a \ : em i aN _——< A) ie a = aoe Y at = : . e RTE vt FN Ricco 4 A = 3 1 Ap : - IDAZSEeSTt ay H Dl Bi ] |= 12 = > : Uv ids sanity, WOT th SE IRAN i < ry, Py, mA =e» pei nest Gel oo i ieee ak Si eer Se als MEMOIRS OF THE New YorRK BOTANICAL GARDEN Wor. E. “THE INFLUENCE OF LIGHT AND DARKNESS UPON GROWTH AND DEVELOPMENT BY DANIEL TREMBLY MACDOUGAL, Pu.D. ISSUED JAN. 20, 1908 MEMOIRS OF THE New YORK BOTANICAL GARDEN Vite ieee fie INELUENCE OF LIGHT AND DARKNESS UPON GROWTH AND DEVELOPMENT BY DANIEL TREMBLY MACDOUGAL, Pu.D. LIBRARY NEW YORK BOTANICAL GARDEN ISSUED JAN. 20, 1908 THE INFLUENCE LIGHT AND DARKNESS UPON GROWTH AND DEVELOPMENT BY DANIEL TREMBLY MACDOUGAL, Pu.D. LIBRARY NEW YORK BOTANICAL GARDEN PUBLISHED BY THE AID OF THE Davip Lypic Funp BEQUEATHED BY CHARLES P. DALY. NEW YORK 1908 PREFACE. The results described in the following pages were obtained by a series of experimental observations begun in 1895 and continued until the close of the year 1902. Originally designed to analyze the phenomena of etiolation, the work has naturally led to a consider- ation of the more general relations of the plant to light, and it is believed that some important additions to the knowledge of the sub- ject have been made. The chief results of value have been obtained by long continued confinement of the etiolating plants in dark cham- bers from which light was entirely excluded. The author has received material assistance from his students and colleagues during the seven years over which the investigations extended. The description of the etiolation of Ovalis and Sarrace- nia purpurea is largely drawn from examinations of etiolated speci- mens made by Mr. Wm. B. Stewart. A number of botanists have rendered notable aid in the interpretation of some of the morpho- - logical facts presented. The illustrations are from drawings made from the actual objects or photographs, by Miss Alexandrina Taylor and Mr. \ August Mariolle. D. T. MacDoueGAat. New YorK BoTANICAL GARDEN, Jan. 10, 1903. TABLE OF ‘CONTENTS: THE INFLUENCE OF LIGHT AND DARKNESS UPON GROWTH AND DEVELOPMENT. HISTORICAL. RECORD OF INVESTIGATIONS. PAGE. RSM MSR ce oa. o hg o's dininicia a's 2 wa ve ale oh ae Sion oes wos eenO Se Settee ee I PR RMD fein ces es aes 5-5 5.aite soni ielc de'nceeas olds Gulelew «Moe see eee I HepB es AN one inc Ne Sc ccc eas vis'es Wc wen a’de'v se'tins ¢ cin clad a eslnn apie gee eee I AME CON Nee es cg x oles yalhus wenn < Gi ews cu cnwent Se does Spee See I OR eat IN GIO AS ON eae Sef e siesta v viens ow dased wo sed burs 4 cy Hsin eee eee 2 SITE WEAN (Sk 010.0) Bang ED ORERAEE « SSM R SRR ec 2 leet ep ere aoe eons fi hb cae coh sge ss ee cca oe eave ts oto aaleeeeememne 2 Dea a eT Dy he tee cy nae dso ois tn vee ene’ Men ts pao s SR SE 3 Wet aaaover vn a (LOO, 1032)... sci ..socanenecb eden vara davash quewenmemes ce ME sol gence are ere AS nae vin-c fc Galeeioe dened ovieteld nce sap xewhos aodenonbeeee a pve Fee iraM ANS et cance. fc). «+ 2sadbate.<5s vcaess sh asst eo ssesdas Sacer eeeeen 4 ER RBar reve reese oats dts cdyeaianls oanammicuves no, Gude sch tner gee 4 RIS AME OI oe rd So Suche ave cretoe vcauindue deve nek ongeuang wane tee ceMeeaenen 4 Ayo et Pee accor ots ec al sin v= cine Vu wn Ke wo eye o's dale olde a sito s abelee ee 4 eR os EN A ape ci ienias odin ep naicione ie ciecco Ss} nde cing etna wnt ehidele oes canoe meee 4 LRGET SS 20) OP G8 eer epee Perce rcs se ence 5 IVS APN TN Eps Seis oe ce ein kei dc ae'eleo'es don wa 0's o/isinf erode olden alee pleemnaier 5 PRs RIED CPO Pl gets coco revacisca var s'dsecoaase-sle ders tenanen weltel ta eaaaag 5 ee ese AMON een one neers ovo:0,00'0 oC Se 9 se ot ae @awena ou du as admebpangeasen 5 ato did PIE AC RM) et ayer ca oa se fale ws ocslein aie «ac dup She iwele’mnws sWiees salpemee gee 5 SME ROAR Poon coc. 0 22 sean cweaseeosseéaecnes) ones sepckaeewenatynenpars 5 Welhaty Gis6s).<......-2.+5 ee PRR eet ees ORR ote PR Onto 5 ee MESA P a ech eee yc a a ocds v asinine soos Gans vesbaqgneunbewatacuanmnagieaae 5 WeATMISE RISA AN) Oh concede ce snac as week ni s'ch asada ssn cesietk cd aegev ta aicwans 6 eae ROA ee ae cne conn tye stweeccsacie sees a ammtsmnsiedessnionaremalcamen 6 MORRIE BOND locos se atts chenecs “aewelcs-copa vaenentoesnwseeiiem od sins oweeua’ss 6 REE PERCE TOMO Yo oe cave ase isc0s 00 ae -cnevasseacwevsanagsorsntanetmesarananiee 6 Paces age OE) ae cis caries So nnn oak vecieeeaies9 «heed aan clerbantnnaeslace ties 6 RMS TANIU DOGG) one oo sadnnvnvns nc suececnessnnasactsseceshacneseasaeceanssceree 7 Ae ia a celes ciceweerw egal asisindactsogenso= sec reeeennsainser’ tects | viii CONTENTS. Sachs (1859, 1862, 1863, 1864, 1865, 1872, 1887, 1892) ws... a Kraus'G..( 1869, 1870, 188%, 1004) 25, secseeen seine. fees Ii, te Batalin: ( 1860, 1572), \...2cccaciecs set eew coeeaee arene eens eee races oe 12,33 Weiss (1865, 1866) 5.24 s.c.ncssaugenany-tared east tier ay tee eee ioe tna 13 Famintzin (1865, 1867)............. Peter ea i a ino ee 13 Karsten, Hi. (1970) i05-/csie's sions een tee ee ee ine elon ere sae i Pratt) (0873). 5<0-02-5 capgad aipactontactete mete bang het wo ee ce IEE Pat 13 Godlewsky (1873 )..2.-s0-cascesessensenee Nae Sure TE hie Renu he's settee 14 Detmer (1880, 1082) oes cmnenenusk obecsseanssaiasesn ees cet reds s raaan none 14 Lasarefll (1874). .cdzpe cons ones eee eran meee eve Nance oe tate eee 14 Strebil (2874) sick see ee are ancien eae sie earner eee 14 Koch (1892) cccc: dcp camaemigeneie sew atte si cltes i Bag aie ere orden ar 15 Wiesner: (1874) 4.c.atc oma oe areca tea ne hentia vonieinn Urania eae eee 15 Kraus, C. (18755 10 7G aay cree tees sexcas tenes ney tase ou eae 15 Weala € 1875) ..0/cndadmen an ametinierta sues re esd necs aks fpemanry tase esarcionmE 15 Mer (2895): a sshdtenrtaeeammnceeieres te nate was LenS tin datne nates Sole Nagra saae 16 Rzentkowslky ((1G7G esr esate oon cay ones encase wecsese> + ap hes easnt arene 16 Borodin \( 1G 7G yess Peete ewan Seas vas Neon ge ewasilace den sash aey Seam 16 Aekenasy (GG) siren sc eeeey ean ss ace ao sve ons ne tnt oe shee ee teen eae 17 Heckel (e876). <. :i.capenee eget etnias cacsscss 0s econ snpweenvoceqreampsuantenee 17 Baravietzicy (2079 )uri sacs tetas wetecs vont ts he nc sb a cenden case wenen aye aun ewe | Brefeld (2877) Mi..cascconsmenneraMepee as cans sheen eas csiedessgeeenn nese s team 17 Schulzer von Muggenburg (1878)............sc0ceseoeseessercenseerannnes 17 Eilfving (8800) .<.5..canernctpeeatpmenays aan ess boo) cans obegecuaeeennamE 18 Granta: (F808) «cc stoner aoe eee wag asst on be bac servos oon eee 18 Ratwenhofl €1878).0ir52 Genre ceeatie see even ee cone leas aele dep iidenetemem 18 Gtebler (16878))..25:. detec: cose eet oe +o eet * enichenbessseine: aaeaee 18 Kraus ©. (18789) cc22 i pccpenkpeeeinemeteacananen er 220%. BP ee Sy. 19 Vines. (18978) a0. scccesencade man eemmetehhea- Seated cess: see seeses en ane eaeee 19 Godlewsky (1870))..0.5.:ieccteereamarareus teente soe dae ecd toy on ¥en ceaiee mee 19 MWricemer (1880). .....<. dctaenetasneer tegen rns ce anes oe ye+ +n! 2 Sacha 20 Godlewsky (1889, 1890) ..........cccssseecseee soececseeersrseccesocsreasaes 20 ° Boehin (1886)........ sssctecssssecsmuersratetees han sce cdenes ese vesasmmaaeiaem 20 Krabbe (1582). ...:.c.cntcieccsse sense empepmenemuasscie-¢ss+- s+ +e. nik senna 21 Vochting (1884, 1887, 1891, 1893, 1894, 1900)......... 4. .seeee nese es 21 PSO (ROBE). 2 ca. ne cadicane ta cca ra ceen ata meaee Mths tiearr saa e'< Sao = «07 geen 21 Klein (1885)........ccsceecsesecseeeecereeeecreecseencscereecsseses soecesaease 22 SchoOVEE (1BSOY, 5.62 coe as. consis oe de mremnneMebmesn scab ae sce avs dan nan eWateet 22 Dutottr (1886) 22. si. conc vents scp eeoaneaatennce se geov ces sea ode d vasdarinesmmse eg 22 Stahl (0883) o-2< fas nctere seen av Menpices ceakanm ancecentnssteestinesdensaate/zeeae 22 UN itS eh LBB ) ico. sone n ho telanateai econ anes aa alepete dna Tastes “as onaeereinaee 22 Vines (1889) §<... ce cecsee ssnsnseccncseswacteneccenswasdacses) ¢osssieeeteesenne: 23, CONTENTS. ix MEER GUOQO) 20... ocssedveuveweoswsaue) ste, sbaeeermant 72 Memsusae aes Guganes 23 ISLE LOO) «cp den cid asics cusses oe antuinlen th ty sian’ « poe teNemn ave umsde Senge weekoa ss 23 Eatedine (1890, TSOT, 1893 )..+.....ctacseccecctnansnehsscseuunnedodesssnee 23 MeN NeMRERIGES ((CLOOZ ) ...0c 000 vas vqmnieedguces adele apne gsapen ceva’ sanude seeders 24 Pew andolle, CoC TG92) 0.0. cecesaevecsioud svanpeoases Spee dpeuactuyiae s ot Sa IOI Delphinium exaltatum Ait. ........... PPP eer: 22005. ee 102 Flag at set br DENS C Vsces sis. « cenishes sc ne iho s aaupete eNOS fetcive = Fos oad 103 Lirythronium Hartwegt So. Wats sc s.:5.sset a es este aes 104 CONTENTS. x1 Fralcata comosa (Li.) Kuntze .........00 ceceececeeceeseeeeseee ec ensreneceeeanens ed Fagus Americana Sweet.......cssseccseseseseeeessereeenenenanesseeesssesseeaees 105 Flix fragilis (Li.) Underw......s.ceeeceeeceseenceeeeneene rene: nerenesceesaees 106 ee corcaccans MICKS. .....600000ccnwsamen doses icg nals us meuamnasnaneeciaaeanne. 106 Ee EP ee ISELC HD TAAW ooo... scccenenvegeessnene concensus asedgneepaniney? auvnan ss 109 TIRE PF IACONEROS Lsn,.. 2.20. .cciocenc consume <. sidings See 222 Growth and development of seedlings in darkness....................2.+2++- 230 Effect.of darkness upon succulemts.:, couppeasemeeeeeee eae an -2 ees shoe oat ae 235 Etiolation of xerophytes with reduced leaves and spiny or cylindrical BECDIAS sss cecc ceed cevnseschpas te svg sbeebs pee nnEnnee rene Stth theta seade 238 Etiolation of stems of woody perennials .................. OR CASE PPD a 239 Etiolation of stems of herbaceous biennials and perennials................ 243 Influence of etiolation on the development and differentiation of the tissues ‘anid enlergencesy. $51 iassntenc seen oe eRe eRe noeies sc cos ons i aoann 246 CONTENTS. Xlil Development of stomata on etiolated stems........ ........s.ece00s SL aussh eet ae Peete Pmapectated Stes... ....'. wnceyacsasncexsuseuaninngabeusd beracnetaotee 2447 Ppiaemmaleels Of etiolated stems. ....... 250. But little difference could be found between the xylem of the normal and etiolated stems. External to this however the changes were most marked. The etiolated stem developed a distinct and continuous cambium with many layers and the sieve tissue was not to be made out with certainty, as in the normal. The space between MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 45 the cambium and the bast fibers was occupied by a mass of elongated parenchymatous cells with large lumina. The bast fibers were to be made out but were very sparingly thickened. Externally to the bast A SO) SI oD Re B ROY : ; Seen = 2 e Fic. 6. Agios Apios. Transverse section of portion of aérial normal stem; A, epidermis; B, cortex; D, bast fibers; Z, cambium; /, xylem; G, pith. >< 40. was a tract of two to five layers of cambiform cells which seemed to be very active. The formation of this secondary generative region is certainly a remarkable occurrence, and is one which finds a paral- lel only in Castanea, Hicoria and Quercus among the species examined (see Fig. 7, C). Fic. 7. Afpios Aptos. Transverse section of portion of etiolated stem ; A, epi- dermis; B, cortex; C, generative layer; D, bast fibers; Z, cambium; F, xylem; G, pith. X 40. 46 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Nearly all of the tubers from which etiolated stems were devel- oped in these cultures survived and contained a large amount of storage material, and some of them showed a second growth similar to the first, without perishing. Afzos may be classed as a plant capable of making more than one effort in different seasons to carry leafy stems up to sunlight. Aplectrum spicatum (Walt.) B.S.P. Fourteen vigorous specimens of Afplectrum spicatum were placed in the dark chamber on December 27, 1898, and soon awakened. Leaves were formed which reached matur- ity in May, 1899. Similar cultures were also made in the following year. These leaves were formed at the extremities of offsets which run 2 or 3 cm. laterally from an old C corm and then develop the terminal internodes as a corm with its apical bud apogeotropic. The leaves are put out during the season of swell- ing of the corm. The young corm receives storage matter both from the old corm and from the active new leaf. Inthe etiolated specimens the corms thus formed attained about twice the length of the nor- mal, with the longitudinal diameter much greater than the transverse, which is the reverse of the normal behavior. Fic. 8. Afplectrum spicatum. A, etiolated plant with young corm, scales and attenuated leaf. BB, old corm and young corm formed in darkness. C, inflorescence of etiolated plant. WD, single etiolated flower. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 47 The outer and lowest sheathing scale attained a length of 3 cm., and the scale from the median node of the new corm was 9 cm. long, while the leaf arising from the upper end of the terminal node attained a length of 25 cm., which is about double that of the nor- mal. The excessive development is distributed throughout the entire length of the leaf, so far as my examinations may be depended upon. The upper portion remained folded plicately in a cylindrical mass a few millimeters in diameter, and the total width when arti- ficially extended was not more than one-fourth of the normal. Numerous stomata were formed which were open when examined in alcohol. About the time that the leaves reached maturity, offsets from the young corm were sent off, which in some instances had the coralloid form taken in certain mycorhizal adaptations which I have previously described.” The development of the leaves usually occurs at the close of a vegetative season, and these organs live through the winter, falling away in the spring, when the scape arises axially to the leaf scars. In the etiolated examples, however, the development of the leaves covered a period from December 27 to May following, and the in- florescences began to push up in March before the growth of the leaves was completed. The flowering branch is composed of two or three internodes. From the upper end of the uppermost internode a scale 8 to 15 cm. long arises completely sheathing the flower bud, its edges being fused to form a complete covering. An inner scale with a length of 6 cm. also sheathes the flowers in the same man- ner. These two scales remain intact and the flowers perish with- out being exposed to the air. The separate pedicels attain a length about a half greater than the normal, and the floral envelope in the separate flowers is much reduced, although the pollinia appear fairly normal in stature. A third outer sheathing scale inclosing the inflorescence is pushed open by the flower bud with its double coat. Etiolated corms made a second growth in the dark chamber after a resting period of four months. The second series of etiolated leaves were smaller than the first. No flower buds were formed. Many of the corms were seen to be alive after the second growth in the dark, but no further action could be secured from them. 129MacDougal. Symbiotic Saprophytism. Annals of Botany, 13: 1. 1899. 48 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Arisaema Dracontium (L.) Schott. Corms of Arzsacma Dracontium were placed in the dark chamber in 1897, 1898 and 1899. After a proper resting period had been given, the terminal buds would begin to enlarge about five weeks later, and roots were sent out from the upper internode which pene- trated the soil in all directions. These roots as well as those of Amorphophallus and other aroids often emerged into the air, and were only directed back into the soil after a length of a centimeter or two had been exposed, as if the sole directive force were moisture. Fic. 9. Culture of etiolated plants of Arésaema Dracontium, showing several stages of development of the buds, scapes and flowers. After about five weeks from the beginning of the culture the buds reached a length of 25 to 30 cm., at which stage the prophyll, which had hitherto completely enclosed the leaves and flower, would split and an elbow or curved portion of the petioles of one of the leaves MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 49 would be thrust out. After a time the leaves and flowers would become entirely freed from the bud. The leaflets remained tightly folded together and were of a rich yellow color. The spathe re- mained tightly wrapped around the spadix, was smaller than the normal and also of a pale yellow color. The scape did not attain a length comparative to that of the petioles. Normally the attenuated tip of the spadix is thrust out above the leaflets, but in these etiolated examples it remained much shorter. The etiolated spadices were about normal length. The stamens and pistils did not reach normal stature, and attempts at pollination met with no result as to seed formation. Fic. 10. Arisaema Dracontium. A, epidermis of normal scape. B, epidermis of etiolated scape. C, epidermis from lower surface of normal leaflet. D, epidermis from lower surface of etiolated leaflet. >< 190 The scapes and scape were more slender than the normal. The altered dimensions of the epidermal cells did not correspond to these changes, however. Measurements of a number gave an average length of 38 for the normal and 32 for the etiolated epidermal cells of the scape. The width of normal cells was 10 and of the 50 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. etiolated 11. Stomata of normal scapes measured Io by 12 in one series and 10 by 11 in another. Stomata of etiolated scapes meas- ured 8 by 10 and 8 by 11. The stomata were slightly open when examined in water. Corms surviving the first etiolation were given a period of rest, when they were again set in action, and produced buds of not more than half the length of the first etiolated growth. No flowers were formed inthis second etiolation, however. Many of the corms were sound and alive after the second etiolation, and remained quiescent two years and are still dormant at the date of preparation of this memoir (June, 1902). Attention has been called to the saprophytic etiolated growth of the seedlings of Arzsaema Dracontium in a previous paper. The ger- mination of the seed results in the formation of a hypocotyledonary stalk which is pushed down into the soil carrying with it the plumule which remains in an undeveloped condition. The base of the hypo- cotyl soon begins to swell and the surplus food in the seed is with- drawn into the tuber thus formed, which bears the quiescent plumular bud at its apex. The entire season is thus spent underground, and the saprophytic existence of the seedling is much prolonged.” Arisaema triphyllum (L.) Torr. Arisaema triphyllum \ent itself most readily to etiolation experi- ments and it was used in obtaining data on several general questions in the investigations. Several hundred cultures have been made in the dark chamber, and this plant has been under continuous observa- tion from 1895 to 1902. Corms placed in the dark chamber after a proper resting period would soon begin to show indications of activity. Ordinarily the terminal bud of the corm elongates to a length of 5 to 7 cm. and then splits, allowing the leaves and flowers to escape. The sheath- ing bases of the two leaves enclose the base of the scape to a dis- tance of 4 to 8 cm. from the corm, and the petioles attain a length of 15 to 75 cm., which is something longer than the scape. A second scale sheathes the base of the bud and has a length of 2.5 cm. A third basal scale rarely reaches a length of over a centimeter. Marked departures from this procedure were shown by etiolated cul- 130 MacDougal. Seedlingsof Arzsaema. Torreya,1: 2. 1901. See also Rennert, R. J. Seeds and Seedlings of Ar‘saema triphyllum and Arisaema Dracontium. Bull. Torrey Club, 29: 37-54. 1902. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 51 The prophyll elongated excessively, attaining a length of 8 to 50 cm. before it splits for the emergence of the leaves and flower. The second scale attained a length of 4 to 7 cm. and the third about half that length. This test was made in another form by placing tures. Fic. 11. Artsaema triphyllum. Normal, with two latera plantlets. plants with awakening buds in an exposed situation and covering the buds with a heap of sphagnum to a depth of 30 cm. Similar elongation of the prophyll was made and the bud was not opened 52 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. till the tip of the prophyll had been stimulated by light. Still a third experiment was made to determine the capacity of the plant for piercing obstacles between its bud and light; a number of corms were buried to a depth of 25 cm. in loose garden loam and the pro- phyll reached the surface of this substratum before opening. The mechanical force exerted must have been very great. B Fic. 12. Arzsaema triphyllum. A, plant grown in portable dark chamber with occasional exposure to diffuse daylight. B, etiolated bud shortly after opening: an apical portion of the prophyll is borne on the tips of the leaf. Roots were not sent out from the crown of the corm until about the time of the maturity of the leaves. The petioles are normally about equal in length, but in etiolated cultures one was often much longer than the other. The laminae did not unfold when the cultures MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 53 were made in absolute darkness. It was noted, however, that etiola- tions made in the small portable dark chambers, which were ex- amined daily in an exposure to sunlight for two or three minutes showed a different stature for the leaves. In such instances the laminae were extended in a plane and had a superficial area of about half that of the nor- mal. This result has been verified by repeated obser- vations and suggests that etiolative reactions must be accepted with caution unless known to have been secured in a total exclusion of day- light. This caution takes on special emphasis from the fact that such vitiated etiola- tions may not show the pres- ence of chiorophyl. Sachs’ criterion of perfect etiolation is therefore not one which may be depended upon in all species: (See Fig. 12.) The scape of the flower showed excessive elonga- tion and the spathe did not reach normal size, the great- est decrease being located in the overarching hood. The spathe retained its red- dish and purplish colors in fairly normal depth so far as comparisons might be made. In some instances the hood showed a strong AQ’. . AS & aI r Triste id Est Ta oe Fic. 13. Arisaema triphyllum, grown in almost absolute darkness. epinastic growth by which it was recurved outwardly, and in nearly all instances it was more or less nearly erected. (See Fig. 13.) 54 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 14. Arisaema triphyllum, showing development of culture in Fig. 13 after exposure to daylight for two weeks. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 55 Stomata were formed in the epidermis of the etiolated prophyll, which were open when examined in water, and the guard cells con- tained much starch. The length of the epidermal cells in the prophyll was to that of the normal as 18 to 12. Similar relations were found in the epidermis of the petioles, while the epidermal cells of the scape did not differ widely from the normal in measurement. It is to be seen therefore that the excessive elongation of the aérial organs of Arzsaema triphyllum is accompanied by a multiplication of the epidermal elements, which are of slightly increased size. The sur- face of the prophyll is covered with rods of waxy exudation in the normal, which are lacking in etiolated specimens. (See Fig. 16.) Upon the maturity of etiolated aérial organs the plastic material was withdrawn into the corms, which increased by a thin layer above and cut off a thicker layer below, so that upon the ripening of the corms they were smaller than at the beginning of the test owing to the consumption of some of the material in the work of growth and transpiration. The alterations in the chemical composition of the aérial shoots and corms are shown in the analyses given below. After a resting period of a few months the corms might again be started into renewed activity which resulted in the formation of one, or sometimes two leaves only, with no flower. Third and fourth etiolations might be made in the same manner, in which only single leaves of diminishing size were formed. Half of the original num- ber of corms survived the third etiolation, and a small proportion were still alive and apparently sound after the fourth in darkness, but no further growth could be secured from them. It is probable with more attention to cultural details of temperature, especially dur- ing resting periods, that even longer endurance to deprivation of illumination might be observed. The resting periods were shortened by the treatment given the plants in such manner that four growths were made in three calendar years. The repeated growth in the dark was generally in the same ter- minal bud, but in some instances its destruction would result in the accelerated increase of two of the lateral buds which formed two small corms at the expense of the older one. It was noted in the repeated etiolations that the formation of roots was very sparing, the chief energy of the plant being directed to the construction of petioles. The germination of seeds in darkness is followed by the forma- tion of an etiolated leaf, which has a petiole longer than the normal 56 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. and an undeveloped lamina. The leaf quickly perishes and all of the plastic material is withdrawn into the newly formed tuber. Such small tubers may be started into activity after a period of rest, and may form a second leaf which also perishes during the forma- tion of the second tuber or corm. A third growth in darkness might be made, but the corms formed afterward were incapable of further endurance or existence. (See Fig. 15.) Fic. 15. Artsaema triphyllum. A, seedling after first etiolation. B, seedling after second etiolation. C, seedling after third etiolation. D, adult plant after fourth etiola- tion, from corm. The capacity of Arzsaema by which it is able to construct leaves both from corms, and from the seedling stage in darkness during three and four successive seasons is a remarkable fact, and is illustrative Fic. 16. Ardsaema triphyllum. A, surface view of epidermis of normal petiole, B, surface view of epidermis of etiolated petiole. C, epidermis of normal prophyll. _ D, epidermis of etiolated prophyll. £Z, etiolated flower. 58 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. of the immense reserve energy of plants with storage organs. Such an adaptation would be of great value in plants growing in loose moist soil in woods and meadows. The corms undoubtedly are often covered with soil, humus, or dry leaves to great depths. In such instances the power of excessive elongation of the prophyll would enable the plant to make a strong effort to emerge from such unfavorable conditions, and failing in the first attempt, the trial might be made a second, third; and even a fourth time, with greatly increased chances for survival over the plants which must win the light in the first attempt or perish. (See Fig. 12.) Cultures were made in very diffuse daylight in which the tem- perature was exactly the same as of others in direct sunlight. It was found that the petioles did not show an elongation beyond that of the average normal specimen, but the laminae were reduced be- low the average in superficial area, and assumed a curved position. The overarching hood of the spathe assumed the upright position characteristic of the etiolated cultures. (See Fig. 17.) A number of studies of the method and rate of growth of the peduncles and petioles were made. To determine the region of maximum elongation, intervals of a centimeter were marked on the petioles and scapes and these intervals remeasured at maturity. The following final lengths show the locations of the greatest growth. PETIOLE. Basal, 2 Cie. 6 7 12 10.5 4.5 Terminal. SCAPE. Basal, (Mee 5 4 5 Terminal. It is to be seen that the greatest elongation of the petioles takes place in a region above the middle, while it is basal in the scape. Peduncles and scapes have been attached to various auxanome- ters during the course of the experiments, extending over five years and the results, in so far as to periodicity and maximum elongation, have been fairly uniform. A consideration of the facts thus ob- tained forces one to the conclusion that the growth of the peduncle and petiole in light is not characterized by any periodicity depen- dent upon, or influenced by light. The rate of growth was found to increase after 10 A. M. in most instances, or a short time after a rise in the daily temperature customary in greenhouses, which as an after-effect culminated at6or8 P. M. Lesser maxima were induced MEMOIRS* OF THE NEW YORK BOTANICAL GARDEN. 59 by unusual variations in temperature. No marked periodicity could be detected in the rate of growth in the dark room kept at a constant temperature although slight fluctuations were seen. Similar irregular fluctua- tions in the rate were observed in the growth ofthe prophyllin darkness. The fluctuations in the dark room might be accounted for partly by the daily addi- Fic. 18. Arisaema triphyllum. Adult plant after confinement in dark room two weeks. Fic. 17. Arisaema triphyllum. Grown in diffuse light. 60 MEMOIRS OF THE NEW YORK BOTANICAL-GARDEN. tion of water to the cultures, which was given as the state of the cultures seemed to demand it. The same influence would also be operative in the illuminated cultures. It is therefore certain that Arisaema triphyllum does not exhibit a daily periodicity of growth independent of variations in temperature, and that the rate is not notably influenced by light; if light does retard, or accelerate the rate it is masked by the superior influence of temperature and trans- piration (see Figs. 19, 20, 22, 23, 24 and 25). Petioles and scapes which had ceased to elongate at a rate of more than a fraction of a millimeter daily were removed to the dark room when the temperatures of the illuminated room and dark room were equal, and growth was quickly renewed, an elongation of 14 to 16 mm. being made in four or five days. Such additional growth was undoubtedly facilitated by the higher relative humidity of the dark room, but must have been induced by the stimulation of dark- néss.(see Pig). 27). Etiolated specimens which had attained maturity were brought into a lighted room and found to be capable of expanding the leaf- lets, which however did not attain the average size of normally developed organs. The erect and recurved hoods of the spathes retained these positions. Variations in the final positions of the leaf- lets and general aspect of such illuminated etiolations are shown in Fig. 14. In one instance a second flower scape was developed from an etiolated plant after being brought into light. DETERMINATION OF WATER, DRIED MATERIAL AND ASH. The following series of determinations were made to ascertain the relative proportion of the main groups of constituents in normal and etiolated material. I Resting corms in a dried condition were placed in a moist cham- ber for a day, after having been out of the soil for three months. The outer dead coats were rubbed off with a cloth, and a corm of medium size with the half of one of the maximum size were weighed, and the various desiccations and combustions gave the following data ; Weight of fresh material 13.995 grams. 66 oe dried sé 3-400 oe Be et eeinid TOG: |B MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 61 Proportion of water 75.65 per cent. es ‘© dry matter 24.35 s 3; cE ee B, not including ash =. 24.29 a “ ‘¢ ash in fresh material Ai es 3 66 66 666 dried 66 3.58 66 II Leaf and petiole of a green plant cultivated in greenhouse ; Weight of fresh material 5-441 grams. 6 ‘6 dried 66 .484 ss st t* “ash = O82 4 uji85 Proportion of water in fresh material gI.105 per cent. as ‘¢ dried matter 8.995))"*.) -- ‘© ash in fresh material yr toy lt 66 6 666 66 dried 66 4.54 66 66 Corm of Above Plant Weight of corm 4.243 grams. «¢ 6 dried material wae * ef 66 66 ash -O13 66 Proportion of water in fresh material 89.84 per cent. -. ‘¢ dried matter in fresh corm oT) |? Bae fe ‘© ash in fresh material 206) “6 “6 6 6e) 66s dried be 2.44 66 6G Ill Etiolated specimens which had been cultivated one year in green- house and then forced in dark chamber ; Weight of leaves including petiole and laminae 9.811 grams. s¢ «dried material (687 co) 8 igh O51. Proportion of water in fresh material 93-00 per cent. as ‘¢ dried matter aor eas te = «¢ ash in fresh material Bis ees 66 66 666) «666 dried 6s 7.43 66 66 Weight of half of corm of above plant taken when leaves reached maturity 22.00 grams. Weight of dried material 050 ** 66 «6 ash .063 66 Proportion of water in fresh material 82.50 per cent. aK ‘¢ dried matter Pesce, 1 88/8 ihe ‘¢ ash in fresh material somone ee 66 66 666) 66 6dried cc 1.633 6s ‘6 62 MEMOIRS OF THE IV NEW YORK BOTANICAL GARDEN. Air-dried seeds collected from fruits grown on plants in the open were cleaned and dried in air at ordinary temperatures ; Weight of material oc. #6 dried matter ‘¢ ash Proportion of water a4 66 *¢ dried matter 66 ‘¢ ash in fresh material 66 66 ce ¢e dried 66 V 3.619 grams. 3.320 we -059 oe 8.27 per cent. 91.73 ig 1.63 66 te ff 66 Determination of the constituents of an entire etiolated plant dur- ing its second growth in darkness ; Weight of corm 66 ‘¢ dried material ‘¢ ash Proportion of water iad 6é ‘¢ dried matter ‘¢ ash in fresh material 66 73 66 66 dried 66 W eight of entire single leaf with petiole ee ‘¢ dried material ‘¢ ash Proportion of water 66 66 66 ‘¢ dried matter ‘6 ash in fresh material a3 (73 cr =e dried (a3 66 VI 9-927 grams. 796“ -045 66 60.18, per cent. 19.82 a 453 =" 5-89 66 4-916 grams. i) 1018, (Les 96.24 per cent. 2270 ts BOGE 5" 9°73 ‘és Determination of constituents of three seedlings during the second season of development ; Weight of corms ae ‘¢ dried material ‘¢ ash Proportion of water oe ‘¢ dried matter *¢ ash in fresh material 66 fT a ee dried 66 e6 66 1.229 grams. 302 § JO05,2; ** 75-43 per cent. 24.57 y -407 66 1.655 6 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 63 Weight of leaves 3.639 grams. *¢ ¢¢ dried material 3.92 oe ov eves .009 ct Proportion of water 89.23 per cent. ee ‘¢ dried matter 10.77 pe oe ‘¢ ash in fresh material 247 ee 2 se **. -dried material 2.28 ch VII Determination of constituents of small plant grown in very diffuse light ; Weight of fresh leaves including petioles 6.56 grams. tio *¢ dried material SAGAS pee 66 66 ash 020 66 Proportion of water 94-33 percent. ch ‘¢ dried matter 5.67 he Ms *¢ ash in fresh material 305 te 66 6 666 666 dried 6b 5-20 66 Weight of corm 2.834 grams. oe” P< dived material 557 ni 6 ‘6 ash 025 66 Proportion of water in fresh material 80.70 percent. ee ‘¢ dried matter 19.30 es te ‘*¢ ash in fresh material .882 as 66 66 666 66 dried 66 4.41 66 VIll A number of seeds of an average weight of .03585 g. were placed in the soil on January 2, 1899, and after the tubers formed from the seedlings grown in darkness were fully mature, and the leaf had perished, the following determinations of the constituents of the corms were made; Weight of fresh material “13 eran. Se atipae, |< JO24 2 7st 66 ‘6 ash 66 .OOI 66 Proportion of water in fresh material 88.4 per cent. foe Se draed, matter EL.6 4 IX Determination of constituents of four corms grown from seeds germinated in light, and the leaves allowed to come to maturity and perish ; 64. