soil is rarely the direct cause of phyllody. This is due rather to definite combinations of all the factors of growth, as already mentioned, and also occurs not infrequently as a correlation phe- nomenon resulting from the suppression of other processes of growth. Thus phyllody of individual flowers and inflorescences is produced by injuries to the vegetative axis and by vegetable and animal attacks (mites). For example, C. Kraus’ removed leaves from Helianthus annuus plants of differ- ent ages, leaving only the bracts of the blossom head. In the older plants the bracts curled back and enlarged prematurely. In the younger plants 25 per cent. showed an actual phyllody, since the bracts assumed, more or less, the form of foliage leaves. In my freezing experiments, I have often observed that the bud scales were transformed into herbaceous, leaf-like organs after the apical portion had been destroyed by frost. Goebel’ obtained similar results by removing the leaves of young plants of Prunus Padus, Aesculus, Rosa, Syringa and Quercus, and then putting the plants into plaster casts. Teratology has classified the phenomena. The simplest case is “wirescence,’ turning green, in which an organ of the flower retains its form in all essentials, but becomes green in color. As a rule, the organ be- comes fleshier with this appearance of the chlorophyll coloring matter. In the actual metamorphosis of the floral organs into leaves (phyllody, phyl- 3) 1 Kraus, C., Untersuchungen tiber kiinstliche Herbeifitihrung der Verlaubung usw. durch abnorme Drucksteigerung. Forsch. auf. d. Geb. d. Agrikulturphysik. 1880, p. 32. 2 Goebel, Beitrage zur Morphologie und Physiologie des Blattes. Bot. Zeit. 1880, p. 8038. 342 lomorphosis) the organ also approaches the foliage leaf in form. Bracts become normal stem leaves, the sepals are replaced by actual foliage leaves, the petals become green and fleshy, the pistils become stamens (staminody) or the stamens and pistils assume the character of petals or green, fleshy leaf-like structures, as, for example, in the double cherry, the doubie Ranunculus, etc. In mignonette, through phyllody of the ovules, little leafy axes can be formed in the urn-like open ovule cases. In the favorite tub- erous Begonias, I found that the placentae had grown out of the ovule cases and the ovules carried over on to petal-like transformed branches of the pistil, ete! There are cases in which all the parts of a flower are transformed into small, uniformly green leaves, i. e., a complete green flower condition (chloranthy) arises. One of the best examples of this is the green rose (Rosa chinensis, Jaqu.), received in its time with great enthusiasm, the transformation processes in which have been thoroughly described by Celakowsky!. I would like to introduce here also parthenogensis, which various scientists have often proved recently to be of constant occurrence. Kirchner* saw in this an arrangement “which, differing from the much more wide- spread, spontaneous self-pollination, serves to assure the development of seed, capable of germination, in cases where, for any reason whatever pollination has become uncertain or difficult.” Even those seed primordia can be assumed to be of a somatic character, in which, at the time of the production of the embryo sacs, the reducing division is suppressed and the — egg cell retains a vegetative character. In cryptogamic plants Apogamy corresponds to the process of phyllody in the phanerogams. Instead of the sexual products, vegetative organs appear here, as in Athyrium Filix femina var. cristatum, Aspidium falcatum and Pteris cretica. It is said that in the last plant, no more female sexual organs are formed at all, but the young plant is produced from a vegetative sprout exactly on the places in the prothallium, where the archegonia must have stood®. Such plants which “produce their young alive” (viviparous) furnish abundant material for propagation, just as, for example, the bulblets of many lilies, produced by the transformation of a flower. THE BARRENNESS OF THE Hop. A special process of phyllody, of great agricultural significance, is the barrenness, the blindness, the fool’s head formation of the hop. The names designate only different degrees of a malformation which begins with a simple, abnormal lengthening of the catkins and develops into the formation 1 Celakowsky, Beitrige zur morphologischen Deutung des Staubgefafses. Pringsheims Jahrb. 1878, p. 124. 2 Kirchner, O., Parthenogenesis bei Bliitenpflanzen. Ber. d. Deutsch. Bot. Ges. 1904, Vol. XXII. Generalversammlungsheft. Here also a bibliography. 3 Noll in Straszburger’s Lehrbuch der Bot. 1894, p. 243. 343 of fluttering, dark green inflorescences on which develop foliage leaves, differing in size and varying in numbers. nt hy IN ‘ JX Y \ SS A H BH Lip S t qs Nail = See De 7 7 ze ul yy! / = id Tp, L 3 wt ma Z y, 4 =: ~IAZs Lo, Wl GF “a iit arr ~ ! aa A Yate nh nM Fig. 51. Different transitional stages between the normal hop catkin and a leafy one. (Orig.) Hop growers know that the quality of the hop decreases according to the increased length of the catkin and enlargment of the bracts. The de- velopment of the catkins, most advantageous for technical use, is a short, 344 compact form of the whole inflorescence and a short, broad form and papery, thin consistency of the bracts, as shown in the preceding Fig. 51, Nos. 7 and 2. Half of the leaves have been removed in No. 2, in order to show the short- ness of the joints in the catkin spindle. Nos. 3 and 4 show the abnormal excessive lengthening of the catkin, known among growers by the name “brausche” hops, which must count as the first stage of phyllody. Such “brausche” hops are coarse, contain less substance, ripen somewhat later and have more herbaceous bracts. Beginning with this condition, the phenom- ena of phyllody increase up to the stage shown in No. 5. The green foli- aceous leaves, which here become visible, attain at times the size of a nor- mal leaf. b is the leaf blade which may be followed back into the petiole. At the base of this petiole stand the two green lateral leaflets (m,n) which in the present basal part of the catkin are very small, but increase in size up- ward. No. 6 is taken higher up on the inflorescence and shows the lateral leaflets (,) in a size equal to the other bracts, while the leaf body (6) is much smaller. The remaining bracts and protective leaves are seen at No. 5. Each one encloses a flower. The scale leaves, which exceed developmentally the other leaves and are developed only in the normal female inflorescence of the hop have the same bract-like constitution as do the protective leaves, so that the whole catkin seems composed of uniformly developed bracts. All the bracts are short lived and soon become dry skinned, when they lie over one another like tiles. The barrenness consists, therefore, of the development of the otherwise suppressed leaf blade between every two bract-like leaves. Wide exper- ience now shows that damp years’ and soils strongly manured with sub- stances containing nitrogen cause the more extensive appearance of the barrenness. Frequent summer rains, resulting in cloudy days, are often injurious, even without directly producing the disease. The cells of the leaf, as weli as the axis, then elongate and even if favorable harvest weather occurs, the catkins ripen only superficially. They are brought into the storage rooms while containing much more water of vegetation, thereby causing a very rapid heating of the whole heap. Consequently, even in well- developed catkins, a rapid loss of the peculiar gloss and the light green color takes place, together with a considerable reduction in value of the whole harvest product. As a remedy for the barrenness, the removal or checking of the causes must be attempted, in case these are found in the soil in the form of excess of water or nitrogen. If the cause is cloudy, damp air, all means should be utilized which further the greatest possible ae€ration and illumination of the hop-plantation. If nitrogen is present in the soil in excess, a subsequent fertilization with superphosphate is advisable. 1 Beobachtungen iiber die Kultur der Hopfenpflanze. Published by the Deut- scher Hopfenbauverein, Jahrg. 1879-82. 345 FORKED GROWTH OF VINES. It may be noticed in various localities, that different varieties of vines assume a tendency to excessive branching and retain it hereditarily. The kind of false ramification appears as a forking of the vines and such dis- eased plants are usually little if at all productive. Rathay' published the most thorough observations on this subject and corroborated these state- ments in lower Austria. The wine growers there, who call these branch- sick vines “Forks,” or “Double tipped,” state that the forked formation may commence in very different places. The vines which in adjacent groups usually begin showing this abnormal direction of growth, first develop scattered forked branches and in this way present a ‘‘spurious forking’ as may be seen everywhere in luxuriant vineyards. This initial stage of the disease is not dangerous, since the plants frequently return to a normal growth. The danger begins with the spread of the disease over the whole plant. Correlated with this is the transmissibility of the disease. This has been demonstrated in cuttings and suckers of affected vines. No cause of this phenomenon can be given as yet with certainty. Rathay was convinced that parasites were not present. The opinions of practical workers disagree greatly. Some think that exhaustion of the soil by intensive grape culture is the cause, while others are of the opinion that a clogging of the soil due to heavy rain storms or to the working of the soil during and soon after rain has an injurious effect. In my opinion this disease is a phenomenon of turning green—vires- cence—i. e., a morbid increase of the vegetative development. Kaserer’s* statements favor this hypothesis. He states that, the first evidences of the disease are found in the transformation of the covering bract of the tendrils into a small leaf, the most advanced stage in the trans- formation of all the tendrils into leafy shoots. In grape vines, the tendrils are axial organs, of which the development depends upon the amount and constitution of the organic building materials present. In younger vines they become herbaceous shoots, but in older ones develop into inflorescences at the lower buds. If all the tendrils are transformed into leafy shoots the vegetative development will predominate, a morbid condition. The building material present is wrongly utilized. The cell sap necessary for the formation of the sexual organs is not properly concentrated. Thus far it is possible to agree with Krasser*, who speaks of a diseased condition of the protoplasm in certain regions as a cause of this “herbaceousness.” If Krasser, referring to the works of Kober and Gaunersdorfer (1901) insists that no disturbances in conduction and no lack of nutritive sub- stances can be assumed as causes of the “herbaceousness,”’ which represents 1 Rathay, Emerich, Uber die in Nieder-Osterreich als “Gabler” oder “Zwiewip- fler’ bekannten Reben. Klosterneuburg, 1883. 2 Kaserer, H., Uber die sogenannte Gablerkrankheit des Weinstocks, Mitteil. Cink. ks chemisch- physiol. Versuchsstation Klosterneuburg, 1902. Part 6. 8 Krasser, Fridolin, Uber eine eigentiimliche Erkrankung der Weinsticke. II, Jahresb. d. Ver. d. Vertreter d. angewandten Botanik. 1905, p. 73. 346 only a metamorphosis of scattered buds into leaves, but that a very local affection of the cells of some buds is present, this does not upset at all our theory of phyllody. It is a matter of course that the formation of each organ takes place under definite nutritive conditions. That these change constantly and are the product of the momentary combination of all the factors of growth has been emphasized already in the introductory chapters of this edition. It is still far from possible to determine these combinations. For the present, we have only scattered observations on this subject,—that, for example, an excess of potassium and nitrogen in relation to the con- sumption of the other nutritive substances one-sidedly increases the vege- tative activity at the expense of the sexual development. An excess of water with a relatively scanty supply of light can in a similar way influence the direction of growth. We cannot determine how these disturbances in equilibrium are produced individually for the formation of each organ, whether momentary arrestments in the absorption or transportation of the nutritive substances form the cause. | We can, therefore, state only very generally that phyllody is. produced by a preponderance of the direction of growth producing green leaves as against the mode of growth favoring the sexual organs. The so-called “changelings’ or spurious forkings,- are plants which are still partially fruitful. Among the conditions favoring the tendency to phyllody, Kaserer cites unfavorable positions on which drainage water collects from higher lying ground. Healthy plants set out in a group of affected plants are said to fork rapidly. Superphosphate seems to favor a return to fruitfulness. We consider the replacement of diseased plants by healthy ones of varieties which withstand a more abundant supply of water and heavier soils to be the most advisable mode of procedure. The so-called aggregations of forked plants might be improved by drainage and the addition of sand together with that of calcium phosphate. FALLING OF THE LEAVES. The falling of the leaves, the normal result of age’, is of pathological significance only because, under certain circumstances, it can appear prematurely. The causes which may lead to such premature dropping of organs are of different kinds, and extremes of weather may give rise to it. Ac- cordingly, the phenomena could be treated in different sections of this book. Nevertheless, we prefer to consider here the processes of loosening as a whole, because they are connected with changes in the tissues, in which in- creases of turgor occur decisively, after the organs, for any cause whatever, have become functionally weak. In regard to the falling of the leaves, for example, Wiesner? differentiates the falling of the leaves into a swmmer 1 Dingler, H., Versuche und Gedanken zum herbstlichen Laubfall. Ber. d. Deutschen Bot. Ges. Vol. XXIII (1905), p. 463. 2 Wiesner, Jul., Ber. d. Deutschen Bot. Ges. Vol. XXII (1904), p. 64, 316, 501. Vol. XXIII, p. 49. 347 falling, fallixg due to growth, falling due to heat and falling due to frost. Pfeffer! gives us an insight into the diversity of the causes. “Such a hasten- ing of the leaf-fall is brought about, for example, by insufficient illum- ination, also by an insufficient water provision and by too high a temperature. Not infrequently, however, a premature shedding of the leaves is caused especially by the sudden change of external conditions, which for perti- nent reasons concern first of all the older leaves.” As examples of the injurious influence of a sudden change in the amount of transpiration, Pfeffer cites the sudden loss of leaves in plants as soon as they are brought from the moist greenhouse air into a dry room. Sharp changes of temper- ature, illumination, etc., can act in the same way. v. Mohl? has studied the anatomical processes very thoroughly. The shedding of leaves is accomplished by the formation of a trans- verse parenchyma layer at the base of the petiole, as a rule within the leaf cushion, and, in fact, usually where the cork of the bark passes over into the epidermis of the petiole, and in the interior of the petiole tissue, which is produced by a special cell division. The cells of this layer separate from one another in one plane. v. Mohl calls the zone in which the layer of separation is formed, the “yound-celled layer,’ because it consists of very short parenchymatous tissue, which toward the leaf body gradually passes over into the elongated cells of the petiole, but is sharply defined on the side toward the bark of the twig. In very many cases, a cork layer formed of plate-like cork cells, sep- arates the green bark of the branch, rich in chlorophyll and starch, from this short-celled parenchyma of the round-celled layer of the leaf cushion which usually contains no starch, and very little cholorophyll and turns brown at the base at the time of leaf fall. Schacht* considers this cork sheet, which, at the sides, passes over into the inner cork layers of the bark, to be the cause of the shedding of the leaves. In fact, it may be assumed that if a cork layer be shoved in between the tissue of the bark and that of the petioles, the food supply of the leaf is impoverished and the leaf gradually goes to pieces. Nevertheless, the cork layer is not the cause of the leaf fall, for v. Mohl has shown that it is not formed in many plants which cast their leaves. Thus, for example, no cork layer can be found in ferns with deciduous fronds (Polypodium, Davallia) further, in Gingko biloba, Fagus silvatica, some varieties of oak, Ulmus campestris, Morus alba, Frax- inus excelsior, Syringa vulgaris, Atropa Belladonna, Liriodendron tulipifera, etc. On the other hand, the cork layer is formed in Populus canadensis and P. dilatata, Alnus glutinosa, Juglans nigra, Daphne Mezereum, Sambucus racemosa, Viburnum Lantana, Lonicera alpigena, Vitis vinifera, Ampe- lopsis quinquefolia, Aesculus macrostachya, Pavia rubra and P. lutea, Acer 1 Pfeffer, Pflanzenphysiologie. II Edition, Vol. 2 (1904), p. 278. 2 vy. Mohl, Uber die anatomischen Veranderungen des Blattgelenkes, welche das Abfallen der Blatter herbeifiihren. Bot. Zeit. 1860, Nos. 1 and 2. 3’ Schacht, Anatomie and Physiologie, II, 136. 348 platanoides, Prunus Padus, Robinia Pseudacacia. The cork layer should, therefore, be considered only as a protective layer for the bark tissue ex- posed by the falling of the leaf, often developed before the leaf has fallen. The real layer of separation, in fact, is formed above the cork layer in the almost isodiametric parenchyma of the round-celled layer, not in the brown-walled portion bordering directly on the cork, but in the adjacent healthy portion, of which the walls are light colored. There, shortly before the leaves fall, a zone is found running obliquely in front of the bud toward the outer side of the petiole and composed of young, delicate walled cells with intercellular spaces containing less air. Small starch grains are found in these cells which otherwise do not occur in the enlarged end of the petiole. In this newly formed tissue-zone, the cells separate from one another with- out tearing, but by rounding off, as Inmann* has observed. One part re- mains attached to the petiole as it breaks off, the other to the leaf scar where it soon dries up. The leaf-fall, accordingly, is a vital act, not a me- chanical one. Before the leaf falls, vascular bundles take no part in the changes undergone by the cell tissue of the swollen end of the petiole. These extend through the round celled layer and the cork layer without changing their organization, even without turning brown. The cleavage in these takes place in a purely mechanical way after the split has extended through the parenchymatous tissue. In many plants (Nuphar, many monocotyledons, herbaceous ferns”) in which there is no cork formation on the leaf scar, its outer dried cell layers pass over directly into the healthy bark parenchyma and are thrown off during later development. v. Bretfeld® arrives at the conclusion that the process of abscission of the leaves is the same in monocotyledons and dicotyledons, only the shutting off of the abscission surface differs in different genera. An essential difference lies, however, in the time of the formation of the tissue zone in which the separating layer is produced. While in dicotyledons, the process of ab- scission is the product of living activity, taking place shortly before the leaves fall, this process in the tree-like monocotyledons, orchids and Aroideae is exhibited’ as an act prepared by the primordia of a definite layer and advancing with the general tissue differentiation. The loss of leaves occurring in conservatory plants of the her- baceous and bushy Begonias, of Cistus species and many Mytaceae and Leguminoseae from New Holland must be mentioned in discussing leaf fall due to an excess of water. The upward force of the sap is increased excessively by an abundant watering of the plants at the time of minimal leaf activity. The cleavage surfaces of the falling leaves at times are very mealy, due to the loosened cells of the abscission surface. IB OteAelite) Le50 sO eos. 2 y. Mohl, Uber den Vernarbungsprozess bei der Pflanze. Bot. Zeit. 1849, p. 645. p. 645. 3 y. Bretfeld, Uber den Ablésungsprozess saftiger Pflanzenorgane Bot. Zeit. 1860, p. 2738. 349 LEAF CASTING DISEASES. The leaf casting diseases form the most significant case of premature dropping of the leaves. We speak here in the plural, although it is custo- mary generally to call a sudden dropping of the needles of young pines “leaf casting.” All plants can “cast their leaves” which are capable in any way of pushing off their dying leaf apparatus. The only concern, then, is whether the leaf body in its entirety suddenly becomes functionally weakened, or even functionless. It is only because it appears so uncom- monly abundantly among pines and. is accompanied by severe results that the dropping of the pine needles is cited especially often for “Leaf Casting.” This form of disease manifests itself most frequently and severely in seedlings two to four years old, the needles of which suddenly become hrownish-yellow or brownish-red in the spring and fall after a short time. The considerable spread of this phenomenon dates only from the general change in the cultural methods; instead of sowing the seed and of the Femel management, the raising of plants in seed beds has been introduced. . Since that time it has been observed that in the months from March to May, often within a few days, great areas of seedling plants look as if they had been burned. In this, however, it can be noticed that young plants protected by a not very close conifer forest, or one of mixed trees, or, in nurseries protected by trees of an earlier seeding, do not cast their needles, while exposed areas in the open or in enclosed places are extraordinarily at- tacked by the disease. Specimens with pruned roots suffer more than those with long, vigorous ones, while plants on wet soil suffer most intensely. Mountain plantations are less attacked than those on plains and a northern exposure seems to be almost entirely spared, while a southern or western one suffers greatly. The disease does not appear every year, but generally only after wet, cold winters with but little snow, and alternating sharp frosts. The plants cast their needles most extensively 1f dry springs, March and April, are distinguished by bright warm days followed by cold nights. Often the phenomenon occurs in stripes or spots. It has been observed further, that ptants protected from the noonday sun by neighboring woods, etc., general- ly did not become diseased. Plants in seed beds, which were left covered until after the time of spring frosts, did not cast their needles while ad- jacent, unprotected seedlings did so. Seedlings grown between older covered plants or between broom plants, even those protected by high grass, did not develop the disease, while others where the broom plants had been dug out in the spring were attacked. Ebermayer’, in explanation of these facts, states that observations of a forestry experimental station, made for several years, showed that in March and April the soil temperature down to 11% meters was scarcely more than 1 Ebermayer, Die physikalischen Einwirkungen des Waldes auf Luft und Boden etc. Resultate der forstl. Versuchsstat. in Bayern. Aschaffenburg, 1878. Wola lean 25, 350 _5 degrees C., while the air temperature in the shade not infrequently was higher than 19 to 22 degrees C. Such differences in temperature between the air and the soil result directly in the excessive transpiration of the aérial parts of the plant, while the roots kept in a state of inactivity because of the cold soil, are incapable of taking up the soil water, or not to the amount necessary to replace the aérial loss. Thus the young pines dry up even when the soil is abundantly wet. The greater the difference between the soil and the air temperatures in direct sunlight, the more abundant and devastating is the leaf casting. On the other hand, the more frequently conditions arise which raise the soil temperature, such as warm spring rains, or which prevent a greater lowering of it, i. e. masses of long unmelted snow or of mulch, the less the disease appears. This lessening of the disease will take place also if the temper- ature of the air and the intensity of the sunlight are decreased as, for ex- ample, by a very cloudy sky, by a position on northern slopes, or under the protection of larger trees, high grasses or bushes, or by the artificial screening of the seed beds during the day. That older plants suffer less often from leaf casting is explained, in the first place, by the more strongly developed wood which in all plants may be considered as a water reservoir; in the second place, by a more abundantly developed, deeper reaching root system, which possesses more organs for absorption in its greater number of fibrous roots. Holzner' has raised an objection to this theory. In leaf casting, dis- coloration appears within 2 to 3 days, while, in an actual process of drying, the pine needles redden only gradually. He considers the cause a direct effect of frost. It is a well established fact that frost will also cause leaf casting. Baudisch* protected seedlings by a brush covering one meter deep above the surface of the soil. The plants which had remained healthy until the protection had been removed then suffered from the April frosts. Many authors ascribe an injurious influence to autumn frosts*. -The theory most generally accepted at present considers the disease to be para- sitic and, accordingly, recommends that it be treated with fungicides. Ac- cording to v. Tubeuf’s*t experiments, it cannot be doubted that there are also cases of parasitic leaf casting’. However, the fact must be taken into consideration, that the fungi of leaf casting are present in abundance on older pines, firs, spruces and larches, without calling forth the specific phenomena. Therefore, unless some conditions especially favorable for the much dreaded juvenile disease are present, it cannot become epidemic. 1 Holzner, Georg. Die Beobachtungen iiber die Schiitte der Kiefer oder Fohre und die Winterfairbune immergriiner Gewichse. Freising, 1877. Here bibliography of 145 studies on leaf casting. 2 Centralbl. f. d. ges. Forstwesen VII, 1881, p. 362. 3 Alers in Centralbl. f. d. ges. Forstw. 1878, p. 132. N6rdlinger ibid p. 389. Dammes and others, Jahrbuch d. schles. Forstvereins 1878, p. 40 ff. 4 v. Tubeuf, Studien tiber die Schiittekrankheit der Kiefer. Arb. d. Biolog. Abt. am Kais. Gesundheitsamt. Part II, 1901. 5 Ci aviol. I, sp: 268° 351 All these statements as to the factors causing leaf casting agree in maintaining that the needles fall because they have become weakened functionally or still are normally weak as a result of the winter’s rest.. Moreover, the abscission process depends upon the development of the cleav- age layer which presupposes living activity and an increased turgor. Thus, there arises an antagonism; the leaf organ is not at the time in a condition to function as a normal center of attraction and consumption. Because of its anatomical structure the basal part above the region of the subsequent cleavage can be excited and it is prematurely brought to the development of this cleavage layer by the increase in turgor, which arises in the spring due to exposure to the sun, or has been retained from the previous year, and finds no equalizaion since even the inactive lamina of the leaf do not take up the water from it. This disturbance in the equilibrium of the turgor distribution is the cause of all premature dropping of the leaves. In the special case of the pine leaf casting I think that the contrasts described by Ebermayer and, indeed, the sharp contrasts, represent the most frequent cause of the disease. Only in explaining it, I differ from him in so far that I accept as cause the winter’s inactivity, evident also in the constitution of the chloroplasts, instead of the excessively increased evap- oration from the needles. Only the base of the needle is excited and de- velops the cleavage layer, which, as will be mentioned under petals, can, under certain circumstances, be produced in an extremely short time. I am of the opinion that the needle does not become dried out, but is put out of action by the cleavage layer. I would like to assume from the absolute scanty elimination of water by pines in winter, that a drying of the needles resulting from an excessively increased evaporation, is not the cause of the discoloration and falling of the needles. An’experiment in a water culture of one year old seedlings showed me that a pine ceased its evaporation on the 17th of November despite following days with temperatures of + 3, 4, 7, 9g degrees C. Up to the 22nd of December they did not evaporate one gram more of water, although the root stood in water’. It can, therefore, scarcely be assumed that the spring temperature can, in a few days, cause a great loss of moisture, more particularly as the pine is a tree species which evap- orates the least of all’. Since the drying of the needles does not seem to me to be the cause of leaf casting, but rather a lack of equallization in the water supply, resulting from the sharp contrast between the needle surface, weakly assimilative, and its base, already active, I would like to believe the best preventative method to be the avoidance of such sharp contrasts: I, therefore, add the proposals made by Ebermayer :— A. Increase in soil temperature: (1) due to the prevention of too great cooling during the winter by means of leaf, brush or moss coverings; (2) 1 Sorauer, Studien tiber Verdunstung. Forschungen auf d. Gebiete der Agri- kulturphysik, Vol. III, Parts 4,& 5, p. 10. 2 vy. Hohnel; loc. cit. Vol. Il, p. 411, 352 by draining wet soils; (3) by loosening and mixing heavy soils with earths rich in humus, so that the warmth of the air can penetrate more easily. B. Lessening of sharp contrasts by shading: (1) by brushing the seed beds with evergreen boughs, which should not be removed on warm days; (2) by making the seed beds in places which are protected on the south by tracts of trees. “Tn the restoration of pine woods, on the whole, the most radical means consists in a return from the extensive clearing system to a plan of seeding, such that the young plants have the necessary protection from the direct sunlight in the overhead wood protection, but can still obtain as much light as is necessary for their vigorous development. The same end is attained by a slender fringe of trees running from N. E. to S. W., which are much used at present in the restoration of the pine tracts. In the cultivation of extensive clearings the shading can be obtained by a shelter growth of such plants as are favored by the habitat,—for example, by birches, etc., or by previous spruce plantations.” “In cases, where no shelter growth can be arranged because of local conditions, the planting of seedlings is preferable (yearling plants with a good root system seem best suited for this), yet the first two cultural methods will much more surely attain the desired goal.” Finally it is well to emphasize that every attention should be given to obtaining a good root system ;—accordingly, too thick seeding, heavy, un- broken soil, considerable injury in transplanting and the like are to be avoided. A leaf casting occurs also in older trees. The older needle bunches of plants standing on moor-soils in misty depressions, or found in localities subject to extreme frost, fall prematurely. But, in the autumn, these hang to the trees, turning yellow or drying up, and are thus distinguished from the seedlings specifically diseased with leaf casting. On heavy soils the pine always dies easily’. LEAF-FALL IN HousE PLANTS. Among the most delicate of the house plants belong the azaleas, be- cause, as a rule, they suddenly drop their leaves in summer or in the autumn; the broom-like little tree then at best develops only a few pitiful flowers. Here too are concerned sharp contrasts occurring suddenly. Either the plants (usually set in moor soil) in summer are left too dry, and later watered very abundantly, or they are brought too suddenly into the warm house in the autumn. In both cases, the leaves are weak functionally and then their functioning is increasingly stimulated by the increased upward pressure of the water. If the transition is brought about gradually, the inac- tive leaf surfaces would have time to resume their normal action by a general slow increase in their turgidity and there would be no resultant injury. 1 Runnebaum, A.. Das Absterben und die Bewirtschaftung der Kiefer im Stan- senholzalter usw. Zeitschr. f. Forst- u. Jagdwesen, 1892, p. 43. S58) But, with the sudden upward pressure of the water, the basal region alone is stimulated, thus causing the development of the cleavage layer. In foliage Begonias, rubber plants, camelias and many others, the leaves begin to drop in the autumn and winter. Here, the leaf is in a natural, dormant state. Abundant watering in a warm room causes an up- ward current of water which the leaves cannot utilize. Here are briefly a few of my own observations. A Begonia fuchsioi- des which had been forced through the winter in a warmer room, was brought at the end of March into an unheated, but sunny room. Within a few days it dropped all its leaves except the youngest ones. Libonia floribunda, which had been kept very cold, was suddenly brought into a greenhouse in December for forcing. The plants dropped all the older leaves, while plants remaining in the cold retained theirs. Some specimens of a double white fuchsia were brought into the house in the autumn in order to get early shoots for cuttings. Other specimens of the same variety were left in the cellar until the beginning of March. At this time the tips of all the plants were set as cuttings in a bench with 25 degrees C. soil heat. After a few days the cuttings, from the plants in the cellar, lost their leaves up to the very tips, while the others had not even lost the leaf at the cut surface. The tips of one branch, taken a few days later from a cellar plant, were placed in sand in the cellar, without any especial care and were found in May to have rooted, while the tips from the cellar plants had gone to pieces in the warm Case. For house plants it may be recommended as a fundamental principle that the plants should be subjected gradually to other vegetative conditions, and the dormant period, upon which every vegetative plant enters, should not be interrupted by an increase in the supply of heat and moisture. THE DROPPING OF THE FLOWERING ORGANS. This process takes place in the same way as that of the leaves’. The composite axes of the inflorescences in Aesculus and Pavia are known to separate into their individual parts, which loosen from one another with smooth cleavage surfaces. In the same way, if many fruits are set, a num- ber of half-grown ones are often abscissed to a joint in the fruit stem. The staminate blossoms of the Cucurbitaceae are abscissed at the cleavage layer formed on the boundary between pedicel and blossom, those of Ricinus communis in a line of separation, produced at a joint lying in the lower part of the peduncle. The hermaphrodite blossoms of Hemerocallis fulva and H. flava, left unfertilized, are abscissed by a cleavage layer ex- tending under the base of the blossom through the upper part of the ped- uncle. The cells of the cleavage surface round up and separate from one another. ane v. Mohl, H., Uber den Ablésungsprozess saftiger Pflanzenorgane Bot. Zeit. 1860, p. 5 354 In the same way a fully developed cleavage layer is found in the sepals of Papaver somniferum, Liriodendron tulipifera, at the time they fall; in the falling parts of the calyx of Mirabilis Jalapa, Datura Stramonium, in the petals of Rosa canina, Papaver; in the single corolla of Lonicera Capri- folium, Rhododendron ponticum, Datura Stramonium; in the stamens of Lilium bulbiferum and L. Martagon, Dictamnus Fraxinella, Liriodendron ; in the stigma of Lonicera Caprifolium, Mirabilis Jalapa and Lilium Martagon. In the majority of cases, the cells of the abscission layer contain no- starch, or at least no more than does the surrounding tissue, while, in the leaves and thick sepals and petals of Liriodendron abundant starch is pres- ent. This lack of reserve nutriment is explained by the rapid formation of the cleavage layer in the blossoms, for which the momentarily transportable nutritive substance is sufficient. In the sepals of Papaver somniferum the cleavage layer is produced in a single night, in the petals of single roses, in the hours of an afternoon. While cell increase seems to occur in the cleavage layer of leaves, it can hardly take place in the petals. The pro- cesses there visible consist only of a more abundant protoplasm, an in- creased porosity and mutual separation, due to a rounding up of the cells, and, at times, a pouch-like enlargement of the cells, whereby the cleavage layer looks velvety. The appearance of the cleavage layer is delayed as the organs are better nourished. THE SHELLING OF THE GRAPE BLOSSOM. By the term “shelling” or “falling” the winegrower means the dropping of blossoms soon after blooming. In some regions the phenomenon returns annually while, in other localities, it appears only in isolated years, as, for example, in those when wet, cold weather destroys the blossoms. Accord- ing to Muller-Thurgau’s' investigations, with a low temperature at the time of blossoming, the cells of the stigmas were beginning to turn brown even before the blossom sheaths fell, which indicated death or at least an extensive retarding of the process of pollination. Actually, on such stigmas the pollen grains did not develop pollen tubes at all, or only poorly. The dropping of the petal cap took place very slowly or was en- tirely suppressed. The ovule cases of such blossoms remained for some time, often actually for a long time, but they scarcely enlarged at all. How- ever, since, according to Muller’s discoveries, ringing of the vines is usually beneficial, the low temperature cannot be the direct cause of the incompleted act of pollination and the failure to mature the seed. The dull, cool weather during blossoming is especially favorable for the growth of leafy shoots, which, on this account, require the material stored up for the development of the inflorescence, so that the nutrition is not sufficient for the blossoms. Such a starving of the blossom cluster and, consequently, a more or less 1 Miiller-Thurgau, Uber das Abfallen der Rebenbliiten und die Entstehung kernloser Traubenbeeren. Der Weinbau, 1883, No. 22, SOs extensive shelling of the blossoms will occur also with weather favorable for blooming, if abundant nitrogen is present in the soil, or if virgin soil with an abundant supply of nutrients and water is used for the cultivation of grapes, when the luxuriant development of the vegetative organs limits the further development of the sexual apparatus. In fact, Muller gives examples of such cases and, at the same time, states his experience, viz., that sometimes fertilization has helped over- come the evil, and sometimes a long incision in the vine accomplishes the same end. Miller also ascribes to the same causes the appearance of seedless grapes on the bunch, which, as a rule, is correlative with a partial shelling. The seedless grapes are larger than the unpollinated seeded ones which, at times, remain on the bunch even until autumn. The seedless ones, however, are not as large as normal, seed bearing grapes, although, like them, they color and become sweet. Indeed, it is evident that they ripen earlier and become sweeter than the grapes with matured seeds. Since the seed primordia in the seedless grapes do not seem much larger than at the time of blossoming, it must be assumed that some dis- turbance had taken place at that time. It is probable that, in such cases, pollinization had taken place, but that either a temporary lack of suit- able nutritive substances, or some other disturbance, prevented the further development of the egg cell. The stimulus, exercised by pollination on the walls of the ovule cases is present and the grape consequently develops. Since, however, it does not need to use up any of the nutritive substances flowing towards it in maturing the seeds, this grape at first exceeds develop- mentally the grapes containing seeds. Weighing seedless and seeded grapes proves that the seed, in maturing, functions as a centre of attraction for material. Muller-Thurgau' found that the weight of the fruit flesh of 100 berries of Riesling was Seedless With 1 Seed With 2 Seeds Normal, with 4 Seeds 25.0 g 50.2 ¢ Tpi2ne Ae As examples of the differences in the material development, the results of an experiment by Muller with Riesling may be cited here. 1000 berries on the 25th of September showed Sccmlessam ) appear in the bark. The circumvallation edges extend over the bark as a knob with a lip- like cleft. This appearance is retained because of the natural swellings which are met with at times in the branches from cankered trunks of apple, beech, ash and cherry trees, and which I consider to be the initial stages of the closed canker swelling (cf. Fig. 135 in the ‘following section ). 586 CANKER (CARCINOMA). As “canker,” I consider those wounds which develop their overgrowth edges into excessive wood swellings. The character of the exerescence lies in the exclusive, or predominant formation of parenchyma wood instead of the normal prosenchymatous wood elements. The canker excrescences have a typical form for each tree variety. ; Fig. 132. Overgrowing frost split in apple branch, produced by artificial cold. a. CANKER OF THE APPLE TREE. The canker of the apple tree occurs in two forms, of which the more common one is distinguished by a broad, central exposed wood surface formed from the open, protruding, blackened wood body and is surrounded by roll-like, strong calluses, developing outwardly each year like terraces. At the centre of the wound is found frequently the remainder of a small stump of a branch. This is indicated in Fig.. 133 by 2, while the nearest overgrowth edge is indicated by uw’. We see how the wound surface gradu- ally increases since the first formed, still rather flat edge dies and turns 587 black, while that of the next year (w”) develops in the form of terraces. The process is repeated from year to year (see u”’-w"”) until nearly the whole extent of the axis has been attacked by the canker excrescence and dies. Such places, with open wounded surfaces which become wider and wider, are called “open canker.”’ The increase in thickness of the overgrowth edges toward the outside is explained by the fact that plastic material, coming from above, from still living, leaved twigs, has to be divided in each successive year over a smaller part of the twig or trunk surface because of the retrogression of the over- growth edges and accordingly provides relatively more abundant food [ "I taney | Fig. 133. Open apple canker. Fig. 134. Closed apple canker. substances for the formation of new parts, in the cambial zone, which is growing shorter and shorter. The closed canker (Fig. 134) when completely developed, represents approximately a spherical wood excrescence (wv) at times exceeding the diameter 3 or 4 times, knotted and usually completely covered with bark. This wood excrescence is flattened at its tip and deepened in the centre of the upper surface like a funnel (ft). In contrast to open canker, this swell- ing covers a much smaller part of the axis bearing it but makes up for its lesser extent in width by a considerably greater radial elevation, 1. e., greater height. 588 Blight may often be proved also on the branches and twigs on which occur canker excrescences. In all three varieties of injury a bright red to brown, flat conical, or oval fruit body of Nectria ditissima may be found, not infrequently, in winter on the dead, cracked edges of the wound. If a cross-section is made through the excrescence of a closed canker, approximately the following picture is found. We see (Fig. 135) the whole large swelling divided radially into two groups by the split (sp) with its roll-like edges. This cleft forms the inner continuation of the outwardly recognizable funnel-like depression on the flattened top of the canker excrescence (Figs. 134, 135 t). At the bottom Fig, 135. Cross-section through an apple branch with a knct of “closed canker.” of the cleft usually lies a brown, mealy, or putty-like mass which is found to consist of humified cell remnants. The edges (7) of the cleft are also strongly browned. They are formed by thick-walled, parenchymatous-like porous cells, provided with a dead, brown content. The further back one goes from the edges of the cleft, or the point of dying, toward the healthy tissue of the trunk, the less noticeable is the brown color. The tissue be- comes white and is formed of parenchymatous wood which contains an unusual amount of starch. Groups of strongly refractive cells gradually appear in these masses of parenchyma wood. They are clearly elongated, thick-walled wood cells which, isolated at times, or in small groups, appear irregularly distributed in the parenchymatous wood. (Fig. 135 4). Com- 589 pare the cross-section given in Fig. 132, due to an artificially produced frost split on the branch of an apple tree. Parallel with the appearance of the first wood cells is that of the hard bast cells (Fig. 132 4 6) in the bark. These prosenchymatous elements in the edge of the wound, formed of parenchymatous wood, are the initial stages of the normal annual ring for- mation and extend from the edge of the wound backward, approaching one another more and more closely, until they have united in a normal annual ring on the healthy side. If we start with the normal annual ring zone on the healthy side of the trunk, we may thus conceive this formation as follows; it is as if the prosenchymatous tissue of a healthy annual ring (Fig. 135 c h) had been divided into several radiating branches (Fig. 135 4) within the canker excrescence which chiefly consists of parenchyma wood, rich in starch and containing here and there large crystals of calc1um oxalate. (Radial division of the annual ring.) The edges of the wound, themselves, are not found united; the cleft, therefore, in spite of its narrowness, has never completely coalesced since the outermost cells, edging the cleft, constantly die. In proportion to the uncommonly luxuriant new formation, the number of dying cells in “closed canker” is very small. The dead place here always forms only a narrow twisted cleft; while in “open canker” the originally dead tissue represents a broad surface and the dying back of the edges of the wound extends so far that not only the wood surface which first remains uncovered, but also each overgrowth edge is incompletely covered by the succeeding one. The characteristic radial division, or splitting of an annual ring (Fig. 135 nh, h) within the woody, parenchymatous edges of the excrescence is less conspicuous in open canker and may completely disappear in case the entire trunk, which has remained healthy, participates, at the height of the canker-wound, in the exorbitant thickening, i. e., excludes a one-sided hy- pertrophy of the trunk. The determination of the dry substances in normal and cankerous wood in the cherry gives a proof of the softness of the tissue in the canker excrescence. Normal wood has 66.9 per cent. of dry substances; the overlying canker wood, only 45.1 per cent. From the fact that the canker excrescence frequently exceeds consid- erably the thickness of the two or three year old branch which bears it, we may conclude that the excrescence which is never found on the green shoot of the current year, i. e., begins only in the woody twig, must grow very rapidly. With such rapid development of the tissue, it is not surprising that the fluctuations between cloudy, wet weather and periods of drought can so manifest themselves that, within one summer, alternate zones of thin-walled and thick-walled wood are produced in the canker excrescence. This is found if the darker zone, extending from the pith (m) in Fig. 135, is traced further. It corresponds to the thick-walled wood elements and, in the normal part of the trunk, indicates the autumn wood in contrast to Bee the more abundant spring wood but always within the canker excrescence prosenchyma wood in contrast to parenchyma wood. The _ illustration shows the last formed, dark rings in the healthy part divided radially toward the diseased part. wu indicates a diagonally cut, dead branch. Bape ¥E 5 ee a _ ig. 136. Juvenile condition canker. of apple This luxuriance of growth, which manifests itself by the formation of the radiating canker excrescence, may not, however, lead universally to the conclusion that the growth of the tree as a whole is always luxuriant. On the contrary, a regular occur- rence of canker knots is found in weak, slender trees in certain localities. Cankered and also blighted trees usually show a very luxuri- ant lichen growth. At the central place of attachment. of ‘such lichen cushions it may often be proved that the cork lavers of the branch have been separated and the thallus cords shoved in be- tween them. In fact I could observe cases in which the lichen thallus penetrated the whole pro- tective cork layer of the branch and reached the collenchymatous bark cells, some of which. still contained chlorophyll. The lichen growth may, therefore, not be as injurious as the yellow and green forms are generally declared to be. How much, however, the spread of the lichen depends upon some individual peculiarity of the tree is still unknown to us (prob- ably a greater tenderness, poros- ity and torn condition of the bark), as is explained by an obser- vation on grafted older trunks of Fraxinus. The stock, possibly one to one and a half meters tall, appeared only scantily covered with lichens while the grafted scion, which at times bore a 12 to 15 year old crown, was closely covered by lichen growth. As a rule, cankered places on old ash trees, standing on wet ground, are covered with lichen. 591 In regard to the juvenile condition of cankered places, I mentioned under Frost Tears that I considered such small tears to be the initial stages of the canker excrescences. In the adjacent picture I give an illustration of two branches in natural size, as I found them on an apple tree, suffering from canker. In Fig. 136 a 1s shown an oval depressed part of the bark near a bud. The growth which took place after the injury has so in- creased the tension at the dead spot that the dry bark at its centre has split. At b we see a somewhat further advanced stage. The dead bark in the middle of the wound has already been raised by the overgrowth edges, ap- pearing at the side and united with one another. The places indicated at c and c’ in Fig. 136 show conspicuous, protruding knots, with a uniform new bark covering. At yr are the dried scaley, somewhat distended edges of the primary bark of the branch, which has been ruptured by frost. In this, the places are not near a bud; c is in the middle of an internode and c’ on the side opposite the bud. In Fig. 136 d the wound has attacked the tissue surrounding a bud. The bud is dead and the region depressed. The wound surface is here very great, the bark r’, under which air has penetrated, is still connected with its healthy surroundings and that newly pro- duced on the edge of the dead spot has caused a widening of the branch, as is very frequent in blight wounds. ~ Reproductions of open canker of the apple tree. as well as closed canker, show that the region of the trunk, bearing buds or young sprouts, is preferred in the formation of canker. Such a preference of the region below a short twig is shown in the adjacent figure of a small pear branch (Fig. 137). Directly : = Fig. 1387. Preference underneath the short twig at a we find a deep, already show ules: AE a overgrown frost tear. At b, the region of the short- the hase,ef ihe Z branch. ened branch ring with its short internodes and many weak buds, the bark has been split by many small tears and dried like scales. The young, upper part (c) of the branch has remained healthy. In such bark splits frequently the strongest overgrowth edges are found which often represent a single enclosed knot covered with uniform bark, but having often two lip-like excrescences touching one another and usually running longi- tudinally. Such wound edges at times appear folded toward the twisted central cleft, the original bark tear, from there falling away; they then resemble the canker wounds. The bark tears do not always represent longitudinal clefts and, accordingly, the overgrowth does not always occur in the form of two protruding lips but rather as knotty, spherical elevations with a crater-like central depression. On a branch g mm. thick, | found canker knots 13 mm, high and 35 to 45 mm. broad. Other branches, just as 5) thick and two years old, at times showed only very weakly callused, uni- formly closed protuberances, covered with new bark, which break out from the cleft in the old bark. The studies here cited determine that each canker spot has, as its initial stage, a wound which extends as a narrow radial tear into the ¢am- bium and kills it slightly back from both sides. This wound must be produced shortly before, or at the time when the trunk of the tree develops the greatest growth activity, since the wound surface will attempt at once to form a covering by means of very luxuriant overgrowth edges. The luxuriance of these overgrowth rolls manifests itself in the fact that, especially in the closed form of canker, a partition of the annual ring usually occurs, the edges of which chiefly consist of parenchyma wood. The edges of the wound are very susceptible because of this porous struc- ture, so that they succumb with ease to injurious attacks. We must consider frost as the cause of these forms of disease because it has been possible to produce, by the action of artificial frost, the same initial stages as are found in canker wounds. However, a number of very reliable observers have determined that it is possible by the injection of a (capsule) fungus, Nectria ditissima’, to produce wounds, the forms of which resemble perfectly those of the open canker of the apple. I can confirm these statements by my own experi- ments. One has indeed a right to speak of a fungous canker but the above named parasite is not able to attack an uninjured axis. It can spread de- structively only if it gets into a bark wound. AJl inoculation experiments agree in this. On the other hand, the same Nectria is found in apple trees, beeches and other varieties of deciduous trees without causing any canker excrescences whatever. Therefore, it cannot be termed the specific incitor of canker excrescences but will give rise to these only occasionally when very definite secondary conditions co-operate simultaneously. Besides the presence of a fresh wound surface, it depends also upon the specific pecu- liarity of the tree, i. e., the cultural variety, which must possess the ability to respond to the wound stimulus with quickly developing, very luxuriant overgrowth. This ability is so typical that in general practice one speaks of “Varieties with a canker tendency.” Besides this, experience has shown that the tree easily becomes cankered in certain places and kinds of soil. These are the so-called frost holes, having a marshy soil consistency, an impervious sub-soil, ete. These are well-established facts. I{ we now keep in view the fact that Nectria ditissima must have some wound for infection, we must ask whence came these wounds. From observations made in nature and from the results of experiments with artificial frost, we are convinced of neces- sity that frost injuries are the most easily accessible. Paparozzi holds to 1 See literature in the second volume of this manual, p. 209. 593 the same standpoint for the canker of pear trees'. If the frost wounds are flat surfaces such as will be found later under “Blight,” the Nectria will infest the tree without its formation of luxuriant overgrowth edges. If, however, narrow frost tears, extending into the cambium, are produced into which the Nectria find entrance, the tree responds with the formation of canker excrescences in case climate, habitat or specific characteristics make it capable of so doing. Accordingly, the fungous canker also appears to be essentially depend- ent upon frost injury and its combatting or avoidance will have to be carried on with due consideration of the danger from frost. b. CROTCH CANKER IN FRUIT AND ForREST TREES. “Crotch canker,’ which is of frequent occurrence in forest and fruit trees, should be mentioned as an especial form. It consists of frost wounds found at the bases of the branches, or twigs, which belong to the group of open cankers and are formed from black, dead surfaces differing in size with luxuriant, irregular overgrowth edges. The angle where the branch joins the main trunk is separately attacked in many varieties. In the so-called “bifurcations,” or forkings, where the difference between the main and the lateral branch disappears so that two equally strong branches grow out from one point, the ex- posed and blackened place in the wood is usually elevated at both sides and, accordingly, the over- growth edge is formed from the material of both branches -(cf. Fig. 138). Aside from the more sensitive, imported trees, our indigenous forest » trees, according to Nordlinger?, are also exposed to % injuries at the crotch, especially when young; thus, Fis. 188. Crotch canker. ior example, beeches in shady positions and on poor soil, in which the internodes at some distance from the crotches are also often covered with frosted surfaces. The annual growth of the oak also suffers on poor soils and the ash is found to be injured if the tree stands in depressions with a heavy clay soil. In such damp places I found the over- growth unusually luxuriant but so covered with thick, split bark, overgrown with lichens, that it had become irrecognizable. Opposed to the theory, which Hartig represents, that crotch canker is conditioned by spring frosts, Nordlinger thinks the cause is frost at the beginning of winter. He bases his opinion on the investigation of the wood ring and on the fact that, in thousands of cases, crotch canker is very 1 Paparozzi. G., Il cancro del pero. Roma, Offizina poligrafica; cit. Bot. Cen- tralbl. 1904, v. XXVIII, p. 94. 2 Die Septemberfréste 1877 und der Astwurzelschaden (Astwurzelkrebs) an Baumen. Centralbl. f, das ges. Forstwesen. Wien 1878, Part 10. 594 abundant high up in the crown and in shady places, i. e., those less exposed to spring frosts. The especial susceptibility to frost of the base of the branch is ex- plained by the fact that, on account of the greater number of buds originally set there, more parenchymatous medullary bridges are present, which traverse the wood ring. The parenchymatous wood is more tender and contains more starch. To this should also be ascribed the fact that bark beetles like to settle in the crotches and that wood mice, as Nordlinger states, frequently eat only the base of the lateral branches in poplar suckers (Populus monilifera). Therefore the frost, i. e., the spring frost, kills the base of the branch most easily. In old, weakly growing trunks, the luxuriance of the overgrowth edges decreases considerably and can become so slight that only narrow, circular overgrowth edges are present, which push out slowly from under the dead bark. This blight corresponds to that of the crotch injury, since in open canker, the first stage is not a cleft but a collapsing, drying dead bark surface. Hence, the expression “crotch blight’ frequently used by many practical workers. c. CANKER ON CHERRY TREES. In sweet cherries are usually found semi-cylindrical protuberances on the twigs, or older branches. The outside of these swellings, often thicker than one’s fist, not infrequently seem depressed, as in blight; the dead bark is split and partially stripped from the blackened wood body, still remaining attached as larger scales with up-rolled edges (cf. Fig. 139). The barrel-shaped swelling on the branch represents an abnormal de- velopment of the overgrowth edges (u and u’) of the wound (sp) which does not close entirely, as is also found in the “closed canker of the apple.” In the latter, however, the overgrowth tissue is a sudden, unusually lux- uriant widening of the annual ring, while, in the cherry, the swelling of the normal side of the twig shows a gradual transition to the excrescent over- growth edge. On this account, the closed canker of the apple has the form of knots but the completely developed canker of the cherry a gradually increasing barrel-shaped thickening. Besides this typical form, various transitions are found from the closed canker knots, on the one hand, to the flat wound, on the other, which is termed blight. Conical swellings are found at the base of older branches of trees, suffering from canker, which can offer all the transitional forms up to the typical canker swelling. The initial stages are found on one side of the branch in the form of a small frost wound alongside the first annual ring. An especial emphasis should be laid here on the fact that the enormous overgrowth tissue seems often to be developed from a medullary bridge. This, therefore, points to some direct injury to the bud. The development of the overgrowth edges is continued in subsequent years, when only paren- 595 chyma wood is formed in which starch is rapidly and abundantly deposited. If the canker swelling has become considerably extensive, the branch dies, as a rule, above this swelling; in this, stroma-forming fungi (usually from the family of the Valseae) greatly co-operate. They appear in the form of small warts. If the young branches (1 to 2 years old) of trees suffering from canker are examined, blight-like places, often several centimeters long, are found, with lip-like overgrowths instead of individual buds, while, on the parts of the branch above and below these places, the buds have developed to short shoots. It is evident from this that the injury to the branch must take place before the breaking of the bud. Since, however, no injury of any kind can be ascertained in the year in which the branch is formed, but will be found only in the following spring, it must have arisen in the winter or at the beginning of spring; the as- sumption is, therefore, pertinent that the bud, as it unfolds in sprouting, is killed by the frost and that the accu- mulated plastic material is now used in the formation of the excrescent edges of the wound. Since the tissue of these overgrowth edges remains as soft as the parenchyma and is almost always found filled with starch, it is clear that, in the following winter, its edges succumb very easily to injury from frost and new excrescences are produced from the deeper lying zones which remain healthy. A consider- * J ation of the cross-section in Fig. 139 Fig. 139. Cherry canker frost cleft makes clear tuewhole:processo This» 1"1'" overetowth edees my tone tudinal shows that the clefting of the axis has begun at a short distance from the pith body (m) and in the second ainual ring. The third annual ring has already furnished luxuriant overgrowth edges (f) which, in turn, split the following year (sp’). These secondary clefts cause secondary overgrowth (f’). The barre!-shaped canker swelling, however, is formed chiefly by the ex- crescent wound edges of the main cleft, which are radiatingly arranged (k). ‘thus an annual ring inside the canker swelling is divided into several rings, as in the closed canker of the apple. The bark body 596 (r) also forms corresponding excrescences and, in places, develops thick bark scales. In the canker of the cherry, as in all canker diseases, only scattered individuals are found diseased in large plantations. I often found in the Fig. 140. Canker excrescences in the grapevine. healthy shoots of these cankered examples abnormally broadened medullary rays, a phe- nomenon which may be observed also in other kinds of trees. I, therefore, surmise that the inclination to become diseased with canker may be found in the individual ten- dency toward a widening of the medullary rays. THE CANKER (SCAB) OF THE GRAPEVINE. In the older wood of grapevines near the surface of the soil, about Io to 50 cm. above it, are found scattered, small spherical or large barrel-shaped, out-pushings of the wood from the bark, with a beady, irregular upper surface, split lengthwise into fibres. Fig. 140 shows a beady canker swelling between the strips of bark which are drawn in white. In small, isolated outgrowths, their production, according to Gothe’s* investiga- tions, is clearly recognizable as the over- growth tissue of longitudinal clefts. The clefts appear at the edge of the annual ring, from which it must be concluded that they were produced at the time when the de- velopment of the next annual ring began. caused by the dying back in spots in the cambial zone in the spring. In regard to the production of the excrescences, I have stated some differing observations of my own, under the head of the disease to be treated next,—Canker of the Spirea. The injury, which killed the cambium, has also caused a considerable circular sur- face on the old wood to turn a deep brown. The overgrowth beginning at the healthy place, which often quickly closes the cleft, is characterized by an excrescent luxuriance of the wood and bark. The woody edges, curling out towards one another, consist of soft, ductless parenchyma wood, without any real 1 Mitteilungen iitber den schwarzen Brenner und den Grind der Reben. Berlin und Leipzig, H, Voigt, 1878, p. 28 ff, 597 prosenchymatous elements, i. e., they exhibit the characteristic structure of the excrescent wound wood. If the overgrowth edges have united into a connected annual ring, this grows further in such a way that it is sub- divided by medullary rays. The direction of these medullary rays continues that of the medullary rays of the wood formed the previous year. There- fore, this wood has undergone only a temporary interruption in the brown dead tissue. The changes and tissue excrescences described are never found in wood of the current year. Gothe thinks the bead-like appearance of the tissue excrescence, which, growing extensively radially, splits the old bark, is explained by a complete “overlapping, inward growth” of the overgrowth rolls, which are present most abundantly at places on the vine lying about 30 cm. above the surface of the soil. Examination shows that, starting at such places, the number and extent of these swellings decrease away from as well as towards the soil; close to it, and about one meter away from it, they occur very rarely. With a slight development of the disease, the attacked trunks may vegetate for several years and then still produce bearing wood. With a greater development of the canker swelling, the wood, lying above it, dies. The rapidity, with which the canker swelling is produced, is proved by the fact that, on August 8th, plants were found in which the grafting tape lay embedded 0.75 cm. in the tissue excrescences. Therefore, the entire canker swelling, 2.5 cm. thick, can only have been produced after the time of grafting (in May), for it can not be assumed that a scion would have been inserted in a diseased vine. Gothe has proved by the following experiment that the injuries to the cambial ring take place in the spring. In April, when the vines were pruned, 12 strong bearing vines were tapped, between two nodes, with a dull iron, in such a way that an injury to the cambial layer could be as- sumed. Glass tubes were then shoved over the injured places and the openings closed. The first traces of the swellings could be proved as early as June 8th, while on specifically scabby vines the tissue excrescences did not appear until June 20th. Up to autumn, perfectly normal scab struc- tures continued to form in the glass tubes, with also the same anatomical structure as naturally formed excrescence edges. Spring frost may be considered as the cause of these excrescences in nature. Most of the literature which proves the appearance of grape canker after spring frosts also favors this assumption’. It is also strength- ened by the discovery that grape canker occurs only in the so-called frost holes. Godthe cites in this connection, an example from a vineyard which began on a small slope, passed through a hollow and rose again on the opposite slope. On both slopes the plants were healthy, but in the hollow were found to have been attacked by the disease. In a subsequent test, the 1 G6the cites v. Babo, Weinbau, p. 305; Dornfeld, Weinbauschule, p. 129, Kohler, Der Weinstock und der Wein, p. 205; du Breuil, Les Vignobles, 598 observer found that the disease had occurred on 20 other vines, which stood in depressions in the soil. The fact that the grape canker appears at a definite height on the vine is explained by the various differences between the heat maximum and minimum to which the vines, at different heights, are often exposed at the time of spring frosts. Draining of the soil might prove the most effective method. Kohler has already announced favorable results in his above-mentioned works. sesides this, attention should be given to the planting of hardier varieties and especially the choice of suitable positions (moderately moist, porous and warm soil). It is not inconceivable that the scab, without the action of frost, may be produced by an accumulation of plastic materials, as Blankenhorn and Mithlhauser believe they have observed as the result of too severe cutting back’. It is certain that the beginnings of the swellings, occurring in the form of medullary ray excrescences, can appear in the vines in which in the spring the bark has been raised in places from the wood of the previous year. Such canker excrescences, as said above, can mature without any injury from frost, just as canker-like, excrescent overgrowth edges are found in luxuriantly growing pomaceous varieties. But in such cases, the deep, extensive browning of the wood body is lacking. c. CANKER ON SPIRAEA. A disease, not yet described, showing great relation to the canker ot the grape, attacks the bases of the stem of Spiraea opulifolia. The disease seems to occur more commonly only in regions with very cold winters. The material which I had for observation came from East Prussia. Other wood, at least two years old, with strong annual rings shows at the stem bases unusually abundant hemispherical swellings of the wood, scattered, or in rows like chains of beads, or in masses. (Fig. 141 A, k, kk). The size of these swellings varies from a few millimetres up to 1.5 to 2 cm. in diameter. The swellings are brown, darker than the outermost bark layers, which they rupture, and loosened in tatters. They are often cleft or depressed in the centre like a funnel and provided with thick granu- lated, torn surfaces. No single bark layer can be raised, since the tissue of the swelling is brittle and easily breaks off in pieces. In cutting away a considerable swelling, or, as one is justified in saying, canker knot, it is found that lamellae or firmer material radiate out from a more or less broad base. However, the lamellae neither extend through the whole thickness of the canker, nor are they separated sharply from the tinder-like, decayed, darker ground tissue. This itself is to be considered an excrescent continuation of the last annual ring, which becomes more and more delicate toward the periphery. 1 ef. Wiirzburger Weinbaukongress, XS ‘ ~ = Canker on Spiraea. Fig. 141. 600 In Fig. 141 B, which gives a cross-section of the canker knot (k) from lig. 141 A, m indicates the pith body; a, the uninjured annual ring of the first year’s growth; 0, the cleft ring of the second year; c, the wood of the third year, which is growing out into the canker swelling (fk) ; 7 represents the firmer tissue islands and stripes in the tinder-like ground tissue. In the cases which have been observed up to the present, the main part of the canker knot has seemed to be the production of a single year and, in fact, a one-sided woody excrescence over a place which, even in the pre- vious year, had formed a wedge-shaped zone of porous, parenchymatous wood tissue, its pointed end toward the interior. In so far two years are necessary for the completion of the canker knot. If the above mentioned, wedge-shaped zone is traced backward to the annual ring of the previous year, it will be seen that this originates in a brown, slender place in the first spring wood. The adjoining anatomical picture, Fig. 141 C, will facilitate the expla- nation, The whole figure C 1s a radial section of the second annual ring from a Spirea stem and contains the tissue zone which is preparing to develop into the real canker swelling. The line f to ff represents the strip of changed tissue, which in its further development in the following year, will have become a complete canker knot. The tissue shown at a is the autumn wood of the first annual ring. No disturbance has been observed in the wood body of this first annual ring, just, as in the canker of the grape, the first annual ring has a perfectly normal structure. The wood of the second annual ring (0D) at first began a normal development and continued it up to b’, At this time occurred some disturbance which produced the cleft (d), and browned its edges (c’). The time this split was produced must have been that of the greatest formation of new wood for, only a few cell rows farther, we find that the split is closed at h, and the annual ring has grown further with the formation of groups of normal parenchymatous elements (p). Only a single cell-row (&) forms a radial stripe, with shorter cells containing wider lumina. Now the abnormal wood stripe, instead of dis- appearing as the annual ring matures and increases in width, grows broader, since more and more cells take part in the changed form of construction (kk). Thus the disturbance advances until the second annual ring is fin- ished and then begins, to a renewed extent, in the spring zone of the third annual ring (c-c). Even when the second annual ring is finished, the stripes of the begin- nings of the canker may be seen to project as slight elevations above the periphery of the remaining wood ring. In the spring of the third year the new formation at this place is so luxuriant that the rapidly growing canker knot, strengthened by the equally rapidly excrescent part of the bark (k /), ruptures the normal bark (7) at sp and now grows further, as it were, as a foreign structure, in order, after some weeks, to end its growth, being a complete canker knot I to 2 cm. thick. 601 Similar formations are found in the canker of the grape. Only I have found as yet that the disturbance, setting in at the beginning of the second year, and corresponding to the holes (d), consists of a broader tangential elevation, circular in form. It give the impression that, at the beginning of the period of growth, the bark was raised from the wood body for a considerable distance. My repeated experiments with artificial frost show that this process can actually occur and, in fact, it is met with rather fre- quently in various trees. As a result of this lifting of the bark, a tangential hole is produced on the grapevine, usually at the place where, on Spirea, the slender, radial cleft is found. The raised bark forms, first of all, wood parenchyma and this soft wood body passes over very gradually, in the course of the following summer, into normal wood. Here, however, some of the broad medullary rays are found above the raised part which have developed especially and at the end of the year project as delicate tissue caps. In the grapevine, as in Spirea in canker formation, these are not neces- sarily overgrowth edges, as is always the case in the canker of the apple; in the former, tissue cushions of a wood body which has become parenchy- matous develop to canker knots. These cushions at first appear uninjured and are at any rate caused by some previous disturbance. This explains the theory expressed by Blankenhorn, on the canker of the grapevine, viz., that the stoppage of plastic materials (for example, with too strong prun- ing), can cause the canker excrescence. The formation of the canker excrescence often indicates some modi- fication, inasmuch as the canker cushions, produced in the first year, are partially killed by the frost. Then the central, most delicate part suffers and represents a black, dried core. In the following spring only the edges grow further, just as do overgrowth edges, and line the cleft, as is shown in Fig. 141 B. It has been said that the parts of the edges of the growing canker knot continue growing “after the manner” of overgrowth edges. Actual overgrowth edges, spirally curved, are found only rarely (as in the canker of the grape). Fig. 141 B shows that the wood ring of the third year passes over imperceptibly into the canker swellings. Therefore, the canker swelling is actually a wood formation but this wood, because of the enormous rapid- ity of the tissue formation, is a structure so soft and so similar to the likewise excrescent bark tissue, which is dying back from the outer side, that it is often difficult to determine the boundary between them. This porous wood, which I have found so very soft only in the canker of the rose, forms, on the dead swelling, the brown,, tinder-like ground mass, of which we spoke at the beginning. The firmer, lighter colored parts are the islands of thick-walled wood cells and ducts (Fig. 141 5, 7) increasing in breadth and thickness at the periphery. In canker knots of different sizes, the groups of ducts (7) are sometimes found in the form of wedge-like lamellae, becoming thicker toward the outside, sometimes (as in Fig. 1412 ) 602 in the form of spherical groups with a sheath-like arrangement of their elements. The groups not infrequently unite and in this way cause a greater firmness but no complete wood ring has ever been observed. It 1s these isolated parenchyma and duct groups which in pruning so greatly resist the knife, that they are torn loose from their connection with the other tissue before being cut through. Hence the easy crumbling of the canker knot. Fig. 142. Rose Canker. Concentric overgrowth edges may be recognized, rising like terraces around a central, dead wood surface. f. CANKER OF THE ROSE. In the culture of the newer climbing roses, which (according to Crépin-Briissel) have resulted from a crossing of Rosa Indica with RK. multiflora and are called Polyanthus varieties, we have become acquainted with a phenomenon which comes under the head of canker excrescences. The adjoining Fig. 142 A and B, represents such canker swellings as are 603 found at the base of the strong stems of Crimson Ramblers in Germany. Their appearance on the lower part of these rose stems, which, as is well known, grow most luxuriantly in Germany, reminds one of the same occur- rence in the canker of the grapevine. As in all forms of canker, we find here also that the region of the axis is preferred where branches (4, a) are produced and the base has strongly thickened or split open into curled excrescences (8, ub). As an explanation of this phenomenon, it need only be remembered that the wood ring is broken and especially susceptible to disturbances at that part of the normal axis where a branch starts. for the pith body is widened at the place of insertion of the twig into a pith bridge, transecting the wood ring and passing over into the lateral branch. In such a developing branch the eyes stand closest together at the base; they may often be but little developed, because the leaves are still bract-like or incomplete, but the parenchymatous medullary bridges, which traverse the wood ring, are present. The canker spot on the main axis in the present case, as in the “open canker of the apple,” shows a central wound surface with an exposed brown wood body (Fig. 142 4 and B, w). This surface is encircled by terrace-like, rounded overgrowth edges (i). These wound edges, however, do not retain their uniform wall-like character, as in the canker of the apple, but develop into irregularly knobbed, or beaded, heaped up tissue masses. In other cases, the canker of the rose occurs, like the canker knot in Spiraea, in boil-like, united and elongated wound edges, which line a long cleft, starting from the base of the branch. All excrescent tissues ultimately rupture the bark (7). An insight into the production of these excrescences, which are not exceeded in luxuriance by any other canker swelling, is obtained from the above reproduced cross-section of a rose stem, at the place where it has formed a small, isolated bead-like elevation (cf. Fig. 143). We perceive that the stem has developed normally in the first year; a normal wood ring (h) surrounds the pith body which has broad medullary rays (mst) and which ruptures later (v). In the second year, as the first cell rows (gr) of the new wood ring were in the midst of developing, some disturbance must have made itself felt in the form of some break in the tissue, for the new wood ring (Ap), for the most part, has taken on the character of the parenchyma wood and only in places (h’) has it retained the normal wood structure, characterized by the formation of ducts and thick-walled wood cells. The cause of this breaking up of the tissue has been a split in the bark, traces of which may be seen in the lip-like, small indentation at the upper side of the figure. The cork layers (k) of the bark, which cover this, have been split and the overgrowth tissue (zw) swelling out from both sides, which has been covered in turn with a cork mantel, has coalesced into a closed mass in the immediate proximity of the tear (which is not shown in the drawing). If this tissue is traced backward toward the healthy (upper) side of the branch, starting from the most luxuriant place of 604 excrescent tissue (zw), it is found that this gradually dwindles away and inside the bark begins to take on a normal character (fg.) Here the ar- rangement of the hard bast cords is still approximately normal but their structure has been changed greatly. The majority of the bast cells have a yellow, swollen content and easily browned walls. Nevertheless, they are distinguished, as strong, light-colored groups from the deep brown bark Fig. 143. First stages of the rese canker. parenchyma which is cut off from the outer collenchymatous bark layers by the subsequently produced layer of plate cork (k’). The drawing shows, however, that the ring of bast cells (b) is removed farther from the wood body the further it advances into the tissue of the excrescence. It is, therefore, pressed away from the wood body by the increase of this body. At the same time the bast ring is seen to have been PD 005 uo pushed back further from the outer collenchymatous layers. Therefore, cell increase must have taken place in the primary bark. The question should now be asked as to whether the tissue, which presses the bast ring away from the wood, is exclusively a product of the secondary bark or whether the wood cylinder itself has contributed to this. We find the answer in the tissue group (/p’) which represents the paren- chyma wood. We find such groups of parenchymatous wood within a soft, thin-walled tissue, when bark wounds are healed by the formation of new tissue from the youngest sapwood layers, remaining on the wood body. We learn further, by studying the false annual ring (cf. False Annual Rings) and the healing processes of inner frost tears, to recognize the formation of parenchyma wood from the broken sap wood layer. Also, in the pro- cesses of grafting and especially those of budding and bark grafting we find that cicatrization tissue has been formed from the youngest sap wood, if the actual cambial zone has been injured. If the cambium is retained in an injury but the bark mantle is broken by a tear in the bark, the cambium develops into a tissue, at first parenchymatous, which, at the edge, gradu- ally passes over into a normal wood structure, according to the amount in which the normal bark pressure is restored (cf. Wound Healing). The same new growth can also take place on the inner side of the bark if this is raised from the wood cylinder without an entire interruption of its nutrition. I have carried out the experiment with cherries in such a way that the still smooth bark of the young trunks was loosened in strips, connected at their upper ends with the uninjured bark mantel left on the axial cylinder. At the places where the upraised strips passed over into the uninjured bark, I found the same callus formed on the inside which later was differentiated into bark and wood. It has therefore been deter- mined experimentally that exposed wood can produce new bark and that upraised bark tatters can produce new wood when still attached at their upper end to the wood body. In this way, the process in rose canker becomes easily understandable. In the first spring, a tear appears in the bark which extends to the cell rows of the spring wood of the new annual ring already formed and results in the lateral raising of the bark from the cambium as shown in the holes (J). At first the constricting influence, which the cork girdle (&) usually exercises on bark and young wood, is wholly overcome because of this cleft, which results in a luxuriant increase of the young wood (on the under side of the figure) where the cambial zone has not been destroyed, and the lux- uriant increase of the parenchyma of the inner bark where this had been raised from the young wood (at / on the upper side of the figure). The new structures, whether formed from bark tatters, or young wood, are uniformly callus-like and pass over imperceptibly into one another. It is these new structures which have ruptured the previously continuous bast ring (b, b’), have pressed outward the most strongly injured part (b’) and caused its death after splitting it off from the outer bark. 606 The main question is, in what way can the first radial cleavage have taken place. And the only answer to this can be; as the result of frost. For we again find here the browning of the pith crown, the tearing and widening of the medullary rays, the phenomena of elevation and cleavage of the tissue which I have been able to produce experimentally by the action of artificial frost. Only, I have not been able to produce artificially the secondary phenomena, viz., the luxuriant tissue increase. This probably is based upon the fact that in using artificial frosts I have not yet found the proper juvenile developmental condition. This must be the time when the cam- bial activity has just begun, as is evident from the small number of cell layers just formed by the new annual ring. If the dis- turbances occur later, capacity for reaction in the tissue is less and the excrescent cell increase does not take place. Gothe’s ex- periments show how very deter- minative the time of injury is. As already mentioned, he pro- duced excrescences resembling the canker of the grape, by a continued tapping of the grape- vine in the early spring. The grape canker is closely related ontogenetically to the canker of the rose. g. CANKER OF THE BLACKBERRY. It is a noteworthy fact that, with the exception of grape canker, all the other canker ex- crescences are found in the family of the Rosaceae. In the canker of the blackberry, cauliflower-like, hard, glistening, white tissue masses with a beaded warty surface are produced on the older wood (cf. Fig. 144 &). These tissue masses sometimes form isolated spheres ; sometimes collect in Fig. 144. Canker of the wild blackberry. elongated, wart-like cushions, as in Spiraea. The region of the eye is the 607 preferred place of production. The bark is split and partially thrown back like wings. With an abundant appearance of the canker swellings, first of all, the foliage turns yellow, then the stem begins to die back slowly from the browned eyes. By July, as a rule, the diseased branches on the same shoot. side by side with bright, perfectly green ones, have died back entirely. If healthy plants are examined for such cankered stems, either small reddish, or brown, long ridges are found, or gaping tears often one centi- metre long. I observed the same phenomenon also on many petioles. The sloping edges of such tears are covered also with cork. On these edges, small beady excrescences appear in places which consist of parenchyma and are formed from the primary bark close to the outside of the hard bast cords, In the Rosaceae this tissue region proved to be extremely easily stimu- lated. I found that, after very different injuries to the bark, which gener- ally did not extend to the hard bast, strong branches responded to the wound stimulus by a parenchymatous increase close outside the hard bast cords. Often, in the canker of the blackberry, a place of predisposition for the formation of canker may be noticed, for, in the spots where a wart-like excrescence had appeared, even in young branch shoots, the mechanical rings formed from the hard bast cords and other thick-walled connective elements are proved to be unthickened. A thin-walled parenchyma had appeared instead of the prosenchymatous and sclerenchymatous tissues. The parenchymatous, excrescent tissue in the primary bark increases very rapidly and ruptures the overlying normal bark layers. In the interior of the canker wart, a porous wood body is formed which is rich in ducts. The formation of wood elements is repeated in the peripheral parenchyma layers of the excrescence zone first produced since meristematic aggrega- tions arise from which develop tracheal wood elements, arranged like bowls or shells. The beginning of canker in the blackberry therefore is a parenchy- matous excrescence in the primary bark body which grows outward, with a cauliflower-like ramification. Only later does the tendency to hyper- trophy extend backward into the inner bark, finally attacking also the wood ring which, at first, seems to have a normal structure. As soon as the swellings become older and the wood body participates in their formation, it increases to 3 or 4 times its normal size. We find similar processes in dropsy, in the formation of tuber-gnarl, etc. The canker is more rare in Rubus; as yet I have found it only in four cases and always in narrowly restricted places. CORRESPONDING FEATURES IN CANKER SWELLINGS. In a survey of all the known material relating to closed canker corre- sponding features are found. (‘Open canker” forms a transition to blight and is included here). The production of a small tear forms universally the beginning of the disease. It may be seen in all cases that the injury must 608 have taken place in the early spring and that the richly collected material enabled the parts surrounding the wound to form enormous excrescences most quickly. The parenchymatous character of the new structures causes a great sensitiveness to injurious atmospheric influences and especially to frost. Low temperatures, therefore, are able to injure the canker tissue in the next period of growth. The injured [ tissue complex can respond repeatedly with excrescent tissue, because, with its paren- chymatous nature in the previous period of growth, it has stored up very abundant re- serve substances in the form of starch. The canker forms in the individual genera of the Rosaceae differ only in the manner of reaction to the wound stimulus and agree in that they prefer the bud and its immediate surroundings as the place of production. The reason for this may be sought in the division of the trunk at the place of insertion of a bud. The wood ring is always more slender here and finally traversed by a parenchymatous pith bridge. The initial stages of the canker knot, So. far as, observed). e4. the smialisieare usually arising near the buds, have been produced by artificial frost, but not the luxuriant overgrowth structures. This cir- cumstance may possibly be traced back to the fact that a period in the spring had been chosen which was too late for the action of the artificial frosts. In the healthy branches of cankered trees an abnormally increased formation of the medullary rays has often been observed, and this may indicate the explanation of the tendency to canker excrescences of certain cultural varieties, or different indi- viduals in certain habitats, since those ex- RES Dal Feet amples will answer most easily to a wound Fig. 145. Frost spots on pear : Fg / bark, stimulus by hypertrophy, if their medul- lary, or rather bark rays, grow luxuriantly in a healthy condition. BLicGHT (SPHACELUS). In contrast to the term ‘‘canker’’ which in general practice is used for ihe heterogeneous phenomena of a gradually extending disease, one under- stands pretty generally by the term “Blight” the occurrence of dead, black- PART VIII. MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER In Collaboration with Prof. Dr. G. Lindau And Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural! History of Berlin in Hamburg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT Third Edition--Prof. Dr. Sorauer = a Copyrighted, 1917 FRANCES DORRANCE ert for « € LJ CP © eae e,e « ©v.a479859 o, * _" THE RECORD PRESS Wilkes-Barré, Pa. JAN -5 1918 iy na ‘ es 609 ish, extensive spots in the bark which have dried on the wood. In smooth barked trees, instead of large, connected blighted surfaces, numerous small depressed places in the bark are noticed, appearing often on one side of the tree. These resemble finger marks and are usually called frost plates. These injuries are abundant, or scarce, according to the susceptibility of the variety to frost and the conditions of the places of growth. In stone fruits, the phenomena of blight are found most frequently in cherries and plums; in the more sensitive peaches and apricots, the trunk usually suffers as a whole. In pomaceous fruits, pears undoubtedly tend most easily to injuries from blight. Of forest trees, the beech and oak count as especially sensi- tive and in damp places the ash and acacia also. The edible chestnut is found in central Germany only in isolated localities. Among conifers, the fir seems more sensitive to frost than the spruce. The larch suffers as soon as it lacks sufficient light and air. The linden and maple are rarely found to be injured. Blight spots are found most rarely in the older birch, elm, willow, poplar, hornbean, and especially the pine. The dying of the bark is to be considered as a direct effect of frost. It penetrates to different depths and can, accordingly, produce a different appearance in the different blight wounds. Thus, for example, frost fre- quently attacks only the youngest layers of the bark and sap wood, includ- ing the real cambium. The older, outer layers of the bark die only from lack of nourishment, since the bark, killed by frost, turns dark in a short time after thawing. We find in the spring (especially in pears) depressed, sharply outlined places, often only very small in extent and at first only on different sides of the trees, or branches. These places soon become dry and adhere to the wood (Fig. 145 p). They are the above-mentioned “frost plates” found by many fruit tree growers. A cleft appears at the boundary between the dried part of the bark and the healthy part, which is raised up by the growth in thickness of the trunk. The dead part of the bark is again cut off from its surroundings by this cleft and loses its ar- resting influence (Fig. 145 7). The arrestment, exerted by such a dead place, lies in the increased pressure of the bark mantel so long as this bark mantel is still connected with the dead, dry, inelastic tissue. The bark pressure will be greatest near the dead places and the number of newly formed elements the smallest. We find this at the beginning of the healing processes. The tree en- deavors to cover the dead places by the formation of overgrowth edges from the healthy parts of the bark. This can take place in two ways, according to the kind of blight injury. If the branch, at the time of the frost, already has some older wood, which is browned on the blighted side but not split off, then the overgrowth edges often gradually push between the dead bark and the wood body and slowly lift the scale-like, dry ‘brown mass of the bark. With each successive year, the overgrowth edges 610 approach more and more closely to one another from the sides until they finally unite, cover the blackened place in the wood and thus push out the previously attached bark and throw it off. iii qo LAM Fig. 146. Young pear trunk with different kinds of blight spots. In Fig. 147, the In Fig. 146, which represents a blighted young pear trunk, we see at the top, the old, blackened, exposed wood body which originally was covered with bark in a fresh condition ; it is left light in the drawing. The bark on the whole side of the tree has been killed by frost, dried up and thrown off from the healthy part by the overgrowth edges which appear after frost. The swollen place at the base of the drawing illustrates the broadening of the flattened trunk, which occurs frequently at blighted places because of the in- creased formation of wood by the uninjured, adjacent tissue. On thin twigs, the frost plates are often very small, but the wood under the dried bark is found to be split radially. The cleft, which closes after the abatement of the frost, is now rapidly overgrown; the dead bark is thrown off at once and the over- growth edges unite. In this, the union takes place after the manner of frost ridges, i. e., the edges rise up like ridges above the normal plane of the annual ring, while the broad wounds which are closed very slowly show the axial cylirder to be flattened at the frozen place. In both cases, however, the overgrowth edges are ~ distinguished by the fact that they arise under the high pressure of the dead bark and, on this account, are smallest at the outermost ends and pointed like wedges. This wedge-like growth of the overgrowth edges, which spread out over the dead surface, is a character- istic of blight in contrast to canker. The overgrowth edges of canker increase in thickness towards the place of injury and, like rolls, sink down into the open split which forms the beginning of the canker. It may easily be seen, that the tissues of the over- growth edges differ according to the pressure condi- tions, under which they arise. This has been discussed more in detail under canker. dark place B corresponds to the frost plate p in Fig. 145; fis a piece of dead bark, the healthy part of which (7), recognizable by its white, glistening, hard bast bundles (hb), is separated from the dead tissue by a diagonal cork zone, adjoining the normal cork covering (K) at 611 B.. The annual ring, produced after the frost, is marked J. If this is fol- lowed back to the place of injury, it is seen to diminish suddenly to a point and to be entirely absent under the dried, dead place in the bark (#, f). Only the next annual ring would be able to push between these. The structure of these pointed overgrowth edges resembles much more the normal wood because of the very scantily formed parenchyma wood and the rapidly appearing thick-walled wood cells together with the ducts, than does the lip-like wood parenchyma overgrowth edges of the canker (cf. “Open. canker’’). In the adjoining Fig. 147 we see, above the pith bridge (m), the normal annual rings, interrupted by darker, sickel- shaped zones (pz), which here appear gray. These zones con- sist at times of thinner walled, ductless, shortened parenchyma cells, and at times of wood parenchyma, richer in starch. In luxuriantly growing varie- ties the radii of the medullary rays, which here are straight, appear somewhat bent and dis- place the longitudinally elon- gated wood cells and ducts from a diagonal to a horizontal direction. It was stated above that the frost plates should be consid- ered as narrowly limited scald injuries of relatively small ex- tent in all directions, which could, however, be found dis- playing all transitions up to large, blasted surfaces cover- ing the whole side of the tree. Fig. 147. Cross-section through a pear stem Besides occurring in _ pears, at a blight spot, produced by frost. such frost plates may also be found in the red beech. On branches of a beech thickly covered by such plates, the browning of the contents of individual cells, scattered through the pith, could be proved to be the final radiation of the frost action in its furthest extension into the healthy tissue. These cells undoubtedly have a different content from the other pith cells, which have remained colorless and, in cell contents, probably approach most nearly those of the medullary crown, which likewise easily become brown, O12 The browning does not extend into the surrounding tissue, as in wound rot, for the cells already existant, as well as those formed later in the imme- diate proximity of the tissue browned by frost, remain clear-walled and healthy. The browned medullary cells contain as much starch as do those not attacked, so that the brown color can not arise from a change in the starch but from some other substance. The pith does not suffer in every case. Often the wood in 2 to 3 year old branches is so browned that a yellow, gum-like filling of the ducts extends up to the medullary crown and the medullary rays also appear brown almost to the centre; the pith itself, however, having no diseased discoloration whatever. Such differences take place in different internodes of the same branch. Nevertheless, the rule holds that the initial stages of browning are found, on an average, in scattered cells of the pith, especially those of the pith crown; that, at first, only the contents and then later the walls themselves become discolored and that this discoloration of the contents seems to consist of a browning and thickening of the cell fluid. The gum-like solid masses can break in sec- tioning into angular pieces. I believe the filling of the ducts must be traced back in part to the hardening of the fluid contents already existing, in this way easily explaining the often drop-like formation of the filling substance. With increasing cold the browning of the pith, as a rule, follows that of the medullary rays and bast parenchyma groups in the bark. In branches of the red beech frost action, limited to individual vascular bundles, can often be recognized; the discoloration is restricted to the inner half of two main medullary rays, attacking first the part of the bundle which belongs to the medullary crown and often ending suddenly with the boundary of an annual ring. At times the wall of the duct may be found unstained or only discol- ored on one side, while the contents seem completely discolored. It was mentioned above that the secondary membrane can also participate in the filling of the ducts and wood cells. At first this swells up and at times, in fact, completely fills the lumen of the wood cell, or of the narrow duct, which then seems colorless and refracts the light uniformly. Besides this, cells and ducts are found which have turned a deep brown; their cell con- tents often lie in the form of drops or rings against the wall, but sharply separated from it. In other cases there is no separation between the cell contents and the cell wall and here the participation of the wall in the change is certain. It also may happen that only an inner layer of the cell wall turns brown, swells up and finally becomes rigid. This swollen layer then has not space enough on the inner side of the cell, or of the duct, and folds inward so that a colorless cavity is found between the brown wall layer, which has been pushed inward, and the outermost, unchanged portion. In the browning of the cambium, which usually occurs only on one side, the contents are only slightly browned and the cell wall does not discolor at all until later. The spring wood, directly adjoining the autumn wood, seems to be most sensitive. It is evident in the bark, that the parenchymatous 613 cells, extending in the form of an arch from bark ray to bark ray, and already elongated, suffer less than the inner, small celled tissue which bounds them. The observations, here mentioned, illustrate frequent, isolated cases but not phenomena of universal occurrence. Finally, a case in the sweet cherry should be mentioned as especially noteworthy. The pith of a one year old branch seemed split at one side up to and beyond the centre and the cells of the periphery of the pith grew out like filaments into the result- ing cavity, similar to the woolly stripes of the apple core. No gummosis was present. The case was observed in the so-called “frost-wrinkles.” It is interesting because it shows that the activity of growth in the pith, which in general occurs only in soft wood trees (Tilia), can be reawakened here. In the above mentioned phenomena of scald is also found, as a rule, an increase of the gum centres in the Amygdalaceae and of the resin centres in conifers, with an increase of the parenchyma masses (Fig. 147 pz) be- tween the normal parts of the annual ring, just as in canker. In canker, it can also be proved that the breaking up of the bark due to a weakening of the mechanical ring corresponds to the breaking up of the wood by parenchyma wood in the same radius. The hard bast bundles are absent from the bark of the overgrowth edges just as are the real, thick-walled wood cells in the wood of these edges. AGGREGATIONS OF PARENCHYMA WOOD. In canker excrescences, we have seen how tender and perishable the wood ring becomes as soon as it passes over into the overgrowth edges of a narrow cleft at the time of the greatest growth activity in the spring. Because of the rapidity of the production of such large tissue masses, the wood ring does not have time to mature prosenchymatous elements but at first is formed of parenchymatous, thin-walled elements which, to be sure, have some advantages as a storage tissue for reserve substances, but show very slight power of resistance to parasitic and atmospheric influences. It is therefore easily understandable that even in healthy trees the appearance of parenchyma, instead of prosenchyma wood, deserves especial attention from a pathological standpoint. Such cases may be found everywhere. The aggregations of parenchyma wood can occur in the trunk in the form of scattered nests, or in ring-like bands, differing in length and width. They have been variously named. We find an enumeration of such cases in de Bary? , who sees in them an hypertrophy of the medullary rays. Rossmassler calls them “Repetitions of the pith,’ Nordlinger, “pith spots,” while Th. Hartig? speaks of “cell passages.’ The most mature form is found in the so-called “moon rings.” These are brown, or white, bands of parenchyma wood, usually extending in a ring partially or entirely around the trunk. This parenchyma wood appears at times to be decayed like 1 De Bary, Vergleichende Anatomie der Vegetationsorgans 1877, p. 567. 2 Hartig, Th., Vollstindige Naturgeschichte der forstlichen Kulturpflanzen. 1852, p. 211. 614 tinder. These decayed tissue masses not infrequently give a cellulose reaction. Such tissue is often found traversed by mycelium. Th. Hartig describes the fungus as Nyctomyces candidus and N. utilis. Rob. Hartig ascribes the mycelium observed in oaks to Sterewm hirsutum Willd’. In other tree genera, other fungi are found which destroy the wood and which are treated more thoroughly in the second volume, p. 385 ff?. In cross-sections of the wood structures termed “‘pith spots” appear as isolated, sharply bounded, somewhat crescent-like, browned, decayed spots, which, like passages, may be followed downward to different distances in the trunk. We owe a thorough study of these to Kienitz-Gerloff*, who observed that in willows, mountain ashes and birches it is caused by the feeding of an insect larva. According to a review by Karsch* Tipula suspecta, Rtzb. is concerned here. This larva feeds “‘on the cells of the cambium and the youngest wood at the time of the formation of the annual ring.” The passages, made by it, are closed as follows :—‘the cells, break- ing through the edges of the wound, grow quickly and divide with delicate | cross-walls. At the same time, a complete closing of the cambial ring takes place and, from now on, the normal wood and normal bark are formed over the wound surface, while the cavity, perfectly independent of the new cambium, is closed by the increase of cells’. These injuries, due to filamen- tous diptera larvae, which bore their way into the cambial zone, especially at the base of the trunk and the root neck, sometimes even higher up in the shaft, and in water sprouts in May and June, are primarily considered as producers of pith spots or “brown chains” only in the varieties of trees named. Kienitz remarks that similar structures in other trees, especially conifers, do not arise from the diptera larvae above mentioned. In regard to the pith spots of the birch, v. Tubeuf® confirms the inves- tigations of Kienitz and mentions thereby that G. Kraus explains these cell aggregations as normal structures. De Bary, as was said above, speaks of hypertrophies of the medullary rays and, at the first glance, one also gets the impression that the pith spots are caused by a widening of the medullary rays. These are seen actually to become broader. before they enter the aggregations of parenchyma wood and their cells take on the polyhedric, thick-walled, greatly pitted appearancé of the cells of the pith spot which are filled at times with starch and brown tannic substances. In fact, it is often found that the medullary rays, when entering the pith, are broadened and unite laterally. But, supported by my “barking experiments,” I con- sider the newly formed, filling tissue to be a product of some cell increase which can take place not only in the medullary rays but in all the tissue 1 Hartig, Rob., Zersetzungserscheinungen des Holzes, p. 129. 2 Paging in the German original. 8 Kienitz, M., Die Entstehung der Markflecke. Bot. Centralbl. 1883, Vol. XIV, p. 21 ff. Here also bibliography. 4 Bot. Jahresbericht. Jahrg. XI, Part 2, p. 518. 5 Bot. Jahresber. 1883, Vol. I, p. 182. 6 v. Tubeuf, Die Zellgiinge der Birke und anderer Laubhélzer. Frostl. naturwiss. Zeitschr. 1897, p. 314. 615 forms composing the annual ring. The growth of the medullary, or the bark rays, only exceeds that of other tissues in all processes of wound heal- ing; it thereby becomes predominate. Also if, in the above mentioned “‘moon rings,” the boundaries between the already destroyed parenchyma wood of the annular bands and the healthy tissue are investigated, not infrequently a striking widening of the medullary rays is found, especially in oaks. In conifers, especially pines, a still more extreme form of disturbance may be found, the so-called “ring-barking.” At times, when the trunk is split, a complete cylinder, beginning at the healthy central portion of the trunk, separates from the apparently equally healthy peripheral wood, as from a shell. This takes place because the tissue is destroyed in one, and indeed only one annual ring, becomes rotten and traversed by mycelium. This form of ring barking is distinguished by its sound, healthy core from the one studied by Robert Hartig' in the pine, in which a wound parasite, Trametes Pini (Brot.) Fr. causes the destruction of the core but does not extend into the healthy sap-wood. MHartig describes the rapid advance of the mycelium in the medullary rays and, after having discussed the destruction of the wood caused by the mycelium, the dissolution of the incrusting substances and the retention of the cellulose in the wood fibres, says that, “as the result of the collapse of the wood which is connected with this decay and loss of water, not only are radially extending cracks formed but often the outermost annual layers are loosened as a mantel from a thicker or thinner core. Thus annular clefts are produced which can have led to the name of “ring barking.”” We are here, therefore, concerned with a form of very extensive red rot, or heart rot. According to v. Tubeuf, the fungus appears also in spruces and has been observed in larches and white firs and, in America, in the Douglas fir. Emphasis should be laid on the fact that this mycelium spreads “very easily in one certain annual zone” and the diseased, white tissue aggregations, which now consist only of cellulose, may be found abundantly in the spring wood”*. This seems to me to indicate that the fungus finds greater resistance in the adjacent annual rings, i. e., the annual ring already attacked must necessarily have been more porously constructed. Accordingly, bands of parenchyma wood might contribute especially not only to infection of branch wounds by Trametes and other wood destroyers, but also to their distribution in the trunk. FALsE ANNUAL RINGS. DouBLeE RINGs, Etc. Its is a well known fact* that the size and constitution of every annual 1 Hartig, R., Wichtige Krankheiten der Waldbaume. Berlin 1874, p. 55. 2 y. Tubeuf, Pflanzenkrankheiten durch kryptogame Parasiten verursacht. Berlin 1895, p. 471. 8 Hartig, R., Lehrbuch der Pflanzenkrankheiten. Berlin 1900, p. 172. 4 Kiister, E., Pathologische Pflanzenanatomie. Jena 1903. p. 25, ete. Here also pertinent bibliography. — 616 ring in woody plants depends upon the amount and kind of leaf activity. This has been thoroughly treated in forestry literature. Every considerable interruption in the activity of the leaf apparatus makes itself felt in the wood and can lead to the omission of wood formation in one side of the tree, or at the base of the trunk and in the root. If the cambium, which had been active in the spring, is incited to renewed increase in the same year after a period of inactivity, it begins the formation of a new spring wood which passes over into autumn wood, sometimes more slowly, sometimes - more quickly. In this way a new, normal, annual ring is produced. In such cases are found semi-circular double rings, or others encircling the whole girth of the trunk. We owe exact studies on this subject to Kny't, who determined espe- cially clearly in Tila parvifolia that, after the sprouting of the buds on shoots which had been entirely defoliated by caterpillars, a second annual ring was formed. The boundary between the newly formed spring wood and the wood ring produced before defoliation is sharp. In Ratzeburg’s? study we find repeated examples of the dependence of the formation of the annual ring on the time of defoliation. Since different insects can cause complete defoliation, at different times of the year, a weakening of the growth of wood is found sometimes in the same year, but, at other times, not until the following year (when the deposition of reserve substances is scanty). In 1886, I was able to add the action of frost to the causes which can bring about the formation of false annual rings. In 1895 R. Hartig* pub- lished a treatise in which he described frost rings in the oak and fir and considered also a different mechanical effect, viz., a drooping of the shoots due to a loss of turgidity. This bending of the shoots became permanent and could be found the following year. The drooping can also occur as a result of the destruction of the pith parenchyma. In the last edition of Hartig’s text book*, frost rings from the wood of a pine and of a spruce are illustrated with the remark “in older parts of the trunk of the pine it was found that a so-called double ring was produced in each year of late frosts. I later confirmed the fact also in spruces and other conifers, that a late frost not only injuries the youngest shoots but even produces the ‘double rings’ formed in parts of the trunk which were ten years old.” O. G. Petersen® describes and illustrates a similar disturbance in the structure of the annual ring of beech trees which had suffered severely from frost on the 17th to 18th of May, 1go1, in Holland. Nordlinger® had 1 Kny, L., Uber die Verdoppelung des Jahresringes. Sep. Verhandl. d. Bot. Ver. d. Prov. Brandenburg 1879. Here also discussion of earlier theories. 2 Ratzeburg, Waldverderbnis, I, p. 160, 234; II, p. 154, 190. 8 Hartig, R., Doppelringe als Folge von Spitfrost. Forstl. naturw. Zeitschrift 1895, p. 1-8. 4 Lehrbuch der Pflanzenkrankheiten. Berlin, Springer 1900, p. 220, 221. 5 Petersen, O. G., Natterfrostens virkning paa Bogens ved. Sep. Det forstlige Forsogsvaesen, I. 1904. 6 Nordlinger, Die fetten und die mageren Jahre der Baume. Kritische Blatter f. Forst- und Jadgwissenschaft, 1865, Vol. 47, Part 2. 17 already observed in the normal wood formation a ring-like break in the form of a line of reddish tissue. Corresponding reports and observations may be found elsewhere which, however, do not contain any new points of view. Studies on canker phenomena increased our understanding of the disturbances in the formation of annual rings. I have proved in the apple canker that an annual ring, which is simple and normal on the healthy side of the branch, may be subdivided on the canker side into several ring zones. My recent studies on the oak have shown how such a breaking up of the tissue may take place. EXPERIMENTAL PRODUCTION OF PARENCHYMA Woop By FRostT ACTION. The cases of the production of parenchymatous wood tissue instead of normal parenchyma, described in the preceding chapter as “pith spots,” “parenchyma wood bands,” “ring shells,” etc., arise from a variety of causes which, however, as a whole, agree, in that the cambium in different parts of, or to the whole extent of the annual ring, is more or less freed from the pressure of the bark girdle binding it. It may be concluded from subse- quent observations that frost, and especially spring frosts, furnish one of the most essential and frequent causes of such a loosening of the bark girdle. In 1904, in May, a frost had so greatly injured the younger oak shoots near the edges of different forest plantations, where these bordered on open meadows, that a number of branch tips were completely frozen while only ~ the leaves of others had blackened and dried; later they continued their growth at the tips. When these shoots, within a few weeks, had again formed new leaves, they were cut for investigation. They showed great differences in structure, among others that illustrated in Fig. 148. We recognize an irregularly pentagonal medullary body (m)_ sur- rounded by slender wood rings (4) more strongly developed on one side. This wood ring, however, on the outside, does not adjoin a regular cambial zone, as is the case in the normal branch, but passes over suddenly into a porous, wide-celled parenchyma wood (fh) which becomes thicker walled toward the bark and only rarely leaves recognizable a cambial boundary zone between itself and the bark. That this girdle (ph) formed of porous tissue still belongs to the wood ring and has arisen from it, is proved by the short-celled, vascular elements (g’) scattered in the zone of thin-walled cells which, in the structure of their thickening layers, seem similar to those of the ducts in the normal, first formed wood ring, or resemble them. This presence of short ducts, or duct cells, and the condensing of the whole zone of thin-walled cells at its periphery by the occurrence of thick-walled elements, resembling the true wood cells, shows, therefore, that this branch, injured by frost, had re-adapted itself to the normal formation of the wood ring a short time after the cessation of the frost action and the formation of the parenchyma wood. If this branch had been allowed to continue growth until frost, we would then have had a second false annual ring, as has been observed by earlier investigators and was discussed in the preceding chapter. 618 The bast ring (>) has been less affected; only the contents of the young bast cells are usually found to be brown, corresponding to the filling of the 0); x50 }0 {2} ue pase SoS Zee EXO OSS Eee ie, p ene o OS eG \) LA Cay OX 5 @ fase Nene QS Wusees Q ae, se ese py pare G ne INGIUENceesecs Om Be PET oa iN wich $3 1) a YO eae | 2S } BA Yer HESS e GOAT TT 2onke BAU Sselb. 2 Ane. me ey Hy at Peres} ones : yal 2 a5 se NAL Salugtogns) ai HAY YZ Ay) KATY is OG Ly) 4 7 SOLet SSSs2eS Pt A healed internal frost wound on a young oak branch, caused by injury from a May frost. 3 ¢ cambial zone, z zigzag line with swollen cell walls, ¢ vessels in the normal wood. Explanation of the other letters to be found in the text. different ducts of the wood ring with a reddish yellow, gum-like substance. The bark parenchyma contains single, brown groups. No special phenomena 619 of discoloration are visible in the collenchymatous outer layer of the bark but may be found in the pith crown, which appears to be entirely brown. This browning decreases with the distance towards the healthier base of the branch at which the sections were made. At the base of the branch we find only scattered cells, with yellow, swollen contents. A difference in direction of the holes thus produced becomes noticeable in the abundantly recurring cracks. Within the pith disc may be found the greatest radial extension of the holes which is seen to be connected with a peculiar, radiating formation of the pith. This is found to be distended into a pentagon, produced by the passing of the vascular bundles, com- posing the wood ring, out from the wood ring. As indicated above, the cause of this extension of different bundles lies in the fact that, in each ot the five corners of the pith, the vascular systems, destined for the five next higher leaves, are about to make their way outward through the bark into the leaves. The pith body for the leaf lying next above the part of the branch here illustrated, is naturally furthest distended and is adapting itseli to passing over, as a pith connection (mb), into the next bud. The bundles of the two higher leaves, lying only one or two internodes above the place of the cross-section, still lie within the complete wood ring, but even they have already formed noticeable distentions of the axial cylinder (at the right in the figure). The bundles for the 4th and 5th leaves, following the spiral of the leaf insertion, still le entirely within the wood ring and indicate their lateral appearance only by a slight outward convexity (at the left side of the figure). Between them the pith body is continued only in the form of a broadened medullary ray and has not widened into an actual pith connection. The holes (/), produced by the rupturing oi the tissue, correspond in size to the amount of distention of the pith. The larger these are, and the nearer they stand to the buds belonging to them; the stronger is the radial splitting. Differing from those in the pith, we find the holes (/’) in the bark extending tangentially. They are produced, in part, by the throwing off of the peripheral collenchyma of the parenchyma, rich in chlorophyll, in part, however, by the rupturing of individual parenchyma cells. It should be noticed, that the formation of holes in the bark, as also the formation of thin-walled tissue (ph-lg), is much greater on the side of the branch where the bundle has separated most widely from the main vascular system than on the opposite side. Moreover, this also explains the fact that, in the investigation of branches injured by frost, as a rule, one side 1s found more greatly affected than the other. The natural conclusion, that the action of the frost has been greater on one side is usually erroneous. For, if a num- ber of successive internodes are examined by series of sections, the investi- gator will be convinced that sometimes one side of the same branch shows a greater injury from frost, sometimes the other, according to the position of the bud, near which the section was made. The closer to the bud, the stronger the action of the frost in the branch. 620 After numerous vain attempts, the above described disturbances in tissue, and processes of healing, could at last, in the spring of 1905, be produced artificially. In April potted specimens of 4 to 5 year old oaks were brought into a greenhouse for forcing. The tender young shoots were exposed in May for one night to a temperature of 4 degrees C. below zero in a freezing cylinder. The plants were then left out of doors and investigated the middle of June. Here, exactly as in the observations made the previous year on naturally frozen oaks, the branches, injured by frost, showed very different forms of disturbance. Among them were some resembling typically the natural injuries described above; only the processes of healing, which here begin clearly at the medullary rays, were much less extensive, which may be traced to the fact that potted specimens always develop more weakly and slowly than forest trees growing in open ground. The observation was also made, that the clefts in the tissue seemed to be less extensive, the older and stronger the branch was at the time of the frost action. I conclude from this that injury from frost only leads to the formation of parenchyma wood within an annual ring when it affects very young, tender shoots at the time of the greatest growth in length. Besides this, favorable, warm weather must follow the frosty nights so that cell increase can continue at its former rate. The building material, in the form of mobilized reserve substances, is present in the branch, injured by frost, in the same amounts as before the action of the frost, but the newly produced cell elements develop differently because the conditions of tension in the branch and the resulting pressure on the cambium have become dif- ferent, due to the breaking up caused by frost. THe THEORY OF THE MECHANICAL ACTION OF FROST. The phenomena, which came to light in the above described natural and artificial frost injuries to young branches, however they may vary, can be traced to simple mechanical processes. In this we still refer to the above illustration of the oak branch in which we see that the pentagonal wood ring, surrounding the medullary disc, passes over suddenly into a light zone of delicate tissue (J/g) and this gradually forms, toward the perihpery, tougher elements, which have the character of normal wood (/). The illustrations 2 to 6 in Fig. 149 serve to orient the place of origin of the thin-walled tissue. These show enlarged portions, drawn cell for cell from the right side of the above figure (Fig. 148) at the region of the sec- tion, lying between /g and b. In all the drawings, the upper angle is the one toward the pith, the under angle the one toward the bark which, in fact (Fig. 149 2, 4, 6) even shows bark elements. The uppermost cell groups, in part designated by h, form the boundary of the wood ring which was present before the action of the frost. These pass over directly into the thin-walled tissue (/g) of the thin-walled stripe (Fig. 149 2, 3). In this, the medullary rays, which in normal wood are only one to two cells broad (Fig. 149, 5 m s) have become enlarged and irregularly many-celled. They 622 contract to their former breadth only where the porous tissue passes over into the secondary wood (Fig. 149 2, 3, h’) with regular ducts (g’). Then a normal cambial zone is formed again (Fig. 149 2 c) which, at the time when the medullary rays were broadened excessively, had beeome irrecog- nizable, since cell division took place absolutely irregularly in different regions of the ring of thin-walled tissue. As soon as the formation of the regular cambial zone begins again, the loose bark tissue also differentiates itself in such a way that juvenile bast groups (Fig. 149, 4 b and 6 b b’) again becomes recognizable. The fact, that no dead tissue of any kind is present between the wood, matured before the action of the frost (h), and the looser, thin-walled tissue (/g), proves that the young wood, the sap wood ring, has passed over directly into the parenchyma wood of the ring of thin-walled tissue. Never- theless, this parenchyma has retained its connection with the wood body. On this account, it 1s not surprising that, after the cessation of the causes which had brought about this parenchymatous formation of wood, the tissue gradually re-assumes the normal wood character and adapts itself to the formation of a secondary wood ring (Fig. 149 2 and 3h’). In fact, indi- vidual elements of the sap wood, the thickening of which had advanced somewhat further at the time when the formation of parenchyma wood began, had continued the thickening of their walls. On this account, we find isolated tracheal elements (Fig. 149 4, tr) in the centre of the paren- chyma wood. The zone of thin-walled, porous tissue (/7) in the cross-section of the oak branch (Fig. 148) is, therefore, only a modified wood ring which has passed over into an excessive new cell formation. Since such a cell increase can arise only from elements which still possess their cambial nature, it must necessarily be concluded that the very youngest cambial zone elements, i. e., the sap wood, have produced this parenchyma wood. As a matter of course the real anatomical cambium, together with the young bark, has par- ticipated in this cell increase and, in this way, produced the abundant tissue in which it is not possible to distinguish where the transition from wood to bark takes place. We now ask what may be the cause of the formation of this profuse tissue zone? The answer can only be found in the removal or weakening of the constricting, compressing influence, exercised by the bark girdle, as a whole, on the youngest tissue, i. ¢., the cambial region. This cause is indicated bv the holes in the bark tissue (Fig. 148 I’, at the right). Such tangential holes in the healthy tissue are produced by the’ upraising of the tissue lying above the hole from that lying beneath it. It can only be raised, however, if it has not enough room on this underlying parenchyma which is caused by a greater tangential distention. Conse- quently, a stronger tangential strain has occurred in these outermost tissue layers than in the adjacent inner layers of the bark. 623 Caspary’s measurements in freezing should be recalled here. The peripheral layers contract earlier and more strongly than do the central layers. This contraction with cold is stronger tangentially than radially and greater in the delicate parenchyma than in the prosenchyma wood. Con- sequently, with the action of frost, there must take place everywhere within a woody axis a preponderance of tangential strain over radial contraction and, under certain circumstances, this must increase to a radial splitting of the tissue.. If the wood ring is thought of, first of all, as isolated, this preponder- ating tangential contraction in places of least resistance would necessarily lead to such clefts as would correspond to the gaping frost cracks in old trunks. Therefore, inner clefts must be produced from purely mechanical causes and, in fact, in the medullary rays and medullary transverse connec- tions. Such are actually shown in the illustration of the oak branch, injured by natural frost (Fig. 148). If we now consider the primary wood ring in its relation to the adjoin- ing bark girdle, we must refer again to the fact that the bark girdle, of © which the peripheral cells are larger tangentially than radially, contracts more strongly tangentially and, therefore, is strongly torn in this direction during the action of frost. If the frost grows less, this cracking may cease, indeed, but its effects remain, for the tissue which may thus be stretched, is not absolutely elastic and does not contract to its former volume. In this way each frost action leaves behind an excessive lengthening of the peripheral tissue layers in proportion to the adjacent layers which lie more toward the inside. The bark body, as a whole, therefore, is longer and either does not have room enough on the wood cylinder so that in places it is raised up from it, or it at least curves outward, i. e., it decreases its constricting influence on the cambial elements of the wood cylinder. The cambial zone responds to this with a formation of parenchyma wood, as may be seen in every wound in which the bark is raised. If the bark girdle closes together again into a connected layer the cambial cylinder of the branch, by growth in thickness, must again resist the constricting effect of the bark and, on this account, again forms normal wood elements. Thus the formation of the parenchyma wood bands in young branches comes under the same law of unequal contraction which, in old trunks, leads to the production of gaping frost clefts. THE RUPTURE OF THE CUTICLE. The experiments on potted specimens of forced oaks, mentioned in the previous section, proved the fact, not known until then, that, on superficially browned, or still green leaves, i. e., those outwardly but little affected, a repeatedly interrupted black, very fine line is formed on the under side, which gives the impression of very fine particles of soot which had settled on it in places. With a higher magnification, it is seen that this line consists of small raised places in the outermost cuticular layer which, because of its 624 granular condition, retains the air, and therefore appears black. The small granular papillae still remained when the leaf was destroyed by sulfuric acid ; in which treatment the leaf curled up like a worm and the epidermis of the upper side puffed out in places. This result agrees with discoveries which had been observed earlier in beech trees after natural late frosts, and which we could prove also on oaks in the open. In the production of such scarcely perceptible rupturing of the cuticle, some special conditions must also have co-operated which were present accidentally in the experiments but do not seem to be always effec- tive in other experiments or in nature, for, soon after late frost, such injured oak leaves could be found in some localities but not in others. Probably a definite condition of turgor in the leaf is connected with it and this will be dependent again on the constitution of the cell contents at any given time. A conception of the fine differences, which are decisive in frost inju- ries, is obtained from the observation that dead particles of tissue, injured by frost, may be found at times in the centre of the mesophyll of the leaf, which apparently is but little, if any injured. The fact that, in experi- ments, these cuticular breaks appear only on the under sides of the leaves may be traced perhaps to a constitution different from that of the upper cuticular covering, for it is found that in the action of sulfuric acid, the upper covering turned a bright lemon yellow, which color shade was scarcely perceptible in the cuticle of the under side. I would like to lay especial value upon the discovery that, under certain circumstances, a rupturing of the cuticular glaze can be produced by light frost. In other breaks in the cuticle (in pomes) fungus spores were found lying in the line of the break and it may, therefore, not be out of place to assume that, in these protected places, such fungus spores have the best opportunity to germinate and to sink their germinating tubes into the organs. In this way might, therefore, be explained the attacks upon apparently per- fectly healthy leaves and fruit by fungus infection after a light spring frost. Voglino’s' reports might be referred to here. In 1903, after some frost in April, he found that the fungous parasites had an especially large distribu- tion in plants injured by frost. Thus is explained also the phenomenon of the so-called rust etchings in connected rings and irregular surfaces on our fruit. They are cork formations which have set in, in the cuticular tears, as a result of the processes of healing, while the normal cork etchings on the fruit usually begin at the stomata, or rather, the lenticels. PROTECTIVE MEASURES AGAINST FROST. (a) SNow COVERING. The process, universally used for protecting plants against frost, con- sists in surrounding them with substances which are poor conductors of 1 Voglino, P., L’azione del freddo sulle piante coltivate, specialmente in rela- zione col parassitismo dei funghi. Atti accad. di Torino XLVI. 62 wal heat. Grapevines, roses, etc., are covered with earth or leaves, or the trunks are wrapped in moss, straw and the like. All these means are good but in cold winters, with a moderate snowfall, one should not delay throw- ing the snow from the streets on to the covered plants. It is well known that wrapped trunks of roses, for example, often freeze; this is explained by investigating the temperature under the covering material with a ther- mometer. It is found to deviate but little from the temperature of the outer air. On the other. hand, if the soil under the snow covering, possibly 15 cm. deep, is investigated, it is found to be considerably warmer. Goppert’s investigations! are the best on this subject. In February, 1870, the tempera- ture was very low. The thermometer fell on the 4th to 12.6 degrees below zero, On an average, and yet in this, the temperature was only 3 degrees below zero under the snow covering, 10 cm. deep. The temperature of the air on Feb. 5 was 147 degrees below zero, the temperature under the snow 4.6 degrees below zero, . ; on Feb. 6 was 17.6 degrees below zero, the temperature under the snow, 5 degrees below zero, on Feb. 7 was 16.7 degrees below zero, the temperature under the snow, 5.5 degrees below zero, on Feb. 8 was 16.7 degrees below zero, the temperature under the snow, 6.5 degrees below zero, on Feb. 9 was 15.4 degrees below zero, the temperature under the snow, 6 degrees below zero, ; on Feb. 10 was 14.9 degrees below zero, the temperature under the snow, 6 degrees below zero, on Feb. 11 was 15.8 degrees below zero, the temperature under the snow, 5 degrees below zero, on Feb. 13 was 5.7 degrees below zero, the temperature under the snow, 2 degrees below zero, on Feb. 16 was 2.8 degrees below zero, the temperature under the snow, 1.5 degrees below zero. The soil under the snow covering was frozen 36 cm. deep, but its tempera- ture, even on the cold 5th of February, at a depth of 5 cm., was only one degree below zero. It would scarcely be possible to find more eloquent proof of the useful- ness of a snow covering. This explains the possibility of polar vegetation. The greatest degrees of cold in the polar zone as yet observed (40 to 47 degrees below zero) affect only the trunks of the trees which project above the snow, but not the roots. Perennial, herbaceous plants are just as little affected. These stand in a soil with a temperature under the snow cover- ing of only a few degrees below zero. The snow covering, to be sure, does not arrest freezing but does prevent loss of warmth through radiation, the penetration of greater degrees of cold and a rapid change in temperature. But, even with us, the existence of many plants is more often connected with snow covering than we think. The freezing of seed would occur much more frequently when a long damp and moist autumn favors plant development, if the snow covering were not deposited on them, which keeps off radiation and the great fluctuations in temperature, so frequent in our latitudes. We see often enough how easily insufficiently protected, or fully 1 Bot. Zeit. 1871, No. 4, p. 54. 626 exposed parts of plants freeze, if struck by sudden strong sunshine. The cell contents, suddenly struck in a condition of rigidity, the result of cold, are found poor in water content and drawn back from the cell wall, and do not have time to distend again, by absorbing water, into their normal rela- tion with the cell wall, and, thereby, the surrounding tissues. In this way, the disorganization of the cell begins. These are the processes which occur with spring frost and are especially advantageous for garden plants. (b) Tue Use oF WATER. Especially herbaceous plants which are suddenly exposed to frost are benefited if the hard frozen parts of the plants are watered with right cold water and then shaded. The water on the plants freezes to an ice crust, thus raising slowly the temperature of the plant itself to zero, and it can gradually be warmed further above this temperature, after the thawing of the crust. On the same principle of gradual warming rests the plunging of frozen potatoes and roots into a vat full of cold water and the piling of frozen cabbage heads in heaps which are then covered with straw mats. In spring and autumn, when the air temperature does not fall-to zero , but the plants, because of their radiation of heat under a bright sky, cool down below zero, become covered with frost and freeze, they may be pro- tected by substances arresting radiation. Covers and mats are spread over the plants, also very thin cloths are effective here and, if no other covering material is at hand, a thin layer of brush is very useful; even perpendicular walls have proved excellent protection against frost. They are effective, on the one hand, by keeping off the wind and, on the other, by decreasing radiation from the plants. In trees, trained against stone or wooden walls, in addition to the very considerable decrease in radiation of the trees on the side next the wall, the wall itself gradually gives up its stored heat to the benefit of the trees. A less effective, but not entirely rejectable, protection against frost is recommended by older authors and is practical in gardens in spring. The trunks of trees are wound with straw rope one end of which dips into water. Straw and tow ropes are suspended in all directions over beds of blooming spring plants some distance above the surface of the soil, their ends being held fast by stones in a vessel filled with water. To understand the favorable effect of this process, one should remem- ber the great latent warmth in the water. If the water in the saturated straw ropes freezes, heat is set free which is advantageous, since it prevents the penetration of the cold to the underlying parts of the plants. Thus plants, near larger bodies of water, freeze less easily. One measure used with good results for potted plants, at a time when night frost may be feared, consists in a decreased watering, whereby the tissue of the plant 627 contains less water when it is exposed to the frost. A more abundant evaporation removes more heat from the plant and, therefore, heavily watered plants will cool down more than those which are less turgid. (c) Errect oF WIND. Winds can also act favorably inasmuch as a storm begins with warmer weather, which hastens evaporation, thus removing the water from the tissues. Experimental proofs are furnished by Aderhold’s experiments’ with artificial rain. In each of six specimens of pears, which had been kept for several months in summer in a “rain chamber,” five examples were found, after a winter frost, to be completely frozen and the sixth partially frozen, while of the check plants, which had stood in a dry chamber, only 2 were frozen and 4 were uninjured. Nevertheless, no general rules can be formed in regard to the action of wind. Each locality has its own special requirements. If, for example, the statement is made that winds act favorably, this refers only to those cases where no such permanent effect of the wind is concerned, as is seen on sandy coasts. There the action of the roots is the determinating factor. Even if they do not freeze, they still cannot take up any more water, while the aérial portions still transpire strongly. Plants can directly dry up under such conditions. The discoveries of Hédfker-Dortmund* are noteworthy in this connection. He protected the aérial portions less, but covered the soil, which in autumn had been loosened up about his plants, with manure or damp peat mould and watered the evergreen bushes on sunny frosty days. Because of the covering, the frost could not penetrate very far and the roots could constantly supply water to the aérial portions. In decorative planting, where the finer varieties of conifers are abundantly used, it seems advantageous, in very windy regions, to use the bluegreen forms instead of the pure green ones. Some growers maintain, in fact, that the former are more resistant. Care should further be taken that the base of trees or plants, which throughout the year have possibly been protected by a moss growth, piles of leaves, forest litter and the like, are not exposed in the autumn in clear- ing up, etc. It has been found, in fact, that portions of plants matured under the protection of soil or leaves, contain a sap which freezes more easily than that of portions constantly exposed to the air. Sutherst* has proved this for celery, carrots, and the hearts of cabbage heads. Besides this, even if the constitution of the cell sap is not a determinating factor, at least the transportation of water is decreased in the roots and trunk 1 Aderhold, R., Versuche iiber den Hinfluss haufigen Regens auf die Neigung zur Erkrankung von Kulturpflanzen. Arb. aus der Kais. Biol. Anst, f. Land- u. Forstwirtschaft. Vol. V, Part 6, 1907. 2 Hofker, Windschutz und Winterschutz. Prakt. Ratgeber i. Obst- u. Garten- bau 1907, p. 61. 3 Sutherst, W. F., Der Gefrierpunkt von Pflanzensaften. Biedermanns Cen- tralbl. 1902, p. 401. 628 which have been robbed of their protective surroundings ; they thereby cool more quickly, thus increasing the danger of drying". The importance of leaving the dead litter of the plants (leaves, bunches of grass, flower stalks of the past year and the like)on seed beds and bushes until late spring is not sufficiently appreciated. Not only is their effect as a protection against frost concerned here, but also as a protection against the drying spring winds. Almost every year we make the discovery that plants have come well through a severe winter and evergreens have retained their leaves, but if windy, dry weather sets in a few days after the snow has melted, the leaves, which had remained juicy, dry up. It is possible that, with this rapid drying of the tissues, a similar change may take place in the protein of the protoplasma; Gorke? proved this recently to be due to frost action. The result in many plants is a complete case of leaf casting disease, which is absent where protection has been afforded by the litter of the previous year. Often our most common perennial blos- soming bushes, grain seeds, tree seeds, etc., are not destroyed until dried in the spring. d. SMUDGE.. All these preventative methods may not be used universally in agricul- ture, but the use of smudges which Mayer* has rescued from oblivion, may deserve still more consideration from the agriculturalist. It was previ- ously repeatedly recommended by Goppert* and Meyen® and supported by. experiments. Fires which develop a good deal of smoke are ignited on the pieces of ground where injury from frost is feared. This process, which, according to Boussingault, had been largely used by the old Incas in upper Peru and is said to have repeatedly found extensive use among the older peoples, is now used again as a protection in vineyards. Accord- ing to Goppert, Olivier de Serres in 1639 and later Peter Hogstrém in 1757 endeavored to determine experimentally the effectiveness of the pro- cess. In Wurtemburg as early as in 1796 and in Wirzburg in 1803, regu- lations existed, according to which in the autumn, when danger from frost occurred, growers were obliged to light smudges for the vineyards. In Grinberg, Silicia, this method was used for a long time, but it was given up 1 Kosaroff, P., Einfluss verschiedener Ausserer Faktoren auf die Wasserauf- nahme der Pflanzen; cit. Just’s Jahresbericht 1897, I, p. 75. 2 Gorke, H., Uber chemische Vorginge beim Erfrieren der Pflanzen. Land- wirtschaftliche Versuchsstationen LVX, 1906, p. 149; cit. Bot. Centralbl. 1907. Vol. 104, p. 358. The author explains the cause of death from cold as follows: The sap gradually becomes such a concentrated solution, due to the elimination of water from the Cell, in the form, of ice, that a precipitation of the soluble protein bodies takes place. He bases his theory on experiments with juices extracted from healthy and frozen plant parts, Fresh vegetable sap contained considerablv more water soluble protein than that which had been frozen. The degree of cold at which a precipitation of the proteins takes place in extracted sap varies greatly in the different plant species. In summer barley and rye it fluctuates between 7 to 9 degrees below zero. In winter barley and rye, between 10 to 15 degrees below zero; in the needles of Picea excelsa it reaches 40 degrees below zero. Reactionary changes can also codperate in freezing. The phosphoric acid, for example, as an aid, is weaker at higher temperatures, and is stronger when cooled down. 3 Lehrbuch der Agrikulturchemie 1871, I, p. 382. 4 Warmeentwicklung 1830, p. 230. 5 Pflanzenpathologie 1841, p. 323. 629 from a lack of general co-operation, despite the fact that, for twenty years, it had been used with good success by one proprietor. General co-operation in any region is necessary, for otherwise a single proprietor frequently does a service to his neighbor upon whose fields the wind drives the smoke, without obtaining any service in return. Special regulations for the use of smudges are not necessary. Any clear night, toward morning but before sunrise, the fires are lighted and fed with damp litter, moss, straw, etc., in which care is taken that the thickest possible smoke is carried over the fields. Naturally the warmth produced by the fire is not effective here; it cannot be felt even a short distance away from the centre of the flame, but the smoke, like the straw mats spread by gardeners over the plants, or like clouds, is beneficial since it prevents too great cooling from radiation. We know from Tyndal’s discoveries that a number of substances, like carbonic oxid gas, carbonic acid, marsh gas, ammonia, hydrogen sulfid and volatil oils, in the finest possible distribution in the air, reduced to a very small amount its capacity for letting through rays of warmth. Water vapor’ ‘has a like effect. Tyndal determined that this took up an amount of heat fifteen times greater than that taken up by the whole (impure) air in which it was distributed. The process is, therefore, as follows :—During the day, the sun sends its heat to us in radiant and dark rays, part of which the soil reflects, but absorbs the greater part, which it retains until the air becomes cooler than the soil. When this condition appears an equilibrium of heat tends to set in, since the earth now gives up its heat to the cool air in the form of dark rays. If, however, the lower layers of the air are strongly laden with one of the above-mentioned gases, or with water vapor, the vapor itself takes up the warmth radiating from the soil, instead of conducting it into the upper regions of the air. Tyndal shows how great the amount of heat is, which is taken up by the lower-layers of air. “If we consider the earth as a source of heat, at least 10 per cent. of the heat given off by it is held within ten feet of the upper surface.” By this absorption of the dark rays of heat the lower layers of the air, rich in water, form a protective mantel about the earth which, as a result, does not cool down so far as it otherwise would. The smoke produced by the fire is, therefore, an artificial covering, full of water vapor, which, in combination with the still partially unknown products of distillation, decreases the permeability of the atmos- phere for the dark rays given out by the surface of the field. We omit a special enumeration of the commercial smoke candles and bricks recently made for the purpose of producing smoke at the time of frost, since new ones will always appear with the advance in technic; refer- ence to the existence of such articles is sufficient. It need only be mentioned that, recently, in smoking vineyards, the smudging material was carried about in carts* in order to overcome the blowing of the column of smoke by suddenly changing winds. The use of smoke carts is said to be the most 1 Tyndal, Die Warme betrachtet als eine Art der Bewegung. Deutsche Ausgabe von Helmholtz und Wiedemann 1867. 2 Burger, Riucherkarren. Prakt. Ratg. im Obst- u. Gartenbau 1906, p. 128. 630 extensive in the town of Colmar, where a smoke department has developed and has been well organized ever since 1884. Colmar lies on a plain and the danger from frost is greater on plains than in higher regions, as was shown, for example, in 1903 in frosts in Florence. Here Passerini! found fruit trees and asparagus greatly injured at an elevation of 40 m. above sea level, but perfectly healthy 100 m. higher. In Colmar iron carts were used, which contained possibly 16 litres of fluid tar. After the tar had been ignited they were drawn back and forth over one field and then taken to the next place (possibly 150 m. distant). When the temperature fell to 1 degree above zero, the smoke department was notified and, at a tempera- ture of zero degrees, the signal for lighting was given by means of gunshots. As a rule, this began in the night between two and three o'clock. The very heavy expense to which the administration was put, because of the smoke department, was paid by a tax on the harvested grapes. We have cited this special case because we believe that only such an organization can have such sweeping results. Frost PREDICTION. On account of the expensiveness of producing smudges for the protec- tion of plants, threatened by late frosts, it is naturally of the greatest im- portance to be able to judge in advance approximately whether night frost will occur. On this account, it is advisable to make use of the frost curve con- structed by Lang (Munich) (Cf. Fig. 150). This is based on psycho- metric observations. If, in spring, the temperature falls in the afternoon and the sky becomes clear, with a cessation of wind, the probability of night frost increases. For the use of the figure, two exactly corresponding thermometers are necessary. The mercury bulb of one is so wrapped in gauze that the under end of the gauze dips into water, thus keeping the cover of the ball moist. This thermometer, because of the constant evap- oration of water, will stand lower than the one beside it showing the ordinary air temperature. [rom the difference between these temperatures the relative humidity and the position of the dew-point can be reckoned, i. e., the temperature at which the water, contained in the air as dew, mist, or rain, will be precipitated. In order, however, that these precipitations of water vapor may become effective as a protective mantel against frost danger produced by radiation, the formation of dew and mist must take place at a temperature above zero; therefore, the point of condensation must lie above zero. If this is not the case, and the air is dry, a night frost may be expected. The mechanical manipulation will, therefore, be as follows: the height of the dry thermometer is read first of all, then the difference between this and the one with the moist mercury bulb is reckoned. The height of the 1 Passerini. N., Sui danni prodotti alle piante dal ghiacciato dei giorni 19-20 April, 1903. Bull. soc. botan. ital. 1903, p. 308. 631 dry thermometer is found on the horizontal line and the amount of differ- ence on the perpendicular scale. If the two lines, starting from these points in the scale, intersect at the right of the curved line which represents the nocturnal frost curve, i. e., intersect among the dotted lines of the scale; then no night frost is to be feared. If, however, the point of intersection appears at the left of the hypothenuse of the triangle, i. e., outside the dotted lines, night frost may be expected with certainty, in case the weather does not change suddenly and warm air currents do not cause the formation of mist or clouds. If, for example, in the afternoon, we find 8 degrees C. on the dry instrument and 4 degrees C. on the moist thermometer, this gives a difference of 4 degrees. The point of intersection of the perpen- S 5 Frosty Nights S Se tial Uige tre 1 i] y ® 1 | .& poctony : 34 ee tl Y ; rae iS me ry it eee “i SPER Ee UNS Tar Pe ir S) ; ! ! ' ora i ! 2 ES 1 , : ! | 1 | 1 oO ' ! \ ¥ ' ! | ' , 4--p--l--4--4- Pes Sq aStoSl= SSS es of ! ' ' ; ) ! ; ' } 1 | ' Ree fe Gari, Sn ARC Tt a efeaea Oar t i ; ' ! ! L : ‘ ' ' J ) OIF TE a Oe Te Be Ie IO FL OID TS. “TFG Height of the dry Thermometer Fig. 150. Curve for finding night frosts; according to Dr. Lang, Munich. dicular temperature line 8 with the horizontal line of a difference of 4 would be outside the dotted lines, i. e., at the left of the nocturnal frost line; therefore a night frost would be probable. Harpy FRUIT VARIETIES. The more we recognize how manifold are the often outwardly imper- ceptible changes due to frost, which becomes apparent only in their after effects, the more important becomes the search for varieties of fruit resistant to frost. If, however, we compare the experiences of fruit grow- ers, it becomes evident that the climatic conditions of different regions may modify the character of the variety in such a way that a variety recom- mended in one place as hardy is susceptible to frost in another, because of earlier development or lesser maturation of the branches. On this account, 632 we will name some varieties recommended as hardy for different localities, some with a continental climate, others influenced by the sea. In this list the injury to the blossom from May frosts is decisive, the condition of the wood less important, because injuries to it come under consideration usually only in less frequent, heavy winter frosts, while blossoms are exposed every year to the danger of freezing. The difference between northeastern and northwestern Germany must be taken into consideration for German plants. In the eastern provinces the influence of Russia is felt, especially in Posen and upper Silesia, because of the invading periods of late frost. Nevertheless, we can record experi- ences which show that certain varieties of the more sensitive pears furnish good table fruit even in Posen. Radowski' lists from winter pears which have stood the test in unfavorable years: Mecheln, Rihas Seedless, Madame Verté, Winter Nelis, New Fulvie, Winter William and Dechant of Alengon. In upper Silesia the following have stood the test*: Amanli’s Butter pear, William’s Christ pear, Bonne Louise d’Avranches, Red Bergamot, English Summer Butter pear, New Poiteau, Pastor pear and Diel’s Butter pear. Of the varieties of apple which have grown well in the district Rybnik, the following are preferred: Red Astrachan, Oldenburg, Kaiser Alex- ander, White Clear apple, Danziger, Hawthornden, Winter Gold Pearmin, Landsberg, Baumann, London Pippin and Kasseler. | The English varieties from the region around Kosel have been espe- cially warmly recommended: Lord Derby, The Queen, Lord Grosvenor, Lane’s Prince Albert, as well as Cellini, Hawthornden and Bismarck. The following are suitable for exposed positions and sandy soil: Brunswick Milk apple, Red Astrachan, and Oldenburg. According to Mathieu the following are especially suitable for the climatic conditions of central Ger- many: White Astrachan, Oldenburg, Red Eiser apple, Kaiser Alexander, Red Cardinal and, for second choice, Red Astrachan, Prinz (Downing), Baumann and Boiken. Of pears, the following have stood the test: Winter-Apothecary, Barons B., Dotted Summer Thorn, Green Magdalene, Small Long Summer Muscatel, Roman Butter pear, Spar pear, Good Gray and Archduke pear*. Although the danger from frost is especially great for pears, yet a May frost at the time of blossoming does not always destroy the crop. Experience shows that good crops are often obtained despite this, because generally only the opened blossoms suffer and those, developing later, produce so much the finer fruit. Besides frost, a continu- ous rain, at the time of the blossoming fruit trees, is especially to be dreaded. _1 Radowski-Schrimm, Winterbirnen fiir den Osten Deutschlands. Prakt. Ratg. i. Obst- u. Gartenb. 17 Dez. 1905. * Langer, G. A., Die Bedeutung der Obstsortenwahl, fiir die Grtlichen und kKlimatischen Verhdltnisse. Deutsche Girtnerz, 1905. No. 38. 8 Jahresbericht d. Sonderausschusses fiir Pflanzenschutz. 1900 Arb. d. D, Landw. Ges, Part 60, p. 247. 633 For the German climate, the following varieties of plums have, on an average, best stood the test: Queen Victoria, Yellow Mirabelle (of Metz), Double Mirabelle of Nancy, the German prune and the green Reine Claude. Of cherries, the following varieties survive the frosty days of spring in spite of their early blossoming: the common sour cherry, Ostheimer Weichsel, Double Glass cherry, large, long Loth cherry, and the Red Mass cherry. For a more moist climate, the varieties might first come under consid- eration which would stand the test in Schleswig-Holstein. As such should be named the Peach Red Summer apple, Degener apple, Bath Beauty, Red June apple, Summer Spice apple, White Summer Kalvill, William’s Favor- ite, the White Clear apple, originating from the Baltic provinces of Russia, and the English varieties, Mr. Gladstone and Irish Peach (Summer Peach apple)*. The majority of the above-named varieties are early apples and we think that the cultivation of early varieties must be recommended for the conditions in northern Germany. ‘To be sure, they usually do not give first class fruit, but, with their shorter period of growth, they have the advan- tage of maturing earlier, the growth of their branches thus passing over into winter with riper wood which, therefore, is harder. In planting new fruit orchards, the varieties should be considered first which have already stood the test in a similar climate and under similar soil conditions. It should not be forgotten, for example, that varieties, suitable for dry climate, usually develop poorly in places by the sea, and conversely. In regard to soil conditions, reference should be made to the fact that varieties. which grow well on light or on heavy soils, would most advan- tageously be chosen from nurseries which have the same physical soil constitution as is found in the place where the trees are to stand perma- nently. A great difference between the place of early growth and the permanent location in which the tree is planted, easily causes an arrestment in growth until the specimen has accustomed itself to the new soil condi- tions. The conditions are the most difficult in marshy soils, even when these have been improved by mixing with lime and the addition of ashes, or kainit and Thomas slag. Stoll? recommends, of the stone fruits, the com- mon sour cherry and (with good liming) the house plum. The following apples do well. Boskoop’s Beauty, Golden Noble apple, Double Pigeon, White Winter Dove apple, Boiken apple, Orleans Reinette, Gray Holland Reinette, Parker’s Pippin and Purple-red Cousinot. The Gravenstein, Prinz and the Golden Pearmain grow well but are inclined greatly to canker. Only the following pear varieties should be named: the Yat, Charneu Delicious and Great Katzenkopf. Of the small fruits, gooseberry and cur- rants are planted on moor lands. 1 Sorauer, Schutz der Obstbiume gegen Krankheiten. Stuttgart, Eugen Ulmer, 1900. 2 Stoll, Obstbau auf Moorboden. Proskauer Obstbauzeitung 1906, p. 182. 634 Snow Pressure, Ick CoATING AND ICICLES Just as certain regions are especially often visited by hailstorms, definite zones exist (if from other causes), especially in the mountains, in which injuries occur almost every year due to pressure from the snow. Besides these zones, some places in all regions with an abundant snowfall must be considered as especially endangered. These are depressions in the soil into which the snow can be blown from above or from the sides. Equal amounts of snowfall act differently according to the weather. If it is very cold and windy, enough snow rarely collects on the branches to cause injury; the crystals are too fine and cold to stick to one another. If, on the other hand, the weather is warm and quiet, the snow falls in great flakes and balls easily, large masses cling in the crowns df the trees and bend or break the branches. If the trees stand on declivities, many injuries are noticed on the slope opposite the windy side; whole strips of trees can be overthrown. This occurs as a simple result of snow pressure, especially with mild winter weather and soft, open soil, while, with greater cold, the more brittle trunks will be broken (snow breakage). ‘Transplanted trees, with shallow root systems, are overturned more easily than specimens well anchored by tap roots. Evergreen trees are especially inclined to break and of them the pines seem most brittle. The tougher varieties, like firs and spruces, bend more under the burden and later right themselves. Deciduous trees are less injured if the snow masses come after the leaves have fallen. Oaks and beeches, which often retain their foliage throughout the whole winter, are more endangered than other trees, provided that a previous moist and cool summer has not prevented the latter from passing into their dormant period and dropping their foliage. Here too the brittleness of the variety is decisive for the kind of injury. The trunks and branches of older acacias almost always break. In birches and alders, also, breaking may be found oftener than bending. Bernhardt' also calls attention to the fact that the resistance of the tree variety changes according to whether its habitat is suited to its requirement or not. For our fruit trees, the shape of the crown also enters greatly into consideration; especially in apples, for with their flat, outspread branches, a true splitting of the crowns is often found. If the tree’s natural habit of growth does not form a pyramidal crown, it is advisable to cultivate artificially the development of a strong middle branch. With avalanches, occurring frequently in high mountains, the whole effect changes according to the variety of the trees and the age of the trunk. If the standing forest is old, the trees are broken at different heights and thrown together in wild and irregular disorder. Where the trees are of different ages, the young trees are only partially pressed downward and, for a time, buried in the snow. After the snow melts, these trees right 1 Waldbeschidigungen durch Wind-, Schnee-, His- und Duftbruch. Centralbl. f. d. gesamte Forstwesen 1878, p. 29. 635 themselves, or lean somewhat down hill, and slowly continue growth. Usually growing branches are found only on the side toward the valley, since the rolling snow masses have broken off those of the opposite side. In deciduous forests, deformed bushes develop, because of the tearing out of the roots or trunks; they look as if produced by the grazing of wild animals. The influence of the snow covering, and of the accompanying frosts on seeds has been mentioned already in an earlier chapter. In regard to changes in temperature in the soil, reference should be made to Wild and Wollny’. The ice-water, produced by the melting of the snow, can not be without effect, as soon as it reaches green meadows and seeded fields. Kuster*, for example, has shown that, as a result of cooling with ice-water in the chlorophyll grains of Funaria leaves, a vacuole formation is started which results in the green pigment’s lying at the edge of the vacuoles in the form of crescents. Ice coating and icicles. The injuries from ice formed on trees are: more rare. A quickly melting coating of smooth ice is usually considered non-injurious. Nevertheless, in general many growers ascribe the produc- tion of blasted specks to the deposition of ice on smooth barked branches and trunks. If, with Nouel, the production of smooth ice is considered as the solidifying of the rain drops due to the impact of striking the tree, the drops having already been cooled below zero degrees, it can be assumed that the cold of the ice acts injuriously. From the experiences collected from artificial frost experiments, I am of the opinion that the smooth ice covering can act injuriously, because of changes in tension in the ice-covered tissue. It may be proved, in very light spring frosts, that clefts arise in the bark tissue of herbaceous shoots without any extensive browning of the cell; therefore, without the chemical action of the frost having made itself felt. Such injuries to the tissues are also possible from smooth ice, if it remains for some time on the plant and especially if it outlasts the fluctuations in temperature frequently occurring with the formation of smooth ice. It is possible to distinguish from the usual formation of smooth ice, the ice and mist coverings which might be compared with snow pressure because they depend upon different processes of formation. As character- istic of the phenomenon, we will consider a description by Breitenlohner?, who made extensive observations. On January 27, 1879, precipitation began in the middle of the day, in a forest near Vienna with a complete cessation of wind and with misty weather, under an increasing air pressure and low temperature. This precipitation was half way between a drizzle and mist and soon hardened to smooth ice. A one-sided ice covering 3 to 1 Bot. Jahresber. 1898, I, p, 584-85. 2 Kuster, E., Beitrage zur Physiologie u. Pathologie der Pflanzenzelle. Z. f. allgem. Physiologie 1904, Vol. 4. 3 Breitenlohner, Der His- und Duftanhang im Wiener Walde. Forsch. auf d. Gebiete d. Agrikulturphysik 1879, p. 497. 636 5 mm. thick was produced on the trees, the temperature of which in all parts lay under zero. The period of the still frost lasted 5 to 6 days in this Viennese forest; the ice covering remained 9 days and increased until the thinnest branches grew to the size of a ship’s rope; the beech trunks broke, while the young copse wood was bent to the ground. Since only the surface of the soil was frozen, the trees were also overthrown. The needles of the conifers especially favored the formation of ice and firs became ice pyramids, since the icicles, often 20 cm. long on the upper branches, were frozen to the lower branches. In low positions, the covering was actually transparent, smooth ice; on the heights, however, the chief part consisted of a mixture of ice and mist. In the same way, the size of the ice particles decreased gradually from the edge of the forest toward the centre, where the covering was neither ice nor mist but had a firm, ray-like consistency, until finally, deep in the forest, it appeared as a typical mist covering, which became thinner and thinner the deeper one penetrated into the forest. In order to form a conception of the amount of ice thus produced, which also occurred simultaneously in Germany and France, the weight of the ice, hanging on a single branch, was determined with the following results: for the one part weight in a leafless cherry branch, the ice was 36.7 parts; in the Zerr oak, 44.1; in the red beech, 85.3; in ‘the fir, 31.1; in the spruce, 51.3; im the pine, 99.0 para: Breitenlohner, in explaining the phenomenren, calls attention to the fact that the observations of meteorological stations, at the time of the ice covering, showed the action of a south wind; therefore, a moist, warm equatorial current above a cold polar stream filled the valleys. The contact of the equatorial with the polar air waves led to the unusual form of precipi- tation. This remained fluid because the lower, cold stream of air was not very thick vertically, so that the precipitation, coming from a warm current, had to pass only a short way through cold air. Where the cold layer of air had a greater vertical thickness, the pre- cipitation took on a solid form and covered the vegetation as hoar frost. The precipitation, formed after the contact of two layers of air, which differ in temperature and moisture, can retain its consistency as fluid water even below zero degrees, since moist winds are splendid heat producers and carry an amount of latent warmth in water vapor which is freed during the continued condensation. Only when the cooling agent exceeds a certain amount is the mist changed into frost vapor and then the moisture elim- ination consists of ice needles. The peripheral trees, exposed to the free currents of air, catch and hold the mist, while, in the interior, the choked air causes the formation of the typical mist covering. This, therefore, would be analogous to hoar frost, occurring with late or early frosts, and, therefore, cannot be considered to be frozen dew. Dew is condensed water vapor, which is precipitated in drops on the parts of the plant cooled down below the condensation point of the air by radia- tion. These drops unite. Water vapor is usually abundantly present in 637 the air and, as Stockbridge’ proves, can arise as vapor during the summer months from the soil which in the night is warmer than the air. If there is a strong dew covering, it can be considered rather as a means of protec- tion against the freezing of the plants. If this dew freezes, a crystalline coating is produced which is identical with the ice covering. Hoar frost, on the other hand, is produced when the point of condensation of the air lies below zero degrees. This degree of temperature is reached through radiation and evaporation from the plant; therefore, the mist molecules attach themselves to one another in a firm crystalline form (soil or summer hoar frost). The covering of frozen mist, or winter hoar frost, is pro- duced by the flowing of the equatorial current into the slowly displaced polar current; the change is dangerous because, with longer duration, so thick a covering of frozen mist can be produced that the strongest trees break under its load. In nurseries, the prompt and careful beating of the branches with sticks will prevent such an injurious accumulation of ice. This naturally cannot be carried out in forests. In summer frosts, the cultural conditions are often of decisive signifi- cance. It should be taken into consideration, in tilled soil, that the plant body cools down more rapidly than does the soil which, in the night, acts as an equalizing source of heat and prevents, more or less, the formation of hoar frost. This effect will be the greater, the larger the water content of the soil which thus retards the cooling down. On damp fields the dew, which moderates the cooling of the leaves, is formed earlier and more abundantly than on dry soils. On the other hand, cultural regulations which prevent the rising of heat from the drier soil layers, such as the loosening of the soil, or a strawy manure, favor frost*. 1 Journal of science, Vol. I, p. 471; cit. Naturforscher 1879, Nio. 32. 2 Petit, M., Einfluss einiger Kulturverfahren auf die Bildung von Reif, Annal. agron, 1902, No. 7, cit. Centralbl. f. Agrikulturchemie 1903, p. 557. CHAP TER Xclik EX CHS» OF IEA. DEATH FROM HEAT. Supported by numerous psychological works’, we have arrived at the conclusion that, in judging injuries produced by excess of heat, the same points of view make themselves felt as in judging those due to lack of heat. In our cultivated plants we are confronted by constantly changing organizations. Not only has each species its special requirements as to the amount of heat which it can endure, but, even within a wide range of heat, the different individuals, in each species, and indeed their different develop- mental stages, behave quite differently. The individual susceptibility to a degree of heat, exceeding the optimum amount, varies according to the habitat, the supply of water and nutritive substances and the action of the other vegetative factors so that definite figures as to admissable temperature values can only have a limited validity. We see, from this, that, in our plantations, the plants can accustom themselves to higher amounts of heat up to a certain degree. Their struc- ture becomes different, their development more rapid, but their life pro- cesses, as a whole, still take place within the latitude of health. In regard to the different susceptibility of the different organs, according to their momentary developmental stage, we favor the theory that the part of the plant is the more resistant to an excess of heat, the richer the tissues are in cyptoplasm and the relatively poorer in water. Death from heat, like death from frost, is produced by the irreparable destruction of the mole- cular structure of the cytoplasmic body. We do not know in what way this takes place, nor how far a coagulation of certain protein bodies co-oper- ates in it. The more porous the cytoplasmic body is within its specific composition, due to the in-layering of abundant water, the more easily such a destruction takes place. On this account we find that organs, rich in water, die more quickly from excess of heat. Death from heat is often preceded by a “heat rigor,” from which the plants can recover, when the super-maximal temperature abates, and can begin their growth again. The 1 Pfeffer, W., Pflanzenphysiologie, 2d ed., Vol. II, Leipzig 1904. ee a a ee 639 longer the plant is Jeft in a condition of rigor, the more slowly can it take up its activity againt. We will become acquainted with other main points on the subject of difference in susceptibility in the following actual occur- rences. Poor DEVELOPMENT OF OuR WEGETABLES IN THE TROPICS. When cultivated plants from the temperate zones are carried to tropical regions very great disturbances become noticeable at times in the ontogeny of the plants, which severely impair the cultural aim. This lies in the unde- sired abbreviation of the different phases of growth, especially in the shortening of the period of leaf development, and of the production of reserve substances which are used up too early for the development of the reproductive apparatus. This is especially marked in the case of plants in which the period of growth has been prolonged by continued cultivation in soil abounding in nutritive substances, i. e., rich in nitrogen, and the leaf apparatus has been developed luxuriantly (varieties of cabbage, lettuce, etc.). We find cases of this nature reported in older works. Thus, for example, Duthie cites such a case from Saharanpur*. His experiments in India on plant structures show, with a few exceptions, a too rapid ripening of the seeds of European plants. While the beet (Beta vulgaris var. rapa) takes 18 months in England to complete its development, it needs in India only 8 months. In the cultivated forms of German asters, the effect of a change of climate manifests itself in the non-ripening of the seed. The blossoms of Brachycome and Petunia change and all become white. The process seems to me to represent the opposite of the process of the redden- ing of plant parts in spring, due to a lack of heat. Similar phenomena have been reported from tropical America. Leh- man* found in Western Colombia that cabbage, lettuce, onions and carrots did not develop sufficiently for cultural purposes. While seeds, imported from Europe, furnish in the first year, in corresponding localities, excellent, tender vegetables with a desired amount of development, seeds from these individuals give plants which, in cabbage and lettuce, show only traces of head formation while the onions grow out into stalks a finger thick without any tenderness, or flavor. The plants here have no dormant period. In the level equatorial regions this phenomenon occurs sooner and more noticeably than in the higher, mountainous regions and between the roth to 15th parallels of latitude. / POSTPONEMENT OF THE USUAL SEED TIME IN OurR LATITUDES. We must here consider the phenomenon, not infrequently observed, that vegetables, sown too late in the year, come into the hot, dry season too 1 Hilbrig, H., Uber den Hinfluss supramaximaler Temperatur auf das Wachstum der Pflanzen. Inauguraldissertation. Leipzig 1900; cit. Just, Bot. Jahresber, 1901, I pe203% 2 Gardener’s Chronicle 1881, I, p. 627. 3 Lehmann, Uber eine physiologische Erscheinung bei der Gemiisekultur im tropischen Amerika, Deutsche Giartnerzeitung 1883, p. 260. 640 soon, while still developing their vegetative organs. The leaf-body becomes hard and the tuber-like swellings soon become woody. Annual seed-bear- ing plants (grains and summer blossoms) ripen prematurely. Peas, sown too late, succumb very early to rust (Uromyces). Kraus! has already advanced the theory that the turgidity of the tissue decreases with too high temperatures. Haberlandt, in his experimental plants, has found a splendid example of the influence of drought in fungous attacks on plants. Of three pots sown with wheat and left standing side by side during the whole period of growth, the one where the plants were watered only enough to keep up life, were so attacked by mildew (Erysiphe graminis) that the greater part, at any rate, of the blame for the whole failure of the harvest must be ascribed to the fungus. The pot, standing nearby and abundantly watered, was almost entirely shunned by the parasite®. Still more decisive is the case which I observed with Podosphaera leucotricha Salm. Walf of a number of young apple trees in pots stood in a conservatory, the cther half out of doors back of this conservatory. All the specimens had retained through- out the winter the didia form from the previous year. The trees in the conservatory exposed, without any protection, to the summer heat were twisted out of the shape from the extensive spread of the mildew, which developed to the perithecial fruiting stage. Those standing back of the conservatories, in half shade and in moving air, lost the mildew. Hell- riegel’s* experiments prove how much the production of plants suffers from a wrong time of sowing, even without the action of parasitic enemies. Barley sown in April, May, June, August and September in pots with the same mixture of nutritive substances and soil moisture, under otherwise entirely similar conditions, behaved absolutely differently. That sown in April developed very regularly grown, excellent plants, bearing ripe seeds at the end of 88 days. The seed sown at the end of May grew into plants which, at first, also developed very vigorously, but as a long period of heat occurred toward the middle of July, at the time the heads push out from the upper leaf sheath the stalk was retarded in its growth in length. Up to the premature death of the plants (after 77 days) the kernels had matured only incompletely and remained flat; they, therefore, had become ripe pre- maturely. The latter sowings showed an increasing lengthening of the period of growth (the September seed, for example, required 240 days) and resulted in quite incompletely ripened grain. In regard to forest plantations, experience also shows that the losses from transplanting of young forest trees vary according to the time it takes place. Experiments in Mariabrunn‘ gave the smallest loss in spring trans- planting. For spruce trees the number of dying examples of an April to June planting increases only to decrease again in autumn transplanting Molekularkonstitution des Protoplasms. Flora 1877, p. 534. Biedermann’s Centralbl. 1875, II, p. 402. Grundlagen des Ackerbaues 1883, p. 352. Deutsche Forstzeitung November 13, 1892. mo tH 641 (September and October). The same behavior was shown in the case of the pine, which gave a still more significant percentage of loss. In decidu- ous trees, as is well known, autumn transplantation is preferred. SUNBURN OF LEAVES IN NATURE. The death of the tissue, resulting from the action of the sun, is here meant. In such cases, however, light and warmth act together. We do not know how much must be ascribed to each factor in such phenomena of death. The opinion of noted foresters, that all the light in the plant cell passes over into the dynamic force of heat and becomes effective in this form, is not very probable. My evaporation experiments with a decrease of light, and a simultaneous increase in temperature, indicate rather that at least a part of the light, as such, becomes effective, and influences the process of assimilation. A part without doubt is converted into heat and acts in that way. Upon this hypothesis, it is also probable that a plant would behave differently with the same amount of heat, according to whether it is subjected to this in a dark, or in a lighted place. In general, temperatures between 40 to 50 degrees C. are fatal; yet Askenasy! has observed, with Crassulae, that they can endure uninjured such amounts of heat. Askenasy was convinced in midsummer that the inner parts of Sempervivum, at an atmospheric temperature of 31 degrees C. in the shade, had undergone a heating up to 48 to 51 degrees C. The warmth within the plants seemed higher in some varieties, lower in others, than on their outer surfaces. The temperature of the outer surface of the leaf, in different days, did not stand in any direct relation to the atmospheric temperature. Sempervivum arenarium showed, for example, at 31.0 degrees C. on the 15th of July, at 3:00 P. M., 48.7 degrees C. Upped 2 ap “ce cé ce T6th a3 “ec cs 3 -00 P. Ie 4O. O “cc ce 23.1 ce ce é ‘ec T8th ce ce (a9 T2 :20 P. M., 49. O 6e 6é Thin-leaved plants, standing nearby, had a much lower temperature. The phenomena of sunburn are observed most frequently in hot-house plants which, in spring, are set out of doors. The leaf is not always killed but often only reddened or browned. In curled leaves only the convexity, on the upper side, becomes colored and, instead of being green, is reddened to a copper color (roses). In the course of a few weeks such a plant can recover even when left in this place. | I tested experimentally a similar case in spotted specimens of Canna indica, the greatest number of which in cloudy weather were taken from the hot house, in which they had been forced up to the unfolding of the first blossoms, and were set out of doors. Some pots stayed two days longer in the hot house and were then sunk in the earth in the middle of the day beside the specimens set out earlier. In the afternoon the upper leaves 1 Askenasy, Uber die Temperatur, welche Pflanzen im Sonnenlichte annehmen. Bot. Zeit. 1875, p. 441. 642 appeared striped with white, since the parts of each intercostal field farthest from the ribs, conducting water, showed dead tissue., The white stripes were broadest at the edge of the leaf and dwindled gradually toward the midrib so that it was clearly evident that the burning of the leaf occurred earliest and strongest in those regions which lay farthest away from the water conducting system of the large vascular bundles. The epidermis did not seem essentially changed in the white places, but the palisade parenchyma which no longer had chloroplasts was greatly changed, while a transitional zone toward the healthy tissue, provided with large chlorophyll bodies arranged along the walls, showed a content still green but cloudy. In tissue, which had become white, the cell walls of which had remained clear, glycerin contracted only a small amount of the contents so that it was necessary to conclude that in this short time a large part of the contents had been used up in respiration. In the places most greatly injured, the epidermis was raised here and there, like blisters. from the flesh of the leaf (burn blisters) and the destruction of the chlorophyll had extended even to the under side of the leaf. After some weeks it was possible to observe a regeneration of the chloroplasts in the burned leaves in the above-mentioned transitional zones. Thus, a healing process had taken place exactly as after slight injuries from frost. The presence of mycelium could now be demonstrated beneath the burn blisters in which part of the epidermal cells seemed to have collapsed. Rowlee' observed a collapse of the epidermal cells even after an 8 hour exposure to electric arc light which acted on the leaves of heliotrope at a distance of one metre; other plants (for example Ficus elastica). under similar conditions, remained unchanged. In fleshy, long-lived leaves, the healthy tissue is separated from the burned tissue by a cork zone, as is shown in the subjoined illustration of a Clivia leaf injured in August from sunburn. It is easy to observe that the position of the leaf determines the place of production of the burned spot, since only those places, perpendicular to the source of heat, turned a yellow- ish gray and collapsed. On the following day the burned spot was per- fectly brown and brittle. The youngest leaves were uninjured. The boundary between dead and living tissue becomes sharp, as soon as the burned spot extends through the whole thickness of the leaf. If, however, only the upper side of the leaf is injured, a faded, transitional zone is found. In this, the chloroplasts turn the color of verdigris, while the remaining cell contents show a yellow green. Therefore, there may occur here first of all the disappearance of the xanthophyll, while the cyanophyll remains com- bined in the chloroplasts. Thus, the contours of the mass of chlorophyll grains, which at first refracted the light equally strongly, become less sharp and a large amount of very fine granules give it a sandy consistency. 1 Rowlee, W., Effect of electric light upon the tissues of leaves. Just’s bot. Jahresber, 1900. II, p. 287. 643 Finally, the chloroplasts form groups, a dirty tea-green to a blackish green in color, which assume a cord-like form because the cell collapses. These content masses, which lie against a wall, bleach very quickly in sunshine and cause the yellowish gray color of the burned place. The cell walls do not lose their cellulose character, as is proved by testing them with chlor zine iodide. é The healthy tissue begins at once to cut itself off from the injured tissue by a cork zone (k) whereby the cells of the transitional zone (br), which have remained rich in contents, at first somewhat enlarged by an undulation of their walls (A, 2), show enlarged intercellular spaces and gradually die. When the burned spot becomes somewhat older, it turns a deeper brown, in which the epidermal cells, which have not collapsed (e), partici- pate even up to the healthy tissue. The cork zone (k) is produced by a IF y . pte x oy aca cataty AED DICTED HE BUTS 5 eLT } SesugC ape ie ; ees Fig. 151. Cross-section through a sunburn spot in a leaf of Clivia nobilis. division and elongation of the mesophyll cells which have remained alive at the edge of the burned place. The normal cells, back of these (pf) usually remain somewhat poorer in chlorophyll. The callous appearance of the peripheral zone (w) of the normal leaf part at the edge of the burned place should be noted; this is explained by the distention of the cells, which develop the cork zone, and of the mesophyll (/) lying in front of them, which had been injured but did not die at once. SUNBURN Spots IN CONSERVATORIES. Complaints of the occurrence of burned spots on the leaves of tender plants in conservatories abound, especially in spring, and opinions as to their production differ greatly. Sometimes bubbles in the glass are held responsible for this. Sometimes, it is: thought that the drops of water, which remain on the upper surface of the leaf after the plants are sprinkled, act as burning glasses or become so warm from the sunshine that they injure 644 the tissue. Jonsson’st experiments have proved that the bubbles in the glass are actually the cause. He observed the light image of the sun’s rays produced on the leaf by such bubbles and the changed position of such spots resulting from the change of the sun’s position. This explains also the not infrequently observable phenomenon that such burned spots appear in regular lines. One experiment proved, however, that sprinkling can also act danger- ously, when a drop of water remained hanging on the under side of the cover glass, fastened at some distance above the surface of the leaf. In this, traces of burned spots could be produced, while drops of water lying directly on the leaf caused no injury. To avoid such disadvantages, it would be advisable in general practice to choose better grades of glass at least for those hot houses in which valu- able foliage plants are kept. DEFOLIATION, Phenomena of scorching are not here concerned but rather the precipi- tous maturity of the tissues. In cases observable out of doors, a great dryness of the soil is usually combined with the direct action of the sun. Special experiments with burning glasses show, however, that even in damp soil the leaves are thrown off which are most strongly injured by burned spots. Wiesner? found that, in “the falling of leaves due to heat,” those which usually fall come from the inner part of the crown of the tree, rather than from its periphery. He thinks that these outer leaves, as a result of their greater radiation of heat, do not become so warm as the leaves found in the enclosed places. We might seek the reason for this in the different vitality of the organs. Those exposed to the greater amount of light produce more substance and their cells are richer in cytoplasmic material. They have, therefore, with an abnormally increased evaporation and respiration, more reserve substances and are longer lived than leaves of the same period found in the inner part of the tree crown. Young organs in themselves are more resistant. In cases occurring out of doors, the place of growth, together with the water supply, acts decisively. Among forest trees, this is seen best in oaks and larches in young plantations where individual specimens, already show- ing completely dried bunches of leaves, are always to be found between green trees which have been uninjured, or only slightly changed. In one young larch plantation, I found that the specimens most greatly injured had lost almost all their needles from the upper branches. Only the very young shoots, the tips of which seemed twisted and a fox red, still held needles which hung downward like red tassels. The youngest needles of all 1 Joénsson, Bengt, Om Brannflakar pa vaxtblad. Botaniska Notiser 1891. Zeitschr, f. Pflanzenkrankh. 1892, p. 358. 2 Wiesner, Jul., Uber den Hitzelaubfall. Ber. d. D. Bot. Ges. 1904, Vol. DO. p. 501. 645 seemed faded, flattened and papery dry. Their extremely scanty cell con- tents formed a colorless ball, lying free in the inner part of the cell and turning yellow with iodine. In the older needles, the cell walls of which had remained perfectly colorless, the abundant cell contents appeared in the form of pale grayish red, or yellowish brown, uniform masses lying against the wall. The appearance resembled that produced under the influence of acid gases. In spruces too the discoloration of the needles, produced by intense summer drought, is very similar to that produced by sulfurous acid. A similar dropping of the leaves, due to heat and drought, may also occur not infrequently in other conifers, especially when suddenly left standing alone. My experiments with spruces showed, in regard to the process of dropping needles, that when the rays from a lens were focussed at the base of the needles, these could be loosened at once with a slight pres- sure even if they showed no discoloration. When the needles were injured at points higher up they remained attached. In the burned places the cell contents had contracted into a band-like, green to brownish-green mass in the centre of the cell, and even their granular structure could still be per- ceived. The contracted content masses lay usually in the same position in the different cells, i. e., in the direction of the long diameter of the needle. Injuries to the bud from sunburn are comparatively rare. This is to be attributed, in part, to the protection of the covering of the buds by a hairy felt, gum, resin, cork layers, or the like, which often are found to be espe- cially effective; in part, also to the abundant cytoplasmic contents of the young tissue which, therefore, are changed with greater difficulty. In the tropics, special protective precautions may often be found. According to Potter’, for example, in Artecarpus, Heptapleurum, Canarium ceylanicum, and others, the stipules of the older leaf organs serve as a protection for the young leaves until they become strong, or the entire old leaf at first forms a protective covering for the young one (Uvaria purpurea, Gos- sypium, etc.) In peach forcing in England, a dropping of the peach buds has been observed. In places, where a damp cloth was stretched over the plants as a protection against the action of the sun, no dropping of the buds was found’. SUNBURN IN BLOSSOMS AND FRUITS. In injuries to blossoms, no absolutely high degree of temperature is necessary; even the usual temperatures can become injurious for shade loving plants in an unfavorable place of growth. The tuberous Begonias form the best known example, the blossom edges of which easily become brown, if the plants cannot benefit from the evaporation from moist soil. An unusual excess of heat affects fruit in two ways. On the one hand, it produces premature ripening, i. e., the appearance of the processes 1 Potter, M. C., Observations on the Protection of Buds in the Tropics. Journ. Linn. Soc. XXVIII, 1891, p. 343. 2 Gardener’s Chronicle 1893, XIII, p. 693. 