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Weight of fresh material .201 gram. 66 ‘6 dried 6 .049 66 66 ‘¢ ash 6 .002 ¢6 Proportion of water in fresh material 75.3 per cent. as ‘¢ dried matter 24.7 os xX Determination of the composition of seeds ; Weight of 25 air-dried seeds .851 gram. cc «6 dried material oz. se Fae 5G Proportion of water 10.46 per cent. 3 ‘¢ dried matter 89.54 cs 6 ‘¢ ash in fresh material 1.88 ee 66 66 6 dried 66 2.09 66 It is to be seen by a consideration of the above data that the resting corm of a plant, which has been etiolated once, contains a greater proportion of water and less dried material than the normal, a relation that holds during the second etiolation also. The propor- tion of ash in the fresh material in etiolated corms was found to be less than in the normal, while the proportion of ash to the other con- stituents of the dried matter increased by reason of the actual decrease of the latter. The proportion of water in etiolated leaves was greater than the normal, and the proportion of ash in the fresh material less, in the corm. Likewise the proportion of ash to the other constituents of the dried matter was very much greater than in the normal. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN, 65 ee beep AD 1D 2. a IG eee ene! 20 12 9 Oa ee ee ee aD P.M. A.M. Fic. 19. Curve of growth of scape of Arzsaema triphyllum under normal illumi- nation, March 26 to 30, 1901. (See Fig. 20.) Description on p. 67. 66 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 2.4.7 6. Bui MDa ee A Ny ny ee P.M. A.M. Fic. 20. Curve of growth of scape of Arzsaema triphyllum, March 30 to April 5, 1901. (Continued from Fig. 19.) Description on p. 67. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 67 CoMMENT ON Fics. Ig AND 20. Therate of growth of the scape is represented by the continuous line and the actual elongation during every period of two hours is denoted by half the distance of this line from the base line measured from the point over the numer- als denoting the hours. 5, 10 and 20 millimeter intervals are marked on the left hand margin for convenience. The course of ' temperature is designated by the dotted line, and the single reference point of 20° C. is marked on the right hand margin of the plans. The temperature is seen to range from 15° to 25° C., and the maxi- mum rate of growth of about 11 mm. for the two-hour period ending at 6 p. m.on March 30. During the last 12 hours of the observa- tions the total amount of growth did not exceed 3 mm. and the preparation was removed to the dark room with the result that an immediate acceleration of growth was shown as illustrated in Fig. 21. 5m A Pie ees Oy 1G) - Tis 5m B tage dow io 17 918 Werad Fic. 21. A, curve of growth of normal peduncle placed in dark chamber at con- stant temperature of 19 to 21° C. Maximum rate of elongation of 3 mm. in a 2-hour period was shown. JB, curve of growth of a normal petiole, fully grown, then placed in dark room as in A. CoMMENT ON Fics. 22 AND 23. The curve of growth is repre- sented by the irregular continuous line and was plotted from auxano- metric measurements beginning when the sheathing prophyll had attained a length of 10cm. and could be opened to allow the attachment of clamp of a Corbett auxanometer (see MacDougal’s Practical Text- Book of Plant Physiology, p. 287. 1g0r). The actual amount of 5mm 5mm ne le GT aD Pee) ge ot ee 5mm Be A 6 8 —10- Tae 4 6! OG Oe MAU ame OMe MS CO ek em cs cs ce P.M. A.M. Fic. 22. Curve of growth of scape of Ardsaema triphyllum in dark room at con- stant temperature of 17 to 19° C. (See Fig. 23.) 15mm ame eee OB NO «ADs OF eA SG eel PM. A.M. wie te 20.468 10 92° 90 7 dG? Sr aa ae Heal A.M. Pe BS AO 19 2 A GNI BS rahe Do P.M. A.M. ee eames es AO LD: Bh ca eater ig oy sce art P.M. A.M. Fic. 23. Curve of growth of scape of Ardsaema triphylilum in dark room at con- stant temperature of 17 to 19° C. Continued from Fig. 22. (See Fig. 24.) 7O MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 10mm 5mm. Ly. 18 9 20.21.22 28 94° 25. 26. 97-8 March, 1900 A 10mm 5mm Ij 18-19: 90° 21 285938 94 95 26 -\oiaeee March , 1900 B Fic. 24. A, grand period of growth of etiolated scape of Arisaema triphyllum plotted from daily maximum rate. JB, grand period of growth plotted from total daily amount of growth. 10mm 5mm 6PM. 6 A.M. 6PM. 6 A.M. 6PM. 6AM. 10mm — 6AM. 6PM. 6AM. 6PM. 6AM. 6PM. Fic. 25. Curve showing rate and amount of growth of prophyll of Arisaema triphyllum in dark chamber. The measurements were begun when the prophyll had reached a length of 3 cm. and ended five days later when it had ceased to elongate at a length of 35 cm. The distance from the base line to the curve denotes the actual amount of growth during the two-hour periods, the maximum being about 4 mm. per hour. The temperature of the dark room was 22° C. at the beginning of the observations and gradually fell to 20° C. near the end. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 71 growth during any two-hour period may be found by taking half the distance of the curve from the base line from a point over the numeral denoting the end of the period. Elongation continued three days later than the plotted record. Aristolochia sp. Some tubers of Aristolochia brought from Bermuda in 1900 were placed in the propagating house after a proper period of rest in February, 1901. As soon as indications of activity were shown two cultures were removed to the dark room. The normal stems attained a length of 18 to 25 cm. with in- ternodes 1.5 to 3 cm. long. The laminae of the cordate leaves measured 2.5 by 4 cm. with petioles 1 to 2 cm. long, in the normal specimen. The normal petioles were curved downward throughout their entire length, but most sharply near the laminae in such man- ner as to bring the outer (lower) surface of the leaf uppermost, at an angle of 45° with the vertical. The etiolated stems on the same date were about 15 cm. long and upright. Later the normal stems began to show marked movements and twine about supports while the etiolated stems became weak and dependent, finally reaching a length of 1.7 meters, far in excess of that of the normal at a much later stage. The terminal portion of etiolated stems remained apogeotropic and the internodes attained a length of 2.5 to 6 cm., showing a marked increase above the normal. The petioles were 5 and 6 cm. in length, which is also much more than the normal. The etiolated petioles assumed an angle of about 38° with the stem, and did not exhibit any form of geotropic response. The laminae were folded together with the upper (inner) faces appressed. The number of stomata on etiolated examples was much less than in the normal. The etiolated stems attained a greater diameter than the normal, due chiefly to exaggeration in the size of the elements in the cortex and pith. The heavy thickening of the walls of the cortex and epi- dermis of the normal was notably lacking in etiolated specimens. The pericycle was notably thinner, with the elements less heavily pitted. The entire stele remained in an embryonic condition and the cambium was much less strongly developed than in the normal. The tubers were allowed to become dry and go into a resting stage in the dark room in June, 1901. In December a second etiolated growth 72 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ensued, which did not differ greatly from the first season’s activity. Many tests were made with supports and other objects brought into contact with the apical portions of the stems, but in no instance did Fic. 26. A, terminal portion of normal stem of Ardstolochia. B, etiolated culture of Arzstolochia. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 73 twining occur, a result in accord with tests with all other etiolated climbers. The second etiolation did not exhaust the tubers, and A77s- tolochia is to be added to the list of species capable of several efforts to reach sunlight while being nourished from storage organs. Asparagus officinalis L. Clumps of Asfaragus oficinal’s in a resting condition were placed in the dark chamber in October, 1901, and soon began to send up stems. The normal cultures in the greenhouses formed shoots about a meter in height, with many branches, the branches being subdivided and bearing many cylindrical cladodes. LEtiolated stems attained a diameter about double that of the normal, being about the same F Ni WY fl SS aS N\ ee ED, Fic. 27. Portion of normal stem of Asfaragus officinalis with branch and cladode. thickness as the underground portion of normal cultures, but having much longer internodes. The internodes of normal and etiolated stems were about equal. Branches were sent out by only a few of the etiolated stems, generally by those which had fallen prostrate after a growth of about .7 of a meter. The branches were thicker than the normal and attained a length of about 10-15 cm., and were not subdivided. The terminal portion of the stemretained its apo- geotropism and curved upward when the stem had fallen by reason of its mechanical weakness. 74 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. The true leaves, which appear as bracts subtending the cladodes, were somewhat larger in the etiolated examples, and are almost pure white in color. Normal stems show a very irregular outline in transverse section due to the unequal thickness of the cortex, which is not fully illus- trated by Fig. 29. The etiolated stems are variously compressed from a cylindrical form,.but the curves in the cross-section are not so sharp or crooked. The cells of the etiolated epidermis are some- what elongated, and this layer is furnished with stomata apparently functionally normal. The epidermal cells are larger in all transverse Fic. 28. Terminal portion of etiolated shoot of Asparagus officinalis with branches, This shoot has fallen prostrate and the apex has curved upward geotropically. diameters than the normal and the outer wall lacks the outer thick- ening layer. The etiolated cortex is also composed of much larger elements than the normal, which assume more rounded forms, and are furnished with greater air-spaces. The walls of the normal cortex are much heavier than in the etiolated. The marked increase in the diameter of the etiolated stem is to be attributed chiefly to the exaggeration of the cortex, although the fundamental parenchyma may participate to some extent in the matter. Itis noticeable, how- ever, that the central lysigenous cavity of the normal stem is lack- ing in etiolated organs. The normal stem has a heavy pericycle MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 75 with walls thickened to such an extent as to almost obliterate the lumina in same instances. The etiolated stem presents a marked contrast in this matter. Only four or five layers of the pericycle oogt yA ] O° 00; 71952 Q 99 Oo = Qn EK Oe Fic. 29. I, partial transverse section of normal stem of Asparagus officinalis. I, partial transverse section of etiolated stem. A, epidermis. JB, cortex. C, pericycle. D, region in which large bundles are seen. ; are noticeably thickened and the walls have but a fraction of the diameter of the normal. The steles in the central portion of the etio- lated stems showed least departure from the normal. Those lying ex- ternally, however, remained in a primitive stage of development. The spiral vessels were best differ- entiated, while the great annular vessels had very thin walls. The sieve tissues also showed a lack of differentiation, and their contents were not so dense as in the normal. Asplenium platyneuron (L.) Oakes. Rhizomes collected at New Ca- — Fis. 30. Asplenium platyneuron. naan, Conn., November 27, 1900, Normal. After Britton and Brown. were placed in the dark room at once, and showed indications of activity within a few weeks. Fronds curved in the form of an open spiral of one and a half revolutions with a midrib 20 cm. long were 76 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. /s i ra} it i th HTT ] Se TTT Tah val Mh EET nt vy A i pase Fic. 31. A, etiolated culture of Asplentum platyneuron. B, same after illumina- tion for ten days. C, portion of midrib with pinnae, X 4. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. PL Fic. 32. Etiolated culture of Aster divaricatus. 77 78 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. formed by March 6, 1901. The midrib was about a millimeter in diameter midway between the tip and base. The pinnae were rep- resented by flattened expansions 1.5 by 1 mm. with oblique auricled basal lobes. Later three or four pairs of lobes could be made out in the pinnae. -The lower (outer) surfaces of the pinnae showed numbers of stomata with a circular outline, which were slightly open when examined in water. The guard cells, as well as the spongy parenchyma, were richly loaded with chloroplasts containing chloro- phyl, and the entire plant above the soil has a decided green color. An examination of the structure of the pinnae revealed the fact that the fibrovascular tissues were in a very primitive stage of devel- opment. The mesophyll were but slightly differentiated, and inter- cellular spaces were very sparse. An etiolated culture was brought into the light on April 2, and the older pinnae under- went but little structural change except in the formation of additional chlorophyl. Pinnae of the younger fronds, which had accom- plished but little growth at the time of illumi- nation attained a stature more nearly that of the normal, and the differentiation of the tis- sues was Carried out in much the usual man- ner. It is to be noted also that such pinnae stand much farther apart than the normal, showing an excessive elongation of the midrib. lee es PUSS BS | ee °®, 7 Dim Aster divaricatus L. Rootstocks of Aster divaricatus were brought into the dark room in February, 1900, ’ and soon showed a rapid growth of the shoot. Fic. 33- Aster divarica- Etiolated stems attained a height of about 35 tus. A, normal leaf. B,etii cm, which is not far from the average of the olated leaf. ‘ normal plant. Fifteen leaves were formed on atypical specimen, with petioles about 5 to 6 cm. long. The laminae were about 2 cm. long and'1 cm. wide when unrolled. The upper surfaces (inner surfaces) remained appressed together, only partially separating in a fewinstances. The petioles held a position from: 30 to 40° from the vertical, or rather from the stem. The hairs on the normal stems were equally abundant on etiolated organs. MEMOIRS Normal several stems have collenchymatous subepidermal layers. But one or two layers of subepidermal tissue were thickened in the etiolated culture, and only to a slight extent. The inter- cellular spaces were quite as well marked in etiolat- ed cultures as in normal. The bast fibers were only slightly. thickened and no cambium layer was formed in etiolated cul- tures. Full differentia- tion of the sieve cells was not accomplished. The bundles are separated by seeeneeeees: Fic. 35. Aster divaricatus. OF THE NEW YORK BOTANICAL GARDEN. 79 Fic. 34. Aster divaricatus. 1, partial transverse section of normal stem. etiolated stem. tissue. C, F, xylem. Partial trans- verse section of etiolated stem. Description as in Fig. 34. 2, partial cross-section of A, epidermis. 4, collenchymatous cortex. J, bast fibers. /&, cambium. G, pith. wide primary medullary rays, and the formation of secondary tissues had not begun in etio- lated stems. The xylem shows a development arrested before the vessels had reached nor- mal condition, and the pith lacked some of the intercellular spaces found in the normal. Etiolated shoots did not sur- vive very long and the earlier leaves quickly disappeared before the older ones were formed. Results similar to the above were obtained from known species which was cul- tivated later. an un- 80 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Baccharis halimifolia L. A number of shrubs of Baccharis were brought from salt marshes of Staten Island, in November, and placed in the green- houses and dark chambers. These shrubs were about 140 cm. in Fic. 36. Etio- lated leaf of Bzcu- height. Within a month a number of the buds about the base of the main stems began to grow and de- veloped slender etiolated stems, which bore small lanceolate leaves and which attained a length of a few centimeters and then perished. Bicuculla cucullaria (L.) Millsp. A number of the scaly bulbs of Bzcuculla were placed in soil in the dark room in January, Igoo, and soon showed leaves. The petioles attained a length of 10 to 18 cm., and the terminal portion immediately below the lamina was curved through a complete revolution in such manner that the undeveloped com- pound lamina was held in a position varying between the inverted vertical and horizontal. The new bulbs formed at the bases of such etiolated leaves were only half the size of the normal, and were entirely free from coloring matter. No unfolding of the compound lamina was shown and the leaves soon perished. A second growth could not be induced. The average length of the epidermal cells of the etiolated petioles was double that of the normal. The palisade tissue on the upper (inner) side of the lami- nae could be distinguished, but the remainder of the culla with bulbous parenchymatous tissue was closely packed, and no enlargement at stomatal organs were found, a fact in correlation with base. the short duration of the etiolated leaf. The width of the epidermal cells remained exactly the same in etiolations and the increase w as shown wholly in length. Botrychium obliquum Mun. Rootstocks of PBotrychium were placed in the dark room in Oc- tober, 1899. The stipe attained a length of 18 cm. below the point where it divided into two branches, one of which was again divided, at a distance of 1.5 cm. The three branches thus shown were 9g, MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 81 10, and 16 cm. in length respectively, and only the larger one devel- oped lateral branches of noticeable size, but all had a cluster of foliar rudiments at the extremities of the pinnae. A spore-bearing pinna usu- ally arises from the stipe near the point where it branches, but in the etiolated cultures this organ was represented by an atrophied structure near the base of the stipe. The stipe was much longer than the normal, and the exces- sive growth was seen to take place in the upper part of the main stalk and in the adjacent bases of the’ branches. The diameter of the stipe was something greater than that of the normal organ. The upper portion of the stipe has two schizosteles of crescentic cross-section with the concavities facing each other in the normal, and distinctly separated by masses of fundamental parenchyma. The etiolated stipe had two large schizosteles almost confluent at the margins in much the same manner as the structures in the basal portion of the normal main stipe. The thickening of the normal epidermis is noticeably lacking in the etiolated stipe. The paren- chymatous cells are slightly larger and with thinner walls in the etiolated specimens. B fo FIG. 37. obliguum. Etiolated culture of Botrychium The sclerenchymatous tissue shows but little thickening in the etiolated stipes, and a similar lack of devel- opment is to be seen in the xylem, in which the walls are hardly half the diameter of the normal. Stomata, which are open when examined in water, are present 82 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. in etiolated stipes, and the epidermal cells are excessively elon- gated, showing a length of 20 as compared with 12 in the normal ex- amples. In this instance the epidermal cells appear to keep pace with the excessive growth of the stipe, although such correlation is of doubtful significance. Some chlorophyl was present, giving the etiolated specimens a distinct green color, in accord with the be- havior of all other ferns examined. ‘Torsions were observed in the stipes of all etiolated examples of Botrychzum. It was also notice- able that the midribs of the pinnae were thicker than in the normal. The grooves usually present on the upper surfaces of normal midribs were lacking in etiolated specimens. Bowiea volubilis Harv. Bowrea volubirs is a singular type of a xerophyte. It forms a large bulb with heavy green scales, from the central axis of which usually arises a scape I to 2 meters in length, bearing small lilia- ceous flowers. The base of this aérial shoot is usually sheathed with two or three small bract-like leaves which arise from it at points below emergence from the scales. Fic. 38. Etiolated culture of Bowzea and normal branch. Bulbs, which had rested properly during the summer of 1900, were placed under cultural conditions in the dark chamber in Sep- tember. Three shoots were sent up from a single bulb, reaching a Fic. 39. Brassica campestris. Etiolated shoot, single leaf, epidermal cells’ of lamina, and elongated epidermal cells of petiole. 84 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. length of nearly a meter, bearing branches or buds at distances of 3 to 8 cm., the distance from the bulb to the first and lower branch being slightly in excess of that of thenormal. In some places, how- ever, the intervals were so short that three or four branches were crowded on a portion of stem not more than a centimeter in length. In some instances the buds developed branches 6 to 8 mm. long, sub- tended by small bracts of equal length. A bract about 7 cm. long, perfectly white, was formed at the base of each stem, being about double the normal length." A comparison with the normal shows that an excessive elonga- tion has taken place in the basal portion of the shoot, and that the development of the terminal portion has been hindered and the growth of the branches almost totally suppressed. The plant is normally a twiner, clinging closely and firmly to supports, but the eti- olated specimens were unresponsive to the pres- ence of vertical supports and were held to ft by means of cords. The terminal portions of the stems exhibited an apogeotropic reaction. The thickening of the outer walls of the epi- dermis was notably less in the etiolated examples. Stomata were present, and were open when exam- ined in water. The layer of parenchymatous tissue beneath the epidermis, which usually contains many chloroplasts and starch granules in the nor- mal plant was almost free from plastids and solid bodies of all kinds in the etiolated examples. The sclerenchyma ring internal to the cortical tissue is but slightly thickened, and the fibro vascular tissues show but little development. Brassica campestris L. Large turnips were placed in the dark room in February and the leaves were soon sent out, grow- ing very rapidly and attaining full size by the end of March. The shoots reached a total height of 55cm. Leaves attained a length of 13 cm., of which 4-6 cm. lay in the petioles. The narrow laminae all Fic. 40. Etiolated culture of Avodes. ‘ 181 For a general description of the development and growth of Bowzea see Buche- nau, F., Die Wachstumsverhiltnisse von Bowiea volubilis Hkr. fil. Abhandl. d. Naturw. Ver. z. Bremen. 6: 433- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 85 were pale yellow and endured less than a fortnight, the entire shoot perishing very quickly. The epidermis both of the laminae and of the petioles showed excessive elongation, and also perfect and open stomata, in addition to large numbers of these organs which did not reach the stage of full differentiation of the guard cells. The fleshy roots perished quickly after the death of the leaves. Caladium esculentum Vent. Corms of Caladium placed in the dark chamber in February, 1900, soon began to send up a succession of leaves with petioles 1 to 1.3 meters in length, with the laminae only partly unrolled. These laminae showed an extension of 25 cm. in length and 15 cm. in width when flattened out. The epidermal cells of the laminae Fic. 41. Etiolated leaves of Caladium esculentum. were very nearly the same as the normal in general size and outline, but those of the petiole were excessively elongated in a degree fairly correspondent with the petiole. The production of the etiolated leaves continued without interruption for a period of about 20 months, when the main bud perished, and activity of the lateral buds was exhibited in the same manner for some time. 86 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. It is to be seen that Caladium is capable of making a sustained effort to carry its chlorophyl surfaces up to light by means of the comparatively enormous amount of energy stored up in its large corms. A second series of cultures gave approximately similar re- sults, and the behavior of this plant is much like that of Arodes, to which it is closely similar in form and development. Fic. 42. Epidermis of petioles of Caladium esculentum. A,normal. 8B, etiolated. Calla (cultivated). Large corms of Arodes (Calla Aethiopica) placed in the dark chamber in November developed two large leaves and a flower stalk within a month. The flower did not reach the advanced stages of Arisaema, and the spathe remained tightly wrapped about the spadix. The leaves quickly died down, and a succession of these organs was formed continuously with no apparent resting period for nearly a year, when, the corm being nearly exhausted, death ensued. The leaves showed some chlorophy] under the conditions in which most of the species examined were entirely blanched, except the ferns (Fig. 40). The following comparative analyses of the aérial organs were made; ETIOLATED LAMINAE AND PETIOLE. Weight of fresh material 5-520 66 ‘¢ dried 66 399 eet s 86: ash, .027 Percentage of water 92.77 = ‘« dried matter 7.23 oe ‘¢ ash in fresh material -049 66 66 6 66 6k ried 66 6.76 Norma LAMINA AND PETIOLE. Weight of fresh material 4.290 > «¢ dried ee -440 Rebeca sit, .031 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 87 Percentage of water So. 8 9-73 a ‘* dried matter 10.27 “ ‘¢ ash in fresh material 72 7 a3 Gt. He dried (73 7.04 Calla palustris L. Rootstocks of Calla palustr’s were taken in a resting stage in April, and placed in dishes of water and mud in the dark chamber in April. The plant is a native of bogs and often grows in the mud at the bottom of shallow pools. Etiolated leaves had laminae slightly less than the normal, while the petioles was somewhat elon- Fic. 43. A, normal example of: Calla palustris. B, etiolated example of Calla palustris. gated beyond the normal. No other differences of importance could be discovered. Camassia sp. Bulbs of a Qaamasia (Camassia) placed in the dark room in mid- winter soon began a slow growth, the bud pushing up to a length of 2cm. before opening. The sheathing scale had a length of about 3 cm. 88 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. and the leaves developed to the normal length. The inflorescence remained in the form of a slender bud with a scape about 3 cm. long. The outer leaf was attached to a precision auxanometer in such manner that the nutations of the tip were prevented and a complete continuous record for the entire period of growth was obtained, during a period of about fifty days. A study of this curve fails to reveal any regular rhythmic action. Elongation varied from the average rate Fic. 44. Precision auxanometer used in measuring growth of leaf of Quamasia The instrument is shown with the lever attached to a leaf of Hyactnthus, and is adjusted to magnify the elongation forty-five times. (For full description of construction and use see MacDougal’s Practical Text Book of Plant Physiology, pp. 291, 292. 1901.) above and below it at times, but such fluctuations were doubtless due in part to the application of water to the cultures which was done at various times of the day, whenever necessary. The temperature was constant to within 3° C. as described above. (See Fig. 45.) Canna (cultivated). Rootstocks of Canna placed in the dark room soon began to send up a succession of leaves, which reached a maximum length of 45 cm. and which had a lamina more attenuated than the normal, being about 40 cm. long, and only 8 cm. in width. Such alterations from MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 89 6PM. 12M.64.M.12M.6PM.12M.6.A.M.12M.6PM.12M6AM.12M6PM. 12M.6A.M.12M.6PM. 12M6A.M.12M 6PM.12M.6AM.12M.6PM.12M.6.A.M.12M:6PM. 12M6 AM. 12 M6PM. 12M.6AM.12M.6PM. 12M6AM.12M Fic. 45. Curve of growth of leaf of Quamasza. Plotted from data obtained by precision auxanometer. go MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 46. Etiolated culture of Canna. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. gi the normal were accompanied by excessive growth of the epidermal cells, and by the formation of stomata apparently normal, and open when examined in water. Guttation from the mar- Se ee gins and apex of the etio- GS GN De lated leaves was very ey marked. After four or Cd five months’ continuous “f leaf production the root- 7 stocks perished. oe Castanea dentata (Marsh) A Borkh. ee ah a A number of chestnuts were placed in moist soil in the dark room and con- trol house October 10, 1901, and began germi- =| | nation about fifty days later. The stems had reached a length of 10 to I2 cm. on January 1, ri 1902. After a length of 25 cm. had been reached fs the terminal buds _per- MN TNH . ished, and branches from B the first or second bud be- Fic. 47. Epidermis of laminae of Canna. A, é normal. JB, etiolated. low took up active growth, sending up stems which had reached a length of 15 cm. by April 4, 1902. (See Fig. 48.) The basal portion of the shoot below the point of insertion of the cotyledons showed a diameter of 6 mm. and the main stem about half that amount. The entire main stem and the basal portion of the branch in the illustrated specimen had assumed a brownish hue in consequence of the changes in the cortex and epidermis replacing the normal formation of bark. The leaves were all bract-like and showed two stipular appendages of nearly equal size, all of much the same character as those borne on the first three normal inter- nodes. It is quite significant that this etiolated seedling showed noth- g2 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ing but the earlier reduced and primitive leaf forms, and about the same number of internodes as the normal seedling. Normal seedlings comparable to the above were of a height of about 25 cm. above the point of insertion of the cotyledons. The basal portion of the stem had a thickness of 3 mm. and the shoot above the cotyledons had a diameter of 2 mm. and tapered gradually toward Fic. 48. Castanea dentata. A, etiolated. &, normal plantlet. the apex by reason of the greater amount of secondary thickening in the older regions. The formation of bark was well advanced and numerous lenticels were present. The normal seedlings were fur- nished with three leaves of approximate adult form and size on the terminal portion of the stem, while on the internodes immediately below were four leaves of a length not greater than one sixth of the adult with the dentation indistinct or entirely lacking. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 93 The terminal portion of the etiolated stem showed a ring of pro- toxylem with an indistinct cambium region, which shaded grad- ually into the bast fibers external to it. The bast fibers were dis- tinguishable chiefly by their position, the walls being but little heavier than those of the cortical cells. The thick layer of cortex was composed of elements, the radial diameter of which was greater than that of the tangential. The epider- mis was composed of elements with walls but little heavier than those of the cortex. One or two subepidermal layers of the lat- ter were slightly thickened, however. A few stomatal organs with widely open aper- tures were found, which would represent the beginning stage of lenticels. The cross section of the lower portion of the etiolated ; : stem above the point of insertion of the sve SESS cotyledons showed an increase of the pith, feseeeees the formation of a thin wood ring, and the absence of secondary tissues. The cam- bium layer had taken on distinctness in Fic.49. Partial cross-section of etiolated stem of Castanea. A, epidermis. B, collapsing places, and a layer of phellogen was visible layer in cortex. C, phellogen. in the medio-cortex. The bast fiber cells 2» hard bast. #, cambium. showed about half the normal thickening. mrs: The normal stem shows an outer layer of phellogen bounded internally by a cylinder of collenchymatous tissue immediately inter- nal to which the cortical cells contain chlorophyl. A region of cortical cells shows the same indications of collapse as in the etiolated stem, but the formation of a dividing layer in the medio-cortex is not present in the normal stem. Cicuta maculata L. Clusters of dormant roots were brought into the dark room in the first week in February, 1901, and the stems began growth within a few days, reaching maturity in about four weeks. The stems devel- oped four or five compressed internodes, from each of which a single leaf arose. The leaves were held nearly erect and the petioles were two or three times as long as the normal. The branches of the petiole in the hypopodial region were only slightly and irregularly developed, the laminar tissues remaining in very rudimentary form 94 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. in Closely rolled clumps. The leaves soon perished, and growth ceased. ~ The rootstocks remained alive however and might have been capable of another effort under proper cultural conditions. Fic. 50. Etiolated cultures of Czcuta maculata. The above reactions were practically duplicated in tests with Thaspium trifoliatum grown in small dark chambers at the Uni- versity of Minnesota in 1898 and 1899, and all umbelliferous species behave in this manner so far as my observations extend. Claytonia Virginica L. Tubers of Claytonza placed in the dark room in April, at a time when natural growth of the buds was taking place, did not show MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 95 more than a third of the normal size of the stems, although the tubers still contained a comparatively enormous amount of reserve food. The flower buds remained unopened and the leaves perished quickly. It is quite probable that the limited action shown by this species was due tothe temperature, which was much higher than that encountered in the open air during its period of blooming. The plant would need the capacity of elongation to free itself from the layers of leaves which accumulate to some depth in its habitats. Cocos nucifera L.!” A number of cocoanuts in the husk, freshly arrived from Jamaica, placed in moist soil in December, 1899, soon germinated, and were Fic. 51. Cocos nucifera. Shoot of normal plantlet. placed in the dark room in February, 1900. Leaves were formed from the plantlets which differed from the normal chiefly in a slight 132 See Kirkwood and Gies. Chemical Studies of the Cocoanut and its Changes During Germination. Bull. Torr. Club 29: 321-359. 