646 of ripening at a time when the fruit should really be storing up reserve substances. The result is that the cells of the fruit flesh, insufficiently filled with reserve substances, end their life prematurely, resulting in a specked condition and premature decay when stored. In grains, a premature ripening of the blades causes a distinct injury to the kernel from an insuffi- cient formation of starch’. The other form of injury consists in the direct killing of the tissues, by sunburn, on the exposed places of juicy fruits. Such burned spots fre- quently resemble places injured by hail because the killed tissue cannot stretch proportionately during the process of swelling of the fruit and therefore tears. In the increasing cultivation of the tomato, we now find abundant examples which remain unrecognized only because fungi usually infest the burned places of the fruit. The cases are then described as parasitic diseases. INJURY TO GRAPES FROM SUNBURN. This is of great agricultural significance. According to Miiller- Thurgau’s observations? an injury to grapes will be observed when hot, clear, sunny days occur suddenly after a longer period of cold, damp weather. It is found then, almost as a rule, that the berries of the free hanging clusters, exposed to the direct rays of the sun, lose their green color, become pale, then turn brown and finally shrivel. The stem of the cluster also begins to suffer where it is directly touched by the sun’s rays. The berries, hanging to it, shrivel but, in this case, do not lose their green color. In the blue varieties, the berries, which come in contact with the sun’s rays, remain green, becoming darker than those of the white varieties and turn almost black. In some years, whole bunches are found shrivelled up like raisins, producing in places a considerable injury*. That it is actually an excess of the heat which kills the berries in this case is shown by the fact that grapes, which were warmed in a tin case to 50 degrees C., took on exactly the same appearance as specimens attacked by sunburn out of doors. The state of ripeness, as well as the water content of the organs, and also the humidity of the surrounding air, exercises a decisive influence on the burning. Unripe Riesling and Sylvaner berries were not injured when warmed to 42 degrees C. for two hours but were injured at 44 degrees C. after an equal length of time. Direct measurements showed that the berries, on which the sun shone, were warmer than the surrounding air. While a thermometer in the air showed 24 degrees C. in the shade and another 36 degrees C. in the sun, the temperature in the grapes, exposed to the sun, increased to 40 degrees C. It was found further that Riesling grapes from good warm positions were poorer in water and suffered less from sunburn, than those from 1 Déhérain et Dupont, Uber den Ursprung der Starke des Weizenkorns; cit. Biedermann’s Centralbl. 1902, p. 324. 2 Der Weinbau 1883, No. 35. 3 Jahresber, d. Sonderaussch, f. Pflanzenschutz 1892. Arb. d. D. Landw. G. 647 inferior vineyards. Besides the small water content, the advanced ripeness of the berries is a condition which acts as a protection against sunburn. The early Malinger and the early Burgundy, which ripen even in the middle of August, for example, showed no injury whatever from the hot August sun while more than 50 different varieties of grapes, standing close by, which ripened later and therefore were still hard and green in August, had suffered more or less. Measurements of the temperature in green, unripe, hard berries of Riesling, -Sylvaner, Elbling and late Burgundy showed injury at 43 degrees C., while the fairly ripe berries of the early Malinger and early Burgundy could be warmed for some time up to 55 degrees C. without injury and the flesh of the Malinger grapes was killed only at a temperature somewhat above 62 degrees C. The discovery by practical workers that sunburn is found most fre- quently when wet, cold weather precedes hot days, is explained, on the one hand, by the greater water content of the berries and, on the other, by a lesser evaporation and, consequently, a lesser cooling when the air is moist. In regard to the influence of drought, Muller made an experiment on two Riesling grapes, one of which was placed in a glass vessel lined with moist blotting paper, the other in one containing some calcium chlorid, and both placed in a tin case which could be heated. The grapes in moist air were completely killed at a temperature of 41.5 degrees C., while those in the air, dried by the calcium chlorid, were scarcely injured. Two thermometers, one of which hung free while the bulb of the other was stuck into a grape berry, were put in a similar tin case, and warmed up to 40 degrees C. The thermometer, covered by the grape, constantly stood approximately 4 de- grees lower than the other when the temperature increased slowly as well as when it decreased. This may well be conditioned only by the evapora- tion of the grape. , The phenomenon of Seed cracking can set in as the result of sunburn. Since, however, different causes of this phenomenon exist, it would be better to consider it later by itself. At times so called “rusty grapes’ are found, i. e., those of which the skin has formed fine cork lamellae. This has been thought to be a protec- tive means against sunburn’. Protection of the grapes by the leaves is the best precautionary method and it is wrong to think grapes are helped by the removal of their foliage. SUN CRACKS. In forest and other trees, at times in spring, the bark cracks. This phenomenon has been named Sun cracks by de Jonghe, while Caspary? considers them due to the action of frost. Surface dying of the bark is distinguished, as sunburn, from simple torn wounds. Illustrations are found 1 Zeitschr. f. Pflanzenkrankh. 1902, p. 111. : 2 Bot. Zeit. 1857, No. 10; “Bewirkt die Sonne Risse in Rinde und Holz der Baume?” ; 648 in R. Hartigt and Nordling?. The latter distinguishes still another “winter sunburn’”’® in which the injury to the trunk is found only at its base. The reflection of the sun’s rays from the upper surface of the soil is assumed to be the cause. R. Hartig’s illustration shows the lower end of the trunk of a red beech sapling with sun cracks*. Since these phenomena, as yet, have only been observed in the late winter and strict experimental proofs are still lacking, we maintain the opinion expressed earlier that the cracks are pro- duced by differences in tension which arise with a sudden sharp change in temperature without the necessity of a warming of the tissue from the sun until it dies, as is the case in sunburned places. Hartig’s* measurements of a spruce in August show how much the parts of the plants are warmed above the temperature of the air. With an air temperature of 37 degrees C. he found 55 degrees C. in the cambial region of the southwest side; only 45 degrees C. on the south side; 39 degrees C. on the east side; 37 degrees C. on the north side. The measurements were made in the afternoon after 4 o'clock. INFLUENCE OF Too GREAT Sort HEArT. Sachs® has already furnished abundant material in regard to the deter- mination of the temperature requirements of different plants and especially with respect to the germination of seeds which had been exposed to a high temperature of air and water. In the latter connection it is evident that dry seeds endure a higher temperature without being injured than those already sprouted and that probably all plant tissue (within boundaries required by the species) is in every case the more resistant to heat the less the water content of the cells is proved to be. Corroborative works have been furnished by Haberlandt, Wiesner, Fiedler, Krasan, Just, Nobbe, Hoehnel and recent authors, in regard to which reference must be made to Pfeffer’s Physiology. Just’s’ experiments show, for example, that unfavorable results may be experienced when, in germinating seed, the temperature is increased above the optimum given for any special variety. He found in these ex- periments, that a prolongation of the germinating time and a slower devel- opment of the seedling is produced by too high temperatures, just as in seeds which are too old. Prillieux’s* older work is of importance in regard to the anatomical changes. In bean and pumpkin seeds, sown in pots in which a high soil temperature was maintained by heated wires, the following results were. found: the young seedlings grew but little and with difficulty; however, 1 Lehrbuch der Baumkrankheiten, 1st ed., p. 188. 2 Lehrbuch des Forstschutzes, 1884, p. 332. 3 Baumphysiologische Bedeutung des kalten Winters 1879-80; cit. Tllustrierte Gartenzeitung 1881. 4 Lehrbuch der Pflanzenkrankheiten, 3d ed. 1900, p. 230. 5 Ibid., p. 228. 6 Experimental-Physiologie, p. 64 ff. 7 Cohn’s Beitrage zur Biologie der Pflanzen. Vol. II, p. 311. 8 Prillieux, Altérations produites dans les plantes par la culture dans un sol surchauffé. Ann. sc. nat. Ser, VI Botanique, t. X, p. 347. 649 they looked swollen; in the places where the swelling of the little stems was most intensive, gaping, usually horizontal wounds were found which ex- tended to the pith. In contrast to normal plants of the same age, those of the over-heated soil were only half as long but approximately three to four times as thick in diameter at the place of the greatest swelling. Here too the epidermal cells were two to three times as broad as in normal plants. The stomata showed the same difference only to a slighter degree. The hairs were not changed. The bark parenchyma was, to be sure, four times as thick but no cell increase had taken place; the cells of the pith paren- chyma showed still greater radial distention; but actual cell increase could be proved only in the bast parenchyma. Prillieux cites further that the nuclei behave similarly. They hypertrophy and increase in such a way that even three or four may be found in a single cell. Nuclear division takes place by fragmentation. Such a cell increase is perceived also in the short, curved and twisted, but not swollen, roots of the changed plants. The large, deformed nuclei show usually very irregular nucleoli, occurring more than one in a cell, in which, not infrequently, vacuoles appear when colored black with osmic acid. In fragmentation of the nuclei, first a fold usually ap- pears at one side and seems to constrict the nucleus. Later a cytoplasmic wall is formed between the two resulting nuclei. The two halves, thus produced, become inflated and tend to separate, which separation, however, does not always actually become complete. It also seems that this cleavage of the nucleus takes place within an already existing cytoplasmic covering, belonging to the original nucleus, which does not rupture until later. This increase of the nuclei and the tender bast element may indeed indicate the way in which a higher soil temperature, which approximates the optimum, can act favorably. Cell increase and the conducting of the plastic material may be hastened. As is well known, horticulture makes good use of the beneficial influence of the higher soil temperature by means of hotbeds. Yet just here the observation may be made, that a too high soil temperature is not favorable for the many plants from a cooler climate. They do not grow more rapidly but easily decay. The assimilatory energy slackens and the weakened organism is attacked by bacteria and fungi. Hellriegel’s experiments! show how much assimilation falls when the soil temperature becomes too high. Comparative cultures in roasted quartz sand gave yields for rye at 8° 10° 15° 20° 25° 80° 40° C. constant soil temperature Fresh weight .... 191.5 176.3 269.4 456.6 376.0 408.0 240.1 Dry substance .. 238.9 22.8 32.4 49.5 42.4 47.0 31.2 wheat Fresh weight .... 98.6 130.8 241.0 260.5 342.0 402.2 296.0 Dry substance .. 15.8 20.8 29.5 30.8 43.9 46.9 40.3 barley Fresh weight .... 151.9 156.0 383.4 408.5 435.2 365.0 230.5 Dry substance .. .17.1 18.0 34.4 36.7 420 35.0 26.3 1 Beitr. zu den naturwissenschaftlichen Grundlagen des Ackerbaues. Braun- schweig 1883. Vieweg & Sohn. 650 The results refer to young plants and show clearly how the production falls off toward an upper and lower limit starting from an optimum tem- perature for the roots. At the same time the figures also throw light upon the difference in the warmth needed by the different species. Wheat (at least when young) requires the highest soil temperature. Wheat developed the most energetic assimilatory activity at 30 degrees soil temperature, while rye developed best at 20 degrees and barley at 25 degrees C. Also in this young stage, when adjustment to conditions is easiest, the plants clearly show the disturbing influence of too high a soil temperature. Aside from the retardation of germination, a considerable difference was shown in the habit of growth of the seedlings in that their stems and leaves at high temperatures became thin and delicate while, at lower soil tempera- tures, the specimens appeared short, thick and more fleshy. The experiments by v. Bialoblockit gave the same results and showed also considerable differences in the formation of the root system. The barley plants, which were kept growing constantly at ro degrees C., soil temperature, had formed their roots from a few large, strikingly strong, splendidly white branches of the primary and secondary series, of which the latter were unusually short and covered with small, wart-like protuberances (latent eyes of the tertiary series). The individuals, standing in the soil at 30 degrees C., constant temperature, had developed unusual, richly ramified brown root fibres, as thin as threads, which had become matted to a thick felt. At 40 degrees C. the character of the root ball was the same but its extent was very small; a small felt was formed in the upper soil layers. Tolsky? also found in oats a stronger development of the individual roots at a lower temperature and recently Kossowitsch* confirmed these results. The rate of penetration of the oats roots into the soil was retarded thereby. A soil layer of about 30 cm., at the increased temperature, was penetrated 14 days after seeding but, at the lower temperature, only after 30 days. Also in other experimental plants (mustard and flax) the weight of the air dried roots was the greatest at a low temperature. The amount of evaporation of plants grown under such conditions was less than for speci- mens of similar development which had grown at the normal, or higher temperature. FAILURE OF THE PINEAPPLE. The fact, that pineapples grown in European conservatories surpass imported fruit, because of increased flavor, has extended their cultivation in private gardens in some regions (for example, Silicia). The greatest danger in their cultivation lies in their “Durchtreiben,” i. e., a continued leaf growth at a time when the plant should enter its rest period in order 1 Landwirtschaftliche Versuchsstationen 1871, Vol. XIII, p. 424. 2 Journ, f. experim. Landwirtschaft, 1901, p. 730. 8 Kossowitsch, P., Die Entwickelung der Wurzeln in Abhingigkeit von der Bodentemperatur in der ersten Wachstumsperiode der Pflanzen. Journ. f. experim, Landw. 1908; cit. Centralbl. f. Agrkulturchemie 1904, p. 451. 651 to set fruit. The cause lies in the untimely supply of heat and water during the rest period of the plant, which needs three years for its development. After the plants from the sprouts (suckers) of already fruited plants have grown for two years in hot beds, they are planted in the autumn of the third year in beds close under the glass of greenhouses which are built flat purposely for pineapple growing. These beds are kept at a high soil tem- perature by bottom heat. When the plants are well rooted at a temperature which should lie between 25 to 27 degrees C. the heat must be decreased at least 10 to 12 degrees C. and a marked, dry period begin. Only if the plants have thus been given a complete rest, may the forcing begin again in February, when the former degree of heat in the soil is allowed to act again on the plants and the soil very soon well watered with warm water. If, after 4 to 6 weeks, the leaves of the plants begin to spread out and to become colored at the heart, it may be concluded that the fruit is setting. For fear that the decrease of temperature may injure the pineapple the moisture and heat are often not sufficiently reduced and the result is a continued growth of the plant with the exclusive production of leaves. According to reports made by Cousins’ the same phenomena appear in the cultivation of the pineapple in the tropics. THE GLASSINESS OF ORCHIDS. Two cases may be briefly mentioned here in which plants of Oncidium developed young shoots, nearly all of which showed a glassy, translucent consistency. A few days after the appearance of the glassy places, at the base of the bulbs, the shoots fell over and decayed. Since parasites could not be found in the initial stages of the disease and the slenderness of the older shoots indicated great heat and moisture, the plants, without any further treatment, were brought into a cooler, brighter conservatory. After a few weeks, the phenomenon had disappeared. FAILURE IN ForcinGc BLossom BULBs. Often, after very hot summers, gardeners complain that, contrary to all expectations, the blossom bulbs develop poorly; that, when the usual tem- perature was used, the blossoms pushed unsatisfactorily out of the bulbs and these began to decay. Bulbs set out later than usual for forcing and cultivated with less heat, however, gave perfect blossoms. From the different cases with which I have become familiar, I have formed the following theory: if a period of warm weather occurs in the early summer, when the bulb fields are in the midst of their most vigorous development, the foliage is killed prematurely by heat and the bulb becomes ripe prematurely. Under such circumstances, the material which later, in forcing, should furnish the starch dissolving enzymes, seems to be formed in insufficient amounts. If, in forcing the bulbs in winter, the usual high 1 Revue cult. colon. 1902, No. 92. 652 temperature is made use of at the customary time, the stimulus of the heat for these prematurely ripened bulbs is too great, since they require a slower, more gradual sprouting with lower temperature. If this requirement is not taken into consideration, the reserve substances are not used, as normally, in nourishing the inflorescence and the bulbs decay. Another case in which similarly. the usual forcing method fails, be- cause the temperature usually found to be best proves to be too high, is seen in the “falling over of tulips.” In certain early varieties (pink blooming), it has been observed that the peduncles break over before the blossoms open. A glassy spot 1 to 2cm. long, appears below the node out of which leaves spring in these varieties (several centimeters above the neck of the bulb). The gradual shrivelling of this spot causes the breaking over of the stem. Investigation proved an abundance of starch throughout the whole bulb body along with an unusual amount of peroxydases. In forcing, it was found, however, that with a high increase of temperature, the starch was insufficiently dissolved, i. e., too little constructive material was sup- plied to those forced aérial parts. The medullary tissue of the stalk, poor in contents, was torn at this glassy place, because of the rapid elongation, thus destroying the rigidity of the stalk. Bulbs, from the same shipment, which were set out some weeks later, i. e., nearer their natural time of developing and in the same temperature, developed normally. It is thus seen how the same temperature in the conservatory can act favorably at one time, unfavorably at another, according to the weather of the previous year and the constitution of the bulbs, and it is advisable at the beginning of the time of forcing to make some preliminary tests. In lilies of the valley, the same circumstance of unusually rich starch production with an insufficient supply of starch dissolving enzymes mani- fests itself in the scanty development of the blossom sprays. At first only a few of the lowest blossoms of the sprays develop and only after these have withered do the upper bells open. For this reason, forced lilies of the valley often become unsalable as market plants. For such cases the process used by Garden Inspector Weber’ of Spindlersfeld can be recom- mended. He watered the pips with water at 44 degrees C. before planting. At any rate, the dissolving of the reserve substances was hastened by this. It is evident from these examples that the dormant plant parts must have reached a definite condition of maturity for success in forcing, which condition is characterized by a sufficient supply of starch dissolving enzymes. SEED WHicH Has SUFFERED FRoM SELF HEATING. Without going into the much mooted question whether the self-heating of unripe seed, or of seed stored in a moist condition, takes place from the effects of oxydases, or from micro-organisms, as in hay’, or from both 1 “Gartenflora,” Berlin, 1907, Part 2, p. 26. 2 Miehe, H., Uber die Selbsterhitzung des Heues. Arb, d. Deutsch. Landw. Ges. Part 111, 1905, p. 76. 653 processes, we will consider here only the utilitarian value of the heated seed. We will mention, as example, an observation made by Bolley', who found in overheated wheat, stack-burned as well as bin-burned, that the embryo was browned, or entirely killed. If the grains develop at all, the tips of the leaves usually die and the roots have no hair covering. The injured grains have lost their clear color and appear pale or browned. The testa is pale and wrinkled ; the flavor of the grain, as a rule, is sweetish and the germin- ating power, even in grain which looks good, is weakened. The injury to the germinating power takes place so much the more rapidly the less ripened the seed was when stored or the less draughty the place of storage, since wind can dissipate the water vapor. According to Jodin’s experiments? the use of a drying substance (slacked lime) has proved to be advantageous. 1 Bolley, H. L., Conditions affecting the value of wheat for seed. Agric. Exp. Sta. North Dakota; cit. Zeitschr. f. Pflanzenkrankh. 1894, p. 22. 2 Jodin, V., Sur la resistance des graines aux temperatures élevées. Compt. rend, 1899; cit. Bot. Jahresber. 1900. Il, p. 420. CEA ER TE LACK OP LIGHT: ETIOLATION. The disease, which is produced by deficient illumination, or entire lack of light, is called etiolation (étiolement). The different stem members in ihe majority of green plants become uncommonly long and weak. Accord- ing to the variety to which they belong, the leaves, as well as the internodes of the stem, either become very long, slender and limp (the majority of monocotyledons), or develop only very slightly and remain, for their whole life, in a condition similar to that in the bud (most dicotyledons). A bleaching of the green parts of the plants, i. e., an arrested develop- ment, or decay of the existing chloroplasts, is connected with this change in form. We find exceptions only in the gymnosperms, of which the major- ity are unusually little susceptible to the removal of light. At any rate, according to Burgerstein’ the absorption of the endosperm becomes slower, the epinastic spread of the cotyledons less energetic and incomplete than in the light, but—with the exception of Gingko biloba and Ephedra—the seed- lings did turn green. Cycas and Zamia, on the other hand, cannot form any chlorophyll in complete darkness, even with a favorable temperature. Among conifers, the larches need the light most since they become only slightly green when it is excluded, while the Cupressineae become com- pletely green. The difference in the formation of the leaves of etiolated plants is explained by the fact that the leaf, for the most part, must nourish itself and that the cellulose material, which it needs for the new formation and maturing of the leaf cells, can be formed only by the action of the light on the very spot. If the nutriment is suppressed, the leaf cells, already formed in the bud, elongate with the absorption of water, on which account the leaf itself will become somewhat larger, but all further growth, depending on cell increase, will be impossible. The more the leaf, in its later enlarge- ment in the light, depends on cell increase, the smaller it remains when the 1 Burgerstein, A., Uber das Verhalten der Gymnospermen-Keimlinge im Lichte und im Dunkeln. Just’s bot. Jahresb. 1900, II, p. 250. 655 light is shut away. Further, it will develop so much the less, the fewer the cells originally formed as leaf primordia at the tip of the stem; a clasping leaf, on this account, will develop further than a whirl leaf can, because, in the primordia of the former, the whole circumference of the stem is active, while in those of the latter, the cells at the same height on the stem must be divided among as many leaves as the whirl numbers. A further point, which must be of influence on the development of the leaf in the dark, is the distance of the leaf primordia from the source of the reserve substances. Those produced first, and lying nearest a reserve substance store, remove more material from the supply and, on this account, become larger than those produced later and higher up on the etiolated stem. Thus the development of the etiolated leaf is dependent on the individual primordia and on the amount of nutrition to be found in its immediate proximity. _ The primordia of the monocotyledon leaves, in the majority of cases, are formed like a roll, surrounding the stem, below the vegetative cone and in the immediate proximity to reserve substance stores, when these are present, from which the dissolved constructive material has to pass only a short distance through the shortened axis (grasses). Having discussed the etiolation phenomena of the leaf, the unusual elongation of the etiolated stem members remains to be explained. We will follow in this the statement made by Kraus’. Asa rule, etiolated stems are thinner than normal ones, caused by a lesser number of cells, and this deficient activity in the cambium of the stem is explained by the assumption that some of the nutritive substances, worked up by the leaf, which pass over into the stem through the petiole, pass further in a radial direction and help to nourish the cambium of the internode of the stem. If this source of nutrition fails, i. e., the leaf, which in the dark remains in the form of a scale, is not in a position to obtain material for cell increase, the stem mem- ber remains as it is without any actually new cell formation. The thicken- ing of the cell walls is also suppressed. In normal stems the parenchyma cells of the bark and the prosenchyma cells of the wood become thickened during their growth in length. The pith cells, however, begin to grow thicker only when elongation is approximately at an end, i. e., at the latest moment, since they are only reached by the cellulose micella, wandering in a radial direction from the leaf into the interior of the stem, when it is no longer used to thicken the wood or bark cells. In etiolated stems, because of the lack of nutrition, the thickening of the cell is only indicated, so that it is almost lost in those which lie between the different vascular bundles and, in the normal condition, develop into wood cells. On this account, frequently no closed wood ring is found in the etiolated plants. The loss in thickness suffered by these cells is compensated for by their greater length, which exceeds that of the normal cell from two to four times. 1 Kraus, C., Uber die Ursachen d, Formveriinderungen etiolierender Pflanzen, Pringsheim’s Jahrb. f. wiss. Bot., Vol. VII, Part 1, 2, p. 209 ff, 656 This excessive length is explained by the modified tension conditions in the stem members. The bark, if loosened from the growing part of the stem, contracts ; the isolated pith body, on the other hand, becomes considerably longer. It is evident from this that, in the stem, the pith is really the elongating factor, while the rest of the tissue represents the restraining factor. Only when the stem is still very young can the pith satisfy the impulse for elongation because the surrounding tissues are still thin-walled and very easily stretched. They can, therefore, most easily follow passively the strain which the pith exercises. Gradually, however, the elasticity of the outer tissue is entirely lost and the longer pith is now restrained by the thick- walled bark and wood elements. In the latter developmental stage, shortly before the stem member ceases growing, the differences in the tissue are equalized, for now the pith cells grow broader rather than longer, as a result of the restraining influence of the bark layers and, in this form, become stable since the porous thickening layers are now formed in the cell wall. Therefore, the longer the bark elements remain elastic, so much the longer can the pith follow its impulse to elongate and draw the other tissues out with it. The etiolating plants often resemble juvenile organs and the condition of etiolation, up to a certain degree, can be designated as a permanent juven- ile form. After discussing the morphological changes, we have still to consider some metabolistic processes. First of all we will mention the investiga- tions of E. Schulze and N. Castoro? on Lupinus albus. In etiolated seed- lings, the protein content decreases constantly, while asparagin increases ; tyrosin and leucin decrease. At any rate, seedlings grown in the light retain for a long time a high amount of asparagin but contain very little amino acid. Palladin’s? experiments make it evident that the decreased current of transpiration in etiolated plants causes a too slight absorption of mineral elements, éspecially calcium. A lack of calcium salts, however, even in leaves rich in proteins, prevents all further development. Wiesner? has shown by numerous experiments that plants grown in the dark are less resistant to atmospheric influences. He found, for example, that seedlings, grown in the light, are much more resistant to the action of rain and water in any form, than seedlings developed in the dark. Observations made by Maige* on Ampelopsis and Glechoma show how the material differences come to expression in growth. Diffused light 1 Schulze, E., u. Castoro, N., Beitrage zur Kenntnis der Zusammensetzung und des Stoffwechels der Keimpflanzen. Zeitschr. f. phys. Chemie, Vol. XXXVIII. Cit. Botan. Centralbl. 1904, No. 47, p. 540. 2 Palladin, W., Hiweissgehalt der griinen und etiolierten Blatter. Ber. d. Deutsch. Bot. Ges. Vol. IX, p. 194.—Ergriinen und Wachstum der etiolierten Blitter. Ibid. p. 229. 8 Wiesner, J., Der Lichtgenuss der Pflanzen. Leipzig 1907, W. Engelmann. p. 260. i} oh = NEAR Se 4 Maige, Influence de la lumiére, etc. Compt. rend. 1898 ‘p. 420; VCit, Bort Jahresber. 1898. I, p. 587. 657 furthers the formation of the leaf shoots and can, in fact, cause the trans- formation of an inflorescence bud into a climbing branch. Direct sunshine has an exactly opposite effect. Green’s experiments! are very important for pathology and especially for the point of view which we would represent, that a whole series of diseases is caused by a change in enzymatic functions. He confirms the observations of Brown and Morris that the supply of diastase in the foliage is diminished after a period of bright illumination. The ultra violet and adjoining visible rays are especially important in producing such an enzy- matic decrease. Such an enzymatic destruction by light may be compared with the well-known killing of bacteria by light. SHADING. In agriculture, the injuries produced by direct etiolation are much less frequent and, on this account, less significant than the lower grade of occur- rences which arise from an insufficient supply of light; 1. e., too strong shading, and make themselves felt in the decreased production of useful substances. Stebler and Volkart? have made measurements of the removal of light caused by different trees. With a clouded sky, they found a decrease of light from the pine of 50 per cent. ; from the birch, 56 per cent. ; from the cherry, 78 per cent.; from the oak, pear and apple, 82 per cent. ; and from the beech, 95 per cent. Since each plant has its.definite need of light, cases also occur in which cultivation gives an excess of light, while the natural habitat would furnish the plant with only a subdued amount. This is found in many of our hop fields and in strawberry culture*. In such cases, shade causes an increased production but, in the majority, reduces the amount of dry substance and weakens the color of the foliage and blossoms. The question of shading may be of especial importance for our colonial plants. In Java, as well as in our East Africa colonies, coffee plantations suffer very frequently and Zimmerman?‘ ascribes this to a lack of shade trees which would prevent over-production by the coffee trees; for example, in Usambara, this has already caused great injury. It is probable that the consequent lessened strength of illumination, besides the protection from the wind and decrease of temperature, especially favors the thriving of coffee. The decreased harvest from plants which need light, due to the influ- ence of the shade of trees, arises not only from the limited amount of light but also from the lesser warming of the soil. E. v. Oven’s experiments? 1 Green, J. Reynolds. On the action of light on diastase. Phil. Trans. of the R. Soc. of London. Ser. B. Vol. 188; cit. Bot. Jahresber. 1897. I, p. 89. 2 Stebler, F. G., u. Volkart, A,, Der Einfluss der Beschattung auf den Rasen. Landwirisch. Jahrbiicher. d. Schweiz. Bern 1904; cit. Bot. Centralbl. 1908, Vol. LOIS ps 60: 3 Taylor, O. M., and Clark, V. A., An experiment in shading strawberries. New York Agric. Exp. Sta. Geneva Bull. 246, 1904. 4 Zimmerman, A., Hinige Bemerkungen zu dem Aufsatze von Fr. Wohltmann, usw. Berichte tiber Land- u. Forstwirtschaft in Deutsch-Ostafrika. Vol. I, Part 5, 1908. 5 vy. Oven, tiber den Einfluss des Baumschattens auf den Ertrag’ der Kartoffel- pflanze, Naturw. Zeitschr, f. Land- u Forstwirtschaft. 1904, p. 469. 658 show how great the differences can be. He found an average temperature of 22.26 degrees C. at g A. M. on ten days in August, in soil on which the sun shone, but, under a cherry tree, a temperature of 19.06 degrees C. In 1884, Wollny* had already measured the influence of soil shading due to weeds in a potato field and found, at a depth of 10 cm. in the soil, that the temper- ature averaged 2.6 degrees C. less than on a field cleared of weeds. Besides the temperature, the amount of water in the soil is of impor- tance. Gain’s measurements? show how much the soil moisture influences the size of the leaf. He reckoned the length of the organs set in a dry habitat at 100, the dimensions on damp soil for barley were 240; for poppies 550; for potatoes 150. If the plants continue to have too little water, their maturing is natu- rally delayed; their productivity is also considerably reduced. In this connection Bimer’s experiments® should be mentioned. He found that the ripening of potato plants was delayed 8 days in a soil with a 40 to 30 per cent. saturation capacity; 18 days in a 30 to Io per cent. saturation capacity in contrast to plants with an abundant soil moisture (80 per cent. saturation capacity). With the same high moisture content of the soil, Wollny har- vested 80 g. of tubers from pot plants, while he obtained only 39 g. with half the water content of the soil and only 19.5 g. with 20 per cent. satura- tion capacity. In growing herbaceous plants with shallow spreading roots, the yield is ‘markedly decreased by the deeper lying tree roots. In v. Oven’s investiga- tions, the water content under a cherry tree amounted to 20.24 per cent., in the unshaded vicinity, however, it amounted to 21.78 per cent. According to Wollny, 2.86 per cent. more water was withdrawn from a potato field by the weeds than by the potatoes alone. v. Oven describes the influence of shade on the plant itself, according to his own observations and those of other scientists. The stem members become longer; the leaves more slender and the ripening is retarded. The epidermis, the sheath of the vascular bundles, the walls of the ring ducts and medullary parenchyma are not so thick and the lignification is less. The cause of the lengthened period of growth of plants in the shade must be looked for in the lesser intensity of metabolism, which manifests itself in the weaker respiration, since, according to our experiments, the amount of assimilatory activity, under otherwise equal conditions, deter- mines the degree of transpiration, and this also explains the essentially lesser evaporation, and, on this account, the higher water content in shaded plants. Of the numerous experiments, which determine a reduction of the harvest due to shade and which v. Oven cites, in addition to his own, one by Wieske on a wheat field is of interest. The plants, which were shaded for the greater part of the day by fruit trees, gave a grain yield decreased 1 Wollny, Forschungen auf dem Gebiete der Agrikulturphysik, Vol. VII, p. 349. 2 Bot. Centralbl., Beihefte. Vol. IV, p. 418. 3 Bimer in Biedermann’s Centralbl. 1881, p. 154. 659 about 30 per cent., and a straw yield about 32 per cent. less than the un- shaded plants in the same fields. The results which Pagnoul' obtained are especially noteworthy. In experiments with sugar beets, he found a strong falling off in sugar content with an increase of the leaf substance per gram of root body and, for pota- toes, a decreased tuber yield with a significant falling off of dry substance. Besides this, however, he proved that the nitrate content for beets and potatoes, grown under blackened glass, was more'than ten times as great in the leaves and roots as in plants grown in the sunshine. Therefore, the physiological activity was changed in the shade since the nitrates were not sufficiently used up. Some of v. Oven’s experiments took up the measurement of the inten- sity of the light which remained after the sun’s rays had passed through a tree crown. It was shown by the Bunsen-Roscoe method, that the propor- tion of full daylight to the amount of light under fruit trees was about I to 0.3. The shade of apple trees reduces the intensity of the light, on an average, from 1 to 0.234; the shade of pear trees from 1 to 0.233; that of cherry trees from I to 0.345. For practical purposes, the lesson may be drawn from existing obser- vations that the cultivation of fruit trees between field plantations, so widely recommended, is unprofitable for northern regions. For southern countries, in which an excess of light and heat may at times injure the plants, the method will be advantageous. We find this theory confirmed by the fact that in Italy the fields are divided by rows of mulberry and olive trees, as well as by grapevines. According to Linsbauer? the cultivation of grapes in Italy (on pergolas) and in Austria (on low stakes) has been determined by adaptation to the light conditions. In southern regions, the: longer dura- tion of the sunshine permits the shading method of growth on arbors, while, in northern countries, the shorter period of sunshine must be fully used. Like Frank-Schwarz, we reproduce illustrations of beech leaves from Stahl’s well-known studies on the structure of shade leaves. In Fig. 152 may be seen a beech leaf grown in the sun, in Fig. 153, one grown in half shade; and in Fig. 154, another matured in strong shadow. We see from these how the leaf decreases in size with deficient illumination. The pali- sade cells (pp) are formed in a less characteristic way, the spongy paren- chyma (scif) becomes especially reduced and the vascular bundle cords weaker; a more feeble bud development is coordinated with the lesser leaf development. The formation of the tissue, especially the differentiation in the paren- chyma tissue®, depends upon the light intensity in the spring. Hesselman* 1 Annales agronomiques, Vol. VII, 1891; cit. v. Oven. 2 Wiesner, Lichtgenuss der Pflanzen. 1907. 3 MacDougal, D. F., The Influence of Light and Darkness, etc.; cit. Bot. Centralbl. 1903. Vol. XCII, p. 296. 4 Hesselmann, H., Zur Kenntnis des Pflanzenlebens schwedischer Laubwiesen. Beih. Bot. Centralbl. Vol. 17, 1904, p. 311, 660 found that the plants, completing their development in a constantly reduced, but not especially small amount of light, show a much scantier formation of the assimilatory tissue than those specimens which have a good deal of light in the spring but are strongly shaded in summer. With an equal amount of leaf surface, plants grown in the sun, with their matured palisade paren- chyma, transpire considerably more strongly than those grown in the shade’. According to Ricdme?, the palisade cells are said to be taller but narrower, the vascular bundles more abundant in the petioles. The same difference is found between specimens grown out of doors and in conservatories’. Investigations made by Count zu Leiningen‘ give us a satisfactory in- sight into the amount of work performed by light and shade leaves. He iwsware a Fig. 152. Cross-section through a beech Fig. 153. Cross-section through leaf matured in the sun, (After a beech leaf from a half shaded Stahl.) position. (After Stahl.) Fig, 154. Cross-section through a beech leaf from a very shady place. (After Stahl.) bp palisade parenchyma, sch spongy parenchyma. found in the beech, reckoned on the same amount of leaf surface, a con- siderably smaller content in pure ash (with the exception of silicic acid) in sun leaves than in shade leaves; the nitrogen content was corresponding. We explain this condition of affairs as follows:—the root system provides the leaves with equal amounts of mineral substances; it now depends upon 1 Bergen, J., Transpiration of sun leaves and shade leaves of Olea europaea and other Orval-leaved evergreens. Bot. Gaz. Vol. 38, 1904, p. 285. 2 Ricdme, R., Action de la lumiére sur des plantes étiolées. Rev. gen. de Bot. 19.02) “t. SSEVi, ps 26. 3 Kiister, Review of “Bédélian, Influence de la culture en serre, etc.,” in Holl- rung’s Jahresber. tiber Leistungen auf d, Geb. der Pflanzenkrank. Vol, VII, 1905, p. 7. (Further notes on Sun and Shade Leaves, cf. Kuster, E., Pathologische Pflan- zenanatomie 1903, p. 24, etc.) 4 Leiningen, Wilhelm, Graf zu, Licht. und Schattenblitter der Buche, Naturw, Zeitschr, f. Land- u. Forstwirtsch, 1905, III Year, Part 5. 661 how these are made use of. The more vigorously a plant grows, the more orgunic substances it produces per gram ash. Therefore, a lesser assimil- atory activity must be concluded each time, if the analysis proves a high ash content in proportion to the dry substances. In the present case, the scanty amount of light is the factor reducing production. Sensitiveness to shade is, at any rate, connected with a definite limit of value for each plant variety, but, as in all factors of growth, these values can shift individually to a certain degree, so that, in the same species, there may be races very sensitive to shade in which, in Nordhausen’s' opinion, certain reduction phenomena become herditary. Each leaf in the plant has its special sensitiveness to shade, according to the light conditions under which it was produced, and its position on the axis. The shade produced by leaves higher up is the most important. The amount of assimilation and respiration, as well as of transpiration, is deter- mined by this. In Griffon’s experiments’, for example, it was found that a leaf, as thick as that of Prunus Laurocerasus is not able, in direct sunlight, to completely prevent the carbon dioxid decomposition in the leaf of Ligustrum ovalifolium. Under two such leaves, however, the development of carbon dioxid took place. Under such conditions, therefore, assimilation was so reduced that respiration exceeded it. It naturally depends also upon what color the shaded plant parts are, i. e., which light colors can still pass through them. According to Teodoresco* the leaf tissues develop most poorly in green light ; they are found to be better in red light; the best development, how- ever, is found in blue light, and, therefore, the greatest enlargement. The chlorophyll grains are also smaller in green light, less numerous and not so regularly distributed as in red and blue light. The product of the activity of the chloroplasts, corresponding to their development, is proved especially favorable in the most strongly refrangible rays. Palladin* exposed etiolated cotyledons of Vicia in sugar solutions to white and colored light and found that the assimilation of the sugar, as well as the formation of active proteids, took place most vigorously in the more strongly refrangible light rays and, therefore, respiration was more intensive. If the leaf, because of a scanty light supply, cannot work any longer, it falls off, just as under the action of all other factors which suppress its assimilatory activity°. This explains the regular “summer leaf fall,” which, naturally, is different from leaf fall due to heat. Wiesner® explains the 1 Nordhausen, M., Uber Sonnen und Schattenblatter. Ber. d. Deutsch. Bot. Ges. Vol. XXI, 1903, p. 30. 2 Griffon, Ed., L’assimilation chlorophyllienne dans la lumiére solaire qui a traversé des feuilles. Compt, rend. CXXIX, Paris 1899, p. 1276. 3 Teodoresco, E., Influence des différentes radiations, ete.; cit. Bot. Jahresber. Fiwdanren 1901 Partai ps tos: 4 Palladin, W., Influence de la lumiére, etc.; cit. Bot. Jahresber. Jahrg. 1899, II, p. 134. ; 5 V6chting, H., Uber die Abhingigkeit des Laubfalls von seiner Assimilations- tatigkeit. Bot. Zeit. 1891, Nos. 8 and 9. 6 Wiesner, Jul., Uber Laubfall infolge Sinkens des absoluten Lichtgenusses (Sommerlaubfall). Ber. d. Deutsch. Bot. Ges. Jahrg. XII, Part 1, 1904, p. 64, 662 “summer ieaf fall’ in that the lowering of the daily light intensity, follow- ing the beginning of summer, brings about a lowering of the (absolute) amount of light, for the plant concerned, below the minimum, whereby an immediate loosening of the leaves is caused. The amount of bloom for each plant depends, of course, upon the abundance of the carbon assimilation, hence shaded specimens bloom less. Exclusively diffuse light delays the time of blooming and can prevent the complete ripening of the fruit, so that the seed will atrophy’. There are cases where plants, with a previously abundant assimilation, are placed in the shade before their blossoms develop. In the dark, the blossoms appear later, as a rule. Their color is paler and at times white; their size and amount of substance less and the peduncles not infrequently longer. If however, the leaves are left in the light and only the branches, bearing the blossom buds, are darkened, then, according to Kraus*, the flowers, with a few exceptions, develop completely. We have considered in the previous section the thin-walled condition of the cell elements in etiolated plants. THE LODGING OF GRAIN. The lodging of the stalks for a long period effects a loss in quantity and quality of the harvest. It is the more dangerous the more the bending of the stalk approaches actual breaking over. Investigators were inclined earlier to assume one single cause for this lodging until later observations determined that very different factors can come into effect and that, accord- ing to the causes, the breaking over of the stalk takes place sometimes at the base in the soil, sometimes close above this point, or higher on the stalk. Thus we know now that frost injuries often produce weakening of the stalks which without, or (usually) with the later co-operation of some fun- gus, initiates their falling over. Further, eating by insects, breaking from the wind, hail, long continued rainfall, not infrequently cause a direct falling of the stalks. While, however, the majority of the factors named cause a lodging of the grain in spots so that stalks remain standing upright between these places, the actual lodging most feared by the agriculturalist is the one occurring in continuous areas, due to weak development of the bases of the stalks. L. Koch‘, who has definitely shown by experiments that this results from a lack of light, produced artificially the phenomena of lodging by shading the stalks. The experiments made earlier by Gronemeyer® were 1 Passerini, N., Sopra vegetazione di alecune piante alla luce solare diretta e diffusa. cf, Just’s Jahresber. 1902, II, p. 628. 2 Beulaygue, Einfluss der Dunkelheit auf die Entwicklung der Bliiten. Bieder- mann’s Centralbl. 1902, p. 102. : 3 Kraus, Uber die Ursachen der Formveranderungen etiolierender Pflanzen. Pringsheim’s Jahrb. f. wiss. Bot., Vol. VII, p. 209. 4 Koch, Ludwig, Abnorme Anderungen wachsender Pflanzenorgane durch Beschattung. 5 Gronemeyer in Agronom, Zeit. 1867, No. 34. 663 thus confirmed. The weakness of the stalks, which conditions the falling over in lodging is found actually in the lower stem members and the second internode (reckoned from the base of the stalk) is the one usually bent over. To be sure, the first, lowest stem member is also weak, but, as a rule, it is too short to bend over; on the other hand, the second is the most elongated and the jeast thickened. The cells of this internode in lodged grain show a considerable over-elongation and scanty thickening in proportion to the corresponding cells of the normal stem. This deficient thickening is espe- cially noticeable in those cells which, in the blade, fill the space between the outer membrane and the vascular bundle sheath, and actually conditions the firmness of the stalk. Lodging of grain, therefore, is produced when the lower internodes of closely planted grain are insufficiently lighted. Too great shading also acts disadvantageously in the very early developmental stages of the plant by the over-elongation of the cells and the scanty thickening of the walls, which, as said above, takes place usually in the second internode from the bottom. This bad condition will occur more strongly in the places in the internodes where the leaf sheath surrounds the stalk most closely. This takes place near the base of the stem and the phenomena of etiolation are found most clearly and intensively here. Formerly a lack of silicic acid was ‘assumed as one reason for the lodging of grain. This may now: be explained as erroneous, since it has been shown by water cultures of grain plants, that minimal amounts of silicic acid are sufficient to produce a normal plant and since analyses of lodged grain, compared with grain which had not lodged, have shown but little difference in silicic acid content. In normal plants also, as Pierre has shown for wheat and Arendt for oats, the lowest internodes of the stall are the poorest in silicic acid, of which the greatest quantity in any case is found in the leaves. These can be 7 to 18 times as rich in silicic acid as the lower stem members. Connected with the lack of light is the second point, given as a cause for lodging, namely, that the disease may be traced to an excessive supply of nitrogen in the soil. At any rate, this is one cause inasmuch as a too luxuriant development of the leaf apparatus is thus produced, essentially increasing the shading. Such a cause is given, however, by every circum- stance which conditions a too thick stand from the seed, i. e., for example, too abundant seeding, too abundant water supply, etc. Experiments made by Ritthausen and Pott! show the change in the maturing of fruit due to different nitrogen fertilizers and the tendency of the plant to lodge. While the grains of summer wheat are well matured with an abundant supply of nitrogen but remain small and glassy like the seed, the grains from plots not fertilized with nitrogen, lodge after less heavy rain- storms. Kreusler and Kern confirmed the above statements. We may 1 Landwirtsch. Versuchsstationen 18738, p, 384. 2 Centralbl. f. Agrikulturchemie 1876, I, p. 401. 664. have in pure phosphoric acid fertilization a means of decreasing the dangers of a too large supply of nitrogen. At least, the results obtained by the above-named authors with wheat and barley showed that a fertilization with phosphoric acid alone (Baker guano with 18.97 per cent. soluble P, O,) resulted in a reduction of the nitrogen content of the grain. But, aside from the composition of the grain, which is changed by an increased nitrogen supply, the whole amount of the harvest must be taken into consideration, which had suffered not a little from a too luxuriant and, therefore, too thick and dark a growth of the plant. Experiments based mostly on the conditions occurring in practice, since they show the influence of shading from the sides, have been cited by Fittbogen’. Under otherwise perfectly similar nutritive conditions, he shaded barley plants by means of a cylinder of rye stalks, fastened side by side and placed around the barley plants, and raised it in proportion to the growth in height of the experi- mental plant, which was constantly illuminated at the tip. The plants, therefore, had light for production but still in insufficient amounts. On this account, they produced only about two-thirds as much dry substance as plants illuminated on all sides, in spite of the 4 to 6 weeks longer growth which were needed for complete ripening. The dry substance, however, was also distributed much less favorably in the different harvest products. While, with a normal illumination, 47 per cent. of the dry substance in summer barley, as a whole, was found in the grain, and 53 per cent. in the straw and chaff, from shaded plants, only 39 per cent. of grain was har- vested for 61 per cent. of straw and chaff, and the kernels were also poorer in quality. In regard to the water used, it was found that plants shaded on the sides, in spite of the at least 6 weeks longer growing time, had used only one-tenth more water in the hottest months (July and August). Therefore, in the same unit of time they absolutely transpired considerably less than the normally illuminated specimens, corresponding to the lesser production of dry substances. On the other hand, the plant will have evaporated rela- tively a great deal of water for we find, in shaded plants, that more than 500 g. of water were used per gram of dry substance, while normally lighted specimens have respired only something over 300 g. for the same amount of dry substance. Therefore, we find, in this vegetative factor, the same effect on transpiration as in others (soil solutions, carbon dioxid content in the air, etc.) A supply of one vegetative factor kept below the optimum, in- creases the relative use of water per gram dry substance produced. The loss due to lodging will be decreased in many cases by the fact that grain possesses the ability to right itself. The process of righting consists in the ability of the nodes to show phenomena of growth at a time when the internodes have already lignified. According to de Vries’ expla- nation?, a new formation of osmotically effective substances takes place in 1 Vortrag aus dem Klub der Landwirte am 14. Dez. 1875. 2 De Vries, ther die Aufrichtung des gelagerten Getreides. Landwirtschaftl. Jahrbiicher von Thiel, IX, 1880, Part 3. a 665 the parenchyma cells of the under half of the node, which carries out the bending, under the force of gravity, because the stalk with its node, is bent toward the horizontal. These parenchyma cells attract water. However, supported by the investigations of G. Kraus', we would like to assume that no considerable formation of osmotically effective substances (acids) takes place, but rather a longer retention of such substances on the convex side, as a result of a decreased oxidation of the organic acids. At least Kraus proves that as much acid is present on the convex as on the concave side in the occurrence of geotrophic and heliotrophic bending. The only actually successful precaution lies in thinner seeding, the quantity of which must be modified according to the consistency of the soil. On sandy soils the seeding must be thicker than on loamy soils, and thicker with a poorer fertilization than with an abundant supply of nitrogen. Planting with the drill is found to be the most useful because the best dis- tributed stand of plants is obtained thereby. If, however, the seeding has already taken place and a close stand, luxurious development, and moist weather give rise to a fear of a subsequent lodging, the attempt should be made to remove a part of the leaf apparatus by strong harrowing, rolling, or prudent mowing and uprooting, in order to provide a sufficient access of light. In regard to cultural regulations, we must refer to the recently pub- lished, very thorough work of C. Kraus’, based on, experimental studies, because the precautionary regulations, according to the different causes of lodging here mentioned, must also differ greatly. On general principles, it is not only a question of growing strong plants as resistant as possible to disturbances in equilibrium, but also to take pains that the plants, me- chanically well developed above and below the soil, find the indispensable support within the soil of a properly developed root system. The task of breeding now follows these two directions. Even the weather at the time of seeding acts determinatively for the position of nodes, regulating essen- tially the anchorage of the plant in the soil. According to Schellenberg’, the node lies higher if the seed develops in cloudy weather. It is, therefore, more advantageous (even for winter grain) when the seeds sprout in clear weather. In weak stemmed plants, inclined to lodge, there occurs also at times a decay of the parts entirely removed from the light, which causes consid- erable loss in the lodging of fodder peas. The sowing of some horsetooth maise with these is recommended as a precaution. The peas can climb up the stems of the maise and its leaves also furnish good fodder. The sowing of gold of pleasure (Camelina sativa) possibly 6 liters per hectare, is also recommended to prevent the lodging of peas, sweet peas, etc. This plant, which is perfectly hardy, ripens about the same time as 1 Sitzungber. d, naturf. Ges. zu Halle 1880; cit. Bot. Centralbl. 1882, I, p. 107. 2 Kraus, C., Die Lagerung der Getreide. Stuttgart 1908, Eugen Ulmer. 3 Schellenberg, H. C., Untersuchungen tiber die Lage des Bestockungsknotens beim Getreide. Forsch. auf d. Gebiete d. Landwirtsch. Frauenfeld 1902. 666 peas and the kernels may be easily separated from the peas by sifting, while the grain, generally grown with peas (summer rye and oats), is sifted out with much more trouble and exhausts the soil more for the following winter crop. Here also, as in grain, breeders are now directing their attention to resistance to lodging. The Bulletins published by the German Agricul- tural Society have proved to be most advantageous in this direction. They contain the latest results of cultural experiments with the different varieties of our cultivated plants. LACK OF LIGHT AS PREDISPOSITION TO DISEASE. When it comes to the attacks of parasites, the mechanical resistance of the membranes of etiolated plants will be less. However, the atmospheric influences become weaker and their fluctuations, reaching directly the cyto- plasmatic cell body, can disturb its functions even if the etiolated plant should work in the same way and with the same energy as one which has sufficient light. The last is, however, by no means the case. The first indication of a change in function is found in the moving of the chlorophyll grains toward the side walls, in the dark. At the same time another significant change begins, viz., the closing of the stomata. Accord- ing to Schwendener? this phenomenon, already observed in complete dark- ness, also sets in with a sudden decrease in the intensity of illumination. It is possibly not a result of the lowering of the temperature connected with the decrease of light, for an increase in temperature within the usual fluc- tuations causes no opening of this apparatus. Connected with this also is the fact that a longer suppression, or reduction of the exchange of gases, can bring about changes in the cell contents, due to a lack of oxygen, that 1s, for example, a tendency to the formation of alcohol. These disturbances will occur so much the more easily, the more intense the capacity for growth and the greater the need for ventilation. Therefore, very young organs will feel this, while old leaves, grown for many years, with a lesser need of light, endure longer limitation in the exchange of gases. Nature indicates this also by the wall thickening of the guard cells, increased with advancing age, which, according to Schwendener, is so strong at times that no further opening of the stomata can be possible. In regard to lessened transpiration, I found in young seedlings of Phaseolus, dependent upon their cotyledons, such a difference between etiolated and normal plants that the former, on an average, transpired in the same period of time, 0.21 g. per sq. cm. leaf surface; the latter, 0.29 g.? The production of dry substance in a plant, under otherwise equal condi- 1 Mittel. der Saatzuchtstelle tiber wichtige Sortenversuche 1905-1907 usw. 2 Schwendener, Uber Bau und Mechanik der Spaltdffnungen, MQnatEber d. Kgl. Akad. d. Wiss. zu Berlin, July, 1881; cit. Bot. Zeit. 1882, p. 234. 8 Sorauer, Studien iiber Verdunstung. Aus Wollny’s “Fiorschungen auf dem Gebiete der Agrikulturphysik.” Vol. I, Part 4-5, p. 116. 667 tions, parallels the transpiration. Investigation showed that not only the absolute production of the young plants was essentially more energetic in the light, but that also a square centimeter of leaf surface developed a greater amount of substances. A weakening of the light, by means of col- ored media, through which the rays must pass, acts similarly to the removal of light by placing it in the dark. In yellow light, assimilation and transpi- ration are more energetic than in blue light; at least the majority of experi- ments favor this’. The energy of production of plants and also the mode change with the decrease of light and this change is expressed, not only in the metamorphic, but also in the metabolic structure. The well-known experiment of covering leaves in the light with a stencil pattern, which leaves free some rather larger surface figures, remoy- ing the green from these leaves after some days by means of alcohol, and then wetting them with iodine solution, is a simple illustration of the action of light. All parts of the leaf, which have been exposed to the light, look blue because of the action on the starch which had been formed in the light. This experiment is of interest inasmuch as it shows how locally limited the action of light is. Only the part which had been illuminated formed starch and no starch passed over into the darkened, adjacent part. The most important thing. according to this, is that the green parts of the plant must themselves work over their constructive materials if they should continue to live. It has been mentioned already that the mobilized reserve substances pass into the young, entirely darkened shoots a certain distance from the tubers and seeds. If the distance is too great, however, the shoots finally die from starvation. They breathe up more respiratory material than they receive in the form of sugar, etc. Some of Miller-Thurgau’s? experiments show, for example, that the starch, when dissolved, passes over into sugar, which is used up partly for construction and partly in respiration. (Grape leaves, which contain 2 per cent. sugar and as much starch, were cut off and their petioles put in water. The contairier was set in a room at zero de- grees. Nine days later all trace of the starch had disappeared. Since the respiration of the grapevine, however, at zero degrees is very slight, the sugar, produced by the solution of the starch in the dark, cannot have been used up in respiration and must, accordingly, have accumulated in the leaf. As a fact, investigation shows 4 per cent. sugar in the leaves. Thus, placing in the dark will promote the formation of sugar in the organs as against the formation of starch. If, as is frequently the case in growing plants out of doors, an actual temperature decrease takes place with the decrease in light, it means a blocking of sugar in the assimilatory - tissues. 1 Compare Hellriegel, Beitrige, p. 8378. Nobbe, Versuchsstationen XXVI, p. 354. Flahault, Bot. Centralbl. 1880, p. 982. Dehérain, Bot. Zeit. 1873, p. 494, 2 Miiller-Thurgau, Uber den Finfluss der Belaubung auf das Reifen der Trau- ben. Weinbaukongress zu Diirkheim a. d. H. 1882. 668 Anyone who has cultivated fungi in nutrient solutions knows, however, how favorably a supply of sugar acts on the development of many parasitic fungi. Cloudy, cool days, therefore, not only weaken the assimilation in the green parts of the plants but, at the same time, by reducing the respiratory processes, bring about an accumulation of sugar in the leaf cells and, there- fore, make possible the production of a more favorable substratum for parasites. The acid content of the various plant parts is also very different in the dark from that found when the organ is favorably illuminated. The observation, that many plants (Crassulaceae) taste sour at night? but not noticeably so during the day’ is very odd. In etiolated plants, Wies- ner could recognize an abundance of organic acids* in the leaves of many monocotyledons, and later De Vries observed* that the stems of etiolated dicotyledons are strongly acid. When illuminated, the rich sugar content disappears. This has been, at least, especially proved for the Crassulaceae, in which, in the night, De Vries could determine a rich acid formation only when the plants had been abundantly lighted during the day, but, if the supply of light was limited to a few hours, the acid content in the night was correspondingly less. An increase of warmth increases also the decomposition of the acids in the dark. Cooler nights lead to the storage of acid. De Vries has proved this directly by experiments’. It is evident, how- ever, from the fact that the loss of acid becomes less with each successive day of shading, that the disappearance of the acids is connected with the supply of material for the formation of acid which has been worked over in the light. Plants, therefore, constantly produce acids and the more energetically the stronger growing the organs are. With light, the acids are oxidized as fast as they are produced; in the dark, they are stored up. On this account, etiolated plants are relatively rich in acids. The suppression of the inflor- escences increases the content of free acids in the leaf. The acid content in the roots is also subjected to great fluctuations and, according to Chara- bot®, in plants cultivated in the shade it is, in fact, larger than in the leaves. In general, this acid'content is greater in etiolated plants. This accumulation of acids in and of itself can offer those fungi, which decompose acids, the possibility of colonization and luxuriant development ; 1 Heyne und Link in Jahrbuch der Gewachskunde von Sprengel, Schrader und Link, 1819, p. 70-73. 2 Ad. Mayer, Uber Sauerstoffausscheidung usw. Verhandl. d. Heidelberger naturf. Gesellsch. 4-8, 1875. Landwirtsch. Versuchsstat. 1875, Vol. XVIII, p. 410, Vol, exe ps ene 3 Wiesner, Sitzungsber. d. K. K. Akad. d. Wissensch. I, April, 1874, Vol. 69; cit. Bot. Zeit. 1874, p. 116. 4 De Vries, Uber die Bedeutung der Pflanzensaéuren fiir den Turgor der Zellen. Bot. Zeit. 1878, p. 852. Uber die periodische Sdiurebildung der Fettpflanzen, Sot. Zeit. 1884, Nos. 22 and 23. 5 Bot. Zeit. 1884, p. 340. 6 Charabot, E., et Herbert, A., Recherches sur lacidité végétale. Compt. rend. 1904, CX XXVIII, p. 1714. 669 however, an excessive increase of turgidity in the tissue can be ascribed to this since, according to!/De Vries, it is especially the plant acids which condi- tion the turgidity of the cells. The experiments of Viala and Pacottet' on black rot (Guignardia Bidwellii) show how very determinative this acid content can often be. Infection experiments in young berries are successful only so long as the acid content exceeds the sugar content. Not only the content in organic acids is increased but also the indifferent ash material is changed by the changed absorption of nutrition. This is shown by André’s experiments? He tried to excite etiolated plants to unusual activity ‘by increasing the tem- perature (30 degrees), but found only an unusual increase in the absorption of silicic acid, with an exclusion of other mineral elements. The decomposition and counter building of the proteins in the plant cell? also stand in the closest connection with the above described processes of the formation and oxidation of the carbohydrates. In the germination and sprouting of buds on branches, roots and tubers, we find products of the decomposition of proteins which are similar to those of artificial protein decomposition, i. e., asparagin, glutamin, leucin, tyrosin, occur in very large amounts. According to Borodin’s investigations* these amido compounds occur more abundantly, the fewer the elements present which are free from nitrogen (especially the grape sugar) and which can be used for the breaking down of the proteins. Since in etiolated plants, as well as in others grown in the light but in air free from carbon dioxid, the new production of carbohydrates is sup- pressed and since these are used up by day in respiration, an accumulation of asparagin will take place. Among the more recent observers, we will mention Zaleski (cf. next page) who found an increase of asparagin in seedlings of Allium Cepa. The above mentioned work by Schulze and Castoro® should be especially considered, from which it is seen that, for example, in etiolated seedlings of Lupinus Albus the content in protein substances decreases; that in aspargin constantly increases. Tyrosin and leucin decrease. As a matter of fact, E. Schulze found more than half of the whole nitrogen content in 20 day old etiolated lupin seedlings in the form of asparagin®. If now the nitrogen frée part of the protein molecule is used up in respiration and no new elements, lacking nitrogen, are present to reconstruct normal protein in the protoplasm, the cell will undergo the most 1 Viala, P., et Pacottet, P., Sur le développement, du Black Rot. Compt. rend. 19045 (CXSEXIXS py lbi2. 2 André, G., Wirkung der Temperatur auf die Absorption der Mineralstoffe bei etiolierten Pflanzen. Compt. rend. 1902; cit. Biedermann’s Centralbl, f. Agrikul- turchemie 1903, Part 2. 3 Pfeffer in Jahrb. f. wissensch. Bot. 1872, Vol. 8, p. 548. Tagebl. d. Naturf. Vers. z. Wiesbaden. 4 Bot. Zeit. 1878, p. 802 ff. 5 Schulze, E., und Castoro, N., Beitrage zur Kenntnis der Zusammensetzung u. des Stoffwechsels der Keimpflanzen; cit. Bot. Centralbl. 1904, Vol. XCVI, p. 540. 6 Schulze, E., Uber den Eiweissumsatz im Pflanzenorganismus. Landwirtsch, Jahrbticher, 1880, p. 1-60. 670 extensive disturbances. Jt is probable that a further decomposition will introduce phenomena of decay which produce the best nutrient substrata for parasites and saphrophytes. The asparagin is worked up well by the fung in the presence of sugar. Vogel* found in the germination of moistened cress seed that hydrogen sulfid was produced in the dark, while, in check experiments, in lighted places, the lead paper showed practically no change. A different process may prevail in the leaf parenchyma from that in the leaf veins. In young Dahlia plants Borodin? proved the presence of saltpetre in the veins and in the petioles, but large amounts of tyrosin and no saltpetre in the leaf parenchyma. Here the tyrosin may well be no analytic product ‘but rather a synthetic one; for if the young shoots of dahlias become etiolated, no tyrosin is formed, but asparagin, which does not appear when the plants are grown in the light. At times, at any rate, an increase in proteins is found in the dark but it is then caused by the very abundant carbohydrates at the plant’s disposal in the stores of reserve substances, as Iwanoff* has shown, for example, for. Allium Cepa. If carbohydrates are present, the leaves, even in the dark, can change the nitrate nitrogen into protein nitrogen, as Zaleski* found in the leaves of Helianthus, which had been placed in a nutrient solution con- taining nitrates and sugar: We have stated here simply a series of facts which show the natural changes in the plant body due to a lack of light. These explain sufficiently the decreased power of resistance of the shaded plant parts through atmos- pheric influence. as well as parasitic attacks. 1 Vogel, Ein auffilliger Unterschied zwischen Keimen am Tageslicht und im Dunkein; cit. Bot. Jahresber. 1877, p. 675. 2 Sitszungsber. d. Bot. Sekt Petersburg. Naturf. Ges. 1881; cit. Botan. Zeit. 1882; p. 589. 3 Iwanoff, M., Versuche iiber die Frage, ob in den Pflanzen bei Lichtabschluss Eiweissstoffe sich bilden. Landw. Versuchsstationen 1901, p. 78. 4 Zaleski, W., Die Bedingungen der Hiweissbildung in den Pflanzen. Charkow 1900 (Russian); cit. Bot. Centralbl. 1901, Vol. 87, p. 277. CHAP TER XTv.. EXCESS OF LIGHT. According to the discoveries, already made in great numbers, on the influence of heat on the different vegetable processes, it must be supposed, from the outset, that not only does a minimal limit exist for the action of light, but that also a special degree of illumination exists in each plant for each process and for each combination of the vegetative factors, which can be termed the optimum. The exceeding of this degree introduces a retro- gression in production. In fact, the observation has already been made for a number of plants that, if the light is increased above a certain amount, the assimilation, perceptible in the elimination of oxygen, does not increase, but remains stationary’, or indeed may decrease*. A normal carbon dioxid content in the air is presupposed in this, for even when the air contains too large an amount of this element, the elimination of oxygen retrogresses, as has been proved already by Boussingault and, later, by Pfeffer?. An optimum illumination may be seen in the appearance of the plant since this loses its deeper green color, with a considerable increase in the intensity of light above the optimum; then it assumes a yellowish color. That the dark green leaves of camellias show a yellowed condition, when moved from the conservatory into sunny places out of doors, is well known. The camellia is a Japanese plant which grows under trees. It is content with small quantities of light and, with the strong rays of our summer sun, soon loses more chlorophyll through oxidation than can be formed by the process of reduction. The breaking down of the chlorophyll by the taking up of oxygen (taking place also in the dark in the presence of bodies which easily take oxygen from the air and form ozone, Turpentine oil) is known to be connected with different groups of rays. According to Wiesner, the yellow rays, and the green and orange ones on both sides of them, show the greatest energy in the breaking down of the chlorophyll in the light. Another example of yellow leaves with a high intensity of light is offered by some varieties of coleus with yellow variegated leaves. These 1 Reinke, L., Untersuchungen tiber die Hinwirkungen des Lichtes auf die Sauer- stoffausscheidung der Pflanzen. Bot. Zeit. 1883, No. 42 ff. 2 Famintzin, Effet de l’intensité de la lumiére, etc.; cit. Bot. Centralbl, 1880, p. 1460. 3 Pfeffer, Arbeiten d. Bot. Instituts zu Wiirzburg, ed. by Sachs, Part 1. 672 produce leaves which at first unfold as green leaves and later, when they become old, become light yellow in places. In the same way, many yellow garden varieties of woody plants only become a bright yellow with strong insolation ; in the shade they remain green. Ewart! observed in tropical plants a complete bleaching of the chloro- phyll grains as a result of an excess of light. If the/light stimulus increases above the specific optimum, the optimal and maximal development of gases at first continues for a short time, but then follows a condition of exhaus- tion®. If this excessive stimulation does not last too long, the plant can recover its normal activity. This over-stimulation can also occur under our normal light conditions, if the plant, by nature, belongs among shade plants. Weiss® cites a fine example of this in Polypodium vulgare, a de- cided shade plant, as contrasted with Oenothera biennis which is distinctly a sun plant. With a favorable temperature, the latter produced about three times as much carbon dioxid in direct sunlight as in diffuse light; while the former assimilated more energetically in diffuse light. Diffuse daylight can, in fact, act to arrest the growth of roots which are accustomed to the dark, as Kny found in lupines, cow beans, and water cress*. In this, he observed in lupines usually a decrease of growth in thickness and a retarding of the development of the central cylinder, if the growth in length increased. The works of Dixon, Dixon and Wigham, Joseph and Prowazek, Max Koernicke and Hans Molisch® prove a very decided arrestment of growth from the use of Rontgen and radium rays. An abnormal thickening and a wrinkled surface were observed in pea roots, which could be traced, apparently, to differences in internal tension. Contractions are produced by the increase in the radial diameter of the cells of the inner bark parenchyma, together with a shortening of the longi- tudinal diameter. It was found in other experiments with vetches and horse beans that the roots turned brown and their growth was arrested. But after 8 to 10 days they grew further, after having thrown off the outermost tips in the form of brown caps, and formed new root tips directly behind these. Normal lateral roots were produced immediately. The arrest of growth 'is less in organs containing chlorophyll. In seedlings a cessation in the growth in length has been observed but no dying back. The leaves became somewhat smaller than in normal specimens. Dixon® could not 1 Ewart, A. J., The effects of tropical insolation; cit. Just’s Jahresber. 1899, eae Sie . 2 Pantanelli, Enrico, Abhingigkeit der Sauerstoffausscheidung belichteter Pflanzen von Husseren Faktoren. Jahrb. f. wiss. Bot. 1903, Vol. XXXIV, p. 167. 3 Weiss, Fr., Sur le rapport entre ’intensité lumineuse et l’énergie assimilatrice chez les plantes appartenant A des types biologiques différents. Compt. rend. Paris CXXEKVIT, 1903iop. S01, 4 Kny, l., tiber den Hinfluss des Lichtes auf das Wachstum der Bodenwurzeln. Jahrb. f. wiss. Bot. 1902, Vol. 28, p. 421. 5 Seckt, Hans, Die Wirkung der Réntgen- und Radiumstrahlen auf die Pflanze. Sammelreferat. Naturwiss. Wochenschrift, 1906, No. 24. 6 Dixon, Henry, Radium and plants. Nature, London LXIX; cit. Just’s Bot. Jahresber. 1903, II, p. 567. 673 find heliotropic curvature in young cress seedlings at a distance of one cen- timeter from a glass tube containing 5 g. of radium bromid. In bright sunlight. we find that parts of the plant often not only become yellow but even turn brown and die’. That this dying is a specific light action and not a result of too great an increase in temperature is proved by the fact that the chlorophyll remains unchanged? in temperatures varying from 30 degrees below zero to 100 degrees abeve zero and, on the other hand, that the destruction takes place with rays of shorter wave length which influences most of all the processes of growth and protoplasmic movement. The rays of a concentrated sun image, which have passed through ammoniacal copper oxid often cause death after a few minutes, while the same amount of light, after passing through a solution of iodine in carbon disulphid (which lets only the outermost red rays pass through) scarcely causes any destruction, or only a very tardy one*. In this red light, how- ever, an extensive warming takes place, but not in the blue light. Among the phenomena arising from an excess of light belongs also the production of shadow pictures, i. e., intensive green pictures of overshad- owing organs on a strongly lighted leaf surface. No destruction of the chlorophyll apparatus necessarily ‘takes place here, only a change in the position of the chloroplasts is produced. Observations, made by Bohm, Famintzin, Borodin, Stahl and Frank, proved that, in sunlight too high for the special need of the plants, the chlorophyll grains begin to move from the cell walls, parallel to the upper surface of the leaf, towards the walls at right angles to them. The chloro- plasts pass from the epistrophe to the apostrophe and thereby bring about the lighter color of the too strongly lighted part. A further observation which can be made easily is the appearance of a red color with too strong lighting in the green leaves of plants which turn red in the autumn, as, for example, when the under sides of sweet cherry leaves are turned uppermost. In the same way, a decided brownish red color may be found in many plants, especially in those with fleshy leaves, when brought in spring from the shaded conservatories into an open, sunny place. Molisch* has investigated such cases. He proved in Aloe and Selaginella that anthocyanin is not formed in the cells but that the chloro- plasts themselves turn red and become green again when put in the dark. In some varieties of Selaginella, red or brownish red chloroplasts were observed, colored by carotin, especially above a place where the stem had broken. The process most important agriculturally and most significant hygienically, however, consists in the destructive action of the sunlight on 1 Bohm, Versuchsstationen 1877, p. 4638. 2 Wiesner, Die naturlichen Einrichtungen zum Schutze des Chlorophylls. Festschrift; cit. Bot. Tahresber. 1876, p. 728. 3 Pringsheim, Jahrb. f, wiss. Bot. 1879, Vol. 12, p. 336. 4 Molisch, H., thber voriibergehende Rotfarbung der Chlorophyllkérner in Laubblattern. B. der Deutsch. Bot. Ges. 1902, XX, p. 442, 674 pathogenic fungi and especially on bacteria. Pfeffer’ says, “It seems that all pathogenic bacteria are killed by a sufficient exposure to sunlight.” That artificial light acts in the same way as sunlight is proved, for example, by the experiments made by Dixon and Wigham? with radium rays. Cultures made with Bacillus pyocyaneus, B. typhosus, B. prodigi- osus and B. anthracis showed that the § rays of radium bromid called forth a perceptible arrest of growth. After 5 mg. of radium bromid had acted 4 days on the bacteria, at a distance of 4.5 mm., their growth, at least, was stopped, if they were not all killed. 1 Pflanzenphysiologie, 2d ed., Part II, p. 319. 2 Dixon, Henry H., and Wigham, J., Action of Radium on Bacteria. Nature, London LXIX; cit. Just’s Jahresber. 1903, II, p. 567. SECTION Til, ENZYMATIC-DISEASES. CHAPTER XG. DISPLACEMENT OF ENZYMATIC FUNCTIONS. GENERAL DISCUSSION. Present investigations tend to the theory of perceiving, in the majority of metabolic processes, the action of enzymes. We would like to divide these enzymes into two groups, according to their activity, which may be called constructive and destructive. In the process of formation of the vegetative organism, we observe in germination, i. e., in the preparation for the vegetative development, a prevalence of the destructive activity since the reserve substances are dissolved and carried over into usually instable groups of substances, capable of being transported. The activity of the vegetative apparatus leads gradually to the precipitation of reserve sub- stances and we term this activity constructive. Its final goal may be recog- nized in the maturation of the seed. From this may be perceived an antagonism in the occurrence of the most important material groups, which antagonism may be determined by the fact that, in abundant deposition of starch, the sugar content, as well as the amount of tannin and of organic acids, decreases. If, on the other hand, sugar, tannin and acids are abundantly present, the precipitation of starch remains small. If the amount of starch is large, the formation of the proteids in the cell from asparagin or other nitrogenous compounds is abundant. In the preponderance of sugar and acids, the nitrogenous com- pounds remain in an instable form. I would like to contrast this condition of the plant parts as “immature,’ with the “mature” condition which is distinguished by an abundance of reserve materials. The different factors of growth that influence constantly the plant body sometimes let one group of enzymes prevail, sometimes another. It is not necessary that the enzymes be destroyed. Their action need only be 676 temporarily arrested. Pozzi-Escot! furnishes an example of this when dis- cussing the Philothion. “Reductases,’ he thinks, which are identical with Loew’s catalase, “are distributed everywhere like oxydases, and act antag- onistically’ . . . De Rey-Pailhade has proved that reductases are quickly destroyed by an oxydase in the presence of free oxygen, and, con- versely, Pozzi-Escot proves that, under certain circumstances, the action of an oxydase can be “paralyzed,” when the reductase is present in great ex- cess. Thus, in temporary fluctuations in the cell contents, a reductase can. for the moment, make the oxydase ineffective, and conversely. Pozzi- Escot perceives the most important role of the reductases to be their action on H, O, in the processes of respiration as well as in photo-synthesis, Antiferments occur in other cases, as Czapek’, for example, has dem- onstrated. He found an arrestment in the further oxidation of the homo- gentisin acid, originating from tyrosin, in organs stimulated geotropically or heliotropically by the presence of an antiferment. In general, we perceive from the results of cultivation and some experi- mental investigations, that light and heat favor catabolism, i. e., disposition of groups of solid reserve material, while darkness and cold either maintain, or cause an increase in the amount of colloidal food materials. Under normal climatic conditions, the time at which prevailing condi- tions in the cell contents exhibit the conditions characteristic of the destructive activity, lies actually in the colder seasons of the year. We find processes of germination especially in autumn and spring, but, on the other hand, constructive activity, i. e., the deposition of reserve materials, ‘in the summer. The necessary regular succession of these periods depends, however, not only on the weather but also on all the nutritive factors, as, for example, the supply of water, the amount and constitution of the nutrients, and, besides this, on differences in cultivation, viz., pruning, etc. A number of diseases offer examples for the last point, i. e., when the organism is com- pelled, by the sudden removal of considerable amounts of the plant body (branches and leaves), to mobilize again the stored material at a time when the period of storing should prevail and, thereby, to return to the vegetative period for the formation of new shoots. In regard to the supply of food we find, for example, that excessive amounts of nitrogen postpone the period of storing up reserve materials since growth is continued beyond the normal size. i Thus, the enzymatic work is postponed; the mobilizing enzymes now prevail and the plant, with organs in active growth, enters upon a period of weather which, in the normal course of events, demands mature plant parts, rich in reserve materials. It becomes, therefore, susceptible to para- sitic and non-parasitic attacks. 1 Pozzi-Escot, E., The Reducing Enzymes. American Chem. Journ., Vol. XXIX, 1908, p. 517; cit. Bot. Centralbl. 1904, No. 49. 2 Czapek, F., Antifermente im Pflanzenorganismus. Ber, d. Deutsch. Bot. Ges. 1903, Vol, XXII, p. 229, 677 It is, however, not only the momentary displacement of the enzymatic functions which can act disadvantageously on the organism, but the number of subsequent phenomena must necessarily be connected with it, which will manifest themselves only in the next generation. If, for example, we keep in view the lengthening of the period of growth, induced, as experience shows, by an excess of nitrogen, the immediate result is that the production of seed, which normally occurs at the period of the greatest amount of heat and light, is carried over into a cooler time when the light is poor. The seed thus produced, therefore, does not have sufficient time and proper climatic conditions to carry on all the processes necessary for the formation of reserve materials. The seed is harvested in a condition in which the mobilizing enzymes are still considerably active and it, therefore, is suscep- tible to attacks by parasites affecting the fully matured seed. It has been proved experimentally that immature seed is destroyed more quickly by moulds. Even if the immature seed is not destroyed. and develops the following season, the plant thus produced will necessarily be influenced in its first growth by the greater amount of water content in the seed and the lesser amount of reserve materials. In this connection the following gen- eration is the product of the preceding one, and, therefore, will reproduce by inheritance conditions of weakness. Everything that is true of the seed, must also hold good for all other permanent organs. The bud and the maturation of the branch are, in the same way, the product of the preceding period of growth and the manner of their further development depends primarily on the degree of maturity to which they attained in the previous year. Displacements of the enzymatic functions, therefore, are continued from one period of growth to another and the diseases, subsequently described, are examples of the inheritance of physiological disturbances. ALBINISM (VARIEGATION ). The phenomenon, sought by gardeners and propagated by grafting (which may, in fact, be carried over to the stock), manifests itself in the whitish appearance of places which sometimes have a circular form in the diachyma (mesophyll), sometimes appear as wedge-shaped stripes between the ribs, and sometimes as connected zones along the edge of the leaf. The intensity of the white coloration varies. The most diverse transitions from the purest white to quince yellow are found, which in many plants give still further color shades because of the occurrence of reddish tones. In this way is produced the phenomenon called variegation. A very well-known example of this white spotted condition is found in the ribbon grass of our gardens (Phalaris arundinacea L., Phalaris picta L.), in which the white parts occur alternately as stripes between the veins. A toy species of the ash leafed maple (Acer Negundo L.) is still more striking. At times this shows perfectly white foliage. The family of the Aroideae might be named as examples of the occurrence of variegation as 678 well as of white coloring. Among these, the calla, frequently cultivated in the house (Zantedeschia aethiopica), shows leaves which often are as pure white as the funnel-shaped blossom sheath. The bright colored calladia, greenhouse favorites, are related to the Zantedeschia. Among them a few are only specked with white, others have white and red spots, and many finally only red spots. The white spotted condition of the fowers and the more rare albinism of fruit are difficult to distinguish. Of the latter, Dufourt has described interesting cases in grapes. There prevails, especially in practical circles, an earnest hesitation in accepting the theory which ascribes the white variegated leaves to the phenomena of disease. Yet, we believe that this opinion must be defended. If we investigate a considerable number of plants with variegated leaves, we find all gradations in the cells from the normal chloroplasts to the entire disappearance of the chloroplastids. The parts of the plants which appear yellowish often have chloroplasts which appear as yellow, sponge-like balls or discs in the cells; the purer white the plants are, the fewer are the even colorless chlorophyll bodies; and the more the cytoplasm ‘assumes the ap- pearance of a soft, uniform wall lining. The intercellular spaces contain more air and at times are larger. The assimilation of carbon dioxid also ceases with the disappearance of the chloroplasts. Cloéz? and later Engelmann*® found that the leaves assimilate carbon dioxid only in proportion to their chlorophyll content. The different gradations in the yellow variegation arise from lesser quanti- ties of the same chlorophylline and zanthophyll, than occur in the normal green leaves‘ and their assimilatory activity is in accordance with this. In pure white leaves the chlorophyll does not form and the chloroplasts are poorly developed. In the yellow forms, chloroplasts are found at least in the bud and often later but the degree of degeneration of the chloroplasts depends on their proximity to the pure white zone. The analyses given by Church® serve as a good confirmation of this. He used white variegated forms of maple (Acer Negundo), Ivy (Hedera Helix) and Holly (Llex aquifolium) : Acer , Ilex Hedera They contained white green white green white green leaved leaved leaved leaved leaved leaved percent. percent. percent. percent. percent. per cent. WIRE Oe mere ces ate ete 82.03.) w270 FAsiA, O25 78.88 66.13 Organic substances 15.15 24.22 23:00) 8535-41 1S7ae 31:03 ANShi3353--s0 tata 2.02 3.08 2.20 2.47 38 2.24 1 Defour, J., Panachierte Trauben. Extr. Chronique agric. du canton de Vaud; cit. Zeitschr. f. Pflanzenkrankh. 1904, p. 286. 2 Compt. rend. LVII, p. 834. 3 Engelmann, Farbe und Assimilation, Bot. Zeit. 1883, Nos. 1 and 2. 4 Krinzlin, G., Anatomische und farbstoffanalytische Untersuchungen an panachierten Pflanzen. Inaug.-Diss. Berlin 1908. 5 Church, Variegated leaves. Gardeners’ Chronicle 1877, II, p. 586. 679 The green leaves show, therefore, in contrast to the white spotted ones, considerably greater amounts of dry substances, while in the latter the ash constituents (as found universally where disturbances in nutrition make themselves felt) form a greater percentage of dry substance. The nitrogen content in the white leaves of the ivy and the holly was greater in propor- tion to the dry substance. This result is also explicable; for, if the chloro- phyll apparatus, without doubt necessary for the production of starch grains and other carbohydrates, is only scantily present, the amount of dry substances is reduced and the absolutely smaller amount of substances con- taining nitrogen appears relatively increased. The fact that the substances soluble in alcohol and ether in the white leaves of ivy and holly amount to about half that in the green leaves likewise may not be considered surprising. The percentages in the ‘composition of the ash are very important. They are as follows :— EXCEE Ilex Hedera white green white green white green Decent Percent. Per cent..per cent, percent. per cent: HOHABIY grr ative, Sesh A5.05. . 12:01 25.40 10.22 A7.20°. 17.01 TESTA Rayos, ey ove tera! 2 10.89 39.93 21.50 34.43 12.92 48.55 MAP MESIA 2a. sss « 3.95 AGS 3.23 2.43 ewes 1.04. Phosphoric acid... 14.57 8.80 9.51 729 10.68 3.87 EGOM ORICON 342 was é P 2h aya 2.62 2Er It is evident from these figures that organs without pigmentation approximate the condition of young green leaves and have, therefore, failed to develop in a normal manner. Griffon’ has come to the conclusion that plants without pigmentation behave in general like etiolated ones, which we have also compared to arrested development. In the yellow transitional stages the results of variegation are very different. In Abutilon Thomp- sont I found the cell content in many leaves still arranged as in perfectly green parts, 1. e., provided with chloroplasts, their edges roundish angular, which were normally arranged against the walls but were a pale yellow, or colorless, and had a strongly granulated content. In other cells the sub- stance of the chloroplasts was united into irregular |\granular balls which took on a blue color with iodine, glycerine, and in part also with sulfuric acid and which might be called carotin. Kohl’ also found carotin (etiolin), in the investigation of golden yellow leaves, besides /-zanthophyll and phyllofuscin. The difference in the thickness of the leaf, i. e., the noticeably lesser thickness of the pure white parts in contrast to the pure green parts, decreases the more the color tone varies from the pure white; i. e., the more yellow the places in the leaf become. Timpe® also calls attention to this 1 Griffon, Ed., L’assimilation chlorophyllienne et la coloration des plantes. Annal. se. nat. VIII, 1899; cit. Bot. Jahresber. 1899, I, p. 151. 2 Kohl, F. G., Untersuchungen tiber das Carotin und seine physiologische Bedeutung in der Pflanze. Leipzig, Borntrager, 1902, IX, 3 Timpe, H., Beitrige zur Kenntnis der Panachierung. Dissertat., Géttingen, 1900. 680 circumstance and lays emphasis on the fact that the slime cells are fewer in the non-pigmented parts of plants which bear the mucilage cells (Ulmus, Crataegus). On the other hand, the content of tannin in the white parts is usually proved to be greater. Starch is found rarely but, according to Timpe, in a sugar solution is often formed more abundantly by the non- pigmented places than by the green ones. Monocotyledons store up no starch in a sugar solution. It is stated by other authors that the pure white places contain no starch since assimilation does not take place there. These apparent contradictions are explained by the transitional stages to a golden yellow color which, indeed, contain no chlorophyll but have zanthophyll and carotin and elim- inate oxygen in the light (like etiolated leaves) *. An interesting fact is that in many plants a lack of pigmentation may be communicated to the stock by grafting. Meyer’ reported experiments of this kind with positive results as early as 1700-1710 with Jasminum officinale. “If a branch of Jasminum with variegated leaves is grafted on the healthy trunk of the same Jasminum, the other branches above and below the scion likewise bear variegated leaves.” Later Lindemuth? and recently Baur*® have studied the question especially. Baur has advanced the theory that the yellow forms may be considered to be sport varieties, or mutations, which in part persist in the seed. The pure white, however, should be distinguished from these as examples diseased by infection. At any rate, the infecting body may be no living creature, but an unknown material something, a virus which can increase in amount within the dis- eased plant. This virus can be a metabolic product of the diseased plant which is able to infect the young chloroplasts in such a way that they cannot develop tc normal organs, but to malformations in which then the same virus is formed anew. However, it may be a metabolic product of the diseased plant which, in a certain sense, has the capacity for growth, i. e., can split off substances ‘from other compounds identical with it, or can synthetically construct new substances of this kind*. This line of thought has already been expressed in a more precise form by Pantanelli®, and later supplemented. He says‘, “the albinism is not an infectious disease, but a constitutional one, the first sign of which occurs as an abnormal accumulation of destructive and primarily oxidizing enzymes.” “The substances, causing the destruction, spread through the leptome * Kohl, loc. cit. 1 Meyen, F. J. F., Pflanzenpathologie, Berlin, 1841, p. 288. 2 Lindemuth Vegetative Bastarderzeugung durch Impfung. lLandwirtschaftl. Jahrbticher 1878, Part 6. Gartenflora 1901, 1902, 1904. 3 Baur, Erwin, Zur Aetiologie der infektidsen Panachierung. Ber, d. Deutsch. Bot. Ges. 1904, Vol. XII, p. 453. Further statements on the infectious chlorosis of the Malvaceae and other simila: phenomena in Ligustrum and Laburnum. Ber. d. Deutsch. Bot. Ges. 1906, Part 8, p. 416. 4 Baur, E., Uber die infektidse Chlorose der Malvaceen. Sitzungsber. d. Kgl. Preuss. Akad. d. Wiss. January 11th, 1906. 5 Pantanelli. E., Studii su l’albinismo nel regno vegetale. Malpighia, Vol. XV-XIX (1902-5). 6 Pantanelli, E., ttber Albinismus in Pflanzenreich. Zeitschr. f. Pflanzenkrank- heiten 1905, p. 1. 681 bundles, either because of an energetic influence due to adjacent and com- municating protoplasts, or of a material transportation by means of sieve tubes and analogous elements throughout the entire body; they reach at last the developing petioles and then the main ribs of the leaves. Here they influence all the parenchyma cells with which they are connected clearly more energetically or because of a poor nutritive provision and removal.” The transference of the phenomena from the scion to the stock, therefore, comes about if, in grafting, the leptome connection in the two component parts has been established. This theory is based on experimental studies. It has been proved by chemical investigation that “the protoplasm and plastids are gradually attacked by abnormal formations of strongly destructive enzymes and digested by them.” In some intensive cases of albinism no accumulations, however, of inorganic, or organic substances, or sugar, may be proved. A determination made by Pantanelli on Ulmus leaves throws light on the behavior of the nitrogen compounds. He pulverized green and non- pigmented leaves with the necessary precaution and let the pulp stand 8 . days in a cylinder. The original amount of water in the green leaves averaged 60.67 per cent., that in the non-pigmented leaves of the same tree, at the same time, 73.8 per cent. The green leaves contained (in percentages of the dry weight). In the beginning ’ After 8 days Nitrogenasea WHOLE Se. ch 2 Se 3-355 per cent. 3-3250 per cent. Prove Gn MitrOVemy, a). sai biecee as duenae gy ee 0.9212 5 Non-proteid nitrogen .......... O.08T a!) 24050) a Non-pigmented leaves contained (in percentages of the dry weight) : In the beginning After 8 days Nitrogen aseaawhole., 7.2.2.2... 2-061 per cent. 2.576 per cent. EVEOtetdrmitO@emts sar cso d.c.62 12 «a SOTA, Aer . O1GO4 is Non-proteid nitrogen .......... OOF tn: LO 7 2a Autolysis in the sap of the variegated leaves is, therefore, compara- tively more extensive than in the green ones. The amount of nitrogen in non-pigmented organs is considerably less, but the percentage of non-proteid nitrogen compounds is greater. The richly abundant phosphoric acid must be present in some other combination since lecithin cannot be formed nor the chloroplast be developed. Also, according to Pantanelli’s investigations, an enzyme which breaks up the starch seems to be present more abun- dantly in the variegated leaves than in the green ones, at least when they are young. In the second edition of this manual (p. 195), I have already referred to the nitrogen poverty of the non-pigmented parts and there expressed the following opinion :—in the normally nourished leaf cell so much cyto- plasm is present that not only material can be furnished for the develop- ment of the cell wall, but the chloroplasts can also be produced abundantly. 682 If the supply to the young cells is cut off too soon, because the material, increasing the amount of protoplasm, is supplied too scantily, and the cell wall becomes old prematurely, the cell can have performed only the first part of its task, the formation of the wall, and has nothing left over for the formation of the apparatus which produces reduction and increases the dry substances, nor for its maintenance. This same poverty must occur in the normal cell if it gets into conditions of growth which cause an accumulation of destructive, i. e., amylolytic enzymes, whereby it is again carried back toward the young stage. If the plant is brought under conditions which favor normal vegetative activity (shade, moisture and heat) the non-pig- mented parts of the axis tend to produce green leaves. A discovery of Lindemuth’s confirms this observation. He proved that intense light actu- ally favors albinism. Ernstt mentions that in Caracas Solanus aligerum Schlecht., common to that region, is found not infrequently with variegated leaves. This occurs, however, only on poor sou. Specimens with strougly variegated leaves, transplanted to better soil, become green. With Urtica dioica, Beijerinck”, even in one year, succeeded in bringing back the green form from the variegated form by means of cuttings. Tissues, with a less concentrated cell sap are, however, less resistant. Actually, the white leaved parts of the plants are more sensitive to heat, frost, and drought, and die sooner. We find more abundant examples in the white leaved Acer Negundo, in which even the bark of the branches becomes variegated. Almost every year, summer sunburn and winter frosts kill the most exposed branches. Such cases also occur in conifers*. In the same way seedlings with white cotyledons and plumules are very easily destroyed. Not infrequently I] have found pure white seedlings, or white ones with a reddish tinge, in larger sowings of various kinds of fruits. These were always treated with special attention but died after some time, in case they did not begin to produce green leaves. Similar observations have been made also by others, for example, on Phormium tenax (de Smet), Passiflora quadrangularis as well as on Dahlia variabilis, Dianthus Caryo- phyllus, and the Liliacea (Lindemuth). A scarcity of reserve substances in non-pigmented branches explains also the further observation that their cuttings grow with greater difficulty than those from the green parts of the same individual. Consider, for example, hydrangeas with pure white leaves and geraniums from the group “Miss Pollack.” Lindemuth observed in Abutilon that the non-pigmented leaves are usually smaller and have a‘shorter life period. We would recail in this connection the phenomenon, occurring not infrequently, in our wild plants, that when one-half of the leaf is white, the other half green, the former remains shorter and the latter, on this account, curves about the white half in the form of a sickle. (Cichorium, Beta.) In marbled leaves, the white 1 Botanische Miscellaneen. Bot. Zeit. 1876, p. 37. 2 Beijerinck, M. W., Chlorella variegator, ein bunter Mikrobe; cit. Bot. Cen- trabl. G. Fischer, 1907, p. 333. 8 Zeitsch. f. Pflanzenkrankh, 1896, p. 361. ® 683 fields of a leaf often appear distended, the green ones wrinkled, or blistered. The stems also at times, in the non-pigmented part, show some shortening, as is proved by the variegated Kerria japonica, of which green shoots on the same stem and of the same age are at times half a meter taller than those bearing white leaves. Sambucus, Weigelia and others, behave in this way. in my opinion, albinism is a form of arrested development which occurs more rarely in wild plants but to an increasing degree in cultivated ones and manifests itself in the poorer nourishment of the different tissue ele- ments. The result of this is that, either the chlorophyll apparatus does not maiure at all, or soon falls victim to destructive enzymes. The lack of any accumulation of reserve materials, or, at most, a scanty one, is connected with this and explains the increased collapsibility of the tissues. Of the causes producing albinism, the pressure conditions in the bud should come first under consideration which arrest the development of the conducting system and thereby hinder the sufficient filling of the cells with plastic material even in the embryonic condition. This would explain the phenomenon of the sudden development of a non-pigmented shoot from the bud of a plant which had been green up to that time. In regard to cultural influences, experience shows that a relative excess of light acts favorably, for we see that often a condition of pure white leaves occurs very inten- sively with direct, strong insolation and is retained longest, but decreases, when shade and a sufficient supply of water and nitrogen give the leaf time to develop more slowly and let its vegetative functions act longer, i. e., preventing a premature end of life. Timpe' cites in his latest work a phenomenon which has been repeat- edly tested experimentlly. He repeated the experiments first described by Molisch*? with the white and green variegated species of Brassica oleracea acephala and obtained the same result, viz., that the brilliant white color of the leaf surfaces, which reaches its greatest development in winter in a cold frame (up to February), decreases almost at once and finally disappears if the plants are brought into a warm place. Molisch transferred white variegated plants from the cold frame at 4 degrees to 7 degrees C. into a hot bed at 12 to 15 degrees C. All the leaves already formed turned green in from 8 to 14 days; those newly formed appeared green at once. Returned to the cold frame, the specimens again formed leaves variegated with white. Here belongs also Weidlich’s statement® that Sclaginella Watsoniana must be cultivated in a temperature of 10 degrees C. if it is to form white tips. In these cases, therefore, the increase in the vegetative functions, producing the loss of albinism, is conditioned by the increase of heat; while in other cases, according to the nature of the plant and other local nutritive condi- tions, the variegated leaves can be brought back to the optimum of their 1 Tempe, Heinrich, Panachierung und Transplantation. Jahrbuch d. Hamburg. wiss. Anstalten XXIV, 1906, Beiheft 3. 2 Berd. Deutsches BOb Gen exdexe 1. piss 3 Gartenflora 1904, p. 585. 684 functions and to the normal formation of chlorophyll by decrease of light and heat; or by the increase of the nitrogen or potassium supply, thus pro- longing the period of growth. A scanty supply of material frequently manifested in the increase of tannin and the absence of starch, the small size of the cell and the increase of the intercellular spaces, is also emphasized by Timpe in his carefully worked out experiments. He describes a phenomenon for Ulmus which seems strange to him but is exactly the best proof of our theory. In this the luxuriant spring growth of shoots variegated with white developed per- fectly green foliage after the tree had been set out; but the midsummer growth, with a lack of water and excess of light and heat, again showed the variegation*. If, however, albinism consists in the premature ending of life, i. e., in the suppression, or arrestment, of the work of the chlorophyll apparatus, the destructive enzymes, even 1f not increased in absolute amount, still obtain a preponderance in the cell because those which cause the formation of the reserve materials, have been too little developed due to the lack of chloro- phyll activity. The equilibrium otherwise formed in the cells containing chlorophyll is destroyed. We, therefore, do not need to assume the formation of a “virus” :— a group of materials acting poisonously, which must be produced and increased in the plant,—in order to explain albinism and the phenomena of disease related to it (the mosaic disease, shrivelling disease, etc.). It is simply a change in the functions, i. e., a different direction of the mole- cular motion to which we must trace back, however, all metabolic processes. If this changed formation of substances is a movement, it can continue until some other form of molecular motion causes its arrestment. The non- pigmented part of the plant is, therefore, the carrier of an abnormal motion in its substances and on this account it would not seem strange if this motion is continued as soon as the paths, i. e., the vascular bundles (according to Pantanelli, the leptome parts), of two separated individuals are united, as is the case in grafting. If we consider albinism not as a phenomenon coming from the ranks of the other phenomena of variegation but only as the most extreme case of a process representing a decrease in the amount of chlorophyll, it can no longer seem strange that plants, variegated with yellow and, therefore, less irritated, can still be brought to the production of seeds in which the same direction of the metabolic motion is continued, i. e., that the seeds furnish plants with yellow variegation. Tue Mosaic DISEASE OF TOBACCO. The most recent authors, who have written on albinism, have already mentioned the relation of this phenomenon to the mosaic disease of tobacco. + WoC: Cit... 68: 685 This name originated with Adolph Mayer, who in July, 1879, when the disease had occurred to an alarming extent in Holland, received some dis- eased plants from the Society of Agriculture (Department Wijk bi Duurstede) for investigation. He published the results of his experiments in 188s, in a Dutch periodical and in the following year in the “Landwirt- schaftlichen Versuchsstationen’?. According to F. W. T. Hunger*® Van Swieten in 1857 had first called attention to the mosaic character of the variegated leaves of tobacco in the Dutch plantations but in his later studies on the cultivation of tobacco in Cuba, did not mention the disease which then was called “Rost.” At present the disease may exist in any country grow- ing tobacco and, accordingly, has received any number of names. Thus Hunger mentions that in Holland it is not only called “Rost” but in places “Bunt” or “Faule.”’ In Germany the name “Mosaikkrankheiten” holds good. In places it passes as “Mauche ;” in France it is called “La Mosaique” or “Nielle” or “Rouille blanche,’ in Hungary it is called “Mozaikbetegsege’’ and the Tartars in southern Russia call it “Bosuch.”’ In Italy it is described under the name “Mal de Mosaico, or “Mal della bolla.” In America, in the northern states, it is called “Calico” or “the Frenching disease ;” in the southern states, on the other hand, “Brindle” or “Mongrel disease”’ The plantations in Java, Borneo and Sumatra also suffer heavily. The Javan- ese call the disease “Poetih,’ while it is known in Deli by the Chinese name “Peh-sem’’®, ; The mosaic disease may at present be considered the most dangerous disease of the tobacco plant. This explains why it has been thoroughly studied recently from several points of view but the results are often con- tradictory. While some investigators, retaining the old theory with great tenacity, wish to find microbes and think they have found them, others defend the theory that an infection disease is present here, the cause of which must be sought in inexpedient enzymatic activity. The diversity of opinion is explained partially by the fact that different phenomena have been included under the mosaic disease which do not belong together. On the other hand, however, the disease can actually appear under different forms. We follow Delacroix* in describing its symptoms. He distinguishes two stages :—1, loss of color; 2, changes in the form of the diseased leaves. In the first groupyof symptoms, the edge of the leaf shows sharply outlined, various colored spots of a faded green, which shades off into a whitish color but not into a yellow green as in chlorosis; the pale green parts have spots of dark green color, which is even darker than that of the normal leaf. The differences in color become more apparent when the leaf is held 1 Mayer, Adolf, Die Mosaikkrankheit des Tabaks. Landw. Versuchsstat. 1886, Vol. XXXII, p. 450, Part III. 2 Hunger, F. W., Untersuchungen und Betrachtungen tiber die Mosaikkrank- heit der Tabakspflanzen. Zeitsch. f. Pflanzenkrankh. 1905, p. 257. 3 Hunger, loc. cit. 4 Delacroix, Georges, Recherches sur quelques maladies du Tabac en #rance. Paris 1906, p. 18. Extrait des Annales de l'Institut national agronomique, 2 ser., Vol. V. , 686 against the light, and, by feeling the leaf, it is noticeable that the dark green places are somewhat thicker than the pale ones. Before Delacroix, Iwan- owski* had already emphasized the fact that the lateral shoots, developing from the axes of diseased leaves, have the mosaic disease. This circum- stance is very important and characteristic of the disease in which the loss of color occurs in the young leaves; as a rule, mature leaves do not be- come diseased. Often the dark green places become somewhat convex so that the surface of the leaves is somewhat wrinkled; in other, and rarer cases, a reduction of the leaf surface sets in which can increase to such an extent that, on the whole plant, only the mid ribs are present but no blades. This latter characteristic has been mentioned by Heintzel? and Iwanowski, but, according to Hunger? it is not typical of the disease, for he had also observed it in Deli in healthy plants on open ground. Therefore, in the mosaic disease, we find the same characteristics as in albinism ; a sharp delimitation of the spots, a greater thickness of the green places, and, at times, a reduction of the leaf surfaces, which, in the varie- gated parts, remain small. This can also be transmitted artificially and probably follows the same paths, i. e., the leptome. The only difference is that the mosaic disease can be transmitted considerably more easily. Every particle of sap which falls from a diseased plant into an injury in a healthy one is enough, under certain circumstances, to cause infection. We will cite, as example, the description of an infection experiment made by Koning*. On the 5th of July he cut the stem of a perfectly healthy plant as far as the vascular bundles and inserted in the cut a small piece of the spotted leaf from a diseased plant. On the 20th of July a dark fleck could be seen near the edge of a young leaf, between the veins. In the course of the next few days, specks appeared also on the other young leaves while the leaf itself took on “an uneven, irregular appearance due to the increase of the palisade tissue.” The edge of the leaf appeared in places to be strangulated, or slightly lobed. Later these spots dried up, after having assumed a reddish brown color. Koning perceived concentric zones in the larger spots, of which the outermost zones were the darkest. Not infre- quently he found that whole pieces had fallen out of the leaf. The latter characteristics are not mentioned by other observers, which fact supports our theory that the disease can present different aspects in different places and in different varieties of tobacco. Koning gives only scanty notes on the anatomy of the diseased leaves. In the very youngest stage of the spots, where no differentiation of palisade and spongy parenchyma has set in, dark stripes appear between the cells which represent strikingly large, air-filled intercellular spaces. These are 1 ITwanowski, D., Wher die Mosaikkrankheit der Tabakspflanzen. Zeitschr. f. Pflanzenkrankh, 1901, p. 1 ff. ; : ; 2 Heintzel, Kurt, Kontagijse Pflanzenkrankheiten ohne Mikroben mit beson- derer Beriicksichtigung der Mosaikkrankheit der Tabaksblatter. Inaug.-Dissert. Erlangen 1900. 3 oe: Git, p: 2TA: ; Saye 4 Koning, C. J., Die Flecken- oder Mosaikkrankheit ,des holl4ndischen Tabaks Zeitschr. f. Pflanzenkrankh. 1899, p. 65. 687 retained in the advancing development of the tissue. No change can be observed at first in the epidermis. It shrivels later, becomes brown and dry when the chlorophyll has disorganized in the underlying tissue and the cells dry up. In extensive plantations the infection of the plants usually takes place through contact with the hands of laborers who produce wounds when thinning out the plants and otherwise working among them. The touching of such places with fingers covered with sap from diseased plants is enough to inoculate the majority of the healthy plants. The process has often been tested experimentally. In an experiment made especially for this purpose in Holland, Koning determined 80 per cent. of disease. The disease, moreover. is not restricted to tobacco, for Woods! had already reported that he could call forth similar phenomena when pruning tomato plants. Hunger? showed as an example that, in the same plant species, different varieties behaved differently according to their origin. He found in direct experiments with the heads of plants in Buitenzorg that all the shoots (lateral shoots) of 50 examples raised from American seeds had the mosaic disease. Of 25 plants grown at the same time from German seed g were diseased. On the other hand, the shoots of the 25 specimens raised from Indian seed showed no change. In speaking of the cause of this disease, we have already mentioned that part of the observers assume the presence of micro-organisms without having seen them. Iwanowski, in fact, describes a specific bacterium, but Hunger found, in subsequent investigations, that the alleged organism dis- appeared from the cell with the use of the chloral hydrate phenol mixture. We can, therefore, say that no parasitic organism is known, as yet, for the typical mosaic disease, or, rather, the majority of exact observations lead to the theory that a physiological disease is concerned here, the transmission of which takes place by means of carriers which, advancing in the infected organism, cause, in the existing normal group of substances, the same changes in the arrangement which produce the disease and in this way the spread of the disease. The different degrees of susceptibility of the differ- ent varieties—those with thick leaves being much more resistant than those with thin leaves—prove that some predisposition must exist. The highly prized Deli tobaccos (those with the tenderest leaves) suffer most. The influence of cultivation is shown by the fact that virgin soils give decidedly smaller percentages of sick plants than those already used repeatedly for the cultivation of tobacco (cf. Hunger’s field experiments) *. Two points of view are now held by the investigators who do not rec- ognize microbes as the cause of the mosaic disease. One group believes that the plant produces a poison, a virus, which is capable of producing the same poisonous substances in the cell content of an inoculated plant, thereby 1 Woods, A. F., Observations on the Mosaic disease of Tobacco. U.S. Dept. of Agriculture, Bull. No. 18, May, 1902. 2Z- TOC “Citi. D. 126s 8 Zeitschr, f. Pflanzenkrankh, 1905, p. 289. 688 causing the disease. Beijerinck' appeared first among those who hold this opinion. In 1898 he described a “contagium vivum fluidum” as the cause. Hunger says further’, “I consider the virus of the mosaic disease to be a toxin which is always produced in the tobacco plant during the metabo- lism of the cells but, in normal cases, exercises no effect, while it accumu- lates when the metabolism is too strongly increased and then causes disturb- ances such as the mosaic form of variegated leaves.” I assume that the toxin of the mosaic disease, which is produced primarily by external stimuli, is capable, when penetrating into normal cells, of exercising a physiological contact effect with the result that the same toxin is formed there secondar- ily. In other words the toxin of the mosaic disease possesses the peculiarity of acting as a physiologico-autocatalytic agent. In this way the virus can be make its way independently throughout the tobacco plant and, reaching the paths leading to the meristem, can exert its influence there on the young structures. ‘This explains the capacity of the diseased substance for in- crease. ‘This capacity does not depend on the active reproductivity of the virus itself but simply arises from the passive reproductive power of the living cell substances.” In contrast to the theory of poison we represent a second theory and call attention to the experiments of Pantanelli and others who have proved a change in the amount and action of the enzymes. Heintzel® says (1899, p. 45), “The enzyme which causes the mosaic disease may, therefore, be considered an oxydase.” Accordingly, the cause of the mosaic disease would be present also in a healthy plant and would have an abnormal action only under special circumstances. Woods‘ expresses exactly the same theory since he thinks only certain conditions are concerned under which the oxidizing enzymes become effective —“either become more active, or are produced in abnormally large quantities.’ The condition of matters at present is still uncertain and forbids a closer examination of the relations. For the theory which we advance and have described in the first section of this chapter, the question is less important, whether an increase of the oxydases actually takes place, or whether a decrease of the reducing sub- stances, always accompanying the oxydases, whereby the same amount of oxydase has an increased activity. Hunger has actually proved that the leaf with the mosaic disease contains less reducing and tannic substances than do healthy tobacco leaves®. A scantier sugar content has been proved in the diseased leaf, corresponding to a lack of chlorophyll; besides this, 1 Beijerinck, M. W., Over een contagium vivum fluidum als oorzaak van de Viekziekte der tabaksbladen. . Koninkl. Akad. van Wetenschappen te Amsterdam. Nov. 1898. Uber ein Contagium vivum fluidum als Ursache der Fleckenkrankheit der Tabaksblatter. Centralbl. f. Bakeriologie 1899, Part II, No. 2, p. 27. 2 140G. Cit.,p, 296: 3 Heintzel, Kurt, Kontagidse Pflanzenkrankheit ohne Mikroben, mit beson- derer Beriicksichtigunge der Mosaikkrankheit der Tabaksblatter. Inaug.-Dissert. Erlangen 1900; cit. by Hunger, loc. cit., p. 269. 4 Woods, A. F., The destruction of chlorophyll by oxidizing enzymes. Centralbl. f. Bakt. 1899. Part II, Vol. V, No. 22, p. 745: 5 Hunger, F. W. T.. Bemerkungen zur Wood’schen Theorie tiber die Mosaik- krankheit des Tabaks. Bull. d. l’Inst. Bot. de Buitenzorg 1903, No. XVII. 689 less free organic acids are found’. Accordingly, the parts suffering with the mosaic disease lack the ability to form sufficient reserve substances; and thus the mosaic disease, which, according to Hunger*, may also be transmitted without the existence of any injury, simply by contact with the hand, or, in grafting, be transmitted to the stock, belongs under albinism. While we still have no reason for restricting the last named phenom- enon, because the white variegated plants, in spite of their greater sensitive- ness, form desirable specimens for our gardens, yet, the need of earnest regulations for combatting the mosaic disease, is most imperative and these have often been tried. According to Koning liming the soil has proved to be the best method. Hunger also proved good results by fertilizing with bone meal and gives warning primarily against an excessive chemical ferti- lization. In my opinion the disease is a result of inbreeding, which can be overcome successfully by decreasing the supply of nitrogen and by increas- ing the lime. Wood says*, “Overfeeding with nitrogen favors the development of the disease and there is some evidence that excess of nitrates in the cells may cause the excessive development of the ferments causing the disease.” The choice of seed also deserves especial attention as is evident from the statements of Bouygeres and Perreau*. These investigators took seed from plants, in the midst of a diseased field, which up to the time of har- vesting had remained free from the mosaic disease. They obtained 98 per cent. of healthy plants. These were, at any rate, capable of being infected in wounds brought in contact with parts having the disease. Special con- sideration should be given primarily to the soil. In earth, on which tobacco had been grown for some time, healthy seed very easily became diseased’. Pox oF TOBACCO. We have mentioned already, in discussing the mosaic disease, that other phenomena of discoloration have often given rise to much confusion. An example of the latter is furnished by the pox disease. Iwanowski and Poloftzofi® have called attention to the difference between this and the mosaic disease. For three years they studied this disease in Bessarabia, having been commissioned by the Russian Department of Agriculture. According to Hunger’, the disease manifests itself in the appearance of 1 Hunger, De Mozaik-Ziekte bij Deli-Tabak. Deel I. Mededeelingen uit S’Lands Plantentuin LXIII, Batavia 1902. 2 Hunger, On the spreading of the Mosaik-disease (Calico) on a tobacco field. Extr. Bull. d. ’Institut Bot. de Buitenzorg 1903, No. XVII. 3 Observations on the mosaic disease of tobacco, Washington 1902, p. 24. 4 Bouygeres et Perreau, Contributions a l’étude de la nielle des feuilles du tobac. Compt. rend, 1904, CXXXIX, p. 309. 5 Behrens, J., Weitere Beitrige zur Kenntnis der Tabakspflanze. Landwirtsch. Versuchsstat. 1899, p. 214 ff and 482 ff. 6 Iwanowski und Poloftzoff, Die Pockenkrankheit der Tabakspflanzen. Mém de l’Acad. Imp. de St. Petersbourg 1890, sér. VII v. XXXVII. 7 Hunger, Zeitschr. f. Pflanzenkrankh. 1905, p. 297. Here also pertinent. bibliography. 690 numerous small white specks at times of great drought, while in Deli the mosaic disease is observable immediately after sharp rainstorms. The cause is looked fer in conditions similar to those in the mosaic disease. WHITE Rust oF TOBACCO. A further phenomenon has been confused with the mosaic disease which is called “White Rust.’ Delacroix: has called attention to the fact that, in this the mature leaves, and not the young ones, become sick first. The spots are more numerous but are smaller and stand out in sharp relief. Ultimately they are bounded by a cork layer. The cause is said to be a micro-organism, Bacillus maculicola. THE DISEASE OF THE PEANUT IN GERMAN-EAST AFRICA. According to Karosek? Arachis hypogaea, one of the most important cultivated plants of the East African colony, is in general but little attacked by disease. In the neighborhood of Tanga and Lindi, however, a phenom- enon has now appeared to a considerable extent which recalls the mosaic disease. The leaves, blossoms and fruit remain small, the yield is scanty; whitish, irregular spots appear on the leaves, deforming them somewhat. The leaves finally become brown and die. Fungi have been found and any lack of nutrition is out of the question. THE SHRIVELLING DISEASE OF THE MULBERRY. This disease, at present widely distributed through Japan, which surely will be found later in Europe, has only been observed more exactly for possibly the last twenty or thirty years and has been studied earnestly only during the last ten years. According to Suzuki’, whose description of the disease we follow, it is called Jshikubyo or Shikuyobyo in Japan. Like the mosaic disease, this shrivelling disease also occurs most extensively in the tender leaved and quick growing varieties. Within the same cultural varieties the individuals suffer most strongly which receive too much liquid fertilizer, while trees planted in poor soil, or in mountainous regions, are almost free from it. The fact that the disease became noticeable at about the time when the so-called “pruning method” was universally introduced into Japan is of especial importance. This method consists in the cutting down of the - trunks, or branches, at the time of the most luxuriant leaf development (May to June), close to the soil when the plant is three years old. The stock at once produces new, luxuriant shoots which by September have become 5 to 6 feet tall. These branches, in the following summer, are cut back again, either close to the soil or several feet above the surface. Speci- mens, which have been cut back for a long time, suffer less from the disease 1 Delacroix, G., La rouille blanche du tabac et la nielle, etc. Compt. rend. 1905, CXL, p. 675. 2 Karosak, A. Eine neue Krankheit der Erdnitisse in Deutsch-Ostafrika. Gartenflora 1904, p. 611. 3 Suzuki, U., Chemische und physiologische Studien iiber die Schrumpfkrank- heit des Maulbeerbaumes, eine in Japan sehr weit verbreitete Krankheit. Zeitschr, f. Pflanzenkrankh. 1902, p. 208. 691 and it is absolutely unknown in regions where the plants, under the old cultural method, have not been cut at all. Consequently, we may maintain with certainty that a phenomenon resulting from intensive cultivation is concerned here. The fact that the plants remain healthy, which were cut back in autumn or the early spring before the opening of the leaves, favors the theory that this cutting during the time of making growth is the cause of the shrivelling disease. Diseased plants can be cured if left unpruned for several years. The first indication of the disease appears generally when the young branches, breaking out from'the stump of the trunk, have reached a height of one foot. First of all, the uppermost surfaces shrivel or show other phenomena of weakness. This change advances gradually downward, while the leaves turn yellowish or dark green, or even can retain their normal color. This usually sets in slowly since, in the first year, only the upper leaves of some shoots become diseased. In the course of time, the condition so spreads that the tree dies. There are, however, also acute cases in which all the leaves shrivel at the same time in one year. The branches of the diseased plants are usually very thin and develop very numerous side branches and leaves; they droop at times and lose their stiff- ness. The roots begin to decay. . Naturally, parasites have often been held responsible for this disease and the phenomenon has been declared to be the result of a parasitic decay of the roots but the roots are demonstrably healthy in the first stages of the disease of the aérial parts; besides this, it seems very remarkable that a parasite always seeks only the trees treated with the pruning method. With due consideration of the preceding facts, one is forced to the con- clusion that a continued disturbance of equilibrium in the nutritive processes must be the cause here. This is confirmed by Suzuki’s numerous analyses. He found, for example, in the average from ten experiments that in leaves of plants suffering from the shrivel!ling disease, when the content of the healthy leaves is set at 100, the water content is 94.7 per cent.; the dry substance 116 per cent. In 100 parts dry substance the content is :— (normally valued at 100) ROLE Ulery eee eens Pot Ein S VC! 5. pt eee 81.8 per cent. LD MS Ai peters Ons re Uc Tet gee |e a a PE 86 i LEU ie hike tO TEM We ore rat Wy See hs ee e o RN RR See Extractive substances free from nitrogen...... 120 a LEA SS OE I aR od a ee a Pe gI vs Seale inith@ meter, seen gee ee vss. oa) wiegennne eetah Ol). mibtuminerd: nitrogen, 26k on. et De ee. 86.05 5. Non-albuminesd nitcacen <9 2. .2Gisia eye i ance 66.6 “ In 100 parts ash content. (normally valued at 100) lO leit caro tonteesecote is Toei ericemt. | 4k Oban cuisine 3 92.3 per cent Sp Ol packet an ee eee O72 4% AG) Wel ted, OS eee LOGS) ae 1a (2) oe oa Tn RA EOROe |: SUI OO os: A AR ae 1200957 692 Therefore, a greater abundance of ash in proportion to the organic substances produced, as has been emphasized already as typical for all defective plants. The characteristic of the shrivelling disease of the mulberry is a con- gestion of starch in the diseased leaves and a very scanty development of the wood body, especially of the conducting elements, the sieve tubes. Be- cause of the scanty number and small breadth of the lumina of these elements, only a very slow transportation of the assimilated material (here especially sugar) can take place. Consequently the continued dissolution of the starch is prevented’. Besides these anatomical conditions, chemistry now proves the presence of an abnormally large quantity of oxydases and peroxydases. According to Woods, it is very probable that the oxydases not only destroy all the chlorophyll but also prevent diastatic and proteo- lytic action. On this account, they might be the cause of the delay in the transportation of the starch and nitrogen compounds. At any rate, Shibata? maintains, as a result of his experiments, that the diastase action is not pre- vented by the oxydase and that a further production of the enzymes would be caused by the entire elimination of the elaborated materials. Later experiments must make clear which of these theories is correct. The fact is sufficient for us here that the whole amount of the reserve substances is exhausted in the sick plants*. This is shown also in the scanty filling with starch of the bari on the branches and roots and of the dormant buds, and manifests itself also in the decrease of root pressure and the transpiratory intensity (Miyoshi). It is now clear that if a plant is continually forced to use its reserve material by the removal of its foliage, it does not have time enough to mature the new growth, i. e., to deposit sufficient starch, albumen and cellulose in these organs. The curing of this disease will lie in a return to the normal fall pruning. As soon as branches of diseased plants have developed their own roots by layering, they develop normally as Suzuki has shown experimentally. Besides this, very similar phenomena of disease also occur in the tea plant as soon as the picking of the leaves is carried on irrationally. THE SEREH DISEASE OF THE SUGAR CANE. At present the Sereh disease, which appeared in Java in the 80’s of the last century and is advancing from the West to the East, is, indeed, the most greatly dreaded disease of the sugar cane. It has now been observed also in Réunion, Sumatra, Borneo, Malakka, the Mascarrean Islands, and in Australia*. According to Kriiger’, whom we follow first of all, the name 1 Miyoshi, M., Untersuchungen tiber Schrumpfkrankheit (“Ishikubyo”) des Maulbeerbaumes. II. Journ. Coll. Sc. Tokio 1901, Vol. XV. 2 Shibata, K., Die Enzymbildung in schrumpkranken Maulbeerbiumen, The Botanical Magazine XVII, 1903. 3 Suzuki, loc. cit., p. 277. 4 Cit. Zeitschr. f. Pflanzenkrankh. 1901, p. 297. 5 Kriiger, W., Uber Krankheiten u. Feinde des Zuckerrohrs. Ber. d. Versuchs- irae ifr paucker cone in West-Java, Kagok-Tegal. Dresden, Schénfeld’s Verlag, Pps aLze: PART IX. MANUAL OF PLANT DISEASES BY PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Prof. Dr. G. Lindau And Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History of Berlin in Hamburg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT vitae’ ig ’ : ~ Ac i 4 : , 1 rte fa Pet ee ay uw an , > 4 Pa . rs \ i @ ee ~~ . 4 Copyrighted, 1920 By ries FRANCES DORRANCE ©0!.4570990 THE RECORD PRESS Wilkes-Barré, Pa. nue -6 1920 693 originates from the Javanese name for Andropogon Schoenanthus (Jav. Seréh), grown extensively in gardens there. This grass forms unusually greatly branched bushes. In its most highly developed form the disease of the sugar cane also appears in an excessive formation of short lateral shoots which make the plant look bushy. The root system is poorly developed and only slender roots spread out in the soil; the majority remain short and bushy, for their tips die and those formed anew fall victim to the same fate. Many parasites are found in the dead tissue; among these, Tylenchus Sac- chari Soltw. is the most common in Java. The internodes of the stem remain short; the eyes of the leaf axils swell up round, while, in the normal cane (with the exception of a few varieties) they lie flat like a shell in the small depressions on the stem. The growth of the main shoot is sup- pressed and, on this account, the lower eyes, especially those below ground, develop quickly. In the new shoots, however, the same process of sup- pression of the apical growth is repeated immediately as well as that of the breaking of the secondary axes. In this way the whole plant gets an obnor- mally bushy formation. The Javanese material, which I ordered for inves- tigation, at times showed such a ramification of the lateral axes on the upper, higher parts of the stem that groups, resembling witches’ brooms, were formed. All possible transitions between this bushy dwarfing and the slender normal condition are found in the different stages of the disease. As a result of the great shortening of the internodes, the leaves stand close to one another like fans. The leaf sheaths seem to enclose each other. In many cases, their death does not take place as it does normally by advancing from the edge towards the mid-rib, but conversely, and the result is that they remain for a long time on the stem and form nests for micro- organisms. Their color is usually darker than that of the normally dead leaves and while the latter are tough, the abnormal ones are more brittle and disintegrate easily. The intensive red colored vascular bundles are at once conspicuous in a cross-section through a node of the diseased cane. This coloring matter may be withdrawn with alcohol. The cell walls are frequently swollen out of shape and partially destroyed. This red coloring of the bundles occurs in cuttings and in older plants in the first stages. of the disease, so that it was thought that they should be emphasized as a characteristic especially deserving of consideration. We have observed this red coloring of the cell walls in many non- parasitic diseases of monocotyledons, and Busse' has been able to produce it artificially in the sorghum millet in German East Africa by painting the leaf blades with vaseline or paraffine oil. The color spread still further in the xylem parts of the vascular bundles and was traced by Busse to a dis- turbance in the respiratory process. We consider the red color to be a phenomenon of oxidation which indicates a functional disturbance in the con- 1 Busse, Walter, Untersuchungen iiber die Krankheiten der Sorghum-Hirse. Arb. d. Biol. Abt. f. Land- u. Forstw. am Kaiserl. Gesundheitsamte 1904, Vol. IV, Part 4, p. 319. 694 ductive system due to very different causes but especially frequent in root diseases. It appears also very clearly in the pineapple disease, in a parasitic disease of the sugar cane produced by Thielaviopsis ethaceticus which can be transmitted by cuttings. The greater the amount of sugar in the stem— this increases constantly from the base up to about the middle of the stem— the more easily the cuttings become diseased by the fungi?. The red color appears in the Sereh disease at times isolated in some nodes, while the fibro- vascular cords of the underlying internodes are still uncolored. It may be concluded from this that the disease represents a general ailment, a constitu- tional disease, which shows its first visible symptoms in especially weakened places. The cause of the disease has been sought in all kinds of influences; exhaustion of the soil, degeneration due to continual asexual propagation, abnormal atmospheric conditions, unsuitable fertilization, especially with peanut meal (Bungkil), too deep planting, or too high covering with earth, too early, or too late planting, and finally parasites. Among the latter, nematodes, fungi and bacteria come under consideration. The conclusions of one scientist contradict those of another. Thus, for example, Kriiger states that he has found bacteria in the ducts as a constant accompaniment of the disease, while Tschirch? considers it impos- sible that bacteria can be the cause of the disease and sees the initial stages in an injury to the roots. Benecke?® sides with Kriiger, Mobius* opposes the assertion of any existing degeneration and also seeks the cause in parasitic organisms. Ohl® perceives the cause of the Sereh disease and the disease of the coffee tree in Java, in which the leaves fall, to be the deforestration of the mountains and subsequent drought. Janse®, in the same way, traces the disease to a lack of water, since he thinks that the gummy obstruction of the ducts prevents conductivity. He connects the formation of the gummy substance with bacteria (Bacillus Sacchari). Went" considers the Sereh directly as a gummosis which arises from the co-operation of a parasitic root and leaf sheath disease and which may be propagated by cuttings. Wakker® considers the disease as a non-parasitic gummosis, associated with the excess of water which cuttings, developing during the dry monsoon, suffer in the following rainy period. 1 Cobb, N. A.; Fungus Maladies of the Sugar Cane. Rep. Exp. Stat. of the Hawaiian Sugar Planters’ Association. Bull. 5, Honolulu, 1906, Part 1, p. 218. 2 Tschirch, A., Uber Sereh, die wichtigste aller Krankheiten des Zuckerrohres in Java. Schweiz. Wochenschrift f. Pfarmazie 1891. 3 Benecke, Franz, Proefnemingen ter Bestrijding der ‘Sereh.” Samarang 1890. For further treatises by this author cf. Zeitschr, f. Pflanzenkr. 1891, p. 354, 361. 4 Mo6bius, M., Over de gevolgen van voortdurende vermenigvuldiging der Phanerogamen langs geslachteloosen weg. Mededeelingen van het Proefstation “Midden Java” te Samarang. 1890. 5 Ohl, A. E., Eene Waterstudie. Batavia 1891; cit. Zeitschr. f. Pflanzenkrankh. Vol. I, p. 365. 6 Cit. Zeitschr. f. Pflanzenkrankh, 1893, p. 238. 7 Went, F. A., Die Serehkrankheit; cit. Zeitschr. f. Pflanzenkrankh. 1894, p. 235 and 1901, p. 297. Re Pare J. H., De Sereh-Ziekte S. A. Archief voor.de Java-Suikerindustrie. 1 ; sworn 695 Thus the difference of opinion extends to the most recent times? with- out having led to any positive reconciliation. The reason probably lies in the fact that the characteristics given for the Sereh disease also occur in other diseases, as will be shown, for example, in the following section, and thus different investigators may have considered different forms of the disease. We will emphasize a few facts from positive results, i. e. that healthy cane can remain healthy in plantations suffering from the Sereh disease, and that diseased cane remains diseased in healthy fields. It should be added further that often wide bands along the edges of the fields appear diseased first, or only the edges themselves, and that the Cheribon cane, which tends to disease when planted in mountainous regions, has given healthy cuttings. Some cuttings are practically immune, while others are susceptible. Even the cuttings of the same variety from regions free from the Sereh disease at first remain healthy, even in infected regions. It is evident from this that the disease can scarcely be parasitic but falls under the group of the gum- moses. It can, therefore, not be contested that the bacterial gummosis conditions exist in the Sereh disease, just as in the rot of our sugar beets, but these forms also depend upon certain conditions of weakness of the plant body which we call displacement of the enzymatic functions. We consider the causes of the insufflcient ripening of the cane, i. e. non-deposit of reserve substances, cane sugar in this case, to be the inconsid- erate cultivation of sugar cane with an increased supply of fertilizer and water on heavy soil in enclosed positions, etc. Actually, the loss in the sugar content is uncommonly great in the Sereh disease. We are not in a position to determine the process which causes the lack of reserve substance. It is, however, a matter of indifference in judging of the disease, whether an excess of destructive enzymes is present or a para- lyzation of the constructive ones. The metabolic processes, leading to this lack of cane sugar, are naturally present in the whole plant no matter where they make themselves felt symptomatically. Therefore, each smallest part of the diseased cane, even if it shows no symptoms of the Sereh disease, is actually predisposed to it and even contains the carriers of the disease. Consequently each Bibit (cutting) from the plant having the Sereh disease is condemned to death as soon as it comes under conditions favoring the disease. It heals itself, however, and returns to the normal enzymatic activity on tracts of land where the Sereh does not break out. From this the best method is clearly the choice of varieties immune to Sereh or, at least, the cultivation of Bibits in open, mountainous positions and other localities which do not permit the disease to occur. Probably a change in cultivation takes place in such a way that only weak fertilizing and more porous soils, as well as open positions, are used in the cultivation 1 Hein, A. S. A., Hypothesen en Ervaring omtrent de Sereh ziekte. De Indische Mercuur. Amsterdam 1905; cit. Jahresber, f. Pllanzenkrankh. vy. Hollrung, Vol. VIII, 1906, p. 245. 696 of cane; these also cause a standstill in the Sereh disease in distinct centres of the disease. We believe also that the diseases termed the rusts of sugar cane belong here. Of these, we refer here to the Powdery Disease described by Spegaz- zini'. which occurs also with red spots and a gummy secretion but becomes noticeable because of its unpleasant smell. The base of the stem suffers especially. A bacillus (Bacillus sacchari) may be isolated from the gummy slime which requires an acid nutrient substratum and produces a protein decay which gives rise to the offensive smell of the diseased cane. This disease also occurs with Andropogon nutans. In regard to the production of the red color in the vascular bundles and of the gum in the sugar cane by micro-organisms, Grieg Smith’s? work is of especial importance. He found reddened vascular bundles in otherwise healthy cane as well as in the stems which had become gummy because of Bacillus vascularum Cobb. The red color was produced by the filling of the large ducts with a red gum just as in the Sereh and other sugar cane diseases. He found further a fungus, which produced a shiny, very scarlet color on nutritive media with dextrose but no gum, and gum bacteria in the diseased ducts, especially Bacillus Pseudarabinus n. sp. Bact. Sacchari (“this variety normally lives in the sugar cane”) and besides this Bacillus vascularum. On sheets of nutrient agar with laevulose, the fungus produces no coloring matter, but in combi- nation with Bacillus pseudarabinus a bright scarlet is produced and in com- bination with Bact. Sacchari, a rusty brown. It will be seen from these examples how the constitution of the sub- stratum is able to modify the parasitic activity and in what way, therefore, different aspects of disease are produced. —_ F 709 The gummosis becomes fatal for the tree when the gum centres make up a greater part of the trunk circumference. According to Flihlert lemons suffer most and sour oranges least. Cuttings seem to retain the germs of the disease, and in the same way, grafted specimens seem to give a higher percentage of disease than seedlings which-have remained ungrafted. Rich fertilization, heavy watering, clayey soils, increase the evil, which is said to increase also 1f cover crops, like pumpkins, beans, tomatoes, etc., are grown, which require heavy fertilization. Judging by the material to which I have had access thus far, I consider the disease of Citrus fruits to be exactly the same phenomenon as the exu- dation of gum in the Amgydalaceae. I consider the excessive addition of fertilizers rich in nitrogen, to be one of the momentarily most frequent causes, which play a brief role also in Germany for the pitted fruits in nurseries. Among the Italian authors, Peglion? shares the theory explained here. He calls attention to the fact that the cultivation of cover plants needing rich fertilization is injurious. Stable manure is not very suitable for Citrus. The fruit, to be sure, becomes large but remains thick-skinned and sour. BLACKLEG OF THE EDIBLE CHESTNUT. According to Gibelli® this disease is characterized by the appearance of wilted yellow leaves and small fruit, poor in sugar. In young trees the base of the trunk dries up, the bark turns brown, and its tissues contain ‘concre- tions of tannin as large as the head of a pin. Analyses show all the charac- teristics of plants growing poorly, 1. e. a large ash content in proportion to the dry substance. In the ash is found a scarcity of potassium and phosphoric acid and a considerable increase of ferric oxid. Because of the ball-like concretions, giving the tannin reaction, the disease seems to me to be related to the disease “Mal Nero” of the grape- vine (see page 219). Comes* describes this form as gummosis. According to Cugini’, this disease, because of which bud development is entirely retarded in the spring, or destroyed, is characterized by the appearance of black stripes and spots on the branches, petioles and ribs, tendrils, and stems of the clusters. The spots extend into the organs and, in fact, the trunk even to the heartwood. Besides this, the disease is characterized by the subsequent appearance of yellowish brown granules in the parenchymatous 1 Fhihler. Die Krankheit der Agrumen in Sicilien. Biedermann’s Centralblatt 1874, p. 368. 2 Peglion, V. La concimazione e le malattie nella coltura degli agrumi. Boll. di Entomol. agrar., ete. 1901, in Bot. Jahresber. 1901. I, p. 479. 3 Gibelli, La Malattia del Castagno; cit. Bot. Jahresber. 1879, II, p. 375. Gibelli ed G. Antonielli, Sopra una nuova malattia dei Castagni, ibid. Cugini, Sopra una malattia che devasta i castagneti italiani, ibid. 4 Comes, Ii Mal nero della vite. Portici 1882. Primi risultati degli esperimenti fatti per la cura della Gommosi o Mal nero della vite. Portici 1882. Sul preteso tannino scoperto nelle viti affette da Mal nero. Bot. Jahresber. 1882. 5 Cugini, Ricerche sul Mal nero della Vite. Bot. Centralbl. 1881, Vol. VIII, p. 147. Nuova indagini sul Mal nero della Vite. Bologna 1882. I] Mal nero della Vite. Firenze 1883, 710 elements of the trunk and branches. These granules often fill up the entire lumina of the cells and consist either of cellulose or of substances containing proteins. Cugini, who, morever, considers the phenomenon to be parasitic, also confirms the turning green of the blossoms and connects it with the disease. Differences of opinion prevail already among pathologists who have found parasites. Prillieux' considers Roesleria hypogaea as the cause, while Hartig? declares that this fungus is an accompanying phenomenon and that another, Dematophora necatrix is the real parasite. Later investigations, especially those made by Pirotta*, show that the above mentioned granules in the cells give the tannin reaction and arise directly from the starch grains. He found Rhizomorpha very frequently in the diseased roots, but not always; nevertheless, he does not consider this fact important enough to place the disease among fungus diseases. Comes showed that the granules in question do not represent accumulations of tannin but consist of a different ground substance (gum) which is only | saturated with tannin. GUMMOSIS OF THE FIG TREE. The disease of the fig tree (Marciume del Fico” of the Italians), which has been well known since the time of Theophrates, has been thoroughly studied by Savastano*, who recognized it as gummosis. This disease, to which old plants are more exposed than young ones, is found most markedly in the months of July, August and September when the leaves become yellow and fall, as does the fruit also. Although numer- ous fungi and even insects are found on the wilted and dead leaves (Fumago salicina, Tul, Uredo Ficus, Cast, Phyllosticta Sycophila Thiim., Sporodes- mium, Coccus caricae Fab.), these parasites should not be considered causes of the disease. Usually there is no change in the trunk and branches, but a change does occur in the root, where the chief seat of the disease should be sought. In a highly advanced stage the roots seem blackish up to the crown, They sometimes split open, but oftener decay. It is found in plants, raised from sprouts, that the seat of the disease may lie in the roots of the mother plant, from whence the further distribu- tion takes place in all directions, but especially upward. The outermost layer is the most diseased; only at times is the innermost layer destroyed to any great extent. When the destruction reaches the crown, the plant dies absolutely. When the disease appears, the cells and ducts are found filled with a substance which at first seems a lemon yellow and later a dark amber. At first the cell walls are covered with this and then the whole lumen becomes 1 Prillieux, La pourridié des vignes de la Haute-Marne, produit par le Roesleria hypogaea. Paris 1882. : 2 Hartig, R. Rhizomorpha (Dematophora) necatrix. Der Wurzelpilz des Weinstocks. Untersuchungen aus dem forstbotanischen Institute zur Mtinchen. 1883, III, p. 95. cit. Bot. Centralbl. 1883, No. 46 (Vol. XVI), p. 208. 3 Pirotta, Primi studi sul Mal nero 0 Mal dello Spaceo neolle viti 1882; cit. Bot. Jahresber. 1882. 4 Savastano, L. Il Marciume del Fico. Annuario della R. Scuola Sup. d’Agri- cult. Portici, Vol. III, fase. V, 1884, con 4 tav. cromot. (nach brieflicher Mitteilung). al filled with it. The starch disappears with the increase of these masses. Savastano observed, even in seedlings, a production of gum centres at the point where the young roots passed into the trunk and branches. I found similar conditions in the sweet cherry, which externally showed no trace of disease. Savastano found gummosis appearing also in the trunk and branches. He found a substance in its gum which seems to be similar to “Olivile” occurring in the gummosis of the olive. The gummosis of the trunk and branches starts in the gum glands found even in the roots of saplings. Only after the plants have become diseased with gummosis may the presence of Rhizomorpha be proved which other investigators have considered the causes of the disease. With the red discoloration of the walls, the paren- chyma cells of the roots undergo a process of humifaction in which the specific weight of the tissue becomes less and less because the organic substances disappear. A later work by Savastano' gives the results of comparative experi- ments with specimens of Amygdalus Persica and Amygdalus communis, Prunus Cerasus, P. domestica, P. inititia, P. Mahaleb, and P. Armentaca, as well as Citrus Aurantium, C. Limonum, C. vulgaris and C. nobilis, and also of Olea europaea affected by gummosis. The results show that the gummosis of the plants named has much in common with that of Ficus Carica. In all, the formation of gum centres either takes place as a result of injury, or without any external cause. If the wound is overgrown quickly and completely, the gum formed dries up, as a rule, into brittle masses and remains uninjurious for the surrounding tissue. If, on the other hand, moisture is present on the wounded places, the gum remains soft and is easily carried over the surfaces surrounding the wounds, which also succumb to gummosis. THE EXUDATION OF MANNA. In many plants, instead of gum, a hard, clear substance containing sugar comes from the bark of young trunks and branches, and is called Manna in trade. The liquefaction product contains Mannit which, when extracted with alcohol, can be obtained in fine white silky crystals, tasting slightly sweet, and may also be formed artificially from different sugars. Investigations of the Manna exudation were begun by Meyen’. According to him, the large amounts of Manna, which come from Italy, are obtained artificially from a kind of alder, the Manna Alder, by making incisions in the bark toward the end of July. From these incisions the Manna flows gradually as a thick,sweetish juice, hardening in the air. RESINOSIS. The exudation of resin (resinosis) is for conifers what exudation of gum is for the Amygdalaceae and the Manna exudation for the Oleaceae. 1 Gummose caulinaire dans les Aurantiacées, Amygdalées, le Figuier, l’Olivier et noircissement du Noyer. Compt. rend. I, Decebre, 1884. Reprint. 2 Pflanzenpathologie, p. 228. 72 It sometimes occurs in the wood and sometimes attacks the parenchyma and bast cells of the bark. The first stages of the disease are found in the resinosis of the wood; the mature condition consists in the formation of large quantities of uniform resin masses in cavities in the trunk and branches, which are usually called resin boils. It is well known that resin in the cell contents normally occurs in the form of drops or, as in the glue mats of many wood buds, in the intermediate lamellae of the cell wall, or finally, as in our pines and spruces, in definitely distributed, peculiar resin canals. The contents of many parenchyma cells near the resin canal show resin drops and starch grains, of which some not infrequently are provided with a resin coating. The immediate surroundings must necessarily furnish the sub- stances which fill the large resin pockets. Whether this material is trans- ported in the form of resin, as N. J. C. Muller’ assumes, or in the form of some other compound and is only developed into resin where it is found as such, which theory Hanstein? is inclined to believe, is of little importance for our consideration. In this we have to maintain that the formation of considerable amounts of resin and gum is possible only through the transfor- mation of a plastic substance, flowing toward those places where the liquefaction takes place, i. e. a positive loss of sap. To this it should be added for resinosis, as for gummosis, that the existing plant substance, in the form of wood and bark tissue and of starch grains, succumbs to lique- faction and that, in this way, considerable material is lost. According to investigations made by Karsten* and \Wigand*, the wood at first seems resiniferous, i. e. saturated with resin and balsam. In most of the cells of this saturated tissue, the resin appears as a wall coating, or as drops which have spread together until the cells seem completely filled with the mass. The walls of the cells, originally thick, become thinner and thinner in the same degree as the amount of resin increases within the cell, until, finally, only a fine outline is left, which is gradually lost in the mass of resin. As in gum exudation, the medullary rays also seem to be longer resistent, since they are clearly seen to extend into the uniform resin mass of the dissolved wood cells surrounding them. For complete analogy in the two processes, there is lacking only the proof that, in the exudation of resin, an abnormal wood parenchyma is formed, which undergoes absolute resinosis. 1 Miiller (Uber die Verteilung der Harze usw. in Pringsheim’s Jahrb. f. wiss. Bot. 1866—67, p. 387 ff) says the great amount of resin in the resin ducts cannot have reached that place except by penetrating many cell walls. He finds the cell walls to be permeable for resin. Thin cross sections of pine wood left lying for some time in water showed that all the resin in the cell walls has been replaced = oy eraiaeeun (Uber die Organe der Harz- and Schleimabsonderung in dem Laub- knospen. Bot. Zeit., 1868, No. 33 ff.) speaks of the occurrence of resin first in the grooves of secretion cells as small bands between the cuticle and the cellulose mem- brane. This is undoubtedly an important reason for assuming that ‘‘the resin, which occurs in the form of intermediate wall layers, first assumes its real character after it has passed through the cell wall in another form and been deposited as an inter- mediate layer.” 2 Karsten, H. Uber die Entstehung des Harzes, Wachses, Gummis und Schleims durch die assimilierende Tatigkeit der Zellmembranen. Bot. Zeit. 1857, p. 316. 4 Wigand, Uber die Desorganisation der Pflanzenzelle. Pringsheim’s Jahrb. f. wiss. Bot. “Wol, TLE, sp, 165. | 713 ’ It has often been observed that the starch grains in resinosis succumb to liquefaction just as in gummosis. Starch certainly furnishes a large part of the resin in the exudation. Wiesner! states, for example, that resin bodies exist within the medullary ray cells of foliage trees and possess the structure of the starch grains. These rarely turn blue with the use of pure iodine but do so more often with iodine and sulfuric acid. With the use of ammoni- acal cuprous acid they give the cellulose reaction ; they react to ferric chlorid like tannin. Wiesner, therefore, concludes from his investigations that a large amount of the resin, occurring in nature, arises from starch grains themselves, or from starch grains which have been changed into tannin. He considers the tannin to be a connecting link between the cellulose and resin. We find in Nottberg’s? very thorough work on resin pockets the proof that even in the exudation of resin an abnormal parenchyma wood is formed which succumbs to resinosis and liquefaction. Nottberg proves that, as a result of any injury, whatever, which extends to the cambium, this responds with the production of a “tracheidal parenchyma” which gradually passes over again into the normal tracheids. The tracheids of the sap wood which, as a result of the injury, come into contact with the outer world, stop up their lumina with a mass resembling wound gum, which is insoluble in alcohol but dissolves after treatment with Schultz’s mixture. Usually res- inosis occurs at the same time in the wood body. The different cells of ‘ E ; Fig. 157. Cells of the tracheidal paren- the diseased parenchyma immediately chyma of Pinus Strobus with the resin- after their production begin to form iferous layer rsg; ht resin drops. (After : : ; Nottberg.) resin internally (resin cells). The membranes of the new cells of the tracheidal parenchyma liquefy very early. The unthickened elements, on the other hand, as long as they are retained, constantly show only the cellulose reaction. In the resin cells a definite layer may be recognized in which the resin is formed (resinogenous layer, Fig. 157). Nottberg, from whose book the figure is taken, leaves undecided what this resinogenous layer is; ‘‘a developmental product of the membrane, or of the cyptoplasm.” The pathological formation of resin may be considered the most exten- sive process of liquefaction at present known in the vegetable kingdom. It existed in the tertiary period as well as now, for Conwentz states in his monograph on the Baltic Amber trees (Pinus succinifera, Conw.), which has excellent illustrations, “there was scarcely one healthy tree in the whole 1 Sitzungsbericht d. Akad. D. Wissensch. zu Wien, Vol. 51. 2 Nottberg, P. Experimentale Untersuchungen uber die Entstehung von Harz- gallen und verwandter Gebilde bei unseren Abietineen. Zeitsch. f. Pflanzenkr. 1897, p. 133 ff. Hier auch weitere Literatur. 714 amber forest; the pathological condition was the rule; the normal one, the exception.’ We cannot better present the processes of resinosis than by showing copies of the amber sections which Conwentz has reproduced (Figs. 158-161). Just as at present, we find that the process of resinosis began as follows: —resinosis and liquefaction of the membranes, and finally of the whole cell are eg ee Ce Al CY Fig. 158. Process of turning to resin, beginning with the formation of a lysigenous resin canal in the wood. 205:1. (After Conwentz.) oe 2 ® inn Peat ae Pas) Fe. toe Boek the Fig. 159. Horizontal section. In the summer wood of an annual ring is a group of abnormal wood parenchyma Cells (P). 56:1: The holes in the tissue were produced in sectioning. (After Conwentz.) together with its contents, set in in different groups between two medullary rays (Fig. 158). No anatomically different tissue is necessarily present here, but, in the majority of cases, such an one is present and in fact in the form of wood parenchyma which develops in tangential strips. Conwentz 1 Conwentz, Monographie der baltischen Bernsteinbiume, Danzig, 1890, p. 145. 715 describes these strips (Fig. 159) in the summer wood. Up to the present I have found them predominantly in the spring wood of our trees so that a new annual ring begins at once with the abnormal wood, or after only a few cell rows. I trace the production of these strips back to a transitory weakening of the bark tension (see Frost Phenomena). This abnormal wood parenchyma is shown in a complete stage of resinosis in Fig. 160. Masses of resin, or rather:amber, already produced, can push out the bark away from the oldest part of the trunk. Conwentz found such bark ele- ments in so good a state of preservation that he still could prove their nucler, (Pie. 161.) Nottberg found, in the liquefaction of the solid tracheid parenchyma, that the tertiary membrane was retained longest; this may be observed also in the spreading of the gum centres of the cherry. Fig 160. Horizontal section with abnormal parenchyma wood (P), which has begun to turn to sugar. The abnormal tissue lies in the summer wood. J is the edge of the annual ring. 210:1. (After Conwentz.) Nottberg distinguished good and evil wounds according to whether the wound heals at once or affects the surrounding tissue. It should still be noted that the trees, of which the wood normally has no resin canals at all (the white fir), are found to abound in resin canals after injury, especially in the edges of the callus. These investigations have been confirmed by v. Faber’, who also emphasizes the fact that the pathological resin canals are formed schizogenously. They anastomose in a tangential plane and form a connected network, while their open ends extend into the wound. Above these the resin canals are more abundant and longer than they are below them. In opposition to the statements that the cause of resinosis may always be sought in wounds, I must maintain, as in gummosis, that the processes of liquefaction can also arise autogenously, without wound stimulus. I have observed this in seedlings of pines from heavily manured nurseries, 1 y. Faber, HE. V. Experimentaluntersuchungen tiber die Entstehung d. Harz- flusses bei Abietineen. Dissertation. Bern 1901. 716 and found similar cases likewise in older plants of Pseudotsuga Douglasi, Abies Fraseri and Abies concolor, which showed swellings of the bark. These could be proved to be a lysigenous widening of schizogenous resin canals. The trees stood on moist, marshy soil which had been heavily manured at intervals of two or three years. Recently, I have had opportunity to observe resinosis as a constitutional disease, 1. e. as the manifestation, even in old trees, of a tendency throughout the whole plant body, to form resin excessively. I have distinguished this universal disease, as “chronic resinosis,’ from the “acute resinosis” pro- duced locally as a result of wound stimulus, and remaining localized, which is connected with the exudation of profuse amounts of resin’. Accordingly, in the future, a chronic and an acute gummosis would have to be distin- guished from one another and in the latter, the treatment of the _ wounds with vinegar, already recommended, might be success- ful. FORMATION OF RESIN IN DICOTYLEDONOUS PLANTS. The production of resin and gum resin in dicotyledonous plants is found to be parallel to the processes described in the preceding section. Svendsen* found that the gum resins of Fig. 161. Group of parenchyma cells from Seyh ve Liquidamber, Toluifera, the outer bark which has been completely 4 separated from the central wood cylinder by etGs, Jane pathological products, the turning to resin of an annular, abnormal produced as a result of injury. still be discerned in ere cells. (After After every injury, which ex- Di ere tends as far as the cambium, wound wood is formed which is distinguished by its tracheidal, parenchy- matous character and which gradually passes over again into normal wood. The processes, therefore, are everywhere the same, just as was described and illustrated under injuries due to the frost. The wound stimulus makes itself felt in the old wood by a stoppage of the ducts with tyloses, or the closing of them by Bassorin. The new wood, which is formed about the wound and at first is parenchymatous, has resin canals produced schizogenously; and widening lysigenously. The resinosis thus attacks the wood parenchyma, with the exception of considerable parts of the medullary rays, and con- tinues later in the bark, where it becomes noticeable within the bark rays; a fact which should be emphasized. In dicotyledons, as in conifers, the patho- 1 Landwirtschaftliche Jahrbiicher 1908. Svendsen, Carl Johan. tjber den Harzfiuss bei den Dicotylen, speziell bei Styrax, Canarium, Shorea, Toluifera und Liquidambar. Archif for Mathematik og Naturvidenskab. Kristania 1905, Voi. XXVI, No. 13. ZAZ logical formation of resin is perfectly independent of the presence of normal resin canals. The conditions seem to be more complicated in Peru and-Tolu Balsam. Therefore, so far as we can examine the pathological formation of resin, it corresponds perfectly to gummosis and, therefore, the same theories, which we have expressed earlier, hold good for it. It is not the wound stimulus in itself which causes the liquefaction of the solid tissues, but enzymatic actions, which we cannot determine at present, manifested in the result that scattered tissue groups fail to develop normally and dissolve because of oxydation. These processes can be introduced by wounds but also arise from a changed nutrition. They are dependent upon a definite develop- mental phase, i. e. the time of the sprouting of the trees. Centres of lique- faction, already existing, may be increased by the transmission of their enzymes to normal, permanent tissue. Supplementarily, we will cite a number of phenomena, some of which belong directly to degeneration due to gummosis, and others belong here because we conceive them to be the results of enzymatic disturbances of equilibrium. Analogous to the exudation of gum is the exudation of transparent gummy masses in Eleagnus canadensis, occurring especially about the edges of wounds. Frank has described it more exactly. I found the formation of gum in palms, cucumbers, cacti, and hyacinth bulbs’. I assume an enzymatic disturbance in the heart rot and the black ring condition of the horse radish”, the glassiness of cacti, orchids, carnations, etc. Conditions of weakness are thus created which render the plant sus- ceptible to parasitic attacks. Wood has referred to this point with especial distinctness: “I called special attention to the fact that plants rich in oxidizing enzymes were more sensitive to unfavorable conditions of tem- perature, moisture and especially to insect enemies than plants poor in these enzmyes.”’* 1 According to Comes, the “Brusca of the Olive” is a decided gummosis. 2s. Zeitsehr £./Pflkr. 1899; p. 132. = MOGs Clit. (Ds 22. SECTION IV: EPEFECTS OF INJURIOUS GASES AND LIQUIDS: CHAPTER XVI. THE GASES IN SMOKE. SULFUROUS ACIDS. The injuries to vegetation due to the gases in smoke have become so numerous and varied, with the constantly increasing spread of textile indus- tries, that the study of them begins to form a separate branch of pathology, in which chemistry and botany are equally concerned. It is thus evident that this branch of science demands special attention. The subject has been most extensively treated in Haselhoff and Lindau’s book! and later in that of Wieler?. Because of the abundance of material on injuries from smoke we can here merely refer to these works and treat more thoroughly only the points less fully taken up in them. For a long time, scientists were in doubt as to which element in the smoke was the injurious one, until the investigations of Morren*, Stock- hardt* and especially v. Schréder® proved it to be the sulfurous acid. The metallic poisons, like arsenic, zinc and lead, to which especial attention was formerly paid in studying the injuries due to the smoke of smelting houses, have been proved experimentally to be less injurious to our cultivated plants, while a very small addition of sulfurous acid to the air is able to bring about the death of the plants under experimentation. How small this addition need be is shown by Morren’s® observations. He could perceive the charac- teristic indications of destruction in the leaves even when the air contained 1 Haselhoff, E., und Lindau, G., Die Beschidigung der Vegetation durch Rauch. Berlin 1903, Borntrager, 412 pages, with 217 illustrations. 2 Wieler, A. Untersuchungen tiber die Einwirkung schwefliger Saure auf die Pflanzen. Berlin 1905, Gbr. Borntrager. 8 Récherches experimentales pour déterminer l’‘influence de*certains gaz indus- triels, spécialement du gaz acide sulfureux, sur la végétation. Extracted from the Report of the International Horticultural Exhition, ete. London 1866. 4 Untersuchungen tiber die schidliche Einwirkung des Hiitten- u. Steinkohlen- rauches auf das Wachstum der Pflanzen. Tharandter forstl. Jahrb., Vol. 21, Part 3. 5 Die Hinwirkung der schwefligen Sure auf den Pflanzen, in Landw. Ver- suchsstationen 1872. 6 Loe. cit., page 224. 719 ; ' only 1-50,000 of its volume in sulfurous acid. Schroder states’ that one one-millionth will prove injurious if allowed to act for some time. Such slight amounts are certainly present in many kinds of smoke, formed by the oxidation of hard coal, which contains sulfur. Moreover, since sulfur in the form of iron sulfid is an abundant element in hard coal, it may be assumed that, as Morren says, we establish a poison centre for plants with every chimney we erect. Yet, at any rate, we should not carry this anxiety too far. The experi- ments, proving the injuriousness of such small amounts of gas, were made in a space enclosed by a bell jar and the gas usually acted for several hours. This corresponds in everyday life orly to the constitution of the air in the immediate proximity of an industrial establishment, such as smelt- ing house, coke oven, etc., in a narrow valley where the smoke lies day and night in great masses above the vegetation. In the majority of cases the motion of the air, and especially wind, together with the character- istic oxidation of sulfurous acid into sulfuric acid when in contact with moisture, serve as a protection against the most extreme action of the poison, and against immediate death. In any case, however, it would be well, in regions where hard coal or peat? is burned, to choose for industries producing a great deal of smoke, such positions as are removed as far as possible from large plantations, especially from tracts of trees. The gaseous products, from burning hard coal free from sulfur are not injurious to vegetation®. If the coal, however, contains some sulfur and gives it off into the air as sulfurous acid, it will be taken up by the leaf-organs of the conifers and deciduous trees. According to v. Schroder the greater part is retained in these organs and only a small amount is carried into the wood of the plant. The experiments made by Freitag* directly in this con- nection indicate that we shall have to consider the leaves as the main organs for taking up the poison. Yet all leaves do not take up equal amounts of the poison offered them; in this, conifers differ markedly from deciduous trees. Under similar external conditions, with equally large leaf surfaces, the former take up less sulfurous acid than do the latter. Yet it can not be said that a plant suffers more when it has taken up a greater amount of gas. The power of resistance depends rather upon the special organization of the plant. In this connection, the supposition is pertinent that the anatomy, especially the number of stomata, may be determinative for the sensitiveness of a plant. This supposition, however, which has been repeat- edly expressed by Morren, has proved to be erroneous, since Schroder has 1 Schréder, J. v., und Reuss, C. Die Beschaédigung der Vegetation durch Rauch usw. Berlin 1883, P. Parey. 2 According to St6éckhardt the smoke from lignite and peat is also injurious, for this fuel contains sulfate of silica. The smoke of lime kilns is less injurious because the lime retains the sulfurous acid form, just as in brick ovens the magnesia content frequently present in the clay acts favorably because of the retention of the sulfurous acid. Chemischer Ackersmann 1872, Part II, p. 111 ff. 3 Proved for plum and pear trees. 4 Mitteilung der landwirtsch. Akad. Poppelsdorf. Vol. II, 1869, p. 34 cit. bei Schréder loc. cit., p. 321. 720 found that the sulfurous acid is taken up not only by the stomata but uniformly by the entire upper surface of the leaf. He found that just as much gas was taken up by the upper side, free from stomata, as by the underside which abounds in these respiratory organs only the action of the gas which had penetrated the underside was much more rapid and energetic. This is explained by the fact that sulfurous acid is greedily absorbed by water and oxidizes easily in contact with it. Now, since the loss of water from the leaf into the air takes place especially through the porous under- side which abounds in stomata, the action of the gas manifests itself so much the more here. If the water in the micellar interstices of the cell-walls 1s combined with the acid in greater amounts than can be supplied to the walls, they become deficient in water and finally dry up, thereby losing their capacity to conduct water. Thus only those cell bodies will remain well supplied with water and will retain their normal color, which lie directly against the rapidly conduct- ing tissue of the vascular bundles while the dry part, lying between the vascular bundles (the leaf veins) takes on a faded, brownish color. This phenomenon of bright green venation in a faded leaf mass has been taken asa characteristic point for recognizing leaf poisoning from sulfurous acid. Hartig! maintained that the red coloration of the guard cells of the stomata in conifers is a positive characteristic of injury due to acid. This statement, however, was immediately refuted by other observers. Wieler* and Sorauer® have proved that slow death, under the influence of light and with the action of very different factors causes a red coloration. Directly in connection with this characteristic, apparent to the naked eye, is the decreased water evaporation from poisoned leaves, as found by v. Schroder in weighing experiments. The amount of the transpiration may be used, however, as the expression of the amount of production and thus it may be concluded here that the leaf-assimilation is less. The general effect of the poisoning on the plant body will, therefore, resemble permature defoliation and, in fact, the action sets in the more quickly the greater the amount of sulfurous acid present, the drier the air, the higher the temperature and the stronger the illumination, which are the factors inciting the leaf to more intensive activity. Because of this fact, which has been determined experi- mentally, the supposition that the smoke from smelting works and from hard coal will act less vigorously at night than during the day is pertinent, and we will find later that it is confirmed. Caution is necessary, however, when forming one’s judgment from the characteristic of green venation and dried middle fields. Almost all injurious atmospheric effects express themselves in such a way that the parts of a leaf lying furthest from the water-conducting ribs, namely, the fields between 1 Hartig, Rob. Uber die Einwirkung des Hiitten- und Steinkohlenrauches auf die Gesundheit der Nadelholzbaume. Miinchen 1896, Rieger’sche Buchhandl. 2 Wieler, Uber unsichtbare Rauchschaden bei Nadelbaiumen. Zeitschrift ftir Forst. u Jagdwesen 1897, Sept. 8 Sorauer, P. Uher die Rotfarbung von Spalt6ffnungen bei Picea. Notizbl. d. Bot. Gart. Berlin 1896, No. 16. 721 these ribs (intercostal fields), suffer earliest and most extensively from frost, sunburn, etc. With the action of the acids in smoke, however, the boundaries between the dead and healthy tissues are as sharp as usual, while with the action of atmospheric factors they are less distinct because of the many transitional stages. The appearance of the injury in decidedly smoky districts also differs because, besides sulfurous acid others, such as sulfuric acid, hydrochloric acid, hydrofluoric acid, etc., become effective. The action of these acids strongly soluble in water (hygrophilous) is restricted, however, to the immediate surroundings of the centre of production, where they act at any rate much more intensively and kill the tissue rapidly, while sulfurous acid, distributed in a gaseous form over wide districts, is usually breathed in by the plant slowly but permanently. The former effect, appearing rapidly and eating into the tissue, is distinguished as “acute” from the phenomenon of a slow poisoning which is termed “chronic injury from smoke.” Of course, the latter must have made itself felt inside the plant before the external char- acteristics appeared. The chlorophyll apparatus is changed (as has been proved by Wislicenus' with the spectroscope and by Sorauer? with the microscope) even if the plants still appear perfectly normal. In this case an- “muisible injury from smoke” is spoken of. Naturally such disturbances can be averted very easily and the plant, as has been found, is in a position to cure itself after the cessation of a weaker action of smoke. Such cases will also occur in forestry if changes in local conditions take place which divert a stream of smoke or dilute it to the point of uninjurious- ness. Wislicenus*, to whom we owe recent especially thorough, conscien- tious investigations, states that the point of uninjuriousness is 0.0005 per cent. of the volume. : He emphasizes the fact that, aside from the extreme individual differ- ence in sensitiveness, the stage of development of the plant is of decisive significance. The time when the new leaves and needles unfold is the most critical; the plants suffer most then, because the cuticular covering of the epidermis is still insufficiently developed. The above-mentioned influence of light, which promotes injury and was observed by v. Schroder and Hartig, has been tested experimentally by Wislicenus*, who found that visible injuries did not appear in young spruces in the dark and in winter, although an increase of the sulfur content could be proved. Ramann and Sorauer” have also observed that the amount of demonstrable sulfur in an organ is not determinative for the degree of injury and Count zu Leiningen® calls 1 Wislicenus, Resistenz der Fichte gegen saure Rauchgase bei ruhender und tatiger Assimilation. Tharandter Forstl. Jahrbiicher 1898, Sept. 2 Sorauer, P., u Ramann. E. Sogenannte unsichthare Rauchhbeschadigungen Bot. Centralbl. 1899, Vol. LXXX. See also Brizi in Zeitsch. f. Pflanzenkrankh. 1904, p. 160. 38 Wislicenus, H. Massnahmen gegen die Ausbreitung von Hiittenrauchschaden im Walde. Referat 5 der Sekton VIII d. Internat. landw. Kongresses in Wein 1907. 4 Tharandter Forstl. Jahrbticher 1898, p. 152. 5 Hoe. cits 6 Graf zu Leiningen, W., Licht und Schattenblatter der Buche. Naturwiss. Z. f. Landw. u Forstw. III. Jahrg. Part 5. 722 attention to a factor which is of decisive importance in making tests as to the estimate of injuries due to acid viz., to the very different amounts of sulfur and chlorin in shade leaves as contrasted with sun leaves. He found in the beéch in one square meter of leaf substances :— in sun leaves in shade leaves SS A RNA IAS AEM Ns SPA) suc 0:27 30 8: 0.3004 g. OF ERE nite aM arma ee 0.0190 g. 0.0347 g Therefore, the less abundant the production of organic substances is the relatively higher becomes the content of sulfuric acid and chlorin. The statements of Wislicenus express the same: “A poorer soil quality, that is, soil constitution of less value physically and chemically, soils specifically unsuitable for the plant genus or primarily insufficient, excessive, or abnor- mally varying water content of the soil create a Pion eoeaae to disease from smoke; among them the chief factor is the lack of water.” The fact that the conditions in a forest become different because : the falling of the needles and the dying of the branches, indeed, that the appear- ance of deciduous trees is changed, that the trunks become almost entirely free from lichens', and that the bark of the trunks of beeches takes on a peculiar grey tone, may be mentioned only in passing. The statements of v. Schroder and Reuss point directly to the change in soil constitution. They still say that an accumulation of undecayed needles is formed under spruces chronically injured by smoke and a complete absence of all living vegetation is noticeable as far as the dropping from the tree extends. This indicates a “poisoning of the soil.” This is proved by Reuss’ experiments, in which he carried soil from a smoke filled region into a zone free from smoke and set out plants in it. After three years, the loss in 1 to 2-year-old seedlings of the ash amounted to 100 per cent., of the maple 92 per cent., of the beech 72 per cent., of the spruce and pine 8 per cent., and of the oak, none. Wieler? has now taken in hand especially the question of soil poisoning and has proved that under certain circumstances in smoky regions with a continued out-pouring of smoke, sulfurous acid could be proved to a depth of 30 cm. and had, therefore, not been changed into sulfuric acid. The latter will also remain uninjurious only so long as it can combine with bases. If these bases are used up in neutralization and are washed away by rain the humic acid present finds no possibility of combination. In fact, all the soil tests made by Wieler, from regions injured by smoke, showed great amounts of humic acid. Calcium, which could have combined with the humic acid produced is, therefore, not present in these soils. The other bases, however, with which the humic acid forms soluble compounds (mag- nesium and iron) must have disappeared from the soil. Thereby, naturally, the absorptive power of the soil becomes poorer for other mineral nutritive substances. This refers also to the alkali forming soluble compounds of 1 Lindau, loc. cit., p. 120. 2 Wieler, Neuere Untersuchungen, ete., p. 314. 723 humic acid which likewise pass into the subsoil. The lack of calcium makes more difficult the decomposition of the humus substances and the nitrogen enclosed in them remains inaccessible to the plants. At times the bacterial flora is scanty in acid soils. The free sulfurous and sulfuric acids may act injuriously also on animal organisms such as earth worms. Soils in smoky localities will become impoverished or poisoned by all these factors. Wieler ascribes the death of plants and especially chronic injuries to the scantier absorption capacity of soil, which has been poisoned and weak- ened by sulfuric acid or also by hydrochloric acid, but certainly goes too far into this, since all experiments show that the direct contact with the smoke forms the chief cause of death of the aérial organs: also comparative chemical analyses of the foliage and of the soil from which it 1s produced, do not always indicate an impoverishment of the supply of bases, but at times, in fact, a strong increase of calcium and magnesium’ Yet, neverthe- less, this aspect of the effect of acid smoke remains of the greatest impor- tance and the attention of practical workers should be directed to period- ically repeated application of calcium to the soil. We must refer to special works for the influence of currents of air and their constitution, especially their water content, as well as for proving acids in the air and the regulations for overcoming injuries due to smoke. We would like to mention only that Ost* has given a simple method for deter- mining the amount of sulfuric acid in the air. He saturated small pieces of cloth with corrosive barite and dried them. He then hung them in ‘exposed positions in the places where the experiments were being made and after a certain time investigated their sulfuric acid content. By this method even pure mountain air showed a certain amount of sulfuric acid as its normal mixture, which must increase significantly in the neighborhood of villages. We have found recently in a lecture by the chief forestry com- missioner, Reuss*, a summary of the requirements of foresters for the pro- tection of the forest against smoke. He indicates the necessity of forming indemnification societies in regions where many factories are placed close together. The fact should not be left unconsidered that when damages are demanded the objection is raised not infrequently by the injuring smelters and factories that eating by insects is the chief cause. In this connection, Gerlach‘ calls attention to the fact that spruce plantations, diseased by smoke, are preferred by the resin weevil. Not only Pissodes Herciniae and P. scabricollis, but also other insects, like Grapholithia pactolana and G. Chermes increase to a devastating degree in forests injured by smoke. 1 Die landwirtschaftliche Versuchsstation in Miinster i. W. Denkschrift von J. Konig. Miinster 1896, p. 191 ff. 2 Ost, H. Die Verbreitung der Schwefelséiure in der Atmosphare. Die chem. Industrie 1900; cit. Zeitschr. f. Pflanzenkrankh. 1901, p. 248. 3 Reuss, Karl. Massnahmen gegen die Ausbreitung von Hiittenrauchschaden im Walde. Internat. Landw. Kongress zu Wein 1907, Section 8, Ref. 5. 4 Gerlach, Beobachtungen und Erfahrungen tiber charakteristische Beweis- mittel uzw. Merkmale von Rauchschiden. Osterr. Forst- u. Jagdzeitung; cit. Bot., Centralbl. 1907, No. 40, p. 360. 724 HyprocHLoric ACID AND CHLORIN. Besides sulfur, hard coal also contains chlorin in the form of sodium chlorid!. The chlorin content varies between 0.1 to 2.0 per cent. Leadbetter found in hard coal 0.009 to 0.028 per cent. of chlorin*. This, however, could not be proved in the ash and must, therefore, have been forced out with the volatile substances. Meinecke has also directly proved the presence of chlorin in the gases of blast furnaces* and Smith* calls attention to the chlorin content of rain water in regions where hard coal is burned in consid- erable amounts. According to these statements, therefore, we must not consider any single injurious factor in the smoke of hard coal but different combinations of several factors. The difference will depend, on the one hand, on the composition of the coal and, on the other hand, on its use industrially. Because of the rapid formation of hydrochloric acid from chlorin in the presence of moisture and light both these factors must be treated together. In connection with sulfuric acid, mention has already been made of the impoverishment taking place possibly from the continued action of hydro- chloric acid in the soil. The action of direct solutions of chlorin alkalies will be mentioned in connection with cooking salt. The action on the plant varies according to its species, the season of the year, or the place and individual development. In general, this results in a bleaching and drying of the leaf edges, or also of the intercostal fields in which chlorin vapor acts more quickly than does hydrochloric gas. In contrast to sulfurous acid, however, dry leaf edges preponderate here. It was observed in the experi- ments made by Ramann and Sorauer (see Sulfurous Acid) that spruces sprinkled with water absorbed, on an average, less chlorin than plants not moistened. The studies on the changes in anatomy have up to the present led to contradictory results. Thus Lindau’ observed in Abies an alteration only at and near the stomata, while Kinderman® confirms the investigations of Leitgeb and Molisch, that the guard cells possess the greatest power of resistance to injurious factors (among others, acids), which probably arises from a special constitution of the cytoplasm. Because of the uncertainty of results up to the present time, I will repeat here briefly the results of my own studies on grain and spruce’. At first the heavy general falling off in reproduction which the plants undergo, because of the hydrochloric vapors, and which manifests itself in the quan- titative proportions and the formation of the grain, has been found to be very H Hasenclever, Uber die Beschidigung der Vegetation durch saure Gase. 1879, p. 9. Berlin, Springer. Chemical News 1860, No. 46. Dingler’s Journal 1875, p. 217. Bericht iiber die Entwicklung der chem. Industrie von A. W. Hofman, 1875. Loe. cit., p. 244. , Kindermann, V. Uber die auffallende Widerstandskraft der Schliesszellen 1 schidliche Hinfliisse; cit. Just. Bot. Jahresber. 1902, II, p. 653. Sorauer, P. Beitrag zur anatomischen Analyse rauchbeschadigter Pflanzen. Landwirtsch. Jahrbticher 1904, p. 587. Pe & lo gzeze 0 Tae On 725 pronounced ; this confirms the investigations of Wieler and Hartlebt. Such an effect can occur without an indication of a disturbance in growth by any striking external characteristics. As a rule, however, this disturbance in growth is accompanied by a discoloration of the chloroplasts and their subse- quent balling. There then follows a contraction of the primordial sack and a shrivelling of the chlorophyll grains. The leaf thus injured may still at times live out its life normally, depending upon the intensity and length of action of the chlorin. Usually, however, it dies prematurely, in part or entirely. . In the latter case, principally the leaf parts die, for which, because of their position and the lesser development of mesophyll and vascular bundles, the supply of water is acquired less easily and is smaller; these are the tips and edges of the leaf. Therefore, we find dry, discolored leaf tips in grain and narrow dry outlines on both sides of the lower part of the leaf surface which still remains green. As a result of rapid death, a compara- tively important condition is found in the cell content of the dead parts. The drying with the retention of air in the tissue is connected with a shriv- elling of the cells; yet in such a way that the walls of each cell do not touch one another. The natural process of drying, on the other hand, which occurs only after complete impoverishment of the cell content, is character- ized by the entire collapse of the mesophyll cells, in which the upper wall falls against the lower wall and the whole flesh of the leaf, formerly green, represents a pale straw colored strip of dense tissue with curving walls lying upon one another in layers. The collapse of the cells in different varieties of grain, with the exception of barley, extends almost entirely in the meso- phyll during the natural process of drying, while the epidermal cells retain approximately their normal height. In barley (characterized by practical workers as “soft” ), the epidermal cells also collapse in a natural death. But in this, some of the widest cells of the upper surface form an outward fold. In a cross-section through the dead leaf this appears as a conical protuber- ance resembling a hair and gives the whole cross-section the appearance of a thin, knotty spiny cord. Because of the importance of distinguishing a leaf which has died a natural death from one destroyed prematurely by acid gases, we will illus- trate a leaf injured by acids and one which has died normally. Fig 162 1 is the cross-section through the edge of an oat leaf dried by hydrochloric acid, or chlorin vapor. It is seen that the tissue has shrivelled greatly, especially between the ribs (the intercostal fields) without the mesophyll having had time to become empty. The cell contents appear a dirty green to a brownish green color and variously contracted. The walls of the bast layers at the angles of the leaf (6) and below the vascular bundles (b) like the epidermis are colored a reddish yellow to a brownish yellow and the epidermal cells in places (s) are so dried that the upper wall touches the lower wall. Fig. 162, 2 is a magnified cell group from 162, 1, showing the still abundant cell content. 