1902. 96 Fic. 52. Cocos nucifera. Etiolated shoot of plantlet after 15 months’ confinement ni dark room. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. attenuation of the broad laminar portion. A year later, after con- tinuous growth in the interval, the fourth pair of leaves had arrived at maturity in the darkness. A specimen examined on March 6 had absorbed all of the endosperm from the apical end of the fruit, but a great amount of food was still present as a layer increasing in thickness toward the opposite end, where it had been decreased but slightly from its original thick- The absorbing organ com- pletely filled the central cavity, and its rough rugose outer coat was Closely pressed against the re- maining layer of endosperm. A neck or cylindrical body a centi- meter in thickness connected the absorbing organ with the young plantlet. The roots were furnished with numerous lenticels. ous stomata, open when examined in water, were found on the leaves in the epidermis of the lower side. The upper, inner, side of the leaf seemed to be free from transpiring organs of any kind. Chlorophyl was developed very quickly under the influence of illumination of a gas jet of six candle power at a distance of three meters. A second specimen examined ness. Numer- » on May 22, 1901, had developed the sixth pair of leaves, a sparse root system, the main root being about 3 cm. in diameter at base, and had not used more than half of MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 97 the food stored in the endosperm, during the period of 15 months in which it had lived saprophytically on the stored food in the fruit. During my absence in the summer of rgor all of the specimens perished. In this as well as in other seedlings the power of ex- tended existence by means of the food stored in the seed is seen. Coix Lachryma-Jobi L. Seeds of Cozx placed in the soil in November, 1899, germinated in the following March and at the end of April had attained a height of 25 cm., showing one basal leaf untolded, and another still in the rolled form. The internodes were about 5 cm. long with sheathing petioles of the same length. The blades had a length of 8~10 cm., and were a centimeter wide at the greatest extension. Normal control examples were 15 cm. in height and the sheathing bases of the leaves about 3.5 cm. in length. The blades were 1.2 cm. wide and 8 cm. long. The lowest internode was about 5 cm. in length, and the one above iti cm. It is thus to be seen that the stems are excessively elongated and the leaves also, the latter being but little narrower than the normal. Colocasia sp. Corms of a cultivated Co/ocasza were placed in the dark room, in February, 1900, and developed leaves with petioles a meter or more in length, with the laminae only partly unrolled and held in a horizontal position, after the usual habit of the caladiums. The lami- nae attained a length of 10-20 cm. Second and third leaves were ° produced in quick succession and then the corms were allowed to go into a condition of rest through the summer. Upon the application of water to the cultures in September, 1900, the formation of leaves recommenced. The slight exposures to light in the examinations with a paraffine candle were sufficient to induce the construction of chlorophyl, in this as well as in caladiums and cultivated callas. (See page 86.) The leaves were found to be proheliotropic to such feeble illuminations, and apogeotropic. Guttation was very marked, the exudations issuing from the apices, margins and injured portions of the leaves. Cornus alternifolia L. f. Vigorous shrubs of Cornus 3 meters in height were taken from the soil about December 1, 1901, and after a period in a cool cham- 98 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ber were placed in the control and dark chambers in the middle of December. ‘The first activity was observed in the specimens placed in the dark chamber on January 18, 1902, at which time a number of buds midway on the branches and on the middle portion of the stem began to elongate. Later all buds on the main axis and branches in the upper portion of the shoot perished and only those from the basal portion survived. These, however, showed a vigor- ous growth. It was found that the upper part of the stems of all of the plants had died as a result of the transplanting. It is noteworthy that the awakening buds were all infra-axillary. On April 6 some of the young etiolated branches had attained a length of 18-20 cm., at which time a photograph was taken from which the accompanying drawing was made. A few branches measured twice this length on June 17, 1902. The etiolated branches assumed an atti- tude very nearly vertical, in consequence of which some of them were appressed to the stem. No branching occurred except in one or two instances. In such the up- permost pair as well as the terminal bud would elongate approximately equally. The leaves on etiolated branches attained a length of nearly a centimeter, but remained small and bract-like, although giving some imitation of the adult form. The hairs so noticeable in the young normal stems and leaves were present even on the older por- tions of etiolated stems and were very Fic. 53. Cornus alterni- folia. Normal branch. abundant on the younger portions. These hairs consisted of a short upright stalk bearing a slender ovoid capitate cell with its long axis parallel to the surface. The branches retained their colorless aspect for some time, and showed a slight tinge of brown in June, five months after their appearance. The cross-section of the apical internode of the etiolated stem showed the pith in the process of enlargement, a thin cylinder of wood cells with an indistinct cambium layer. The bast fibers formed an incomplete circle of spindle-form cells with but little thicken- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 99 ing. The cortex was composed of the customary thin-walled cells, which with the pith contained some starch, and was furnished with intercellular spaces. The epidermal cells were slightly thickened as also one or two layers of hypodermal tissue. Some widely open stomata were present. \ TV Fic. 54. Cornus alternifolia. Base of young tree with spreading normal branches and upright etiolated branches. In the older internodes the pith had attained twice the original diameter, the wood ring had increased by continuous and uniform external additions, and some thickening had ensued in the bast fibers. The number of these elements had not increased, and the walls were pushed inwardly in some instances as if the cells had collapsed. No indications of collapse were to be seen in the outer layers of cortex, or in any way comparable to that seen in Castanea, a fact which is correlated with the shorter period of duration of Cornus. The formation of a distinct phellogen in the epidermal region had 100 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. reached an advanced stage, and was followed by some discoloration of the epidermis. Normal stems of the same age showed no indications of the formation of phellogen. The cortical cells were smaller than in the etiolated with the tangential greater than the radial diameter. The bast cells were much like those of the etiolated stem. A region immediately underneath the epidermis contained much chlorophyl, which also extended down into the pith through the rays. No marked differences in the trichomes could be found. Cyclamen sp. Corms of Cyclamen purchased from a dealer were placed in moist soil in the dark room in January, 1900. The growth of the leaves soon began, and elongated petioles were formed, which were soon Fic. 55. Cyclamen. A, normal epidermis. J, etiolated epidermis. C, etiolated hairs, from the petiole. DD, normal hairs from petiole. Terminal portion of petiole with etiolated lamina. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. IOI prostrate with the apical, terminal portion apogeotropic, and bearing the small undeveloped laminae with the upper (inner) surfaces ap- pressed. The petioles and laminae were purplish in color, and the epidermis bore short hairs filled with a reddish cell sap. The etio- lated hairs were slightly smaller than the normal. The epidermal cells were excessively elongated, being four or five times as long as the normal, and the stomata were larger and apparently functional. The production of leaves continued more or less irregularly dur- ing a period of 18 months, and then the activity slowed down, and the corms went into a state of rest from which it was impossible to rouse them, although still sound and healthy. In no instance were the flower stalks developed. Cypripedium montanum Dougl. Dormant specimens of Cypripedium were placed in the dark chamber in January, 1900, and began growth a month later. Two months later a young flower bud was pushed out from among the etiolated leaves, but did not open or attain normal size. | | ‘ | Fic. 56. A, epidermis from normal leaf of Cypripedium montanum. B, glandular hair from surface of normal leaf. C, epidermis of etiolated leaf. D, glandular hair from etiolated leaf. The main stem attained a length of only 2 cm., which is only a fraction of that of the normal. The excessively elongated leaves 102 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. were 15 cm. in length, and 2.5 cm. wide, while the normal leaves are 3. by 3.2 cm. Epidermal cells from the lower surfaces of the etiolated leaves measured 32 by 4 while those of the normal were only 15 by to. Etiolated leaves bore glandular hairs only, the pointed trichomes being absent. The shaft of the glandular hairs in the normal, con- sists of two cells with an average total length of 50 and diameter of 4, while in the etiolated the shaft was composed of four cells of an average total length of 110 with a diameter of 12. The apical gland measured 22 by 19.5 in the etiolated, and 16 by 13 in the normal. From the above facts it is to be seen that the growth of Cyprz- pedium in darkness is characterized by a non-development of the pointed hairs on the leaves, and the excessive development of the glandular trichomes. The first result is in accord with Schober’s re- sults, but no reason is at hand to account for the excessive enlargement of the glands and the multiplication of the cells in the stalk, unless these organs might be considered as aids to transpiration. The stomata of the leaves were of normal size, but of slightly attenuated outline, being apparently functionally normal. The laminae maintained an erect position, and were more or less rolled during all of the period of their existence, embracing about a month. Delphinium exaltatum Ait. A number of rootstocks of Delphinium exaltatum were potted and brought into the dark room on January 18, 1900, and began to grow at once. The main stem attained a length of 8 cm. as against the normal of 4 cm. and the total height was 28 cm. while normal plants under similar conditions were only 15 cm. high. The etio- lated petioles reached a length of 10 to 30 cm. while the normal measured only 4 to 6, thus showing the most excessive elongations in the petioles. The petioles assumed a negatively geotropic posi- tion with the laminae pendent by means of a curvature at the extreme tip of the petiole. The actual rate of growth was about twice that of the normal, during a period of ten days kept under observa- tion. An etiolated specimen was cut off and the base of the shoot thrust into water in a calibrated measure, through a cork which was smeared with vaseline to prevent evaporation from the water surface. The total volume of the exposed stem was 5 c.c. and MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 103 included 6 etiolated leaves. 1 c.c. of water was taken up in 24 hours in the dark room at a temperature of 16-18° C. A shoot of a normal plant with seven leaves, the whole having a volume of 2 c.c. used 2 c.c., or its own volume of water in 24 hours at a temper- ature of 18 to 20° C. in diffuse daylight. (See Fig. 57.) Equisetum arvense L. A number of bulb-bearing un- derground stems of Agzsetum ar- vense were placed in a dark room in January, 1900, and a month | ‘ \/ Fic. 57. Etiotated shoot of Delphinium exaltatum. later two sporophytes and a number of vegetative shoots were to be seen. The latter developed only a small number of branches to a length equal and greater than the normal, the remainder attaining a length of a centimeter or two, and the whole shoot showed some attenuation. In only two instances out of 40 under ob- servation did these branches give rise to branches of the second order. The vege- tative shoots perished within sixty days, Fic. 58. I, normal young vege- - : ney which may have been due to defective ative shoot of Eguzsetum arvense. fee } I, etiolated shoot. cultural conditions. (See Fig. 58.) I 104 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. A few spore-bearing stalks or sporophytes developed to a height of a few centimeters, and the spores appeared fairly normal in structure, showing a green coloring matter, but the sporangia did not open and the spores soon perished. Erythronium Hartwegi S. Wats. Numbers of bulbs of Erythrontum Hartwegi obtained from dealers were placed in the dark chamber in the spring of 1901, and a single leaf 12 to 15 cm. long was sent up from every one. The leaf, as well as most of the bulbs, soon perished, however, probably due to imperfect cultural conditions. Falcata comosa (L.) Kuntze. Tubers of Falcata comosa were placed in the dark chamber in the spring of 1899, and rapidly developed stems. A comparison with control examples showed that the lowest internode of the normal stem was 7 cm. in length and that a runner was sent out from this inter- Fic. 59. Partial cross section of normal stem of Falcata. A, xylem. JB, scleren- chyma. C, sieve tissue. JD, bast fibers. > 80. node which grew to the length of a meter or more, while in the etio- lated examples the lowest internode attained a length of 13 to 28 cm., and the runners were represented by branches not more than a cen- timeter in length. The successive internodes in the normal measured 3, 3, 4, and 5 cm., while in the etiolated all of the internodes above the basal one MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 105 described above, hada length of 7 and8 cm. It is thus to be seen that etiolation phenomena are shown by this, as well as by all of the other vines examined in the course of the experiments. Furthermore it was found that in no instance did these vines exhibit a tendency to twine about supports as in the normal. Fic. 60. Partial cross section of etiolated stem of Falcata comosa. X 80. Descrip- tion as in Fig. 60. The leaves remained as very small rudiments. Etiolated stems were thicker than the normal by reason of the excessive development of the cortex and pith. The epidermal cells of etiolated plants were larger than the normal in all dimensions. The sclerenchyma showed less thickening, as also the bast fibers, and less sieve tissue was differ- entiated than in the normal. The xylem was also less developed than in the normal. Fagus Americana Sweet. Trees of Hagus Americana 3 meters in height were placed in the control house about December 1, 1901, having been taken from the soil and placed in large pots. About half of the buds were removed from all of the plants. A young plant 25 cm. in height which had been in the greenhouse three years was also placed in the dark 106 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. chamber. No action of any kind was shown as late as June 23d although the temperature was probably suitable for this species. Similar results were obtained by Jost with Fagus. (See p. 26.) Filix fragilis (L.) Underw. Rhizomes taken from the soil at New Canaan, Conn., on Novem- ber 28, 1900, soon showed activity and developed fronds with mid- ribs 25 cm. long with 5 pairsof pinnae. ‘The pinnules were unfolded, being about 4.cm. long. ‘The lower pairs were opposite in the usual manner, but the upper pinnules were variously alternated. The entire frond was deeply tinged with chlorophyll. The rootstocks were intact after this growth, and could doubtless send up other fronds after a resting season. Galium circaezans Michx. Rootstocks of Galiuwm circaezans placed in the dark room in January, 1900, developed stems which were 30 cm. long with the 1G. 61. Normal leaf of Galiéum circaezans. - Fic. 62. Etiolated leaf of Ga- lium circaezans. ongest internode measuring 7 cm. on March 22. The leaves were partially rolled on the long axis, ovate, and with an obtuse apex. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 107 The middle nerve only was apparent. Motile stomata were present which were open when examined in water. The stems were about 2 mm. in diameter and were circular in cross section, the angles of the normal stem being entirely lacking. Glandular hairs and functional stomata were also present. The epidermis was composed of cells of rounded outlines in cross section, and the collenchyma usually pres- ent in the angles was entirely absent. The etiolated cortex was ex- tremely thin-walled, and showed intercellular spaces. The stele re- mained in an embryonic condition. The vessels of the xylem and Fic. 63. Galium circaezans. A, transverse section of etiolated lamina. JB, epi- dermis of etiolated leaf. C, epidermis of normal leaf. protoxylem were barely distinguishable, and groups of sieve tissue might be seen. The epidermal cells of the etiolated stem were scarcely more elongated than the normal, but are wider in surface view. The angle of the stem in the normal bears a duct furnished with glands of the usual stature. The stomata were closely crowded together as if the entire number had been formed in the earlier states of development and were not separated by the normal development of the epidermis, which did not take place. Anthocyan was pres- ent in the leaf, and masses of a yellowish substance in the paren- chyma cells of the laminae, and also in the etiolated shoot. The epi- 108 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. A, epidermis of normal stem. B, epidermis of Fic. 64. Galium circaezans. etiolated stem. > 20. N s oy iY "8 ¥ NS Se ef? SOU TO ns. A, epi- Partial cross section of normal stem of Galium ctrcaeza ExG. 65. C, sieve tissue. D, xylem. Z£, pith. dermis. B, cortex containing chlorophyl. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 109 dermal cells of the leaf were naturally smaller in the etiolated organs and more regular in outline, while the palisade tissue, and spongy parenchyma are not differentiated. Fic. 66. Partial cross section of etiolated stem of Galzum ctrcaezans. Descrip- tion same as in Fig. 65, except that the cortex contains no chlorophyl. Gasteria disticha Haw. A single specimen brought into the dark room in September, 1900, soon began growth. The young leaves, the apices of which were barely exposed, were carried into an erect position instead of being brought to the horizontal as in the normal. A small offset with thin linear or lanceolate leaves was developed from the basal inter- node, reaching a length of several centimeters on May 20. (See Fig. 67.) This branch perished during the summer. Similar elongation, and erection of propagative branches was to be noted in Sanseverza. The main stem was greatly elongated, the internodes attaining a length IIo MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. of 3 or 4 cm. and were partly exposed instead of being entirely sheathed by the leaf bases as in the normal. A single slender inflorescence axis was developed from the axis of the first leaf reach- ing a length of 4 cm. and then underwent atrophy. The normal leaf of this species is roughly rectangular in cross-section, while the etiolated was double convex. The rugose formations of the normal leaf were lacking in the etiolated, except at the margins of Fic. 67. Gasteria disticha. A, plant after six months in dark chamber, show- ing two leaves formed in light, and two partially developed in light which completed their growth in darkness, also inflorescence, stalks and smal] runner or offset. the lower etiolated leaves; those found later were entirely smooth. Etiolated leaves were only half the length of the normal, a fourth of their width, and a third or fourth of their thickness. The chlorophyl of the older leaves was retained with no apparent alteration, and a slight tinge of green was noticeable in etiolated leaves due to the occasional exposure to the light used for inspection. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. gi dial Fifteen months after the culture began, the leaves, which had reached full development before confinement in darkness, had perished and the leaves formed partially in light and partially in darkness had begun to die at the tips. (See Fig. 69.) The upper internodes showed a successive increase in the length of the inter- nodes, and the leaves were held at various irregular angles. Such a Fic. 68. Gasteria disticha. A, partial transverse section of normal leaf. B, par- tial transverse section of etiolated leaf. C, surface view of normal epidermis of leaf. D, surface view of etiolated epidermis. positions were partly due to the rupture of the stems near the nodes and also to the sheathing leaf-bases. The structural alterations in etiolated leaves were very marked. The epidermal cells of the normal leaf were irregular polygons in surface view, in which but little difference might be seen in the vari- ous diameters. These cells underwent great axial elongation in etio- lated organs, and the outer cutinized layer was notably lacking. The guard cells of the normal stomata are extended outwardly making II2 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. an elevation on the surface of the leaf by a single thickening of the outer cutinized layer. Such thickening was wholly lacking in the etiolated leaf, and the guard cells are slightly sunken below the sur- face. The guard cells do not undego full differentiation, and the supporting cells were smaller than in the normal, being functionally Fic. 69. Gasteria disticha. Same plantas in Fig. 67, 14 months after confine- ment in dark room. The leaves formed in light have perished and the younger etio- lated leaves are held in various aberrant positions due to ruptures in the stem. active however, as attested by the long endurance of the etiolated leaves. The parenchyma cells of the normal leaf are richly loaded with starch and chlorophyl, which were entirely lacking in the etiolated organs, the plastids present being much smaller than the normal. The growth of the etiolated specimen continued until Feb- ruary, 1902, at which time it was damaged in handling and per- ished. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 113 Gleditsia triacanthos L. Seeds placed in a dark chamber in October, 1900, did not ger- minate until March, after which growth proceeded very slowly. The cotyledons were carried aloft attaining a total length of 15 mm., and were ovate with an auriculate base. The upper, inner surfaces were closely appressed. The cotyledons endured for about 60 days in the dark chamber, when they were thrown off, and the first node of the stem attained a length of 8 mm. bearing a pair of appressed leaves, which did not unfold, but in which the pinnae were distinctly visible. ‘The hypocotyledonary stem attained a length of 18 cm., which is about one and a half times’the length of the normal. The root system formed in the dark was very sparse, being made up of a tap root with a very few branches. The lower surfaces of the cotyledons were furnished with stomata, the guard cells of which were loaded with starch, and which were closed when examined in water, being apparently not functional. The seedling perished after the above development had been accomplished. Hemerocallis sp. Bulbs of Hfemerocallis placed in the dark room in early spring after activity had begun in the open, showed an active development which resulted in the formation of leaves 11.5 cm. long. The upper or inner surfaces remained closelya ppressed, and the entire leaf was colored a pale yellow. ‘The flower stalks or inflorescence gave no indications of activity. Hicoria sp. A number of nuts from an unknown species of hickory were placed in moist soil in March, 1900, and germinated in May of the same year. The stems had reached a height of 40 cm. to 60 cm. in June and were then checked by the high summer temperature, the terminal buds being destroyed. In November of the same year a renewed growth ensued after the summer resting period, and one more of the original lot of nuts germinated. The apical buds of the older plants being dead the lateral buds nearest awoke, and the branches formed from them assumed the upright positions of the main stems. Some etiolated specimens removed to the illuminated room developed leaves resembling the customary forms in normal cultures. Growth and development of the shoots continued until March, 1got, thus showing that the seedlings were capable of an 114 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. existence of nearly a year in darkness at the expense of the food stored in the nut. Hicoria minima (Marsh) Britton. Nuts of Wicoria minima were placed in moist soil in the control chamber, and dark room on October 16, 1901. Three of those in the dark room had germinated and sent up shoots, one of which had reached a length of 12 cm. on January 4, 1902. None of those in the control chamber in illumi- nation had shown activity at this time. On April 16 five plants were to be seen in the illuminated chamber with stems 5 to 8 cm. in length and bearing a num- ber of reduced bract-like leaves and two, trifoliate, or simple laminae. At this time the etiolated specimens had attained a length of 25 cm., in some instances bearing a single straight up- right stem with the terminal bud still active. The leaves were simple and bract-like, soon falling off. The lower third of the stem had begun to show a dark brown color Fic. 70. Hicoriamimima. Eti- olated shoot and terminal portion of normal shoot MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 115 indicative of the earlier, or initial stages of formation of periderm. On June 17 one stem had attained a height of 36 cm. the longest internode measuring 8 cm. The normal stems of the age of the etiolated showed a brown color at the base due to the death of the epidermal cells. Five or six layers of cork had been formed underneath, and the thick-walled cortex contained much chlorophyl, especially in the outer layers. Crystals were numerously distributed throughout this tissue. A: heavy cambium layer was present, and the incomplete ring of bast consisted of cells which had undergone extreme thickening. All of the parenchymatous cells were heavily loaded with starch. A cross secticn of the basal portion of the etiolated stem that had begun to turn brown showed the epidermal system in a fairly normal condition with the walls white and translucent. The usual forma- - tion of cork in the hypodermal region was lacking, but a median region in the cortex had begun to collapse, the walls assuming a brownish hue giving the external color to the stem. The entire cor- tical region had thinner walls than in the normal and both starch and crystals were noticeably less abundant than in the normal. In this as well as in Cornus and Quercus, the lack of cork formation in the hypodermal region was accompanied by the development of a phel- logen immediately external to the cylinder of bast cells, some- times in immediate contact with the collapsed layer: the bast fibers were nearly normal in stature so far as might be seen in cross sec- tion. A distinct layer of primary cambium could not always be made out, and the walls of the wood cells were not so heavy as in the normal. The above collapse of the median region of the cortex was accompanied, or followed, by the shrinkage of the basal portion of the stem in such a manner that it had a smaller diameter than the terminal portion, a phenomenon also seen in Quercus. Hicoria ovata (Mill) Britton. Nuts of HWicorza ovata placed in the soil in the control chamber, and the dark room on October 16, 1901, had begun to germinate on January 4, 1902. On April 16, one young plant with two primitive leaves was seen in the control chamber, the stem being about 8 cm. long above the place of insertion of the cotyledons. The lower part of this stem bore a few bract-like leaves. Two seedlings were found in the dark room. One had sent up a main stem about 25 > 116 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. cm. in height, when the terminal bud perished. A lateral bud then devel- | oped an erect branch which extended the total height of the shoot about 30 cm. above the soil. The terminal bud of this branch also perished and the growth of other lat- | eral buds had begun. The behavior of the cortical and epidermal tis- sues was much the same as in AZ. minima. The median collapsing layer of cortex turned brown- ish-yellow, and with the disintegrating epidermal cells gave the stem a brownish-black hue. The bast fibers were fewer in number, and but little thickened in any instance. Hyacinthus sp. (grape hyacinth). Leaves of awakening bulbs attained a length of 25 cm.in darkness, which were crescentic in cross Pale section, and yellowish, or perhaps slightly greenish \" f at the tips. The presence tl > of some chlorophy] was to SER: So be detected in many plants, the leaves of which were Fic. 71. Hicorta ovata. Etio- lated plantlet, and terminal por- tion of normal shoot. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. formed in the buds of the bulbs or corms. The flower buds retained their dormant condition for a time, then perished. The widths of the nor- mal and etiolated leaves were found to be about equal, but the etiolated leaf was a half longer than the normal green one. When etiolated leaves were brought into light no further increase could be detected either in width or length. A slight flat- tening of the partially rolled or curved leaves ensued, however. Hyacinthus sp. flyacinthus sp. developed leaves 30 cm. in length, which were rolled in tube form, and were II and 12 cm. in width when flattened out for measurement. Secondary leaves from lateral scales of the bulb attained half this length and retained the cylindrical form. No develop- ment of the inflorescence could be seen. Hydrastis Canadensis L. Rootstocks of Hydrastis Canadensis placed in the dark room in January began growth a month later. Sterile stalks bearing only leaves reached a height of 30 cm. with a diameter about equal, or in some instances exceeding the normal. The petiole at first showed an elbow immediately below the lamina, but which disap- peared on maturity, and the lobes of the lamina were appressed with the upper surfaces together and directed upward. ‘The stems bearing both ieaves and flowers showed a much greater elon- gation, but their length bore about the same proportion to the normal. The curvature of the petiole at first enclosed or shielded the peduncle and pendulous flower bud, thus presenting an elbow of stem as it pushed upward. Finally, however, the petiole became erect, as well as the peduncle which was formerly protected by it. Fic. 72. AHydrastzs. Etiolated stem. ) 117 118 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Starch was lacking from the etiolated petioles except in the guard cells of the stomata. The fibrovascular tissues were fairly normal in their general development and structure, and the stems were approx- imately of the same degree of rigidity as the normal. The epidermal cells of the etiolated stems were slightly elongated. The hairs borne on etiolated stems were not more than one fourth of the length of the normal. Similar differences are to be found on the leaves. The stomata of both the laminae and the stems were slightly open when examined in water and appeared to be functional. No rhythm in growth could be detected from an examination of the aux- Fic. 73. Hydrastis. Normal anometric measurements. (See Fig. 74.) leaf. ' 10mm 9 218. -8" eee 2 bee eee 9 A 6 6 10 Bis 4 ooo fee A.M. Rais 10mm. OA 8 Bp ACs ie ey Oh me A.M. P.M. Fic. 74. Curve of growth of stem of Hydrastis during three days in dark room at a temperature constant between 22 and 24° C. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 119 Hypopitys Hypopitys (L.) Small. Clumps of Hyfopitys which were breaking through the soil near the Marine laboratory at Cold Spring Harbor, Long Island, in 1899 were covered in such manner as to exclude light. No appreciable difference in the stature or appearance of these plants and others in the light could be detected. This test was repeated at Woods Holl, Mass.,in the same year, and also at Priest River, Idaho, in the following year with the same result. It is also notable that this plant does not usually exhibit phototropic curvatures, although as may be seen by reference to the historical sketch, many fungi are capable of both etiolative and phototropic reactions. i Fic. 75. Etiolated stems arising from tubercle of sweet potato. I20 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Ipomcea Batatas Poir. Tubercles of the sweet potato placed in moist soil in the dark room in November began to produce stems in January, and sent out a succession of these organs, which were apogeotropic, but soon became decumbent with the terminal portions curved upward. The apical buds soon perished, and the lateral growing points began activity. The leaves developed petioles a half or two thirds of the normal length, with the laminae folded with the ventral surfaces together. The laminae did not attain a superficial area of more than a tenth of the normal. The leaves were crowded together on the basal portion of the stem, being not more than 1 or 2 cm. apart on a section about 20 cm. long, in normal plants. Above this the leaves are more scattered on a portion of the stem in which twining usually takes place. This terminal twining portion was not developed in the etiolated plants. (See Fig. 75.) No important differ- ences could be detected between the structure of normal and etiolated stems. The leaves quickly perished and dropped off, leaving a distinct protuberance at the point of connection with the stem. (Fig. 75+) The tubercles per- ished after the first eti- olated growth, and the plant does ,not seem adapted to making a second effort in dark- ness. Iris sp. Shortly after root- stocks were placed in the dark room the buds began activity, and a Fic. 76. Etiolated specimen of /r7s, and epidermis k of etiolated leaf. succession of leaves was MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. I21 formed, which were slightly in excess of the normal size. The epi- dermis was elongated beyond the measurements of the normal, and the leaves did not survive long. The stomata appeared to be functional. Fic. 77. Normal flowering shoot of Lysémachia terrestris, and also shoot grown in ditfuse light with branches replaced by bulbils. 122 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 78. Leafy shoot of Lysimachia terrestris grown in diffuse daylight. Etiolated shoot of Lys?- machia terrestris with apical portion of same enlarged. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 123 A second series of cultures with a species native to eastern America in March in the dark chamber showed a development of two leaves with a length of 23 and 25 cm. which were free only a few centimeters at the tip. The slightest exposure to the light used in examination was sufficient to stimulate the production of chloro- phyl. Lysimachia terrestris (L.) B.S.P. Lysimachia terrestris consists of a branching rhizome with aérial leafy stems which may bear flowers, or the numerous branches may be converted into, or remain in the form of, bulbils as the author has discovered in some previous investigations. When such rhizomes easecsaeenereee O Cerat E ») 4 SDs ee “aNsets ™~B @ ray Os Fic. 79. Lysimachia terrcstris. Partial transverse section of normal stem. A, air-spaces in cortex; B, xylem; C, bast fibers; D, glandular ducts; £Z, sieve tissue. are placed in the dark room, slender etiolated stems without branches or bulbils are produced, with internodes of a length of 1 to 5 cm., while in the normal stem the length of the internodes varies from 5 cm. to 3 cm., the longest being found in the middle of the stem below the flower-bearing branches. The total length of the etiolated stem was slightly greater than that of the normal flowering shoot, 124 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. which continues to elongate during the greater part of its existence in the open. The opposite leaves on the etiolated stems remained in a rudimentary form and were upright, being closely appressed against the stem. The leaves do not attain a length greater than 5 mm. and a width of 1.5 mm., dying away on the lower internodes as the stems Fic. So. Lysimachia terrestris. Partial transverse section of bulbil. A, air spaces; B, protoxylem; £&, protophloém; /, endoderm; DY, ducts. progress, much after the same manner as in the normal specimen, so that only three to five pairs were to be seen at one time. The number of internodes in the etiolated and normal stems are prac- tically equal. The diameter of the etiolated stem was barely halt that of the normal. The epidermis of the stems as well as of the leaves showed numbers of stalked glands of apparently normal struc- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 125 ture. The cortical cells of the etiolated stems were richly loaded with starch, as well as the guard cells of the stomata. The differ- ence between the sizes of the epidermal cells in the etiolated and normal specimens was not great. The red anthocyan of the normal specimen was lacking from the etiolated specimen. The great air spaces of the cortex are present in both the etiolated and normal. The glandular ducts were also present. The stele remained in an embryonic condition ; the cam- bium ring was apparent, and was fairly complete. A number of elongated cells in the phloém with dense contents and strictly trans- verse walls seemed to be sieve tubes arrested in an early stage of development. A few layers of closely packed parenchyma cells lay closely to the internal surface : Aah Sy of the xylem, while the central pith was made up of plates of cells with great air-spaces. A comparison of the etiolated stems; with the bulbils reveals the Fic. 81. Lystmachia terrestris. Partial fact that the anatomy of the two transverse section of etiolated stem. A, is very closely similar, and both pith and cortex; BB, protoxylem; CC, may be regarded as stems in a sieve-like cells; DD, ducts. state of arrested, or very incomplete, differentiation of the tissues. =a 7A aces moe Menispermum Canadense L. A number of the underground rhizomes of Men/spermum were placed in the dark chamber in January, 1900. The aérial stems, which are lateral branches from the rhizomes, soon made their appear- ance, and in three months attained a length of 25 to 50 cm., with the 1383 MacDougal, D. T. Vegetative propagation of Lysimachia terrestis. Bull. N. Y. Botanical Garden, 2: No. 6. p. 82. 1g01. See also Practical Text-Book of Plant Physiology, pp. 320, 326. 1901. 126 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN, longest internodes about 5 cm. At this stage the shoots began to perish. The stems seemed to be apogeotropic and exhibited distinct nutating curvatures. The leaves were expanded but extremely small, Ee eS Star | pee ge uae oo Fic. 82. Menispermum Canadense. A, epidermis of normal stem; B, epidermis of etiolated stem. Etiolated culture. standing out from the stem at an angle of 50° to 60°, the lower ones perishing before the stems had reached full length. It is to be noted MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. I27 that the ordinary aérial stems usually form but few leaves before reaching a length of a meter or two, hence this is a vine which does not show excessive elongation, or suppression of organs to any marked extent, in etiolation of awakening shoots. The epidermal cells were smaller in all dimensions than the normal, and the stomata which seemed to be present in normal numbers were functional. The hairs were hardly so numerous as in the normal. A normal collenchy- Fic. 83. Menispermum Canadense. Partial transverse section of normal stem. A, epidermis; JB, subepidermal layer; C, cortex; D, bast fibers; Z, Sve mys eer, xylem parenchyma, Cambium and sieve tissue are to be seen between D and £. matous subepidermal layer was lacking in the etiolated stems, and the cortex showed an increase both in number and size of the elements, and contained no intercellular spaces in either instance. The etio- lated cortex showed five to eight layers of cells and the normal but three or four. The bast fibers formed a complete cylinder in the normal, while in the etiolated stem they are represented by elongated elements with walls but little thicker than the cortical cells, and the groups external to the separate bundles did not fuse or extend into each other. The sieve cells seemed to be quite as well differentiated in the etiolated specimen as in the normal, although not so numerous, and the lumina 128 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. were not so great, as if these elements had taken on mechanical as well as conductive functions. The xylem offered as many vessels as in the normal, but these did not reach the size of the normal, and a notice- able lack of development of the intravascular parenchyma was to be seen. Extremely large intercellular spaces were to be seen in the pith of the etiolated stems. The cambium cylinder, composed of A ~p Fate Cc =; D e' LSE Ady x ITS ECR LES | 7 STAY | Ohie Fic. 84. Menispermum Canadense. Partial transverse section of etiolated stem. Description as in Fig. 83. two or three layers in both normal and etiolated stems, appeared to form a continuous cylinder in the etiolated stem, but was interrupted by the heavy rays in the normal. This vine behaves in accordance with Sachs’ conclusions that vines are etiolated stems, but the lack of development is probably due to lack of nutrition. Twining was not observed in any of the stems of the numerous cultures. Many of the rhizomes were alive after the first growth in darkness, but cultural conditions did not per- mit a second growth. Narcissus Tazetta L. A large number of etiolations were made of Varcissus from bulbs obtained from dealers during the period 1896-1902. Bulbs of JV. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 129 nana, VV. poeticus and JV. tazetta were cultivated in the dark cham- bers and the results obtained from the three species were so nearly uniform that no separate discussion is needed for each. The leaves attained a length more or less in excess of the normal in all instances, and showed a somewhat attenuated epidermis with functional stomata. The air spaces were not so large as in the normal, and the sheathing scales at the base were longer. The leaves normally assume a position nearly erect, but in the etiolated plants these organs soon become decumbent and prostrate. Their width is fully equal to that of the normal. The inflorescence axis normally exceeds the leaves in length, or at- , tains a length about equal to them. \ The stalks show a large lysigenetic central cavity which was not so large | in the etiolated stalks. The etiolated inflorescence axes did not reach a |} length of more than half of the \| normal, and the flowers scarcely ad- \\ vanced beyond the stage in which }} they are to be found in the normal | | buds just emerged from the bulbs. \" | The inflorescence was enclosed in a i \ complete sheathing scale which did \\ a not open. In no instance did the \\ i I | flowers emerge or assume a normal | | aspect. Onoclea sensibilis L. Rhizomes of Onoc/ea taken from the soil in March, soon developed long stipes with the laminar portion rolled up. The stipe reached a length of 70 to 80 cm., while in the normal it did not measure more than half this length. The increase in length was accompanied by an excessive increase in thickness due to the exaggeration of the funda- Pr tlh, 1 ew ” ; Fic. 85. Etiolated culture of Oxoclea mental tissue. The gamosteles were sensibztzs. I30 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. fairly normal but did not fuse until a greater “distance from the base than usual had been reached. The sclerenchymatous external lay- ers, including the epidermis, showed less thickening, to which was due the greater pliability of the etiolated stems. A few of the stalks of the lower pinnae were elongated, but in every instance the foliar or laminar tissues remained in a clump or bunch. Fic. 85. Oxoclea senstbilis. Partial transverse section of normal and etiolated stipe. &. epidermis. Etiolation is thus seen to result in an excessive elongation of the stipe in the basal portion. The rhizomes were not exhausted by the growth of etiolated fronds, and appeared capable of making a second effort to reach light. Ornithogallum umbellatum L. Bulbs of Ornzthogallum placed in the dark chamber in January, 1901, developed leaves with a length of 22 cm. within a month. The leaves were crescentic in cross section, many of them twisted and about 6 mm. in breadth when flattened. The flower bud re- mained dormant during the entire confinement to darkness, and when | the preparations were brought into light after two months, the leaves showed some decay at the tips, but made an increased growth, while the flower bud remained inactive. The bulbs were not exhausted by this treatment, and seemed capable of making a second growth in darkness. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. I31 Opuntia Opuntia (L.) Coult. A number of fronds of Opuntia Opuntia were laid flat on moist soil in the dark room, in November, rgo1, and had developed cylin- drical or compressed stems, which were slightly longer than the normal by January 6, 1902. The leaves, which are subulate and fall off early in the normal, were of an attenuated ovoid form, being drawn down to a very small diameter both at the base and apex. These leaves persisted until the etiolated stems began to show signs of deterioration, when they were easily detachable. Fic. 87. Opuntia. Prostrate normal frond, from which arise etiolated stems. Marked deviations from the normal were to be seen in the struc- ture of the leaves. Numerous multicellular hairs were found around the leaves, but very few bristles were to be seen. The epidermal cells including the stomata were reduced in size in etiolated plants, and the arrangement of outer layers rich in chlorophyl with their 132 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. long axes at right angles to the surface was noticeably lacking in etiolated stems, in which no differentiation was to be seen except in the development of one or two layers of smaller cells beneath the epidermis. These cells contain a large number of globular clusters Fic. 88. Opuntia Opuntia. A, etiolated epidermis, surface view; B, normal epi- dermis, surface view. of crystals in the normal, which are not nearly so numerous in the etiolated fronds. The outer walls of the epidermis were less thickened in the etiolated. Osmunda cinnamomea L. Clumps of Osmunda brought into the dark room in April, 1900, soon developed long straggling fronds thickly clothed with pale hairs, with pinnae extended but not attaining a length in excess of 1.5 cm. The entire frond showed a distinct greenish tinge due to the presence of a marked amount of chlorophyl. The outer tissues including the epidermis were much less thickened than the normal, the epidermal cells being notably elongated and containing chloro- plasts. Functional stomata were present and contained many chlo- roplasts. The parenchymatous tissues as in the normal showed some inter- cellular spaces, but the walls were more or less wavy. The endo- dermis (phloeoterma) was made up of smaller elements with less thick- ened walls than in the normal. The pericyclic cells were not to be distinguished from the sieve cells or the adjoining parenchyma. The mass of tissue between the endodermis and metaxylem, usually consisting of the pericycle, the parenchyma separating it from the sieve tissue, and the parenchyma between the sieve tissue and the metaxylem, was much thinner than in the normal, and it was not pos- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 133 sible to determine which of these tissues was lacking. The meta- xylem was but little different from the normal. The walls of the i] fi ; mS gel? Fic. 89. Etiolated culture of Osmunda cinnamomea. protoxylem (consisting of groups of small cells immediately inside of the xylem) were not so much thickened as in the normal. The in- 134 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 90. O. cinnamomea. Terminal portion of etiolated frond, and single pinna. fo) loos Ye) oe, ° Oo! S OS So ° 5 98 (2) iS 2 Ore RAS re) 6 9 @) We a) [e) S ae SOx Fic. 91. Osmunda cinnamomea. A, normal epidermis, surface view ; B, etiolated epidermis, surface view; C, partial transverse section of etiolated stipe; D, partial transverse section of normal stipe. MEMOIRS OF THE NEW Fic. 92. region. Q fa’ 2. Osmunda cinnamomea. es YORK BOTANICAL GARDEN. 135 oe ax YE: 12, a, Seely! Transverse section of portion of normal stelar A, endodermis (phloeoterma); G, specialized group of pericyclic cells con- taining tannin; B, Z, sieve tubes; C, D, metaxylem; F, pericycle and tannin cells in this tissue. 136 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ternal sieve tubes were larger than in the normal and with lighter or thinner walls. The endodermis internal to the sieve cells just mentioned was less heavily thickened than in the normal, and was not to be separated from the pericycle bounded by it. ve é we KK) ee Fic. 93. Osmunda cinnamomea. Transverse section of portion of etiolated stelar region correspondent to that shownjin Fig. 92. Description as in Fig. 92. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 137 Oxalis lasiandra Zucc. Bulbs of Oxals lastandra placed in the dark chamber at various times were compared with cultures in very diffuse light, and in day- light. The first activity was shown in the development of leaves with elongated petioles and some offsets. The roots did not break out un- 2 Fic. 94. Oxalis lasiandra. Transverse sections of leaf. A, normal; B, etiolated. til later. The length of the petioles was as much as 11 or 12 times that of the normal in some examples, while in others it might not reach more than double the length of the normal. In one series of Fic. 95. Ovxalis lasiandra. Surface view of epidermis of leaf. A, normal; B, etiolated. tests the average length of normal petioles was 20.87 cm., in diffuse light 36.9 cm., and in darkness 47.1. The thickness in normal and 138 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. etiolated specimens was about the same, but those in diffuse light were much heavier, probably in response to the mechanical stimulus of the weight of the leaflets. The laminae remained in the folded condi- tion in which they emerged from the bud, in the etiolated examples, and attained only about one fifth of the volume of normal examples. Fic. 96. Oxalis lastandra. Surface view of epidermis of petiole, < 250. Fic. 104. Peltandra Virginica. A, epidermis from dorsal surface of lamina, normal. #&, epidermis from dorsal (outer) surface of etiolated lamina. > 300. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 47° sults were obtained from the study of a number of plants at differ- ent times. : A fully etiolated specimen of .Pel/tandra which was brought into diffuse daylight, showed some marked changes as the result of Fic. 105. Peltandra Virginica. A, epidermis from normal petiole. JB, epidermis from etiolated petiole. illumination, among which were to be noted the assumption of the horizontal position of the laminae, and the unequal development of the basal lobes which ensued under such conditions. Peltandra is a bog plant, or rooting aquatic, according to circum- stances. Phaseolus sp. (cultivated). Numbers of seedlings of Phaseolus were etiolated with the in- variable result that the first internode attained a length about three times the normal, when proper cultural conditions were furnished. The first pair of leaves developed petioles over a centimeter in length, and laminae of equal length. The entire shoot of the seedlings attained an extreme length of 30 cm., the terminal portion above the 148 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. single pair of leaves being about 6 cm. long, with recurved apex. The stalks were generally more or less compressed and flattened. In other tests the terminal portions of large plants were conducted into small dark chambers to secure ‘* partial” etiolations. Branches treated in this manner developed flowers which were fairly normal, except that they were blanched. The essential organs were perfect, and fertilization en- sued, pods and seeds being formed. The latter were apparently perfect, but no germination tests were successful. The leaves were entirely devoid of chlorophyl, but the leaflets were held in various posi- tions with the upper surfaces concave, and did not exhibit the nyctitropic movements, so far as my ob- servations went, although particular attention was not paid to this point. It is to be seen that the effects of ‘* partial etiola- tion” differ most widely from those in which the en- tire plant is deprived of light. In partial etiolations ew >. iy A Fic. 106. Etio- = Fyg. 107.. Terminal portion of shoot. The branch A, has been enclosed in a lated seedling of small dark chamber and bears leaves, flowers and young pods formed under Phaseolus. these conditions. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 149 it is difficult to furnish absolute security against admission of light, and the darkened portion is probably influenced by the illuminated regions near it. Phytolacca decandra L. A number of strong roots of pokeweed were taken from the soil in a resting condition in November and placed in pots in the control house, and dark room immediately. Growth began about a month later. The shoots pro- duced in the dark chamber elongated much more rapidly than those under normal illu- mination and had attained a length of 22 cm. on January 22, 1902. Shortly afterward these shoots perished and others sprang up from the crown, which likewise made only a limited growth. This process was repeated, and on April 27 four etiolated shoots were to be seen with others beginning to develop. On July 6th the stems had reached a length of 42cm., with leaves 45 cm. long. The tuber- ous underground storage organ remained intact and seemed sound and healthy. The diameter of etiolated stems did not exceed 11 mm., which is much less than the normal. The cross section was ovoid in outline although lacking the small irregular- ities of that of the normal stem. The etio- lated leaves consisted of a small slightly elongated petiole curved upward froma horizontal position with a much reduced lam- ina. The entire leaf was a rich yellow 16-108. Etiolated stem en of Phytolacca decandra. color. The pith showed the transverse splittings of the normal stem in the basal portion, but in the terminal portion a long continuous cavity occupied the center of the stem. The epidermis was not excessively elongated and had comparatively thin walls. The prestomatal cells were to be seen richly loaded with granular matter and plastids and in some instances the first division had taken place. The collen- chyma was fairly well developed in the angular portions of the stem occupying about six or seven layers, in some instances and but two I50 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. or three in other places. The cortex was composed of extremely thin walled elements with some intercellular spaces. The protoxylem was fairly normal but the woody tissue was very imperfectly developed, while the formation of the secon- dary wood ring and xylem had only progressed so far as to show Fic. 109. Phytolacca decandra. Structure of etiolated stem. A, epidermis; B, collenchyma; C, cortex; D, bast fibers; 4, location of secondary cambium; /, cam- bium; G,xylem; H, surface view of epidermis, showing one prestomatal cell. groups of elements with denser contents in the positions of the vessels, and the presence of a layer of cambiform calls external to them. Numbers of elongated lenticellular ridges appeared on the basal portion of the stem in the region from which the leaves had fallen. The comparatively brief duration of the shoot was coupled with the non-formation of stomata on the stem. Podophyllum peltatum L. Rootstocks of Podophyllum were brought into the dark room at various times and the leaves and flowers allowed to develop. Petioles showed an elongation about 80 per cent. in excess of the normal and the epidermal elements were correspondently elongated. The lobes of the centrally peltate leaves were about one third the length of the normal, and were folded with the under surfaces together, the whole etiolated laminae having the form of a partially opened umbrella. Stems bearing both leaves and flowers reached a length about double the normal in darkness, and the flowers were fairly normal in structure opening partially. The lack of functional ma- turity of the stomata was accompanied by a brief duration of the leaves and stalks, and the etiolated organs soon perished, resting MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. T51 buds being formed on the rootstocks which could not be awakened in the dark room. Fic. 110. Podophylium peltatum. A, stem bearing flowers and two. leaves; B, peltate leaf. Normal. Polystichum acrostichoides (Michx.) Schott. Clumps of Polystichum acrostichoides were brought in from the open, and forced in the dark room in February at the New York Botanical Garden. The fronds soon developed long upright stipes along which were borne the pinnae tightly rolled in clumps. Much of the excessive elongation took place in the basal portion, which at- tained three times its normal length. The sporogenous tissues at the @ 152 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 111. Podophyllum peltatum. A, B, stems bearing flower and two leaves ; C, peltate leaf. Etiolated. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 153 % => iy “a ‘ Fic. 112. Polystichum acrostichotdes. Normal. rc r % M }: é E : ss i : ar i : ‘ 4 57 7 Y 7 yy =—Z x > = 5] f cE ! : ay ie 7 - iis Boas ent Ve “Say3! Fic. 124. Quercus sp. Partial transverse section of lower part of stem. I, nor- mal. II, etiolated. £, epidermis. D, phellogen. C, collenchyma. JB, cortex. TS <. f >a \, 1 Y ) 1 stem of C,cambium. JD, bast Partial transverse section of lower part of norma Quercus sp- Fic. 125. B, woody cylinder. A, perimedullary parenchyma. E, inner cortex. seedling. fibers. (p 164.) Fic. 126. Quercus sp. Partial transverse section of lower part of etiolated stem ylinder. C,cambium. D, of s eedling. A, perimedullary parenchyma. 8, woody c (p. 165.) bast fibers. #, inner cortex. 166 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. tion of phellogen was ‘found, although it was marked in the corre- sponding region of normal stems. The cortical cells in the etiolated appear to be smaller than in the normal stem, and more compactly arranged. The bast fibers form a continuous irregular ' circle in the cross section of the normal stem but were still separated by the medullary rays in the etiolated. The more interesting differences of structure were to be found in the lower and older parts of the stem. The epidermis and hypodermal cells inthe etiolated had be- come irregular and were slightly collapsed. A phel- logen had been formed in the medio-cortex, and the cortical cells were somewhat larger than in the normal, and with thinner walls. The difference between the bun- dles of bast fibers was still very marked. The sieve tissues showed a diameter Fic. 127. Quercus sp. Seedling in second s,hoyt half that of the nor- year. Normal (oblique) and etiolated branches. 5 mal, and the cambium layer was not so well marked as in the normal. The elements of the xylem were in general larger in all dimensions, but the thickness of the xylem ring was hardly half that of the normal. The walls of all of the tissues in the xylem were thinner. (Figs. 123-126.) The petioles showed corresponding differences in the normal and etiolated. The epidermal tissues were less thickened, and no col- lenchyma was to be seen. The separate bundles of the meristele were in a very rudimentary stage, with the sieve tissue but imper- fectly developed, and the pericycle entirely lacking. The bundles were clearly separated by rays of parenchymatous tissue. (Fig. 121.) A seedling of an unknown Quercus was brought into the dark { MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 167 10mm Grier G er Be TO. 1D) Be: A be ani inl a A.M. P.M. 10mm Cee. BIO’ Te oe OO. EOF eld A.M. P.M. DAE a! SOG 6 pee Mian (0 aa Sg a ee © Pn = a |) ain De ate Oe ee Be ND AS Ne ES PIMA: SO | ale =) age a. aay «Shae capeage 8 Shoal 9° A.M. P.M. Fic. 128. Curve of growth of etiolated petiole of RAeum in dark chamber at tem- peratures 21-23°C. The actual amount of growth during the two hour periods is denoted by half the distance from the base line at a point above the numerals to the wavy line denoting rate of growth. 168 room in November, 1go1. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Two buds near the base of the young inclined stem soon awoke and formed stems 15 and 25 cm. in length. FIG. 129. Etiolated leaf of 7?hewm, Y% actual size. These etiolated stems were twice the thickness of the normal, due to the exaggerateddevelopment of the cortex and the internodes were longer than the normal. The leaves did not go beyond the stage described above. (Fig. 127.) Rheum sp. Rootstocks of rhubarb obtained from a dealer were placed in a dark chamber in the early part of March and sent up leaves in which the peti- oles were both thicker and longer than the nor- mal. The branches of the petiole in the laminar portion of the leaf separ- ated but slightly, and in so doing ruptured the in- active lamina in many places, a phenomenon also observed in the re- lated genus /tumex. Such etiolated leaves elongated at a fairly con- stant rate, the minimum being shown about 10 A.M. It could not be as- certained from the study of the auxanometric data whether this resulted from a true rhythm or MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 169 whether it was the consequence of application of water about the hour in question, after which elongation increased. (Fig. 128.) The composition of etiolated leaves of rhubarb has been the sub- ject of many studies and tests on the part of practical investigators, and the cultivation of this plant in darkened cellars, and in total dark- ness is an industry followed by many gardeners. This method of cultivation appears to have been hit upon by Knight. A recent manual gives the details of management of these plants in darkness.™ Rhus sp. (native shrub). A root of /ehus carried into the dark room in March with a clump of soil adherent had developed a shoot 35 cm. long with seventeen rudimentary leaves by May 1, the lower eight of which had fallen off. The angular outline of the normal stems was preserved, anda number of lenticels were formed near the base of the shoot. The pith was composed of uniformly thin-walled cells with large intercel- lular spaces. A cambium layer could not be made out, but some bundles which from their position must have been of secondary for- mation were to be seen. ‘The cortex was very thin-walled and no thickening of the subepidermal tissues was seen. The epidermis was free from stomata, but bore numerous pointed and glandular hairs. The sections assumed a milky appearance on being placed in water. The leaves attained a total length of over a centimeter and were curved downward. The two basal pairs of pinnae were extended but had a total length of only afew mm. The leaves were densely hairy, showing both forms of trichomes as noted below. No stomata were formed, which is correlated with the brief existence of the shoots which soon die in darkness. Ricinus communis L. Seeds placed in dark chamber germinated and produced hypo- cotyledonary stems 30 cm. in length, which were weakly erect. The cotyledonary stalks were 2 to 3 cm. long. The cotyledons were not freed from the endosperm in any instance, and made no growth, soon falling off, exposing the plumule. The first pair of leaves attained a length of about 8 mm. If the endosperm were removed the cotyledonary stalks curved downward after the customary move- 1344 Knight, T. A. Ona method of forcing rhubarbin pots. Trans. Hort. Soc. Lond. 3: 154. 1820. Morse, J. E. The New Rhubarb Culture. New York, 1go1. 170 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ment which brings the cotyledons to a horizontal position in normal plants. In some instances the seedlings continued ex- istence after the endosperm and cotyledons had been discarded altogether. The first internode often assumed a length of 5 cm. and had leaves with laminae a centimeter across, with the petioles re- flexed. Rumex sp. A resting specimen of a eumex native in the Garden was brought into the dark room December I, 1901. Two weeks later the development of the leaves began and a succession of these organs were formed during the next four months. During my absence from the Garden during February and March, 1902, no observations were recorded, but 20 of these organs were seen and the plant was still alive and engaged in sending up leaves, on July 23, 1902, making an additional noteworthy example of a plant capable of extended endurance without the activity of the chlorophyl apparatus. The petioles of the etiolated leaves attained a length of 30 to 35 cm. and were flattened on the in- ner, ventral surface. The laminae were represented by thin lamellae of yellowish tissue which extended along the midrib for a distance of 14 to 17 cm. with a width of about a centimeter narrowing toward the base and apex. The petiole appeared to be in a state of elongation throughout its entire length, and the excessive growth of its continuation in the midrib resulted in the rupture of the lamellar struc- tures. In some instances the laminae showed sufficient resistance to set up a marked tension, by which the midrib was held in a curved position some time before giving way. The epidermal cells of the petiole were excessively elongated and some of the normal compound hairs were seen, being also present on the lamina. Perfect and functional Fic. 130. Etiolated leaf of Rumex sp. % actual size. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. T7t stomata were found both on the petiole and laminae. Geotropic curvatures were exhibited by the terminal portions of some of the leaves which had fallen prostate while still growing actively. Salvia sp. Numbers of branches of a cultivated Sal/v/a were thrust into small metal dark chambers during the course of the observations in 1896 and 1897. Such chambers were made as tight as possible by means of packing of cotton wool, but it can not be definitely affirmed that all light was excluded. If the branches had already laid down flower buds, a development would () SS ensue in which the calyx would attain about two thirds of its nor- Fic. 131. Salvia sp. Normal flower with mal size, but the corolla, which is extended earolla and etiolated flowers with 5 corollas atrophied. usually much longer and highly colored, failed to emerge from the calyx, and was almost colorless. The stamens and pistils also failed to reach normal stature or to at- tain functional maturity. : Sansevieria Guineensis Willd. A specimen was placed in the dark room in September, 1900, and when examined in May, 1go1, nearly all of the mature green leaves originally borne by the plant were still alive and but little changed as to texture or color. Three young leaves which were about 10 to 15 cm. long at the beginning of the etiolation were now twice this length by basal growth, and the additional portion thus formed was a very pale green in color. One prominent terminal bud had become apogeotropic and formed an upright stem 15 cm. in height with the lower sheathing bracts about 12 mm. in length which is something in excess of the normal. This growth of the upright stalk was continued after a resting period in the summer of 1901 and in January, 1902, seventeen months after the beginning of the test, this stalk was 20 cm. long. May I, 1902, twenty months after confinement all of the leaves had perished, but the etiolated stalk still continued. The basal inter- nodes had attained a length of 12 to 14 mm., but those nearer the tip 172 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Fic. 132. Sansevierta Suineensts. Culture after confinement in dark room for 20 months MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. E73 of the stem which had now reached a length of 35 cm. were not more than 5 to 7 mm. Jong. The stem had fallen prostrate by its own weight, but the terminal portion had curved upward apogeo- tropically. A number of small papillar projections a millimeter in diameter were seen emerging from various parts of the internodes. In some instances the emergences were from nodal areas, while in others a position in the middle of the internodes was occupied. Gen- erally but one of these structures was found on each internode, but in some instances two were found. These emergences were sup- posedly young roots. The terminal half of this upright stem was imbedded in the soil in the propagating house, and developed a new plant, forming an exception to the old statement that etiolated organs could not be used as cuttings. The upright etiolated stem showed two or three layers of epidermal cells with brownish collapsing walls, a fundamental parenchyma of small elements, with some intercellular spaces. The outer fibrovascular bundles were notably reduced in both xylem and phloém as well as in the stereome. Sarracenia purpurea L. Numbers of specimens were grown in the dark chamber in 1898. The leaves were wedge-shaped in transverse sec- tion, and slightly greater in diameter than the normal. The leaves already formed, and which had reached a length of a Sid eae Fic. 133. Sarracenia purpurea. A, etiolated culture. B, etiolated culture after exposure to illumination for 18 days. C, etiolated leaf. 174 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. few cm. before being placed in the dark chamber formed a small pitchered cavity, and an extension of the flap to a width of 8 or 9 mm. The over-arching lip extended only 2 to 7 mm. beyond the end of the cylindrical portion which would have formed the pitcher in the normal. Leaves which developed from the bud after being placed in dark- ness showed the normal size of cavity, but the lateral flap of the leaf Fic. 134. Epidermal structures of normal leaf of Sarracenia purpurea. A, epi- dermal cell and hair from terminal flap. &, surface view and section of epidermis from ‘‘ attractive” area. C, epidermis from ‘‘ conducting ” area. D, epidermal cells and hair from ‘‘ detentive”’ region. After drawing Wm. B. Stewart. was reduced to a wedge-shaped rudiment, and the arching lip was scarcely apparent. In such instances glands were found over the entire leaf and long, slender hairs were to be seen in the pitchered cav- ity. The diameter of the cavity in the normal pitcher was six to eight times that of the etiolated leaf. The etiolated leaf was twice as long as the normal, and much of the elongation took place in the basal MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 175 portion of the leaf, which was five timesthe normal. This elongation also extends upward into the basal portion of the cavity of the pitcher which in the region below the detentive hairs was ten times the normal. The region covered by the detentive hairs was 1.4 times that of the normal. Above this the etiolated conductive surfaces was only one eighth of the normal and the attractive honey-bearing region had dis- appeared. The lateral flap of the normal was nine times as long and —_— BS ieee OA GSS Sites ae Fic. 135. Epidermal structures of etiolated leaf of Sarracenia purpurea. A, from terminal flap. ZB, ‘‘ attractive” surface. C, from ‘‘ conducting” surface. D, from ‘‘ detentive” region. , inner surface of cavity of ascidium. (After Stewart.) sixteen times as wide as the etiolated. The relative lengths of the various regions are shown in Fig. 136. The epidermal cells of the external surface of the upper part of the leaves ranged from 10 to 22 in length in the normal and from 25 to 63 in the etiolated. The width in the two instances ranged from 7 to 20 in the normal and from 3 to 5 in the etiolated. Not all of the stomata were differentiated. 