1 Wieler, A., and Hartleb, R. Wher Hinwirkung der Salzsiure auf die Assimi- lation der Pflanzen. Ber. d. Deutsch. Bot. Ges. 1900, p. 348. ried by the fumes of chlorin or hydro- chloric acid and one which has died a natural death. Fig. 162. Difference between an oat leaf d 727 Fig. 162, 3 illustrates the cross-section through a normally dried oat ieaf from a locality free from smoke. In the cross-section the leaf appears as thin as a cord because the mesophyll (V) is approximately empty and the cell walls have collapsed. The leaf does not shrivel in the same way around the larger vascular bundles because the strong layers of bast serve as stiffen- ing; they look like knots in the cord-like form. In spite of the great drying Fig. 1638. Leaves of a red beech, affected by sulfurous acid. (After v. Schrider and Reuss.) of the leaf, the epidermis retains its natural height and at most turns a pale quince yellow like the bast cords, and is thus distinguished from that injured by acids. Fig. 162, 4 is a magnified group from Fig. 162, 3. FE indicates the epidermis ; below this, the collapsed mesophyll cells in which the scanty cytoplasmatous remnants of the cell content have been made recognizable by soaking the section in water. Also in the oat leaf which has matured slowly in continued wet weather the part injured by acid differs in color 728 from the normal since it has assumed a lemon yellow color in the walls of the bast layers and epidermal cells. The intensity of the discoloration is connected with the quality of tannin. In observing differences in color one must work quickly, since the coloring matter is soluble in water. All that has been said here of grain varieties may not be applied;without limitation to other plants. As a general occurrence may be considered only the fact that in all kinds of sudden death, the cell contents are abundantly Fig. 164. Birch leaves injured by sulfurous acid. (After v. Schréder and Reuss.) Fig.165. Rose leaf and Fig. 166. Beech leaves injured by hydrochloric acid or chlorin fumes. (After v. Schré6der and Reuss.) retained, while they are for the most part used up in respiration when the leaf has lived out its life naturally. In order to emphasize the habitual differences in the manner of attack of the vapors of sulfurous and hydrochloric acids we will give here illustra- tions of injured leaves copied from the repeatedly cited works of vy. Schroder and Reuss. In Fig. 163 we see a leaf of a red beech taken from the vicinity of a silver smelter, which had been injured by SO,. Fig. 164 shows a birch leaf 729 from the neighborhood of a copper mill likewise injured by SO,. The com- mon characteristic consists of more or less sharply defined brown specks in the intercostal fields. The spots are usually surrounded by a brown zone which may vary in tone. In many trees (for example, the red beech) a transparent yellowish green band of diseased but not dead tissue is found around this peripheral zone. Figures 165, 106 and 167 illustrate leaves from a rose plant, a beech and a birch, which have been artificially injured by hydrochloric acid. They have the dry periphery, which may usually be observed after the action of pure chlorin vapor. Nevertheless, it should be emphasized that in testing smoke effect no definite conclusion may be drawn from such structural pictures showing the habit of growth, because, on the one hand, the forms of injury vary according to the individual habitat and de- velopment of the tree and, on the other, different factors may produce similar injuries. HyproFLuoric ACID. More often than was for- merly supposed, hydrofluoric acid produced by the opera- tion of superphosphate, glass and chemical factories has proved injurious to vegeta- Heme ne Pict, sat first. sd puzzling, that smoke from kilns and terra cotta factories is very injurious in many cases and in others non-inju- - rious has been explained by fig. 167. Birch leaves injured by hydrochloric this action of the acid. The acid or chlorin et acaegl v. Schréder and difference in effect depends upon the presence and amount of fluorin compounds to be found in the clay and raw phosphates. According to Ost, action manifests itself in small, brown, corroded spots which in many plants are surrounded by a yellowish zone. Smoke experiments carried on by other investigators produced in oak leaves narrow, yellowish brown, sharply defined peripheral discolorations. The Norway maple showed similar tracery along the edges of the leaves and the leaf surface and later also turned brown. Lindau’ describes the ana- tomical condition in the oak. He found both of the epidermal layers to be intact and the contents of the mesophyll cells slightly browned. The indi- vidual chloroplasts were still recognizable, “but the rest of the cell contents had an oily appearance.” Ly Woes Cit. ps2 50: 730 In regard to the forest trees, which come most under consideration, we find it stated that the spruce, even one day after artificial smoking, shows some shoots with a whitish gray discoloration; in fact, they had wilted. After a second smoking the little trees were set out of doors, where the color tone, which originally had been a whitish, yellowish gray, passed through all the gradations from yellow and yellowish red to the “characteristic red of injury from acids.” Pines, larches, and acacias, like the spruce, were found to be discolored in the vicinity of a phosphate factory where hydrofluoric vapors were devel- oped in the removal of phosphorite containing the calcium-fluorin by the use of sulfuric acid'. Mayrhofer* was able to prove a strikingly high content of fluorin in the needles and leaves at a distance of 500 to 600 m. from the factory. The effect of such an exhalation may be absolutely destructive to grain. Thus Rhode*® observed that in some plots rye devel- oped no kernels at all, or only deformed ones. My own investigations were made only on preserved material of dead spruce needles which I had received from Professor Ramann, but, what is most important, the condition found in them agreed with the effects obtained with sulfurous acid. Only, in the needles affected by the hydrofluoric acid, I found, however, a wrinkling of the tissues as a result of the shrivelling of the cell walls. It must be concluded from this that the drying of the needles. which appears so quickly with the use of sulfurous acid, takes place only after the direct action of the acid has already produced a change in the form of the tissues. The contents, however, had not dried against the walls as in the action of sulfurous acid, and, on this account, could not have contributed to the stiffening of the walls themselves. Nitric AcIp. We find only one note by Konig* on the influences of nitric acid (or nitrogen tetroxid). With 5 grains nitric acid (reckoned on nitrogen tetroxid) to 100,000 1. of air or 0.05 g. of nitrogen tetroxid in one cubic metre of air, he found characteristics occurring in trees which resembled those appearing after the action of sulfurous acid and hydrochloric acid. The air generally contains only 0.00003 g. of nitric acid in one cubic metre. AMMONIA. Ammonia and ammonium carbonate in quantities far beyond that of the usual content of the air, which at most may be assumed to be 0.056 mg. per cubic metre, were found to favor growth. In general manufacturing pro- cesses, however (ammonium sodium processes, etc.), such large amounts 1 Allgem. Forst. u Jagdzeitung 1891, p. 220. 2 Mayrhofer, J. Uber Pflanzenbeschiidigung, veranlasst durch den Betrieb einer Superphosphatfabrik. Freie Vereinigung d. Bayr. Vertreter fiir angewandte Chemie. Vol. X, p. 127. 3 Rhode, A. Schidigung von Roggenfeldern durch die einer Superphos- phatfabrik entstrO6menden Gase. Zeitschr. f. Pflanzenkrankh. 1895, p. 135, 4 Konig, Denkschrift 1896, p. 202. i become free that they produce injuries, although the plants in general are found to be very resistent. The sensitiveness of different species varies greatly, but the kind of injury shows a great uniformity; namely, a black coloration occurring in spots or surfaces. Experiments made by Borner, Haselhoff and Konig! exhibited in the oak the appearance of dark spots or a complete blackening of the leaves. In the cherry at first a brown color was seen and later black. After a short exposure to the action of ammonia the leaves and blades of barley were bleached white on the side turned toward the sun. Rye and wheat showed rusty spots and edges. In addition to the cases already known in literature, I will add here a few of my own observations. I found the leaf tips of barley turning white. The intercostal fields of young chestnut leaves were dark at first, but became black the next day and later dried up. The foliage of some of the red blos- soming varieties of Azalea indica behaved similarly, while in a variety stand- ing nearby but bearing white blossoms only a browning of the leaf tips and edges appeared. Along the edges of the outermost tips of blossoms of the red variety, white, nearly round, or wedge-shaped spots resembling a natural variegation were found, while blossoms of the white variety within the same length of time remain unchanged with the exception of scattered small, brown spots. No after effects could be perceived after the plants had been removed from the ammonia atmosphere; but there was some reaction in the inflorescence of a cineraria. The red, outer blossoms which had turned blue from the ammonia, became red again some time after their removal from the ammoniacal atmosphere. The spruce furnishes an example of the influence of the developmental stage on the amount of injury. The old needles took on a pitch black color and were retained, while the color tone of the young, delicate needles, at first a dirty green, later passed over into a faded, reddish yellow. The individual power of resistance in the different needles is shown especially clearly in an experiment in which some needles could be observed on branches, among the pitch black ones, which showed no discoloration or at most only a darker green. The black color was due mainly to the pitch black color tone which the protoplasma of the epidermis and mesophyll cells had assumed. The cell walls were only slightly brown. In the cells most injured the contents had become a consistent, granular, doughy mass, which at times had drawn back from the walls. The contents of the guard cells of the stomata were also pitchy black, never red, as in injuries due to acids. In the transi- tional places between tissue which had remained healthy and that which had blackened, it was noticed that the protoplasmic mass in which the chloro- plasts were imbedded had already turned black, while these granules ap- 1 YZeitschr. f. Pflanzenkrankh. 18938, p. 100. Lindau (loc. cit., p. 286) describes the action of the strongly concentrated ammonia gas on the plant cell; in the interior of the leaf the cells usually show very strong plasmolysis; the contents become indistinct and at times drops of oil are exuded. In this a brown to black coloring matter is given out which tinges the entire contracted contents. This proves later to be a ferment. 732 peared unchanged in form and position. Only later the green coloring matter in the protoplasm was found to have changed and become a dirty brownish green. Then the ground substances of the chloroplasts united with the other cell contents apparently leaving behind some granular remnants. The ammonia might also exercise some special poisonous effect on the cell contents besides combining with the acids as has been assumed in another place. Kny' has already called attention to the fact that, according to the statements quoted in the literature on this subject, the protoplasm in very different parts of the plant possesses an alkaline reaction without having influenced the chloroplasts. The same author has shown that a very dilute ammonia solution injures the assimilatory activity. In one case, where the wall of a stable was used as the back wall of a greenhouse, the way in which ammoniacal poisoning may often take place was clearly demonstrated. When the heat was turned on in the autumn, ammonium carbonate developed from the wall, which, in a short time, blackened the leaves of Aucuba, Viburnum Tinus, Prunus Laurocerasus, the Dracaenae and other plants in the greenhouse. Only the tissue immedi- ately adjoining the veins of the leaves remained green. TAR AND ASPHALT FUMES. The discoveries concerning the injuries of tar and asphalt fumes have been explained only recently, since the material for observation has become more abundant. Aside from the effect which the asphalting of streets can produce at times in sensitive plants, the factories preparing the carbons for arc lights are to be considered as essential causes of disease. Roses rich in tannic acid, strawberry leaves, Ampelopsis quinquefolia and chestnuts should be named as the most important plants showing injury from asphalt fumes’. Different varieties of roses suffer in very different degrees ; for example, Tea and Bengal Roses are less affected ; Remontants and their hybrids, however, are for the most part very severely attacked. Parts of the outer membrane, or the whole leaf surfaces become a dull black. Usually if the whole surface is not discolored (Fig. 168 1a) the blackened places occur as interrupted or connected bands between the larger lateral ribs, that is, in the intercostal fields. If the sepals have been affected by the fumes, the blossom buds unfold only poorly. Soon after the appearance of the blackening, the contents of the epidermal cells of the upper side will be found deeply browned, granular and lumpy, and usually deposited along one of the horizontal walls. The cuticle is not browned and apparently unchanged. When the leaf is more diseased, the epidermis of the under side becomes affected in the same way and later collapses. On the other hand, the mesophyll is but little irritated. The fumes act only on the exposed surfaces of the organs; all the covered parts (Fig. 168 1b) remain un- 1 30t. Centralbl. 1898, Vol. LXNITI, p. 430. 2 Sorauer, P. Die Beschidigungen der Vegetation durch Asphaltdaimpfe Zeitscehr. f. Pflanzenkrankh. 1897, p. 10. / User ‘ / Uo iantad, : Fig. 168. Virginia creeper, strawberry and rose leaves injured by tar fumes. 734 changed. If the middle part of the leaf is injured, the edges curl up like the sides of a boat. Attention should be called in passing to the fact that in many roses (for example, Rosa turbinata), a similar discoloration appears in the late autumn. In this rose, for example, I found that the older leaves, still hanging on the stems, had become dully spotted with black without any previous red coloration; this arose from the contraction and browning of the contents of the epidermal cells. These cells, however, retained their natural turgidity and height, but began to collapse after having been affected by asphalt fumes. In this the contents of the mesophyll also retain their normal consistency and position for some time, while, in the autumn colora- tion, they contract at once and change into uniform masses, at first green, but later turning brown. Under the microscope parasitic blackening (Asteroma radiosum, etc.) can be distinguished easily from asphalt cor- rosion. Before I began my experiments, Alten and Jannicket had already described the blackening of roses and strawberries caused by the action of asphalt fumes. They considered the iron which was proved present in these fumes to be the actual injurious factor since it combined with the tannic acid of the cells and they supported this theory by experiments in which they produced black spots, corresponding to those in asphalt injuries, by sprinkling the leaves with ferrous chlorid and ferric sulphate. Ferric chlorid did not have this effect. I could not obtain this result and observers who have sprayed with iron solution as a means of overcoming chlorosis and icterus do not report any blackening. In the strawberry leaf illustrated in Fig. 168, 2 (a cultivated form of Fragaria chilensis), only a partial blackening of the upper side is found at g because only this part of the leaf had lain free; otherwise the phenomena were similar to those in roses, the curling of the leaf edges, the partial dry- ing of the leaf serrations, etc. In Fig. 168 3 we see a leaf of Ampelopsis quinquefoliaa few weeks after it had been acted upon by tar fumes from a factory making electric light carbons. The less diseased leaves were found to be still green but not out- spread; the edges were curled up like bowls and the inside of the blade wrinkled by the outpushing of some of the tissue lying between the finer ramifications of the veins. At times small places with a cork colored upper surface were found near the midrib. With more extensive injury, these places were always present and passed over partially into blight spots which became dry and ultimately united. Finally, each leaf may show very regular markings due to the drying of the intercostal fields. (Fig. 168 3s.) These dry places often break away, due to the rubbing of the leaves against one another, thus producing a lattice-like perforation (Fig. 168 3/). 1 Alten, H., und Jainnicke, W. .EHine Schadigung von Rosenblittern durch Asphaltdiimpfe. Ref. Zeitschr. f. Pflanzenkrankh. 1891, p. 156 und 1892, p. 33. 1 Le ie) vare) Young branches become corky on the side affected and show fine cracks. Any existing air roots dry up. When the action of the asphalt fumes ceases, the leaf’s attempt to heal itself at once become apparent. In case the palisade parenchyma has been only a little, if any, affected, it may elongate somewhat and slightly push out the epidermis, which has collapsed to a state of irrecognizability. If, how- ever, the palisade layer has also died the healthy underlying mesophyll develops a perfectly regular layer of flat cork cells. The same process may be noticed on the leaf stems: the brown, dead, ruptured, outer cork and parenchyma layers, together with the hard bast bundles which at times have also succumbed to the necrosis, are separated from the healthy tissue by a broad cork band which in extreme cases extends as far as the cambium. Vitis vinifera suffers sooner and more than does Ampelopsis, so that its leaves, at times, are curled entirely out of shape and perforated. In this it was observed that in places lightly affected the guard cells of the stomata had suffered first. Other plants behaved differently; in regard to these, reference must be made to my original work on the subject. The corrosion of the epidermal cells, however, may be cited as the universal characteristic. As in all injuries due to gaseous bodies, the fact that the injury is chronic, or acute, determines the results; in the former case, with slower action, the organ affected can remain alive for some time by its counter action and may slowly live out its life. In this the characteristics differ from those found when the action is that of more highly concentrated gas waves, which result in a rapid death. Thus, for example, in the slow death of spruce needles, a strong, red discoloration of the cytoplasm of the guard cells and later, in fact, of their walls was perceived in the still green parts, but not if the injury was acute. The walls of the vascular bundles element also discolored ; as always happens from asphalt fumes, the cell walls suffer especially quickly. This is seen very well in the older fir needles which acquire a metallic lustre. BROMINE. In the ordinary industries in which bromine is. produced injuries due to bromine alone may scarcely be spoken of because, as a rule, sulfurous acid works with it. At considerable distances from the factories the bromine may still be perceived by its odor, but no decided injuries from the acid. Therefore, any description of natural occurrences in the neigh- borhood of bromine factories may be omitted here and only the behavior of plants under the artificial action of intense bromine fumes be described. I carried out experiments as follows for 4 days :— Small, well-rooted spruce saplings in pots were exposed several hours each day to gaseous bromine, being left out of doors between times. The branches nearest the bromine sources naturally suffered most and all their needles turned brown. On the less injured branches many needles were found to be partially brown from the tip back, while on the branches furthest away from the course of the bromine only a few brown needles were found 730 among the healthy ones. The red brown, which in the beginning was very bright, soon turned into a gray brown. The needles kept this color until they fell, about two weeks later, buti this took place only on greatly injured branches. It was found in the discolored places of the slightly injured needles, remaining on the branches, that the walls of some groups of meso- phyll cells near the epidermis had turned a faded to reddish yellow, while the contents had lost their color and finally with a complete disorganization of the walls had dried up. In this they not infrequently passed through a stage of foamy consistency. For some time after the action of the gas the guard cells of the stomata seemed to have become discolored up to the healthy tissues only in the zones of transition whereby their walls had turned a brownish yellow. The epidermis was slightly browned; the sub-epidermal prosenchymatous fibres were found to be colorless. The mesophyll near the brown places remained green and had either a flocculent green content or the chloroplasts were united into lumps. Healthy tissue adjoined this immediately. At places more strongly injured the vascular bundles were also affected and discolored just as from sulfurous acid, but the color tone of the injured needles was only rarely a reddish brown. They were generally a yellowish brown and less hard, a fact distinguishing them from needles affected by SO,. The slight amount of difference is of less moment here because, as said above, in general injuries from bromine occur as a rule in connection with those caused. by sulfurous acid. CHAPTER X Vir: SOLID, SUBSTANCES: GIVEN OFF BY CHIMNEYS AND THE DISTILUALTES MAE Y CONTAIN: The best survey of the material from the streams of smoke affecting vegetation is found in a table by Wislicenus* which we may repeat here un- changed because it is so very clear. No general decision can be reached as to the substances given in this table. Under certain circumstances they may become injurious and, indeed, very injurious but, in other cases, they do not cause any loss of crops worth mentioning. This depends not only upon the greater or less exposure of the plants but also on locally different, secondary conditions. Aside from the individual sensitiveness of different species of plants, the constitution of the soil and the weather at times become decisive, especially with fine flying ashes. It should be mentioned in connection with the injuriousness of tar vapor that tar vapors from lime kilns also cause injuries. In burning lime- stone, when the calcination begins, that is, the breaking down of the carbon- dioxid, the smoke becomes laden with great quantities of the distillates given in the table, which produce corrosions similar to those described under asphalt fumes. These vary with the plant. The imjuriousness of soot was previously universally overestimated and is still, to some extent. The more recent investigations of v. Schmitz- Dumont and Wislicenus! confirm Stockhardt’s older discoveries, that soot is usually non-injurious. More delicate plants may show corrosion because of phenol, ete., carried in the soot. The theory of the stoppage of the stomata must be left undiscussed. According to my investigations of plants covered with soot the cases are very rare in which the soot particles have succeeded in getting into the cavities of the stomata, or actually have stopped them up, and even in these rare cases, I have not been able to perceive any change in the surrounding cells. Considerable quantities of extractive substances (sulfates and phenols) must first be leached out from the soot before any injury may be 1 Wislicenus, H. Zur Beurteilung und Abwehr von Rauchschaden, Vortrag in Dresden am 31 Mai 1901. Zeitschr. f. angewandte Chemie 1901, Part 28, Taf. V. i | 738 | | CHEMICAL CONSTITUTION OF (THE FIGURES INDICATE ~— 5 Ordinary Smoke from Hard-coal Furnaces (Double Chemical Air Content) Constituents in Gases Distillates and Solid Matter Contained Occurring Typically in from Smoke Foundries, etc. ) Steam | House Boilers | Heaters ~Wood-burning Ovens (Chareoal-kilns, Old Glass Tar Fumes (Injurious) Ordinary ) Unsuitably |. | Z 5 Aromatic Carburetted Hydro] — Coke Used, = ; aa a9 and Brick! |) es a ae 0 10.13 | 8.0 Phenol (‘‘Creosote’’ ) ae ard-coal) loae5 CO; 8.73 \) tae Anilin ccasion ; eu (CO) (a 3 Pyridin ally In Heating, 2 (ek, — Pyrrol Charcoal Tron Se H.O 4.7 ? Refineries, Soor (Practically Non-injurious) Steel S st ye with | bal Carbon with Compounds: Smelters 5 “ oo (ae 0.04 Tar-like, NH, | (Reducing Shi oie : Potassium, Sodium, Caleium Heat) SS) a Sulfurie Acid = HCl 0.005 2 Chlorin u a. =a Rhodan, ete. er q HF S35 Fryinc Asues (Conditionally ae “a SiF, Injurious) al Hsi B. Oxids \ Various Basesas cm ee | Carbonates | Non-injurious 2 Nitrie and \ Phosphates { Insoluble = Nitros Acids | Silicates } Substances = HS - As.O, Soluble with Difficulty = (C8. (Manufacture of Sulfates | of Fe, | Soluble | ' Metal Refineries “lle a S| ee Chlorids f Zn, Cu | Injurious { a] NH, 3 Alkaliesand Am- f — Sub- A |.c (Amin Bases, | monia Salts ) stances S eS Ammonia Salts) | ee i) S eae . e ‘ 3 a a R ] ed Manufacture of OTHER SpeciFic Soins: ad | gh htherand | 0 cae Zn and ZnO ; Zine Refineries £ Ghani (Manufacture of CaCs, Ca(OH)z, CacCOs Carbid Factories | Fumes, etc. ‘ Cement Dust Portland Cement Works SS — I gg Fishe) VARIOUS KINDS OF SMOKE NTAGE) Dl Ly q VOLUME PERCE 18 SUOTPBIVYXY OLUBOLO A 17 16 15 14 13 12 11 j=) tl © IYOULG PATOULOIO'T SOAISO[UXG pure spunoduoy Wwaso01gN ®ONH Jo oanqovjnur yy ‘OJo ‘SOLLeUTOYy [IO ‘seltojoRy vanpy (u0oNe -INJVQ) IBSNG Jood-aso[N][V0 -OJG[NG ‘Sy1O \\ SULTON (sorpRo]q-MBy ‘dyad -poo\, ‘1odRq) sotloyove[g (ssoo0rd [QBN ) SPOULBUGT JTUTB.LO S| OUT JO pLLoTyD “TOH ‘ayBT[NG ‘Sol10joB 7 SULYOROT SOLLOJOVI OTL punoy Wor, Sosed) 9}Sv AL syto 4, oyeydsoyd -19dNQ WOT SOSBL) OISB AL ieds-ony i] WAOAID SUISf) ‘SoLto}OBVy SSR[t) JUdDSeTRdG, PUR ssBpD MOT[[OF{ ULOLF SOSBL) 94SB AA SSOVO1 OyET[NY oy} suts;) ‘SOLLOJOR SSB[L) UOT SOSBL) OSB AL (AYOUAGS|R ET) SoLtoqOV AT ploy WO SOSBE) BISBAL SUdA() SOIL UTOAY SOSR4) id Borie Ac 0.089 0.004 Ultra- marine Ovens YI 0.07 0.025 Chiefly Waste Gases Containing Fluorin HNO; In Annealing 0.089 In O. 44 26 5 0. 0.45 oO. Used : as, Soda Residue in Refuse Heaps. ) at Bi g ( e Tluminatin as, Prussic Acid, Ferrocyanid, etc.) Ns Ae Iuminating © Photographic Papers, ete. ) 740 manifested. This is shown in Wislicenus’ experiments with the soot from hard coal, lignite and benzine, as well as extracts from soot, by means of which the leaves of the hornbean and linden and, later also spruce needles were slightly etched. Probably, as they dry up, the salts effect an osmotic removal of water and a drying of the cells. The same experiments also dis- pelled the fear that a thick coating of soot absorbs the light, changing it into heat and, therefore, acting disadvantageously. It is theoretically possible that the carbon dioxid carried in the smoke can act injuriously for even experiments with an extreme increase of this gas above the normal 0.04 to 0.06 per cent. have proved the retardation of assimilation but this can scarcely be spoken of in practical industry. The same holds good for carbonic oxid. The metallic elements of the smoke from smelters (see table) also enter into the question of the effect of flying ashes. According to Freytag’s inves- tigations’, pure metallic oxids are usually non-injurious. Naturally, foliage bearing such oxids cannot be used as food for animals, since they may easily cause inflammatory diseases. Also, these metallic elements such as insoluble oxids or carbonates and silicates scarcely injure the aérial parts of the plants more than does the street dust. Soluble compounds, on the other hand, such as arsenous acids, sulfates, and chlorides (copper, zinc, and lead) are principally concerned here and produce brown spots through the corrosion of the tissue, as soon as they are deposited on moist leaves. They are said not to injure dry foliage and a subsequent wetting from rain easily washes away the coating. Mer- cury fumes in the air always act very injuriously. The compounds washed into the soil by rain are absorbed by it and are usually non-injurious. A large accumulation of arsenic (more than 0.1 per cent.) is disadvantageous. Experiments. made by Phillips? prove that healthy plants undergo no dis- turbances in growth from the taking up of lead and zinc, while copper acts as poisonously as arsenic and disturbs the root development. Klein® and numerous, more recent observers furnish proof of the presence of arsenous acids in plants. Such poisoning of the soil may occur, for example, near copper smelters and in the litigation against the Mannsfeld-Hettstadter copper smelters Grouven refers especially to this point*. My own experi- ence in the same region shows that, at present, large surfaces of the fields have become poisoned and, despite very abundant fertilization, yield very meager harvests. The experiments in which soil which had become unfer- tile was carried from the vicinity of copper works to a region free from smoke prove that the gases in the smoke are not alone the injurious factors, 1 Freytag, in Jahrb. fiir das Berg- und Htittenwesen im KOonigreich Sachsen 1873, pp. 24 and 36, cit. in Hasenclever.—Landwirtsch. Jahrb. 1882, p. 315-375. In regard to the action of smoke, the author differs from Schroder inasmuch as he does not consider the sulfurous acid as such to be the injurious agent, but only the sul- furic acid which is being formed from it. 2 Phillips. The absorption of Metallic Oxides by plants; cit. Bot. Centralbl. £8835) Viol: ae INos di. py 364: 3 Chemischer Ackersmann, 1875, Part 4. 4 YFithling’s neue landwirtsch. Z. 1871, Part 7, p. 534. 741 but also the soil which has been rich in copper salts. [ven in the latter place, which is free from smoke, the plants (Phaseolus vulgaris) became diseased while those sown in the same region in soil which had always been there remained healthy and developed vigorously. An analysis of potatoes, of which the plants themselves were covered by the metallic dust from a nickel factory, shows how much of the metal may be taken up by the plants during one period of growth. The healthy foliage contained (in percentages of substances free from water and from sand) : Coppek Oxides hs wae ree 0.198 PAT CRO Cg hss ede oi th, sparse hw skametones 0.169 INT CIEL ORO foc rarckc Adve oo 8 edie: saves Bethe The diseased foliage contained (in percentages of substances free from water and sand) : CapMmerr Owls cen ae Gee osteo ees 0.0713 PENNE MORN GHON APIs ec iere hes teed oh ee cts 0.1712 Nite lcel Osada es eS eats acl fetes 0.0251 Analyses of the tubers from these plants, however, did not give any zine and nickel oxid, and only 0.0043 per cent. of copper oxid as contrasted with healthy tubers which contained 0.0041 per cent*. Besides copper as a poison the arsenic compounds are important because of their injuriousness. According to v. Schroder these impair vegetation even if present in the soil in amounts of less than 0.1 per cent. Nevertheless, the improved technique of manufacture takes care that more and more of the arsenic, as well as the soluble metal salts, is kept back from the smoke in the flying dust flues, so that at present a fresh metallic poisoning of the soil is less to be feared. And yet the throwing off of flying ashes requires increased attention. A number of my own experiments have shown that with many flying ashes which become mixed with the soil a visible increase of growth may be obtained, while those from other industries have caused poisoning. This is less often a direct injury to the aérial parts of the plants, but more fre- quently an indirect one, manifesting itself by its effects on certain heavy kinds of soil, rich in water. In aérial injuries, sodium sulfid and calcium sulfid can produce corrosion in some, more tender plants. The course of the action in the indirect injuries has not yet been sufficiently explained. In my opinion, reduction phenomena in the soil are partially concerned in it by which hydrogen sulfid is developed. In heavy soils deeply covered by flying ashes, especially if they have been heavily fertilized with lime, a phenomenon of disease appears to such an extent in barley (I have called it “spotted necrosis”) that the harvest is greatly reduced. All parts of the plants, even the beards of the glumes, appear closely stippled with brown. The brown points represent centers of 1 K6nig, J. Denkschrift der Landwirtschaftl. Versuchsstation Miinster i. W. 1896, p. 204. 742 dead tissue of which parasites certainly are not the cause. Black fungi may later infest these spots and then this complication is described as the “Hormondendron’” disease. The spotted necrosis is, however, not a disease peculiar to regions of flying ashes but it undoubtedly occurs most inten- sively there. I found it could be lessened by a heavy application of lime. The opinions handed down by Steffeckt give the best references to the injurious action of hydrogen sulfid. In them the repeated decrease in the value of the harvest by a mechanical coating of the soil is also considered. I also know of cases in which a deposition of ashes on vegetable plants, especially varieties of cabbage, was so heavy and could be removed to such a slight extent that the quality of the plants became poor, or they were abso- lutely unsalable. If fodder carrots and sugar beets had been heavily covered and their leaf heads used later as fodder some of the animals died. Incred- ibly large amounts of ashes were found in the stomachs of these animals. HypDROGEN SULFID. In consideration of our theory that hydrogen sulfid may be formed in certain heavy kinds of soil after flying ashes have been deposited on them, I made some experiments with barley. In some pots, pieces of potassium (poly sulfids) from sulphur liver were laid between the young barley plants ; in other they were put in the water in saucers in which the pots of barley stood. A piece of lead paper, laid between the plants, slowly turned brown. After six days the leaves began to turn yellow usually, in fact, beginning at the center, more rarely at the tip. The discolored areas appeared to be more watery and transparent than when the yellow discoloration was pro- duced by other causes?. A wilting of the tissue followed the yellow discol- oration and a drying of the green leaf surface lying above it, together with the assumption of a grayish yellow color. The first symptom of the disease is always the bleaching of the chloro- phyll coloring matter, which at once begins to spread into the cytoplasm. This is not preceded, nor accompanied, as in other cases of poisoning, by a contraction of the primordial pouch (or a shrivelling of the chloroplasts). Instead of this, in places, the passing over of the cell water into the inter- cellular spaces becomes noticeable, thereby explaining the transparent appearance of the yellowish areas. The outlines of the individual chloro- plasts then disappear up to the appearance of a granular mass which is contracted in the centre of the whole cloudy, pale yellowish, green cypto- plasm. The impression given is that here the cell contents as a whole swell up into an uniform, doughy mass, while in the action of the hydrochlorin and hydrochloric acid shrivelling phenomena are perceived and, with sul- furous acid, a process of drying of the contents which remain differentiated. 1 Steffeck, Die durch gewerbliche Einwirkungen hervorgerufenen Flurschaden und Verunreinigungen von Wasserliufen und Teichen. Magdeburger Zeitung 1907. Nos. 329 and 331. 2 Sorauer, P. Beitrag zur anatomischen Analyse rauchbeschadigter Pflanzen. Landwirtsch. Jahrb, 1904, p. 643. 743 In oats the bleaching of the chlorophyll coloring matter was slower and less intensive. As a result of the subsequent diseased condition of the roots, the walls of the vascular bundle elements became a deep brown. Sopa Dust. Ebermayer! has reported on the injuriousness of sodium fumes. In the manufacture of cellulose, sodium lye, under high pressure, is permitted to act on pulverized pine wood. To get back the sodium, the lye used is vaporized and the residue burned to destroy the organic substances. In this way a considerable amount of sodium carbonate is freed in the air. The leaves of fruit trees near such factories appear brown or black and die after a short time. Leaves which had been dipped into a dilute sodium solution (1.01 specific gravity) took on the same color; apple leaves appeared to be some- what less resistant than pears and plums. In regard to soda dust, as yet only those cases have been known in which soda from ammonium soda factories was turned to dust by an improper method of ventilating the factory rooms. The soda dissolved by dew, or rain, easily produced in many trees an appearance of the injury from acid vapor, such as the dying of the edges of the leaves, or scattered cor- roded areas. | In doubtful cases the expert is helped by the condition in wild grasses and especially grain stalks which assume a lemon yellow color. Grain can become sterile according to the time and intensity of the giving off of the soda dust and trees may gradually be killed by the repeated annual injury to their leaves. Besides this, different plant species vary greatly in sensi- tiveness and often are resistant to soda but sensitive to acid smoke, or conversely. My experiments on grain and wild grasses (Agropyrum repens, Agrostis vulgaris, Lolium, etc.), in which I covered them with dust while wet with dew, gave the same yellow discoloration, even in the glumes, just as in natural injuries? which were demonstrable at a distance of 2 kilo- meters from the factory. onig* observed that the edges of barley leaves became white.- Red clover is said at first to show small black spots on the leaves, some of which later become entirely black and drop off. The same is true of potatoes. Konig found perforations near the brown edges of the leaves in oaks as in cherries. The needles of the white fir are said to become yellow at the tip and fall off. As a result of his analyses, Konig considers the action of the soda to lie not only in a humification of the leaf substances, but also in the taking up of soda by the leaves, from which it wanders down to the roots. An increase in acids, especially silicic and sulfuric acids, takes place at the same time with the increase of the amounts 1 Hin Beitrag zur Pathologie der Obstb’iume. Tagebl. d. Naturf.—Vers. zu Hamburg, cit. Biedermann’s Centralbl. 1877, if, p. 318. 2 Zeitsch. f. Pflanzenkrankh. 1892, p. 154, note. 3 Borner, ‘Haselhoff and Kénig. Uber die Schidlichkeit von Sodastaub und Ammoniakgas auf die Vegetation. Mitgeteilt von Konig, Landwirtsch. Jahrb. XNI, cit. Zeitsch. f. Pflanzenkrankh. 18938, p. 98. 744 of sodium!?. Often the phosphoric acid and chlorin also increase. In the injuries due to acid gases this reaction of the plant body is shown also further by the fact that the leaves, not yet injured beyond a certain extent, contain more bases than do healthy ones. CoNTROL PLANTS. Reference must be made to technical handbooks for technical regula- tions regarding the avoidance or decrease of injuries due to smoke and flying ashes. However, I would like to give here one method in clearing up the question whether the injuries already perceived are connected with the poisoning of the soil, or are due to the purely aerial action of gas waves containing acid. This method is that of control plant cultivation and is carried out as follows: Wooden cases, containing at least one cubic meter, are sunk in the fields in question and are filled with soil which, before witnesses, has been taken from a region free from smoke. On the other hand, soil taken from the fields in question is put in similar cases which are sunk in a field in a region free from smoke. Both series of cases are then sown in the same way with beans (Phaseolus vulgaris nanus) and harvested simultaneously after a number of weeks. The harvest is examined micro- scopically and chemically. The poisoning of the soil is proved by the fact that the plants grown in the soil taken from the fields in question but kept in cases in regions free from smoke become diseased with the same characteristics as those near the source of smoke. If, on the other hand, the beans from the cases filled with soil from a region free from smoke which had been sunk in the fields in question, near the injurious industrial establishment, show the charac- teristics of smoke poisoning, this then proves that the dangerous streams of smoke alone are sufficient to injure vegetation. These comparative cultures have the advantage of giving the contesting parties an insight into the kind of injury which is recognizable to the layman and thereby furnish the means of an unification of opinion, thus avoiding lengthy lawsuits. It is well in regard to these to strive for the formation of federal smoke commissions. We mean by this the appointed persons from among botanists, chemists, agriculturalists and foresters, who would meet together as a commission of specialists and would always be the same for the different districts. By retaining the same persons they would have a more exact insight into the special conditions of their districts and a more assured judgment in these difficult questions. ILLUMINATING GAS AND ACETYLENE. The injurious effect which illuminating gas exerts on plants has been ascribed to the hydrogen sulfid abundantly present in it. This is, how- ever, not the only cause, for Kny* has shown that gas, carefully purified 1 K6nig (Denkschrift 1896, p. 207), found only in rye, despite a higher sodium content, a smaller ash, and especially less silicic acid. It seemed to him that the silicic acid was dissolved by the soda in the glume and then washed away. 2 Sitzungsber. d. Ges. naturforsch. Freunde zu Berlin in Bot. Zeit. 1871, p. 869. 745 from hydrogen, is still injurious to roots. I conclude from the violet gray color in many roots of trees injured by illuminating gas that some of the tars, or the ammonia, carried over in the gas are the injurious factors. For the present, this violet discoloration of the roots may be considered the best indication of the injury even if it is not an absolutely certain one. We must agree with Wehmer' that such root discolorations occur also in death due to other causes and that often in trees killed by illuminating gas in the soil this characteristic is found only sparingly. The later case is easily explained since only those roots discolor which come in direct contact with the injuri- ous agent and thus cause the death of the tree. The root dying subsequently remains uncolored. The different trees and shrubs show a great diversity in their power of resistance to the affect of gases. While in Kny’s experiments, for example, the elm died very soon, Cornus sanguinea withstood the poisoning of illum- inating gas without any perceptible injury. An analysis made by Girardin? shows how far the effect of a gas pipe may extend. According to it, the soil at the distance of one meter showed empyreumatic oils and sulfur and ammonium compounds. A further example of the different behavior of plants toward illumin- ating gas is given by Lackner*. His observations, however, relate to the effect which the gas is said to exert when burned in the room. Retention in a room where much gas is burned is very injurious to camilleas and azaleas and ivy is said to die at once. On the other hand, palms. Dracaenae, Aucuba japonica and other plants are found to be not at all sensitive to it. Richter’s experiments* prove that illuminating gas acts arrestingly on the growth in length of bean seedlings and other plants and favors the growth in thickness. It is not true that the amount of carbon dioxid, rapidly increasing by combustion, acts as injuriously on the plant body as on the animal body, as people were inclined to assume’ ; it is rather to be supposed that different products of incomplete combustion of the illuminating sub- stances should be to blame for this. 1 Wehmer, C. Uber einen Fall intensiver Schidigung einer Allee durch aus- strOmendes Leuchtgas. Zeitschr. f. Pflanzenkrankh. 1900, p. 267. 2 Jahresber. iber Agrikulturchemie Jahrg. VII, 1866, p. 199. 3 Monatsschrift d. Ver. z. BefOrd. d. Gartenbaues in d. Kgl. Preuss. Staaten. January, 1873, p: 22. 4 Richter, O. Pflanzenwachstum und Laboratoriumsluft. Ber. d. D. Bot. Ges, UGS ALGAE, BE 5 We repeat that with otherwise favorable conditions for growth, the presence of carbon dioxid up to a high percentage is useful, since it advances the production of plant substance as shown by the increased elimination of oxygen. According to the investigations of Godlewski (“Abhangigkeit der Sauerstoffausscheidung der Blatter von dem Kohlenséuregehalt der Luft” in Sachs’ Arbeiten des bot. Inst. of Wiirzburg, 1873, III, p. 3438-70) the optimum for the carbon dioxid content lies tremendously high (5 to 10%) in comparison with the content of the air. In this way is explained the favorable action of hot beds and of the low sunken glass houses of the gardener warmed with horse manure. Here the high carbon dioxid produc- tion of the organic substances, which are being decomposed, is united with the abundant development of heat, weakened light and moist air; i. e. the factors essential for a luxuriant leaf growth. But blossom development is promoted, how- ever, since with the increased carbon dioxid content of the air, the blossoms are formed earlier and more abundantly. (Demoussy, Uber die Vegetation in kohlen- siurereichen Atmosphiren. Compt. rend. 1904, Vol. 139, p. 883). 746 According to my experience with house plants, the dryness of the air is primarily the chief cause of death, and manifests itself in the drying of the leaf tips and edges. In regard to the effect of illuminating gas on roots, Bohm’s experi- ments', with willow cuttings in bottles of water through which illuminating gas was passed, showed that. the action was slowly fatal. The cuttings which died after 3 months had formed new short roots at the expense of the stored starch. The action was thus less intensive than it was when carbon dioxid was passed through the water. In this case all formation of new structures by the submerged stem was suppressed while the upper part, which formed tyloses in its ducts, developed sickly shoots. Death occurred after 2 months. In other experiments in which hydrogen was passed through the water, development was practically normal. (Compare the section on Excess of Carbon Dioxid.) The plants also died when illuminating gas was introduced into the earth in their pots. Seeds, set in earth through which illuminating gas had passed for almost 2% years, developed more poorly. If a stream of atmos- pheric air was drawn through such soils for a considerable time, the soil did not lose its injurious effect entirely so that, as already stated, this effect may indeed be ascribed chiefly to the tarry products which are deposited in the soil in a fluid or solid form. Spath and Meyer? found that even a comparatively small amount of gas (25 cu. ft. distributed daily on 14.19 sq. m. at a depth of 1.25 m.) killed the roots which came in contact with it. Even a greater quantity of gas was found to be less injurious if it reached the trees during their winter dormant period. Here too different varieties of trees display a different power of resistance. Most expedient at present seems to be Juergens’ method, as recom- mended by Bohm, of laying the gas pipes through the streets, etc., in glazed | terra cotta pipes which have openings leading to the light standards so that constant ventilation can take place within the terra cotta pipes. Brizi® has made experiments in regard to Acetylene poisoning. He found in one Italian city that Quercus Ilex died when growing alongside a pipe carrying this gas. Herbaceous plants died in pots and dried up if acetylene was introduced into the soil. The nuclei disappeared in the pali- sade cells of Coleus, the roots lost their hairs, the lateral roots seemed wilted, crushed and brown, the bark cells lacked all fluids. In Evonymous Japonica the plants in dry soil seemed perfectly normal after 7 days, while, in moist earth they had all dropped their leaves after the 6th day and most of the young roots had died. The laurel and the grapevine behaved similarly. 1 {ber den Einfluss des Leuchtgases auf die Vegetation. Sitzungsber d. kK. Akad. d. Wissench. zu Wein, Vol. LXVIII B. 2 Spith and Meyer, Beobachtungen iiber den Einfluss des Leuchtgases auf die Vegetation von Biumen. Landwirtsch. Versuchsstat. 1873, p. 336. 3 Brizi, U. Sulle alterazioni prodotte alle piante coltivate dalle principali emanazioni gasose degli stabilimente industriali. Staz. sperim. agrar. ital. XXXVI; cit. Zeitsechr. f. Pflanzenkrankh. 1904, p. 160. 747 Brizi considers the action of the gases contained in the acetylene and the admixtures to be a displacement of the normal air, containing oxygen, so that the roots suffocated and he thinks that illuminating gas will act similarly but more powerfully. The moisture in the soil, therefore, favors the injury because it reduces the imperviousness of the soil to the gas. This theory of Brizi’s of the suffocating effect on the roots exercised by illuminating gas, together with the products its contains, finds support in so far that I have perceived clearly the odor of butyric acid when cutting the roots of lindens in Berlin after poisoning from gas and I could determine a violet brown discoloration of the membrane of roots of trees which had died because of stagnant water. , CHAPTER X VIEL WASTE WATER. WATER CONTAINING SODIUM CHLORID. Of all the injuries caused by waste water, the most common are those produced by sodium chlorid. These are found especially in regions where extensive hard coal mining takes place. From the experiments published by Konig? in association with Storp*, Bohmer,* Stood* and Haselhoff*, we will quote a few figures about the composition of mine water which will suffice to show what quantities of sodium chlorid and other salts are con- tained in it at times. It contains per litre Name of Mining Sodium Calcium Magnesium Potassium Magnesium Company chlorid chlorid chlorid sulfate sulfate Wenpineane ata e eee 65.949g I11.056g 3.736 0.659 g — Matthias Stinnes.. 33.244 ¢ eH OPN UAeE e735 — 0.042 g Saline Konigsborn. 45.413 g 4.001 g 0.189 g “= 1.250¢ From these examples it is easy to reckon the effect of irrigating, or flooding land with such solutions. The action will be direct, as well as indirect, according to the changes which the soil undergoes. In the latter connection, the fact that nutrient substances in the soil (Potassium, calcium, magnesium, and, under certain circumstances, also phosphoric acid) are dissolved in increased amounts and washed away should receive first consid- eration. This leaching process begins with the percentage of 0.5 g. sodium chlorid per litre. Nevertheless, all water containing any considerable amount is dangerous for irrigation. Pot experiments with-meadow grass show a considerable reduction in harvested substances corresponding to the loss in nutrition of the soil. A second disadvantage of irrigation with water containing sodium chlorid is the increased density of the soil. Even 0.41 per cent. sodium ar Die landwirtseh Versuchsstat. Miinster i. W. Denkschrift 1896, p. 153. Landwirtsch. Jahrbiicher 1883, XII, p. 795. Ibid, p. 897. Landwirtsch, Versuchsstat. 1899, Pp. 113. Landwirtseh. Jahrbiicher 1893, p. 845. Rm & bo a 749 chlorid in the soil is enough to make it sterile because of the density. Sanna found near salt works a preponderance of fine earth over coarse particles and calls attention to the fact that the work of the soil bacteria is stopped by the decreased supply of air. Such soils must unquestionably be laid open in furrows before winter so that they may again undergo a breaking up by frost. Finally, one more point must be cited to which Preglion® has called attention. He studied the peculiar deforming of the ears which is called “Garbin”, and ascribed to the action of sea winds. According to him, how- ever, physiological drought is to blame for this. The salty soil holds the water so fast that the roots-are not able to take it up in sufficient amounts. In regard to the direct effect, consideration must be given to the fact that a plant can particularly adjust itself to water containing salt, according to its own peculiarity, and change its habit of growth accordingly. Hoster- mann® has proved that meadow grasses take on a xerophyte structure; they become smaller and squattier ; the internodes shorter and the leaves smaller ; the plant growth is meagre and the root system develops weakly. Transpi- ration retrogresses and the energy of assimilation is arrested with 0.05 per cent. In regard to the germinating power of seeds, it has been observed that weak concentrations (0.5 to 0.75 per cent.) act favorably, but above that amount injury sets in. Areschoug* mentions other phenomena of adjustment, since he considers the retention of water in tissues not directly connected with assimilation (storage tracheids, slime cells) to be a protection against the accumulation of chlorids. Also, the hydathodes appear to eliminate water containing sodium chlorid. Diels® found that structural adjustment for arresting transpiration increases with the saltiness of the habitat. It might be concluded from this that vegetation from the coast would also behave differently in basins of water containing different amounts of salts. Rostrup® also actually calls atten- tion to this point. Pines suffer the most and birches the least. It is evident from the notes made by the Economic Society of the Province of Maribo after the floods of 1858, ’63, 65 that the effect of salt water is greater the more loam the soil contains. Of winter plants thus flooded, rye suffered more than wheat. In early spring seeding on land saturated with salt, barley and peas were injured most of all. Mangelwurzels, potatoes, white clover and ray grass did not seem to suffer very much from the effect of salty soil. On the other hand, red clover was very sensitive. In Wohltmann’s experi- 1 Sanna, A., Einfluss des Seesalzes auf die Pflanzen. Staz. sperim, XX XVII; cit. Centralbl. f. Agrikulturchemie 1904, p. 826. 2 Peglion, V, Der Salzgehalt des Bodens und seine Wirkung auf die Vegetation des Getreides. Staz. speriment agrar. ital. 1903; cit. Centralbl. f. Agrikulturchemie 1904, p. 507. Ricdme, Influence du chlorure de Sodium, ete.; cit. Zeitschrift fur Pflanzenkrankh. 1904, p. 222. 3 Hodstermann, Einfluss des Kochsalzes auf die Vegetation von Wiesengrasern. Landwirtseh. Jahrb. Suppl. 1901; cit. Centralbl. f. Agrikulturchemie 1903, p. 211. 4 Areschoug, F. W. Untersuchungen iiber den Blattbau der Mangrovepflanzen. Bibl. bot. 1902: cit. Bot. Jahresber. 1902, II, p. 295. 5 Diels, L. Stoffwechsel und Struktur der Halophyten; cit. Bot. Jahresber. 1898, I, p. 606. 6 Rostrup, Plantepatologi, p. 74, 75. 750 ments! with artificial sodium chlorid fertilization, barley and wheat (among summer grains) showed great sensitiveness, while winter wheat throve fairly well even with heavy additions of salt. Peas failed entirely with a strong fertilization; oats were more resistent. Winter rye was found to be the least sensitive. In potatoes, the starch content was much decreased; the protein content not affected; the amount of ash increased. In sugar and fodder beets the quantity harvested was increased without a decrease of the sugar content. Their descent from coast plants may be noticed in this. The effect of salty soil manifests itself in trees only after they have stored up the salt for some time. Weber® is an advocate of the theory that, in many cases, it is not the excess of salt but the marshiness of the soil which causes death. He found in the yellowed branches of Salix viminalis in the valley of the Lahn near Bersenbruck, where the mine water flows in from Eversburg, that the leaves had a chlorid content of 1.309 per cent., while those of healthy plants contained only 0.877 per cent. We find abundant statements concerning the behavior of decorative plants in Otto’s book*. He gives, aS a universal characteristic, the reddening of the tips of plants before they die. Aside from mine water, a high content of sodium chlorid manifests itself in the sewage fields. In summer the concentration of the liquid sewage becomes relatively large and many plants are found “to scorch’ as the gardener on such fields says. Tobacco has proved to be very sensitive so that up to the present there has been a complete failure of the tobacco crops, as emphasized by Ehrenberg*, who has considered very thoroughly all the injuries due to liquid sewage. Besides the sodium chlorid the amount of magnesium chlorid also comes under consideration. The effects of the leaching action are changed, as the experiments of Fricke, Haselhoff, and Konig’ have proved. While irriga- tion with water containing sodium chlorid results in an increased removal of calcium, magnesium, and potassium, yet from water containing mag- nesium chlorid, the calcium, potassium and sodium are lost and the mag- nesium is retained. In irrigation with water containing calcium chlorid, the calcium will be retained by the soil and plants, while considerable amounts of magnesium, potassium and sodium are lost. In large cities, however, the question of injury from sodium chlorid has still a different side, that is, in its use in thawing street railways. Besides this, coarse salt is strewn on the pavements by many householders. In Berlin, this is forbidden, to be sure, but the police is often deceived by the 1 Wohltmann, F. Die Wirkung der Kochsalzdtingung auf unsere Feldfrichte. Landw. Zeit. f. d. Rheinprovinz 1904, p. 46. 2 Weber, C. Kritische Bemerkungen usw.; cit. Bot. Jahresber. 1898, II, p. 301. 3 Otto, R. Wher durch kochsalzhaltiges Wasser verursachte Pflanzenschadi- gungen. Zeitsch. f. Pflanzenkrankh. 1904, p. 136. 4 Whrenberg, Paul, Einige Beobachtungen. tiber Pflanzenschidigungen durch Spiiljauchenberieselung. Zeitschr. f. Pflanzenkrankh. 1906, p. 193. 5 Fricke, Haselhoff, E., u. Konig, J., Uber die Verinderungen und Wirkungen des Rieselwassers. Landwirtsch. Jahrbiicher 1893, p. 801. 751 mixing of salt with sand!. The salt used to remove the snow melts and passes into the soil where the street is not asphalted. In the spring the trees start to grow but die during the course of the summer. Here, too, the different varieties display different degrees of resistance’. Besides this, the action of a solution of sodium chlorid varies according to whether it is con- stantly sprinkled on the roots or whether the soil dries out between times. The latter case is the more dangerous one. Extensive injuries have also been found near volcanoes due to the effect of the vapors. The sulfurous acid occurring in varying amounts in the vapor mixture, and also the hydrochloric acid and hydrogen sulfid, may well be the chief causes of the poisoning. They might also give rise to the destructive effect of the showers of ashes; yet this has been ascribed also by some observers to the extensively deposited sodium chlorid. According to Pasquale’s reports®, some of the red and violet colors of blossoms change to blue (Papaver, Rosa and Gladiolus), some remain unchanged (Viola tri- color, Convolvulus, Digitalis). The green parts of the plants become brown, during a fall of ashes occurring at the time the trees begin to grow, just as after burning or drying but not scalding. Succulent and leathery leaves did not suffer. Mechanical effects from the showers of ashes, such as a possible stoppage of the stomata, could not be confirmed immediately. They seemed, however, to make themselves felt after some days. Sprenger*, who describes the results of the Vesuvius eruption in April, 1900, advocates the same theory as does Pasquale. WaASTE WATER CONTAINING CALCIUM CHLORID AND MAGNESIUM CHLORID. These are found abundantly in mine water from hard coal mines, in the mother liquor flowing away from salt works and baths, in factories preparing calcium chlorid, and potassium salts, in the waste waters of ammonium sodium factories, etc. The analysis of the neutral fluid, which flows from the kettles to which the ammonium chlorid obtained in the manufacture of ammonium sodium is decomposed, shows, for example, what amounts come under consideration in these cases. Konig’? found in 1 liter, 80.00 g. of sodium chlorid, 56.00 g. calcium chlorid, 1.02 g. sodium sulfate. In other tests, which were strongly alkaline, less of the substances named were found, but, in place of these, sodium sulfate and 3 to 5 g. of free calcium. The changes in composition in the soil have already been considered in the pre- vious section, but it should still be emphasized here that favorable effects have been observed if weak amounts are given temporarily (up to 2.0 g. per liter). The germination of seeds was increased. Raspberries and straw- 1 Weiss, A. Zeitsch. f. Gartenbau und Gartenkunst. 1894, No. 37. 2 Ritzema Bos, Schédlichkeit des Auftauens der Trambahnlinien mit Salz- wasser fiir die in der N&ihe stehenden Baume. Tijdschrift over Plantenziekten 1898, p. 1. 3 Pasquale, Di alecuni effetti della caduta di cenere, etc. Bot. Zeit. 1872, p. 729. 4 Sprenger, C., Vegetation und vulkanische Asche. Osterreich. Gartenzeitung 1906, Vol. VII. ' 56 Denkschrift, p. 161. /5? berries were found to be very large and brightly colored on the soil saturated with calcium chlorid. The fruit, however, tasted of calcium chlorid and did not keep well’. BARIUM CHLORID. This is a comparatively less important element, which is found only at times in the waste waters of hard coal mines. Its poisonous action has been proved by Haselhoff? in water cultures of maise and horsebeans. Growth in height was arrested; the leaves wilted and fell. In nature, however, direct injury will occur only rarely, because the sulfurous salts rapidly transform it into insoluble and non-injurious barium sulfate. WastTE WATER CONTAINING ZINC SULFATE. Konig® has paid especial attention to the investigations of such waters from Zinc Blend Mines. It was proved that the brooks which take up the waste water contained sulfurous zinc oxide in solution. An evident retro- gression in the yield and in places a very poor growth was noticed on meadows thus watered. The grasses grown on such sterile places, as well! as the deformed, bushy beech and maple trees, contained up to 2.78 per cent. of their ash in zinc, while the ash of normal meadow plants did not contain this metal. Vegetation dies in places where zinc ore happens to be deposited accidentally. Only one specific zinc plant (the “white mineral blossom’) was still visible. This “mineral copper blossom” contained not less than 11 to 15 per cent. zinc oxid in its ash. It is thus seen how differently the various plants behave and what high concentrations may often be endured. The injuries appear only after a considerable number of years, after the zinc oxid present in very small amounts in the water of the brook has accu- mulated to considerable quantities. Konig is justified in concluding from this that the requirement made upon mines by the Concession Department that only clear water be allowed to flow away into the streams is not enough protection to the owners of meadows. The books supplement the discoveries mentioned, one of which by A. Baumann‘ treats exclusively of the effects of zinc salts on plants and soil ; while another, by Nobbe, Bassler and Will® takes up injuries due to arsenic and lead as well as zinc. It must be emphasized, from the results of Baumann’s experiments, that the zine sulfate in solution is much more injurious to plants than had been supposed up to that time. Small amounts (possibly .1% zinc, that is, 4.4 mg. zinc vitriol in a litre) have been proved absolutely non-injurious in all the plants under experimentation (13 species from 7 families) with the excep- Noe Denkschrift, p. 161. Landwirtsch Jahrbiicher 1895, p. 962. 3 Konig, Untersuchungen iiber Beschidigungen von Boden u. Pflanzen durch industrielle Abflusswisser und Gase; cit. in Biedermann’s Centralbl. 1879, p. 564. 4 Baumann, A., Das Verhalten von Zinksalzen gegen Pflanzen und im Boden. Preisschrift 1884. Landwirtsch. Versuchsstat. Vol. XXXI, Part 1, p. 1. 5 Nobbe, Bassler und Will, Untersuchungen tiber die Giftwirkung des Arsen, Blei und Zink im pflanzlichen Organismus. Landwirtsch. Versuchsstat. Vol. XXX, Parts 5 and 6. ‘ hao tion of the radish. Conifers are very resistent. They withstood a solution containing I per cent. zinc while the Angiosperms died with even 5 mg. zinc per litre and, indeed, older plants died in general more quickly than did young ones, The effect of the poison manifests itself by a striking change in color of the diseased plants. Scattered small areas of a metallic lustre on a rusty yellow color appear on the leaves and finally spread over the whole surface. The fact that the zinc attacks the chlorophyll apparatus especially, thereby hindering the work of assimilation, is proved by the observation that seed- lings in which the chlorophyll grains are not yet matured as well as plants grown in the dark and fungi behave indifferently to relatively highly con- centrated zinc solutions. Zinc carbonate and zine sulfate placed in the soil exercise an injurious effect. In themselves, to be sure, they are not injurious although they are soluble in pretty considerable amounts in water containing carbon dioxid, whereby the zinc sulfid is first changed to zinc carbonate. But their dan- gerous action lies in the transformation which the zinc undergoes in the form of vitriol with the potassium, calcium, and magnesium salts. In this these nutrient substances become soluble and may be wasted away. In poor sandy soils sterility may, indeed, be produced and the injuriousness of irri- gation with waste water from zinc smelters lies especially in this removal of the nutrient substances. The injurious solubility of zinc in the soil depends essentially on the amount of calcium carbonate contained in it. In the presence of this min- eral to possibly four times the amount of the zinc sulfid no more zine will be dissolved. A soil ruined by zinc sulfate can be improved by the addition Gf substances which render the soluble zinc salts insoluble. Humus has been proved to be splendid and, on this account, fertilization with moor soil can be recommended. In the absence of this, abundant stable manure, clay, or marl may be used. Marl, or calcium, must be given under all conditions. Tschirch mentions, in regard to injuries due to lead salts, that a peculiar kind of dwarfing is produced. The plants which have received 1 kg, mennig (red oxid of lead) to 2 sqm. of surface remain small and do not bloom (lead- nanism)*. Devaux? found that lead solutions in a dilution of I-10,000,000 acted injuriously. This metal was fixed by the cell wall and contents. To purify waters containing zinc sulfate, the use of filtering layers of limestone dust and moor earth could be recommended ; insoluble carbonic and humic zinc oxid is formed in them. WATER CONTAINING IRON SULFATE. The waste water from mines and washeries of sulfur silicate and from hard coal mines, the water which drains from piles of hard coal culm and i Sschirch, Aj. Das Kupfer vom Standpunkt der gerichtlichen Chemie usw. Stuttgart 1893, F. Enke. 2 Devaux, De l’absorption des poisons métalliques trés dilués par les cellules végétaux. Compt. rend. 1901, cit Just’s Jahresber. L902 5 Eps 353; 754 the waste water from wire factories usually contains iron sulfate. Besides this, the use of ferrous sulfate as a disinfectant-in cesspools should also be taken into consideration. Large amounts of iron sulfid are thus produced which, through oxidation in the air, are transformed into iron sulfate and sulfurous iron oxid. The ferrous oxid, like zinc from zinc sulfate, is retained by the soil and changed to ferric oxid, while a corresponding quantity of other bases, such as calcium, magnesium, and potassium, combine with the sulfuric acid and are easily washed away. This impoverishment of the soil is accompanied by an increase of magnetic oxid which initiates a souring and choking of the ground. As soon as the bases for the transformation of the iron sulfate are exhausted, the ferrous sulfate remains untransposed, or appears also as free sulfuric acid. However useful small amounts may be on rich soils (up to 150 kg. per hectare, according to Konig"), since the sulfuric acid, thus set free, must act as a loosening medium, just as injurious will be a continued addition of iron sulfate with constant irrigation of pastures. Experiments show that if acid compounds are given the plants instead of the basic salts which alone favor their growth (iron sulfate is strongly acid) a deterioration of the hay results and a decrease in the yield of milk. The different clovers and sweet grasses (possibly with the exception of Glyceria fluitans) disappear gradually from such pastures and sour grasses, the horsetails (Equisetum) and mosses take possession of the soil. An addition of lime water causes the elimination of ferrous hydroxid with the formation of gypsum and it will thus be possible to purify waste water containing iron sulfate by the use of calcium. WastE WATER CONTAINING CoPpPpER SULFATE AND COPPER NITRATE. Waste water from silver factories and brass foundries is concerned here. An insight into the composition of such water is given by an analysis of solutions flowing from a brass foundry published by Haselhoff*. He found in one liter: Copper sulfate, 51.619 g; Copper nitrate, 5.298 g; Zinc sulfate, 14.045 g; Ferrous sulfate, 2.422 g; Calcium sulfate, 1.943 g; Magnesum sulfate, 0.459 g; and free Sulfuric acid (SO,), 30,376 g. This is, at any rate, a very extreme case, for it is one hundred times greater in the individual elements than is the content of the water which flows from copper works and silver factories. For the nature of the injury, however, the amount of the elements is unimportant, since small quantities produce the same effect when used in continual irrigation. The way in which the sulfate and nitrate of the copper salts act on the soil is the same as with zinc and iron salts. Copper oxid is retained in the soil and remains chiefly in the upper surface of the pasture land. The sulfuric acid, which is set free, combines with the calcium, magnesium, and potassium, and these salts, with irrigation, pass 1 Denkschrift, p. 175. 2 Haselhoff, Landwirtsch. Jahrb. 1892, p. 263 and 18938, p. 848. Denksch., p. 176. 75 into the subsoil. Aside from the impoverishment in basic nutritive sub- stances the copper sulfate (such plants as grasses, for instance, take up rather considerable amounts of copper and zinc salts) acts finally also as a direct poison so far as cultural experiments in nutrient solutions' have demonstrated. Masayasu Kanda? found that, in water cultures of peas, injuries appeared even with 0.000000249 per cent. of copper sulfate. On the other hand, if added to soil in a concentration a million times greater, it acted as a stimulant. The conditions are even more favorable for plants in natural soil. According to Tschirch® almost all plants possess some copper since, indeed, all field soils may contain traces of it. The vegetation, on soils to which copper is added abundantly, takes up usually but very little copper, so that the danger of poisoning is not imminent. This theory finds sub- stantiation also in the fact that in the very frequent use of copper sulfate as a spraying substance against parasitic diseases a constant enrichment of the soil takes place without any injuries being demonstrable with certainty. We personally believe, at any rate, that a time will come in which a constant addition of copper will make itself felt as a retardation to vegetation. The waste water containing nickel and cobalt found near nickel-rolling factories will act in the same way as described above. It may be mentioned here supplementarily that John* in 1819, in his book “The Feeding of Plants,” had studied sand and water cultures to which solutions of different metallic salts had been added. He proved thereby that sunflowers did not take up copper given them in the form of insoluble copper carbonate, while peas and barley stored up great masses from a soil to which a solution of copper nitrate had been added drop by drop. The fact that local conditions sometimes make possible a beneficial use of the waste water but at other times cause injurious factors to be felt, prevents our consideration in more detail of the different industries. In this connection the poisonous peculiarity of the soil, due to its power of absorption, plays a principal part. Hattori® calls especial attention to this in regard to copper salts. The injuries due to municipal irrigation with liquid sewage have been mentioned already in the section “Sewage Disposal Fields” (page 364). 1 Otto, R., Untersuchungen tiber das Verhalten der Pflanzenwurzeln gegen Kupfersalzl6sungen. Zeitschr. f. Pflanzenkrankh. 1893, p. 322. 2 Masayasu Kanda, Journ. College of Science. Tokyo, Vol. XIX, Art. 13. 3 Tschirch, A., Das Kupfer vom Standpunkt der gerichtlichen Chemie, Toxi- kologie und Hygiene. Stuttgart 1893, Fr. Enke, 8°. 138 p. 4 Miiller, Carl, Zur Geschichte der Physiologie und der Kupferfrage. Zeitschrift fur Pflanzenkrankh. 1894, p. 142. 5 Just’s bot. Jahresber. 1902, Absch. Krankh. Ref. 277. CHAPTER XTX. INJURIOUS EFPPECTS OF CULTURAL METHODS: A. COATING SUBSTANCES. 1. Tar. The inside of the framework of conservatories is often coated with tar in order to increase its resistance to great dampness. We are confronted with a long list of complaints that, after setting out the plants in the tarred greenhouses, a blackening and falling of the leaves takes place. I noticed the same phenomena near freshly tarred fences. The conditions found agree in all essentials with those described for asphalt fumes and are explained by the exhalations from the fresh tar coating. The injurious results do not appear if the tarring has taken place a few months before the plants are brought into the greenhouses. I found a method used in the vicinity of Berlin which acted as well. The boards and framework were treated with hard coal tar and after this had dried were coated with cement. An attempt has been made recently to keep the paths in gardens and public parks free from dust by means of a thin layer of tar. The process is much recommended? and the experiments made in France and Italy have shown that even paved streets can be treated advantageously in this way. This process necessitates, however, the edging of the path with a strip of galvanized tin 8 to 10 cm. high, since the injurious elements of the tar would otherwise attack the vegetation. This process, which despite its necessary annual renewal is said to be still cheaper than asphalting and less trouble- some than oiling, or the treatment of the streets with “Westrumit,” must still be tested by further experiments. 2. Refuse from Gas Works. According to a report from Mr. Klitzing, at Ludwigslust, where roads on sandy soil have been hardened by the use of such refuse, a dying back of the street trees was caused. 3. White Lead. Ina case of which I have heard, it was necessary to put potted plants in greenhouses a short time after these had been coated with white lead, and then the unpleasant discovery was made that the plants dropped their leaves. 1 Das Teeren von Fuss- und Fahrwegen in Garten und Parks. Der Handels- girtner, herausgeg. von Thalacker, Leipzig-Gohlis 1906. No. 50. ey 4. Od Fumes. JSorff' used lead oxid as an addition to boiling linseed oil in order to test experimentally the influence of oi fumes. He was led io make these experiments by the injuries which had occurred near a linseed oil and varnish factory. Just as in the decomposition of fats by alkali, a mixture of fatty acid alkalies, soap, is produced, a mixture of ¢or- responding lead salts, lead plaster, is formed similarly by the decomposing of fat with lead oxid. In both cases glycerine occurs as a by-product. When the glycerine, or fat, is heated to a high temperature fumes of akrolein are formed which smell like scorched fat and quickly pass over, through oxidation, into an akroyl acid which is recognized by its suffocating odor. Yellow red to brown spots are produced in the intercostal fields, or along the edges of the leaves according to the nature of the plant. These increase in size with longer action, spread and actually unite. Most of the cells of the leaf mesophyll, especially of the spongy parenchyma, collapse because of the loss of turgidity. The cell contents contract from the walls and the chloroplasts form greenish yellow to brown masses. Finally the struc- tureless cell contents and walls become brown. The elimination of tannin is especially noticeable in the epidermal cells, the contents of which take on a bluish black color with ferric chlorid. The flesh of apples and pears which have been exposed for 4 hours to the oil fumes has an oily rancid taste. Since akrolein, obtained by boiling glycerin, produced the same phe- nomena the injuries from oil fumes may in all essentials be ascribed to this substance. 5. lurpentine Fumes. Molz? made experiments on the effect of turpentine fumes, because a case was brought him for observation in which the leaves of grapevines were said to have been injured by the fresh coating of oil in the grape house. The action of turpentine fumes on the grape leaves became noticeable after a half hour in the slight discoloration of the edges and the increased curling; after an hour, apple leaves showed a weakly reddish browning; after three hours, an intense dark red brown discoloration of the upper side. The grape leaves became an olive brown. At times some green areas were found within the brown surface, so that the leaves looked dappled. Rose leaves turned an olive brown; pear leaves, a shiny, blackish gray. Molz suspects the cause to be a process of oxy- dation produced by “the existence of ‘terpentinozone’ and its action on the ‘bradoxydable’ substances of the cell.” 6. Carbolineum. Like tar, Carbolineum is used, on the one hand, as a coating substance for the framework of greenhouses, hot beds, stakes, etc., in order to increase the resistance of the wood to moisture; on the other hand, as a remedy for injuries to trees and a means of destroying injurious insects. The great difference in opinion as to its effectiveness is due in part 1 Korff, G., Uber Einwirkung von Olda’ampfen auf die Pflanzen. Prakt. BI. f. Pflanzenbau u. Pflanzenschutz 1906, Part 6. 2 Bericht der Kgl. Lehranstalt fiir Wein- Obst- und Gartenbau zu Geisenheim ay, Iga, al{0sy 758 to unsuitable manipulation and also because “carbolineum” is a general term; the different kinds have different compositions and effects according to the factories producing them. In general, all that has been said of tar holds good for the use of car- bolineum as a coating substance. If plants are brought into rooms where the carbolineum coating has not dried sufficiently, they suffer and, at times, show symptoms resembling those produced by asphalt fumes. Thus, for example, Zorn in Hofheim (Taunus) reports’ that the leaves of strawberry plants set out in hot beds of which only the outer side had been painted with carbolineum, became a peculiar brown, very shiny and curled. Under the subject of coating the tips of grapevine stakes, a “Chronique agricole’ calls attention to the fact that even when such stakes have been painted in the winter and the young shoots of the grapevine have already overgrown the painted part in spring, unpleasant phenomena can still occur. Some berries on the bunches which touched the saturated spots were found with blackish brown spots and had a slightly tarry taste. Also the saturated parts of the stake were found less resistant to fungi than those treated with copper vitriol. It was noticed in a peach trellis which was painted in the autumn and exposed to the weather for the whole winter that, nevertheless, in the spring after every rain the youngest tips of the shoots looked as if they had been burned. Such occurrences are by no means uncommon. It is the vaporizing phenol and similar bodies which cause the injury. Since 1899 carbolineum has been used extensively as a remedy applied directly to fruit trees*. As to the results, we find some unusually laudatory opinions, some very harsh ones. The reason for this lies, on the one hand, in the difference in carrying out the experiments; on the other, in the vary- ing composition of the substance which is a mixture procured in the produc- tion of tar from hard coal and charcoal. If the tar which is produced in the manufacture of gas from hard coal together with the illuminating gas, coke and ammonia water, is reheated in a distilling apparatus up to a temperature of 150 degrees C., so-called light oil is obtained; between 150 degrees and 210 degrees C. middle oil; between 210 degrees and 270 degrees C. heavy oil, and between 270 degrees and 450 degrees C. anthracene’. The pitch remains in the oven. Wood tar behaves in much the same way. In preparing carbolineum the oils above named are used since they are mixed im definite percentages and decomposed with kolophonium, asphalt, boiled linseed oil, etc. Aderhold* states that, at the present time, possibly 80 carbolineum factories furnish the trade with 200 to 300 varieties. The distillation experiments made by Scherpe in the Biological Institution of Agriculture and Forestry with 25 varieties proved that often the (espe- cially injurious) light and middle oils were absent and the heavy and 1 Praktischer Ratgeber im Obst- and Gartenbau 1905, No. 51. 2 Chronique agricole du canton de Vaud 1892, No. 10. 3 Mende, O., Zur Obstbaumpflege. Gartenflora, 1906. No. 1. 4 Aderhold, R., Karbolineum als Baumschutzmittel. Deutsche Obstbauzeitung (Ulmer-Stuttgart) 1906, Part 22. 759 anthracene oils alone were present, while in other varieties the opposite was found to be true. Accordingly, the results in treating wounds were very different. While normal overgrowth occurred with some, with others there was a very visible increase in the size of the wounds due to the dying back of their edges. But, aside from this, the carbolineum as a means of closing wounds, even in the viscid varieties abounding in pitch and asphalt, does not stand comparison with plain hard coal tar, for Aderhold has observed that a few weeks after the painting, fungus species had already appeared on the car- bolineum surfaces. Since the painted surface may also crack, under the influence of the atmospharilia, such fungi have a good opportunity of pene- trating into the wood. In regard to the very fluid kinds of carbolineum, that is, those rich in light and middle oils, which are warmly recommended for coating trees attacked by red aphis and scale’, the promptness of their action in killing insects is unmistakable, but its protection is not permanent. The recoloni- zation of the painted wounds by red aphis has been repeatedly confirmed. To this should be added, however, the often observed injury to the buds which cannot be avoided in painting or spraying the trees and which is to be ascribed especially to the vaporization and direct action of the light oils. Therefore, the substances should be diluted. It is advisable to use the commercial carbolineum varieties which are soluble in water and to add them to lime water up to about 20 per cent.*; even an addition of 10 per cent. acts favorably*. An action directly favoring growth is said to have been observed in trunks thus coated*, and also the increase of the chlorophyll content of the painted bark has been microscopically determined in Brunswick with the use of a definite brand®. We believe that this result is due to the fact that in coating smooth barked trunks tears are frequently produced in the bark which must be overgrown subsequently. An increased bark activity in the overgrowth walls has also been proved in common scarification. The use of this substance as a coating for trees is advisable only during the dormant period and in fact with some tested brand. “Schacht’s fruit tree Carbolineum” (containing 20 to 30 per cent.) has been repeatedly recommended®. We would never advise spraying in summer. As a means of closing wounds we would prefer coal tar because not only Aderhold’s discoveries, but also experiments made by Schweinbez’ in Hohenheim, and our own have shown no advantage in the use of carbolineum. Its recom- 1 Baumann, R. Geisenheim. Prakt. Ratgeber 1905, p. 459. 2 Praktischer Ratgeber im Obst- und Gartenbau 1906, No. 49. 3 Praktische Blatter fiir Pflanzenbau und Pflanzenschutz, herausg. v. Hiltner. 1906, November. 4 Gartenflora 1906, No. 3. 5 Graef, Uber Karbolineumversuche im Jahre 1906, Prakt. Blitter f. Pflanzen- bau und Pflanzenschutz, 1907, Part 3. 6 Steffen in Prakt. Ratgeber 1906, p. 23. 7 Vom Karbolineum. Gartenflora 1906, p. 22. 760 mendation as a remedy for chronic gummy exudations is based at least upon self-delusion if not the exigencies of advertising. Schweinbez holds the same opinion of the related substances “Tuv”, “Dendrin’, “Baumschutz”, “Neptun”. 7. Lyzol. Formerly lysol had its enthusiastic adherents and doubters just as carbolineum has them now. The Lysolum purum of Scholke and Mayr in Hamburg, introduced into trade about the end of the 80’s of the last century, is a transparent, brown, syrup-like fluid which remains dissolved and perfectly clear in pure water, and has been extensively used as a means of disinfection. In introducing it, it was said that, according to experi- ments, 3g. of lysol to a litre of liquid was enough “to destroy, in 15 to 20 minutes, bacteria in all their developmental forms, if suspended in liquids.” We are concerned here with a solution of tar oils in neutral soap and, indeed, with the light tar oils (cresol), for they volatilize almost entirely between 187 and 200 degrees’. In contrast to other commercial products, like creoline, cresoline, Little’s Soluble Phenyle, which, as solutions of resin or fatty soap in tar oil only form emulsions with water and usually give off carburetted hydrogen oil (Ethylene), when diluted, lysol has the advantage, at any rate, of complete solubility in water, but shares with the above preparations an injurious effect on the tissues of plants. It was used in horticulture mostly as a spraying substance for leaf lice, thrip, black fly, and other injurious insects. Otto’s* cultural experiments, made soon after the introduction of the substance, showed that 0.5 per cent. lysol solution, the one commonly used for disinfection, proves to be a severe poison for plants if added to the soil, even if it does not come directly in contact with the seeds or seedlings. With direct action, even in a much more diluted form, it attacks uncommonly sharply the roots of water cultures. It was used in a 0.25 to 0.5 per cent. solution as a protection against leaf lice. In this, however, it kills only some of the leaf lice, the majority of which die oniy with a 2 per cent. solution; the plants were then so blackened and injured that they could not be considered capable of further life. 8. Carbolic Acid, Amylocarbol, and Sapocarbol. The amylocarbol is a mixture of soft soap, fusel oil, and pure carbolic acid. Sapocarbol is saponified carbolic acid. All substances containing carbolic acid are dangerous and usually directly fatal for plants. In Fleischer’s experiments* with the above prepa- rations, the sapocarbol in one per cent. solution was effective for leaf lice without any injury to the leaves from the spraying, with a few exceptions. In dilutions which completely kill the leaf lice, Pinosol and Creolin act injuri- ously since both can only be emulsified in water. The Antinonnin, the 4 1 Zeitschr. f. Pflanzenkrankh. 1891, p. 185. 2 Otto, R., Uber den schidlichen Hinfluss von wisserigen, im Boden befind- lichen Lysoll6sungen usw. Vorl. Mitt. Zeitschr. f. Pflanzenkrankh. 1892, p. 7Off. 8 Fleischer, E., Die Wasch.- und Spritzmittel zur Bekimpfung der Blattlause, Blutliuse u. Ahnlicher Schidlings usw. Zeitsch, f. Pflanzenkrankh. 1891, p. 325. 761 potassium salt of Orthodinitro-Cresol is more injurious to plants, according to Frank’s experiments’, than to leaf lice and other animal parasites. 9g. Refuse from Lactic Acid Factories. To those injuries we will add a case which we owe to a report from Mr. Klitzing of Ludwigslust. He noticed that the refuse from a factory which produced lactic acid from maize and potatoes, for the treatment of leather, caused the death of plants. 10. Calcium arsenite. The arsenic solutions which are being accepted more and more as a means for combating insects are used as a rule in the form of Schweinfurter green, or calcium arsenite. Injuries to the leaves have been observed in aqueous solutions as also in lime water or Bordeaux mixtures, or sodium arsenite calcium solutions. In general we would refer to the special books on the subject’. 11. Hydrocyanic acid. Fumigation with hydrocyanic acid has recently been accepted as a modern method of combating animal parasites in plants and has been developed especially in America. It may be said in general, in opposition to individual complaints of injuries to plants, that these should not prevent the use of this substance*. Townsend confirmed, for dry seeds, that the germinating capacity does not suffer if the action of the hydrocyanic gas is not continued longer than is necessary for killing animal life. A longer treatment, however, causes considerable injury. Moist seeds suffer more quickly and lose their power to germinate. 12. Copper solutions. These come under consideration here only in so far as their injuriousness is concerned. Their usefulness as fungicides, which will be considered in the second volume of this book, depends, in our opinion, chiefly upon the fact that the fungi give out ferments which dissolve the copper salts dried on the plant parts and thus poison themselves. Bordeaux mixture which, without doubt, is of great importance as a means for fighting fungi, may primarily favor growth, as its enthusiastic advocates would like to prove, but-it cannot be acknowledged as a promotor of growth. Opinions as to whether the copper can penetrate through a normal cuticle in all plants are not unanimous. According to Bouygues? this is not the case. Rumm? also could not prove the existence of copper in the tissue of sprayed leaves and believes that the favorable action can be traced only to the chemico-tactic stimulus. The electric currents, resulting from it, are said to cause the favorable effect in the leaf tissue. The question whether copper can react on the interior of any part of a plant and how, cannot be decided universally but must be taken into consideration case by case. Old cuticule, provided with a thick wax coating, will possibly not be attacked 1 Krankheiten der Pflanzen 1895, Vol. I, p. 329. 2 MHollrung, M., Jahresbericht auf dem Gebiete der Pflanzenkrankh. Berlin, Paul Parey. Published since 1898. Hollrung, M., Handbuch der chemischen Mittel gegen Pflanzenkrankheiten. Berlin 1898. Paul Parey. 8 Townsend, W. O., Uber die Wirkung gasf6rmiger Blausdiure usw. Bot. Gaz. XXXI; cit. Bot. Jahresber. 1902, I, p. 354. 4 Bouygues, H., La cuticule et les sels de cuivre I; cit. Centralbl. f. Bakt. usw. 1905, N. 24. 5 Rumm, C., Zur Frage nach der Wirkung der Kupferkalksalze usw. Ber. d. Deutsch. Bot. Ges. 1893, p. 445. 762 while a young leaf can suffer. In older leaves, however, injuries may also occur in one case and not in another; the cuticle covering may be broken by atmospheric action (late frost) and the copper solution may remain for some time in these tears. Finally, the specific sensitiveness of the plant variety is decisive, as will be shown in later examples. The first doubt as to the peculiarity of copper mixtures for favoring growth arose from the results of some spraying experiments made in 1891’. An arrestment in the development of potato plants could be proved as com- pared with unsprayed plants which remained healthy. The considerable amounts of starch and chlorophyll contained in leaves treated with copper which are considered as an indication of favoring growth were traced by Schander to the effect of the shade caused by the calcium copper coating’. Ewert confirms the effect of shading but calls attention to the fact that this may not be the only arresting factor*. Through the effect of the copper sub- stances, especially Bordeaux mixture, stoppages occur in the transference of the assimilates. The considerable amounts of starch and protein, here observed, are not the results of increased assimilation which, as has been proved, is repressed together with transpiration and respiration, but is the action of arrested transpiration. This point of view which we represent presupposes, ati any rate, that copper actually enters the plant and this theory is substantiated by the fact that scientists who do not assume a penetration of the copper still find copper reactions in a number of their experiments (Frank and Kriiger). Besides this, Ewert has also proved the presence of copper in plants sprayed with Bordeaux mixture. Later we will quote notes from Schander’s work as to the way in which the copper is taken up. In my opinion, the copper, entering through wounds, or through the epidermis of plants treated with copper mixtures, is combined at once with the proteins of the protoplasm and thereby reduces cell-life. Since spraying does not represent a complete wetting of all the leaf surface, certain areas remain healthy, between injured ones, and these must show an increased growth activity. This makes itself evident at times with an abundant supply of light and moisture, in the formation of mtumescences. I described the first case of this kind in potatoes*. Later v. Schrenk’ observed intu- mescences on cabbage plants as a result of their treatment with copper- ammonium-carbonate, copper chlorid, copper acetate, copper nitrate and copper sulfate. Very recently Muth® has observed a very strong formation of intumescences in grape leaves after a treatment with copper. 1 Sorauer, P., Einige Beobachtungen bei der Anwendung von Kupfermitteln gegen die Kartoffelkrankheit. Zeitschr. f. Pflanzenkrankh. 1893, p. 32. 2 Schander, E., Uber die physiologische Wirkung der Kupfervitriolkalkbrithe. Inaug.- Diss. Berlin 1904 und Landwirtsch. Jahrbticher 1904, Parts 4 and 5. 3 Ewert, Der wechselseitige Einfluss des Lichtes und der Kupferkalkbrihen auf den Stoffwechsel der Pflanze. Landwirtsch. Jahrbiicher 1905, p. 233. 4 Zeitschr. f. Pflanzenkrankh. 1893, p. 122. 5 Schrenk, H. v., Intumescences formed as a result of chemical stimulation. Sixteenth annual report Missouri Botanical Garden. May, 1905. Special reprint. 6 Muth, Franz, tiber d. Beschidigung d. Rebenblattern durch Kupferspritzmittel. Mittel. d. Deutsch. Weinbauvereins I. Jahrg. No. 1, p. 9. 793 Such effects may be produced if the tissue is partially poisoned but does not actually die. They may also occur, however, when death actually takes place in which case the dead tissue areas in many plants fall out of the leaf, causing perforation. Such cases have recently been described by Schander’. In connection with this, it is mentioned that Fuschia and Oenothera secrete acids which dissolve small amounts of copper hydroxid. Alkaline secretions have also been-found (Phaseolus multiflorus), or the copper is dissolved not by secretions of the leaf but simply by the atmosphiarillia, especially with continued wet weather. Ruhland? declares, on the other hand, that the assumption of a dissolv- ing of the copper by leaf secretions has no justification, and that this can be ascribed only to the atmospharillia. Reports as to the injury to foliage from spraying with copper have appeared as the process has been more generally used. In 1891 it was observed in fighting Peach rot that, after using Bordeaux mixture, not only the leaves and blossoms fell, but the young wood also was in- jured*. The Amygdalaceae and especially peaches have been found to be especially sensitive. Bain‘ showed in his experiments with r apple, grape and peach leaves that this is connected with the specific sensitiveness of the protoplasm. He says that the peach leaf is able to dissolve copper oxid by a substance secreted on its upper surface. Young leaves suffer most. The in- jured part of the leaf is then cut off ae Spee Brews Sie me aes a by a cork layer and thrown off ; (Shot disease, which Aderhold® has also described for the cherry). Severely diseased peach leaves fall but the apple leaf, as well as the grape, possesses the ability to continue assimilation by means of the remaining lamina. According to Hedrick’s* more recent studies, peaches, apricots, and Japanese plums are the most sensitive fruit trees, while the common plum is not affected more severely than the pear, apple or quince. The different varieties behave differently. The most highly cultivated examples, with the 1 Loc. cit. 2 Ruhland, W., Zur Kenntnis der Wirkung des unléslichen basischen Kkupfers auf Pflanzen usw. Arbeiten d. Biol. Abt. f. Forst.- u. Landwirtsch. beim Kaiser. Gesundheitsamt Vol. IV, 1904, Part 2. 3 Report of the Secretary of Agric. for 1891, Washington 1892, p. 364. 