176 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. The epidermal cells in the lower portion of the cavity which underwent excessive elongation were 1.64 times as long as the normal, but the normal were 1.4 times as wide as the etiolated. A similar re- lation holds in the detentive area where the epidermal cells were 1.29 times the normal in length but the latter are 1.55 times the etiolated cells in width. An increase of the actual number of cells in the etio- lated detentive region was thus demonstrated. In the conducting sur- )! Wa panes hy ial PLS 1. Fic. 136. Diagram showing relative development of various regions in normal and etiolated leaves. I, normal. II, etiolated. -A.terminalflap. J, ‘ attractive” surface- C, ‘‘ conducting” surface. D, ‘‘ detentive” surface. £, cavity below detentive sur. faces. , petiole. Drawn by Wm. B. Stewart. face the cells of the epidermis are 1.35 times the length of the etiolated, in the normal and are also 5 times the etiolated in width, showing a decrease in the number of cells. The same is true of the attractive surface in which the normal is more than twice the etiolated in all dimensions. Trichomes of all kinds are both longer and thicker in the normal. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 177 Sarracenia variolaris Michx. Rootstocks of Sarracenia variolaris were placed in the dark room in January, 1900, and etiolated leaves had reached the maximum size Fic. 137. Sarracenia variolaris. A, epidermis from outer surface of normal leaf. B, epidermis from outer surface of etiolated leaf. C, etiolated leaf. 178 MEMOIRS OF THE NEW YORK BOTANICAL’ GARDEN. in March. These leaves showed torsions of the basal portion, and at- tained a length of 18 to 20 cm., which was not in excess of the normal. The over-arching hood was found in the etiolated leaf as a conical pro- RHR dnt | ly Mg TAT PST) eer i in Toa i A Fic. 138. Etiolated cultures of Saururus cernuus. A, lamina and portion of pet- iole of etiolated leaf. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN, 179 jection 1 to 2 mm. in length, and generally two gland-like structures were to be seen on the upper edge of the lateral flap. Other rudi- mentary glands were to be found down along the edge of this lateral ex- tension. The utricular cavity was present and extended to a depth of 3to5mm. It was lined with small cells rich in protoplasm which were wholly undifferentiated. ‘The epidermis of the outer surface of the leaf was composed of cells with four walls in surface view, and were also rich in protoplasm. Honey glands were present. The epider- mal glands, as well as the stomata, were fairly normal. No trichomes were present. The pitchered cavity also lacked the hairs and glands of the normal. The leaves endured existence for three months after nearly full size had been reached. (Fig. 137.) When etiolated leaves were placed in light the lateral flap under- went some extension but no great differentiation of the utricular formations ensued. Saururus cernuus L. Rhizomes placed in dark chamber in May, 1901, soon developed stems with a height of 40 to 54 cm., being composed of 9 or Io inter- nodes each 2 to 11 cm. long and showing a diameter at base of stem Fic. 139. Saururus cernuus. Partial transverse sections of etiolated and normal stems. I. Etiolated. II. Normal. A, epidermis. 2B, collenchyma. C, cortex. of 1.6 cm. and at apex of .6m. The petioles attained a length of 5 cm. in some instances, but the sheathing bases did not keep pace 180 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. with the thickening of the stem and they were soon cast off. The laminae were partially unfolded and measured about 5 by 3 cm. A few of the axillary buds showed some development and runners were sent Fic. 140. Epidermis of etiolated petiole of Saururus cernuus. out from the bases of some stems, each bearing several smaller leaves of the above aspect. It is to be noted that this plant roots in mud and may grow in water 60 cm. in depth. (Figs. 138-140.) Sparaxis sp. Plants of Sparaxzs placed in the dark room sent up leaves to a height of 10 to 20 cm. which were strictly erect and closely adher- ent, and soon perished. No flowers were developed. The humidity and temperature was probably too high for this species. Solanum tuberosum L. In tests to determine the length of time this species might endure continued deprivation of illumination it was found that two seasons might be passed without light, smaller tubers being formed on branches. The tubers formed during the second season perished because of unfavorable conditions in the culture room, and it is perhaps possible for this species to endure considerably longer periods without light. A number of tubers were placed in the dark chamber in October, 1900, and by March, 1901, had produced a great number of length- ened club-shaped foreshoots which were 20 to 30 cm. long and 1.5 to 2 cm. in thickness with no geotropic sensibility. ‘These stems were extremely brittle. Branches were curved in various ways and were easily detachable. Typical tubers were formed on the branches from such stems under the surface of soil. This experience was MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 181 repeated in the winter of 1902. Similar shoots 60 cm. long were formed with but few branches. The epidermis formed a few func- tional stomata, and the epidermal cells contained highly granular lining layers of protoplasm. The thickened foreshoots described above grew and remained alive about six months.” Taraxacum sp. Rootstocks of dandelion placed in dark chamber showed some attenuation and a full blanching of the leaves. Excessive elongation ensued in the basal portion. Tipularia unifolia (Muhl.) B.o-P. Specimens received from South Carolina and placed in the dark room developed new corms of two internodes each 3-5 cm. long from the apical portion of which leaves 20 cm. in length were sent up. The laminae were rolled in a cylin- drical form, and were wholly free from chlorophyl. The width of the leaves was about that of normal organs. Trillium erythrocarpum Mx. Corms placed in a small dark chamber in 1896 devel- oped stems slightly longer than the normal with the leaves epinastic in such manner as to sheathe the flower bud. Itis Fic. 141. Normal and etiolated cultures of to be noted that these tests were 770" @7y¢hrocarpum. imperfect etiolations. The flowers opened slightly, but did not form fruits (Fig. 141). 5 Batalin, A. Ueber die Wirkung des Lichtes auf das Gewebe einiger mono- und dicotyledonen Pflanzen. Bull. d. 1. Acad. Imp. d. St. Petersbourg, 7:69. 1869. In addition to other papers by Knight (see p. 4) and Véchting (see p. 21), see Vochting, H., Ueber die Keimung der Kartoffelknollen. Bot. Zeitung, 60: 87-114. 1902. 182 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Trillium erectum L. Plants formed in the dark room in 1896 had the leaves appressed around the base of the peduncle and were smaller. The peduncles Fic. 142. Normal and etiolated cultures of Trzllium erectum. were not so long as in the average. The flower opened in a fairly normal manner, but did not produce fruits in these imperfect etiola- tions. . Milla uniflora R. Grah. = 77ctelia unifora Lindl. Plants were etiolated in March, 1900. The leaves, which are normally twisted and curved, attained a length of two or three times the normal, being 35 to 50 cm. long and § to7 mm. in width. Num- bers of leaves from lateral buds attained a length of 10 cm. anda width of 1 to 2 mm. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 183 The inflorescence axis emerged from the sheathing leaves at a distance of about 8 or 9 cm. from the bulb and was distinctly apoge- otropic with the peduncles attaining a length of 14 to18 cm. The flower stalks were extremely sensitive to light, soon showing apoge- otropic curvatures. The etiolated flowers were enclosed by two trans- lucent bracts united except at the tip and projecting beyond the flower 5 or6mm. These sheathing bracts arose about 5 or 6 mm. from the base of the flower tube. The separate portions of the perianth were about 16 mm. long, ovate and with the adnate stamens apparently perfect. The relative proportions of the stamens and pistils were as in the normal. (Fig. 144.) Fic. 143. Normal culture of M/clla uniflora. The normal leaf of 77rztelia = Milla is 12 to 15 cm. long and 8 to 10 mm. wide, being perfectly plane in cross section, while the etiolated are crescentic. The flower and its stalk are about 18 cm. long and become negatively geotropic after fertilization. The sheathing bract is about 2.5 cm. long, splitting as in etiolated specimens and is dorsiventral. The ovary is about 2 cm. long and the perianth about 3 cm., being variously colored and marked with a purple midrib. The open perianth is wheel-shaped. (See Fig. 143.) MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 184 Fic. 144. Etiolated culture of Mla uniflora. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN, 185 Tulipa patens Agardh. Tulipa patens etiolated in spring of 1900, developed leaves 30 to 60 cm. long with inrolled margins and torsions present but not so marked as in 7. sylvestris. The leaf from the lowest internode 7 cm. above the bulb was about 2 cm. wide at base and sheathed the second and third leaves. The second leaf arose from a node 4.5 cm. above the first and the third arose from a node 1 cm. above the second. The pedicel of the flower was about 6 to 8 cm. long, the perianth segments were I to 1.2 cm. long and were of a pale yellow. The stamens were of equal length and deep yel- low. The pistil was about 1.4 times the length of the stamens. The pedicels reached a length of about 2 cm. and the floral organs slightly larger than the normal in some instances, being apparently perfect except for blanching. Tulipa sylvestris L. The leaves were 30-33 cm. long and trailing in etiolated specimens grown in 1900, and marked torsions were exhibited. The margins were tightly inrolled nearly half way to the center, and the entire blade was twisted tightly into a roll in which only the lower, outer surface was visible. The new bulb was formed laterally to the old one in a manner characteristic of the normal, both sending down long offsets. No flowers were developed. Vagnera stellata (L.) Morong. Etiolated specimens of Vagunera stellata a Ls beige grown in the dark chamber in April, 1900, “sf showed a length of stem of about 55 cm. °°)" which was equal tothat of thenormal. The Fic. 145. Etiolated culture leaves were about 5 cm. long in the etio- % "##7¢r@ stellata. lated and 12 to 15 cm. inthe normal. The upper part of the stem became horizontal in the normal, but remained upright in the etio- 186 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. lated. The leaves of the etiolated specimen soon perished, but the development of the inflorescence progressed so far that some of the terminal flowers had opened in a manner apparently normal. The rootstock remained sound and healthy. Viola obliqua Hill. Specimens of a violet native to the Garden were taken from the soil in March, 1900. This is an acaulescent species which ordinarily Neu Fic. 146. Viola obliqua. A, epidermis of normal petiole. JB, epidermis from etiolated petiole. C, epidermis from normal lamina. D, epidermis from etiolated lamina. Z£, etiolated specimen. sends only its petioles and peduncles above the soil. The petioles of the etiolated specimens attained a length about double that of the MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 187 normal. The petiole at the base of the lamina was curved in such manner that the lamina was held pendant in an inverted position 1n the earlier stages of growth. With the growth of the petiole, this curve became accentuated until finally the tip of the lamina was projected upward, the petiole having curved through 360°. The epidermal cells of the etiolated petioles measured about 280 by g, and of the normal about 65 by 9. The stomata were open and functionally normal. The thickness of etio- lated and normal petioles was about the same. The laminae were rolled with the edges over- lapping. Some of the stomata are functional but the greater number are not differentiated. Viola rostrata Pursh. Specimens of Vzola rostrata were placed in the dark chamber in January, 1900. The shoot reached an extreme length of 18 cm. and the petioles of 6to 10cm. The laminae were not unrolled and were held pendant by a curvature of the petiole at the base of the lamina. In transverse section the epidermal cells were seen to be muriform and the mid- dle of the laminae consists of four or five un- differentiated parenchyma cells with some air- spaces. The stomata did not open. The cross section of the petiole showed eight to ten fibrovascular bundles with annular, spiral and scalariform ducts present. The cortex was composed of twenty layers of large cells, equal to about half of the diameter of the pith. Small intercellular spaces were to be seen in the cortex. A subepidermal layer was slightly thickened. The epidermal cells were slightly papillose in places. No distinct cambium Baa pr agin) haere 2 PS ep i e trata, etiolated shoot. ring was formed. The stipules of etiolated specimens were about 4 by 7 mm., while in the normal they are but 3 by 1.5, thus showing an increase in size in darkness. The normal stem had a cortex about equal to the pith in thick- ness and a heavy pericycle. A cambium layer was present in the 188 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. normal. The subepidermal cells were well marked and large air spaces were to be seen between them and the epidermis. The development of the xylem scarcely exceeded that of the etiolated. (Fig. 147.) Woodwardia radicans Sm. Rootstocks of Woodwardia placed in the dark room in 1g00 show a succession of stalks 25 to 30 cm. long and 3 to 4 mm. thick, bearing a few brownish scales which fell off later. The laminae and its branches remained as tightly rolled cylinders, which showed a distinct tinge of green, but which began to decay with no indications of opening. In its development it agreed fairly well with other Polypodiaceae. The normal specimen has a leaf with a stalk 20 to 25 cm. long and passing into a rachis with a length at least 50 per cent. greater. The pinnae are widely spreading, are 20 to 30 cm. from tip to tip. The etiolated specimens therefore show only a development of the stalk perhaps slightly elongated beyond the normal, with the entire foliaceous portion inactive. ADDITIONAL OBSERVATIONS. Acer rubrum L. A young tree of the red maple was brought into the dark room in November, 1901, and buds began to elongate on the lower part of the main stem early in the following May, followed later by the activity of others over various portions of the main stem and of the branches. The older etiolated stems reached a length of 15 to 65 cm. by July 22, and were about twice the thickness of normal twigs and shoots of the same tree formed during the previous season. Juvenile sprouts from the bases of young trees growing in the open, however, during the early summer, developed stems fairly equal to the etiolated ones, both in length and thickness. The etiolated stems were but weakly erect, soon falling over by their own weight where- upon the apical portions curved upward apogeotropically, giving the stems the appearance of trailing, and reminiscent of Acer circinatum. The normal branches of the tree in the dark room during the previous season in the open air, and of other trees in the open developed MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 189 about 2 to 5 internodes of a thickness not more than one third of the etiolated, and a total length of not over 5 cm., the maximum length of single internodes being less than 5 cm. Etiolated branches developed 6 to 8 internodes, or about the same as juvenile sprouts, the maximum length of the internodes being about 14 cm., which was double that of the juvenile sprouts. After the above growth had been made in darkness, the terminal buds perished, and activity was generaliy begun by the buds on the basal portion of the etiolated twigs, although some were developed on the terminal portions. It was noticeable that the greater number of buds on etiolated twigs that awakened were exposed to the occasional illumination of the gaslight by the aid of which exami- nations were made. In one instance an etiolated shoot showed a development of all of the main axillary buds on the illuminated side, and none on the other. The etiolated twigs bore pairs of opposite leaves, the petioles of which had a length of about 2.5 to 4 cm., and the small laminae measured 2 by 1.5 cm. being extended, and about one sixth of the normal size. (See Fig. 148.) Fic. 148. Acer rubrum, A, etiolated branch with leaves. B, normal greenleaf. The anatomical changes which may be ascribed to the effects of etiolation in Acer were more nearly parallel to Cornus than to Quercus or Hicoria. ‘The subepidermal layers of cork were present, and the formation of lenticels had begun in the basal internodes of the etiolated stems. Such lenticels were larger and more numerous 190 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. than in the stems of old trees in the open, but bore a general re- semblance in occurrence and form to those on juvenile sprouts. The walls of the epidermal and underlying tissues of etiolated twigs were slightly tinged with brown and the reddish cell contents of the normal epidermis were entirely lacking. The outline of the cross section of the normal twig is distinctly angular while in the juvenile and etiolated stems it was nearly circular. The subepi- dermal corky layers were present in the juvenile, adult and etiolated branches, the underlying cortex being thickened collenchymatously, pitted, and containing chlorophyl in the two normal forms, while in the etiolated the cortical cells were but slightly thickened, being flattened radially, with some intercellular spaces. The etiolated twigs showed, but a faint development of bast fibers, which with the lack of development of the collenchyma, must account for the mechanical weakness of such stems. The cambium layer is well marked in three kinds of branches, the wood cells and vessels show- ing larger lumina and thinner walls than the normal, although not so large as in the juvenile forms. The same may be said of the pith. The epidermal cells of the normal twigs of juvenile, and adult sprouts and twigs show a length parallel to the long axis of the branch fairly equal to the width, being somewhat irregular in out- line, while in etiolated examples these elements are drawn out into more nearly regular rectangles as seen in surface view, being about six times as long axially as tangentially. The tangential width of the epidermal cells was about the same as in normal adult branches. The dorsal surfaces of the leaves showed stomata which were open when examined in water, and appear to be functionally active. The duration of the leaf did not exceed twenty days. Trees beginning activity in the dark room in May, still bore etiolated shoots in various stages in the following September. Jost cultivated some species of maple in the dark room in the winter of 1891 and 1892, and found that some of the buds of young trees developed into elongated etiolated shoots. The excess of growth in length was not so marked as in Aesculus, however. It was noted that some secondary thickening, or the formation of an additional ring of wood, was seen near the base of the etiolated shoot in the old stem.’ 136 Jost, L. Ueber Beziehungen zwischen der Blattentwickelung und der Gefassbil- dung in der Pflanze. Botan. Zeitung, 51: 108. 1893. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. IgI AEsculus Hippocastanum L. Seeds of the horse chestnut placed in the soil germinated in the control chamber, and in the dark room in the following May. Nor- mal seedlings sent up a stem in which only the basal internode de- veloped a length of about 11 cm. and a diameter of about 9 mm. at the base tapering to 4 mm. at the summit. The normal seedling with a shoot consisting of a single internode on July 22, bore a single pair of quinate leaves and a strong terminal bud. The normal internode was somewhat angular in outline and of a deep green color. (See Fig. 149.) On July 22 the single etiolated seedling on hand had developed a stem 50 cm. in length consisting of ten internodes, the terminal one Fic. 149. ALsculus Hippocastanum. Normal seedling. of which had made about half of its probable ultimate growth. The basal internode was 12 cm. in length, and with a diameter of 7 mm., thus exceeding the normal slightly, both in length and thickness. This, as well as the other etiolated internodes, was compressed in the plane of the opposite leaves. The leaves were represented by pairs of sessile bracts with broad clasping bases and ciliate margins wholly unlike the foliar organs developed on the seedling. It is to be 192 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. noted that the first pair of leaves in the seedling in this plant are truly foliar, and that these bract-like organs resemble nothing more than the cataphyllary leaves of the older stem. It seems probable that these bracts may be considered as the leaf-bases and they per- sist only a short time, being alive only on the second internode from the apex of the stem. Numerous lenticels 1 to 3 mm. in length and half of that in width were to be seen, over the entire etiolated stem. The epidermal cells of the etiolated stem had collapsed in the older portions, and were generally rectangular in surface view, being two or three times as long as broad. In some instances, however, the ends were acutely oblique. The phellogen underneath the epidermis comprised five to seven layers, and the outer cortex seven to nine layers, the latter being composed of elements heavily thickened collenchymatously, and flattened radially. The inner cortex was also similarly compressed, but the walls were not so heavily thickened. The bast fibers were only slightly thickened. Internally to these cells was found a mass of irregular thin-walled elements which shaded gradually into the cambium, which in turn passed gradually into the woody tissue. The vessels and tracheids showed larger lumina than in the normal. The pith was composed of perforate parenchyma richly loaded with starch, and it is to the exaggerated growth of this tissue that the excessive thickness of etiolated stems is to be ascribed. The root system of the etiolated seedling was somewhat sparse, and the cotyledons were turgid and still contained some starch and other food material. The normal stem of seedlings was furnished with a phellogen much like that of the etiolated, but the epidermal layer showed a number of outgrowths in the form of short-pointed hairs, which were not seen in the etiolated. The outer cortex is thickened collenchym- atously, and contained much starch and chlorophyl, while the inner layer.was composed of elements with much thinner walls. The bast fibers were heavily thickened. The formation of some secondary tissue had begun on July 22, and the medullary rays were diverted from the radial position as if torsions had been set up. The outline of the stem was obtusely angular. The root system was more profusely branched than in the etiolated example. A single seedling AZscudus was allowed to germinate in the con- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 193 trol chamber in full illumination until the plumule of the young shoot was almost disengaged from be- tween the cotyledons, and the curved portion of the stem already exposed bore a pair of small quinate leaves. The plantlet was then removed to the dark room and allowed to continue growth. Not only did the leaflets of the first pair of foliar organs continue growth, attaining nearly double the size shown at the time of their removal to the dark room, but all of the leaves borne on the etiolated and erect stem a month later also had five small leaflets which were en- tirely lacking from perfectly etiolated seedlings. It is thus to be seen that the stimulation of light upon the basal portion of the young shoot induced the de- velopment of laminar members on internodes which not only were not exposed directly to the light, but which were not developed until some time later. The evidence afforded by this demonstration also bears most strongly against the acceptance of any etiolation results in which light is excluded from a portion of the plant only. ‘ Small trees of this species were cultivated by Bon- nier in a continuous illumination from electric arcs of such intensity that oxygen was given off at one-third the normal rate by aquatic plants. Under such condi- tions the shoots did not attain normal size and elon- gated more slowly than under the usual conditions of alternating daylight and darkness. True foliar leaves were produced which were very green. No differen- tiation of bark or lenticels ensued, and the cortex was thinner than in the normal, as well as the central cylinder. The cortex was differentiated into two zones as it appeared to do under both normal condi- tions and in absolute darkness, in the experiments de- scribed above. The sinuosities of the pericycle were less accentuated. The thickening of the pericycle was less marked, and the woody tissue was less perfectly Fic. 150. ALsculus Hippocastanum. Etiolated] seedling 60 days old. 194 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. developed. The greatest difference was to be seen in the secondary wood, which consisted of much smaller elements with thinner walls. The perimedullary layer was perfectly developed and the pith was greater than in the normal. The influence of weak continuous illumination is thus fairly similar to that of darkness, so far as the central cylinder is concerned. The differentiation of the cortical and epidermal systems is carried much farther in the etiolated specimen examined. It is to be recalled however, that Bonnier’ used small trees showing adult stems, while the stem described above is that of the seedling, which in the normal, consisted of the first internode. Apios Apios. (See page 42.) After the first series of observations on Afzos was made, oppor- tunity was afforded for an examination of the subterranean branches upon which the tubers are formed by the swelling of the apical por- tions of the internodes. ‘The earlier stages of the development of these formations was accompanied by the differentiation of a secon- dary cambium or generative layer in the pericycle, very similar to that exhibited by etiolated stems. The increase in the radial diam- eter of the cortex was not readily noticeable however in the tuber- forming stems. A subepidermal phellogen is formed early in the tuber-forming stem, but this does not take place in the etiolated, or in the normal aérial stem. Etiolated stems were free from trichomes, in contrast with the subterranean tuber-forming internodes, which bore these structures in great number. Fagus Americana Sweet. (See page 105.) Young beech trees from 30 cm. to 3 meters in height were brought into the control chamber and dark room in November, tg01. No activity was shown until July, 1902, when several buds on the smaller plants began to elongate, producing branches, which in some instances reached a length of 3 to 8 cm. by September 1, 1902. Such etiolated branches consisted of 3 to 6 internodes varying in length from 4 to 15 mm. and bore minute leaves on the basal por- tions and larger foliar organs on the terminal portions. The maxi- mum size of these leaves was 8 cm. in width and 12 cm. in length. The leaves, as well as the stems, were silky-hairy, the trichomes hav- ing much the normal appearance. 137 Bonnier, G. Influence de la lumiére électrique continue sur la forme et la struc- ture des plantes. Rev. Gen. d. Bot. 7: 253, 254. 1895. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 195 Buds were formed on the calluses over cut surfaces in a few of these small plants, and these, together with some of the awakening dormant buds, made a growth of a centimeter or less, then went into a resting condition being loosely covered with silky-hairy brown scales (see Fig. 152). The above observations are fairly in accord with those made by Jost’ upon Fagus sylvatica (?). Jost found that darkness hindered the development of beech buds, and that when. a few buds were exposed to the light by the extrusion of a branch from the dark room, the others in darkness showed greater activity than the buds of plants wholly confined in darkness. The first crop of buds developed in darkness were but 3 cm. in length, and a second series awakening later made a growth of about 8 cm., bearing leaves about 5 cm. long. Jost believed to have demonstrated by his series of ‘ par- tial etiolations ” that some substance formed in light is necessary to the growth of buds of the beech. The larger trees used in my own experiments were trimmed by having a few of the larger branches cut away, and the only growth shown by such trees consisted in the formation of buds and branches from the calluses formed over the wounds. Thebudsinsomeinstances F'G- 151. Magus sylvatica. A, nor- did not elongate more than a centi- oe es Sees gale tap Si aks meter before going into a resting condition, while in others branches 18 to 20 cm. long were formed, consisting of 5 or 6 internodes, of a length of 2 to 5 cm. and bore leaves which fell away after attaining a length of about 5 cm. The stems and leaves were silky with appressed hairs. Numerous lenti- cels were formed. Normal stems of trees in the open air made a growth of 6 to 11 cm. in the season of 1902, and about 5 or 6 internodes were formed with lengths varying from 2 to 42 mm. The internodes of the 138 Jost, L. Ueber den Einfluss des Lichtes auf das Knospentreiben der Roth- buche. Ber. d. Deut. Bot. Ges. 12: 188. 1894. 196 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. etiolated branches are thus seen to be excessively elongated, a fact accounting for the superior length of these members. The normal stem of the current season’s growth showed a col- lapsing epidermis, an underlying collenchymatous layer of cortex, and an inner cortex with larger elements and thinner walls. Both regions contained chloroplasts. The bast fibers of the pericyclic region were grouped in such manner as to give the usual crescentic transverse section, being separated by the external continuation of the rays, which also separate the bundles widely. Some reddish coloring matter in the outer layer of the cortex was almost masked by the brownish tinge of the walls of the epidermis. Etiolated stems showed structural divergences of degree only. The phellogen, collenchymatous layer and inner cortex were distinguishable. The cortical cells were furnished with thinner walls and contained so much reddish coloring matter that the etiolated stems had a decided pinkish tinge. The bast fibers, which are grouped in about twenty clusters in the normal, appeared in about forty smaller groups in etiolated stems, the crescentic outline of the trans- verse section appearing more flattened. The cause of this apparent multiplication of the clusters of bast fibers is not clear. It might be ascribed to the non- Fic.1s2. Branch Gevelopment of some of the fibers, thus breaking the of Fagus Ameri- normal clusters into smaller groups, the elements hav- cana, which has jing thinner walls than in the normal. Cambium was been in dark room ° . 8 months. A,nor- Present in etiolated stems and the medullary rays were malbudwhichhas not so wide as inthe normal. Less thickening oc- notawakened; B, curred in all of the woody tissues. Stomata were a a. present on the dorsal (lower) surfaces of the etiolated Bioeeeat leaves, although nothing but the most minute open- ing could be detected between the guard cells. Bonnier’ cultivated Fagus sylvatica in continuous illumination in the same manner as A Fsculus (see page 191), and found that phellogen was not formed under such treatment. The number of sieve tubes was less than in the normal, and the rows of vessels and tracheids were seen to be more closely crowded together by the inferior 139 139Bonnier, G. Influence de la lumiére électrique continue sur la forme et la struc- ture des plantes. Rev. Gen. d. Bot. 7: 300. 1895. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 197 development of the medullary and intravascular parenchyma as in etiolated stems of /. Americana. Ibervillea Sonorae Greene. A number of large woody tubers of “ guarequi”’ were collected from the sandy plains around Torres, Sonora, Mexico, in February, 1902. Some were placed in the control house and others in the dark room in May, 1902. Adventitious buds on the upper surfaces of the irregular tubers soon began activity, sending up vines 3 meters in height and climb- ing by means of extra-axillary tendrils after the manner of the Cucurbitaceae. These tendrils were extremely sensitive and reached a length of about 6 cm. The internodes of the glabrous normal stems were about 6 to 8 cm. in length, and the peti- oles about 4 or 5 cm. Etiolated stems did not reach a length in Gxcess Of 50 -Cmi, a limited growth perhaps partially due to the high humidity of the dark room. The plant is found to flourish best under the same con- ditions as_ subtropical cacti from the most arid regions of Amer- ica. The internodes of the etiolated stems were fairly normal in length, except the basal ones which were much elongated, but were about double the thick- ness of green stems. Etiolated petioles were about a half longer than the normal. Tendrils were present, but did not attain the Fic. 153. Normal branches of Jbervillea Sonorae. 198 MEMOIRS OF. THE NEW YORK BOTANICAL GARDEN. normal length, soon becoming curved as in normal mature organs, but did not assume the irregular. corkscrew form of these or- gans. Etiolated tendrils were irrita- / | ble to contact in the stage when they g had reached a maximum size, but the \ y resulting curvatures carried the tips through only a few degrees, except \ with continued contact, and in a few instance these organs succeeded in encircling a support. If the irritable p surface was placed in contact with a support one or two turns would be j made around it, but the free portion did not assume the corkscrew form. If stems which had begun growth in light were removed to the dark room the first etiolated tendrils developed subsequent to the removal were larger than if the entire growth had taken place in the dark room, affording an- other example of the endurance of the stimulating effects of light in partial etiolations. | The excessive thickness of etio- lated stems was found to be due to the Fic. 154- Entire etiolated shoots greater size, and perhaps some multi- of Jbervillea Sonorae. B, B, sup- Sy lot Sah Odidapen ty a tangil at A: plication, of the parenchymatous ele- ments in the stele and cortex. The tips of the stems as well as the petioles were apogeotropic. Lycopodium lucidulum Michx. A number of bulblets of Lycopodium lucidulum in the germinat- ing stage were found near Cold Spring Harbor, L. I., about the middle of July, 1902, and representatives of the various stages of development were preserved, while some in a resting condition were brought in and placed in the dark chamber. ‘These structures are composed of several thickened fleshy leaves, and are formed in the axils of stem leaves, being in fact modified branches, and containing much chlorophyl. About a month after confinement in the dark MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 199 room, the main axes of the gemmae began to elongate, and sent up stems about 15 mm. in height, which were fairly equal to that of nor- mal specimens. The etiolated stems were almost devoid of color, but a faint greenish tinge was noticeable in the leaves. The cells were larger in all measurements and the stelar tissues less per- fectly differentiated. The etiolated stems were slightly thicker than the normal, and bore about five leaves, which were appressed and much narrower and shorter than the normal, being bract-like. The distance be- tween the leaves was greater than usual, correspondent to the internodal elongation Fic. 155. Lycopodium lu- of the higher plants. One or two roots had “##/#”. A, normal plantlet been formed by some gemmae, and the lat- ter has begun to assume a yellowish aspect as if the chlorophyl were breaking up. The growth of the etio- lated plants continued for five weeks from the time of germination. arising from sprouting gem- ma; &, etiolated plantlet. Smilax Beyrichii Kunth. Tubers of Smzlax from Florida collected in October, 1901, were placed in the dark room and control chamber in January, 1902, and began growth in May. On October 7, 1902, etiolated stems had been formed that had a length of 80 to 90 cm., consisting of 18 to 20 internodes of a length of 2.5 to 4.5 cm. Normal stems had formed a much larger number of internodes which made up a total length of 2 to 3 meters, the separate internodes measuring about double the etiolated members. Numbers of weak prickles half of the length and thickness of the normal were formed in darkness, in addition to which some papillar projections were formed on the basal etiolated internodes which were doubtless rudimentary roots. Leaves were represented on the etiolated shoots by sheathing bracts something larger than the normal, being over a centimeter in length, and bearing a narrow lanceolate body at the apex a few millimeters in length representing the petiole and lamina. Tapering papillae on either wing of the base near the lamina represented the ten- drils. These organs arose from the extreme margin, and had the appearance both in the etiolated and normal organs of being branches 200 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. of the hypopodium although designated as not{homologous with any part of the leaf by Goebel.’ B Fic. 156. Smilax Beyrichit. A, normal immature leaf with tendrils, natural ize. B, etiolated leaf, consisting of an exaggerated basal portion, bearing atrophied tendrils, and a rudimentary lamina, 4. Etiolated stems were thicker than the normal by reason of the in- crease in the size of the cortical cells, which were also furnished with thinner walls, the collenchymatous thickening to be found in the inner portion of this region in green stems being lacking. The numerous fibrovascular bundles were not so strongly developed as in the normal. The newly formed smaller bundles to be seen in the cortex of normal stems were not found in the etiolated stems. 140 Goebel, K. Organographie der Pflanzen. Part II., p. 432. 1808. GENERAL CONSIDERATIONS. Modes of Influence of Light upon Plants. — The relations in which plants stand to radiant energy are so diverse, and the several effects of light and darkness upon plants so intimately interlock that a brief statement of the currently accepted conclusions upon various phases of the subject will be a necessary preliminary to a critical discussion of the records of researches cited in this memoir, and of the new facts which have been brought out in my own investigations. The term light is used in the present paper to denote waves of radiant energy included in the spectrum between the infra-red rays with a wave length of .760 w and the supra-violet with a wave length of .397 pu Sunlight has been found to exert analytic, synthetic, isomerismic, polymerismic and catalytic effects upon the chemical substances which may be isolated from the protoplasm of plants. It is fairly probable however that no such extensive action ensues when the various substances and compounds are bound up in the metabolic system of the living cell. At the present time evidence is at hand to show that certain synthetic effects, such as the union of oxygen with some portions of the protoplasmic substances, may be produced in the organism, and that it is to this cause that the destruction of bacteria in sunlight may be ascribed. It has also been found that light exerts a direct influence upon the enzymes in protoplasm. In the earlier stages of such action the effect of the red, orange and some blue rays seems to increase the amount of enzyme present, and later a disin- tegrating effect was exerted by these rays, the violet and ultra-violet being constantin such analytic or catalytic action. Tothe violet and blue-violet rays is also to be ascribed the oxidizing action noted above as well as the disintegration of chlorophyll. It is of course entirely probable that the action of light may set up chemical processes in the plant is in a manner entirely stimulative, and independent of any communication or transformation of energy. So far as known facts are concerned, the only method by which light might exert an effect 141 MacDougal. Practical Text-book of Plant Physiology, 110. 1gor. 202 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. upon growth would be by the decrease of the enzymes participating in the various stages of the process. That the rapidity of growth becomes less under illumination in many plants is beyond all doubt, but that such effect is due to the direct paratonic action of radiant energy is a matter that will come up for further discussion in this paper. '” The stimulative action of light in chemical processes is well illustrated in the matter of formation and maintenance of chlorophyl. Protoplasm is capable of constructing this complex and unstable substance in darkness, and of maintaining it in a fairly normal con- dition for periods extending over many months. In many species however, the process of formation is not set up except under the stimulation of light, and the entire spectrum appears to participate in the stimulation. Simultaneously, however, the upper end of the spectrum exerts a disintegrating action, which is probably a direct chemical effect of the same character as that by which enzymes are broken down. Radiant energy in the form of light being the most important source of energy of plants, it enters into manifold physiological relations with the shoot. The plant has coérdinately a number of capacities for adjustment to various phases, degree of intensity, and angle of incidence of the rays. An added interest is attached to this feature of the subject from the fact that the capacity for these adaptive reactions have been formed to respond to associated characters rather than to the exact portion of the spectrum with which the action of the plant is concerned. ‘Thus the phototropic reactions of plants are induced in greater part by the more refrangible blue violet rays, the resulting movements being for the direct purpose of placing the surfaces of the chlorophyl-bearing organs at a proper angle for the economical and safe reception of the orange red rays. It is true of course that the two kinds of radiations are almost invariably associated so far as the experience of the vegetable world is concerned, but the fact remains that the stimulation in question is one of association. A further ex- ample of such associations in irritability is to be found in the sensi- bility of reproductive organs to light. Seeds and spores are benefited directly in a few instances only, by exposure to light, yet the conditions for the distribution of seeds and spores are more commonly favorable 142 MacDougal. Critical points in the relations of light to plants. A résumé read before the Society of Plant Physiology and Morphology, Baltimore, Dec. 28, 1900. Abstract in Science, 13: 252. 190T. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 203 when the reproductive organs are held up in sunlight. Here the phototropic response is made to a stimulus ordinarily associated with a series of complex conditions embracing currents of air, activities of animals useful in dissemination, water, etc., which are actually necessary for the profitable and successful dispersal of the propa- gating bodies. Even the germination of a large number of seeds and spores in light only may be regarded:-as a similar association of a stimulus with other vegetative conditions. It is true of course that spores of certain pteridophytes must have light-exposure to enable the chlorophyl-apparatus to construct building material for germina- tion and growth, but in the larger number of instances illumination acts simply as a signal indicative of the presence of other necessary factors. The intensity of light necessary to constitute a phototropic stimulus varies enormously with different species, and with the developmental state of the individual. Using a normal candle burning 7.78 grams of paraffine per hour at a distance of one meter as a standard it has been found that an illumination of .00033 to .o6 meter candle con- stitutes the minimum in seedlings of the most delicately organized species examined. The optimum effect in curvature is obtained in the same plants with an intensity of .11 to .44 meter candle, and these intensities must be increased a hundred to a thousand times to reach the maximum. Increase of the intensity beyond the maximum may result in changing the character of the response in such manner that the organism will curve or move away from the source of the rays. The more refrangible rays are chiefly active in such effects, and the amount of increase in the intensity necessary to constitute a stimulus is not more than 18 per cent. in some instances. In addition to the reactions described above the plant shows other forms of response to intensities of illumination by photeolic and pho- tolytic movements which bring the cell-constituents into adaptive rela- tions with radiant energy by which injurious activity of the trans- piratory and other functions are avoided. All efforts to establish a connection between the action of light on the enzymes or other cell contents as a primal and direct cause of the reactions in question have failed. Light has undoubtedly exerted a predominating influence in the development of the prevailing types of vegetation, the form and structure of the body and its members being largely determined by 204 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. the experience of the plant with respect to the nature, intensity, and direction of the rays which have impinged upon them. It would hardly be justifiable to say that light has originated or caused dorsiventrality in the vegetable kingdom: the causes must lie deeper and be infinitely more complex. Light of course has been one of the complex conditions to which dorsiventrality is a primary and basic developmental adaptation. Given the capacity of dorsiventral or- ganization or development however in individuals, and its occur- rence is often directly subject to the determinative and inductive action of illumination. It is to be said in this connection that the use of the term ‘‘ directive ” to designate morphogenic influences exerted by light, as has been done by Goebel, is withal, not in harmony with current usage, this term having long been applied to the action of the rays in inducing phototropic, photeolic and photolytic movements of the axes of the shoot and its members or of the body in general.” Chief among the determinative influences exerted by light are to be mentioned the anatomical differentiations which may ensue as a result of its action, by which an organ may become dorsiventral and the positions of the dorsal and ventral surfaces altered. It is well known however that any form of dorsiventrality once assumed by the body or any of its members may not be changed, or reduced by altered conditions of illumination. A second phase of induced bilaterality is that in which organs are induced or suppressed upon comple- mentary surfaces. This form of symmetry is often directly reversible by changed conditions of illumination, particularly among the thallus- like forms of. the lower plants. Not only does the illumination de- termine the relative position of the dorsal and ventral surfaces, but it may also guide the polar differentiation, the apex and base of plant- axes being formed in developing spores with respect to the direction of the rays. The association of different developmental stages of a plant with various intensities of illumination and the hindrance of procedure in every other instance in which the intensity of the light is beyond certain limits is a somewhat more complicated and delicate mani- festation of the determinative influence of light upon the induction or suppression of organs. The actionin question must be purely stimu- lative in its character, and for every stage an optimum, maximum and minimum of intensity might theoretically be established. 143 Goebel. Influence of Light. Organography of Plants. Eng. Ed., 227-259. 1900. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 205 The length of the main axis and its branches, and the superficial extent of foliar organs have been found to depend upon the intensity of the illumination in a large number of species. Such variations in stature are coupled with corresponding alterations in internal struct- ure. Adaptations of this character may be generally attributed to responses to the transpiratory conditions set up and to various mechanical factors. The marked features of alpine types consisting chiefly of dwarfing of the shoot and additional checks upon transpira- tion may be ascribed in part to the increased intensity of the illumi- nation at higher levels due chiefly to the lessened absorption by the atmosphere of the blue-violet end of the spectrum, and to the altered moisture-relations by which the danger of drying out is much greater than upon plants at lower levels. The change of the light-conditions entailed when aérial members are converted functionally into underground organs is over-balanced by the altered mechanical conditions, so that only a part of the differences may be ascribed to altered illumination. The character of the stresses to be borne are so altered that the develop- ment and arrangement of the me- chanical tissues are necessarily dif- ferent from those of homologous aérial stems. Then again, the humidity of the medium is so much greater, and the transpiratory conditions so dif- ferent that the epidermal surfaces and subepidermal tissues are widely variant from those of aérial stems and branches. The terms ‘‘ light” and ‘ illumin- ation” have been used in the preceding ; ; Fic.157. Ranunculus Asiaticus. discussions to allude to the ordinary 16D, leaf developed in discontinuous exposures of plants to daylight of an normal illumination ; 16C, leaf de- Siena Aer aiehe local en veloped in continuous electrical il- y pee aoe ~ lumination. 16N, etiolated leaf. vironment and longitude, and alterna- after Bonnier. ting with the nocturnal periods of dark-. ness. A reviewof the records of investigations cited in the opening section of this book brings out most conclusively that the greater major- 206 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN, ity of plants exhibit divergences from normal growth and development whenever cultivated under conditions in which the customary occur- rence of illumination and darkness is varied. The effect of one departure, in which plants are cultivated in complete darkness, has been the subject of an enormous number of investigations as pre- viously indicated. The amount of experimental evidence at hand bearing upon the influence of continuous illumination upon plants is comparatively meager, the most important contribution to the subject, from a botanical point of view, having been made by Bonnier in 1895 (see page 27 of this Mem- oir) The continuous electric illumination to which Bon- nier subjected the plants used in his experiments was of suchintensity that a liber- ation of oxygen from aqua- tic plants under the same conditions took place at about one third the normal rate at which the process ensued in sunlight. Par- 4 we N ticular emphasis is to be Vi, SY gb laid upon this fact in view zips of the well-grounded con- ie tc a iN 1p clusions, to which refer- ence is made above (p. 204), that the separate Bw stages of development of t yo a plant, or of the different yy = organs, are associated with i certain intensities of illumi- Fic. 158. Carpinus Betulus. 1C,leafybranch nation. An intensity below from small tree in continuous electrical illumina- the normal of fu}l sunshine tion. ID, leafy branch in normal discontinuous T & - illumination. After Bonnier. would be favorable for cer tain action and unfavorable for others, and it is to this continuous and long-continued con- 144 Bonnier, G. Influence de la lumiére électrique continue sur la forme et la struc- ture des plantes. Rev. Gen. d. Bot. 7: 241, 269, 332, 407. 1895. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 207 dition uniformly favorable to the growth of certain organs and tissues, that the aspect of plants grown in uninterrupted illumi- nation must be ascribed rather than to any green ‘ etiolative ” effect supposed to be produced. Thus in continuous exposure to illumination by Bonnier, a much greater development of chloro- plasts and formation of chlorophyl ensued than in the normal; the bark, and practically all of the parenchymatous tissues containing chlorophyl even to the central pith. The tissues of the leaf did not reach the extreme stages of differentiation characteristic of normally exposed organs and the same may be said otf the stem in which the parenchymatous tissues showed but little differentiation ; bark was not developed, and endoderm was not always distinguishable. In the case of the hellebore special alterations ir the development of the endoderm and pericycle were noted. Because of the general arrest of the morphological development of the stem, which in the very na- ture of the plant must be similar in some respects to those resulting from etiolation, or any other cause retarding development, it may not be concluded that the two processes are similar. So far as the results of Bonnier may be interpreted, the exposure to the illumina- tion in question showed no especial feature due to the continuity of the illumination, but may rather be ascribed to the accentuated effects of an illumination of low intensity. Schiibeler '” transported a number of cultivated and native species from lower latitudes to places in the northern part of Scandinavian peninsula where they would be subjected to a continuous illumina- tion during a period of two months, during which the sun remains above the horizon in that locality. It is to be noted that the intensity of such illumination is far below that of temperate and tropical local- ities. The vegetative period of such species was notably shortened, and the seeds produced were larger than the average. ‘The effect of such continuous illumination was to cause an accumulation or increase in the amount of certain aromatic and flavoring substances, and to increase the amount of coloring matter in leaves and flowers, while diminishing the amount of saccharine matter present. A specimen of Acacia lophantha did not show any of the usual 145 Schiibeler. The effects of uninterrupted sunlight on plants. Abstract in Na- ture, 21: 311. 1880. 208 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. diurnal adaptive movements of the leaflets according to this account during the two-months-long day.” Fic. 159. Helleborus niger. YD, section of basal portion of petiole of normal leaf. C, section of basal portion of petiole grown in continuous electrical illumination. E, epidermis. CC, cortical tissue. L, bast fibers. B, wood cells. en, endodermis of entire stele. E’, endodermis of separate bundles in etiolated petioles. CC’, pericyle. CC”, parenchymatous cells in position of medulla. After Bonnier. The influence of illuminations of a duration and intensity dif- ferent from the normal in the culture of economic plants has received some attention from physicists and horticulturists. Siemens’ pub- lished a report of some experimental observations in 1880, in which the comparative behavior of plants in continuous darkness, normal daylight, normal daylight supplemented by nocturnal illumination 46 Wiesner, J. Untersuchungen ueber den Lichtgenuss der Pflanzen im Ark- tischen Gebiete. A. d. Sitzungsber. d. kaiserl. Akad. d. Wiss. i. Wien, 109: Abth. 1, May, 1900. MT7Siemens, C. W. On the influence of electric light upon vegetation and on certain physical principles involved. Nature, 21: 456. 1880. See also Proc. Roy. Soc. 30: 210-230. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 209 from electric arcs, and electrical illumination for six hours daily, with confinement during the remainder of the day in a dark room, were described. The light from the lamps was of 1,400 candle power, measured photometrically, and was of such intensity as to injure leaves placed within three or four feet, an effect probably due in part to the high temperatures set up. Experiments in which the normal daily illumination was supplemented by nocturnal electrical illumination, showed the most vigorous growth and greatest develop- ment, and the same effect extended to the flowers and fruit. Noth- ing in the results described could be found to support the theory that light exerts a paratonic effect upon growth. Ve i Age RST Fic. 160. Spinach (Sfénacéa olera-ea). A, normal plant. B, specimen grown n daylight supplemented by nocturnal electrical illumination. Redrawn, after Bailey. Deherain exposed a number of plants to continuous illumination from electric arcs in 1886. One series was cultivated in a darkened chamber, and another in a clear glass house. The lamps used were of a nominal candle power of 1,400 to 4,000 and the illumination (with the accompanying temperatures) was sufficient to produce many injurious effects upon the plants used. When the lamps were shaded by glass globes, less injurious effect was seen and some etiolative attenuations of stems and petioles were observed.“ Me Ann. Agronom,; 7% §51:~ 1881. 210 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. L. H. Bailey has carried out extensive experiments upon the in- fluence of electric illumination of 2,000 candle power upon cultivated vegetables and flowers in which the normal daylight illumination was supplemented by that derived from electric arcs during nocturnal periods of various lengths. The rays from a naked arc were injur- ious to many forms and in the case of spinach it seemed to induce the formation of flowers and seeds after the manner of certain other agencies. The action of the light from shaded lamps was gener- ally favorable to the growth of lettuce, while the effects on other plants were of advantage economically, or not,according to the portion of the body to be developed, and the general habit of growth. One of the most important results of the experiments by Professor Bailey “” was that of attenuations similar to the ‘‘etiolations” of Bonnier were produced (see Fig. 160). The rate of growth observed in the con- tinuous illuminations afforded no proof that light retards growth. A comparative study of the injured and uninjured plants by Row- lee showed that such leaves as those of coleus and_heliotrope were injured by the light from an arc lamp a yard distant, the effect of the light being to kill the epidermal cells and hairs. Thick, coriaceous, or succulent leaves with heavy cutinized external walls, such as those of Ficus elastica, Rhododendron maximum, Kalmia latifolia, and coronilla were uninjured by such exposures, doubtless owing to the screening effects of the heavy walls or cells contain- ing much water.” A series of experiments by Rane published in 1894 demon- strated that the light furnished by incandescent lamps 60 to 80 candle power did not give some of the injurious effects of arc lamps, and that the growth of foliage plants for food was accelerated by such illumina- tion. Flowering plants blossomed earlier and continued to form flowers over a longer period than under normal illumination. Spi- 9 Bailey, L. H. Some preliminary studies of the influence of the electric arc lamp upon greenhouse plants. Bull. No. 30, Cornell Univ. Agric. Exp. Station. 1891. Bailey, L. H. Second report upon electro-horticulture. Bull. No. 42, Cornell Univ. Agric. Exp. Station. 1892. ; Bailey, L. H. Third report upon electro-horticulture. Bull. No. 55, Cornell Univ. Agric. Exp Station. 1893. 150Rowlee, W. W. Effect of the electric light upon the tissue of leaves. Proc. 19th Annual Meet. of the Soc. for Promotion of Agric. Science, Boston, Mass., pp. 50-58, 2 pls. 1898. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 211 nach and endive went quickly into the formation of seed under the same condition. This series of experiments was also lacking in re- sults which gave any evidence that light directly retards growth." Corbett has recently published a paper upon the effects of an illumination derived from incandescent gas-light upon plants. The lamps furnished an illumination of about 560 candle power and a study was made of the influence at various distances. It was con- cluded that the effect of such light in supplementing the normal day- light produced heavier and taller specimens of lettuce, and induced faster growth of lettuce and spinach. Tomatoes produced flowers and fruits earlier than under normal ‘illumination, and lettuce and radishes developed seed stalks earlier than under normal conditions. The rate and period of growth were increased in lettuce and spinach by the use of the supplementary artificial illumination. Lastly, the proportion of sugar in solution in beets grown in such extended illumination was greater than in the normal, although the size of the beets was less. Asa general result the growth of the shoot, or the portion of it exposed to the light was greatly accelerated by the additional illumination afforded by the experiments.'” The entire life of the plant so far as the aérial organs is con- cerned is one of wide experience in alternating periods of daylight and darkness. ‘The results of the experiments cited above demon- strate with some certainty that increases in the total duration of illu- mination to which a plant is exposed, during its vegetative period, either by artificial nocturnal illumination, or by cultivation in Arctic regions results simply in a correspondent acceleration of the sea- sonal development of the plant, by which a greater amount of work is accomplished within a given number of days. The ex- tinction of the daily ‘‘ resting period” brings no distinct reaction so far as important anatomical features are concerned, although an ex- aggerated production of certain substances is found to take place. Neither is any retarding or paratonic effect to be seen as a result of this continuous illumination. 151 Rane, F. Wm. Electro-horticulture with the incandescent lamp. Bull. No. 37, W. Virginia Exp. Station. 1894. 152 Corbett, L. C. A study of the effect of incandescent gas-light upon growth. Bull. No. 62, W. Virginia Exp. Station. 1899. See also Flammarion, C. Physical and meteorological researches, principally upon solar rays, made at the station of agricultural climatology, Juvisy, France. Abstr. Exper. Sta. Record, 10: 103. 1898. 212 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. A modification of the normal conditions by which the customary nocturnal period of darkness is lengthened to extend completely over the vegetative period, and to include the entire possible development of the plant exercises much more marked and quite sweeping effects. In the first place all of the direct influence of light is lacking, and in the analysis of the results of such etiolations it is necessary to take into account most rigidly the general relations of every species to light, as well its mode of life, seasonal habit, and mode of nutrition with respect to the accumulation and use of reserve food material. The growth of a plant in darkness deprives it of the determinative and morphogenic influence of light in all of the various phases, and causes it to assume a stature wholly determined by its autotropic and geotropic reflexes and their correlations entirely uninfluenced by pho- totropic, or photolytic reactions. It is equally undeniable that etio- lation must create most serious disturbances in the nutritive system. The photosynthetic power usually exhibited by chlorophyllaceous organs is wholly lacking, and if the plant is autotropic in its method of subsistence it must prosecute its entire development by the aid of reserve food laid up in its storage tissues. The amount of this ma- terial, even in seedlings, is usually far in excess of that needed for the stage of development for which it is provided, but when the plant is forced to depend upon this supply by confinement in the dark room, for the construction of organs and tissues usually supplied from the foliar organs, variations may be expected. These variations may consist in partial atrophy, or non-development of the organs con- cerned, and of alterations in the differentiation of the tracts conduc- ting plastic material to and from the affected organs. The etiolative condition implies the establishment and maintenance of currents of plastic material by no means identical in volume, character, direction and location with those of the normal plant. Lastly, the relations of the body to water are most profoundly modified. The decrease in the formation of stomata, or the total failure of differentiation of these organs lessens the power of transpiration of the plant, and is followed of course by a much diminished movement of water and fluids in the body which must materially affect all translocation processes. In addition to these negative effects of continued confinement in darkness the probability is near that darkness exerts a direct effect per se upon the plant, an aspect of the subject which will receive some consideration in the following pages. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 213 It will be necessary to make a critical examination of the results of the observations described in the present memoir in order to deter- mine how far the separate factors enumerated above are to be con- sidered as responsible for the forms and activities of etiolated plants, and in order to test the validity of the various theories that have been proposed in explanation of the relations of plants to light and darkness. The manifestations to be considered include among other features alterations in the seasonal or periodic activity coupled with altera- tions in the duration or length of existence of the various members of the shoot. These departures from the normal mode of existence serve as a means of analysis of the economic value of the reserve supplies in seeds and other storage organs. It follows naturally that the form and general aspect of the shoot are greatly altered by a development in which the usual relation to light is disturbed, and that such divergences are accompanied by unusual methods of dif- ferentiation of tissues, which are developed in a manner markedly different from the normal, some being suppressed, others accentuated, and in some instances new tissues arising. Variations occur in the form, size, and number of the elements, the structure and character of the walls being materially different from the normal, while the protoplasts diverge chiefly in the character of the inclusions, and composition of the vacuolar fluids. Organs and members may be suppressed, or undergo a development of mass beyond the normal in a manner wholly determined by the general physiological relations of the species in question. The abnomalities may go even deeper and include variations in the dorsiventral organization of the plant, neces- sarily accompanied by alterations.in the character of the reflexes exhibited ; many of the more important forms of irritability being sup- pressed. The non-development of the various stimulative reactions is purely a loss of functional capacity in some instances, while in others the change from the normal is still more sweeping and embraces the non-formation of the tissues in which the power of reaction is ordinarily invested. The relations of light and darkness to reproductive organs and their products are so complex that an interpretation of the behavior of these mechanisms may be made only after a consideration of the mode of formation of the reproductive bodies, and of the method of their dissemination, as well as of the general features of the nutrition of the plantlet arising or aevelope from such bodies. 214 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. A general examination of the results at hand may be made by a recapitulation of the principal facts disclosed as to the etiolative and other reactions exhibited by the different members and organs of the bodies of the simpler and higher plants. Stems and main axes in general exhibit the greatest diversity of behavior in the matter of growth in length and thickness, final ex- tension and duration under etiolative conditions. The least devia- tions from the normal occurs in species in which the main axis is subterranean or is ordinarily shielded from the direct action of light. Such plants usually send up leaves and flowers during the vegetative season with die back periodically, to the underground or shaded por- tion. The aérial organs thus produced, leaves, inflorescences and branches, undergo etiolations that will be described below, and their altered development is not with- out correlation effects upon the axis of the plant not directly ex- posed to the action of the rays. Effect of Etiolation on Bulbs, Tubers, Corms and Rhizomes. — In species in which the stem is compressed and clothed with scale-leaves in the form of a bulb as in Allium (pp. 37,39), Ama- ryllis (p. 40), Bowzea (p. 82), Hemerocallis (p. 113), Hyacitn- thus (p. 117), Varczssus (p. 128), Ornithogallum (p. 120), Quam- assia (p. 87), Sparaxis (p. 180), Tritelia (p. 182), Tulipa (p. 185) and others of the same type but Fic. 161. Afplectrum spicatum. A, little alteration ensues, except spent corm with young corm bearing a that the bulbs or stems developed eat ring come ongar whch ar a8 storage and propagative or other is attenuated from being formed in gans at the end of the season darkness. in the dark room are necessarily smaller than the parent bulb of the last growth in the open, by reason of the diminished amount of material available for construction and the diminished surplus for which storage is to be provided. The same is also generally true of MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 215 solid tubers and corms like Arzstolochia (p. 71), Arisaema (pp. 48, 50), Calla (p. 87), Caladium (p. 85), Peltandra (p. 144) and others of this type, the newly-formed part of such structures being more slender when formed at the bases of etiolated branches, inflores- cences and leaves. In the last-named instances, however, in addi- tion to having a lessened need of storage tissue the etiolation of the aérial organ undoubtedly exerts an additional stimulation by which more attenuated forms result. This action is the converse of that seen in partial etiolations in which illuminated organs exert a stimu- lative effect on others in darkness. ‘The former phase of the reaction is most highly accentuated in Aplectrum (p. 46) and 77pularza (p. 181) of the plants studied. In these two species the vegetative sea- son is characterized by the formation of one or more offsets from the corms, the terminal internodes of which become apogeotropic, as- sume an upright position and become thickened into a corm, bearing a single leaf from the uppermost internodes. The leaves are much longer than the normal and do not completely expand, remaining in a plicately folded position in the darkness. This attenuation is also participated in by the internodes from which the corm is formed, a length nearly double that of the normal being reached, with a diam- eter less than the normal (Fig. 161). The creeping rhizome of Sansevierza offers an example of a diageotropic stem which undergoes alterations in its geotropic proper- ties during etiolation, becoming apogeotropic and assuming an up- right attitude, the structure becoming entirely radial (p. 171).'” A similar action is exhibited by MVuphar lutewm according to Goebel, the creeping rhizome assuming an erect position, and undergoing alteration from a dorsiventral to a radial structure when covered with earth; the effect in question is ascribed to darkness, and is said to be exhibited by many spermatophyta.™ Effects of Etiolation on Aquatics.—The photomorphotic relations of rooted and submerged aquatic plants are by no means simple, and reactions are so highly diverse that a general treatment is all but im- possible. The stems or modified branches bearing floating organs of Muphar, Nymphaea, and other species which anchor to the sub- stratum have been shown by Frank to have a capacity for adapta- 1533Maige, A. Recherches biologiques sur les plantes rampantes. Ann. Sc. Nat. Bot. Ser. 8-21 s+ 345. ' 1900. 15{Goebel, G. Organography of Plants. Part 1, p. 231. 1900. 216 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. tion to the depth of the water, which seems to be independent of ef- fects of alterations in intensity of illumination. A similar reaction is seen in Hydrocharis morsus-ranae when the stature of the petioles of swimming and stranded plants is compared. The elongation of stems submerged below the normal depth is accomplished by an ex- cessive growth of the usual number of internodes rather than by any multiplication of these members in all of the observations which have been brought to the author’s attention.’” Noll has recently proposed that all such such adaptations by which the the length and character of supporting organs are altered in order to bring about a better ad- justment with the medium or sub- stratum should be included under the general head of etiolations, which might be distinguished ac- cording to the nature of the cause. Thus the well-known reactions of plants to darkness would be desig- nated as darkness-etiolations, while the modifications due to the depth of the water would be water-etio- lattons. ‘The same author has also proposed that the specific morpho- Fic. 162. Caulerfa with cylin- genic influence of darkness upon drical exeuwee tens in darkness. plants should. be known as shore Redrawn, after Klemm. ; i F tonus in antithesis to Pphototonus. The former term is acceptable as it suggests a definite term for a phase of reaction on the plant of the plant, which, as previously pointed out by the author, and emphasized by Noll, is not due simply to the absence of the effects of light, but is the reaction to a definite condition.’”* Rooted aquatics such as Calla palustris (see page 87) and Peltandra Virginica (see page 144) were found to undergo a slightly 155Fank, A. B. Ueber die Lage und Richtung schwimmender und submerser Pflanzentheile. Cohn’s Beitr. z. Biol. d. Pflanze, 1: Hft. 2. 31-86. 1872. '@Noll, F. Ueber das Etiolement. Separate a. d. Sitzungsber. d. Nied-Rhein. Gesell. f. Natur- u. Heilkunde z. Bonn. 1g01. MacDougal, D. T. Critical points in the relations of light to plants. Read before the Society for Plant Physiology and Morphology, Baltimore Meeting, Dec. 28, 1900. Abstract in Science, 13: 252. 1901. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 217 excessive elongation of the petioles when confined in darkness, and Saururus cernuus (see page 179) developed stems in excess of the normal length under the same conditions. It is to be noted that these three species are, properly speaking, bog plants and support their inflorescences and foliar organs above the level of the water. A similar behavior has been reported for W7ppuris vulgaris, Ranunculus divaricatus and Myriophyllum spicatum by Mobius, so that the evidence is fairly conclusive that aquatics or semi-aquatics, which carry up the shoots irrespective of the exact height of the water level agree with land forms in their etiolative reactions.’” The results attained by Mébius with other forms are fairly in accord with those of Frank so far as the action of stems is concerned. Naias major, Cabomba, Chara and Callitriche showed no special reactions to confinement in darkness. Phz/otria Canadenszs (Elodea Canadensis) and Ceratophyllum demersum occupy a position mid- way between the two groups of forms noted above. Both species are rooted aquatics with the shoots wholly submerged, and yet show an exaggerated elongation of the internodes in darkness, even when torn from their anchorage and allowed to float freely in the water. The flowers of Ceratophyllum are borne in submerged axils, and those of Phz/lotrza float on the surface, the staminate ones becoming detached and rising to the surface when mature. These etiolative elongations are accompanied by various reflexive movements of the leaves in Ceratophyllum and Myriophyllum. No explanation is at hand to account for the characteristic behavior of the two forms noted above. It may only be said that these two plants are exceptions to _ the rule that submerged and floating aquatics are not capable of etiolation. It is to be noted in this connection that the submerged forms of at least some of the species with dimorphic leaves are due to the osmotic action of the salts dissolved in the water, or rather to the amount of water held in the vacuoles of the primordia. This has been shown to be the case in Proserpinaca palustris and is very probably true of other forms also.'’* The elongated cylindrical prolifications formed by Caulerpa in darkness may be taken to be due in part to the specific influence of 151 M6bius, M. Ueber einige an Wasserpflanzen beobachtete Reizarscheinungen. Biol. Centralblatt, 15: 1, 33. 1895. 158 MacCallum, W. B. On the nature of the stimulus causing the change of form and structure of Proserpinaca palustris. Bot. Gazette, 24: 93. 1902. * 218 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. darkness, and in part to the absence of the formative influence of light, by which dorsiventrality is wholly lacking from etiolated organs. The reactions of Caulerpa in the dark chamber are to be classed with those exhibited by Ceratophyllum and Philotria as being entirely independent of pressure, since the reactions in ques- tion are exhibited by isolated floating fragments of shoots.’” Duration of Etiolated Organs and Plants.— The actual duration of etiolated organs formed and confined in darkness varies greatly with the degree and mode of development of these organs, and is greatly influenced by the transpiratory relations of the shoot, a sub- ject which will be discussed below. ‘The length of time, or number of seasonal periods through which an ordinary chlorophyllose auto- tropic species may exist, when confined in a dark room, is deter- mined by a number of factors. It is to be said that the data bear- ing upon this subject, as noted in my observations, are by no means to be taken as to express the ultimate endurance of the species tested since a modification of the temperature and moisture to meet the special needs of the separate species would doubtless result in extend- ing the periods much beyond the limits given. If the plant pro- duced in darkness simply the number of stems, branches or foliar organs usually developed in one season, the question became one of the endurance of the separate organs, and the greater majority of the species examined perished with the death and maturity of such etiolated members, many of them being incapable of further exist- ence upon the reduced supply of available reserved food. In one series of forms the failure of the earlier organs formed in darkness to reach illumination was followed by the extension of the shoot by excessive elongation of the internodes, and the multi- plication of these members and the dependent branches, in a manner giving an epitome of the life of the normal plant. Thus, in the seed- lings of A sculus, Hicoria and others, the young plantlets developed many more internodes than the normal, the foliar organs of which quickly perished, the entire growth representing a series of efforts to spread chlorophyllose tissues in the light. This capacity in seed- lings in the way of continuous effort, seems to reach its maximum in the cocoanut, which continued a growth of the plantlet for fifteen months without interruption, being nourished saprophytically upon the carbohydrates, fats and proteids, stored in the huge endosperm. 159 See references to Berthold, Noll and Klemm on page 25 of this memoir. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 219 At the end of this period half of the material originally stored still remained in a normal condition, and it seems entirely probable that the seedling of this species might be capable of living two or three years in total darkness, receiving only water and mineral salts from the substratum. No evidence has been afforded by my experiments that any adaptation to continued darkness, was made by an increased capacity for taking up organic matter from the soil. Continuous growth resulting in the formation of a number of leaves far in excess of that shown in an ordinary season, was observed in Canna, which developed etiolated leaves vigorously and continuously for four months. Caladium (p.85), which continued sending up leaves for a period of twenty months in darkness before the underground member perished, and Atumex (p. 170), which sent up a succession of leaves for eight months are also examples of this type. The slow growth of succulents in darkness is of a similar character. Opuntza (p. 131), makes a steady extension of the curious cylindrical etiolated shoots through long periods of dark- ness. Gasterza (p. 110), was found to continue the extension of its aérial shoot for eighteen months in total darkness, and Sazse- weerta (p. 171) for a period of twenty months, by means of food stored up in the underground stems and succulent leaves. The endurance of plants which undergo seasonal periods of in- activity in darkness gives the question a new aspect. In one series inclusive of Afzos (p. 42), Arzstolochia (p. 71), and Cyclamen (p. 100), shoots are sent up from the tuberous underground organs which undergo a characteristic etiolative development, and then perish, the plastic contents of the newly formed members being transported back into the storage organs. At the close of the sea- son, the amount of material in such organs is less the amount used in respiration, and the portion that has been converted into aplastic substances in the aérial organs. The principal changes inthe storage organs of plants of this type consist in slow increases in size during a number of seasons until destroyed by some contingency, or reach some limit of growth at present unknown. The external layers of such members are generally well protected by corky or other re- sistant layers, and do not decrease in size during the withdrawal of the material necessary in the construction of the aérial shoots. A larger group of the species brought under observation have underground organs in the form of rhizomes and corms in which a 220 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. new section is added to the apical portion during the seasonal activ- ity, and the oldest portion is abandoned and cut off from the surviving region, examples being furnished by Artsaema (pp. 48,50), Zrellium (pp. 181, 182), Avodes (p. 86), Am- orphophallus(p. 40), Felix (p. 106), Menispermum (p. 125), Onoclea (p. 129), Osmunda (p. 132), Pel- tandra (p. 144), Podophyllum (p. 150), Polystichum (p. 147), Pterts (p- 157), Veola (p. 186) and Wood- wardia (p. 188). Plants of this type seemed to be admirably adapt- ed for several seasons activity in uninterrupted darkness. The ac- 4 tion of the apical bud generally re- sulted in the formation of a terminal region of smaller diameter than A the normal, and as the rhizomes A B or corms were cut away in the older Fic. 161. Arisaema triphyllum. A, portions the underground mem- seedling after first growth in darkness. ber left at the end of the season Bs seedling after seganal etiolation. C, ot growth in darkness wouldane seedling after third etiolation. smaller than the normal average. The aerial organs sent up for such diminished underground mem- bers were also smaller than the normal, and showed a tendency to appear in lessened number. The most striking example of this nutritive type is that of Avzsaema (pp. 48, 50), the corms of which were capable of four seasons of activity in the darkness under con- ditions of fairly constant temperature as described in an earlier sec- tion of this memoir. So far as the single set of analyses are to be considered as representative, the proportion of water increases in the aérial organs with successive etiolations, and decreases in the corms. The repeated development of the plant in the dark room without any accession of new material from the chlorophyl-apparatus seems to lead to the conclusion that the stored material contains the necessary constituents for cell construction, and the endurance of any species of the conditions under which no new food may be formed is primarily a matter of food supply. The capacity for such MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 221 repeated growth is a most effective device in the economy of species living in regions in which the upper layers of the substratum is loose and subject to shifting changes which might cover a plant too deeply for it to reach the surface during any given season. It is to be seen that Avzsaema (pp. 48, 50) is capable of four distinct efforts to reach light and exposure to atmospheric factors. The seedlings of this plant exhibit this same adaptation in a remarkable degree, since the plantlet is capable of three seasonal efforts to bring its develop- ing leaves up into sunlight. As has been described previously, Arisaema Dracontium (p. 48) and Arum maculatum naturally carry on the first season’s growth of the plantlet without the development of chlorophyl-bearing organs, thus greatly lengthening the period of saprophytic nutrition of the seedling.” | A fourth type of endurance to prolonged periods of darkness is offered by species in which the old storage organs are destroyed during the period of formation of aérial organs from their buds, and new subterranean organs are developed on branches of the original organ or from lateral buds from the stems arising from them. Aplectrum (p. 46), Brcuculla (p. 80), Solanum (p. 180) and Trpu- Jaria (p. 181) may be cited as examples. The total duration of no one of these species has been tested, but the potato has been seen to form the second generation of tubers in darkness, and doubtless this species is capable of extended existence without light under proper conditions of temperature and moisture. In addition to the simple behavior of the corm in Avvsaema (pp. 48, 50) noted above, the lateral buds may develop young corms and use up the material from the parent corm, continuing the existence of the plant in this manner. It is to be seen therefore that an exposure of the aérial members of a plant to light is not an indispensable tonic condition for the plant. The subterranean members may continue their normal ac- tivity for several seasons when deprived of illumination, and with but little alteration in their structure, and that due directly to the amount of reserve material returned from the perishing etiolated members. In a few examples creeping stems which are only par- tially submerged or imbedded in the soil undergo changes in habit and function when placed in darkness, but such reactions must be 160 MacDougal. Seedling of Arv’saema. Torreya, 1:2. 1901. Rennert, R. J. Seeds and Seedlings of Arzsaema triphyllum and Arisaema Dra- contium. Bull. Torr. Club, 29: 37-54. 1902. 222 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. taken as direct reactions to darkness rather than to any communi- cated impulse. ‘Transmission of the etiolative impulse is to be seen in aérial shoots however. Aérial stems and aérial branches of plants with submerged stems will be considered in a common group in the present discussion. It is found that the references to etiolated stems in the greater part of the literature include both forms, and that no sharp distinctions have been made as to the main axis and its branches in the treatment of the relation of light and darkness to plants. The amount of branch- ing and prolification of stem structures of all kinds in darkness is a very important feature of the reactions however and will receive at- tention in the following section of this memoir. , Effect of Darkness on Climbing Plants.—The aérial stems of plants that climb by twining, and by tendrils, examined during the course of my work include Agzos (p. 42), Aristolochia (p. 71), Bowtea (p. 82), Falcata (p. 104), /bervillea (p. 197), Menispermum (p. 125), and Smz/ax (p. 199). Of these Afzos and Arzstolochia develop stems that reach a length not far from the average nor- mal, although the maximum length of stems in the open exceeds that of the maximum in darkness. The average length of the in- ternodes in both of the above instances was far greater in the etio- lated (see pages 43 and 71 of this memoir) than in the normal. Sachs found that the normal internodes of Dzoscorea Batatas were longer than the etiolated, that but little difference was shown by the internodes in the hop vine and that etiolated internodes of Bryonza dioica were slightly longer than the normal when compared with regard to homologous positions in the shoot. As a result of a con- sideration of the data obtained by his observations Sachs was led to believe that by reason of their position in the stem some internodes had become permanently etiolated or that certain internodes inherited the etiolated habit, and did not undergo further elongation when compelled to grow in darkness. Thus he says: ‘* Wahrend die in der vorigen Abtheilung betrachteten Internodien durch die Beleych- tung in ihren Verlangerung gehindert werden, im Finstern aber ihrem Ausdehnungsstreben Geniige leisten, giebt es dagegen andere Internodien, welche selbts unter der Wirkung des vollen Tageslichts das Maximum ihres Langenwachstums erreichen kénnen und daher durch die Finsterniss keine weitere Steigerung erfahren. Solche Internodien kann man gewissermassen als natiirlich etiolirte be- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 223 trachten oder besser ware es vielleicht, sie als solche zu bezeichnen, deren Langenwachstum durch das Licht nicht wesentlich beeinflusst wird.” *' He seems to have lost sight of the differences in behavior among the internodes and to have transferred his idea of ‘‘ natural etiolation ” to include the entire stems. The measurements of etio- lated and normal internodes given by him show that certain inter- nodes in the stem of any given species undergo excessive elongation in darkness and others do not. His observations in this matter are 11 RRR Fic. 164. Jpomea purpurea, with terminal portion of twining stem enclosed ina dark chamber illustrating the method by which ‘ partial etiolations ” are produced. Redrawn, after Sachs. confirmed by many others including my own, and it seems quite evident that the occurrence and position of internodes undergoing etiolative elongation are characteristic of the species and may have some connection with its general habit, and that no stem is to be re- garded as ‘* normally ” etiolated. 161Sachs. Ueber den Einfluss des Tageslichts auf Neubildung und Entfaltung verschiedener Pflanzenorgane. Bot. Zeitung, 21: Beilage, p. 31. 1863. 224 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Cotyledonary stalks of twining plants are excessively elongated in darkness in species in which the cotyledons are raised above the soil, but in others in which the cotyledons remain below the surface naturally, the first internode of the plumule takes up this action, and in some instances as in Wcorva (pp. 113-117), AFsculus (p. 191) and others in my own observations, the increase is shared by all of the suc- ceeding internodes. This action is not confined to the climbing plants. Alterations in the rate of growth and final length due to etiola- tion are variously distributed in climbing stems. The basal inter- nodes of Afvos show the greatest increase in length over the normal, while the median members are but little changed. The basal por- tion of the aérial stem of Bowrsea, which is morphologically to be considered as an inflorescence axis is greatly elongated while the terminal braching portion is much dwarfed. The median inter- nodes of Bryonia appear to exhibit a tendency to excessive elonga- tion according to Sachs, the basal ones not reaching the normal size. The basal internodes of Falcata were elongated more excessively than the other portions of the stem, although all of the internodes were doubled in length. JZenispermum did not develop internodes in any instance equal to the normal average, and the limited growth of this species in darkness, whether directly due to limited nutrition or not, yet is certainly conditioned by it, since the amount of reserve material in the slender rhizomes is very small. In Phaseolus, as tested in ‘* partial ” etiolations by Sachs the terminal internodes were much more elongated than the basal ones in darkness. It is to be seen, therefore, that the influence of darkness on climbing (twining) stems causes local disturbances of the rate of growth, and altera- tions in the location of the zone of maximum elongation. Tbervillea is a tendril climber and the stems reached but a frac- tion of their normal length in darkness, the etiolated internodes being about normal length however. Svmz/ax, which is also a tendril climber, sent up long shoots which were much less than the normal length. Extensive observations are not at hand, yet it is believed that multiplication of the internodes in darkness does not occur among twining plants, the reaction consisting wholly so far as length is concerned, in alterations in the length of internodes, which may not be equal to the normal in number. Etiolated stems of climbing plants were prophototropic so far as my own observations go, and the capacity for the reaction to MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 22 impinging rays of light seems to be inherited by individuals which have never been exposed to light except in the period of the integra- tion of the seed from which they grew. The actual degree of sensi- B, etiolated stems of Aristolochia. C, etiolated stems of Menispermum. 226 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. tiveness is increased however, and etiolated plants show some diver- gence from the normal in reaction time and amount of increase in intensity necessary to constitute a stimulus. '” All of the climbing species examined in the dark room at the New York Botanical Garden were apogeotropic, and the stems assumed an erect position, falling over from their own weight as soon as a certain height had been reached. The development of JZenz- spermum was accompanied by but slight manifestations of this char- acter however, and the comparatively short stems remained in an upright position in most instances. It is most notable that none of the five species examined by the author, Apzos, Arzstolochia, Bowzea, Falcata and Menispermum, in which adequate stems were devel- oped, were capable of twining around a support, although repeated tests of this particular phase of the reaction were made. Moreover the nutatory movements of the apices of the etiolated stems were of much narrower amplitude than in the normal. Duchartre recorded that Droscorea Batatas and Manda suave- olens did not exhibit twining in darkness when fully etiolated, but that when normal plants were brought into a dark room twining con- tinued for some time, the apical portion of the stem finally assuming an upright attitude.'"* These results were confirmed by de Vries." Sachs’ experiments appear to offer evidence to the contrary, since he found that etiolated internodes of /fomaea purpurea and Phaseolus multiforus were capable of attachment to a support by twining around it. An examination of his technique shows that such results were obtained in ‘* partial” etiolations only, in which the apical por- tions of stems were thrust into small chambers through openings sealed with cotton, wool or other fiber, thus introducing the vitiating action of possible imperfect exclusion of darkness and the positive stimulative influence of light on the free portion of the stem." 16? Figdor, W. Versuche ueber die heliotropische Empfindlichkeit der Pflanzen. Aus. d. Sitzungsber. d. kaiserl. Akad. d. Wiss. i. Wien, 102: Abth. I. 1893. See references given in above paper to Wiesner’s researches. 63 Duchartre. Compt. Rend. 61: 1142. 1865. 14De Vries. Zur Mechanik der Bewegungen von Schlingpflanzen. Arb. a. d. Bot. Inst. i. Wurzburg, -3: 317- 1873. 8 Sachs. Wirkung des Lichts auf die Bliithenbildung unter Vermittlung der Laubblatter. Bot. Zeitung, 23: 117. 1865. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 227 The results of observations upon etiolated seedlings appear to offer another phase of the question however. Both Sachs‘ and Noll'” UN La Fic. 166. Etiolated stems of Afzos, and Bowzea. record that the stems of seedlings are capable of winding around supports even when fully etiolated. Noll grew seedlings of Po/yg- onum Fagopyrum, Tropaeolum majus and Brassica Napus in a dark chamber under conditions that seemed to exclude all vitiation from the effects of light, obtaining marked circumnutations in half of the number of seedlings in some series of tests. The period of a single revolution of the growing tips ranged from eleven and a one- quarter hours to two hours. The stems of the seedlings of Tyro- paecolum and Fagopyrum, and in few instances those of Lrasszca also 166Sachs. Vorlesungen ueber Pflanzenphysiologie. p. 668. 1882. 167 Noll. Ueber rotirende Nutation an etiolirten Keimpflanzen. Bot. Zeitung, 43 : 664. 1885. 228 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. were found to be capable of twining around thin wooden rods sup- ported in a vertical position. The action of the last-named species is held by Noll to indicate a method by which the twining habit might arise in any species with a pliant stem, in which torsions arise. In connection with the aspect of the subject under discussion in the present paper, this capacity for twining might be regarded as an in- herited quality in the seedlings in question, and to be made possible by the torsions characteristic of certain etiolated stems of seedlings. So far as the evidence at hand is to be regarded as conclusive how- ever, the power of twining is to be denied to fully etiolated adult stems ; at least it may be said to be ‘‘ not proven.” It is by no means im- probable however that it might be exhibited by seedlings and young stems arising from tubers or propagative bodies of some species. The attenuated stems of climbers offer some evidence upon the effect of nutrition on development. The translocation of the necessary supply of constructive material from a basal reservoir through the long thin stems in which the cross section of the conducting tissues is very small, must result in a sufficiency of supply reaching the apical portion of the stem after a certain length has been reached. This upward transportation of carbohydrates is also rendered more dificult by the lack of development in the transpiratory organs. Scarcely any doubt remains that the insufficient food supply does operate to limit the stature of thin stems of all kinds, whether climb- ing or not. The duration of the aérial etiolated shoots of climbers in some instances such as in Apzos, Aristolochia and Menispermum, is fairly comparable to that of the normal. The delicate physical structure of etiolated stems makes the length of existence of organs grown in darkness more or less dependent upon the mechanical treatment which they receive from the experimenter. The lack of thickening in the epidermal walls, and of the mechanical and vascular tissues in general renders etiolated stems peculiarly liable to abrasions and wounds which quickly result in death. If care was taken that the action of air currents was excluded, and the etiolated organs were not handled or bent sharply the length of life was greatly extended, a fact also true of all etiolated organs, which in no instance were found to exhibit the power of forming cailuses or closing wounds in an efficient manner unless brought into light. It is well known how- ’ MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 229 ever that normally developed organs may form callus when confined in darkness. The stems of etiolated climbers have been shown by various authors to be of normal thickness in some instances, greater than the normal in others, and less than the normal in others. Stems of AZzos, Aristolochia, Bowrea, Falcata, Menispermum, Tbervillea and Smilax were thicker than the normal. The increase in diameter was due in all instances to an enlargement of the pith by increase in size of the elements, coupled with increase in the intercellular spaces in some cases, and also an increase in size and number of the elements of the cortical parenchyma with material alterations in theform of the cells in both instances. These plants share with all etiolated stems a lack of differentiation and develop- ment of the epidermal tissues. Trichomes were lacking in the etiolated stems of Afzos, and were not so numerous on stems of Menispermum grown in darkness as on stems grown in light. The epidermal cells of Afzos and Falcata were larger in all diameters than the normal, and smaller in AZenzsfermum. Functional stomata were present in Afzos, in increased number in Arzstolochza, but were fairly normal in number in Falcata and Menispermum. Tissues of purely mechanical function in the subepidermal region and near the pericycle were lacking in development in all instances, while the stele here as in all etiolated stems remained in an embryonic condi- tion. Afzos presented a notable instance of the origin of a second- ary generative layer in the pericyclic region similar to subterranean tuber-forming stems, ajthough no other resemblance to these organs could be made out except, so far as the general increase of the paren- chymatous tissues might be taken to be of this character. Of the two species of tendril climbers examined, /bervrllea only bore these organs, and in a size but little less than the normal. The tendrils of Szzz/ax are borne laterally on the hypopodial portions of the leaves, which appeared in darkness only as bract-like formations with the tendrils represented by minute papillae. The etiolated tendrils of /dervz/lea were found to be irritable to contact, and en- circled small rods of wood, but the free portion of the tendril be- tween the engaged tip and the base was not thrown into spirals; a fact due among other causes-to the lack of development of the me- chanical tissues. Sachs found that the tendrils of Cucurbita not only clasped supports but the free portion passed into the spiral form 230 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. in the ‘* partial” etiolations made by him, and Von Mohl previously reported that the tendrils of etiolated plants of Bryonza were capable of a normal exercise of their functions in darkness.'