4 Bain, 8. M., The action of copper on leaves, ete. Agric. Exp. Stat. of the University of Tennessee, 1902, Vol. XV. 5 detail into the beginnings of the process of healing. This represents a cross- section through a single wound edge of a place of scarification (Fig. 173 b) t k XY ory) AT} (aa rs ee 2) es Boo: oY ae re os 0 Te “ ~C Age Bye Momcpyolegicys -m . HAC SO Ee ; i Bea ties — nh (Oda pexeiaie nen weleM poner aS RAC Oksttols HOMO pee cen meee sear Baila a1 nora et Dee sab eK & Oleld w Fig. 173. Scarification wound. Fig. 174. Healed scarification wound. in the sweet cherry at a time when this edge had not yet united with the opposite one, growing from the other side of the wound. The wound sur- face (Fig. 175 w) has not yet been covered. h indicates here also the old wood which at w has been exposed by the incision. At the time the incision was made, the knife passed from s to w. The old bark (ar) was drawn back towards the sides from this plane of incision. This part corresponds to that similarly indicated in Fig. 174. The upper part of this old piece of the bark, as well as the edge, which has dried out because of the incision (Fig. 174 t), is indicated in Fig. 175 by the contours marked ¢ and only one hard bast bundle (hb) has been sketched in the bark parenchyma (ar). At the time the incision was made, the cambial zones (c) and the young inner bark (ir) lay close to the old wood (h). The cells which bounded the plane of the wound incision (s to w) reacted differently to the wound stimulus. The parenchyma of the older bark dried backward, for a certain distance, 778 and formed the brown, dry edge of the wound, recognizable to the naked eye, and thus enclosed each slit (Fig. 173 ¢). The parenchyma of the inner bark (ir), still capable of increasing, its growth not yet having ended, takes ’ advantage at the edge of the wound of the opportunity of spreading toward each side where the pressure has decreased, that is, over the plane s to w. These cells, therefore, curve outward. Those from the cambial zone shove ihe first bark cells further out and mature, in the subsequently growing zone, to bark cells (7) containing chlorophyll; and in this way the tender paren- chymatous edge of the wound (7’, ir) is primarily produced. The peripheral cells (r) of the convex edge of the wound turn brown later and dry up. WW D> a Gecall Xo AN) \ g Ah} i LA ( an “ tea 0) 6 CQ Y) NN) H{1{ a TY YS d 0 « HH fara MN) oweael nance mee pae"ay ee ms = «| © () 1g weear h A) iy Ip ()) y 2 m Fig. 175. Overgrowth edge produced in a scarification wound. Cork (k) is produced in the cells lying directly underneath this. This cork zone (k to k), covering the whole wall of the wound, now attaches itself to the outer cork covering of the old bark so that the new structure is sur- rounded by a very inelastic cork layer which consequently presses on the swelling tissue lying beneath it. On this account, the bark pressure is also produced at intervals. The influence of this bark pressure on the immediately succeeding products of the cambial zone (c), which is bent forward like a snail but does not reach to the old wood (h), manifests itself by the formation of thicker walled ele- ments. New wood (nh)is produced which toward the wounded side is PART X. MANUAL OF PLANT DISEASES BY nip mt PROF. DR. PAUL SORAUER Third Edition--Prof. Dr. Sorauer In Collaboration with Prof. Dr. G. Lindau And Dr. L. Reh Private Docent at the University Assistant inthe Museum of Natural History of Berlin in burg TRANSLATED BY FRANCES DORRANCE Volume I NON-PARASITIC DISEASES BY PROF. DR. PAUL SORAUER BERLIN WITH 208 ILLUSTRATIONS IN THE TEXT Copyrighted, 1920-3 : By fae FRANCES DORRANCE Oclagos5088 DEC 22 1920 THE RECORD PRESS Wilkes-Barré, Pa. ARE) parenchymatous, short, with wide lumina (7) and perforated by isolated, short, wide ducts (g). The further the new wood lies from the edge of the wound, the more regular, narrow, dense and longer celled it is, the sharper appear the medullary rays (m) and their continuation (m’) in the bark. The more gradual the formation of the new wood, the more taut is the tension in the outer cork zone (k to k) of the overgrowth edge. This frequently tears apart in places as a result of the inner pressure, so that the bark parenchyma is exposed and pushes out into the torn place. On these out- pushing cells, new cork cells are formed in the shortest possible time, which lie against the surrounding ones and thus close the cork girdle. Fig. 176. ‘Cross-section through a hollow pine trunk’in which only the circum- vallation edges, several years old, carry on the nutrition of the trunk. In case a scarifying incision is so broad that the overgrowth edge of the first year cannot cover it, the new wood of the following year will overgrow the wound surface like a lip. In this lip-like, convex overgrowth, which is recognized best by the course of the new covering cork zone (k to k, Fig. 175) the cambial zone (c) assumes a special curvature, which becomes more marked the deeper the wound surface lies. If it now happens that, in old runks, a broad longitudinal wound is made, instead of a scarifying one, and the wound body is destroyed by atmospheric influences, together with para- sitic action, so that the trunk becomes hollow, ultimately only the overgrowth edges will remain. Fig. 176 represents such a case. It is a cross-section from a hollow pine trunk’. Because of the slow rotting away of the 1 The original may be found in the Botanical Museum in Berlin. 780 younger annual rings, the overgrowth edges have assumed a beautiful, spiral form, rarely to be observed, and the nutrition of the trunk depends on the comparatively slender wood layers of the last few years. The process is shown in less striking form in all hollow trees, for example, often in willows and poplars. In conifers, the rotting away of the trunk, as a result of longitudinal wounds, is a less frequent case, because the wound surface usually coats over with resin, or at least the parts of the wood exposed become resinous. ‘This self protection, after a longitudinal injury, becomes most apparent in the gathering of resin, as Fig. 177 shows. ——> £ | UG \\ aL C= @ See , %, o7, Fig. 177. Section of a trunk of Picea vulgaris with the overgrowth of the resin channels. The entire age of the tree is 70 years. The first resin tapping (a) took place at the age of 50 years, the second (b) at 51, the third (c) at 62, and the fourth (d) at 65 years. (After D6bner-Nobbe.) The wounds resulting from the gathering of resin, in the form of strips some centimeters broad and about 2 m. long, from which the bark has been removed, do not die for some time. In spruce trees, R. Hartig found that the turpentine flowed in drops from the resin canals, lying in the medullary rays, soon after injury. Although a large amount of resin is accessible to the wound, since the resin canals running vertically in the trunk are in open connection with those of the medullary rays, yet the very fluid turpentine, as a rule, ceases to flow after the first year. The turpentine becomes thicker by the volatilization of the turpentine oil and the turning to resin (oxida- 781 tion). After the resin has been scraped off from both sides of the tapped place, the overgrowth roll is cut away in order to open new resin canals, or new strips of bark are removed from other sides of the tree. INSCRIPTIONS. Inscriptions and numerals cut into the trunks of trees, as also the irregularly gnawed and bitten places produced by the gnawing of wild animals in winter, should be mentioned as special cases of a common form of longitudinal wound extending into the old wood and connected with a loss of substance. In inscriptions, the knife has removed considerable amounts of old wood and, therefore, has penetrated deeper into the trunk; on the other hand, however, the wound is not so broad. The healing of deep incisions begins at the longitudinal edges of the wound; the upper and lower edges share only to a very insignificant amount in this. The edges of the wound, produced by the cambial zone and provided with their own bark, extend further every year, forming overlapping layers, and thus gradually grow over the wound surface without becoming re-united with the old wood, of which the outermost cell layers, bounding the wound, turn brown and die. These healing layers form only a mass lying close against this wood, like the metal in a mould. At the moment when the two opposite edges of the wound of each letter coalesce, i. e. their cambial zones unite, these zones again form normally arranged wood elements, which become increasingly thicker because of the annual zone of increased growth, and thereby leave the original incision deeper and deeper in the trunk. In splitting the wood, a lucky blow will separate the intermediate layers, which had not been injured, between the individual letters or numerals, and the original brown mould falls away from the in-grown wood mass. Inyury Due To WiLtp ANIMALS. In injury due to wild animals, the wounds are broader, more irregular but, as a rule, extend only into the sap wood. If the bark and sapwood are torn off from the entire circumference of the trunk, it dries up after a number of years, if the injury did not occur early in spring or in summer. Asa rule, however, the griawing and barking, due to wild animals, takes place only on scattered parts of the trunk and then there follows gradually a formation of overgrowths from the edges of the remaining bark. If such overgrowth edges are injured again in some subsequent year, before the first wound is closed, the wood body apparently takes on a very complicated formation of annual rings. The injuries differ with the kind of animal. According to Ratzeburg?, red deer and elk, but not the roebuck, “peel” the tree, since usually in the spring, in feeding, they loosen strips of bark at the bottom by means of their incisors and then tear them off upward. The healing then takes place either 1 Waldverderbnis, I, p. 50 ff. 782 by overgrowth or, in some cases, by a new formation of bark (cf. Barking of Fruit Trees). The bark may also be worn off by rubbing and blows, but in this the half-loosened remnants remain on the edges of the uninjured bark in the form of tatters, or small rapidly drying and, therefore, curling strips. Usually the traces of hair on the bark remain. Since deer and roebuck rub their horns up and down against the tree, to free them from the velvet, these rubbing wounds are longer than the peeling wounds and more frequently extend around the trunk. Now, the roebuck sheds its velvet in February and March; the deer about the first of May, and others four weeks later. The wounds, due to the latter, therefore, fall in a time when the tree has the greatest amount of plastic material at its disposal. They will, therefore, heal much more quickly than wounds made in the winter and spring. It thus happens that the wound does not once reach the cambium, but only removes the outermost bark layers. If the inner bark remains in place the annual ring develops almost normally beneath it from the cambium, at least, so far as the arrangement of wood and vascular elements is concerned. The wood cells, however, are usually thinner walled, with broader lumina, the ducts much more numerous, the whole annual ring broader. If the weather is wet, or the habitat of the trees shady and damp, a callus tissue frequently develops on the outerside, from the cells of the youngest bark which has been left in place. This callus tissue leads to the formation of new bark; in rarer cases, with luxuriantly growing trees, to the formation of isolated wood bodies. Wounds from blows and splitting of the bark also arise at the time of “rubbing” and in the period of “heat” in the late summer. A different method of healing the wounds now often sets in, since a callus tissue is formed from the youngest sapwood layers on the wood body, which has been freed from the bark; it fills out the hole, as in budded trunks (cf. Budding). We have still to consider gnawed wounds, as produced by mice and rabbits, beavers and hares. ‘The latter, with their teeth, cut young branches or weak plants. Real gnawing, which is so disastrous for our fruit trees, is found usually only after deep snows. The wounds extend to the older wood on which may be recognized the tooth marks. If these reach around the trunk in connected surfaces, the tree is lost. If, on the other hand, isolated particles of bark are left in place, an overgrowth takes place from these. According to v. Berg, it is advisable to fell Aspens and Sallows (Salix caprea), which game peels, at once, in order to protect the other trees from similar injury. Finally, the scattering of food, during the winter, might be cited as the best means of protection. We insert this chapter on the injury due to game only in its relation to the anatomical processes of healing wounds. This subject is treated very thoroughly in a recent work by Eckstein’*. 1 Eckstein, Die Technik des Forstschutzes gegen Tiere. Berlin 1904, Paul Parey, 783 In places where grazing cattle are driven into the forest they frequently cause greater injury than do game. Roots will be exposed to such an extent that whole trees die along the paths. Sheep and goats bark larches, firs and balsams, etc. As v. Mohl indicates, and Ratzeburg confirms, deciduous trees endure injuries to their trunks, extending to the cambium, much better than do conifers. Klein, in his latest forest-botanical note bookt gives numerous and good reproductions of trees that have been gnawed by grazing animals. OVERGROWTH OF Cross WOUNDS IN MANY-YEAR OLD TREES. If branches, or trunks, are cut across the same processes of breaking the bark and the new formation of overgrowth edges must set in as were i, VI, WJ a Wy Ys ff Yj, Uf | Y IY J 4 if YY ff | (fof Wf Mi d WH LYWIW MA Fig. 178. Remains of a sawed off branch which had died back from the cut surface and which had been covered over as with a cap, by the overgrowth edges of following years. described above in scarification. The injury, however, in itself is much more dangerous because in this all the annual rings of the branch are exposed and the effect of the atmosphere and wood destroying fungi is uncommonly facilitated. We see in the adjoining cut (Fig. 178) the product of several years’ overgrowth of the old stump of a branch. The darker, central part is the cut end of the branch, which, under the influence of the atmosphere, has died far back into the trunk. In five years, the wood cap of the overgrowths 1 Klein, Ludwig, Bemerkenswerte Biume im Grossherzogtum Baden. 214 Illus. Heidelberg 1908, Winters Universitatsbuchhandlung. 784 which have extended farther each year, has been formed over the surface of the wound and has finally closed it. The overgrowth in this case has taken place principally from above, since most of the plastic material has come from that direction. In a slender, longitudinal wound the overgrowth takes place principally from the sides. The process of overgrowth, which sets in in the branches of trees, also causes the closing of wounds on cut or chopped surfaces of stumps left when trees are felled. The process extends only comparatively slowly, since the cambial ring producing the overgrowth edges has to cover a very large wound surface. The result is that, long before the overgrowth edge has reached the central part of the cut surface, this has decayed and the center of the branch in consequence has become hollow. The overgrowth masses now sink down into the cavity in very different forms and, at times, in twisted cords covering projecting splinters or stones. Thus they can attain a considerable size’. The question is now pertinent, whence comes the material necessary for such an extensive new formation. The opinion usually expressed is that the reserve substances, formed before the felling of the tree and present in the stump, can be the only source of all the new structures. In other cases, root union, which occurs not infrequently, is used to explain this, for it is assumed that the stump is nourished by the uniting of its root branches with the stronger roots of adjacent trees, which still retain their crowns. Certainly, cases of this kind are not rare in larger tracts of trees? and such a nourishing trunk can actually give considerable assistance to the stump. Nevertheless, there also exist instances in which absolutely isolated | trees have formed such large overgrowth masses on the stump that the supposition of a production of such massive new structures from the reserve substances alone does not seem sufficient explanation. In my opinion, however, there exists universally in such cases an acces- sory apparatus, which is capable of conveying newly assimilated material. If the young overgrowth edges are investigated more or less chlorophyll will be found in their bark, according to the amount of light the trees receive, and it is by no means clear, why this chlorophyll apparatus should not assimilate just as well as the green bark of the trunk. The fact that branches are found growing out of older overgrowth edges shows how abundant is the life prevailing in them*. The formation of branches from the cambial ring of tree stumps is a very common occurrence, which comes to view on all sides with felled poplars and arises from the production of adventitious buds in the paren- chymatous overgrowth tissues. 1 Good illustrations of such cases in GOppert, Nachtrage zur der Schrift tiber Inschriften und Zeichen in lebenden Baumen. Breslau, Morgenstern 1870, 2 Gobppert, Beobachtungen tiber das sogen. Uberwallen der Tannenstécke. Bonn, Henry & Cohen, 1842. 3 vy. Thielau, in Lampersdorff near Frankenstein in his advertisements of the Goéppert Treatise (Uber die Folgen 4&usserer Verletzungen der Baume, etc.) in May, 1874. 785 Even in the poplars a complete circle of strong green branches grows up around the edge of the cut wood body. Such an “eruption of shoots’ degenerates, as a rule, after a few years because it is not able in its place of production between bark and wood to form new roots which can reach the soil. If soil reaches the base of these shoots by being covered or by prema- ture decay of parts of the bark, the shoots can free themselves from the nutritive trunk by growing roots and form long lived, independent individuals. The ability to produce new shoots from the tree stump, very differently developed in different tree genera and very rarely in conifers, does not always depend on the formation of adventitious buds but also on the awak- ening of dormant eyes as in conifers. In this, however, the hard cortex of the stump often hinders further development. If such a subsequent development of shoots is expected and desired, as in forestration or in parks, the trees must be cut down as deep as possible in order to give the new shoots a good chance to root. The custom, not infrequently found, of renewing tree plantations by leaving stumps one meter high, should be given up absolutely. The new shoots developing on such stumps are, on an average, much weaker and are often surpassed by shoots at the surface of the soil. OVERGROWTH PROCESSES IN YEAR OLD BRANCHES, In our cultivated trees, the necessity arises of cutting back the tops in order to prune the foliage shoots and thus favor the fruit buds, or in trans- planting to bring the top into balance with the injured root system. The pruning affects principally the year old growth, and is done either in the fall or early spring. Consequently, a considerable time passes before the processes of closing the wounds begin through new formation of tissue. In this it is found not infrequently that such young growth dies back for a short distance from the cut surface. In Fig. 179 is shown the tip of a year old cherry branch which has dried back some distance from the cut surface. Fig. 180 shows the same branch cut through longitudinally ; s to s’ is the original cut surface; ¢ is the boundary layer, back to which the twig has died; a, a swelling frequently found in such cases. Fig. 181 shows the anatomical structure. In it, s to s’ is the plane of the cut, a h, the last peripheral particle of the old wood of the cut surface; a r, the old bark with its outer normal cork layers (k). Of this bark, the tissue indicated by T has dried back and, in fact, the tissue near the hard bast cords (b) dies the furthest downward; the bast cord is also dead and together with the outer cork layers of the bark, which also are but little shriveled, projects from the discolored parenchyma. The cut surface is, therefore, uneven and rough. The next process which sets in, after injury and after the upper bark tissue has died, consists in the cutting off of the dead from the healthy tissue, by means of the formation of a cork zone (k’, k”). The cork zone is devel- 786 oped more extensively about the base of the bast bundle and represents a radiating overgrowth (k”). The increase in cell numbers begins at once in the layers of the cambial zone (c) lying next to the cut surface, and of the bounding, inner bark which, at the time the pruning was done, lay close to the wood body (ah). Exactly as in the protuberance of the roll in the scar wound shown in Fig. 173, the protruding bark zone (nr) is formed from the products of the one H AC \ t ) Bio. 179) [] ue ease) wag C : Wise SZ, f} Ly ik OJ!O Fig. 181. ey eae A one year old branch of the sweet cherry cut through in cross-section, the cut surface of which has dried back. Fig. 179. From without the cut surface of the branch appears somewhat dried back and has a swelling (a) below the dried tissue. Fig. 180. The same branch cut through in the median line. Fig. 181. Anatomical sketch of the region a to » of Fig. 180. cambial zone and the young bark, and this protuberance is closed in the same way by a cork girdle (k’ k””). The wood products of the cambial zone, the maturing of which changes gradually because of the pressure of the newly produced wound bark, are produced at first as parenchyma wood (Ap) in which cord-like, short, porous duct cells (g) occur. The further the for- mation of the new wood, produced after injury, is traced back from the cut 787 surface, the more the elements of this wood are found to resemble the normally elongated, thick-walled elements (g’, h’). In the drawing, the transition from the short vascular elements to the long ones is interrupted by the continuation of an old medullary ray (m) into the medullary ray (m’) of the new wood. Besides this formation of new wood and independent of it still another cell increase manifests itself in the bark near the hard bast bundle. The parenchyma cells divide and increase, thereby, the thickening of the original bark, which is forced out by these new growths and causes the externally visible swelling (Figs. 179 a, 180 a, 181 a). Under certain circumstances, the new growth within the bark is so intensive that a meristematic zone is produced, which remains active for some time, producing in turn wood and vascular elements, and gives rise to the formation of wood fibres in the bark, said to have been found in the production of gnarl tubers. The drawing of a cut branch, reproduced in Fig. 181, does not agree entirely with the structure found in the overgrowing cross-wound of the stump of a branch. The reason for this is that we usually think of such cuts as having been made late in the spring or summer on older branches. In these cases the drying back of the tissue from the surface of the wound is not extensive until the time when the wound begins to heal, i. e. until the formation of the overgrowth edge (ur, nh). This overgrowth edge soon appears above the cut surface and lies in a curve over the old wood, which had been formed before the time of pruning and is indicated by ah. The arrangement of the elements then corresponds to the formation of the callus roll in the cuttings illustrated in a later figure ; the nature of the cell elements remains that shown in Fig. 181. As the branch becomes older and the wood layers, formed from cambial zones, become increasingly thicker, the overgrowth edge, projecting on all sides above the cut surface of the branch, also becomes thicker and thicker until the opposite sides touch one another and unite in a cap which entirely encloses the cut surface. | Each overgrowth edge begins in the way shown in cross section in Fig. 175. It can, therefore, be said, figuratively, that the new wood layers, formed after injury, spread over the old wood body, laid bare by pruning, and finally shut it in by a cap. GIRDLING CALLUS, By “girdling” is understood the removal of a small circular strip of bark around the whole axis, usually at the time of the greatest cambial activity, since only at this time can the bark body be loosened easily and completely from the wood. In girdling, only the part of the branch lying above the wound receives the plastic material prepared by its leaf apparatus. This cannot, as des- tined, be used to strengthen the wood ring for the whole length of the branch, but is held back above the place of girdling, thus conditioning a 788 more abundant cell increase in the cambial ring at that place. We find that the diameter of the upper part of the branch has strikingly increased in pro- portion to that lying below the girdling cut. The supply of water carried up from the roots to this place is at first, however, considerably decreased. In the first place, the amount of water ascending in the bark is prevented from rising further by the girdling cut, and then the main stream, ascending in the wood, loses no inconsiderable amount of water at first by evaporation at the place laid bare by the girdling. Therefore, in the upper part of the branch the main factor of cell elongation, turgor, is decreased by the lessen- ing supply of water from below. The cell increase is indeed greater but the cell elongation is less than in the normal branch. While the growth in thickness of the part of the axis, which lies above the girdle, is increased, the apical growth of the branch remains moderate; the internodes are not as much lengthened. Shortening of the internodes with abundant supply of plastic material is the first step toward the formation of fruiting wood; thus fertility of the branch is more rapidly brought about by girdling. The part of the branch above the girdling is demonstrably poorer in water; its leaves, likewise poorer in water, take on an autumnal coloration earlier, and the ripening of its fruit is hastened. The assertion that larger fruit can also be obtained by girdling has been confirmed only in certain cases. Grapevines, for example, and the American varieties especially, after girdling seem still to get such a consid- erable amount of water in the upper part of the vine that no retarding of the apical growth is noticeable. In this case, therefore, the development of the fruit depends essentially on the amount of plastic material and this varies in different years, according to the prevailing atmospheric conditions. In the same way, the character of the variety is of influence. For example, Paddock! observed that the variety of grape, “Empire State,” ripened its fruit three weeks earlier than usual because of girdling, the “Delaware,” on the other hand, showed scarcely any reaction and, in fact, its quality was poorer. Girdling is used on grapevines as a means for curing the dropping of the young berries”, but as a constant regular treatment in cultural pruning girdling will never find an opening; it may always be used only as a drastic, exceptional method, in special cases, the injuriousness of which frequently exceeds its usefulness. Even in the grapevine, in which girdling is used most frequently, its use must remain limited. In the “Annalen der Oenologie’* Gothe judges that the hope of a general application of the process in grape culture will not be realized. The advantage of hastened ripening, he thinks, is unmis- takable. In this way, late varieties may still be brought to ripening, but the grapes of girdled vines give a worthless wine. The part of the vine 1 Paddock, W., Experiments in Ringing Grape Vines. New York Agric. Exp. Sta. Bull. No. 151, 1898. 2 Jager, Obstbau 1856, p. 125. 8 Vol. VI, 1877, Part 2, p. 126. 789 above the girdled place dies (at least in European varieties), the part below it is poorly nourished, so that the eyes remain sterile and should not be taken into account in pruning. Besides this, girdled shoots break off very easily. In many trees also there is found frequently a hastening of the develop- ment of the leaf buds below the place girdled, which can increase to the formation of water sprouts. This case is more frequent in apple trees than in pears. Recently, girdling has also been made use of in herbaceous plants with edible fruits. Thus, for example, Daniel' obtained larger fruit with the Solaneae by this treatment. Other observers could not confirm this, but found a retrogression in the develop- ment of the whole plant?. If we now pass over to the study of the anatomical conditions produced by the girdling cut, or “pomological magic ring,’ by means of the adjoining illustrations, we shall, we believe, best further thereby an understanding of the matter by giving first of all a general description of Figs. 182 and 183. Fig. 182 represents a girdled grapevine; u is the lower overgrowth edge, u’ the upper edge; bi, the bared surface of the wood body. Fig. 183 is a longitudinal section through the lower, smaller overgrowth edge (Fig. 182, 7). S,S” is the plane of the lower knife cut in girdling; S,.S’C’ is the protrud- ing tissue of the overgrowth edge. H represents the outermost layer of the exposed wood body; in this, g,g’ indicates the ducts and h,h’ the porous wood cells. R, as in Fig. 182, is the bark cut through in girdling, which appears pushed back from the wood by the out- swelling overgrowth tissue (7,C,C’). This tissue at 2 Fis: 182. A ring- . ; ing wound on a lies close against the wood and is protected externally grapevine with the by a cork layer (k,k’). This protruding overgrowth Be OER aoe edge of parenchymatous tissue is differentiated by the overgrowth edge arched cambial zone c,c,c’, into the parenchymatous (u) and the more weakly formed wound wood (wh) and the wound bark (wr). Both lower one (u). are traversed by radiating medullary rays (m). Figs. 184 and 185 show how such an overgrowth edge appears in cross section. The first was taken from the upper wound wall, close to the place where it leaves the bark; the second figure originates from a broader, most distant region. In considering Fig. 183, we see that a mass of tissue has protruded from the edge of the wound produced by a 3 to 4 fold division of the 1 Daniel, Lucien, Effets de la decortication annulaire chez quelques plantes herbacées. Compt. rend. Paris 1900, p. 1253. 2 Hedrick, Taylor and Wellington, Ringing herbaceous plants. New York State Agric. Exp. Sta., Geneva, Bull. No. 288, 1906. 790 cambium and having at first the character of callus’. This holds good for the products of division of the youngest bark, which united with the cambial callus from the later overgrowth roll. At the time of girdling (in July) the old wood body of the vine (Fig. 183, H) was already strongly developed. We can recognize elongated, thick-walled wood cells in the immediate proximity of the ducts (g), chiefly On Nae, C’ Ae 2 i ce” 1 " ' Hi i i b f ! fi i HS: le SA S a SN ne, a? e YS wane oS eae Sh Ay Ss 2, 8 i ' ' ! ets —+— i Os he Nene CBN A Say "3081 sits Lay GH Bails | | | } if fal Lat inn re) 4 Tiliil wae sereORTOl//AABOeee A ‘ () 0 ss = SS == a s = 5) c ‘Be a SL R Fig. 183. Longitudinal section through an overgrowth roll which has developed from the lower edge of the ringing wound (Fig. 182, u). provided with horizontal cross walls (4), otherwise usually pointed like a wedge and having fine pore canals (h’). The narrower vessels are spiral or ring ducts (g); the wider ones show circular or slit-like pits (g’). The broadest of all have a ladder-like, or reticulated, porous wall. The ladder- 1 All juvenile cicatrization membrane with apical growth of its cell rows, no matter whether produced on a cut surface above or beneath the surface of the soil, may be called “callus.” We will call the callus which has a bark, is lignified, and continues its growth by an inner meristem zone the ‘overgrowth edge.” 791 like arrangements of pits corresponds to the pores of the cells surrounding the ducts in rows, the walls of which cells are pressed against those of the ducts. The lower cut, by which the ringed place was laid bare (Fig. 182 b/) is indicated in Fig. 183 by the plane S,S’. In this longitudinal cut, therefore, the girdled exposed surface extends from S upward along the exposed wood cells. At S’, we see how the knife has smoothly cut the bark (RR) perpen- dicular to the longitudinal diameter of the vine. At the time the cut was made, the bark (RF) lay close against the wood (H). The tissue lying between them and projecting far out (7,C,C’) has been produced after the girdling. And, indeed, the extreme lessening of the bark pressure con- , nected with the removal of the bark in the sectional plane S,S” and the parts adjoining it in the cells of the cambium, as well as in those of the youngest wood, likewise in those of the younger and youngest bark, causes a forma- tion of callus with a surprisingly great cell increase, since the end cells of the tissues named and those directly adjoining them push outward, divide, elongate and cut off their anterior ends by cross walls. In these anterior ends, the elongation and construction is repeated many times. In this way, a callus wall (C,C’) projects in a circle, around the cut edge of which the inner side at 2’ lies close against the wood, without uniting with it. At any rate, this callus wall at first has neither the extent nor the structure given it in the drawing; this represents rather a wound wall devel- oping from the callus which, by the increase of the new cambial zone (c’), has already formed secondary elements of thickening. Originally this callus wall consisted only of thin-walled parenchymatous cells (z,2’) appearing immediately and radially arranged, their diameter in all directions being almost equally long. In such a juvenile callus wall, which is early differentiated, a cork zone is formed (k,k”) first of all on the outer circumference. It gradually increases in thickness and serves as a layer protecting the thin-walled, newly formed tissue mass. The cut surface of the old bark tissue (R) which has been separated widely from the wood by the new wound tissue, is cut off in the same way by the cork layer (k”). The old, hard bast cells (b), which have been cut, have turned brown from the cut surface deep down into the healthy tissue and died. The original bark tissue (r) lying inside and back of these bast cells has participated in the cell increase and callus formation; only the cells lying next to the hard bast of the original bark have formed a cork zone (k”’), cutting off the dead part. Near this cork zone run the hard bast cells (b’), which were already formed at the time of girdling, but under the influence of the cut do not extend normally as at b. The elements of these cells arranged in rows may be traced back- ward into the healthy tissue and gradually pass over into the old bast; this row of cells is continued in the wound wall in the elongated, but very thin- walled groups of cells (b”), which lie at equal distances from the cambial zone. /92 The cambial zone, which runs close to the prosenchymatous wood elements in that part of the normally developed vine which lies below the place of the cut, describes a wide circle c,c,c’ at its entrance into the wound, or overgrowth wall; it divides the apparently uniform ground tissue into one part lying against the old wood body of parenchyma cells with strong, porous walls, the wound wood (wh), and an outer part, the wound bark (wr). In the clearly marked, radiating arrangement of the individual cell rows, this row is recognized as:a secondary growth of the cambial zone, appearing very early in the callus roll. The elements formed from the cambial zone have approximately the same parenchymatous form in the same horizontal surface, only, as already said, the parenchymatous wood (wh) differs from the bark tissue by its porous walls, which are more greatly thickened and more dense and, therefore, lie against one another with sharper angles; a stronger pressure has already made itself felt here. But an evident differentiation is noticeable in the bark tissue itself. Between the somewhat oval cells, forming the ground mass of the bark, we find more elongated, more slender, somewhat prismatic cells arranged in a curve (b”) approximately parallel to the cambial zones. These represent the very beginnings of the hard bast cells. They are richer in content and accompanied by pouch-like cells, which, in their longer axis, usually run parallel to the young bast bundles and contain raphides of calcium oxalate (o). The bark tissue produced from the youngest bark already formed at the time of cutting and containing thick-walled, but short and broad hard bast contains its calcium oxalate in the form of stellate druses, or separate crystals, similar to those which occur chiefly in the normal bark (0’). At the place of the transition, raphides and stellate druses are often separated from each other only by two cells. Here also only the loosely constructed tissue contains raphides. The parallel arrangement of the crystal-containing cells, with the bast fibers, is seen best in tangential section in the cherry; here the base bundles, lying in a net work upon one another, are found to be accompanied by parenchymatous cells lying close against one another and elongated. Almost every one of these contains a crystal of calcium oxalate. In the grape this is less sharply marked and becomes relatively indistinct as the tissue, as a whole, loses its differentiation in the overgrowth walls. In this less differ- entiated part may already be recognized thicker walled elements lacking the deposition of calcium oxalate in the surrounding tissues. The calcium appears in the cells formerly filled with starch, a fact which indicates that the calcium oxalate is one of the end products in the solution of the carbo- hydrates. Therefore, no calcium oxalate is found in the outermost peripheral zones of the overgrowth edge because these zones consist of the first formed tissue of the quickly growing undifferentiated callus projecting beyond the cut surface. In these the material has been utilized entirely for cell increase and is not deposited in the end as reserve starch. On the whole, however, 793 only a few peripheral cell rows always remain free from starch and free from subsequently formed calcium oxalate, for the tissue which extends beyond the cut surface, and which warrants the name “callus” only so long as it is absolutely undifferentiated, soon shows a difference in its structure and passes very rapidly from the callus stage into that of the overgrowth edge. Soon after the formation of the peripheral cork covering, a meristem zone appears also in the interior of the callus tissue and represents the continuation of the cambial ring of the normal piece of the vine within the overgrowth edge. Besides this meristematic zone, the first traces of a bast body may also be recognized in the separated parenchymatous cells lying scattered close under the cork zone. These cells appear to have somewhat more strongly refractive, easily swelling walls (b”’). In some of these I think I have recognized indications of sieve pores similar to those found in the tangential walls of normal bark sieve cells (sz), so that the conclusion may be drawn that the first differentiation of the callus tissue, appearing almost simultaneously with the formation of the new cambial zone, consists in the formation of sieve cells within the bark. The tissue formed in the cambial zone appears, in Fig. 183, to be divided longitudinally by the medullary ray cells (m). These are elongated radially, have clearer contents and like the rest of the tissue are small celled at the periphery of the overgrowth edge. Their approximately perpendicular direction changes gradually into the normal horizontal one as the rays extend into the normal tissue of the uninjured piece of the vine. In the youngest portion of the callus edges, where the tissue lying next the cork border first arose, one finds the wood lying between the clearer medullary rays to be short, thin-walled and parenchymatous. The further the wood is examined back toward the normal tissue, the longer and thicker walled it appears and it passes from its radial direction more and more into the longitudinal elongation of the normal wood elements. The earlier in the year the girdling is undertaken, i. e. the longer the newly produced cambial zone of the overgrowth wall produces wood, so much the more do the later formed elements approach normal wood in length and form. Scalariform vessels (g,2) appear in this thin-walled parenchymatous wood as the first thick-walled elements; they have at first the size and arrangement of the wood parenchyma cells of the surrounding tissue but assume gradually the form and arrangement of normal vessels the nearer they approach the uninjured parts of the wood. In opposition to de Vries, I must maintain that the short duct cells are not always the first formed thick- walled elements. When the callus at the lower margin of a girdle is very weakly developed, the wood parenchyma often passes over directly into normally arranged, slightly thickened xylem elements, without the previous appearance of short duct cells. In the callus at the upper margin of a girdle which in the same length of time has developed more than twice as extensively as the lower callus, the cambial zone is broader, all the elements are more numerous and the 794 beginnings of the vascular bundles in the callus always start with duct cells. The formation of these cells takes place the earlier the nearer to the old wood they are formed. Their form, size, thickness of wall and arrange- ment will be more nearly normal the further back the tissue lies from the cut surface. The vascular strand (g,2) of this tissue grades gradually into the normal wood formed before girdling, thereby forming a pseudo-secondary growth in that area. According to the anatomical condi- tions shown in Fig. 183, we may say that the girdling has produced an un- usual loosening of the wood in the uninjured part of the vine adjacent to the wound. In this way the vascular bundles, which are formed of vessels and thick-walled tracheids on one side of the cambium and of the thick-walled phloem fibres and sieve tubes on the other, and which, in normal wood, are arranged close against one another in concentric circles, are separated and broken up into single strands by masses of parenchyma. These strands, g,2 (vascular strands), and b’ (phloem strands), the elements of which con- stantly become fewer in number, change constantly and continue into the callus, which is gradually covering the girdle. We may best see by means of cross sections taken at different heights through the callus, what happens to the vascular cylinder which in the unin-. se we: OF: ~ 3 “ el ‘4 jured portion of the vine consists of the wood and the phloem rings, only slightly broken by few-celled medullary rays. This cylinder finally is separated into single strands by the growth of Fig. 184. Cross-section through aring- parenchyma induced by the girdling. fees Bey i Stun ie Gee The strands gradually become narrower as they pass outward radially and tan- gentially in wavy lines, they are at first distinct, but later anastamose forming a net and finally split up into isolated strands arranged in fans. — iu ies a a\.\ Sy 795 For the sake of greater clearness, the cross sections shown in Figs. 184 and 185 have been taken from the upper similarly constructed but more Oo Be SE 4 oil Ly} iow) CO tea nity IL ey i * n “As pe { '( /f y ue ‘si \ SATO DRG IGOATID Coli eI ee U SPLITS Wn IeG Nah fay Cea Lf an Se ON f RN OW Lani \ con SES GDA ONY ih ei SY ia) ‘s mg SS PS jena eae CA J 0 CE ae grasgustese HOO CEES SESSNINNG ¢ Fig. 185. Cross-section through the ringing roll at a considerable distance from the place of its appearance, i. e. where it is more luxuriously developed, as would be found in Fig. 183, possibly in the plane k to wh. strongly developed callus of the same vine, which furnished the longitudinal _ section, Fig. 183. 796 Fig. 184 shows the callus in cross section at the place where it leaves the old bark, i. e. about at S to S’ in Fig. 183. Fig. 185 is a cross section through the middle of the projecting part of the callus, i. e. about in the place k to wh in Fig. 183. In Fig. 184, H represents a part of the old wood formed before girdling. g’ indicates the wide, scalariform vessels of which those lying nearest the cut surface S to S” have filled with tyloses (t) asa result of the injury, and consequently have become impervious to air; h shows the tracheids in cross section. SS’ to C’ (in Fig. 185, C to C’) is the new wood formation of the callus. We find that the medullary rays (m), from the normal tissue (/7), are continued, after a short interruption, into the callus. The medullary rays become constantly broader; the vascular bundles, the xylem elements of which in normal wood are closely packed, are separated further and further by the constantly widening medullary rays. The bundles thus have fewer elements and normal tracheids are no longer present. The strand (st’) consists only of short, wide vessels, and narrow ones with transverse walls, together with wide, thinner walled wood cells, abutting on each other transversely. The single strand in Fig. 184 (st) in the normal wood has divided in the tissue of the callus into two strands (st’), and these again into four strands in the part still further from the cut surface (Fig. 185 st’), at the same time the new bundles are pushed out of their original position by the formation of new medullary rays (Fig. 185 m’). They advance as separate groups toward the periphery of the constantly thickening callus. With the broadening of the tertiary medullary rays these thin vascular strands (Fig. 185 st’), which (in longitudinal section) seem to branch as they growth in length, separate farther and farther from each other until they finally disappear entirely near the outer edge of the callus. The terminals of these strands are short, broad, porous cells of wood parenchyma. It is well known that each vascular strand is made up of both phloem and xylem. The wood and phloem are sister elements' In Fig. 184 b, we see a group of wood fibres, which belongs to the xylem strand st; b’ and bb’ represent the phloem, belonging to st’, the cells of which, analogous to wood elements, have become broader. The radial thickening of the phloem cells is not very well shown in the drawing. In the fall, when the grapevine has cut off the cortex by a cork zone, the sinuous cork layer (#), in the callus, has divided the phloem bundles into two parts (Fig. 184, b’ to bb’) ; c’c’ represents in Figs. 184 and 185, the cambial zone. In Fig. 185, 0 is a pouch cell with calcium oxalate in the form of raphides. In some pouch cells sharp, jagged very small protuber- ances project from the inner cell wall. The first differentiation in the callus may still be recognized after it has passed over into the finished overgrowth of the callus, beginning at the outer- most cork layer; i. e. if, in Fig. 185, the section begins at the part curling farthest downward and then advances upward. If we designate the part 1 Ratzeburg, Waldverderbnis I, 70. 727. adjoining the old wood (Fig. 183, 2’ to S), as its innerside, in contrast to the spherically convex outer side, the parenchymatous tissue of the inner edge, lying directly under the cork zone, is seen even in the second sections to color more deeply when treated with iodine than does the corresponding part of the opposite outer side. In the same way, by using iodine, a radial division of the tissue may also be recognized, for certain bands at first only one to three cells broad take on a deeper color than the broader parts lying between them. A difference may be seen also in the form of the cells in the first cross sections, for those lying nearer the outer edges appear rounder than the more densely crowded ones nearer the inner edge; also all the cells, lying directly under the corky outer layer, are smaller than those at the centre. The lighter colored bands contain cells with a greater radial elon- gation, the first indication of the medullary rays. The zone of the renewed cell division, which will form the beginnings of the later cambial rings, lies close to the inner side of the callus roll adjoining the region of cells which were the last to divide to strengthen the peripheral cork zone. From there, in the subsequent cross sections, the division zone moves farther and farther from the old wood (compare the curved course in the longitudinal section, Fig. 183, c to c’), reaching its greatest distance from the old wood outside the plane in which the girdling occurred and again within the old bark, approaching the normal wood until it takes up the usual position of normal cambium. The principles that have been discussed here in detail with reference to the grape are expressed in any kind of girdling, the special structure naturally varying with the kind of plant. Czapek' has shown that, of the conducting elements, only sieve tubes and cambiform cells come under consideration for all assimilating products, indeed, the paths which convey substances are straight, even in the phloem. The phloem parenchyma, like the medullary rays, serves as storage tissue. The deposition of reserve substances is influenced by girdling, inasmuch as (according to Leclerc du Sablon?) the roots of trees girdled near the base of the trunk in the spring at the time of sprouting are richer, and the trunks poorer, in reserve materials, than those of trees which have not been girdled. The leaves of the former to be sure are not so green, but contain much more reserve materials than ungirdled specimens and according to my obser- vations color much earlier in the autumn. INJURIES TO THE BARK. A. HustoricaL SURVEY. The processes of healing a wound which has exposed the wood all the way around the trunk often a meter in width, produced by the removal of 1 Czapek, Fr., Wher die Leitungswege der organischen Baustoffe im Planzen- korper. Bot. Centralbl. 1897, Vol. 69, p. 318. 2 Leclere du Sablon, Recherches physiologiques sur les matiéres de reserves des arbres. Revue générale de Bot., Vol. XVIII; cit. Bot. Centralbl. v. Lotsy, 1906, No, 43, p. 447. 798 all tissue down to the cambium, have been the subject of observation for more than 100 years. Thus Treviranus' quotes that L. Firsch found some apple and pear trees on an estate in the Province of Brandenburg, from which all the bark had been removed from the points of insertion of the lowest branches down to the roots, completely around the trunk, so that the white wood could be seen everywhere. The trees were covered again with new bark. Frisch assures us that this experiment will always succeed if made at the time of the solstice and if the exposed outer surface, over which the sap is spread uniformly with a feather, is protected by linen or split cane against the sun and wind*. The celebrated experimenter, Duhamel’, removed a ring of bark from several young trees, elms, plums, etc., 7 to 10 cm. wide down to the wood, at the time when the sap was flowing and surrounded the wounds with glass cylinders, which were closed at the top and bottom against the uninjured part of the trunk with cement and tissue. He found delicate, jelly-like warts forming on the exposed wood surface, and pushing out between the wood fibres of the sap wood (des mamelons gélatineux qui sortaient d’entre les fibres longitudinales de l’aubier). These little warts, which push out under very tender, probably left over, phloem lamellae, were at first white, and half translucent, later gray, and after 10 days (on April 18th) green. These new structures, broadened in the course of the summer and finally uniting, produced a rough bark beneath which delicate wood lamellae were recognizable. ‘“‘Ainsi il est bien prouvé que le bois peut produire de l’écorce et que cette écorce est des lors en état de produire feuillets ligneux ss Knight made similar experiments and obtained similar results. He found once® on Ulmus montana, a regeneration of the bark when the wound had not been covered. The tree grew in a shady place. Knight found in old topped oaks, with an incompletely formed new bark growth, that the jelly-like warts had pushed out from the parenchymatous cell tissue and “in many cases new bark was formed in small and isolated portions only on the upper surface.” Meyen* quotes Werneck’s observations, according to which the regen- eration of the bark will take place only if the barking happens about the 25th of June, when the trunks are still young and the wounded place is “very carefully protected against drying by a hollow and closely adjusted bandage.” We find Meyen’s own theory® in the description of his experiments given in his Phytopathology. On April 30th, 1839, in warm sunshine he 1 Treviranus, Physiologie der Gewachse, Vol. II, 18388, p, 222. 2 Duhamel, Physique des arbres 1758, Vol. II, p. 42. Vol. VII, p. 63, and loc. cit., p. 44. Vol. VIII, p. 66, 67. 3 Treviranus, loc. cit., p. 223 (Beytr. 223). 4 Meyen, Neues System d. Pflanzenphys. 1837, p. 394. 5 Meyen, Pflanzenpathologie, published by Nees. v. Esenbeck. Berlin 1841, p. 14. * Miscell. Berolin. Contin, II (1727), 26. 799 removed the bark from the little trunks and larger branches of the hazlenut, the snowball, Syringa and willow and, like Duhamel, enclosed the barked places with cemented glass tubes, which in addition were wrapped with paper, although he made the experiments in thickly shaded places. Jelly- like drops were “sweated out’ here also, “which always occurred on the places where the medullary rays appeared on the upper surface of the wood.” Microscopic investigation of this “sweating” showed the warts to be composed of tender cell tissue, “which enlarged constantly because of the gum in the sap, exuded by the medullary ray cells.” The greenish color, which these new structures assume, arises from the chlorophyll grains. In the course of the experimental year these structures reached a thickness of 11 mm. but shrivelled greatly when dried. Meyen cannot ascribe the significance of bark to these new structures, which are also produced naturally in shady places. For “no separation into different layers, of which the normal bark of the same tree is composed, can be seen and moreover there is no trace of sieve tubes in it, which are, of course, very important * This physiologist, very distinguished in his time, who according to the Mirbelian theory considered the cambium to be a structureless sap, which brought forth such cell structures as those from which it had appeared, has indeed the merit of having made use of the microscope to investigate the new structures which appeared with the healing of bark wounds. He was not fortunate enough, however, to observe the production of wood among these new structures and to prove the analogy between these forms and normal bark. Probably the moist air and heavy shading from his cylinder were to blame, since as we shall see these factors influence considerably the charac- ter of the new structure. Dalbret? experimented earlier than Meyen, for on the 21st of June he barked an ash and a walnut, enclosed the barked places in a cylinder and obtained the same results as Duhamel. Th. Hartig*® in the spring of 1852 at the time the new annual rings had begun to develop removed the bark from 30 to 40 somewhat older oaks for 6 to 8 meters above the ground and in August found the majority of the mutilated trees bore as dense foliage as the adjacent ones from which the bark had not been removed. On 5 or 6 young trunks a scabby eruption, pressed out from the medullary rays of the wood, had formed “curiously” only on the sunny side. Anatomical investigations showed that the erup- tion, quite independent of the phloem and cambium, had come from the wood alone and was a product of the medullary rays. 1 Pflanzenphysiologie, Vol. 1, p. 390. 2 Journal de la société d’agronomie pratique 1830; quoted by Trécul in “Accroissement des végétaux dicotylédonés ligneux.” Annales des sciences natur. III, Serie, Vol. XIX, Paris 1853. 3 Th. Hartig. Vollst. Naturgesch. d. forstl. Kulturpfl. Deutschlands. Berlin 1852. Explanation of the figures (plate 70, Figs. 1-3). 800 “The new structure begins with the appearance of a layer of cork cells at the periphery of the healthy medullary ray tissue, cutting off an outer, dead part. The living part of the medullary ray now develops several layers of parenchymatous cells about its circumference, which cells turn green like the medullary tissue already present. By the increase of the parenchymatous tissue around the medullary rays, a callus roll is produced, which rapidly becomes larger and constantly presses farther outward the cork layer which begins with the formation of lenticels. “The new cell tissue does not develop on any one place from the living medullary ray, but as everywhere new cells are formed in all places inside the cells already formed; these reabsorb the mother cell, grow out to its size and widen the mass on all sides. In spite of the widening of the callus, due to the growing cell tissue, the living part of the medullary ray, nevertheless, always retains the same circumference, the same size, number, form and position of the cell tissue constituting it.” “When the callus reaches a certain size, different parts become unusu- ally thick walled, as is also the case in the normal course of the life of the bark (stone cell aggregations). Further, on each side of the living medullary ray not far from its tip, a vascular bundle develops in the cell tissue, which consists of pitted tracheids and vessels between the medullary ray and the cork layer.” By the fusion of the individual coordinate tissue zones of the new structures, which up to that time had been completely isolated and wart-like, a continuous bark layer covered with a cork layer is produced, differing only by the radial arrangement of its cell elements in cross section from the structure of the normal bark. ‘Along the sides of the tip of the medullary ray, the development of the wood advances up to the formation of a connected wood layer, traversed by the cell tissue of the old medullary rays just as by newly formed, smaller ones. The various wood bundles consist of tracheids and fibres. True spiral elements are lacking. A line of division between the wood and the bark (Meristem zone Ref.) is formed more and more sharply with the advancing development of the wood, although no trace can be discovered either of phloem fibres or of sieve tubes.” Th. Hartig’s observations, which represent an important advance, show, therefore, that the development of the new bark on a bark ‘injury, takes place at the expense of the nutritive substances present in the wood and begins with the formation of a callus tissue around the tips of the medullary rays. It cannot be learned either from the description, or from the drawings, which cells initiate the callus formation. Trécul! fills this gap with his thorough anatomical investigations, which prove at the same time the participation of the whole young tissue left on 1 Trécul, Accroissement des végétaux dicotylédonés ligneux. Annales des science. nat. XIX, p. 165. Sol the barked wood stem and not merely that of the medullary rays in the formation of callus. Nevertheless, under special conditions the medullary ray cells can alone cause the formation of callus and yet the case often occurs where the callus formation is initiated by the young wood cells alone. The young wood cells, the medullary ray cells and the narrow elements participate in the callus formation by a transformation into parenchyma cells which now increase in number’. The youngest cells, left on the wood cylinder, widen, elongate and divide. The end cell of the last row of callus cells becomes largest. It is often spherical, or club shaped, and the new cross wall is produced generally in this stage. The new end cell now formed by the cross wall repeats the process. The older cells, lying back of it, elongate and divide. Besides this kind of callus formation, Trécul observed still another case. While the outermost remaining cells develop into callus tissue, by distention and division, it also happens that they show only a slight develop- ment, while the innermost young wood cells, lying beneath them, take over the role of the actual callus former. Trécul sketches (pl. 7, Fig. 11) a longitudinal section of the elm, the callus on the edge of which consists of short, isodiametric cells. This gradually drying layer has been pushed up from the wood by means of a thick callus layer, of which older cells now adjoin the wood. The youngest cells most distant from the old wood, lying directly under the outpushed dying layer, have stretched radially and formed radially parallel rows. Both cases of callus formation can occur at the same time in the same specimen. Probably the innermost layers of the exposed cambial body are incited to increase by the drying of the outermost layers. As my experiments show, all the cells of the cambial region can partici- pate in the callus formation, not only the young wood cells, as de Vries thinks, but also the young bark cells. It depends alone upon which cell layers are left when the bark is removed. If it is loosened in such a way that only a few of this year’s sapwood cells still capable of mmcrease remain on the old wood, the callus must be formed from them; if, on the other hand, the very youngest cambium cells remain in place, they take over this formation of callus, while the underlying young sapwood develops, accord- ing to its position, into differentiated wood with vessels and is changed only in so far as all its elements become shorter, broader in the radial dimension and thinner walled. Trécul*, in his Fig. 5, pl. 3, of a linden, gives the best example of this case. We will use this (see Fig. 186) to confirm our theory. JB indicates the young wood of the current year formed before the removal of the bark, 1 “Les fibres ligneuses, les rayons médullaires et les vaisseaux d’un petit diamétre eux-memes sont métamorphosés en tissu cellulaire proprement dit; car il y a une métamorphose réelle de ces organes elémentaires en tissu utriculaire ordinaire, et ensuite multiplication de ces utricules nouvelles. 2 "Trécul loc. (eit. Ds Lor. 802 with its vessels (v). A to A’, according to Trécul, is the old bark of the previous year’. The split, which pushed up the bark, extends horizontally above the highest vessel (v) to the point marked +’; from there it runs downward toward the right almost to the thin-walled, last-formed cells of the previous year, so that the whole group (g) should be considered as a new structure. At +, the loosened bark has removed only the outermost layers of the youngest wood, or has possibly extended only to the central cambial zone, so that the whole sapwood has remained in place. The outermost cells elongate (/) and divide (J). The upper cell (7) of each row, cut off by the new wall, repeats the process. 24 ai Tor LAY ene i A 208 Oma ray Oia oAt VY Fig. 186. Callus formaton from young bark cells in a barked trunk. (After Trécul.) The young wood (sapwood) has been stretched radially by the injury, i. e. by the removal of the bark pressure. It forms shorter cells with wider lumens but has remained thin-walled, while the vessels already started have matured. From «+ out, the young sapwood has been removed with the loosened bark and on the wood of the previous year only a few young wood cells of the current year were left. These cells have now taken over the formation 1 It might seem strange that the annual ring at A’ ends with a very thin- walled spring wood, but such cases actually occur. I obtained from the Hifel in January larches diseased with canker, the annual ring of which had formed over the summer wood a layer six cells thick of thin-walled spring wood. 803 of callus, which naturally lacks vessels, though it reaches the thickness of the adjoining parts by a more rapid increase in the lumen of the cells?. Opinions differ greatly as to the life period of barked trunks. The best example of an unusually long life period in trees which have lost their bark extensively, and have not replaced it, the exposed wood con- sequently falling victim each year to decay, is furnished by Trécul in his description of the linden at Fontainebleau*. Yet we have still earlier observations. In 1709, Parent reported the following observation to the Academy: An elm in the Tuileries, which at the beginning of spring, 1708, had lost all its bark nevertheless developed its leaves, even if somewhat less vigorously, and kept them all summer. Duhamel* expresses himself as follows in this connection: Trees with bark wounds, which remain uncovered, gradually go to pieces (sometimes not until four years later). At the sitting of the Academy on May 11th, 1852, Richard related a case, similar to the one described by Parent as something very extraordi- nary, since, in the majority of cases, the trees die soon after such injuries. Gaudichaud* disputes this latter statement by referring to trees in St. Cloud, in the Luxembourg, and at Fontainebleau, which after such injuries lived a great many years, although the outside of the exposed trunk was partially destroyed. At the sitting of the Academy of March 7th, 1853, the same botanist returns to this point and now cites the linden at Fontainebleau. According to Trécul, this tree was planted about 1780 and in 1810 was very irregularly barked by some dump carts. On the north side, the barked place was 32 cm. long, and began 57 cm. above the ground, while on the south side it was 4.05 m. long and began immediately at the surface of the soil. The barking extended completely around the tree and yet, despite this, the tree lived for 44 years (it did not die until 1854). The diameter at the place of injury was 20 cm., below it, 18 cm. The surface of the injured trunk, the centre of which was so cut by the carts that the diameters of the remainder were 10 and 5% cm., was entirely worm-eaten and dry. After the dead wood had been removed, the remaining living central portion was 1 To characterize Trécul’s theory, we will give his explanation of the figure, loc. cit., p. 191: A, A’ bois de l’année précédente, V, vaisseaux de ce bois; R rayons medullaires—B jeune bois formé au printemps avant la décortication. ‘Tous les éléments de ce jeune bois, et la partie la plus externe A’ de celui de année précé- dente, ont subi un amincissement dans leur membrane. Les cellules externes des rayons médullaires R ont donné lieu 4 une multiplication utriculaire, quelquefois abondante en r. La multiplication commence aussi en ], I’, dans les éléments du tissue ligneux. En g, cette multiplication s’étend a toute la couche l’année et meme aux fibres ligneuses les plus externes A’ de l’année précedente. Les vaisseaux qui existaient primitivement dans la couche de cette année, comme en B, v, sont disparu en g. 2 Trécul, M. A., L’influence des cortications annulaires sur la végétation des arbres dicotylédonés. Annales di. science. nat., IV Serie, Vol. III, Botanique 1855, p. 341. 3 Physique des arbres, Vol. II, p. 46. 4 Compt. rend. (from 31st of May, 1852). 804 found to be only 2% cm. thick; it was very juicy and looked like young wood. Almost all the root nourishment for the top of the old tree had to ascend this slender cylinder, and yet in the year observed, viz: March 29, 1853, the top developed just as early and had as many leaves and blossoms as the other lindens. But this tree, which at its base had sent out a number of branches and leaved sprouts 5 to 6 cm. thick lost its foliage in August. Trécul ascribes to these shoots the maintenance of the basal part of the trunk, below the barked place; they prepared for it the plastic material which a normal trunk receives from the top through the bark. Lindley? describes an analogous process in a birch branch which had been completely robbed of bark and sapwood near the place where it joined the tree and yet had continued to grow for several years. Th. Hartig? found that a linden, from which a ring of bark had been removed, was still alive 9 years after the operation; in fact, its fertility was increased. The court gardener, Reinecken, in Greiz, reports a grafted elm 10 cm. in thickness, which for 6 years was connected with its stock only through the wood and not through the bark. The Inspector of the Gardens, Roth, in Moscow, also found a red beech 75 cm. thick and 25 feet high, which for 45 years had never been connected with the parent trunk by the bark (as Goppert states) but was connected only by the wood layers. Nevertheless, it grew vigorously and was finally broken off by the wind. In the botanical garden at Breslau, a linden 14 m. high and one-third meter thick blossomed every year. Its bark had been removed completely and carefully in 1870 for a distance of one-third meter, and above the barked place, an overgrowth layer scarcely 2 cm. long had grown in the first 2 years*. The result of the barking cannot be determined in advance. The life duration in the barked trunk depends considerably on the variety of tree. Rapid growing, deciduous trees best endure such extensive injuries. Satis- factory results have not as yet been reported for conifers. Hartig* did not find any new formation of bark but discovered that the piece of the branch below this barked place down to the next lower branch had developed into very resinous wood. Stoll’ also could find no regeneration of bark. He states, however, that Nordlinger had observed a new formation of bark but had expressed the opinion that the newly formed bark was not capable of conducting the descending sap current. Stoll states of monocotyledons that he found a cicatrization of wounded surfaces in a Dracaena, from which he had removed the bark. It was kept in a greenhouse. The resulting phenomena depend not only on the plant variety but also on the time of the manipulation and the ease with which the individual can 1 Gardener’s ‘Chronicle of Nov. 13, 1852, p. 726. 2 Hartig, Th., Folgen der Ringelung an einer Linde. Bot. Zeit. 1863, p. 286. 3 Goppert, Uber das Saftsteigen in unseren Baéumen. 57. Jahresber, d. Schles. Ges. f. vaterl. Kultur 1880, p. 293. 4 Folgen der Ringelung an Nadelholzasten. Bot. Zeit. 18638, p. 282. ec 5 Uber Ringelung. Wiener Obst- und Gartenzeitung 1876, p. 167. 805 produce accessory organs in the form of adventitious buds and roots. In fruit culture, the girdling process is used only as the most extreme means of obtaining the setting of fruit in trees exhausted by a too vigorous forma- tion of wood. PERSONAL OBSERVATIONS. To test the processes described by earlier observers, the bark was peeled from a considerable number of strong, about 5 year old, sweet cherry tree trunks in July. The upper and lower parts of the barked places were scraped for a length of 2 to 4cm. with a knife to destroy the sapwood; the remaining part of the exposed surface was left untouched (see Fig. 187). Some of the experimental saplings grown on open ground were bent from their natural, vertical position to one inclined toward the ground. : The formation of new bark did not take place in all specimens, but in a few it occurred to a considerable extent. Among the latter were found some small specimens which had formed new bark on all sides with the exception of the perfectly dry, scraped places near the upper and lower edges of the cut. The new bark, therefore, had no connection whatever with the old bark. The initial stages had appeared simultaneously on all sides. The thickness of the new bark, however, was more than twice as great on the lower part of the exposed surface as on the upper part; in fact, at the lower edge, it had spread in Fig. 187. A barked trunk of a sweet short bands with waxtlike thickenings. Chery. 20 yoo ae ees Ree in places on the scattered scraped edges of the place barked. areas. In an inclined trunk the con- tinuation of the bark had turned away from the scraped place and started to grow down toward the ground, as Fig. 187 e’ shows. In Fig. 187, u is the lower and w’ the upper overgrowth edge of the peeled surface. This overgrowth edge, which in structure resembles the callus of the grapevine, has not been developed all around the trunk, since 806 a part of the bark has been left standing in the loose strips ] andJ. New wood with bark (nh) has been formed in places on these strips at a little distance from the place of their attachment. The real exposed surface of the trunk has been cut off from all connection with the overgrowth edges u,u’, because at i and 7’ the young wood, as already mentioned, had been scraped off all around the trunk, in this manner forming an isolating band. The new formation of bark elements with the beginnings of wood had started on the exposed surface, cut off from all connection with the bark and sapwood layers. These new structures do not form a connected mantle but consist of isolated groups. On other, more carefully barked trunks, Fig. 188. Cross-section through a newly produced tissue outgrowth on the exposed wood of the barked sweet cherry trunk. the new bark extends perfectly uniformly over the bared surface. In the middle of this surface an irregular zone of exposed wood has remained without any new formation. Therefore, the new product (b) is not con- nected with the upper one (a), which is considerably thicker. Common to both and just as clearly recognizable in all new structures on other trunks is the thickening which increases from above downward in each individual tissue strip and in its appearance resembles perfectly the phenomenon produced by the drippings of a badly burning candle. In fact, the lower end of the new structure, resembling the callus, is poured in the form of drops over the parts of the wood which have remained naked (ee). On 807 the trunks which had been kept inclined intentionally the new structure hangs free from the axis, like the drippings of a slanted burning candle and, in response to the force of gravity, grows downward like an isolated pendent braid, perpendicular to the earth’s surface. In order to show that the various small spots, as has been observed by Meyen, Th. Hartig and others, possibly are not merely productions of the medullary rays, one such structure is shown in cross section in Fig. 188, and in longitudinal section in Fig. 189. Fig. 188 H indicates the old wood, the barked surface of which (¢ to f) is partially dead; only the middle portion has started new production (N-N). The production began with a raising of the outermost cell layer by the rapidly forming products of division of the immediately underlying sap- wood layer and, in fact, also of the young wood cells together with the vessels and the medullary ray cells. After the cork zone (k), which is becoming thicker, has surrounded the comparatively scanty new parenchymatous tissue (7 to p), an inner meristem zone appears very early at first in bands and then connected. This meristematic zone is new cambium (c to c), which now takes over the secondary growth of cork. In this way the two processes of growth, which can take place in the formation of bark on barked surfaces, differ considerably. If, as is the case in enclosed wounds, which have been kept moist, the new bark begins with a great production of callus, together with a long continued division of the peripheral cells, as Fig. 186 shows, the formation of the outer cork zone and especially the production of the inner meristem zone takes place very late. In contrast to this, as in the present case, the wounded places which have been exposed unprotected to the hot summer sun show the second process, since the outermost remaining cells quickly thicken their outer walls, collapse and in this way furnish for the immediately underlying layers the necessary protection against drying. In this only a slight forma- tion of parenchyma, but a very rapid appearance of the cambial zone, takes place. It seems that the inner meristem zone has developed the more quickly into a callus the more rapidly a sufficient bark pressure is produced by suberization. The next production of the new cambial regions (Fig. 188, c-c) con. sists in the formation of isolated new vascular bundle strands, which, beginning with scattered short vessels (g), rapidly increase with age the number and size of their elements and thus assume a wedge-like form which constantly narrows toward the medullary ray regions (m) and at the begin- ning is very broad, until structure and arrangement of the elements have reached the normal stage of the unbarked trunk. To each xylem part belongs a phloem part (ph), near which appear numerous cells containing calcium oxalate (0). We see that the appearance of the vascular bundles in the parenchy- matous ground tissue is the same as in the callus. This is true wherever 808 a parenchymatous ground tissue of considerable extent has been formed. By cross-division of a number of cells which at first do not differ in form from the ground mass and are but slightly elongated radially and longi- tudinally, a number of meristematic centres are formed from which the beginnings of thick-walled tissue elements start. By a very luxuriant callus-like cell increase from the beginning, two parallel zones of meriste- matic strands can be produced simultaneously, with the tissues as they grow older. These parallel zones mature into two wood areas, which remain distinct until they have become very thick. The formation of a Rue Foes ArT Fig. 189. Longitudinal section through the basal part of Fig. 188, about in the zone to be found from g to p. isolated vascular bundles in the bark of our trees is not rare as is said to be shown in tuber-gnarls. The first processes of change in the sapwood of the barked cherry tree may be recognized in Fig. 189, which gives a longitudinal section from the base of the barked portion in Fig. 188. H is the old wood, which because of the cut has not changed any further, with its loosely reticulated vessels (g). In the sapwood, lying just outside it, the cut has so affected the nearly mature vessel (g) that its imner cavity has become filled with tyloses; these have been used to form new cells and been changed into wood paren- chyma. The new layer of wood parenchyma consists of only a few cells 809 and exhibits immediately the first stages of thicker walled elements in the form of shorter, porous vessels (gz) as the first production of the newly formed cambial layer c-c.. Each successive tissue layer, formed from the cambium, has longer vessels; at h, we find thin-walled elements, shortened, to be sure, but unmistakably resembling the normal wood cells ; correspond- ing to these thin-walled elements, the phloem elements appear at s in the bark (7) : # is the xylem ray, ph the phloem ray. If in the early spring, when the bark is easily loosened, homologous cells are torn around the whole circumference of the trunk in the process of removing the bark, thereby causing a reproduction of similar bark, arising from similar elements, we find that the bark wounds become more irregular from the time of the leaf development until late in June. More cell groups remain attached to one place on the wood cylinder than to another and the new structures differ accordingly. It thus happens that pieces of sapwood of the current year, which contain vessels, are forced up by a callus tissue produced beneath them. If the bark wounds are left uncovered, the new formation of bark will in many cases be more doubtful. According to my experience, the bark regeneration succeeds better in July, for some trees in August, than in April, May or June. The maple and alder must be barked earlier; numerous experiments made on these trees in August gave no results at all. If the bark wound, made in the heat of the day and left without any protection whatever, is investigated after some hours (sweet cherry trees were used for the experiment) it was found that the color of the originally white wood cylinder had changed to yellow. The wound surface owed this color especially to the browning of the medullary ray cells. The browning is more intense on the southwest side than on the north side. The medullary rays are easily recognized by the fact that immediately after the removal of the bark they project somewhat above the barked surface. This fact indicates that the medullary ray cells at the same radial dis- tance from the median line of the trunk have firmer walls than the young wood cells, i. e. their development is further advanced than that of the equally old cells of the vascular bundle. Such an advance of the medullary rays over the other tissue will stamp them as a tissue of increase, which creates space for the newly produced wood tissue im the direction of the radius of the trunk. This prominence of the medullary ray groups takes place also in part because of the more rapid outcurving of their outer walls, resulting, as a rule, from the barking. These outer walls (unprotected) grow thick very rapidly and turn brown. The cell contents increase in the medullary ray and young wood cells lying immediately beneath the wound surface; masses of cyptoplasm and later of starch appear, the former, when treated with glycerin, rounds up SIO into scattered yellow globules. Beneath the outermost cell layer, which at once collapses and forms a protective mantle for the underlying young tissue, the new cell formation begins by means of cross walls. The medullary ray, the cells of which as a rule are in advance of the others, is frequently broadened by this new formation since the later ray cells push out in a fan over the adjoining wood cells. It has already been stated that often the medullary ray cells can remain partially or entirely undeveloped. Then the parenchymatous callus cells, which are never round but always polygonal, and are produced from the young wood fibres, spread over the medullary ray groups. As a rule, how- ever, the whole tissue participates equally in the formation of a thin callus layer which pushes out the outermost cells of the old wood. By drying these old cells produce a protecting layer. While the callus formation through the excrescent apical growth of the various cell rows is very considerable in the barked places, which are kept protected and moist, it is very small in unprotected places. Cork is formed at once beneath the dried, outer cell layer and becomes a constrict- ing, firmly protecting girdle for the underlying young tissue, which is turning green. The new formation of bark on barked places may occur in still another way. If the bark wound is made in such a way that young bark cells form the outermost layers of the exposed surface, they initiate the callus forma- tion and the real cambial layer is only slightly disturbed. The transition of the callus into normal tissue takes places in general in such a way that isolated, short celled, vascular strands occur deeper inside the callus after the cork cells have begun to form about its edge. About this time thick-walled, slightly porous, irregular, or polygonal cells are found, possibly in the same radial direction but more in the vicinity of the peripheral zone of the callus. These cells are the first traces of a phloem formation. In many trees, the first phloem elements in the form of aggre- gations of stone cells are found isolated or soon united into groups. In one zone, cells with a cloudier, denser content are found between the phloem and the vessel elements. In them occur a great many rectangular walled cells, somewhat stretched in the direction of the long axis of the trunk, which might be the very first stages of the newly forming cambium. From this cambium are produced gradually the elongated elements which finally develop into normal wood and fibres but no more long, spiral elements seem to be formed. With the development of these normal fibres, the last to appear, the iew bark may take on the function of the uninjured bark. THE BENDING OF THE BRANCHES. Branches are often bent as a special aid in fruit culture. Experience shows that shoots which grow upright develop most quickly and strongly and that their growth in length will be the more retarded, the further the SII branch inclines from the vertical toward the horizontal. The same retarda- tion of the apical growth is found, however, if branches are bent artificially from a natural horizontal position toward the downward perpendicular, ‘Figs. 190 and 191. Artificially bent apple twig in longitudinal and in cross-section. from which it is evident that the bending itself exercises the arresting influence. No externally perceptible wound is produced if the manipulation is carefully carried out, though a somewhat greater tension may be seen on the upper side and a folding of the bark on the under side. Fig. 192. Fold in the bark on the under side of the bend. The development of the buds is affected by the bending, since the buds below the place of bending swell up more and, not infrequently burst pre- maturely. The success depends upon the time and place where the branch 812 is bent. The nearer the tip of the twig the bent place lies, the less the internal injury is, but also the less the desired result. The buds beneath the place bent will then develop into slender leaf shoots. But when the branch is bent near its base the buds stimulated to growth will develop only short shoots; these, however, show a tendency to change to fruiting wood. [eal ESSN GGREOOUOOO eso aS Fo OSE, Sosa, SS OO BEDS SSS = x ———~. oxow= > — oo 2 S * oof co + —~ eS RO On aaa Mar Iesroe So at ve ob =" Sa. Fig. 193. Longitudinal section through the wood within the pend. We have spoken above of an internal injury to the axis even when carefully bent. This is best seen in a definite example as shown in Figs. 190-194 of an apple branch. The folding of the bark is indicated in Fig. 190 (rf) and Fig. 191 (rf). Upon examination with the naked eye, one sees first of all a swelling of the wood on the under side, below a pale, brownish zone, widened at the place of bending (Figs. 190 and 191, hp), in the longitudinal section (Fig. 190 h) 813 and in the cross section (Fig. 191 w). Except for the folding of the bark body no perceptible uniformly increased thickening is seen in the wood. In the apple branch here drawn the proportion of thickness between the bark on the under side and the upper side is 50 to 42, while that on the under side of the wood is 2 to 1. The pith (m) seems in the longitudinal section slightly brown in stripes, especially in the lower half. Under the microscope many of the cells of the pith and the pith crown, often arranged in wavy lines, are found to have a brownish content and browned walls which, in various cells belonging to the under side of the pith, are sharply bent here and there and at these places separated from one another by newly produced intercellular spaces (Fig. 194). The cells show the same separation even in the cross section. The disturbances to the bark may be recognized most easily in the projecting folds of the under side (Figs. 190 and 191, rf). In such folds, split off from the wood by the bending, the phloem bundles (Fig. 192, hb), as a rule, show a marked outward curving, corresponding to the peripheral cork layers (k) produced in considerable thickness by the squeezing of the epidermal cells and corresponding also to the bark parenchyma (7), which has been broken up by numerous holes (1) into irregular particles. Some time after bending some bridges of radially elongated cell rows are found in these holes, produced by the elon- gation of the still elastic cells of the Fis. 194. a pith cells which have been 4 broken apart in the bending; b those young, inner bark. which have remained uninjured. The apple branch in question was bent at the beginning of summer as is generally done in practice. The bark has been pushed up from the wood at the above described folds in the cam- bial region. The relief from bark pressure at these places has resulted in the formation of an abundant wood parenchyma, filled with starch, as shown in the longitudinal section through the wood (Fig. 193 Ap). After the holes have been filled in and the bark pressure re-established, the wood paren- chyma has gradually changed into normal wood (Fig. 193 hh’). The filling of the holes takes place here after the coalescence of both parenchyma parts growing toward one another and uniting in the medial zone (z). This yellow colored zone, under strong magnification, resolves itself into a stripe of closely compressed cells. In other cases, the filling of the holes is produced also by new parenchymatous structures from the raised bark zone as well as from the remaining young sapwood tissue (as in bark _ wounds). In all cases vessels first begin to appear in the wood parenchyma after the holes are filled out; they gradually reach their normal length and development, are accompanied at first by shorter, thinner-walled wood cells, later by normally long and thicker-walled ones, and thus the normal wood formation begins. 814 After these wounds are closed, the influence of the bending is still always noticeable in a production of wood which takes place more vigorously on the under side than on the upper side. The arrangement of the newly formed wood (Fig. 193 /) follows, on the under side, the wavy line caused by the cone of parenchyma wood (ip). In contrast to the scantier, simul- taneously produced elements of the upper side of the bent place, the prosen- chyma cells of the under side are at first shorter and arranged bluntly against one another, with broad walls. Further, more abundantly divided wood cells and rows of wood parenchyma (hf’), filled with starch, are found on the under side between the thick-walled parenchymatous elements. On account of the limited space considerable parts of the tissue have been omitted in the drawing; also part of the normal wood, formed before the bending, as well as a part of the transitional tissue produced after the formation of the wood parenchyma and equalizing the bending. In Fig. 193, fh indicates the spring wood of the current year, g the spiral elements bordering the pith (mk). In Fig. 194, a indicates the pith cells, which haye been loosened by the bending; b, those which have remained uninjured and originate from the upper half of the pith body. If the bent twig is investigated above and below the bend, it is found that in the present case the influence of the bending extends on an average over 6 to8 cm. The measurements of the branch, chosen for the drawings, are as follows: Its thickness amounted to 4.65 mm. beneath the bend, 5.50 mm. at the bend and 5.06 mm. above it. The bark showed toward the tip a considerable increase in thickness. The thickness of the wood, before the treatment, amounted to = upper side 62.0 per cent. ) Berea pian underside 61.9 —* of the wood cylinder existing | { upper side 50.6 i at the time of the measure- At the bend {under side 35.2 ment, and strengthened by | ) ts ean an | upper side 67.4 subsequent growth. under side 55-4...“ The increase in growth from the time of bending up to the time of investigation amounted to Autumn Wood Spring Wood : upper side 31.0 per cent. 8.0 per cent. Below the bend | under side 31.9 « ae « upper side 39.0 % 10.4 “al ee oie under side 51.8 * 13.4 e Above the bend | BDPEt sige Ke Se ie under side 27.2 21.9 Therefore, the increased wood growth is comparatively greater on the upper side of the bend than above and below the bent place in spite of the great tension which may prevail on the convex side within the bend due to 815 the bending of the branch’. The loosening of the tissue, manifested at the bend, can no longer be recognized on the upper side. On the other hand, on the under side it may be traced for 6 cm. toward the tip. The wood cells are the widest at the bend but are wider above it than below it; they seem to be wider on the under side of the branch than on the upper side. The anatomical changes vary in quantity according to the size of the curve, which the twig describes when bent, as well as the time of bending, the species and, indeed, the individuality of the branch. Therefore, one has in the bending of branches a simple means for mod- erating the growth im length and for directing the supply of water toward the buds which, because of their position and nature, are capable of little further development. THE TWISTING OF BRANCHES The effect of twisting the branches is much more pronounced and_ persistent than that of bending, but follows the same _ general principles. It represents a further cultural method for the fruit grower, when he wishes to change the growth of branches. During the period of growth, a too lux- Fig. 195. A branch bent with its tip downward uriantly growing branch is and twisted at the point of bending about its 5 longitudinal axis, after the coalescence of the first loosened in a short inner injuries. woody region by a half turn of the tissues about their long axis; hereby the tissue is usually crushed and split longitudinally and then bent at this broken place, with the tip of the branch downward, so that the tip is permanently bent toward the base. Thus at the place of twisting the under side of the branch lies on top; the former upper side forms the inner side of the sharp bend, in which the wood is broken down to the pith. The most comprehensive view possible of the changes produced by twisting is given in the longitudinal section through the knotty, deformed place of twisting, which is a year old (Fig. 195). In this figure, m indicates the pith which has been destroyed by the breaking of the wood when twisted ; 4 is the wood of the present upper side on which a bud is seen at a. Because of the turning of the under side to the present upper side, the wood 1 On the production of tension due to pressure, compare Ursprung, H., Beitrag zur Erklarung des exzentrischen Dickenwachstums an Krautpflanzen. Ber. 4d. Deutsch. Bot. Ges. 1906, Part 9, p. 499. Further: Biicher, H., Anatomische Veriin- derungen bei gewaltsamer Kriimmung und geotropischer Induktion. Jahrb. f. Wiss. Bot. 1906, Vol. 48, p. 271. 816 has been repeatedly split longitudinally, and the “lamellae” produced by the tears have a spiral twist which is indicated by dd. The tears are first filled by parenchyma and then the cambial zone, which gradually closes together, deposits wavy layers of new wood (mn) over the wounds below the unusually strained bark (7), which not infrequently splits here and there in spiral, longitudinal cracks, The original upper side, which has become the under side from twisting, shows still greater disturbances. The wood (h’), broken at w and partially split off from the pith, ends in a large knot (wv) due to very irregularly curved particles of wood parenchyma. This knot constantly increases in size with continued growth by the formation of new wood (7). It is easy to perceive that the nourishment of the tip of the branch must be disturbed by such an injury to the tissues and that the reserve substances, visible as starch in the parenchymatous overgrowth parts of the edges of the wound, must be enough for the use of the immediately adjacent buds. From what has already been said, it is evident, likewise, that besides this increase in nourishment the buds found directly beneath the place of twisting will also profit from the increased water pressure. The treatment of twisting, as already remarked, is an effective means of retarding the apical growth of a branch to the advantage of the basal buds witout, however, causing the uppermost lateral buds, lying below the injury, to sprout at once. The lateral bud immediately below the place of twisting, grows out to a new, vigorous leafy shoot only when the injury to the tissues in the twisting has been so great that the leader can no longer receive the amount of water most necessary to replace that lost by evaporation. It, therefore, dries quickly especially if the maniplation is carried out too early inthe year. This result is naturally not desired by the grower. A twisting, carried out too late in the year, would not produce an effect sufficient to prepare the basal buds for fruiting buds, but still would arrest the growth of the branch in length and cause a better ripening of the wood so that it will better withstand the winter. In the propagation of quinces by layering, the branch, which is to be layered, is twisted once about its long axis at the place where it is to form roots in the soil. This kind of disturbance is similar to that in the above- mentioned case; the result different inasmuch as the retarded, descending plastic material is used chiefly for the formation of adventitious roots. German grape growers in the vicinity of Tiflis are said to twist the stems of the ripe clusters and, thereby, obtain a better wine. The changes, initiated by this treatment, dovetail into one another as follows: the supply of water, from the vine to the cluster, is lessened by the twisting of the stem. Consequently, the evaporation greatly exceeds the supply and the juice of the berries becomes more concentrated. Whatever starch happens to be in the stem is carried as sugar to the berries. They break up and utilize, thereby, a part of the organic acids. The same processes occur in the ripening of cut grapes. —— Eo 817 THE EFFECT OF CONSTRICTING THE AXIS. The ‘“‘Constriction” consists in the close binding of an inelastic band (i. e. string, wire, etc.) about a trunk or branch. The results of this treat- ment show, to the casual observer, that this constriction of the axis is nothing but a local, artificial increase of the sap pressure. But here the most extreme case of sap pressure takes effect at once, since the formation of new structures below the constricting place are gradually reduced to a minimum and finally disappear entirely. The xylem elements, near the con- stricting band, thus deviate from their perpendicular course, even increasing their inclination to the horizontal, so that I think in the different normal trees themselves the more or less spiral twisting of the wood fibres is con- nected with the greater or lesser pressure exerted by the sap. Finally, the tree becomes so thick above the constricted place that the bark splits above the band and later also below it. This removes the sap pressure almost entirely. The result is a luxuriant formation of wood parenchyma which, with the aging of the plant part, passes over gradually in the later annual layers into normal wood and overgrows completely the band or the wire. Such an overgrown constriction bears great outward resemblance to a grafted place but has naturally no internal structural resem- blance to it. In Fig. 196 (see page 819) two different stages of the constriction are shown. Fig. 196, z is a year old maple branch, with a constricted place only a few months old. Fig. 196, 2 is an older branch, which shows the overgrowth of a wire ring, several years old. Fig. 196, 3 is a longitudinal section of Fig. 196, 2, where d and d’ represent the cross sections of the wire ring; u represents the overgrowth edge, which is more greatly developed on one side (u’) by the increased supply of nutritive substances from the branch (g) above it. Here it has overgrown the wire earlier than on the opposite side. An anatomical investigation of the stage represented in Fig. 196, 1 shows that the constriction at first cannot produce very extensive changes. The bark has suffered the greatest disadvantage and it is chiefly the cell layers, lying on the outer side of the primary bark, between the phloem fibres, or between the stone cell aggregations and the epidermal cells, which have been especially compressed. The cell layers next the phloem fibres seem to be the most pressed together; the effect is less marked on the next layers toward the outside, which are often thickened like collenchyma. Their cells are compressed to 1% or % their normal diameter and it would seem as if they hereby become somewhat longer than the corresponding cells in an unconstricted place. The sub-epidermal, almost square cells, are compressed to half their diameter. The epidermis suffers least of all. If, as in Fig. 196, 2, the constricting band is wound several times about the branch, apparently very prominent callus rolls become noticeable between every two turns. In them the aforesaid parts of the bark are devel- 818 oped in a way exactly the reverse of that at the constricted place. The cells, bounding the phloem fibres, which in the normal branch are elongated, become considerably broader radially; in fact, they appear like long cylinders, lying perpendicular to the phloem fibres; thereby, the overlying bark tissue, which participates less in the radial elongation, is pushed out- ward. Moreover, the rolls, lying between the two constricted places, are not absolutely large; they are relatively conspicuous only in contrast to the depressions. The secondary bark and the wood follow the convexities and concavities of the primary bark even if with far smaller variations. The pressure, which makes itself felt in the tissues, acts not only where the band lies on the bark but also somewhat above and below the actual place of constriction; this is seen especially in the cross section of the cells. The mutual proportion in the mean of measurements is: In the Bark Normal Roll Constricted Fig. 196, 1” Fig. 196, 1 w Fig. 196, 1 g 11,2 11,8 9,4 In the Wood 73 6,9 | 4,0 Therefore, according to these mean figures which, moreover, show con- siderable fluctuation, an increase manifests itself only in the round and apparently broader cortical cells ; the wood cells, on the contrary, seem some- what narrower than those of the normal wood but it should be emphasized that the same maximum diameter of the wood cells has been found in the roll as in the normal part of the branch at some distance from the constricted place and only the frequency of the occurrence gives the decision. If the constriction becomes older, without the band being broken or loosened, as was the case with the wire band shown in Fig. 196, 2 and 3, then the pressure of the wire on the layers of the bark finally increases because of the growth in thickness of the underlying wood in such a way that the bark layers are killed and changed into a brown crumbling mass. Finally, the healthy bark splits above and below the wire and inclosure of the wire begins. Because the overgrowing layers of the annual ring are considerably thicker in wood and bark than at places at some distance from the wire, the former constricted place finally projects in a considerable roll. Fig. 196, 4 shows the section, indicated in Fig. 196, 3 at a, considerably magnified. We see here in longitudinal section a little of the old wood of a- branch (H) before the wire (d) was bound about it and perceive the new structures of the overgrowth edge at first in the immediate vicinity (U) of the wire and then a continuation of these tissues from the older annual layer (U’). The transitional stages have been omitted for lack of space, likewise the representation of the coalescence, extending about U’, of the very uppermost overgrowth edge with the under one and the representation of the transition from the irregularly running wood elements of the overgrowth ———— a =e + SS SSS oO Poa Se SS _ Fig. 196. lis a constricted one year old branch; 2, a branch several years old which has overgrown the wire ring; 3, longitudinal section through Fig. 2; 4, anatomical sketch of a longitudinal section from a zone originating at a in Fig, 3, 820 edge to the normal wood structure, as it gradually forms in the later annual layers above the place where the wire is. If the wood had grown normally, without the arrestment of the wire, its structure would have necessarily remained the same as before it was constricted, as represented at AZ; wood cells (/) with vessels (g) would have been formed in regular succession and this broad wood would have been uniformly divided by radially extending medullary rays (m). Instead of this, we find the constricted place and above it (/',h) a kind of wood produced by the effect of the wire composed almost entirely of wood cells without vessels. Only in the beginning are these wood fibres deposited at h’ exactly parallel with the long axis of the branch; the more they are found in the direction (/’,h"’) the more diagonally they run and the more twisted they seem. The wood formed after the wire has been bound on has, there- fore, become denser, poorer in vessels and more twisted. The medullary rays, which otherwise run as straight radial bands from the pith toward the lark, are as twisted and outspread toward the top as the wood cells, so that a section made exactly in the direction of the radius intersects several of the curved rays (m’). The difference between the wood cells and medullary ray cells is not noticed until at some distance from the wire. In the immediate vicinity of this we find an almost uniform parenchymatous wood (hp), of which the edge is dead and black and represents the dark line which may be seen in Fig. 196, 3, extending upward a little distance from the wire (d’). The black furrow no longer extends entirely to the outside, since the later annual layers (Fig. 196, 3,u’) have already united with one another. These overgrowth edges, united with one another to form a common, connected wood layer, are indicated in Fig. 196, 4, by the tissue H.’ Here we find the ducts (g’) and the wood cells (nh’) formed as in normal wood (only shorter) but their course is horizontal instead of vertical in the plane lying at the same height as the wire. Only at some distance from the actual place of constriction upward or downward do these elements begin to pass over gradually into their normal perpendicular course (Fig. 196, 4 gh’). The browned, or blackened, zone (Ap) is not continued to U’. The term “browned” or “blackened” has not been chosen without good reason, for the color from ¢ to ?¢ is as black as ink, from there toward ?#” a brownish black. In fact, it is ink which colors the clotted cell contents near the wire. The tannic acid of the tissue has combined with the iron of the wire and, therefore, killed the cell contents in the immediate vicinity. This compound is diffused for considerable distances and, in fact, farther into the old wood through the medullary ray tissue than transversely through the wood cells. The fact that the wire lies directly against the old wood and has killed a zone of it should not be surprising, when we think that the constantly increasing pressure of the distending branch against the inflexible wire, leads to the compression of the soft bark and the cambium 821 and kills them. The dead tissue can be recognized only in small fragments along the wire. We have already explained above how these different tissue forms are produced by the sap pressure, at first greatly increased and then nearly removed by the splitting of the bark around the wire. The almost complete breaking up of the split bark makes possible the appearance of wood paren- chyma from the cambial zone; later, if sap pressure begins because of the uniting of the wound edges over the wire, thus enclosing it, true wood cells and vessels again appear but the arrangement of these elements for some time is horizontal, or spiral, diagonally ascending, caused by the strong pressure of the wire at the time when the cambial zone still lay back of it. The extreme twisting of the wood fibres, which can be confirmed also, to a slighter extent normally, in a great many trees, and manifests itself in different degrees in individuals of the same species, is physiologically inter- esting. The twisted growth is more noticeable in dry places. The greater twisting of the wood fibres, probably caused by the bark of specimens grown in dry places which becomes inelastic sooner, is less easily split and, there- fore, exercises a higher pressure. The practical purpose of constriction is the same as that of girdling but without the danger entailed by a complete removal of considerable parts of the bark. BRANCH CUTTINGS. The term cutting is applied to any part cut from the parent plant, which by its reserve food materials incites various cell groups, chiefly those near the cut surface, to renewed vegetative increase so that a cicatrization tissue is formed. The separated part by forming new roots develops into an inde- pendent plant. A work by Simon? throws light on the anatomical conditions and the dependence of tissue differention on external factors, which appear during the pressure and can not longer be taken into consideration. It may be asserted that an asexual propagation of this kind may be found in all classes of the vegetable kingdom and may take place from very different organs. We recall here the continued growth of torn off mycelial threads, of cut sclerotia, of isolated fruiting stems of the frondiferous mosses and of leaf and blossom parts of phanerogams. Beside the fre- quently occurring root cuttings, cases have also been known of the formation of roots from fruits. We are concerned here for the present with cuttings from branches, the cut surfaces of which react to the wound stimulus by the formation of callus. In connection with this, we will then discuss propagation by root cuttings, the cicatrization of which also begins with the formation of callus. The transformation of the callus into an actual overgrowth edge by the formation of a peripheral cork zone bears very great resemblance to the formation of the overgrowth edges on girdled, or transversely cut, woody 1 Simon, S., Experimentelle Untersuchungen tiber die Differenzierungsvorgiinge im Callusgewebe von Holzgewiachsen. Leipzig 1908, Gebr. Borntrager. 822 branches. But in cuttings the moist medium, in which the cut surface is placed, acts as a modifier. A difference should also be determined accord- ing to whether the branch furnishing the cutting was already in a woody condition, or was still herbaceous. Instead of extensive analyses, we will give here illustrations of an herbaceous Fuchsia cutting and a woody rose cutting. ‘The basal part of the Fuchsia cutting (Fig. 197) is shown in longi- tudinal section ; s to s indicates the original cut surface; the elements appear- ing below this line were formed after the cutting was made; above it (s to s) lie the original tissues, only one-half of which have been shown. m is the IN Seo LS reo ff LY, “2 Fig. 197. Fuchsia cutting. pith ; h, the wood, r, the bark, in which extend the phloem fibres (b). These as well as a part of the wood cells (h’) have browned on the cut surface and died. The outer bark (r’) also has dried up in the region of the cut surface. The younger, inner bark layers, on the contrary, and especially the pith, have healed over the wound surface by an abundant cell increase. The outer part of this cicatrization tissue is turned to cork and this cork layer (k) has grown to a considerable size through the activity of the cork cam-- bium (ke), which forms the protection for the more tender, inner bark tissue. In the callus bark we find the broadened pouch cells (0), with calcium oxalate in raphides. Near these are isolated cell groups, with thicker walls (b’), which represent the phloem of the vascular bundles 823 already formed in the callus, their wood being suggested by strands of short, reticulated vessels (g”). These adjoin the vessels in the wood of the cut- ting, the thin-walled wood cells of which, rich in starch and bounding the pith, have participated in the formation of callus. The old wood of the cutting was torn when cut. The torn place (d) is filled with callus and the cambial zone (c to c) may be traced even into this torn place; it passes through the callus in a connected curve. The normal cambium of the cut- ting lay on the outer side of the wood (h). By cutting off the branch in making the cutting exactly the same change has taken place as in the ringed HE rT AP i ra ee B TET ian gHT ititn i i We my RE fe Be WY eS ERENT ay LOY ee; Ses Ma 05ees ee = recess ioge ean e=== Th SORA ZION See a PORTO OS DSO I TR ey” ™. =sZece eC ES feet a Fig. 198. Rose cutting. branch. At first uniform parenchymatous tissue was formed from the cambium, in which short, reticulated vessels (g) gradually appear. Toward the cut surface these tissue parts have become bounded by a heavy cork layer (k’), but in the outermost bark cells increase has also taken place and in the new tissue a formation of short vascular cells (g’) on the outer side of which is recognizable a meristematic layer (c’). In the present example the pith, as well as the cambium, has been the chief centre of callus formation. On the other hand, the pith has remained quite inactive in the case of the rose cutting (Fig. 198). 824 Here too s to s indicates the line of the cut; all below this is callus formation, which has pushed out the thick rolls from the original cambium and spread over the cut surface from its outer edge inward. In the longi- tudinal section shown in the figure, we distinguish a roll (ca’) cut through radially and a callus (ca?), projecting outward from the back edge and then cut across, the bark of which has already united with the laterally incurving ca’. Thus, in this older rose cutting at any rate the pith is covered but this takes place by the union of edges, curving in from the periphery toward the centre, while in the Fuchsia cutting illustrated above the main mass of callus is formed by the pith itself. The indication of the various elements agrees in general with that of the preceding drawing. m is the pith, which was here torn when cut. The cut (w’) has been filled with callus projecting out from the back edge; h is the old wood, formed before the branch was cut off; nh, the new wood formed during the period of propagation, exactly corresponding in character to the new wood of the callus in the grapevine. This begins with short, wide, porous, thick-walled cell masses, rich in starch, in which occur like- wise short reticulated vessels. Their elements become narrower and nar- rower toward the outside and more elongated, more and more resembling the normal ones the later they are formed after the cut is made, 1. e. the closer they lie to the cambial zone cc. This cambial zone extends around the cut surface of the old wood in broad curves and is covered on the outside by the newly formed bark (ur) which is not completely reproduced in the drawing. We notice on the outermost edge of the bark the corked and _ dying first stages of callus (a), extending at first over the cut surface and formed of broad, spherical to pear-shaped cells, arranged in rows, the end cells of which are rounded. These cell rows are increased at first at the ends, since the outermost cells have enlarged and been divided by cross walls, and the small end cells thus reduced in size repeat the process when growing further. In the callus roll (ca), which extends from the back outward, and has been cut transversely, g indicates the short reticulated vessels, which repre- sent the beginnings of the new wood. Around this extends the cambial zone (c’). bis the old phloem strand, formed before the cutting was made. It has been pressed far away from the old wood at the cut surface by the abnormal new wood formation, and has died at its free end. The cells lying against both sides of the phloem fibre groups have been released from the sap pressure by the cut and have stretched transversely (7’), while in a normal condition they would be elongated. The remaining outer part of the old bark (r) has not changed and has closed the wound with cork. o indicates the rhomboid, isolated crystals and stellate druses of calcium oxalate. The new roots grow sometimes from the callus itself, sometimes from the basal regions of the cutting above the callus, according to the plant species. 825 THE UTILIZATION OF THE VARIOUS AXIAL ORGANS FOR CUTTINGS. Callus formation itself as we see is, therefore, the simple process of healing a transverse wound. The formation of the cicatrization tissue at the base of the cutting is aided by especially favorable conditions. Except in healing the upper edge of the wound, the reserve substances in the cutting momentarily find no other use than in the cicatrization of the lower wound surface, since the usually shady place of propagation does not favor the bursting of the buds. Where the growing conditions given the cuttings through ignorance cause a rapid development of the buds, the formation of callus and roots is reduced or fails entirely. In the second place, the moist place of growth and the usually increased temperature of the soil act in such a way that cell increase is favored on the lower cut surface, i. e. the cicatrization tissue assumes a very luxuriant character. The formation of callus is not absolutely necessary for the cutting. Plants, which very easily produce adventitious buds, reduce their callus tissues to very small amounts. They cover their cut surface by a formation of cork and utilize their reserve substances at once for the formation and further development of new root primordia. Here an abundant cell increase occurs only in the cambial zone, lying immediately in the cut surface, whereby the base of the cutting enlarges considerably (Begonia). The formation of callus can become very injurious in trees which form adventitious roots with difficulty, since by its especially abundant development it consumes the material provided for the formation of new roots. We find, at times, enormous knotty callus swell- ings without any formation of roots (conifers). The kind and age of the cutting and the vegetative conditions given it determine which tissue shall participate in the callus formation. The cambium always takes part in this. Where it, does not assume exclusively the process of healing, it is assisted by the parenchyma of the inner bark, or also by a part of all of the parenchyma of the pith. Further, even the parenchyma of the wood and that of the older bark can participate in this. In herbaceous, rapidly growing plants, even in their thick-walled elements, a cell increase occurs near the cut surface because of the formation of tyloses in the vessels and of a new formation of cross walls in the collen- chyma of the older bark. It has been observed here + that the thickened walls of the collenchyma cells and the vessels in the immediate proximity of the tyloses swell up, become porous, and are, in part, re-absorbed. The more living parenchyma therein present, the more rapid and abundant is the callus formation. The cuttings are generally made at a node directly beneath a bud. In a cross section through a bud-cushion it is found that the parenchyma mass is greatly developed here by the passing over of the medullary connections into the bud. At the node the pith 1H. Criiger on Trinidad; Westindische Fragmente, XII. Einiges tiber die Gewebesverinderungen bei der Fortpflanzung durch Stecklinge bei Portulaca oler- acaea. Bot. Zeit. 1860, p. 371. 826 parenchyma, as a whole, is usually living and capable of dividing, while it has died in the remaining part of the branch and is partially torn. It should be remarked, however, that no constant rules may be given for the kind of callus formation. Often, especially in herbaceous plants, the cuttings form only very little if any callus on the wound surface, swell- ing out and being cut off by cork, but in another case the plants furnish considerable masses of callus. The perfectly herbaceous summer cuttings of Vitis, especially the American varieties, usually develop but little callus ; sometimes, however, great masses of it. The same is true for rose cuttings, if they are cut in the early spring in a vegetative soft condition, from forced plants and stuck in a warm sand bed. A large supply of food and its slow utilization awaken a tendency to callus excrescence. A work by J. Hanstein’, provided with a detailed: bibliography, takes up girdled cuttings. He found that such cuttings, with isolated wood and bark, which had been girdled near the base, developed roots above the girdled surface and not on the under cut surface. If cuttings, which had already formed roots, were girdled, the further development of these roots ceased and a new formation began directly above the girdled surface. An excep- tion to this rule is found in all those plants in which fully developed vascular bundles are found or, at least, a fully developed, sieve tube system in the pith. In them despite the girdling roots are found on the under cut surface of the cutting. When stating these results, we need only add that the oper- ation must be carried out with ripe, or nearly ripened axes in order to obtain these results. If very young herbaceous tips of woody plants are used, in which also the girdling can be done cleanly only with difficulty, the new root system is produced on the cut surface, or in its immediate vicinity. In this all the tissues with the exception of the old prosenchyma elements participate in the callus formation. The part above the girdled surface then frequently dries up. The same phenomengn may be observed if cuttings are placed upside down in the earth. Only infrequently do such cuttings grow further. After they have formed callus and even roots on the end standing in the soil, which is organically the upper end, they usually die back from above down- ward to a small basal part and then develop new shoots from this. The results are of practical importance inasmuch as they clearly illus- trate the transference of the plastic material, necessary for all new structure formation. We see that the main paths for the building materials should be sought in the sieve tube system in the bark. If such paths exist also in the pith, a transference of the plastic substance likewise takes place there. Besides these main paths there are also in cases of necessity side paths, which become of importance. The parenchyma cells of the bark and pith will also conduct the plastic materials upward and downward and likewise, as we see in the new formation of bark on bark wounds, the medullary ray cells in the axis can radially transport dissolved, reserve substances; but the quantity e 1 Hanstein, Johannes, Uber die Leitung des Saftes durch die Rinde Pring- sheiin’s Jahrbiicher fiir wissensch. Botanik, Vol. II, 1860, p. 392-467. 827 transported in this way is small and, therefore, insufficient for any new structures worth mentioning. The plastic substances are carried much more poorly organically upward, i. e. toward the tip, than organically downward. As we see from cuttings set upsidedown and can perceive also from intentionally reversed grafts, under favorable conditions a transference of all fluid materials in the plants, the raw soil solutions as well as the plastic, organized constructive substances, is possible in all directions. The most easily passable paths are naturally used first; when any hindrance occurs there the side paths become of increased importance. In cuttings callus can be formed on every wounded place and this callus can produce axes con- taining chlorophyll and roots. Whether such a case will actually occur depends on external conditions and the typical developmental law peculiar to each plant, changed only with difficulty. Many plants form adventitious roots from the internode so rapidly that the callus formation on the cut surface has not sufficient time to make any development worth mentioning. Contradictions in the results of the various observers are explained by the diversity of the external influences. Thus Stoll’ states that no callus became visible with Pogostemon Patchoult, while Hansen? observed it. The former found no new vegetative points were developed from the callus tissue, while the latter could prove them, etc. In practice it is advisable in propagating bushes not to make cuttings from ripened, old wood but from succulent shoots, which when possible are taken from plants forced in the winter in greenhouses. Under certain con- ditions it is advisable to make cuttings also from plants, which as a rule are propagated from seeds. It is a well known fact that cucumber and melon plants from seed of the previous year make very luxuriant foliage growth but set fruit less abundantly. Old seed with contents poor in water, how- ever, like wilted seed potatoes and the like, behaves more favorably since the vegetative activity of the plant appears to be modified. Cuttings from the tips of vigorous shoots of cucumber and melon plants, forced in the hot bed and bearing the first fruit possibly in May, give within a few days and about this time well rooted plants with greater fertility than plants from seed. Here, at the end of the chapter, it is necessary to call attention to the fact, that propagation by cuttings is often used for the development of new varieties. Many teratological and pathological conditions, which appear temporary in different parts of the plant, become fixed in the cutting. A great many plants with highly variegated foliage, varieties with double blossoms, etc., which originally appeared on isolated shoots, have been made permanent by cuttings. Temporary juvenile stages in Conifers varying with the place of growth are propagated further by cuttings and offered for sale as new forms or varieties. A few striking examples of this kind form 1 Uber die Bildung des Callus bei Stecklingen. Bot. Zeit. 1874, Nos. 46 and 47. 2 Hansen, Ad., Uber Adventivbildungen, Sitzungsber, d. phys.-med. Sozietit zu Erlangen June 14, 1880. 828 valuable suggestions for further experiments along this line. According to Beissnert in order to obtain Chamaecyparis squarrosa from cuttings of Biota orientalis only the small branch axes with decussate leaves should be used, which are found close above the cotyledons. The majority of these little branches always give Biota meldensis, but with an evident scale-like position of the leaves, Biota orientalis. Likewise, cuttings of the first shoots of Callitris quadrivalvis give a new form. The fixed juvenile stage of Cupressus sempervirens may be seen in C. Bregeon; the first shoots of C. Lawsoni give a form with squarrous leaves. Retinospora ericoides,, Zucc. was obtained from Chamaecyparis sphaeroidea var. Andalyensis. The diversity of plants obtained from the ivy according to whether the cutting is taken from blind or blossoming wood is well known. Aside from the often simpler leaf form of blossoming wood, which is easily transmitted to plants from cuttings, we often find their habit of growth to be more dwarfy and bushy. The subject of the retention of juvenile forms has recently been treated thoroughly by Diels’. Propagation by root cuttings is still but little used, although very advan- tageously in many woody plants. Paulownia, Ailanthus, Syringa, Aralia, Mespilus, Rosa, Malus may be propagated by removing larger root branches before the first growth in the spring, or before the second growth in July. These are cut into pieces possibly 5 cm. long and laid flat in rows in the soil: New plants rapidly becoming independent by their own root formation are produced at different places in the piece of root by adventitious bud forma- tion. Among the conifers, Araucaria, Podocarpus and Gingko are said to be advantageously propagated by root cuttings especially if these are set in a warm bed. Large root stocks survive splitting lengthwise; each half then develops adventitious buds. Some plants may also be propagated by bud cuttings (Vitis, Paeomia arborea). The buds are cut from the old wood in the spring just as if one were cutting long buds with some wood for grafting and these bud cuttings are laid flat on the surface of the soil in pots. It is advisable, however, to excite rapid growth by warming the soil. We can also speak of tuber cuttings, since there exists a method of propagating plants by boring the eyes out of the fleshy tubers with a part of the tuber tissue containing reserve substances (potatoes, caladiums). Usually the part of the tuber, which has been cut out, forms cork on its exposed wound surface at the expense of the starch and retains the remain- ing reserve substances for the first nutrition of the eyes, which become independent quickly by the development of adventitious roots. The cutting of seed potatoes should be discussed in this connection. In practice the precaution is observed, as a rule, of not placing the pieces of tubers in the soil immediately after cutting. This precaution is perfectly justified, since, 1 Beissner, Uber Formverinderung von Koniferensémlingen. Regel’s Garten- flora 1879, p. 172, cit. Bot. Jahresber. 1879, II, p. 2. 2 Diels, L., Jugendformen und Bliitenreife im Pflanzenreich. Berlin 1906, Gebr. Borntrager. 829 in planting freshly cut pieces, a decay easily occurs among them as soon as even a little moisture is present in heavy soils. If on the contrary the cut pieces are left a few days in the air, cork layers are formed under the cut surface, which protect the pieces of tuber. If the tubers are cut too early before sprouting, it may happen in some varieties that the pieces remain for some time in the soil apparently unchanged without any sprouting of the eyes. It is, therefore, advisable with tender varieties to spread the tubers before planting in a light, warm place until the eyes begin to enlarge and then to undertake the cutting. The importance of the cork formation on the cut surface is shown by an experiment made by Appel’, who supplemented the results of studies by Kny? and Olufsen*. While the two last named investigators perceived the tuber’s chief protection against infection by parasites to be the wound periderm forming beneath the cut surface after a short time, Appel proves that the potato is able to protect itself before the wound cork is produced. He finds that in the most favorable cases the periderm formation sets in only on the third day after the injury and ends after two days more. There- fore, the wounded place would lie unprotected for that length of time against the demonstrably rapidly penetrating bacteria of decay if the walls of the undestroyed cells lying directly beneath the wound surface did not turn to cork immediately on the side toward that surface. In fact, this cork deposition completed after twelve hours was found in a part of the cell wall of the first and second cell layers beneath the wound surface to be entirely sufficient to prevent infection from Bacillus phytophthorus. The process of suberization develops less well if the pieces of tuber dry at once and are kept warm (for example, within doors). The outermost cell layers of the cut surface then dry up so quickly that the two factors necessary for the turning to cork, viz: oxygen and moisture, have only insufficient access to the tissue layers under consideration. The closing of wounds in all fleshy parts of plants takes place in the same, or a similar manner. GRAFTING. Improving the stock by grafting consists in the artificial removal of one or more buds and their insertion in a living part of a plant for the sake of further nutrition and development. The inserted parts are usually held fast by a bandage and protected by grafting wax from the injurious effects of the atmospheric conditions. The inserted part can in general be called the “scion,” while the nourishing trunk is called the “stock.” The newly produced tissue furnished in part by the stock and in part by the scion, 1 Appel, Otto, Zur Kenntnis des Wundverschlusses bei den Kartoffeln. Ber. d. Deutsch. Bot. Ges. 1906, p. 118. 2 Kny, L., Uther die Bildung des Wundperiderms am Knollen in ihrer Abhin- gigkeit von 4usseren Hinfitissen. Ber. d. Deutsch. Bot. Ges. 1899, p. 154, 38 Olufsen, Untersuchungen tiber Wundperidermbildung an Kartoffelknollen. Bot. Centralbl. Supplement, Vol. XV, 1903, p. 269. 4 Kiister, Ernst, Pathologische Pflanzenanatomie. Jena 1903, G. Fisher, p. 185 ff, 830 which unites the two artifically connected members, is called the “connecting layer,’ or, according to Géppert, “intermediary tissue.” The scion is either a single bud, which has been separated, together with a part of the adjacent bark, or a piece of a twig with several buds. According to the cultural purpose the scion can be inserted at the place of its removal, or at some other place in the same individual or (most frequently) on some other indi- vidual. In the first phase, only the effect of the injury; in the latter, in addition the influence of the difference in character of the scion and the stock will have to be considered. This process of improving the “stock” will have to be considered first of all as a process of wound healing; the favoring, or arresting influence, will have to be taken into account secondarily, due possibly to the mutual interaction of the two artificially connected plant parts. Among the authors treating this subject thoroughly, Goppert? should be named first of all. He took up the subject especially through anatomical studies. A year after the publication of Goppert’s well illustrated work I published a supplementary article, in part confirming it and in part correct- ing it?. Among the earlier physiologists, the statements of Hanstein*, of de Candolle*, of Treviranus> are especially worthy of consideration. Thouin® made a systematic compilation of all the possible variations in the process of grafting. He based his work on Duhamel’, La Quintinye’®, Rozier®, Cabanist® and the other horticultural writers and by means of abundant bibliographical citations facilitated tremendously the study of the history of the art of grafting. Of the various forms of grafting which Thouin describes in his book under separate names and usually illustrated, only a very few have found a general acceptance. All the forms in use at present will from a pathological point of view be best arranged in their respective values, according to the degrees of injury which the stock suffers and according to the greater or lesser degree of ease with which the wounds can be healed. Under other- wise similar circumstances, the success of the manipulation will be the more certain the more rapidly the tissue of the scion forms a firm connection with the stock and, since this connection is brought about by means of the newly produced cicatrization tissue of the wound, the rapidity with which the wound is closed becomes the standard, chiefly, if not exclusively, for judging the value of the form of grafting. 1 Goéppert, tiber innere Vorgiinge bei dem Veredeln der Baume und Striucher. Kassel 1874. 2 Sorauer, Vorliufige Notiz iiber Veredlung. Bot. Zeit. 1875, p. 201. 3 Hanstein, Dr. J., Das Reproduktionsvermégen der Pflanzen in Bezug auf ihre Vermehrung und Veredlung. Wiegandt’s Volks-und Gartenkalendar 1865, 4 De Candolle, Physiologie végétale II. 5 Treviranus, Physiologie der Gewiachse 1838, 11, p. 647. 6 Thouin, Monographie des Pfropfens. Berg’s translation, 1824, 7 Duhamel, Physique des arbres 1758, II, p. 75. 8 De la Quintinye, Le parfait jardinier. Paris 1695. 9 Rozier, Cours complet d’Agriculture, Vol. V, p. 346. © Cabanis, Principes de la Greffe, p. 105. 831 The phenomena of union possible in grafting may be traced to the healing processes of three classes of wounds which I have called bark wounds, surface wounds and cleft wounds. The injuries termed bark wounds (as evident from the earlier chapters ) are those produced by a complete removal of the bark, so that the wood is exposed without, however, losing any of its parts. The form of grafting in which this peeling process forms the main part of the injury belongs to the type of budding. Here, at the time of the greatest cambial activity, the bark is raised for a certain distance from the wood of the stock and the scion (bud) is inserted into the exposed place. This scion consists of a single eye with a small bark shield (budding with bark), or of an eye which has been cut out with some wood from the parent branch (budding with wood) or of a piece of an entire twig which can be inserted in different ways and is shoved under the bark of the stock with its cut surface against the wood cylinder (bark grafting). Under the term “surface wound” are included all the injuries in which a piece of the wood is taken away together with a complete removal of a part of the bark. The surface wound looks and behaves differently, accord- ing to whether this wound surface is produced by a longitudinal or a cross- cut. If the piece is cut from the axis longitudinally, the elements of the bark and wood are exposed lengthwise. The rain water runs off easily from this surface wound, while in a cut across the trunk it collects in little troughs and can much more easily cause the decay of the wood. A hori- zontal surface wound is always much more dangerous for the axis than one running vertically. On this account in general practice diagonal cuts are usually made, instead of horizontal ones. The kinds of grafting, in which surface wounds come into play chiefly, or exclusively, belong to the type of “Copulation.” The simplest form of this consists in the setting of a scion in a diagonally cut surface, produced by the cutting off of the tip from the stock where it is of the same thickness as the scion. Most nearly related to this is the single and double saddle graft. The scion and stock can be united also by actual longitudinal surface wounds, if the stock is cut at the side in only one place without loosening its tip. The scion either remains attached to the parent plant and, likewise, is cut only at the side (ablactation), or cut off from the branch, as in other forms of grafting, it is fitted to the stock by lateral paring. In order that the scion may fit more closely in a lateral position, its lower end is cut to a wedge and this end is forced into a cleft at the base of the surface wound of the stock. In many plants (Camelias) the scion is not infrequently cut to a short wedge and this wedge is forced into a lateral cleft in the stock, produced by a short diagonal downward cut into the wood (insertion). When the grafting fails, stock thus cut suffers least of all and after a short time can be used again. The injury from which the trunk suffers most is the cleft wound. The form of grafting with such wounds is cleft grafting. This was at first used ses. STS oe a ORS EA age ok SCS eaateN ENR Boop AOA ees We ce Neel ciSeccae AMI neta Suet lh ied eae Sar miceesa" ESS IOS pas I Sah mortal L M Wor@o PEARS A MWe SOG esos Nag ee stot MESS, 500 ABB a 5 ty 200! TARE Siases. ve cy Woes OF *\ Rosa (\ SaOoni] as 0) KO ee? 5 ELA Sar i WTR RA tex eeaeel CRO th Bi SA ieegelineoege Eo PE, EERO HT las EL Ae x Were: Obes ee OY, VOLSCGY, POOL PST (HUH HS )} mp csdes Wedorsceer HAA eo eey aor ab, SOG @ Close et eco meeeae ne WOR Tr LONER se NNneaescze NO oadleeeee, SojnocrpeOgce) Ab Aso weaeeee: sagaaiNg HI, “RAL ZI BNeeSg NOG SEclowgss Noses chee tynreu acl, OY OECeN AOU Os ee AN AAT HYG aN \cnd tas SE aE pees Seog eae AN Netconnll yp) CE NOES Wesgre\ Seeellootsalas: [ear] Bes WCOS Re fees Set ol) Swope) Soe see | Saesag CNCOGE: Baradapeyscs LQTS Nay Oregon IZ IOSA en iy UK A 4 | COOcdii5: Canna! (ES (TILNIAY 083 GOs CO Fo CZ Sees Ox as ’ Ki) ) Roe ee Neco pecenes Ye) IA aur Ar VS Boies NS ecscen Gee RW OSerce OSSIOE SEO EEK x) SAO ar®) rae ONS Cleo els HET bryo) VSR AK Soseerseata\ as Jee Sh LSS NO ORO eOGES NOOB AN 0. eilSaesio/joe Por oly cB, OY ZAERO eee SK Ss 2 ee koG OS COS Shot 2 OLCogfoo AKA (MOOK Roce oN Se x pipe Za a hh WSN 70 SY, oe Ne O Fig. 199. A budded rose. 833 generally in Germany but now only for isolated, special cases to rejuvenate older trunks. Cleft grafting consists of pushing a scion, cut wedge shaped on two sides, into a cleft in the stock which has been cut off square. This cleft is produced by splitting or by cutting out a wedge from the wood. In considering the processes of healing, i. e. processes of union in the different forms of grafting, we must distinguish first of all whether this has been carried out on soft wood, or on branches of mature, strong wood. In the first case more tissues participate in the formation of the “layer of union” than in the latter case in which.a mass of tissue is chiefly involved, formed from the cambial zone (at times also from the pith zone). This tissue forces itself into the space between the scion and the stock, or figur- atively speaking must pour in between the two adjacent parts. OcULATION OR BUDDING. The most interesting processes of union are found in oculation. In the plate here given, a budded rose is pictured. In one-half of this drawing (from 7 to 2), the tissue structures are shown after six days; in the other half (from 2 to 3) after about four weeks. The section through the place of budding clearly shows the inserted bud at F, the stock at w. In the stock, hh is the old wood of the previous year, sh, the wood of the current year, formed at the time of oculation. L are the bark strips, raised by the T-cut ; in them, b should indicate the phloem fibres, ¢ the dead tissue of the cut edge. At the time the bark strips were spread out from one another by the inpushing of the bud (£), the cambium was very active. The raising of the bark takes place here in the sapwood in such a way that the youngest vascular primordia (g) and the cambial layers (c) lying in front of them remained attached to the bark strips. Often only the bark is raised. In fact, under some conditions, pieces of the entire cambial region with the youngest bark cells remain attached to the wood. No evidence of any fixed law has been recognized in this con- nection. It seems that the momentarily tenderest part is torn when the bark is raised and that individual homologous tissues can behave differently at the same time in the same varieties; in fact, that even the bark on the different sides of the trunk has a different loosening quality. Therefore, the processes of healing are unlike in the same species and variety even in the same grafted individual at different heights. Even after 12 hours a change in the peripheral cell layers may be recog- nized on the edges of the wound in the bark as well as in the wood; the walls of these cells have thickened and turned yellow, either on the exposed side alone, or on all sides of the cell; the cell contents have increased. It cannot be determined whether this has taken place only because of swelling, as in the wall, or by the transference of material from the inner part of the 834 wood toward the periphery. The first developmental stages differ according to the life activity of the exposed cells. As a rule, all places on the exposed wood are not covered with sapwood capable of increase. If the tissue of the sapwood does not begin to increase, the cell walls on the edges of the wound swell and turn brown, together with their contents ; they also collapse somewhat and form an irregular thick yellow stripe. The walls in the cell groups, which are adjusting themselves for increase, usually turn brown only slightly and frequently after a short time begin to form wound callus. The thin-walled tissue, gradually growing out in parallel rows (ok), is the wound tissue, the growth conditions of which were described under wounds due to barking. In Fraxinus, for example, this could be observed to be 16 cells thick after two days. The arrangement of the callus is comparatively rarely as regular as it is shown in the drawing. Because some parts of the wood do not form wound callus, the adjacent cell rows radiate from one another and cover over the places remaining inactive. This callus forma- tion is so rapid that the covering of the inactive places and the close union of the elements coming from the different sides is a matter of course. The bark strips on an average proceed less rapidly to the formation of wound callus. The products of the new formation are also different. To be sure, the peripheral cells, rich in cyptoplasm, project somewhat (#) soon after the operation, but cell increase does not always occur or, in case it does begin, its product is only cork which can protect the wound surface. The formation of new structures is more energetic and increases until an abundant wound callus tissue is formed usually first toward the inner angle, where the bark strip is firmly attached to the wood (ok). The rapidly formed wound callus masses of the bark and wood, as well as ultimately those of the scion, unite and in the shortest possible time form a temporary protection for the graft wound. We say “‘a temporary protec- tion” for, actually, the tissue as yet reproduced is only short-lived. As soon as the the callus tissue has acquired a considerable extent and seems exposed to increasing pressure, a meristem zone is formed in it at a certain distance from the periphery, which at times is strengthened by cork cells. The maturing of this meristem zone depends upon the distance between the stock and scion. At times, at a very short distance, only a few lateral, isolated aggregations may be recognized but when the intermediate space is great and the wound callus formation luxuriant, continuous zones may be discov- ered, which often after having a looped course are connected with the sharply protruding cambial zone of the older overgrowth tissue formed on the bark strips (cc,cc). The meristem zone is not drawn in the young wood callus because it does not appear until later. In common with the cambial zone of the bark strips (cc), this callus meristem furnishes first of all the actual connecting tissue consisting of 835 wood parenchyma in the form of thick-walled, isodiametric cells, or cells somewhat stretched radially, irregularly quadrangular, which appear not infrequently with somewhat bent walls (kg). These represent the begin- nings of a wood body, which is being formed under slight pressure. By their increase they gradually compress all the thin-walled, first-formed tissue, retaining the character of phloem parenchyma (ok) and representing the first closing of the wound. When the meristematic zone is formed in loops, round masses of wood parenchyma are produced, enclosing the brown dead cell complexes of the original tissue. Gradually the whole tissue (ok) is pressed back between 1 and 2 by cells similar in character to those marked (kg), which store up starch. Under favorable conditions, the scion also participates in closing the wound. In the present drawing, a bud is shown with the bark shield, but without any wood. The cut & is a cross section only through the bark shield. The bud belonging to this, which must be imagined in the direction (0), lies above the plane of the section; in this section only the large central, vascular bundle (gb), which extends to the bud, and a smaller one adjacent to it have been drawn. The third, smaller bundle, present in every unin- jured bud cushion and likewise traversing slantingly the axis of the branch on the other side of the central bundle, has been cut away here in removing the bark shield; this does not affect the outgrowth of the bud. On the other hand, the absence of the central vascular bundle will always signify a failure in budding. The bark shield with the rapidly drying bud bracts can grow further without the vascular body but in my experience it has never happened that an excessively luxuriant overgrowth tissue from the bud had formed adventitious buds and in this way compensated for the dead bud. To be sure, the formation of adventitious buds takes place in many bud grafts, as is shown in the following Fig. 200 of an herbaceous bark graft of Aesculus rubicunda on Aesculus Hippocastanum, but up to the present I have found this bud formation only on luxuriant overgrowth edges of the stock. The bark strips (ne) have produced such strong new structures that they have thereby been pushed out from the scion like wings. Numerous adventitious buds (a) stand on the edge. In the budded rose (Fig. 199), the whole inner surface of the bark shield (E) has already produced new wound tissue, sometimes more, some- times less, according to the age of the mother cells. The cambial zone of the bundle, lying below the phloem fibre groups (b), has formed the new cells very abundantly, as is shown by the protruding tip (¢). The new structure on the inner side of the shield bears the character of bark tissue and is already distinguished by numerous crystals of calcium oxalate, while the cambial zone (c), which begins to form new wood elements, appears in later stages of the coalescence in connection with the cambial zone (cc) of the bark strips. As soon as this union takes place a continuous cambial ring is formed again about the whole circumference of the tree. The cambial 836 zone of the bud represents an integral part of this. The zone (cc), if traced backward, is found to be a direct prolongation of the cambial ring of the uninjured axial part. If the wound is closed by the coalescence of the different wound tissues and the union of their cambial zones, the thin-walled tissue of the wound callus (ok) has almost disappeared and has been replaced by actual uniting tissue in which groups of porous cells may be often distinguished from less porous ones, as mentioned above. As indicated by the bark tip (2-3) the wood parenchyma, which takes over the formation of a permanent union, is also produced directly and in fact in the angles where the bark strip and wood body join, i. e. where the indicating line from kg ends. When it is perceived that the bark strips (3 R L) have been so raised by the budding knife, that not only the whole cambial zone but also the young sapwood elements already differentiated remain attached to them, then it is evident that this connecting tissue is a product of sapwood cells already somewhat older (not those most recently formed). This tissue is not produced from the wound callus (which is never formed in the inner angles) but from the division of cells already destined to be wood cells and vessels. We have, therefore, three different factors which furnish a similar product, the wood parenchyma, already described as the uniting tissue, which takes over the process of uniting scion and stock. The first factor is the bark strip from the stock, the second the callus of the exposed wood body, the third the scion. The momentary strength of the different factors determines which one of these three actually produces the union in a grow- ing graft or bud. The variations which may be observed are extraordi- narily great. The quickest possible formation of wound callus, which takes over the temporary closing of the wound, is essential for the success of the graft. However, the union becomes permanent only if the cambial zone (cc) of the strips (2 L) which forms the new wood and which I have occasionally called “the mobile wound-wall” occurs in permanent union with the cambial zone (c) of the scion (or bud) and forms wood elements remaining in a connected layer. The mobile wound-wall shows the charac- ter of the usual overgrowth edge by its cambial zone which is spirally twisted on the free side, and distinguished from this overgrowth edge, the “fixed wound-wall,’ by the large, inpushed zone of wood parenchyma (kg), which passes out from the fixed wound-wall. The point of union of the cambial zones of stock and scion (or bud) is recognizable not only in the year of the union but remains so for many years, by the course of the wood elements. In the line of union, which extends from c to cc, the elements are more or less strongly elongated tangentially, while in the interior of the wound-wall they have already assumed the normal vertical arrangement and, therefore, in cross section appear actually cut across (hh’), thus resem- bling the normal wood (hh). If, in the production of this uniting tissue, the cambial zone (c) of the scion (or bud) unites with that of the stock (cc) to form a continuous ring, it is evident that this ring is not everywhere 837 equally distant from the centre as in an ungrafted or unbudded trunk, but at z and cc shows a deep depression, an S-like curvature. This curved line of union, GOppert’s “line of demarcation,” is visible to the naked eye and is noticeable even in the bark covering’. In the second, usual method of budding “with a heel,” the bud is cut from the branch with a little piece of wood attached and is shoved into the stock. In this the processes of healing vary somewhat from those described above. The disadvantage in this method is a retarding of the union; the advantage, however, lies in the increased certainty of preserving the bud. In separating the bark shield from the wood body, for the purpose of bark budding, the actual bud cone is not infrequently left on the branch if its vascular bundle cylinder has been too greatly lignified. The bud on the bark shield then has a hole on its underside and does not sprout. Untrained workers overlook this little hole and bud in vain. The same process of healing, as in budding with a heel, is found in bark grafting. Only in this case the stock is more injured since it must first be cut square off, then the bark on one side is split and somewhat raised for the in- sertion of the scion as is done in bud- ding. Instead of the single eye a diag- onally cut branch is used, bearing several buds. The slanting cut surface forms simple overgrowth edges, 1. e. fixed wound-walls, which unite with the mobile wound-walls of the bark strips of the stock and the uniting tis- sue of its exposed wood surface. In ; : F Fig. 200. Bark graft of Aesculus, with bark grafting (“whip grafting”), how- 4 adventinioca: Buds. ever, the stock has more to do and stores up less reserve plastic material, since the part of the cross section on the end surface of the stock not covered by the scion must also be overgrown. The luxuriance, to which the process of coalescence can attain in bark grafting on strong stock, is shown by the accompanying drawing (Fig. 200), 1 The difference between the present experiments and previous work lies in the proof of the different origin of the tissue of union or, according to Géppert, the “inter- mediary cell tissue.” He thinks that the production of the tissue which, in common with the cambium, takes over the coalescence, must come from the medullary rays, while Hanstein considers the whole tissue of union to be produced by the cambium alone. Actually, all elements, still capable of new formation, can take part in the formation of the wound callus and tissue of union. In many trees, for example, good instances of wound callus may be obtained which is formed from the pith body, particularly the pith crown. (Tilia.) 838 of the grafting of Aesculus rubicunda on Aesculus Hippocastanum, taken from nature. A few weeks after the grafting the new structures on the inner side of the bark strips (ul) of the stock had become so extensive that they stood out like wings from the scion and produced adventitious buds (a) on the cut surface. CoPpULATION AND GRAFTING. In copulation, the lower end of the scion and the upper end of the stock are cut slanting, and, when possible, both are of the same size. The two cut surfaces are so fitted to one another that the respective tissues of both coincide. Thus we have here simply two surface wounds. These form complete overgrowth edges which push in between the scion and stock. When the manipulation is well carried out and the space between the wound surfaces very small, the closing of the wound is so perfect that even the microscope can show no spaces between the old wood of the cut surfaces and the compressed connecting tissue. Gdppert finds that, in copulation, this connecting tissue dies in a young condition without disappearing, while in grafting, when the union is complete, it remains for a long time organically active. In my experience, no such difference dependent upon the method used has appeared in the length of life of the connecting tissue. In older cases, holes may indeed be noticed, or brown, decayed masses of dead tissue. It seems to me, however, that this would occur in all grafting without any distinction as to method used, if the wound by very careful adjustment of stock and scion has been closed by the wound callus first produced without any subsequent formation of woody parenchymatous connective tissue in the union. Copulation may, therefore, retain the value and the universal application which it has had up to the present. However, I consider the simplest form to be the best and the so-called English grafting, as well as Thouin’s methods (Miller, Kuffner, Ferrari, etc.) disadvantageous or even injurious and trifling. Cleft grafting may be considered as the most dangerous operation. The stock is usually cut off square and split once, or several times, deep into the wood. The scion is cut wedge shape and so clamped in the cleft that its cambial zone forms the connection between the two parts of the cambial ring of the stock separated by the cleft. In case the wedge-shaped scion is not herbaceous, it will on both sides produce wound walls from the remaining part of its cambium alone. This occurs also on the split edges of the stock. The united connecting masses will endeavor to fill out the space in the old wood. On an average, this succeeds very rarely; in spite of the grafting wax, moisture penetrates into the split from the square cut surface of the stock and easily causes decay or allows some fungus to enter. The process of grafting naturally does not depend upon the existence of a definite cambial zone but will be possible also in monocotyledons. Daniel gives an example of this; he carried out grafting experiments suc- cessfully with Vanilla and Philodendron. 1 Daniel, L., Greffe de quelques Munocotyledones sur elles-m€mes. Compt. rend. 1899, II, p. 654. 839 In concluding this consideration of the healing processes of wounds, it should be emphasized once more that the decision as to the relative value of the grafting method used refers here only to axes at least one year old and already provided with well developed wood. In grafting the,soft wood of woody plants, or herbaceous plants, the choice of method may be governed by purely practical considerations. In the coalescence usually so many elements of the cut surfaces (older bark and wood elements in pith) partici- pate in the formation of wound callus that a close union takes place under all circumstances favorable for the plant body, provided, of course, that a sufficient relationship exists between scion and stock. THE LONGEVITY OF GRAFTED OR BUDDED INDIVIDUALS. It cannot be denied that, aside from the possible action of different peculiarities of the two grafted parts on one another, grafting influences the development of the individual. As Duhamel has already emphasized, the tissue changes at the place grafted will at any rate cause a change in the conductive capacity. The connecting layer will produce retardation of the water conduction and an easier storing up of the descending, plastic ma- terials in the part which consists of wood parenchyma, rich in starch, as also later when the connecting layer is formed from interwoven prosenchyma elements. The results of these changes have already been discussed. The limit, up to which different individuals can be united with one another to form a persistent, normally functioning organism, as yet little understood, may be determined by the fact that, in general, only plants of the same natural families can be grafted (or budded) upon one another with any prospect of success. According to all previous experience, this would, however, represent the extreme limit. A sufficient number of examples are known of cases where members of the same family cannot be united perma- nently. In fact, varieties of the same family can remain united for a few years and then in the end break the union, in which case, as a rule, one part dies. It is probable that, aside from the material relationship, a similar biological development is absolutely necessary in the two individuals which are to unite. I, therefore, believe that the different beginning and end of the vegetative phases (leaf formation, setting of fruit, etc.) and the different amounts of water needed by the individuals is very decisive for the perma- nence of even those unions which were successful in the beginning. Often such cases of grafting remain fresh for many months without any firm union. In herbaceous grafting of heterogeneous varieties, or organs, it is found that the scion often continues growth and develops a sickly inflor- escence but finally dies. So far as I have had insight into this matter, no union had taken place. Both parts may have done their best; all their tissues, capable of developing further, can produce new structures and even, in places, a nominal wound callus but a brown stripe extends between the tissue masses of both parts, which shows at once to which individual the tissue in question belongs. The brown stripe is either formed 840 of the swollen walls of the outermost cells, or caused by the collapse of all the cells of the wound edges. Usually on the boundary a cork layer has been formed by the suberization of the walls of the peripheral parenchyma cells or, besides this, by the appearance of actual cork cells. In genera which finally unite, as, for example, Iresine on Alternanthera, it is found that for whole stretches of the grafted surfaces, the connecting tissues grow side by side, cut off from each other by a cork layer. Similar cases may be proved in root grafts (Bignonia) and it could be ‘observed in cleft grafts of Paeonia arborea on fleshy roots of Paeonia offici- nalis that the root, as stock, had served only as a receptacle for the scion. This latter had formed roots without any union with the stock. Root grafting is in general a very good method. Even for our fruit trees it had been used by Sickler at the end of the seventeenth (?) century and later Seigerschmidt in Mako recommended it very highly*. Root pieces, varying in thickness from the size of a quill to that of one’s thumb, seemed suitable, if provided with fine roots. They were cut in pieces eight to twelve cm. long, were grafted by copulation or cleft grafted and the place of union covered with earth until only two or three eyes extended above the soil. Trunks of old seed- or stone-fruits give an abundant material for stock, when they have to be removed. Of course, the roots must be very healthy. The method of grafting roses on pieces of roots in January or February has been adopted already. For Clematis and other woody plants, this method of grafting is becoming more and more of a favorite. It may be presumed from the very beginning that under certain cir- cumstances which condition a scanty coalescence, the life period of a graft will be very short. The question, whether the process of grafting in itself limits the life period, as Thouin and Goppert have stated, must be laid aside. It cannot be denied that grafted fruit trees, on an average, are shorter lived than those grown on their own roots. It may even be granted that a dying of the trees, as GOppert has observed, is initiated in the line of demarcation by a gradual rotting of the place of union but it is not credible that this process of rotting may be the cause of actual death, or even of diséase, in grafted trees. It is found, on the contrary, that even badly united copulants, which at first may have been simply stuck together on one side, can in the end give perfectly healthy permanent trunks. The old places of union have the firmest wood. A storm may twist the trees off more easily at any other place than at that of the union. Goppert’s observations may possibly hold as the rule only in old trunks which have been regrafted later. I would explain the comparatively earlier death of grafted trunks by the fact that not only better but also more tender cultural varieties are used for grafting. These, aside from the disturbances which they undergo in the cutting, are in themselves more susceptible to disturbances in growth and to unfavorable weather than the specimens grown from the seed, which approach more or less the hardier nature of the stock. 1 Weiner, Obst- und Gartenzeitung 1876, p. 587. 841 MutTuAL INFLUENCE OF SCION AND STOCK. In regard to the influence of the stock on the scion, the experience of practical growers has shown for some time that apples set on Paradise stock retain a lower habit of growth and at times bear fruit even in the first year after grafting. In the Doucin the forms become larger and fertility begins after a few years, while the scion, on a stock of Pirus Malus, attains the usual tree form and bears fruit only after a considerable number of years. For pears, the quince and Crataegus, which love moist soils, form the best dwarf stock. For exposed or dry positions, Pirus Malus prunifolia major, together with P. M. baccata cerasiformis, the cherry apple, have been recommended from several localities as stock for apples’. P. M. prunifolia, originating in Siberia, is hardy and may be used as a street tree. It differs from the variety of P. M. baccata by its conspicuous, retained calyx. With the variety of P. M. baccata belongs also P. M. cerasiformis, which drops its calyx at the time of ripening. Lindemuth states, in regard to the life period of tree trunks, that varie- ties grafted on Paradise stock seldom live more than 15 to 20 years, while specimens grafted on seedlings of true tree varieties of Malus can become 150 to 200 years old. Of the remaining literature, we will mention the following examples: Sour cherries grafted on sweet cherries thrive less well than sweet varieties on sour ones*. Oberdieck found that sweet cherries bore abun- dantly on sour cherries. Treviranus*® quotes that walnut and chestnut trees of the late sprouting varieties are said never to succeed on early sprouting varieties (according to Cabanis, Traité de la greffe). On the other hand, in seed fruits, this method of grafting later varieties on early ones is said to have good results and to bring about an earlier ripening of the fruit*. In peaches, grafting in itself, whether of early varieties on late varieties, or conversely, seems -to give good results. Gauthier reported to the Parisian Société cent. d’ Horticulture’ that he had grafted peaches in August or September on typical fruit spurs (coursonnes), as well as on those which have elongated, both late varieties on early varieties, and conversely. The fruits are said to become larger because, in the tree which is grafted with a late ripening variety, the fruit of the stock can be harvested first and then the tree can use its remaining strength to mature the fruit on the branches of the grafted, late variety. In the opposite cases, of grafting on late varieties, the whole tree becomes stronger because late varieties in general have a more luxuriant habit of growth. 1 Lieb, Pyrus Malus prunifolia major. Pomolog. Monatshefte 1879, p. 130. 2 Lindemuth, Vegetative Bastarderzeugung durch Impfung. Landwirtsch. Jahrbticher 1878, Part 6. 3 Treviranus, Physiologie der Gewdchse II, 1838, p. 648 ff. 4 y. Ehrenfels, Uber die Krankheiten und Verletzungen der Frucht- und Gar- tenbaéume. Breslau 1795, p. 108. 5 Ortgies, Vorteilhaftes Pfropfen von Pfirsichb’umen. Pomolog. Monatshefte v. Lucas 1879, p. 61. 842 An older example from Duhamel’ should be mentioned in this connec- tion. Almonds grafted on plums and, conversely, plums on almonds, at first grow very well but usually retrogress after one or several years. The almond has a much more luxuriant habit of growth, sprouts earlier in the year and, as scion, forms a strong roll at the place of ‘grafting. It is probable, therefore, that such a scion, requiring more water earlier and constantly, will thrive on a less luxuriant stock as long as this is able to satisfy the young twigs from its reserve store in the trunk. If the grafted branch becomes several years old, its needs become greater and, if it cannot accommodate itself to the stock, as frequently occurs (dwarf trees of seed fruits), it gradually degenerates from a lack of nutriment. The results vary greatly, according to soil, amount of water and variety. Conversely, a stock which blossoms too early and grows too luxuriantly will supply more to a scion, requiring a lesser amount, than this can take up. The super- fluous material from the stock is quickly worked over into new structures. If many groups of buds are present, this excess manifests itself in the pro- duction of long shoots. If, however, as in grafting, most of the lateral buds, or eyes, are suppressed, the material remains at the disposal of the thickening ring of the trunk. Thus, instead of prosenchymatous elements, aggregations of wood parenchyma are formed, which, in the Amygdalaceae, easily become gum centres as I also have observed. Among the older observers, Duhamel reports that almond stock, grafted with plum scions, will die from gummosis at the place of grafting. Experience has also taught, in the very general practice of grafting pears on quince or apples on Paradise stock, that death sets in the more quickly for rapid growing scions, the drier the soil and the fewer the roots which the stock has developed in it. The scions fail much the more rapidly. Duhamel also cites cases when, under such disproportionate need of water in scion and stock, even simple transplanting has led to death through failure of union (almonds on plum stock), while the little trees of the same series, left standing in the nurseries, remain healthy. The pruning of the roots in transplanting has decreased too greatly the momentary capacity of water absorption in the stock. Peaches on prune stock are also said to give no especially permanent union?. The wood of the scion is said to turn red and soon degenerate. I would add here an experiment with the grafting of raspberries on Rosa canina*. Among rubus scions grafted by copulation, I found two branches developing on one specimen, one of which bore four normal raspberries. In the autumn, however, the scion died and, upon inves- tigation, the coalescence was found to have been very slight. On the upper part of the surface of copulation, only the stock had developed cicatrization tissue. On the other hand, on the lower part of Rosa, as on Rubus, abundant wound callus had been formed, showing normal processes of coalescence. Duhamel du Monceau, La physique des arbres 1758, II, p. 89. Pomolog. Monatshefte 1879, p. 370. Sorauer, P. Rubus auf Rosa. Zeitschr. f. Pflanzenkrankh, 1898, p. 227. one 843 Evergreen foliage seems to be no hindrance to growth on deciduous stock. Scions of Prunus laurocerasus on Pr. Padus, of Quercus Ilex and QO. Suber on Q. sessiliflora, of Cedrus Libani on Larix europaea are said to thrive but there is no report as yet as to a favorable growth of deciduous wood on evergreen stock. Thouin contradicts the former statement’. Of the noteworthy results of Duhamel’s experiments, it should be men- tioned here that, for example, the fruit of the winter Christ pear on quince had a more delicate, juicier flesh and a finer, deeper colored skin, as con- trasted with scions grafted on wild stock. Leclerc du Sablon* observed that pears grafted on pears store up less reserve substances in their aérial parts than when grafted on quince stock, while the roots are poorer in reserve substances. This latter fact might be explained by the greater fer- tility after grafting on quince stock. It is remarkable that pears and apples, which form so perfect a union with remotely related stock, can never, or rarely ever, be brought to form a permanent union with each other. Numerous experiments have been made in this connection. Thus Knight* reports a case of apple on pear stock, which for one year yielded an abundant harvest but died the following winter. The fruit is said to have had blackened cores, not containing a single seed. Recent observers have affirmed this fact in generai, but em- phasize the fact that exceptions may occur. Thus Stoll* reports that apple scions took well on pear trees and bore very soon but the fruit was small and the graft usually died in the fourth year. The head gardener, Seifert, in Segeberg (Holstein) describes a five year old apple graft on pear stock which in the fourth year had borne six well developed apples (Ribston Pippin). The apples had a good flavor but the crown of the tree had a weak growth. I have known of some favorable results from pear grafts on apples. In Czerwentzitz, near Ratibor, many examples were found of pears which had been grafted on apples. The method was in use at least ten years ago. In the first experiment (Geisshirten pear on apple) it was found that after the second year the fruit from pears on apple stock ripened two weeks earlier than on the main trunk. The scion lived eight years. Less vigorous stock gave no good results. Most varieties, to be sure, remained alive but made no growth. When the same grafting was repeated on the middle branches of the crown, a number of specimens died after two or three years. The others lived in a weak condition for some time without setting fruit. A note by Gillemot® originates from this period. He had two-year-old pear grafts on apple stock and also had grafted cherry scions (Royal Amarelle) in the bark of a plum (Prunia institita). The scions developed very long 1 Thouin, Monographie des Pfropfens. Berg’s translation, 1824, p. 114. 2 Leclere du Sablon, Sur l’influence du sujet sur le greffon. Compt. rend. 1903, CXXXV. p. 623. 3 Hort. Transact. II, p. 201. 4 Stoll, Das Veredeln von Birnen auf Apfeln. Wiener Obst- und Gartenzeit. LSTG6; py LO: 5 Gillemot, Beitrag zur Veredlung verschiedenartiger Gewachse aufeinander. Wiener Obst- u. Gartenzeit. 1876, p. 121. 844 shoots and bore comparatively many and handsome fruits in the second year but died after bearing. Up to the present, such experiments have been repeated on all sides but as yet no further desirable results have been attained than those known for a long time in regard to the use of dwarf stock. In some cases it was evident that the manner of grafting decided the success. Thus, for example, Carriére’ reports that the varieties of pears Bon chrétien Rans, Doyenne de Juillet, Beurre’ Gifford, Beurré Box. did not grow, or died soon after pro- ducing weak shoots, if they were budded on quince (greffé en ecusson). On the other hand, the results are considerably more favorable, if cleft-grafting is adopted and branch tips used as scions. The fertility is unusually great. Ligustrum ovalifolium as stock is also said to behave differently with differ- ent varieties of lilac. Only Syringa Josikea is said to succeed when budded (greffé en écussion) while Syringa Emadi persica and others develop well only when cleft grafted (greffé en fente). Recently special attention has been given this question in the grafting of grapes because of the struggle against the grape louse. The number of works on this subject is very great, so that we call attention only to a few important ones. First of all Couderc? determined, by questioning about 450 French grape growers, that even the power of resistance of an American stock to the attack of the grape louse is usually somewhat reduced by graft- ing and also that the different varieties used as scions exercise an influence varying in intensity. Cases occur, however, in which a very vigorous scion can increase the power of resistance. Ravaz*, among others, lays especial emphasis on the fact that the stock influences the growth of the scion and also its fertility. We owe to Hotter* precise figures on the changes in grapes, due to the influ- ence of the stock. He investigated different varieties of grapes grown on vines grafted on Riparia and on self roots of vines of the same varieties. Among 9 varieties, 77 per cent. of the juice from the grafted vines contained more acid than that from the non-grafted vines, of which 65 per cent. con- tained more sugar than those grafted on American stock. These statements are directly opposite to those of Curtel®, who found the fruit of grafted vines larger, the skin thinner and the seeds less numerous but larger. The juice was richer in sugar than acid, poorer in ash elements, especially phos- phates, richer in nitrogenous elements but poorer in tannin. We have purposely cited both observations in order to show how differently the stock 1 Carriére, Quelques observations & propos de la greffe. Revue hort. 1876, II, p. 208. 2 From the Weinbau-Kongress of the 16th to 19th of August, 1894 in Lyon; cit. Zeitschr. f. Pflanzenkrankh. 1895, p. 118. 3 Ravaz, L., Choix des porte-greffes. Revue de viticulture 1895, Nos. 100, 105, 106. 4 Hotter, E., Der Einfluss der amerikanischen Unterlagsreben auf die Qualitat des Weines; cit. Centralbl. f. Agrikulturchemie 1905, p. 625. 5 Curtel, G., De l’influence de la greffe sur la composition du raisin. Compt. rend. 1904. Vol. CXXXIX, p. 491. 845 can act. We find further experiences reported in the Memoirs of the Im- perial Department of Health in Berlin. Thus, for example, the twenty-fifth Memoir confirms the above men- tioned observation that the American vine, when grafted, loses in power of resistance to the grape louse, jaundice, etc’. In regard to the technic which has come into use in grafting grapes, we will follow Schmitthenner’s? statements. He emphasizes the fact that, at present, the so-called English tongue grafting is almost universally used. This is a form of splice grafting in which the diagonal cut is not long but the cut surface of graft and stock have also an axial incision. The scion is split and shoved into the cleft of the stock so that scion and stock dovetail. Ana- tomical investigation shows that in grafting grapes the activity of the cambium is more reduced than in any other form of grafting; the annual ring formed after grafting is much weaker than the normal one. The influence of the wound is much more considerable than in grafting other woody plants and extends even to the next node, since all the ducts are filled with corky tyloses containing wound gum. Tompa® had already given detailed anatomical data on grafting grapes in a herbaceous condition. However, the grafting of grapes will be com- pletely effective only if one uses as stock, not the American varieties, but hybrids of those which are adapted to the various localities*. Since the end of the last century, the formation of hybrids by grafting has been better understood. The best known example is Cytisus Adami which is said to have come from the grafting of Cytisus purpureus on Labur- num vulgare and, at times since 1826, has produced on different branches sometimes the blossoms of one variety, sometimes those of the other. According to A. Braun® the retrogression did not appear until sixteen years after the grafting. Laubert* found that retrogressive formation should be ascribed to a bud variation, in which the branch form, representing Cytisus purpureus, also completely resembles anatomically the true variety. Bei- jerinck’ found that this bud variation could be incited often by wound stimulus. The description of a different example was published in 1875°. In an English grape house, a vine which had been grafted with Black Alicante was re-grafted some time later with three varieties on the Black Alicante as 1 Funfundzwanzigste Denkschrift betreffend die Bekampfung der Rehlaus- krankheit. Bearbeitet im Kaiserl. Gesundheitsamte bis October 1, 1903. 2 Schmitthenner, F., Verwachsungserscheinungen an Ampelopsis- und Vitis- Veredlungen. Internat. phytopath. Dienst. 1908, No. 1. 3 Tompa, A., Soudure de la greffe herbacée de la vigne. Annal Instit. ampélo- logique hongrois 1900, Vol. I, No. 1. 4 Teleki, Andor, Die Rekonstruktion der Weingarten usw. Wien und Leipzig, Hartlebens Verlag, 1907. 5 Bot. Jahresber. 1873, p. 537. 6 Laubert, R., Anatomische und morphologische Studien am Bastard Labur- num Adami. Poir. Bot. Centralbl. Supplementary Volume X, Part 3. 7 Beijerinck, M. W., Beobachtungen iiber die Entstehung von Cytisus purpureus aus Cystisus Adami. Ber. d. Deutsch. Bot. Ges. 1908, Part 2, p. 137. 8 Grieve, Culford, Bury St. Edmunds, Singular Sport of a Grape Vine. Gard. /Chrons 1875; p: 21. 846 stock. One of these three varieties, together with a small piece of its stock, was cut off later. Immediately a sprout, standing near the centre of the branch of the second inserted variety (Trebbiano) showed a spur with grapes which resembled absolutely the variety (Golden Champion) which had been removed. On either side of this abnormal spur, the Trebbiano stock bore its characteristic fruit. Therefore, no other hypothesis remains possible than that the Champion variety, which had been removed, had exercised an influence backward into the stock (Black Alicante) and through this to the laterally grafted Trebbiano variety. Lackner has cited another remarkable and older case’. He found in the garden Palavicini near Genoa, under the name Maravilla di Spana, an orange (Bigardia bizarro Riss.) which, on parts of its outer surface, showed callus excrescences and corresponding ones in the flesh, resembling in places a lemon, in others an orange and sometimes candied lemon peel. It has been proved that this form originated about 1640 when a gardener in Florence grafted some stock but the scion did not take. Directly beneath the place grafted, however, a branch appeared which bore this very remarkable fruit. The blossoms are likewise different, some being white, others red. In 1873 the “Revue horticole” published a case in which a Mr. Zen had bred new rose varieties by grafting. These varieties remained true. Focke* mentions a white moss rose which had been grafted on a red Centifolia. Such a plant developed bottom shoots which bore some white moss roses, some Centifolia and also moss roses with partly red petals. Besides the roses here described, Pirus, Begonia, Oxyria and Abies have also been named as genera in which graft hybrids can occur. Daniels found a backward action of the scion on the stock in one in- stance in which old pears, grafted on quince, had been sawed off 2 m. above the surface of the soil. Branches developed from these naked stumps, some bearing normal quince leaves, others mixed forms, between quince and pear’. This same author, in collaboration with Jurie, cites similar instances in grafted grapes. Of these, however, Ravaz‘ has proved that such variations also occur in non-grafted vines. Such cases of interchange occur often; there is always a tendency to trace formal differences back to the special influence of the grafting, which, in fact, are only variations in luxuriant branches. Such variations appear also after severe pruning of the older axes. We need recall only the manifold leaf forms on the bottom shoots of Morus, Populus, etc., after the trunks have been sawed off. The majority of errors occur in grafting experiments on herbaceous plants. For this we have also examples by Daniel®, who grafted turnip 1 Lackner, Einfluss des Edelreises auf die Unterlage bei Orangen. Monatsschrift d. Ver. z. Bef. des Gartenbaues v. Wittmark 1878, p. 54. 2 Focke, Die Pflanzen-Mischlinge. Hin Beitrag zu Biologie der Gewichse. Bot. Centralbl. 1880, p. 1428. 3 Daniel L. Un nouvel de la greffe. Compt. rend, 1903, Vol. XX XVII. 4 Ravaz, L., Sur les variations de la vigne greffée; response a4 M. L. Daniel. Montpellier 1904. 5 Daniel L., Creation des variétés nouvelles au moyen de la greffe. Compt, rend. 1894, I, p. 992. 847 rooted cabbages on Alliaria and this on the green cabbage. He found mor- phological and anatomical differences in the plants produced from the seed of the grafted specimens. Under this head belong also potato grafting experiments and the grafting of Solanum Lycopersicum on potatoes. In regard to the grafting of various Solanaceae on each other there exist very many experiments which we have described more fully in the second edition of this manual (cf., p. 692 ff). The most thorough experiments, continued up to the present time, are those by Lindemuth, whose investigations have been considered under the section on Albinism (cf., p. 677 ff). Molisch' has repeated earlier experiments and, agreeing with Strasburger and Vochting, has arrived at the conclusion that the production of graft hybrids may well be explained theoretically but has not actually been satisfactorily proven since, as he says, he and the others had found that scion and stock always retain their morphological character. We are not able to share this point of view since Lindemuth’s* latest experiments, as well as those of E. Baur, sufficiently demonstrate the influ- ence of the scion on the stock. Nevertheless, bud variations in many cases are also found which have nothing to do with the material influence of the scion on the stock but are probably traceable to wound stimulus. Arrest- ment phenomena of very different kinds, as, for example, increased pressure in the bud, can initiate a different development of the young axis. The influence of the stock on the scion is a well known fact in horticul- ture. We will recall only the different effect of the stock on one and the same apple variety. Grafted on Doucin, a stronger wood growth and a later fertility was produced, on Paradise stock a lesser wood growth and an earlier setting of fruit. No general rule may be laid down. The result depends not only on the plant variety but also on the accessory conditions (age, habitat, form of nutrition, etc.). THe NATURAL PROCESSES OF COALESCENCE. Very frequently we find in hedges the union of two branches, which oftentimes have grown toward each other from opposite directions. The same phenomenon may be observed in roots in dense tracts of trees. The root fusions can take place in a young stage of the organ at a time when the epidermis is still capable of division. According to Franke® this process appears in the ivy (Hedera Helix) and the wax flower (Hoya car- nosa), in both of which plants the epidermal cells of two adjacent roots grow toward each other like papillae and unite. These cells then divide and thereby produce a few layers of connecting tissue. This, however, does not have the firmness of the connecting tissue produced from the cambial zone 1 Molisch, H., Uber Pfropfungen. Lotos 1896; cit. Bot. Jahresber. 1897, I, p. 155. 2 Lindemuth, H., Kitaibelia vitifolia Willd. mit goldgelb marmorierten Blittern, Gartenflora 1889, p. 431. Uber Veredlungsversuche mit Malvaceen. Ibid. 1901, No. 1. 3 Franke, Beitrage z. Kenntnis der Wurzelverwachsungen. Beitrige z. Biologie der Pflanzen von F. Cohn, Vol. III, Part 3; cit. Bot. Centralbl, 1882. Vol. X, No. 11, p. 401. 848 in two bark-covered roots of older, woody plants. The same process sets in here as in the union of aérial organs. The bark on the surfaces of contact is sometimes pushed toward the outside, sometimes enclosed like little islands; the cambium no longer increases where the pressure makes itself felt on the places of contact, but unites from a common layer, enclosing both roots. Each year, when properly nourished, this layer forms new wood layers above the place of union. In regard to the anatomical conditions in the coalescence of tree trunks, we will refer to Kuster’s different works! and will mention here only one rare case which we have observed personally. This was found in the Ellguther forest, near Pros- kau, in a pine; at several places on its trunk a second, thinner trunk had grown fast by natural in-arching. The base of the weaker tree had been cut off many years before so that the trunk was obliged to draw its nourishment entirely from the older pine. At the time observed, they were perfectly healthy, and formed a common crown; only it seemed to me that the in-arched, root- less trunk bore somewhat shorter needles. I possess a piece of the trunk of another pine in which the tip of a branch, possibly five cm. in diameter, had bored into RL ny Mi, LENE the main axis and there disap- Fig. 201. Pine from the Ellguther forest in peared entirely. This is an which one trunk has continued to nourish a example of so-called “handled second, rootless one connected by natural : ae grafting. trees. All processes of this kind arise from the ability of the cambial tissue to form connecting layers between different axes. The processes differ from grafting only in the previous separation of the cambial layers by the bark of the plant parts; these layers 1 Kiister, E., ther Stammverwachsungen. Jahrb. f. wiss. Bot. Vol. 3,O,S, ON1e Part 3.—Pathologische Pflanzenanatomie. Jena 1903, Gustav Fischer, p. 1738, Section Wound Wood. 849 unite later. The bark must have been removed by gradual rubbing. If the union of the axes takes place of itself, a connected wood covering is depos- ited each year over the place of union. Often rather larger brown pieces of dead bark are incorporated in the surface of the union. This may be explained by the uneven formation of the two axes which have come in contact. If two trunks, covered with bark scales, touch each other, the most prominent places are rubbed down first and unite, while more deeply lying hollows do not participate in the union but are enclosed by the new tissue. In forests and especially spruce and pine tracts, twin trunks are fre- quently met with, which, beginning at the base, had united for different distances. Less frequent are the cases in which the upper parts of the main axes of separate origin have grown together. A cross section of the base of a twin trunk often shows three centres. In conifers, the middle, third stem has, as a rule, become very resinous. At any rate, the top of the main axis was broken off when young and two lateral eyes have taken over the growth. Instead of forming horizontal branches, these have developed into two top shoots which, after a consider- able number of years, have suppressed the dying main axis and finally over- grown it. Their overgrowth edges have gradually united so that, finally, one single, united cylinder has come from the three axes. According to the experiments mentioned under grafting, it may be assumed as a definite fact that a union can take place between parts of indi- viduals of different kinds. Spruces and firs, apples and pears, with each other and on quinces, or almonds and plums, and the like, may serve as examples well known to all. Nevertheless, a limit in the relationship of the plants certainly exists here, beyond which actual coalescence cannot take place in spite of the closest contact and vigorous rubbing. To be sure, a whole list of reports on the union of very heterogeneous plants may be found in the literature on this subject but a part of these statements is based cer- tainly upon erroneous observations’ in which union was assumed where only overgrowth took place. Having so fully described the processes of wound healing, we may here, without being misunderstood, express the opinion that the apparently rigid wood body of a tree may be caused to take on all imaginable forms if the tissue produced from the cambium is confined in some way. It can be said figuratively that the wood trunk flows about any object standing permanently in the way of its growth in thickness; it grows over it and can enclose it entirely. Examples of so-called encysted stones, fir cones and even animal mummies have frequently been observed. We can here omit the enumeration of special cases, since we now possess a number of most interesting books about remarkable trees and all 1 Moquin Tandon, Pflanzen-Teratologie, Schauer’s translation, 1842, p. 274. Masters, Vegetable Teratology 1869, p. 55. 850 kinds of botanical nature curiosities. The one by Ludwig Kleint may be the most instructive at present. This seems especially fitted to arouse and increase a love of trees by its more than 200 illustrations, made from photo- graphic exposures. WouND PROTECTION. We have already partially discussed natural wound protection in so far as it is produced by cork formation. In the wood body of trees, however, no cork deposit is found rapidly covering the surface of the wound, but the vessels in all such places are filled with tyloses or a gummy substance (wound gum) usually easily soluble in boiling nitric acid (dissolved with difficulty in the Correae). This is found when healthy wood adjoins the dead wood. Asa rule, the tyloses are accompanied by some gum formation. Both kinds of filling make the wood of the branch stump absolutely imper- vious to water and air and quickly close the wound within the period of growth. It is evident from this observation that we would do well to thin our trees in winter shortly before cambial activity begins*. In a great number of woody plants, the vessels and frequently many of the other wood elements are filled with calcium carbonate*. This is found, as a rule, in the heart wood and those tissues of which the cells have a chemical and physical constitution resembling heart wood, such as the pith enclosed by the heart wood and the dead, discolored wood of knots and wounds. ‘This filling is usually so complete that, after such pieces of wood have been burned, solid calcium casts of the cells are found which had con- tained the carbonate. The process may be explained as follows: whenever opportunity is afforded, the soil water, containing the calcium in the form of bi-carbonate, quickly passes through the wood cells and vessels, and gives off carbon dioxid; it also deposits the calcium, which is no longer soluble, as a precipitate on the inner side of the vessels. In living heart wood which, unlike the growing sapwood, cannot quickly work over the calcium salt, each increase in temperature will cause the giving off of carbon dioxid and induce the precipitation of calcium. In wounds, the carbon dioxid will likewise disappear because of the exposure of the tissue. While the sapwood, which deposits no lime, protects itself from the entrance of air by the formation of tyloses or gum (probably as the result of the entrance of air into vessels previously filled with sap) we find in heart wood a deposition of lime as a means of protection. In the normal trunk, the formation of heart wood occurs first in the advance stages ; after injury, however, it sets in at once and gives rise to the 1 Klein, Ludwig, Bemerkenswerte Baume im Grossherzogtum Baden. Heidel- berg 1908. Winter’s Universitaéatsbuchhandlung. 2 Bohm, Uber die Funktion der vegetabilischen Gefisse. Bot. Zeit. ASS, pyizZ29e The most abundant literature on the formation of Tyloses may be found in Kiister, E., Pathologische Pflanzenanatomie, 1903, p. 98. 3 Molisch, Uber die Ablagerung von kohlensaurem Kalk im Stamme dicotyler Holzgewachse. Sitzungsber. d. mathemat.-naturwissenschaftl. Klasse d. k. Akad. d. Wissensch, zu Wien., Vol. LX XXIII, No. 13 (1881). 851 false heart wood formation’ which, through the action of fungi and bac- teria, can be transformed to heart rot?. This attack by micro-organisms has led to the establishment of a num- ber of parasitic diseases, which, however, essentially arise from disturbances in the process of wound healing. As first in importance, we will name WouNnpD GUM. 33 Prillieux describes this disease as “Gommose bacillaire,’ and Viala as “Roncet.” The leaves remain green but become irregularly cleft and de- formed. In cross section, the wood shows black points and specks which enlarge and loosen its structure. Later the phloem separates from the xylem. On the cut surfaces from which the disease spreads, clefts arise which are infected by saprophytes. Prillieux found that the plant died after three to five years. The black points in the wood arise from a brown, gummy deposit, which fills the vessels and cells of the wood parenchyma and swarms with bacteria (motile rods). Prillieux found in an infection experiment, made in May in the laboratory, the characteristics of the disease, which bear great resem- blance to those of Baccarini’s “Malnaro.” Viala and Foex, as well as Mangin, disagree with Prillieux, in that they hold that the described phenomena of disease can be produced by very dif- ferent causes and are not absent even in healthy plants. This difference in opinion was settled by Rathay*, who proved first of all that gum can occur in perfectly healthy vines. He found gelatinous threads in healthy, one-year-old shoots of Vitis riparia, extending from the ducts and composed of gum. The vessels filled with gum (“gum cells’) may be seen in Fig. 202, 7. This gave the color reactions of the pentoses. In Vitis vinifera, V. Labrusca, V. Solonis, V. arizonica, etc., the reaction is found only in wood two or more years old. If this process occurred in young vines, it could not be observed until July, when the gum is pressed out. In the root, gum formation is less abundant. As Rathay reports, even in the grapevine, a normal heart wood forma- tion may set in finally in plants twenty years old but takes place irregularly since scattered places of the inner sapwood are involved in the change and produce the brown spots, which Prillieux has described as the symptoms of Gummose bacillaire. When such a brown place, extending backward like a 1 Tuzson, J., Anatomische und mykologische Untersuchungen iiber die Zer- setzung und Konservierung des Rotbuchenholzes. Berlin 1905, cit, Centralbl. fiir Bakt. 1905, II, Vol. XV, p. 482. 2 Herrmann, Uber die Kernbildung bei der Buche. Naturf. Ges. Danzig; cit. Bot. Centralbl. 1905, Vol. XCIX. 3 Rathay, E., Uber das Auftreten von Gummi in der Rebe und iiber die “Gom- mose bacillaire.” Kremla, H., Uber Verschiedenheiten im Aschen-Kalk- und Magnesiagehalte von Splint-, Wund- und Wundkernholz der Rebe. Jahresber. d. k, k, Gnolg. u. pomolog. Lehranstalt in Klosterneuburg. Wien. 1896. 852 thread in the sapwood (Fig. 202, 3) is examined, it is found that the broad vessels are filled with a brown gummy mass in which are crystalline precipi- tates of calcium carbonate (k); the contents of the wood parenchyma and medullary ray cells surrounding the vessel are deep brown and the adjoining. narrower vessels (e) are filled with tyloses. Starch is found only in the sapwood; in the heart wood, instead of the starch, brown grains are found which turn to bluish black with ferric chlorid. Stoppages of the vessels are not found in the sapwood but only in the heart wood. They are caused primarily by tyloses, which occur exclusively in the inner heart wood, while, in the outer heart wood ring, stoppage by gum or calcium predominates. Often whole rows of vessels in summer wood are filled with calcium, usually in the carbonate but at times in the oxalate form (Fig. 202, 4). The calcium carbonate, deposited in the youngest parts of the heart wood, is dissolved later. In the same way, the great amount of gum in the sapwood disappears with the change to heart wood. The tissue next to the wound surface in a horizontal wound dies back, more or less. In the living tissue immediately underlying this, the vessels are stopped up by means of gum, farther back by the formation of tyloses. The fact that the vessels have drops and layers of gum only on the parts adjoining the wood parenchyma cells, while the gum is lacking when they adjoin neighboring vessels, proves that it is the wood parenchyma cells which excrete the gum. The changes which characterize the heart wood begin much earlier on wound surfaces than on normal uninjured trunks, extending backward, however, only so far as the wound stimulus was effec- tive. On this account, it is termed ‘‘wound heart wood,” by some observers “false heart wood” in order to distinguish it from true heart wood. Many bacteria are found near the cut surface but not in the deeper part of the various centres of heart wood formation, beginning at the wood surface and extending as light brown tissue stripes through the sapwood. Since the disease agrees in appearance with Gummose bacillaire, it is understood to be an immediate result of injury in older parts of the trunk. This wound stimulus may act chiefly on the protoplasm of the wood parenchyma cells surrounding the vessels; it may be continued further because of the con- tinuity of the protoplasm of adjoining cells and may incite the wood paren- chyma cells to a premature formation of tyloses. These cells, therefore, grow old and die prematurely. The normal secretion of gum, at first very abundant, ceases with the formation of tyloses. The process described is made clearer by an examination of the accompanying figures. In Fig. 202, 2 (an alcohol preparation from a ten-year branch of Vitis riparia), j indicates the boundary between two annual rings; m,m medullary rays, g, gum cells, g’ vessels with strongly contracted gum contents. At the right (Fig. r), are reproduced two gum cells from a one-year-old shoot of Vitis vinifera (blue Tollinger) ; their contracted gum contents are seen in the centre. Only the inner outline of the cell walls is drawn. Fig. 3 is the 2-55 sO TEES o% r=) Sy o 9cos5o 99° —~— < Cf) rey BESO I e : i) ji o4' Sern eo SOo05 rato) os 00 290080 = 04093 Oco 89908 00 + 00 0 oo fs Z rr. b ZOG Uf cou ot ay SR "Con D (te t 0% Yo S Fi SYco ° eo So Ogee fore es rors cee “Oli noo 000° % 000 % 10 tee oe Sen P Linea , oper Ceeeemyg genie le ior : =s2o } SS oe2 Ss’ S28525| |A es ee | StS con @ ad UI i Oe Fig. 202. Stoppage of the ducts in a grapevine suffering from wound decay. (After Rathay.) 854 cross section of a brown wood thread from the sap wood of a very old vine; jJofj, the boundaries of the annual rings; k, a radial, fibrous crystalline aggregation of calcium carbonate imbedded in the brown gum mass of a broad vessel; the contents of the adjoining wood parenchyma, of the libri- form fibres and medullary ray cells are much browned and those lying nearest the vessels ¢#, are filled with tyloses. Fig. 202, 4, shows a vessel in cross section, the adjoining wood paren- chyma cells from a dead piece of wood lying under the terminal wound of a one-year-old shoot. Besides colorless gum, it contains radially arranged, stem-like aggregations of calcium oxalate. The lower figure is that of a vessel with the surrounding wood parenchyma from the heart wood of a very old grapevine. The vessel is filled with tyloses in which are contained crystalline aggregations of calcium carbonate (after Rathay). We have cited this case here because, as typical of many other cases, it proves clearly that the gum formation is the result of wound stimulus and at the same time shows how easily diseases may be listed as parasitic, in which is concerned only a subsequent infection by parasites which infest wounds. This concerns especially herbaceous, fleshy and juicy organs. In this connection, attention should be called to a work by Spieckermann’, who points out especially the resistance of a cork membrane to bacteria and the necessity of a definite high amount of moisture in the surrounding air as well as the water content of the tissue itself, aside from its specific sensitive- ness, in order to make possible bacterial decomposition even on a wound surface. THE SLIMY EXUDATIONS OF TREES. In connection with the relation of parasitic infection to wound surfaces, already mentioned under “Gummose bacillaire,” we will mention here the phenomenon where a usually slimy, or gelatinous, and at time clayey looking exudation is noticeable very frequently in different kinds of trees, and even in summer remains moist and variously colored. According to our conception of the matter, an excessive bleeding of the trunk is involved here from wounds which cannot heal. Molisch? has proved that a local bleeding pressure makes itself felt in every wound which begins to be overgrown. In consequence of the injury, the cambium, as well as the parenchymatous elements of the wood and bark, is incited to increased activity and cell division. With this is connected such an increase of turgor that water is pressed out of the wound often under enormous pressure (at times, 9 atmospheres ). 1 Spieckermann, A., Beitrag zur bakteriellen Wundfaulnis der Kulturflanzen. Landwirtsch. Jahrbiicher 1902, p. 155. 2 Molisch, H., ttber lokalen Blutungsdruck und seine Ursachen. Bot. Zeit. IUD. cit. Just’s Jahresber 1902, II, p. 618. 855 If the analyses of the sap from bleeding grapevines are studied closely’, it is found that besides small quantities of organic substances, nitrogen, phosphoric acid and calcium are also present, i. e. it may be considered as a nutrient solution very well suited for infection by micro-organisms and for their increase. Ludwig has studied this thoroughly’. In a number of pub- lications he describes a white slimy exudation in the oak, birch, Saliceae, etc., due to Leuconostoc Lagerheimii Ludw. with which are associated various fermenting fungi (Saccharomyces Ludwigii Hans, etc.). A “brown slimy exudation,’ found in apples, birches, poplars, horsechestnuts and other fruit and street trees, showed Micro-coccus dendroporthos Ludw., with which is associated Trula monilioides Cord. Ludwig found a “red slime” in the late summer on the stumps of old, healthy beeches and observed in it a filament bacterium (Leptothrix?) and Fusarium moschatum. He met with the same bacterium in a yellowish white bleeding sap with a gelatinous, granular con- sistency in lindens and sometimes in birches. He also found toward the middle of April on fresh branch wounds of a hornbeam a milky looking slime which contained Endomyces vernatis Ludw. together with alcohol producing yeast. In one of his later works* we find mention of mites (Hericia) and eelworms (Rhabditis) as animal companions of such bacteria and fungi. In the Zeitschrift fiir Pflanzenkrankheiten 1899, p. 13, we find a list of all the infesters of slimy exudations which have been confirmed not only for Germany but also for the tropics. Of course this list will be constantly increased according to whether the micro-organisms, belonging to specific localities, have had opportunity to infect the bleeding wounds of trees. The organisms here named may be considered to be injurious to trees only in so far as their infection delays or prevents the closing of the wound. Wounds which have been made by frost, lightning, animals, etc., and intro- duce periodic bleeding, form the primary cause of the slimy exudations. If it is found necessary agriculturally to remove such weakening causes, the only method possible would be to cut out carefully the diseased places and paint the fresh edges of the wound with coal tar. 1 Ravizza, F., Uber das Thriinen der Weinrebe usw. Staz. sperimentali 1888; cit. Biedermann’s Centralbl. f. Agrik. 1888, p. 541. According to investigations by Neubauer and v. Canstein (Annalen der Oenologie, Vol. TV, 1874, Part 4, p. 499) the sap of the grapevine (gathered in the dry year 1874) which, in its fresh condition, is as clear as water, and neutral, but easily becomes clouded by bacterial growth and then reacts as an alkali, contained at the time of experiment 2.1204 g. of solid matter per liter, of which 0.7408 g. were mineral elements and 1.3796 g. organic substance, An analysis of the ash gave 10.494 percent. potassium; 1.437 percent. sulfuric acid; 0.188 pereent. ferric oxid; 2.822 percent. phosphoric acid; 41.293 percent, calcium; 5.534 percent. magnesia; 34.791 percent. carbon dioxid; 2.857 percent. chlorid; 0.810 percent. silicic acid in the raw ash. Besides these acids, an organic magnesia salt, gum, sugar, and calcium tartarate, inosit, succinic acid, oxalic acid and unknown extractive substances, were found. Rotondi and Ghizzoni (Biedermann’s Centralbl. 1879, p. 527) also mention besides starch, sugar which the Neubauer investigations had not found in the fresh sap. Only the volatilized sap which, with the giving off of carbon dioxid and the elimination of calcium phosphate, together with a yellow coloration, had a weakly acid reaction, showed all the sugar reactions. 2 Ludwig, F., Der Milch- und Rotfluss der Béume und ihrer Urheber.—tber das Vorkommen des Moschuspilzes im Saftfluss der Baume; cit. Zeitschr. f. Pflanzen- krankheiten 1892, p. 159, 160. 3 Ludwig, F., ttber die Milben der Baumfliisse und das Vorkommen des Hericia Robini Canestrini in Deutschland. Zeitsch. f. Pflanzenkrankh. 1906, p. 137. 850 ‘Root INJURIES. Having thoroughly discussed the overgrowth processes of the aérial axis after all kinds of injury, we can quickly summarize the healing of root wounds. They correspond with those of the aérial axis and undergo modi- fications only inasmuch as the surrounding medium often interferes with the process of overgrowth. For example, if the soil is very moist, the stage of callus formation is prolonged, the transformation of the callus tissue to the firmer overgrowth edge is slower and the possibility of infection by wood de- stroying fungi greater. These factors, however, become less significant if the root wound surface is exposed to the air. The influence of light, warmth and dry- ness promotes the closing of the wound and removes any far-reaching influence, from even large wound surfaces, on the condition of health of the whole root. The best proof is found in much fre- quented forests in the vicinity of large cities where the superficial roots are constantly rubbed bare by pedestrians and, nevertheless, find opportunity to cover the edges of the wound with over- growth walls. The adjoining figure illus- trates such a root so worn that only the first formed annual rings are found to be still intact on the upper side. A cross section shows that no parasitic wound decay has occurred at the wounded place; the wood of the lower side is sound. The wounds produced in transplant- ing deserve the most consideration. ji Fig. 203. A. flat-lying root of the Transplanting is a necessary process, alder barked by the tread of fect. which cannot be omitted in any nursery, for trade requires the delivery to the purchaser of trees which, after trans- portation to a permanent place, exhibit the greatest possible capacity for vigorous growth and development. In transplanting older trees with well developed tops and extensive root systems, a cutting off of the larger root-branches cannot be avoided; hence the great danger of attack by parasitic root decay, which gradually advances into the trunk. But even if this danger has been prevented by the painting of the cut places with tar, the transplanting of old trees is always a danger- ous operation because the activity of the root system is retarded until new 857 root fibres may be formed and the top, during this time, must draw water from the reserves stored up in the wood body. Because of the mutual dependence of the subterranean and aérial axes’ it is necessary to cut back the top of the transplanted tree, corresponding to the change in the root system. The further advanced the foliage of the tree, the more necessary is this pruning. In practice, other means for reducing, as far as possible, the evaporation of the aérial parts are used, such as, for example, the wrapping of the trunk, frequent sprinkling of the top, artificial shade, etc. Trees are usually sold from nurseries in a leafless condition but even here the quickly developing foliage requires a sufficient supply of water. This can be made possible only by newly formed roots. It is, therefore, of the greatest importance to deliver the trees in such a condition that they will form new roots as quickly and abundantly as possible. This depends upon the method of growing the trees and the way in which the roots have been cut. The older the root is, the scantier the development of new fibrous roots on the cut surface; the larger the cut surface, the more slowly it is overgrown and the greater the danger of root decay. R. Hartig® has thor- oughly described this for conifers and deciduous trees. On this account, the first rule is to grow the trees so as to avoid as far as possible wide spreading, large roots, such as trees usually form when developing undisturbed in one place and to produce a root system in the form of a ball-of close standing, short but well branched roots. This is done best by repeated cutting of the roots in the first years of growth. Twisting the long tap root is often recommended instead of cutting it, as this would avoid decay. The widely experienced Goppert* holds to this view. Asa fact, twisted roots develop lateral roots quickly on their convex side*. In the water cultures of fruit trees, which I made in Proskau, some seedlings of the.apple, pear, pine, maple, etc., had curved tap roots because they had reached the bottom of the small receptacles and remained there for some time. The root tips of other plants were injured when taken from the sand. . The majority of both kinds of seedlings developed lateral roots much sooner than the uninjured experimental plants, set earlier in larger receptacles. This circumstance seems practical, as a confirmation of the view of those who recommend striving for early root branching in trans- planting by bending the tap root and not injuring it. We cannot, however, approve of this method; in heavy soils, especially, where we had experi- mentally planted apple seedlings with cut back tap roots and others with uninjured but spirally twisted ones, the removal from the soil for the second 1 Kny, L., On correlation in the growth of roots and shoots. (Second paper.) Annals of Botany, Vol. XV, No. 60, Dec., 1901. 2 Hartig, R., Die Zersetzungserscheinungen des Holzes der Nadelb’iume und der Eiche. Berlin 1878.—Lehrbuch d. Pflanzenkrank. 3rd. ed. Berlin 1900. Springer, p. 263. 3 G6ppert, Innere Zustinde d. Biume nach Ausseren Verletzungen. Breslau 1873. 4 Noll, Fr., ther den bestimmenden Einfluss von Wurzelkriimmungen auf Entstehung und Anordnung der Seitenwurzeln, Landwirtsch. Jahrbticher 1900; cit. Zeitschr. f. Pflanzenkrankh, 1902, p. 55. 858 autumn transplanting was attended with much greater danger for the twisted specimens. To aid in the removal, the plants were pulled slightly and, in doing so, it became evident that the twisted specimens broke very easily at the first bend in the root. It is, therefore, advisable to cut the seedling tap roots at once at the first transplanting, so that several root branches are formed at the root neck; those near the cut surface develop new lateral axes in the second year. This makes possible not only an increase of the organs of absorption but also causes the production of a root ball in which the earth is held between the numerous roots. Prantl’ first studied thoroughly the anatomical changes which occur when younger roots, especially the germinating ones, are injured. He found in vegetables (peas, horse beans, etc.) that the loss of the tender root tip was completely made good by the development of a new one in which all the tissue systems participated if the injury took place close to the tip of the root. If he cut off the germinating root somewhat further back from the apical cell regeneration took place but all the tissues did not participate in this, only the juvenile vascular strands. The method of cutting, used almost exclusively in general practice, viz: the one injuring the mature tissues, does not bring about a regeneration of the root tip; instead of this, callus formation by the bark body sets in, thereby covering the cut surface. Némec’s? work is even more thorough and comprehensive. In contrast to the assumption that true regenerations, in which the part removed from the individual is directly formed anew in its original shape and with its original physiological peculiarities, rarely occur in the vegetable kingdom, experiments show just the opposite for roots. It is here only a question of injurying the youngest possible organs. In roots, restitution remains limited really to the zone where the cells on the whole wound surface (possibly with the exception of the epidermis and the outermost bark layers) are still meristematic. As soon as the cells of the outermost bark layers, together with the central rows of the sclerome, approach maturity, the meristematic cell layers alone, adjoining the peri- cambium, participate in the regeneration. It is found further that the vege- tative point of a root, of which the meristematic cells externally appear uni- form, still possesses a certain specialization. The cells are not equipotential and can not produce different tissues under arbitrarily changed conditions. Such specific differences are present in the “Statocytes.” The mobility of starch grains in these presupposes specific peculiarities of the protoplasm, since in different callus-like hypertrophied cells starch grains are also formed which at times can be still greater than those of the statocytes and yet, under the influence of gravity, cannot be moved easily. The fact that, under the influence of a sufficiently strong centrifugal force, they can move cen- 1 Prantl, Untersuchungen iiber die Regeneration des Vegetations-punktes an angiospermen Wurzeln. Wirzburg 1873. 2 Nemec, B., Studien iiber die Regeneration. Berlin 1905, Gebr. Borntrager. 859 trifugally, proves that they are, nevertheless, specifically heavier than the cytoplasm. Therefore, the cytoplasm of the statocytes must have less specific weight and must be very fluid, i. e. it must contain very few elements of considerable consistency. Nemec also discovered peculiar cytoplasmic accumulations in the statocytes of the root cap, which certainly represent an especial reaction. If a young root is cut off above its zone of growth and not within it, no regeneration but substitution takes place, for new lateral roots are produced, of which those nearest the wound surface are caused by their geotropic sensitiveness to grow down more perpendicularly than if they had developed from an uninjured main root. This makes possible the utilization of the soil layers for nutrition, which the perpendicular, downward growing main root would have traversed’. A fasciation of the lateral roots takes place at times after injury, or removal of the main root. Lopriore? was able to produce this fasciation artifically. GNARLY OVERGROWTH EDGES. One universal characteristic in the overgrowth of wounds is that the wood fibres do not always parallel throughout the new structure but are often bent and twisted until at times they are looped. These variations in the course of the fibres form what is termed “gnarly wood.” The adjoining figure of the overgrowth cap of an oak*branch, from which the bark has been removed, gives the best insight into this. The oak furnishes especially good examples of a complete closing of large wound surfaces by overgrowth and the luxuriance of the uniting wound edge not infrequently brings about the condition where, for example, in sawed off, larger branches, the newly formed tissue does not have a flat surface but one more or less strongly convex, becoming hemispherical to spherical in form. In such overgrowth caps small centres are often found, the so-called gnarl eyes (Fig. 203, a), around which variously twisted wood fibres (p) are deposited. By the term “snarl eyes,” however, actual buds are not understood but rather depressed tissue centres, around which are deposited the wood fibres in the form of a bowl and later serpentinely twisted; in this way representing the “curly grain” in wood. While a spear-like, woody excrescence appears where actual eyes are produced, in gnarl eyes a deep depression is found formed of parenchymatous tissue, often increased by the rounding up and separation of the cells. Wood is deposited around this depression, normally composed of wood cells, medullary ray cells and vessels. The abnormality lies only in the bowl-like arrangement, recalling the gnarl tuber, and the frequent occurrence of medullary ray structures greatly broadened and resembling medullary spots, which at times can develop into secondary centres. 1 Bruck, W. F., Untersuchungen iiber den Hinfluss von Aussenbedingungen auf die Orientierung von Seitenwurzeln. Zeitsch. f. allgem. Physiologie Vol., III, 1904, Part 4. 2 Lopriore, G., I caratteri anatomici delle radici nastriformi. Roma 1902. Note sulla biologia dei processi di rigenerazione delle cormofite, etc. Atti Acad. Gioenia. Catania 1906, Vol. XXT. 860 We consider the curly or gnarly wood only as an extreme case of per- fectly normal processes, in the variation of the wood fibres when obstacles occur which prevent their longitudinal arrangement in the part of the plant. Such obstacles can differ greatly. Each normal branch insertion becomes the cause of a change in the course of the wood fibres surrounding it. The new formation of wood bodies within the bark, described under bark tubers, represents a further cause. Finally, however, we find the most varied phenomena of arrestment in the formation of an annual ring, produced by differences in tension in the growing axis. Such differences in tension are constantly present and are often strengthened by external influences. Frost action, for example, which causes the formation of parenchyma bands, is Fig. 204. Gnarlly wood structure of the overgrowth cap of the stump of an oak branch. of especial significance. Another external cause is the contact of one branch with another. Besides mechanical pressure, conditions of light are also of influence; they cause variations in the nutrition of the different sides of the cambial ring. Internal processes of growth, as, for example, the rapid outpushing of a suddenly broadened medullary ray, are also of impor- tance. These can distend the bark into knobs, causing a repression in the growth of the adjoining wood layers and the like. All such disturbances must change the pressure conditions which the bark girdle in its entirety exercises on the cambium and will, therefore, influence the development of the wood formed from it. We find in the spiral twisting of the wood body in every trunk, hew greatly the course of the fibres is influenced by the S6I pressure conditions, even in the normal trunk. Our experiments in binding a wire ring around a growing axis prove how much the wood fibres can be forced from a longitudinal into an approximately horizontal position by pressure. It is, therefore, the different pressure constantly endured and exercised by the bark girdle, which conditions the development and course of the wood fibres. Therefore, to explain gnarly wound wood, it is necessary to assume a theory of the polarity of the cells and the displacement of like poles as represented by Voechting and Maule’. BARK TUBERS. In concluding the chapter on the processes of wound healing, we have still to consider the production of spherical woody swellings, or tuberous outgrowths of the bark of trees and (more rarely) herbaceous plants. These structures are generally called “wood tubers” or “gnarl tubers.” Their structure and production differ, thus necessitating a subdivision into separate groups. Their character as correlative hyperplasias is their common quality. They are to be considered as the counteraction of the organism to previous phenomena of arrestment. The arrestment can consist in the cessation of the development of a bud or, independent of any bud, can be produced by the death of scattered tissue groups in the bark. The dying of different cell groups in the bark body of the woody axes occurs extensively. Frost and heat, local increase in pressure and the like, can cduse the death of cell groups without any injury to the whole organism, which responds, not infre- quently, by an increased new formation near the centre of arrestment. The dead tissue groups are sometimes only encysted by cork layers, sometimes also accompanied by cell layers, increasing for some time, or permanently, according to the time and kind of disturbance and the amount of the nutri- tive supply in the surrounding tissue. The cell layers either produce only parenchymatous protuberances or cause the formation of new wood bodies, spherical in arrangement, with gnarled fibres. The. latter process can increase to the production of independent tuberous wood bodies within the bark. I have made no personal study of the first group-of bark tubers, the production of which is traced back to bud primordia retarded in develop- ment, and in consequence will quote the descriptions of earlier authors. Trecul’ should be named first among these. He describes in detail some cases of tuber formation (in the oak and hornbeam) and comes to the con- clusion that the tubers always owe their production to a bud which originally is directly connected vascularly with the wood body of the branch or trunk. Such a bud may lie dormant a number of years without projecting more 1 Maule, C., Der Faserverlauf im Wundholz. Bibliotheca botanica Part 33. Erwin Naegele. Stuttgart 1896. 2 Trécul, Mémoire sur je developement des loupes et des broussins, envisagés au point de vue de l’accroissement en diamétre des arbres dicotyledonés. Annales des scienc, nat. 3 serie. Botanique t. XX, 1853, p. 65. 862 than 2 mm. (at least in the hornbeam) above the surface of the bark. After a few years of such lethargy, the fibro-vascular body can renew its activity and develop into a spherical, oval or even ellipical wood tuber. The death of dormant buds occurs of itself after a considerable number of years, if not hastened by external circumstances, since the connection is broken between the part of the bud lying in the bark and that in the wood body by the interposition of the wood mantle of the branch which bears the bud. The outer part of the bud, covered with scales and lying on top of the bark, remains in place for some time; it dries up very slowly and finally is thrown off. This bud, originally attached to the wood body, can also be loosened by the splitting off of its fibro-vascular bundle from the wood of the trunk. As a rule, the portions of the bud which project above the bark surface die, while its fibro-vascular body, thus isolated in the bark continues to form new wood layers and its own bark without the aid of foliage; it must, therefore, draw its plastic material from the surrounding green bark of the trunk. This growth may continue for years; the outer side of the wood tubers may die from the destruction of external agents and, nevertheless, the tubers can continue to form new wood on the inner side. In the red beech, as in the hornbeam, these tubers are produced from adventitious buds. Th. Hartigt describes the production of tubers in the red beech from preventitious buds. The weak basal buds in the red beech die after possibly twenty years inasmuch as the bud stem, lying in the bark, is separated from the part of the bud in the wood by the interposition of a completely uniform, connected wood layer of the branch bearing the bud. The part of the pre- ventitious bud lying in the bark, however, can remain alive for some time and leading, as it were, a parasitic life, grow by continued, concentric wood formation, into those wood tubers which, as large as peas or hazelnuts, project above the bark and are peculiar to the luxuriantly growing beech trunk in middle age. Dutrochet’, whose personal view is related to the then prevailing bud root theory, describes the tuberous outgrowths as bud embryos (méri- thalles). Unlike the normal buds of the axis, these are not inserted on top of and between each other but remain without any connection with the other bud embryos and their vascular strands and, therefore, do not form a part of the axial cylinder. So long as such an embryo, the primordium of an adventitious bud, remains isolated in the other tissues, it develops no leaf and no bud but retains its spherical form and grows by constantly developing new wood layers, covered with their own bark. If this isolated wood body, the primordium of an adventitious bud, finally comes in contact with the axial body, its own bark disappears because of the pressure and the wood 1 Hartig, Th., Vollstindige Naturgeschichte der forstlichen Kulturpflanzen Deutschlands, p. 176. Berlin 1852. 2 Observations sur la forme primitive des embryons gemmaires des arbres dicotyledonés, 1837. (Nouv. Mém. du Mus. d’Hist. nat. IV). 863 knot forms a real bud, which develops leaves. It now represents a gnarl tuber (loupe); the coalescence of several such tubers forms a wen -(broussin). This theory differs from those developed earlier, inasmuch as in it the bud is considered the final product of the tuber formation, while in the others it is held to be the initial one. Lindley’, who describes the tubers mentioned by Dutrochet in the beech, cedar and poplar and who found in one poplar* that branches could develop from them, considers them to be produced from adventitious buds and cites a further case in old olive trees, mentioned by Manetti. He says that the tubers (gnaurs) in these trees were cut out, together with a part of the bark, and planted and that these tubers, which Manetti called Uovoli, gave young plants. Treviranus, to whom Morren sent some cedar tubers, confirms in general the structure of the tubers described by Dutrochet. He places in the same category the phenomena of the isolated vascular bundles (leaf trace strands) in climbing Sapindaceae, Calycanthus floridus and C. praecox, some Bignoniaceae, ete. Schacht* explains the tubers in the bark of poplars, lindens, beeches, etc., as dwarfed branches which have grown in circumference but not in length. While Hartig points to the first beginnings of the tubers in dormant buds, Ratzeburg* lays stress upon the bark as the productive centre of the same beech tubers and says explicitly that they do not extend to the wood body. Similarly Rossmassler® declares that the tubers of the mountain ash (Sorbus aucuparia), which he investigated, lie only in the bark and have no connection with the wood body; Kotschy*®, on the other hand, describes bark tubers 10 to 15 cm. large on the old trunks of the Lebanon cedar, as gnarly, woody excrescences, firmly fixed in the bark, which are connected with the mother trunk by a few vascular bundles. Masters’ also suspects that some of the tubers (gnaurs or burrs) in the elm, etc., as also in many apple varieties, are only aggregations of adventitious buds. A work by Krick* reconciles the apparently contradictory theories. He has determined that the bark tubers (Sphaeroplasts) of the red beech de- velop in connection with preventitious buds, either separating from the wood axis of the trunk, or developing independently in the bark. In the latter case the tubers have a woody, cork, or phloem core but never real pith. The latter kind of tuber formation which takes place in the bark paren- chyma, outside of the primary group of phloem fibres, carries us over to the second group of bark tubers in which certainly no bud primordia participate. 1 Lindley, Theory of Horticulture 198. Translated by Treviranus 1850, p, 37. 2 Loc. cit., p. 224. 3 Schacht, Der Baum, 18538, p. 134. 4 Ratzeburg, Die iStandortsgewdachse und Unkréuter Deutschlands und der Schweiz. Berlin 1859, p. 243, Note 1. 5 Rossmiassler, Versuch einer anatomischen Charakteristik des Holzkirpers der deutschen Waldbaume. Tharandt. Jahrb. 1847, Vol. IV, p. 208. 6 Kotschy, Reise in den cilicischen Taurus. Gotha 1858, p. 267. 7 Masters, Vegetable Teratology 1869, p. 247. 8 Krick, Fr., Uber die Rindenknollen der Rotbuche. Bibliotheca botanica 1891, Part 25; cit. Bot. Zeit. 1892, p. 401. 864 In this we have to mention first Gernet’s' investigations of tuber formation in Sorbus aucuparia. He found the dead tubers so loosely attached to the bark that they could easily be lifted out with the finger nail while the living ones were apparently firmly fixed in the sapwood. Nevertheless, they proved to be “completely separated from it and appeared as bodies possibly belonging in some way to the phloem because the very reddish color of their smooth under end corresponds to that of the phloem.” Most tubers, when cut through, show several centres about which complete wood layers have developed in 13 to 15 annual layers, provided with vessels and medullary rays and agreeing in their cell structure with the wood of the trunk. The course of the wood layers was gnarly. The annual rings were almost always broader in the under half of the tubers toward the trunk than in the upper one, projecting from the trunk. It was not possible to prove any connection with a bud. Even when a tuber lay near a wen, no connection could be found with any of the many bud cones of the wen. Unfortunately, Gernet had no opportunity to study the initial stages of tuber development; the youngest stages in his material were tubercles 0.5 mm. in size, still completely enclosed in the bark, without having caused any external protuberance. They lay outside the phloem fibre and were spher- ical or ellipsoid and showed several centres about which the wood body had already been deposited. This consisted of parenchymatously formed cells in which a differentiation of medullary ray cells became recognizable in longitudinal sections. The first indications of vessels may be considered to be represented by a few cells with large lumina but still lying above each other with almost horizontal, unbroken walls and containing less starch, or none at all. The farther all these cells lay from the centre, the more clearly noticeable became the lessening of their radii and the lengthening of their tangential axes; their cross section approximated that of summer wood. In older tubercles are found at first sharply differentiated a few pitted vessels and a clearly recognizable central parenchymatous centre, rich in starch. The wood body was surrounded by a cambial zone and its own bark. In the upper half of the tubers, cork formation took place at times in the inner bark. The outer side of this newly produced cork zone was united, not infrequently, with the cork zone-of the trunk. The part of the bark isolated by such a cork zone (Gernet’s “cork dam’’) loses its starch grains, becomes filled with air and dies gradually so that the outer side of the tuber body contains dead tissue. As a rule, the appearance of these cork layers also introduces the death of the tuber, which occurs within the next few years. The under half of such diseased tubers, as well as that of perfectly healthy ones, retains its living bark tissue and the formation of the bark body pro- gresses with that of the wood body. From this we may conclude that the tuber grows downward and thus its upper part gradually projects above the surface of the bark of the trunk by rupturing it. 1 Gernet, C. v., Uber die Rindenknollen von Sorbus aucuparia. Moskau 1860. 865 Judging by this, Gernet arrives at the conclusion that, even if he did not know the initial stages of the tubers, he must still deny any connection between them and the wood body of the trunk and can consider the tubers to be produced neither from preventitious nor adventitious buds. Having investigated the tubers of apple trees, I can confirm absolutely this point of view. For my investigation I had at my disposal tubers vary- ing in size from a millet grain to a pea; they came from the base of the trunk of a young apple tree, possibly eight years old. The tubers lay in the outer bark, from which they could be easily separated. The under side was either completely covered with a smooth bark (Fig. 205, 1 a) or showed a brownish, dry point, without any bark and somewhat depressed (1-k) which was surrounded by a green circular bark wall. Fig. 205, 2 gives the median cross section of the latter kind of tuber. In this we see a median core (2,b) consisting of two phloem fibre groups separated by a little parenchyma; other tubers have only one phloem strand in the core, or two or three isolated cores. Around the bundle are deposited cells, parenchymatous in form, with slightly lignified walls and arranged radially. It is evident that they are formed after the manner of cork cells. At times only a group of thick-walled, brown parenchyma cells, with or without starch or phloem fibres, is found in the centre of the tuber; yet this is a more rare case. Finally, tubers are formed now and then with a small central cavity, filled with the brown remains of cells. The radially arranged, circular zone of lignified, parenchymatous cells passes over gradually into narrow, thick-walled,.somewhat elongated wood parenchyma cells, horizontal or diagonal in course, between which lie scat- tered, short, broad vessels with simple pits (Fig. 205, 2,g). _ These groups are already divided into numerous circles of vascular bundles by approxi- mately cubical medullary rays deposited in one to three rows. The phenomenon begins here which continues in alternative zones out to the periphery of the wood body, viz: that the elements of the one part of the bundle, which lies between two medullary rays, show a course differing from that in the adjacent bundle. While the cells and vessels of the one part seem cut crosswise (2 ”), the fibres of the adjacent part are cut longitudin- ally. This is found in trunks which have overgrown some constriction and may be explained only by the theory that the different parts of the cambium of the wood body, which curves about the core like a shell, are exposed simultaneously to different pressure and strain. Since the young tuber body has no exact spherical form but is only approximately round, the parts. which are to overgrow the corners already formed elongate more in the same length of time. The elements become narrowed, longer and thicker-walled toward the outside of the tuber until they have nearly the length, form and, in places, arrangement of the normal wood body. Inside the tuber, as in the wood, a differentiation of the annual rings into spring and summer wood is found, so that it is evident that the tuber 866 is a wood body, provided with the peculiarities of the species and isolated in the bark; its elements grow in all directions around one or more elongated or short cores. Scat tte nena * ee oe preserrereey (( Ks Y 194, . ie;! LES L/h» wis Fig. 205. Bark tubers from an apple trunk, The cambial zone (2 c), surrounding the wood, annually produces a new bark (2 rs) and, in injuries, heals the wounds just as in a normal trunk. Such an injury has taken place in Fig. 204,2 since the bark and sapwood have been removed from the tip of the tuber by some external influence. In 867 consequence of this a normal overgrowth edge (2 «) completely covered with bark is produced which forms the outwardly noticeable circular wall about the tip of the tuber (Fig. 204, rk). The fact, noticeable at first, that phloem fibres are found in the centre of a wood body, leads to the conclusion that the tissue surrounding the phloem fibre groups is the place where the formation of the wood begins. This conclusion is still more strengthened by the structures near the tubers. Frequently younger phloem bundles are found here, even at times the very youngest ones just appearing from the cambial zone, which are surrounded by peculiar, radially arranged cells (Fig. 204,5). In some cases these plate-like cells of the “phloem circumvallation” turn blue with iodine and sulfuric acid; in most cases, however, they turn yellow. This shows that, as a fact, the tissue surrounding the phloem group tends easily to cell increase. The overgrowth of the phloem by cork tissue is in no way restricted to the tissues surrounding the gnarl tuber. In the trees I have investigated it was found in different places after many an injury. In this, however, the cells always have the character of cork cells and serve excellently to cut off a diseased phloem bundle from the healthy wood. Any one who has worked much with diseased trees knows how sensitive the bark cells are which have apparently so resistant a structure. Their brown color and the more dis- tinct appearance of their layers make it possible to trace the disease deeper into the healthy tissue than can be done in the surrounding bark parenchyma. The overgrowth of the phloem begins, as a rule, in the cells of the phloem sheath and remains limited at times to one side, or at least develops more vigorously on the outerside. Similar phenomena, like the overgrowth of the phloem bundles, are found also in some parts of the parenchyma. Without any reason, known as yet, the parenchyma here substitutes for the core a meristem zone in the bark which increases by growing around the centre of fibres, thus beginning the formation of bark tubers. Such tubers have usually a somewhat regular structure since the course of the tissue elements in several annual rings keeps to the same direction. In a median longitudinal section which may be recognized by the fact that the medullary rays lie in approximately the same plane, the bent vessels are cut through their whole length so that they interrupt the dark, parallel wood cell zones as clear, concentric rings. The drawings (Fig. 206) made from the bark of a healthy one-year-old pear twig give an interesting contribution to the explanation of tuber forma- tion. We see in Fig. 206, 1, the basal part of a very strong one-year-old pear shoot of which the buds (@) are set in the normal two-fifths position ; b is the one-sided swelling in the centre of the internode, reproduced again in cross section in Fig. 206, 5, cut through in the deepest part, which is turned toward the base of the twig, in Fig. 206, 3 in the median region, and in Fig. 206, 4 in the highest zone. In Fig. 206, 3, 4, 5, the same letters indicate the same parts; 7, the bark, g’ and g’, etc., the bark vascular bundles in various 868 stages of development. It is evident that those first formed also become smaller at first after entering the axis. m is the pith; m 5, the pith bridge of a central leaf trace, of which the secondary bundles are unequally devel- oped; mest, medullary rays; hb phloem fibre groups, which compose the central core of the wood cord formed in the bark. In Fig. 206, 4 rt is the bark killed by pressure and pressed into the trunk by the xylem strand formed in the axis of the branch. Fig. 206, 5 g* indicates a xylem strand with the beginnings of overgrowth; this is seen to be more strongly devel- oped on the outer side. Fig. 206, 3 g’ is a xylem strand which has not closed completely into a wood cylinder. Its formation took place as follows: cell increase began on the outer side of the phloem fibre group in the phloem sheath and led to the formation of vascular elements and wood cells. The one-sided wood body thus produced is closed by the gradual union of the two edges, turned to the centre and growing toward each other. Fig. 206, 5 c is the cambial zone of a xylem strand already closed internally but still pressed into a kidney shape at the place of union. Fig. 206,2 gives a part of Fig. 206,3 g’ somewhat magnified. In Fig. 206,2 is seen the complete correspondence with the centre of the gnarled tuber in the apple. hb is the phloem fibre group; p, the wood parenchyma; g, the vessels; +, short, cross-cut wood cells; «’, wood cells, extending horizontally from the inner convexity of the wood cord at the place where the two edges have united; m represents the rows of medullary rays spread out like grasping arms; c, the cambial zone surrounding the strand; 7, the youngest bark parenchyma of the specialized zone of bark. The xylem strands (Fig. 206,5) are, therefore, produced at the base of the swelling by an unusually abundant nutrition of the phloem sheath; their primordia lie at unequal heights. When enlarging, they compress at first the bark tissue (Fig. 206,3) which separates them from each other and finally also the tissue lying above them, which separates them from the axial cylinder and is found later as a brown mass in the centre of the wood body (Fig. 206,4 rt). With their entrance into the axial cylinder, the form of the xylem strands in the bark is changed; the core becomes eccentric and finally pressed back to the tip of the wedge-shaped strand as shown in Fig. 206,4 9’, g°, g*®. The change of form is, therefore, exactly the reverse of that undergone by the normal vascular bundle which enters the bark from the axial cylinder. Farther out the branch becomes normal’. The occurrence of bark-produced wood strands, therefore, explains as follows the production of the gnarl tuber. The mature tuber is a wood sphere isolated in the bark, of which the upper surface is composed of a cambial and bark mantle, receiving its nourishment from the surrounding bark tissue. According to the investigations of the above-named scientists, 1 On the similarity of this formation of the secondary wood with that in the Sapindaceae compare Sorauer, Die Knollenmaser der Kernobstbiume. TLandwirtsch. Versuchsstationen 1878. Fig. 206. Production of isolated wood centres in the bark of a one year old pear branch, 870 which need repeating, the gnarl tubers, or tuber gnarls, can develop from a dormant bud and are, therefore, originally connected with the wood body of the branch. In many cases, however, they are produced as bowl-like wood deposits around a group of phloem fibres, or some other bark tissue group without any connection with the wood cylinder or a bud primordium. _ The tuber is gradually pushed out into the outermost regions of the bark, which is beginning to form the cortex; the longitudinally elongated xylem strands of the bark, related to the tuber formation, can press back into the axial body and become elements of the normal wood cylinder of a branch. External wounds in the tuber body are healed by overgrowth, just as in the normal branch and there is no reason to doubt that adventitious buds can develop from the overgrowth edges as well as from the normal bark of the tuber, as has been stated for the olive. Mention should be made of the fact that the large spherical swellings, produced on oak branches by the overgrowth of places where Loranthus europaeus had grown, have also been termed gnarl tubers or heads. Accord- ing to our division of the subject, these are not actual “gnarls’” but gnarly overgrowth edges. Tine Tammes' describes as abnormal overgrowths the peculiar cone- like processes on Fagus silvatica.which usually grow broader on one side and overlap. Investigation shows that the stump of a branch is involved here, which has been closed by gnarly, hypertrophied wound edges. The hypertrophy has been caused by the severe pruning of the trees on account of which a superabundance of plastic material is deposited at the remaining centres of growth. Peters, in his observations on Helianthus annuus and Polygonum cus- pidatum? gives an example of bark tubers in herbaceous plants. The tubers produced in the middle bark should be considered as the reaction of the plant to wound stimulus. A few cell groups in the bark die and dry up; the cavity thus produced becomes surrounded by a cambial zone which- forms wood on the inner side and bark tissue on the outer. Th. Hartig® mentions examples of tuber formation in roots when describing the fact that young aspens occur in great numbers on cleared tracts where no seed bearing trees had stood for some time. As Th. Hartig explains, the little plants owe their existence to the continued growth of roots left from long dead and outwardly vanished trees. The basis of root growth in these cases is always a tuber-like woody thickening of a weak root strand. The tubers themselves are somewhat like those at the gnarly base of old oaks or lindens and those in the bark of the red beech; they are the woody trunk of a dormant eye which, completely individualized, lives a parasitic life on the root of the parent plant “like the dormant eyes of the American species of pine.” The aspen roots are kept 1 Tine Tammes, Uber eigentumlich gebildete Maserbildungen an Zweigen von Fagus silvatica L. Recueil des travaux bot. Neerl. No, 1. Groningen 1904. 2 Cit. Zeitschr. f. Pflanzenkrankh. 1905, p. 26. 3 OC. elt, Ds 4295 871 alive by these tubers without any growth of the feeding root. As a rule, the piece of root, bearing the tuber, is found to be dead and decaying a few centimeters from the tuber. Andreae’ describes gnarled tubers on the roots of Ailanthus glandulosa; they are produced from roots and from branch primordia. In connection with this, a structure may be mentioned here which is often described as the Club root of beets* but has not yet been sufficiently explained. Usually in dry soil there appears near the crown, or a little farther down, a spherical swelling covered with cork, resembling the root body in structure but differing from it in composition because of.a greater water, ash and protein content. The vascular body shows that the swelling should be considered as the enlargement of a vascular ring of the parent root and may, therefore, be considered an offshoot of it probably caused by an excess of nitrogen after some injury*. The swelling is not parasitic but, because of its porous bark structure and its inert sugar content, is easily infested by animal and vegetable enemies. Lear INJURIES. In consideration of the fact that the results of injuries appear more clearly in leaves and other fleshy parts of plants, we will call attention to the conditions which we call wound stimulus. The first effect of the stimulus, which is exercised on the organ by every injury, may well consist in a traumatropic deposition of protoplasm in the tissue immediately adja- cent to the wound surface. According to Nestler’s* investigations, the protoplasm in the uninjured cells collects on the side toward the wound and somewhat later the nucleus moves toward that side. This action of the stimulus extends a few cell rows into the healthy tissue and after about 48 hours reaches its maximum. After this, a more or less complete return to the normal condition sets in. This change in position seems to take place more quickly in the light. than in the dark. In the same way, the chlorophyll apparatus often undergoes a consid- erable change of position®. In many cases an increase of respiration may be noticed at the same time; in the fleshy parts of plants, especially, a rise in temperature could be proved which has been called fever reaction®. The production of carbon dioxid in wounded leaves is said to be especially in- creased if they are poor in carbon-hydrates*. The reactions set in earlier 1 Andreae, tiber abnorme Wurzelanschwellungen bei Ailanthus glandulosa. Inaugural dissertation. Erlangen 1894, _ 2 Briem, H., Strohmer und Stift, Die Wurzelkropfbildung bei der Zuckerriibe. Osterr. Ungar. Z. f. Zuckerindustrie 1892, Part 2. 3 Geschwin, Le goitre de la betterave. La sucrerie indigéne. Cit. Bot. Centralbl. f. Bakt. Tl, 1905, p. 486. 4 Nestler, A., Uber die durch Wundreiz bewirkten Bewegungserscheinungen des Zellkerns und des Protoplasmas. S. Akad. Wien CVII, I, 1898. 5 Pfeffer, W., Pflanzenphysiologie. 2nd Ed. 1904, Vol. II, p. 819. Here also literature on the action of Wound Stimulus. 6 Richards, Herbert Maule, The evolution of heat by wounded plants. Annals of Bot. XI; cit: Bot. Jahresber. 1897, p. 99. 7 Doroféjew, N., Zur Kenntnis der Atmung verletzter Blatter. Ber. d. Deutsch. Bot. Ges. XX, 1902, p. 396. 872 or later according to the degree of injury. According to Townsend’ the hastening of growth becomes evident in 6 to 24 hours after slight injuries, while severe injuries at first cause an arrestment before the increase in rate begins, which, according to the plant, reaches its maximum in 12 to 96 hours and then gradually returns to the normal condition. Krassnosselsky? traces the increase of respiration to an increase of the respiratory enzyme. He carries out further Kovchoff’s experiments which show that an increase in the whole amount of protein and especially of the nucleo-proteids takes place after an injury and then proves (in injured bulbs) that the sap con- tains more oxydases than does that from uninjured specimens.. The same is true of potatoes. The subsequent reactions of leaves after injury vary greatly according to the species of the plant, the age of the leaf and the time of injury. We 207. Injury to a leaf of Leucojum vernum, which is being closed by callus formation. (After Frank.) will content ourselves with discussing the two extremes, viz: the reaction of a tough leathery leaf and that of a fleshy one. In the former, Prunus Laurocerasus represents a case in which a sloughing process of the injured cell group is connected with the injury as has already been mentioned under the results of spraying with copper. According to Blackman* and Matthaei* either the injured cells alone die, or those immediately adjoining them, according to the part of the leaf injured. A brown zone with a lighter colored centre is produced around the wound. The epidermis splits in this hyaline region and colorless, very thin-walled, cells grow out of the adjoin- 1 Townsend, C. D., The correlation of growth under the influence of injuries; cit. - Bot. Jahresber. 1897, I, p. 98. 2 Krassnosselsky, Bildung der Atmungsenzyme in verletzten Pflanzen. Ber. d. Deutsch. Bot. Ges. 1905, Vol. XXIII, p. 143. 3 Ber. d. Deutsch. Bot. Ges. 19038, p. 165. 4 Blackman, F. F., and Matthaei, G. L., On the reaction of leaves to traumatic stimulation. Ann. Bot. XV; cit. Zeitschr. f. Pflanzenkrankh, 1902, p. 61. 873 ing mesophyll. These form a cuticle and thus represent a complete cover- ing of the wounded leaf surface. When this covering is complete, the dead tissue is thrown off. In this the pressure of moist air is taken for granted. In other cases a normal periderm is formed from several cell layers which suffices as a protection for the healthy leaf tissue. The second case of the healing of leaf injuries, viz: by callus formation, is explained by the accompanying figure. It is the cut wound from a cut on Leucojum vernum. ‘The wound lay in the open space between the two tissues of lamellae f and f;vvvv' are the edges of the wound with the dead pieces of tissue. The wound cavity is now filled by the callus cells devel- oping by elongation from the fresh tissue, which lack chlorophyll and have suberized walls. The normal condition of the leaf is represented at the left side of the figure where 77 indicates a large air chamber; the tissue sur- rounding it has not been changed by wound stimulus. o is the upper and u the under side of the leaf. Many fleshy leaves react according to this scheme, but their processes of healing vary greatly, depending on the subse- quent participation of the process of cork formation. Complete union of the edges of the wound can also take place, as may be observed, for example, in the cut surfaces of fleshy roots and tubers'. The union is sometimes the result of organic coalescence, sometimes only a cementing of the surfaces since the cut cells are changed into a gum-like mass by the swelling and disintegration of their walls. The leaf can under certain circumstances reproduce the part arti- ficially removed (regeneration, according to Kuster) or form a compen- sating organ (restitution?) according to the specific character of the leaf, its youth and its distance from the reserve-substance containers. Frequently whole leaves, or pieces of leaves, removed from the plant, _can form new roots and aérial axes. This capacity is utilized for LEAF CUTTINGS. The best known and most frequent use of leaf propagation is found in begonia culture. According to Hansen*, in the various varieties of Begonia Rex wounds produced by slashing the nerves of the leaf lying flat on the soil are closed at once by callus. In this way: a tuberous tissue is formed on the mother leaf from which tissue, or that immediately sur- rounding it, roots develop; later, sprouts are formed from the same tissue, which, however, do not develop their own roots but are nourished by the above-mentioned roots of the callus. Sprouts develop there from one or a_ few cells of the epidermis near the cut rib, sometimes nearer, sometimes farther from the wound. In such cells, a horizontal partition wall is pro- 1 Figdor, Wilhelm, Studien iiber die Erscheinung der Verwachsung im Planzen- reiche. Sitzungsber. d. Akad. d. Wissensch. Wien; cit. Bot. Zeit. 1891, No. 23. 2 Figdor, Wilhelm, Uber Regeneration der Blattspreite von Scolopendrium. Bericht d. Deutsch. Bot. Ges. 1906, Vol. XXIV, Part 1.—Figdor, Wilhelm, ttber Resti- tutionserscheinungen an Blattern von Gesneriaceen. Jahrb. f. wiss. Bot. 1907, Vol. MLIV, Part 1. -3 Hansen, Ad., Vorliufige Mitteilung. Flora 1879, p. 254. 874 duced at first and gradually by further division the meristem of the young sprout from which a roll differentiates as the first leaf. The roots are formed laterally from a few cells lying near the cambial zone of the vascular bundle. These, therefore, “endogenously” formed roots soon rupture the overlying tissue. As Fr. Regel* states, the roots of begonia branch cuttings can also arise from the inter-fascicular cambium. This author, who has investigated several other begonias beside Begomia Rex with rhizome-like, recumbent petioles, as, for example, Begonia wm- perialis and B. xanthina, mentions that the formation of buds also takes place on the leaf blade near the incisions. After the epidermal cells have divided, the underlying collenchyma and the ground tissue are also drawn into the new formation and help in producing the mound of cicatrization — tissue at the place cut. This tissue differs from that of branch cuttings only in the fact that here the epidermis participates in the cell increase. This activity of the epidermis can become of very especial physiological importance immediately after the cut is made since a few of the upper epi- dermal cells near the wound elongate like hairs (pseudo-root hairs) and, without doubt, develop a root-like activity until the true roots are formed. In the adjoining Fig. 208 are shown the new structures on the cut sur- face of a larger leaf rib in a hybrid Rex begonia. A indicates the old part of the leaf, B the new structures. At first an abundant callus tissue (c) develops from the cut and soon shows an apical growth of its cell rows but indicates by the parallel edges of the cork cells that it is in the process of transition to overgrowth edges. The endogenously formed new root (w) breaks out on the under side of the boundary between the callus and the old leaf tissue, while on the upper side, two new bud primordia have already been formed. The younger one of these shows at d the meristematic tissue of the young bud with the epidermis (e). This meristematic tissue is pro- duced by the division of the original epidermal cells and the sub-epidermal tissue. The second bud has been formed earlier at a point lying farther away from the cut and already is further developed. The real bud cone (d) is already overgrown by a more convex leaf primordium (bl) into which extend young spiral vessels (f). The vascular bundle ring of the older part of the leaf is indicated at g, while ¢ indicates the vascular bundles extending into the new root. Kny? noted that the vascular bundles had become larger on the petioles » of Begonia Rex, on which adventitious sprouts had been produced. The ’ cambium, like the adjacent ground tissue, had continued its cell division, whereby the new walls between the adjacent bundles were predominantly parallel to the outer surface of the petioles. Kny regarded this as the 1 Regel, Fr., Die Vermehrung der Begoniaceen aus ihren Blattern usw. Jena’ische Zeitschr. f. Naturwiss. 1876, p. 477; cit. Bot. Jahresber. 1876, p. 423, 439, 452, ete. 2 Kny, L., ttber die Einschaltung des Blattes in das Verzweigungssystem der Pflanze. From “Naturw. Wochenschrift” 1904; cit. in Bot. Centralbl. (Lotsy) 1904, INOW 5b Os pa iGii2: 875 beginning of an inter-fascicular cambium which, developing further, would have closed the peripheral bundles into a circle. - From the many observations already made on leaf cuttings, the assump- tion is justifiable that the processes described above for begonia may occur also in many other leaf cuttings. The foliage shoots develop from more or less superficial cells ; the root primordia are produced from the cells border- ing the cambial zone and either break through the old tissue of the cuttings or arise from the cicatrization tissue of the wound. Variations in the different genera are usually unimportant and differences of opinion among ~ i ' , ‘ t ' ' ' i 1 ' ' . CR a Ti [ctkters eyes =A * ny is * ray HERE RTE POT reece? Pererety Fig. 208. Leaf. cutting from a hybrid form of Begonia Rex. the various authors are often explained by the fact that individuals of the same plant species under different conditions and of different age do not always show exactly the same processes. Beinling’s' investigations, for example, prove that the genus Peperomia does not form any callus but covers the cut surface with wound cork. He also found buds produced from the ground parenchyma of the petiole, or the blade, but not from the epidermis and always independent of the vascular bundle. On the other 1 Beinling, E., Untersuchungen tiber die Entstehung der adventiven Wurzeln und Laubknospen an _ Blattstecklingen von Peperomia. Inauguraldissertation, Breslau 1878, p. 23. 876 hand, Hansen! describes in detail the processes of root and sprout formation in Achimenes and Peperomia from the callus. In this only the first adven- titious roots are produced from the already existing tissue elements. After the callus tissue had increased for some time numerous pro-cambial strands showed themselves in the callus, extending in all directions toward the surface. Their cells soon changed into tracheae; so that “callus’’* is pro- vided with a branched system of vascular bundles. Soon the peripheral cells of this tissue appear to be abundantly filled with protoplasm; they divide and produce a meristem which differentiates, as do the normal vege- tative points, and soon an epidermis becomes very distinct. In the leaf cuttings of the monocotyledons, the processes of bud forma- tion are the same as those in dicotyledons. Magnus* describes bulb cuttings of hyacinths. Numerous adventitious buds are formed on the ventral side of the cut surface which, in case the bulb scale was still young, are produced from an epidermal cell or in older scale pieces from the underlying paren- chyma. At first tender knobs of tissue are formed from the dividing tissue cells which continue growth at ‘the apex in diverging cell rows; dividing dichotomously. It is, therefore, actual callus. On further developed knobs, a circular wall appears, developing into the first sheath-like scale of the adventitious bud, while the enclosed apical cell shows growth in diverging cell rows. On the bulb scales of Lilium Tigrinum and L. Auratum the buds are also formed on the outer edge of the inner side. The rootlets, arising on the outer side from the phloem region of the vascular bundles, live only a short time since the young plant at once forms independent roots. The processes of bud formation in leaf cuttings do not differ essentially from the voluntary production of the buds on uninjured leaves on the plant. Numerous examples of these are well known‘. They have been observed in mosses and ferns’, in lilies and other monocotyledons, most numerously in dicotyledons. Beijerinck formed as a law for the latter, that the vascular bundles of the leaf have an influence on the primordia of the adventitious 1 Hansen, Ad., Uber Adventivbildungen. Sitzungsber. d. phys.-med. Soc. zu Erlangen vom 14 Juni, 1880; cit. Bot. Centralbl. 1880, p. 1001. 2 Opportunity is here given to call attention to the fact that the authors include two different conditions under the name ‘‘Callus.” They call tissue callus which is produced froms the first cell divisions, and has for some time an arrangement in rows; it continues growth, especially at the apex of the cell rows, and lacks all differentiation. ; In the second place, however, the authors, in accordance with general usage, understand by callus the structure differentiated from the callus by the production of a cork zone, the formation of an inner meristem centre and the separation of a ground tissue. This structure has already become similar to the tissue from the wound in which it is produced. However, the juvenile conditions, distinguished by apical growth, should be distinguished from these mature conditions and I propose, on this account, to apply the term “callus” only to the first structures, while the later stages can be known as “cicatrization tissue.” 3 Magnus, Hyacinthenblaitter als Stecklinge. Sitzungsber. d. Ges. naturforsch. Freunde vom 16 Juli, 1878; cit. Bot. Zeit. 1878, p. 765. 4 Beijerinck, M. W., Over het onstaan van Knoppen en wortels uit bladen. Nederl. Kruidkund. Archief. Serie II, Deel III, p. 488-493; cit. Bot. Centralbl. 1883, Nod Tp ade! . 5 Farlow, Bot. Zeit. 1874, p. 180.—Cramer, Geschlechtslose Vermehrung des Farnprothalliums, namentlich durch Gemmen resp. Konidien. Denkschr. d. Schweiz. Naturforsch. Ges. XXVIII, 1880. 877 organs. The adventitious buds are always found on the upper surface where the woody part of the vascular bundles is turned toward the upper side of the leaf; they are produced in the axes of the ribs and are usually more strongly developed the thicker the vascular bundles. The roots are produced from the phloem side of the vascular bundles. Regel' enumerates the plants on which buds of leaf origin have been observed. A few examples may be named here since the buds develop their own roots after having been carefully removed from the leaf and, therefore, are of importance in propagation. Besides the well known Bryophyllum calycinum, which Berge? studied and on which incisions between two serrations of the leaf develop a meristematic tissue in an early stage and from this meristem buds, the following species are noteworthy: Hyacinthus Pauzolsii, Fritillaria imperialis, Ornithogalum thyrsodies, Drimia, Malaxis, Cardamine, Nasturtium, Brassica oleracea, Ranunculus bulbosus, Chelidonium majus, Levisticum offic., Ultricularia, Begonia quad- ri-color, B. phyllomaniaca*. Hansen* mentions also Hippuris, Elodea canadensis and other water marsh plants. Caspary® mentions Nymphaea micrantha and its hybrids. He also cites examples in which an inflorescence developed instead of a leaf. In this way the upper side of the petiole of a cucumber (Cucumis sativus) was covered with more than 120 staminate blossoms without a single vegetable leaf. The success of propagation by leaf cuttings depends upon the indi- viduality of the leaf as well as upon the plant species. Very young leaves must be excluded because of the immaturity of their tissue systems; very old ones because of their scanty life energy and the ripeness of their chloro- phyll apparatus. According to Lindemuth’s® observations, in genera where the leaves can be used as cuttings, the plants thus produced are on an average stronger than those from wood cuttings. As soon as a leaf has developed a few roots, it may be considered a new individual, even when it is not able to produce shoots. This arises from the capacity of such leaves to live longer than unrooted ones and Goebel’ could also prove an increased growth in thickness (in Bryophyllum). Lindemuth also observed, in a begonia, that a flower shoot can be formed instead of foliage shoots in leaf cuttings. This circumstance might indicate that the leaves furnish different products of assimilation at different ages and places on the axis. Usually the assimilates capacitate the bud, produced on the leaf cutting, to form only foliage shoots. 1 oe. cit., p. 452: 2 Beitrige zur Entwicklungsgeschichte von Bryophyllum calycinum. Ziirich 1877; cit. Bot. Jahresber. IV, p. 423. 3 Mohl, Uber die Cambiumschicht des Stammes der Phanerogamen und ihr Verhiltnis zum Dickenwachstum desselben. Bot. Zeit. 1858, p. 196. 4 Toe, cit.; p. 10027 5 Caspary, Bliitensprosse auf Blattern. Schriften d. phys.-Gkonom. Gesellsch, XV, 1874, p. 99. 6 Lindemuth, H., Weitere Mitteilungen tiber regenerative Wurzel- und Spross- bildung auf Laubblittern (Blattstecklinge). Gartenflora 1903, p. 619. 7 Flora 19038, p. 133. 878 Often, however, they are of a concentration which makes possible the formation of flower. buds. In general practice at times the petiole is used for propagation instead of the leaf, in case the leaf itself is too tender. A recent example is the propagation of the cultivated forms of Begonia semperflorens, which is sold under the name of Gloire de Lorraine and greatly prized as a winter bloomer’. In February the most vigorous leaves are cut off close to the stem and the petiole set 1 to 2 cm. deep in sand and peat mold. At a tem- perature of 18 to 22 degrees C. these petioles form root balls as large as walnuts. Other begonias as, for example, the Rex forms set roots from their petioles but almost never develop strong buds. The petioles of cab- bage, celery and other fleshy plants behave similarly. The flower stems of Primula sinensis may be used successfully as cut- tings. Cramer? used flowers with the leaf-like perianth of this plant, in which buds were produced in the axes of the reproductive leaves. A case, which Baillon observed, showed that the fruit could also be used as cuttings ; in this, roots developed from the fruit of a cactus*. The same author also cut in two just:above the base the ovary of Jussieus salicifolia. This bore two leaflets near the centre, and was cut during and after blossoming in such a way that the ovules could be seen; these cuttings were set in a pot. Three weeks later the well-rooted cuttings were transplanted. A small branch with scales appeared in the angle of the carpels. The upper part of the blossom died and a circular scar was formed*. Irmisch describes root formation on the cotyledons of Bunium creticum and Carum Bulbocasta-_ num’. I have seen root formation in the broken-off cotyledons of beans (Phaseolus vulgaris). Carriere found roots on the fruits of Lilium lanci- folium. Beinling® found flower stems of Echeveria which, in moist sand, had grown roots. — Hildebrand’ describes a fruit of Opuntia Ficus indica out of which a second had sprouted; both fruits after separation from the plant developed leaf sprouts. The same thing happened with blossom buds of Opuntia Raffinesquana. Therefore, each plant organ may be capable of developing leaf sprouts by the formation of adventitious buds, provided first that it contains enough reserve substances to live for some time separated from the parent plant, and secondly that the external conditions are favorable. A summary by Magnus* gives further details together with the theories of Klebs, Goebel and others. / 1 Kirst, Vermehrung der Begonie “Gloire de Lorraine.” Prakt. Ratgeber im Obst- u. Gartenbau 1906, No. 5. 2 Bildungsabweichungen, p. 37. Vegetable Teratologie, p. 160. Bot. Zeit. 1865, p. 527, from Adansonia, Vol. I, p. 181. Flora 1858, p: 32, 42. 6 Beinling, Untersuchungen tiber die Entstehung der adventiven Wurzeln und Laubknospen an Blattstecklingen von Peperomia. Inaug.-Diss. Breslau 1878. 7 Hildebrand, F., Wher Bildung von Laubsprossen aus Bliitensprossen von Opuntia. Ber. d. Deutsch. Bot. Ges. 1888, Vol. VI, p. 109. 8 Magnus, Werner, Regenerationserscheinungen bej Pflanzen. Naturwissensch. Wochenschrift 1906, No. 40. a oe 879 INJURY TO THE FOLIAGE. The results of partial or entire defoliation must naturally become apparent in the amount of dry substance produced. , The effect varies according to the amount and age of the leaves removed and also tke possi- bility of compensation for the lack of foliage by the existing buds and the amount of reserve substances necessary for their unfolding stored in the Eb aicG The annual reports on forestry give sufficient examples for forest trees. It is not necessary to go further into this subject here since each separate case must be judged for itself. In the numerous injuries due to caterpillars, for example, the amount of injury depends upon the time and duration of the eating. Reference should be made, in this connection, to Ratzeburg’. He describes, in detail, the influence of defoliation on the annual ring formation of spruces and pines and treats later of deciduous trees*. Cieslar’s* experiments show that the anatomical structure of a wood ring, produced after extensive defoliation, was changed (it became much more tender). Under certain circumstances the vessels can be entirely lacking* in wood produced after defoliation. Hartig? had already proved that a decrease in number of the vessels goes hand in hand with the decrease of foliage. Kny® had already touched on the subject that under certain cir- cumstances double annual rings can be produced. Wieler’ showed by experiments that the boundaries between spring and summer wood can be entirely effaced by changes in nourishment. Such effects can also occur in fruit trees and often manifest themselves in the yield. In only a few cases can a partial defoliation prove to be advis- able agriculturally as, for example, in grapevines, if they constantly produce new foliage shoots which use up the supply of nutrition necessary for the maturing of the grapes. Among annual and biennial cultivated plants, beets come especially under consideration because, in years when fodder is scarce, the older leaves are broken off in the course of the summer and used to feed the cattle. An example from Bohemia* proves that the root body is thereby forced to form more new foliage than it would otherwise and that the storage of reserve substances suffers from this. It was found here that, after defoliation, not only did the beet root remain smaller but the sugar content was about 10 1 Ratzeburg, Waldverderbnis, I, p. 160, 234, ete. 2 Loe. cit. II, p. 154,.190, 238. 3 Cieslar, A., Uber den Einfluss verschiedenartiger Entnadelung auf Grésse und Form des Zuwachses der Schwarzfohre. Cit. Just’s Jahresber. 1900, II, p. 278. 4 Lutz, K. G., Beitrage zur Physiologie der Holzgewdchse. Ber. D. Bot. Ges. 1895, p. 185. 5 Hartig, R., Uber Dickenwachstum und Jahrringbildung. Cit. Zeitschr. f. Pflanzenkr. 1892, p. 292. , 6 Verhandl. d. Bot. V. d. Prov. Brandenburg 1879. 7 Wieler, A., Uber Beziehungen zwischen dem sekundiiren Dickenwachstum und den Ernahrungsverhaltnissen der Baume. Tharander forstl. Jahrb. 1892, V. 42. 8 Blatter f. Zuckerriibenbau. 1905, No. 20. 880 per cent. less than in the undisturbed beets. Aderhold’s* experiments with roots and grain gave similar results. It was found in grain that the length of the heads was strongly affected, irrespective of the reduction of the whole harvest. Nevertheless, one’s fears should not carry one too far, nor should slight losses of leaf substances be considered of too great importance as has recently been estimated by many pathologists in judging the injury due to fungi. It must not be forgotten that the parts of still vigorously growing leaves, which have lost some of their lamina, are excited to increased effort, as I have proved experimentally*. Boirivant* found, in fact, that after the removal of leaf blades the petioles and stems participate to a greater degree than usual in the assimilation and that their parenchymatous tissue can begin to elongate and increase. 1 Aderhold, R., Uber die durch teilweise Zerst6rung des Blattwerkes der Pflanze zugefiigten Schiden. Prakt. Blatter f. Pflanzenbau u. Pflanzenschutz. III Jahrg. 1905, Part 2. 2 Sorauer, P. Studien iiber Verdunstung. Forsch. a. d. Gebiete der Agrikultur- physik. Vol. III, Part 4-5, p. 109. 3 Boirivant, A., Sur les tissu assimilateur des tiges privées de feuilles. Just’s Bot. Jahresb. 1898, II, p. 231. SUPPLEMENT. Page 307. New investigations on Chlorosis have been published by Molz (Die Chlorose der Reben, Jena 1907, G. Fischer). In confirmation of the theory, which we have expressed, a lack of oxygen for the roots may actually be considered as the cause. On this account low positions, where water flowing from higher ground can collect, are the most dangerous. In heavy soils the development of the root system suffers from this. Lime itself cannot produce chlorosis but soils ‘rich in lime cause especially the death of the roots, since they are often very fine grained and can produce an alkaline reaction. Therefore, we may speak of a calcium chlorosis. Con- tinued drought, as well as cold, can also produce chlorosis. Worth consid- eration is Molz’s theory that the weak constitution of a chlorotic plant can be carried over by the wood used for propagation. The disease can either be inherent in the cuttings from the beginning, or “certain disadvantageous circumstances from outside, resulting from an inherited, strong predisposi- tion, can cause the production of the icteric phenomenon and its results.” A permanent cure cannot be brought about by.iron sulfate. At best only the symptoms will be removed and it is probable that the greening of the leaves is not caused by the iron but by the sulfuric acid. Page 335. Molz studied dropsy in grape cuttings (Bericht der Kgl. Lehranstalt zu Geisenheim a. Rhein, 1906). The cuttings had stood for some time in damp soil. They were swollen up like clubs in different places, thus splitting lengthwise the outermost tissue layers. A white, spongy tissue became visible in the gaping wound, which consisted of hypertrophied bark cells. Molz considers the disease, which is not uncommon in moist vine- yards, to be identical with that in Ribes aureum described by Sorauer. Page 345. Black specks are found in the one-year-old shoots of Vitis vinifera and appear somewhat raised. Molz (Centralblatt f. Bakt. II, Vol. XX, 1908, Nos. 8 und g) describes these as small, round knobs of a blunt, conical form (“bark warts’), which may be considered as a compensation for the lenticles not found in Vitis vinifera. Each one has a stoma on its tip which dries up rather early. This drying extends to the neighboring cell groups and advances until halted by the formation of a protecting cork layer. The stronger and better nourished the tissue is the more quickly the 882 protecting cork is produced. Poorly nourished shoots produce no protect- ing cork and on this account bear especially large and numerous bark warts. » These black specks, therefore, furnish a standard for judging the degree of maturity of the wood and the health of the vine. The more numerous and the larger they are, the less mature in general is the wood. Page 378. In Geisenheim, Julie Jager observed a wen formation of the apple tree (Zeitschr. f. Pflanzenkrankh. 1908). The cause has not been sufficiently determined, but is probably to be found in some disturbance of nutrition, which manifests itself in the widening of the medullary rays. Some medullary rays in their primordia show a greater cell increase and widening of the individual cells. The process is connected with the forma- tion of gnarl spikes from the medullary excrescences in Ribes nigrum and Pirus malus chinensis, which we have described. Pages 391 and 395. The iron spotted condition of potatoes was unusu- ally wide-spread in the wet year of 1907 and connected with it appeared a yellow to brown discoloration in the vascular bundle ring. This discolor- ation, in common with a frequent diseasing of the stem end, in which at times a Fusarium was concerned, has influenced Appel to explain the so-called leaf roll disease, a form of the curling disease, as a fungus epi- demic. Appel maintains that the Fusarium, found at the stem end, grew during the winter through the vascular bundle ring into the eyes of the tuber and caused the following year.an increased occurrence of the disease and a gradual destruction of the potatoes. The same theory has been advanced by Reinke and Hallier, only they have made another fungus responsible for it. Sorauer proves (Internationaler phytopathol. Dienst, Stuck 2, 1908) that the Fusarium, to be sure, may be found frequently but that other slime fungi appear just as often; that all fungi could never be observed to be growing in the vascular bundle ring of the tuber up to the eyes. It is not a question of a fungous disease and its continuance through the tubers into the following year. The phenomena of discoloration in the tuber may rather be explained by the increase of the enzymes which Prof. Gruss has proved to have accumulated especially about the stem end. Con- sequently, a relatively larger amount of sugar would be present, which would form an especially favorable substratum for numerous micro- organisms. Page 496. The influence of electricity on plant growth was tested at the Hatch Experiment Station of the Massachusetts Agricultural College (cit. Z. f. Pflanzenkrankh. 1908). Raphanus sativus was used as the experi- mental plant. It showed a hastening of the rate of growth and an increase in weight of foliage and roots; the leaves, however, were a lighter green and were inclined to leaf blight. The electric stimulus seems to act on the organs in the same way as does a lack of light. Gassner (Berichte d. D. Bot. Ges., 1907, Part 1) can confirm the results of Lowenherz’s experiments mentioned in the text. The curvature produced 883 by the action of the current, which could be observed in all plants, did not always remain the same. At times it was toward the negative pole; in other cases, toward the positive pole. In opposition to the cultural experiments with barley, published earlier by Lowenherz and confirmed later by Gassner, which prove an injurious effect of the electric current, the first pamed author now reports favorable results (Z. f. Pflanzenkrankh. 1908, Part 1). With a weaker current he found a hastening of the growth of a seedling; the injurious action began only with an increase of the current. Page 524. In the reports of the Hatch Experiment Station of the Massachusetts Agricultural College (cit. Z. f. Pflanzenkrankh. 1908) may be found observations on the leaf blight. of conifers and other evergreen trees as the result of winter and spring frosts. The trees show the blight usually only on one side, which corresponds to the prevailing direction of the wind. If dry winds blow with a high temperature at a time when the soil is still frozen, the plants cannot find sufficient compensation in the frozen soil for the inereased transpiration and the leaves dry up. This is . the same theory which found expression earlier as explanation for the drop- ping of pine needles. The native conifers suffered less, in case they did not stand on unfavorable soil, when compared with the imported varieties of Picea, Abies, Juniperus, Taxus, Buxus, etc. Page 675. According to Stocklasa’s investigations, Ueber die glykoly- tischen Enzyme in Pflanzenorganismus, Z. f. physiol. Chemie, Vols. 50 and 51, 1907, the anaérobic respiration is an alcoholic fermentation in which a certain amount of lactic acid has formed together with alcohol and carbon dioxid. This holds good also for frozen organs (beets, potatoes, etc.). Zymases and lactacidases are, therefore, not destroyed by the freezing. Lactic acid, alcohol, carbon dioxid, acetic and formic acid are also formed by enzymes in living plant and animal cells. The decomposition of the hexoses by glycolytic enzymes is normally completed without the codper- ation of bacteria. In the precipitates procured from pure plant juices by absolute alcohol and ether, the author found fermentation enzymes which produced a lactic acid and alcohol fermentation in the glycose solution; in this process with easy access of oxygen definite amounts of acetic and formic acid are always formed. Page 677. Fallada’s investigations (Oesterr. Ungar. Zeitschr. f. Zucherindustrie u. Landw. Part V, 1907) on the white leaf conditions of beets favor the theory that the white parts of the leaf remain in a younger developmental stage and with a scantier cell content and are more suscep- tible to the influence of light and heat than are the green organs. The etiolated leaves had a greater water content; the smaller amount of organic substances gave a relative increase of protein especially of the non-albu- minous nitrogen compounds. The potassium and phosphoric content was greater; the calcium and silicic acid content was smaller. 884 Page 717. For the diseases of the horseradish, we have referred to our detailed article in the Zeitschrift fir Pflanzenkrankheiten, 1899, p. 132. It is stated there, “The forms of disease mentioned appear to me on this account only as a great increase of a wide-spread tendency to gunimy degeneration . . . because in the production of the masses filling the vessels the liquification of the secondary membranes cooperates in certain cases.’ This theory has been shared recently by A. Schleyer (Dér Anbau des Merrettichs usw. cit. Biedermanns Zentralbl. f. Agrik., Part 8, 1908). He says, “In my opinion, the turning black is conditioned by the fact that the Pentosane and the sugar in the horseradish degenerates into gum.” Experiments also confirm the theory that lime should be used as a remedy (since humic acid is often present in the soil). When the plants were cultivated in nutrient solutions, some of which were made up with calcium, others without it, the gummy degeneration of “the sugar’ could be proved very soon in the plants which did not have calcium. Page 718. The subject of the injuries due to the gases of smoke and other industrial waste substances is beginning to be separated as a special branch of general pathology and is represented by a special publication. Since 1908, there has existed the “Sammlung von Abhandlungen tber Abgase und Rauchschaden” edited by Prof. Dr. Wislicenus, who has already given in the first part a comprehensive description “Ueber die Grundlagen technischer und gesetzlicher Massnahmen gegen Rauchschaden.” Recent investigations by Haselhoff (Z. f. Pflanzenkrankh. 1908) treat of the action of sulfurous acid on soil. The experiments show that vege- tation is not injured if the soil contains such amounts of decomposable bases (especially calcium) that the sulfuric acid, formed from the supplied acid, is combined. . The case described by Wieler of soil impoverishment in the presence of free acids in the soil may be found very rarely (perhaps in forest soils). If, on the other hand, sulfurous acid is introduced into the soil during the growth of the plants so that it shows an acid condition, dis- turbances in growth become clearly noticeable. In soils containing copper, the copper is carried over into easily soluble compounds of the sulfurous acid and this dissolved copper can then become injurious to vegetation. But even here calcium carbonate helps since it arrests the dissolving action of the acid. Page 761. The occurrence of a disadvantageous effect of Bordeaux solution on the yield, which we first observed, has been confirmed by recent experiments of v. Kirchner (Z. f. Pflankrank., Part II, 1908). The author takes the older literature also into consideration. Probably the shading action of the solution should be made responsible for the lessened yield. This would explain also the rapid turning.green of leaves with strong illumination. The greater amount of starch is not to be ascribed to increased assimulation but to a decreased removal of the assimilates. 885 Page 765. Kelhofer (Internat. phytopath. Dinest, 1908, Part 3) has reported some points in regard to the making of Bordeaux Mixture. The effectiveness of the mixture depends not only on the quality of the materials used but also on the proportionate amounts of the two elements and on the method of preparation. In regard to the proportionate amounts, it should be emphasized that the copper precipitate loses its physical properties the more quickly and the danger of washing away by rain is the greater the more calcium is used in preparing the solution. According to Kelhofer’s experiments, it is further desirable that the copper vitriol solution and the lime milk are mixed when cool and in the most dilute condition possible and, on this. account, the copper ‘solution must be poured slowly into the lime milk; otherwise the precipitate assumes a powdery form which conglobates. Although the addition of sugar is to be recommended in general, care must be taken not to use too large amounts since the copper solution thereby may be more easily washed away. At any rate the amount of sugar necessary to make the mixture keep depends upon the amount of calcium, inasmuch as solu- tions prepared with a good deal of calcium need more sugar. Thus, for example, when using I, 2 and 3 kg. calcium, to 2 kg. vitriol to each 100 liters of water, 20, 30 or 40 gr. of sugar have been found necessary in order to protect the copper precipitate permanently from decomposition, i. e. for at least a year. In common usage, where, as a rule, plenty of calcium is used, it is advisable to take on an average 50 gr. sugar for each hektoliter. With this addition the whole amount of Bordeaux mixture needed can be pre- pared at the same time in the spring at the beginning of the season; the . mixture will then keep through the summer. Page 772. The investigations of Rudolph Friedrich (Ueber die Stoff- wechselvorgange der Verletzung von Pflanzen. Centralbl. f. Bakteriologie, etc. II, Vol. XXI, p. 330) have confirmed the observations of Zaleski and Hettinger that an increase of protein takes place at the wounded place. Besides this, however, Friedrich found that in the storage organs beneath the soil, as well as in the fruits and leaves, a decrease of carbo-hydrates and an increase of acidity (with the exception of bulbs) sets in as a com- mon, secondary phenomenon of the injury. If, with Ad. Mayer, the acids are considered as the products of oxidation of the sugars, then the increased acidity is explained by the more active respiratory need of the injured organ. The decrease of carbo-hydrates will be explained partially by the fact that they are used for protein synthesis. A corresponding decrease of amids or the amido acids may be considered as further reactions to trau- matic stimulus. These substances are used in the construction of the protein molecule. In the potato the smallest starch grains are used up and intro- duce the formation of sugar. Page 787. Hedrick, Taylor and Wellington made girdling experi- ments on tomatoes and chrysanthemums (Bulletin 288 of the Agriculture 886 Experiment Station at Geneva). No beneficial effects could be determined. On the contrary, the plants were very evidently injured. Knobby swellings were formed on the axes; the leaves became sickly and the root system less developed. A confirmation of my personal studies on the processes after girdling may be found in Krieg’s contributions on callus and wound wood formation in girdled branches and their histological changes (Beitrage zur Kallus- und Wundholzbildung geringelter Zweige und deren histologische Veranderun- gen. Wurzburg 1908, Nubers Verl.). The observations on Vitis are new in that the formation of new structures as a result of girdling were proved in the pith, although the pith had not been injured at all. This fact is important because it shows that the wound stimulus, or the changes in tissue tension setting in after each injury, manifests itself in regions far distant from the wound surface and separated from it by firm wood zones. This makes better understandable the changes in the pith body due to frost injuries in which the wood ring shows no disturbances of any kind. The formation of wound wood in the pith of Vitis was observed by Krieg, who ascribes it to the action of the products of decomposition of the woody part killed by the girdling. This wound wood consisted of parenchy- matous aggregations resembling pith spots. These were enclosed by a ring of cambium. The ring lying within the pith bark developed wood with numerous vessels toward the inside and sieve tubes toward the outside. The’ other pith spot, adjacent to the pith crown, formed the sieve tubes from its cambial ring toward the inside and wood toward the outside. The corre- sponding parts of both new structures united later with the respective parts of the overgrowth edge. In the meantime, the plant had replaced the wood already killed in girdling by the formation of new wood and sieve tissue in the pith. Page 825. We owe varied and careful experiments to Elsie Kupfer (Studies in Plant Regeneration. Dissertation of Columbia University, New York, 1907). Of these, we will emphasize first the experiments on root cuttings of Roripa Armoracia. Pieces of the root laid flat in the soil formed new shoots from the cambium of both the upper and under cut surfaces. If bark and cambium had been cut away, sprouts developed after a preliminary callus formation at different places near the vascular bundle and more abundantly at the upper than on the under end. The capacity to form sprouts, which otherwise is peculiar to the cambium, therefore, extends in this case to the callus tissue newly produced as a reaction to wound stimulus. Longitudinal sections of roots of Pastinaca sativa, which were laid hori- zontal in sand, developed new sprouts on both cut surfaces near the cam- bium. In isolated pieces of bark, sprouts were produced on the inner side and roots on the outer side. The isolated central cylinder formed only roots. The experiments with potatoes are very instructive. If any eye at all was left uninjured on some aerial shoot, this developed an aérial tuber. If 887 all the eyes were removed, only root formation took place. Pieces of potato tubers, from which the eyes had been cut out together with the adjoining tuber parenchyma, formed new eyes on these cut surfaces. In the potato leaves, either a simple formation of roots appears at the under end of the petiole or a tuber swelling, containing starch, or a combination of the two, or a regular small tuber with eyes. As a total result of all the experiments for which blossom and fruit stems were also used with success, we may recognize that for regeneration the presence of an abundant reserve material is necessary. Pure white sprouts of different plants formed no roots. Darkening, or removal of the carbon dioxid, prevented regeneration. Since certain parts of the plant are not capable of regenerating one or another organ, even when all conditions are favorable, one is led to the point of view that different substances must be present which determine the formation of any certain organ, Such sub- stances should be thought of in the form of enzymes, which are not present in all cells but are localized in definite parts of the plant body. Page 833. In regard to callus formation, which takes place between the bark shield and stock, Ohlmann expresses himself in his detailed work (Ueber die Art und das Zustandekommen der Verwachsung zweier Pfropfsymbionten. Centralbl. f. Bakteriol. usw. II, Vol. XXI 1908) as follows: “It seems, therefore, that callus formation may begin only at the bark shield. Sorauer states in regard to this question that no law for the tearing away of the bark may be determined. According to Schmitt- henner, the trunk splits in the youngest sapwood. I have investigated a great number of plants of widely different species in regard to this ques- tion. It was evident that the cambium remained intact on the bark. In more scattered cases, I noticed that a few cambial cells had remained hanging to the youngest wood. Nevertheless, I have noticed this so rarely that I cannot ascribe any significance to it.” It should be remarked here that the author did the budding at a time “when the cambial activity was in full progress.” In this case, the author was correct. If the budding is done later, however, then the cases observed by Sorauer become more numerous. Page 854. Blankinship describes a bleeding disease occurring fre- quently in Montana (North America) in Populus augustifolia, P. bal- samifera, P. deltoides, etc. (Zeitschr. f. Pflanzenkh., Part 1, 1908). The trees bled extremely from wounds and this was accompanied by the bleach- ing or yellowing of the foliage. At times the wounds on different axes developed into cavities filled with a gummy, half fluid mass. The exuding sap, laden with bacteria, had a sweetish taste and had often attracted large brown ants. A “Jaundice” of the poplar is connected with this bleeding disease, in which bleeding may also appear but more frequently does not. The foliage of the whole tree is bleached and dries up in the intercostal fields. Death 888 follows after 3 to 5 years. The diseased trees stand generally in low places and the author is of the opinion that the increase of the alkali content in the ground water is to blame. This trouble is found in Montana not simply on poplars but also on other trees avhere irrigation is used. Drainage is advisable. Page 856. Minora Shiga (On the effect of a partial removal of roots and leaves upon the development of flowers. Journ. College of Science, Tokyo, 1907, Vol. XXIII, Art. 4), reports on the promotion of blossom development by the removal of the part of the roots. Different species of very different plants experimented on acted differently under the same manipulation. In Pharbitis, Pisum arvense and Vicia Faba the removal of the main root and small lateral roots cause an unusually early and luxuriant development of the blossoms. This was not the case in Fagopyrum. Cutting off of the side roots promoted the formation of blossoms in Vicia Faba and Pisum sativum var. arvense, but did not do so in Pisum Arvense. End of Volt. 889 INDEX TO VOLUME I. Of the numerous plant names cited in this volume, only those are included in the index of which detailed accounts have been given. To have named all the plants used as examples for certain cases of disease would have uselessly encumbered the index. INDGISSTOMMO EWISS 4 ans oe cie cose kere 357-60 INITIES SH Ge eee anf Bele er Barer tne Nera Ara 105 Aplactationy 1m erate, ci qe sane eee 831 ANencias Eexudationon eutite. ss. o)-2 4. 707-8 Acacia longifolia, with intumescence.. .437 — Microbotrya, with intumescence. . .437 — pendula, with intumescence........443 ANcchimatizationes pacmeer emer: cee aioe ss 40 TOA agre es che hg teh PA NO oo en ot anc ee Seep 04 Acer. Defoliation due to heat......... 4II Acer campestre. Goitre gnarl ......... 27 A MOLI LUN ce aicge S cmotols OOEES Cate Oe 160 —:Negundo. Discoloration ......... 280 = SALA QUCILDS Meo oo ENCORE RR 160 — palmatum. Nanism .............. 144 — plantanoides. Discoloration.......2&0 — Pseudoplantanus, var. Schwedleri. Discoloration; seuaness a eee oe 280 PNG Oty OTe ty ystterctorccsscstioal aeele lola eyerked 744-47, 760 Ncetylene spoisominge 2. jaeens ccs os 740 Acid content. Changes due to lack of EI Nk, S coed Sooo ia lc ain ie Seen 668 NGI Sminias Oller cient eevee otek 240-AI — of plant roots. Effect of neutrali- ZABNUNONG), wep eo PED Gans LOCI ea TE ee ene 402 WA\Gie@aniaiibicol) aoa AE ome eee on eeeecrao ae 204 Acremonium in sterile-head condition. .544 PNCLOGWIIMCIGIUIME cies 42 ac Sos craeiion se 204 ENG CO NSRITEINN” gg Boe Oot o Geer 54 JANG RTOIIL KONI ADOKE. YONI Renee ole oe cose clo aa ao 241 TENGE UANEIS) 9... & 6 eo Bors ce ey cee a RRR ore eet 154 Aesculus, MOACrOSIACNNG ... 22.22 5.0.4 02 105 JNSRNCISbIG CMa aa Cues cree rete 53 GERICUSHCOIND CSIFUS onan 8 cals bass aula 909 ENG AiO Stil Uekecya chimes Warmers erage aie woven olasersit 134 /NCASIPEM BDI IAY Ure roe tee teers cara ceo Reet Ge 147 Agnognium repens 2. By s..0.2..80500. go AlgGnostemunid (GiuhOGO) qa. 02-2020 s+. oe 74 PNileimtlatisis. cep eeaeetet ye a eycitenia ie elas ee 102 Nimes DUNES, SIDI GREICte | eee ee cig cae eee oe 314 — Moist. Effect.on plants injured by GROMGtaaeaee eee hei a oye, fos seeps od 42 = OOM, Wu EC CLM eI ie: ansicnsl ers 408-22 Akrolerma slniiitihiya dtles FOr oe. ane stele oe 757 NIbICaplonen rome ety ae. Sarai: Che) eatin 308 /NIl|YbaVSION Mepemiotie arcs oder 36, 677-84, 608, 847 Alder bogs. Discoloration of water....251 Aldencis ld cathitnss erase couch ciara: 153 Algae, Green, as nitrogen collectors....273 NC Tita Tease cnet epee ae ce etna caste Site toenail ess 270 Nil Feciliieren cracks pyr eae ee eM One WR a ant 195 SS OL Stet a WAR ceca er deren sie onsie heen 267 Mikalsnttar of ther soil Sn pears Megas: 367 Allentospora radicicola, Wakker ....... 227 Auli wS GAG, sce eles aa een 30 ALMA GUEVMOSOE cee aches coer ee 98 = == JPISCIRIEOM Sogo F36a00c00n L.Goe. 333 AMONG. WUWSCOTIG 325 acrsnues eee maura cielo 288 ZANSTDUOULON TU Dh ean Ce sie rsnicic Pn PSone 730-32 Combination: <:-2seee272 Ammonia, Free. Fe Use as top dressing.268 Ammonium salts. — — Use on meadows.............. 363 SS UUALE) Bh siarsientis enh. +1 sure eeeirerere te aetna rake 769 Ampelopsis hederacea. Emergences....440 Amygdalus Persica. Nanism ......... 144 ANaiylOcanbolh, sis swiss oo: we cele See ee 760 Ata Dati aly ates, snes cons 168-70 =~ (Carl arr el Meena et omen cee 586-92 — (IPS aIS GhIG\ IG eorat oa aeRenemeto NS re cero 210-13. =e VatletiesmlObedhy uSOllse aera 175, = Wrater-cOLe. sags sisj..6 «2.1 AS ee 286-87 ——s Vier ehOTMMmatlOny amiss