™ Growth and Development of Seedlings in Darkness. — Seedlings present more than one physiological type, and it will be profitable to divide them into several groups for the purposes of the present discussion. The species included in the present series of experi- ments include A Fsculus hippocastanum (p.191), Arisaema Dracon- lium (p. 48), A. triphyllum (p. 50), Castanea dentata (p. 91), Cocos nucifera (p. 95), Corx Lachryma-Jobi (p. 97), Hicoria minima (p. 114), H. ovata (p. 115), and H/. sp. (p. 113), Gleditsta triacanthos (p. 113), Phaseolus sp. (p. 147), Quercus palustris (p. 158), Q. rubra (p. 159), and Q. sp. (p. 161), and /ezcznus communis (p. 169). Of the above species Arésaema, Cocos, Cotx, Ricinus, as well as Zea, have a comparatively large quantity of reserve material stored in an endosperm, which in all instances except in /tvcznus remains buried in the substratum until a certain amount of food material is withdrawn, and then the storage organ perishes. The degree of development and duration achieved by the seedling in such instances is dependent upon the amount of reserve food available in the seed, and the efficiency of its protection from decay and the attacks of fungi and bacteria. Thusin Cozx the amount of material stored in the seed is not greater than in Zea, but the etiolated plantlets of the former attained a height much greater than the latter, in which but a frac- tional part of the starch and other material was absorbed by the seedling. Decay usually sets in early in the germination of the grain and the growth of etiolated seedlings of Zea soon ceases because of lack of food material. Cocos may be offered as an example of a device by which a comparatively enormous amount of food is stored up and protected from damage from external causes, nearly all of it being available to the developing plantlet. A seed- ling of this plant lived in the dark room for fifteen months saprophyt- ically at the expense of the endosperm, and when examined at the close of this period had not used more than half of the total amount of the endosperm. During the interval, seven large leaves had been developed and an amount of growth carried on fully equal to the 1688 Sachs. Wirkung des Lichts auf die Bliithenbildung unter Vermittlung der Laubbliatter. Bot. Zeitung, 23: 119. 1865. Von Mohl. Ueber den Bau und das Winden der Ranken und Schlingpflanzen. pp- 83, 84 and 122,127. 1827. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 231 normal performance of the plant. The above experience leads to the suggestion that the immense economic usefulness of Zea would justifiy a systematic attempt to develop races in which the endosperm would be more perfectly protected from the agencies which usually destroy it. The advantage gained from the use of the additional amount of food would accrue in a shortened vegetative period and stronger and healthier plants, resulting in a more abundant crop at the end of the season. It is more than probable, however, that the very processes of breeding of this species which have been carried on for the purpose of increasing the size of the grain, and the acqui- sition of the qualities that render it more suitable as an article of food have tended to weaken the protective devices of the grain, and to render it more liable to the attacks of destructive agencies. The most remarkable species in the matter of the relation of the endosperm to the plantlet are to be found in the Araceae in which the seedling of Arzsaema Dracontium and Arum maculatum may carry on their development during the first year after germination entirely at the expense of the material stored up in the seed even when under normal and suitable conditions. The other species, Av7saema tri- phyllum, with which the tests were made, showed the remarkable capacity of carrying on an amount of growth in darkness fully equal to the normal at the expense of the material stored in the seed. Beyond this it was capable of vegetative activity during the three succeeding seasons in the same manner, a manifestation not exhibited by any other plant, of which records are available. Asa result of this action it is to be seen that the starch and other material in the endosperm is hydrolyzed by diastases secreted 2” sz¢a, and in the embryo, and after being translocated to the body of the young plant is partially converted to the use of protoplasts, and into their enclosing membranes and included substances. With the death of the seedling nearly all of the plastic material, and the starch which has been laid down in the tissues of the plantlet are again translocated to the tuber formed at the base of the stem. Upon the beginning of a second season of growth the entire process is repeated except that in this, and in the succeeding seasons, the translocations simply move the material up and down the roots and stems of the young plants. The residuum of plastic ma- terial thus undergoes four major translocations and reconversions during the course of life of the seedling which lives three years in darkness. 232 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. In the single instance in which the endosperm is carried aloft, as illustrated in Avc*nus, the amount of growth seems to be regulated directly by the amount of food present, which is nearly all available for the use of the developing plantlet. It is noticeable that this plant affords not only an exaggerated growth in length of the hypocotyl, but also allows the first internode of the plumule to reach a limited development. The stems of Cotx, Zea and Cocos are slightly elongated in etiolated plants, while in Arvzsaema the stem takes the form of an underground tuber, the aérial portion consisting of the petiolated leaves, the tuber or corm being slightly attenuated as a result of the etiolation. In all of the above instances the excessive elongation consists chiefly in the increased length of a fairly normal number of internodes, although Cocos developed one more than the control specimens of the same age. A second group of seedlings consisted of species of dicotyledonous woody plants with the reserve material present in large amount and contained in cotyledons which remained buried in the soil, including AEsculus, Castanea, Hicoria and Quercus. A£sculus usually de- velops one internode only during the first season of its growth, but the etiolated plants extended nine, the basal one of which was slightly longer than the normal. The various species of Acorza and Quercus examined agreed in that the number of internodes was never greater than in the normal, except in one unknown Quercus, and in the case of 2. palustr7s was actually less. In all instances the etiolated stems were two or more times as long as the normal, the most excessive increase in length being witnessed in the basal inter- nodes. The food material stored in the nuts of the seeds is quite perfectly protected from damage, and the greater part of it was avail- able for the use of the plantlet. In consequence of this fact the duration and actual period over which growth extended was very long. In the case of a Avcoria the seedling went into a resting stage after a period of activity equal to a normal season and then resumed growth, making several branches. This repeated growth did not, however, entail the translocations and reconversions of energy characteristic of the seedlings of Ar7saema as described above. The long-continued action of these woody seedlings implied some radical departures from the usual method of morphogenic procedure, which were most highly accentuated in the cortical tissues, and epi- dermal elements. The species in question form a distinct bark on MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 233 normal plantlets, and all are characterized by exfoliating bark in the adult tree. The anatomical details of etiolated forms of this type will be described in a later section of this memoir. It may be said in this place however, that the transpiratory organs inclusive of len- ticels were more sparsely developed than in the normal. But two species of woody plants were examined in which the cotyledons served as the main storage organs, and were carried aloft during germination. G/edzts7a developed the hypocotyl to a length 50 per cent. in excess of the normal, and the first internode of the plumule attained alength of 8 mm. The cotyledons were held in an appressed position, enduring through a period of sixty days, much longer than in the normal, and were thrown off only after their con- tents were completely exhausted. The other species, a Phaseolus, developed a hypocotyl longer than the normal; the contents of the cotyledons were entirely transferred, leaving but a small remnant which was cast off with the withered seed leaves. The amount of material thus laid down in the embryonic stem was sufficient to per- mit the growth of the first internode of the plumule to a length of three times the normal, and for the development of a pair of leaves with small laminae and attenuated petioles. The second internode was hindered in its growth by the exhaustion of the food supply. The difference in aspect of this plant and that of the terminal portion of partially etiolated adult stems was most noticeable. The root systems of the various seedlings etiolated were incapable of exact comparison with those of control specimens, but in the main it appeared that the total length and general development of the roots of etiolated plants was not so great as in normal specimens. The growth of the root system would depend to a great extent, however, upon the transpiratory functions of the shoot, and as no etiolated shoot excretes more than a third or a half of the usual amount of water vapor, the effect of the lessened use of water would be reflected in a diminished development of the absorbent organs, which, in the greater majority of instances, also have less exacting demands upon them for mechanical rigidity as a means of anchorage. It is difficult to estimate the value of the various records that have been made of this phase of etiolation, since the results in some instances were obtained by ‘‘ partial etiolations,” and in others the growth of the shoot. may have begun before confinement in darkness, and then in still other instances the dark chambers were not abso- 234 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. lutely exclusive of light. The examination of etiolating material in a dark chamber by opening a door that would admit daylight would of course vitiate the experiments by reason of the light stimulation ensuing in consequence of this exposure. Sachs says: ‘* From the large seed of a bean or horse chestnut, on the contrary, there may be produced in the dark a plant of considerable size with copiously branched roots and several, though small and yellow, leaves.” The specimens of horse chestnut grown in my own experiments did not develop a root system in darkness equal to that in light. The sparse- ness of the root-system of this plant when etiolated is shown in Fig. 150. Detmer'” noted the lack of full development of the roots of etio- lated plants and ascribed it to the lack of the synthetic function of the ieaves upon which the root-system was supposed to be directly dependent. But little doubt remains, however, that an etiolated shoot with lenticellar openings, stomata and other transpiratory devices, would necessarily be accompanied by a more fully developed absorb- ing system than one in which but little water was taken up or used by the shoot. Vogel relates that the roots of plants grown in dark- ness are more developed than those which have been cultivated in light, a statement put forward by him as a result of measurements of the aérial and submerged roots of Bombax and Hura crepitans, which does not afford any real proof of the statement in question, however. Lasareff found that the branches of adventitious roots of a large number of seedings were both fewer and shorter than in nor- mal specimens, but he mistakenly supported the assertion credited to Famintzin by which such correlation was supposed to exist between the roots and shoots, that the longer the shoot of an etiolated plant, the shorter would be the root-system."™ Strebl’” found that the rate of growth of roots of etiolated plants was generally greater than that of plants subject to the alternations of day and night for the brief period in which measurements were made, and this may be reasonably assigned to the undoubted corre- 168Sachs. Physiology of Plants. English Ed., p. 531. 1887. "0 Detmer, W. Die Formbildung etiolirter Pflanzen. Vergleichende Physiologie des Keimungsprocesses der Samen. Pp. 464-478. 1880. 11 Vogel, A. Beitrige zur Kenntniss des Verhiltnisses zwischen Licht und Vege- tation. Flora, 39: 385. 1856. Lasareff, N. Ueber die Wirkung des Etiolirens auf die Form der Stengel. Ab- stract by Batalin. Bot. Jahresber. 2: 775. 1874. M2Strehl, R. Untersuchung ueber das Lingenwachstum der Wurzel und des hypokotylen Glied. Leipzig, 1874. >? MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 235 lation that exists between the rate of growth of the root and shoot, but so far as his data may be taken to bear upon this question in hand, the total amount of growth in etiolated roots was less than in the normal. C. Kraus'® records his observations that the roots of etiolated plants do not reach the stature of normally cultivated plants, which he supposed was a direct correlation with the increased length of the shoot. It appears as a consensus of the evidence upon this point that the root-systems of seedlings do not attain normal development when the shoot is fully etiolated. The numerous difficulties in the way of making accurate measurements have prevented the acquisition of data concerning the roots of adult perennial plants confined in the dark chamber during a vegetative season. The theories which at- tempt the explanation of this lessened development as a correlation with the increased length of the shoot have been found untenable from the fact that the length of the roots and shoot do not vary con- versely as proven by Strehl. The supposition of Detmer that the lesser total length of the roots was due to the lack of material usually furnished by leaves is also quite beside the point, since this relatively diminished growth of the roots ensues when an ample supply of re- serve material is present in the hypocotyls or endosperm from which it might readily be conveyed to the roots, and with much less ex- penditure of energy than from the leaves. The only causes which might affect the development of the root-system would be the use of water by the shoot and the demand for anchoring power or mechan- ical rigidity because of the strains exerted by the weight of a> bend- ing shoot. Etiolated shoots are erect, for the most part, and when disturbed easily and readily fall over, the roots being wholly inade- quate to hold the shoots in position. It is well known, however, that the branching and growth of the root is quickly influenced by the conditions of absorption and transpiration affecting the shoot, and this feature is the only one which may be offered to account for the lessened development of the root-systems of etiolated plants, espe- cially seedlings. Effect of Darkness upon Succulents. — On account of the peculiar relations borne by the leaves of succulents to the stem it will be most 13 Kraus, C. Ueber einige Beziehungen des Lichtes zur Form- und Stoffbildung der Pflanzen. Flora, 61: 145. 1878. 236 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. profitable to consider the development of the entire shoot of suc- culents at the same time. The species which might be included under this head, that were used in my experiments comprise, Agave Americana (p. 37), Gasteria disticha (p. 109), Opuntia Opuntia (p. 131), and Bowea volubilis (p. 82) might also be considered here, since its main axis consists of a succulent bulb imbedded in the upper layer of the substratum from. which arises a slender inflorescence axis. The short thick stems of Agave which are completely sheathed by the bases of the fleshy leaves are not excessively elongated in darkness, the only reaction being shown by the leaves. Leaves partially developed when the specimens were placed in the dark room continued elongation, the newer basal portion being chloro- phylless and yellow. The apical parts of such leaves maintained their original green color with but little change in the chlorophyl during periods as long as eight months. Leaves which were devel- oped after etiolation of the plant had begun did not attain dimensions more than half of the normal, and were completely devoid of color, and showed a reduction of the marginal teeth and of other anatomical features. Stems of Gasterza disticha are usually very short, and are completely sheathed by the bases of the fleshy leaves, which are nearly double the length of the stem. During etiolation the stem elongates excessively by an increased growth of about the normal number of internodes, and the upper end of every internode becomes exposed and free from the sheathing leaf-base. The etiolated inter- nodes were distinctly more slender than the normal. Still more attenuation was observed in lateral branches which are usually diagetropic and serve as propagating bodies. In etiolation these were erect and very slender, with internodes much elongated. Opuntia developed cylindrical stems with internodes slightly longer than in the normal flattened structures characteristic of this plant. The etiolated portions endured confinement to darkness for several months but were not so hardy as the normal stems, a fact probably due in part to the extremely delicate outer membrane which failed to protect the underlying tissues from mechanical damage in handling. The reduction of the transpiratory organs, and the comparatively moist air of the experimental chamber in which the plants were con-: fined in darkness must also have contributed to the early demise of the etiolated specimens. Bowzea developed short thick inflorescence axes in darkness, with leaves slightly increased in size. s MEMOIRS, OF THE NEW YORK BOTANICAL GARDEN. 237 A notable feature of the behavior of succulents in darkness is their great endurance to exclusion from illumination, and also their capacity for the maintenance of chlorophyl for extended periods in the organs constructed in light. The reactions offered by Gasterza, of which the excessive lengthening of the stem is the most important are also to be seen in the Crassulaceae as examined by Brenner '* and others. This author found that the growth of species of this family in moist chambers produced an excessive elongation of the stems, which continued only for a time, when the habit of developing short internodes and consequent rosettes of leaves was again resumed. Fic. 167. Sempervivum assimile. A, normal; B, grown in a moist chamber; C, grown ina dark room. Redrawn, after Brenner. The effort in question may be fairly interpreted as a response to the increased humidity, the increased surface offering additional facilities for transpiration. The formation of slender cylindrical stems instead of the normal flattened ‘¢ joints” seenin Opuntia Opuntia, O. leucotrichia and some other Cactaceae is not exhibited by all plants of this general char- acter, however. Thus the leaf-like shoots of Phyllocactus latifrons do not lose their bilateral form and organization, although reaching a 4 Brenner, W. Untersuchungen an einigen Fettpflanzen. Flora. 87: 387. 1900. 238 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. much reduced size when grown in darkness.'” It is to be said, how- ever, that the results in question were partly secured by ‘‘ partial etiolations”’ and the exact limits of the groups which undergo a re- duction of the bilateral features can not be determined without further investigation. It seems entirely probable that the require- ments of the transpiratory functions might be quite an important factor in a group which has made such sweeping adaptations to the conditions of humidity. Etiolation of Xerophytes with Reduced Leaves and Spiny, or Cylin- drical Stems. — The examination of the information obtained by the etiolation of the second group of forms that have made marked adaptations to transpiratory conditions brings in some further con- siderations. Asparagus officinalis (p. 73), Bowiea volubilis (p. 82), Ibervillea Sonorae (p. 197), and Hgutsetum arvense (p. 103) were cultivated in the dark room under conditions of a higher degree of humidity than that ordinarily, and continuously encoun- tered, by three first-named species. According to the conclusions of Brenner, and the suggestions of Palladine and Wiesner the culture of these plants in a humid atmosphere should have produced a lengthening of the stems and an increase of the surfaces capable of transpiration. It was to be seen, however, that the etiolated stems of this group were in general shorter than those grown in light, the de- crease in length being accompanied by accessions to the thickness. Branching was reduced in all of the species in question when grown in darkness. No extension of the surface was reached by etiolation, or as a result of it, although it is to be said that all of these forms developed stomata, and that the outer membranes were much more adapted to a cuticular exhalation of water than the normal specimens, while the bract-like leaves were actually larger than the normal. The total result could not have been to make an increase of the trans- piratory capacity of the plants examined in any instance, and the conclusion is inevitable that the moisture relations of the individual must play a minor part in the determination of the stature of the shoot when acting simultaneously with the influence of light and darkness, conforming more nearly to the action of Cafsel/a as outlined by Wiesner."® M5 V6chting. Ueber die Bedeutung des Lichtes fiir die Gestaltung blattformiger Kakteen. Jahrb. f. wiss. Bot. 26: 438. Also see Goebel. Organography of Plants, p- 248. 1900. 6 Wiesner, J. Formianderungen von Pflanzen bei Cultur im absolut feuchtem Raiime und im Dunkeln. Ber. d. deut. Bot. Ges. 9: 46. 1891. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 239 Etiolation of Stems of Woody Perennials. — Species with woody stems which were grown in darkness in my experiments include Acer rubrum (p. 188), Baccharis halimifolia (p. 80), Cornus alternifolia (p- 97), Fagus Americana (pp. 105, 194), Populus Simonii (p. 154), Quercus sp. (p. 161), and /ehkus sp. (p. 169) in the adult stage, and Castanea dentata(p. 91), AEsculus hippocastanum (p. 191), Gleditsia triacanthos (p. 113), Hicorta minima (p. 114), H. ovata (p. 115), FT. sp. (p. 113), Quercus palustris (p. 158), 2. rubra (p. 159) and 2. sp. (p. 161), in the seedling, or juvenile stage. The reactions showed the greatest divergence, a part of which may be attributed to the unsuitability of the cultural conditions offered for some of the forms. Effects from such causes were recognizable to some extent, and results due to unfavorable factors may be easily elimi- nated in the analysis of the influence of darkness upon the growth and development of the species in question. Fagus Americana, as examined by myself, and /. sylvatica according to Jost bear a specialized relation to light and darkness of an unmistakable char- acter. The buds of young plants might awaken in darkness in my own tests, but the buds of adult plants a few years older did not begin activity except under the influence of light. This influence was furthermore wholly of a stimulative character, as Jost found that when a few buds of a confined plant were exposed to light the stimu- lation resulting was sufficient to awaken others on distant parts of the shoot from which light was excluded, a result wrongly attributed by Jost to the necessity for the action of light in the construction of formative substances necessary for the development of buds. Further- more, this reaction illustrates most strikingly the difference of results that may be obtained by total and partial etiolations. Again, this awakening of the buds only under the influence of light, and the fact that etiolated stems do not make greater growth than the normal, points most strongly to the conclusion that, in these two species at least, light does not exert a retarding, or indeed a direct action of any kind upon growth; the behavior of the plant with regard to this factor being wholly in response to its stimulative action. A further phenomenon of marked interest in /agws was the fact that both young and adult plants formed calluses rapidly in darkness, and that the buds arising from these calluses made a much more rapid growth than the normal, being capable of extension in dark- ness as well as in light. The typical buds showed only a slight 240 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. elongation of the axis in,some instances and the cessation of growth of the etiolated branches was followed by the formation of a number of loose, brownish sheathing scales around the tips of the branches. The etiolated branches of Baccharzs did not offer any striking differences in form or size from the normal, although the brief dura- tion of the organs formed in darkness demonstrated that the temper- ature and soil conditions were not suitable for this shrub. Acer, Cornus, Populus and /hus developed etiolated branches much longer than those on correspondent normal portions of the shoot. The length of etiolated shoots of Acev was about double that of the normal, an increase that was due in part to the multiplication of the number of internodes, and in part to the excessive elongation of all of these members. The number of etiolated internodes in a branch was about the same as that in juvenile sprouts arising from the bases of trunks, or from calluses on trees in the open, but the lengths of the etiolated internodes was greater than that of the juvenile mem- bers, while the thickness in the two instances were about equal, being greater than that of normal twigs on the shoot or main crown. The approximation of the etiolated and juvenile branches seems to point to the fact that the growth of branches in darkness does not allow development to proceed much beyond the embryonic condition. In one instance the juvenile condition is shown as modified by growth and development in light; in the other the embryonic stage is con- tinued under the influence of darkness. The endurance of the eti- olated twigs corresponded fairly well with the length of an ordinary growing season, but the terminal buds did not continue activity dur- ing the entire period, since most of them soon perished, and lateral buds took up the continuation of the branches. It is notable, how- ever, that none of the etiolated branches succeeded in making such development as to pass into permanent form and to survive after the leaves had perished. Buds of Acer awakened but tardily, and in less number on trees in darkness than in light, and exposure to illumina- tion seems to exercise a stimulative effect on the awakening of the growing points. It was noted that even the occasional exposure to the rays of the electric lamp used in making examinations of the eti- olated specimens produced some reaction in the way of increased development of the buds. The length, diameter, and number and length of internodes of stems of Cornus grown in darkness were much greater than those of normal branches on correspondent por- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 241 tions of the shoot or crown, being approximately the same as in juvenile sprouts arising from the base of trunks. The etiolated branches failed to develop beyond a certain young condition although their existence extended over a period of five months, which is fully equal to the entire vegetative season of the tree. None of the branches grown in darkness succeeded in accomplishing such differentiation and development of tissue as to allow them to pass into permanent form, all of the etiolated twigs dying back to the old stems at the end of their period of activity. Unlike Acer, branching occurred with normal frequency, but the branches, both primary and secondary, assumed an erect attitude in darkness, due to an alteration in the geotropic properties, or to the lack of the phototropic stimulation in response to which the branches habitually assume an approximately horizontal position in light. The length, number and length of internodes, and diameter of etiolated branches of Populus were greater than in normal branches, no comparison having been made with juvenile sprouts. The primary branches assumed a position approximately horizontal in some in- stances, and the secondary branches which were produced in some profusion were more or less nearly erect. The branches grown in darkness were of comparatively brief duration and did not succeed in making such development of tissues as to pass into permanent form, dying back to the base in a few weeks. The etiolated twigs of Azus did not exceed the normal in length, number and length of internodes, or diameter. No branching was observed in the single specimen grown in the dark room, and the blanched members soon perished, their duration being much less than that of a vegetative season. The records of etiolations of entire trees by previous investigators are extremely meager. J. A. Hill writes in 1759: ‘‘ The growth of plants, at least their regular growth, as well as their absolute life depends not only on warmth and moisture, but on light; this moves their juices, and upon this motion greatly depends their increase. If tender plants be kept in constant darkness they lose their leaves and die. Thus Mr. Lee, of Hammersmith, at my desire, making the experiment most fairly, killed two tamarind trees and an abrus; and would have killed an erythrina, but he gave it light in time and re- covered it. Light keeps the juices in motion; and this preserves the whole. When it is not admitted these stagnate, and they ferment 242 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. soon after; then the part falls off, and the plant, wanting its neces- sary organs, perishes.” '” Nearly all tests with the larger woody plants have been made by ‘‘ partial etiolations,” which have been shown to secure results wholly unlike those from complete exclusion from illumination. The observations made by Jost on Fagus, are the only authentic instances in which proper methods were used, and his work showed most conclusively that the action of light was necessary to awaken the buds of this tree. It is not unlikely that the temperature may be an important factor in awakening the activity of the buds of trees, and that the species examined by myself might show greater activity at the unknown optimum temperature in darkness. So far as the actual facts are at hand however, the conclusion seems warranted that the buds of Acer, Cornus and Fagus are stimulated to activity by the action of light, and that only a small proportion of the normal num- ber may grow in darkness. Populus seems capable of carrying out the activity of its buds to a much greater extent than the other species in darkness. Etiolated branches do not advance beyond an embryonic condition, and do not form permanent tissue, enduring over a period not greater than that of an ordinary vege- tative season. No previous discussion has been made of the fact that all woody plants showed a tendency to develop buds on the basal portion of the shoot in darkness, the terminal portions awaken- ing tardily and only in small numbers, proving very refractory in darkness, although appearing sound and healthy atter continued con- finement in the dark room. Seeds of these woody plants germi- nated quite as readily in darkness as in light, the stems formed in darkness being longer than those grown in light, but in no instance were branches formed or the lateral buds awakened except upon the destruction of the terminal bud of the main stem. The stems of etiolated seedlings of this class were longer and thicker than those of normal plantlets, and the internodes were longer, the number of the latter not being increased in all instances. The etiolated stems of seedlings showed marked variations from the normal in the man- ner of development of the phellogen and generative layers. A further notable feature of the etiolated stems of woody seedlings consisted in the fact that the basal portions of the main stems con- tained more or less permanent tissue. When the terminal portion of 7 Hill, J. A. Anatomy of plants, p. 213. 1759- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 243 the stem perished, lateral buds near the base would awaken after a resting period and carry out a second season’s growth, when death finally ensued from a concurrence of causes of which deficient nutrition must have played an important part. Etiolation of Stems of Herbaceous Biennials and Perennials.— The greatest amount of observation and experiment upon etiola- tion has been made with herbaceous species in which the aérial stems are sent up from subterranean axes containing more or less storage material. The species examined by myself are as follows: Aster divaricatus (p. 78), Botrychium obliquum (p. 80), Brassica campestris (p. 84), Cypripedium montanum (p. 101), Delphinium exaltatum (p. 102), Galcwim crrcaezans (p. 106), Hydrastis Canaden- sis (p. 117), Hypopitys Hypopitys (p. 119), [pomea Batatas (p. 120), Lysimachia terrestris (p. 123), Pastinaca sativa (p. 143), Phytolacca Decandra (p. 149), Podophyllum peltatum (p. 150), Saururus cernuus (p. 179), Solanum tuberosum (p. 180), Trillium erythrocarpum (p. 181), 7. erectum (p. 182), Vagnera stellata (p. 185) and Viola ros- trata (p. 187). Hypopitys Hypopitys differs from the other species treated under the above heading in the fact that it derives all of its construction material from underground organs consisting of roots symbiotically organized with mycorrhizal fungi, in consequence of which it has undergone most sweeping morphological degenerations of the stelar tracts and members of the shoot and root-systems. The degenera- tion of the tissues has been accompanied by a loss of the capacity for reaction to the direction of rays of light by phototropic movements. Furthermore, it has been found that light is without appreciable effect upon the shoot, the specimens grown in darkness not differing appre- ciably from those in light. Some fungi were seen to make excessive elongations of the sporophores in darkness, while others were unat- fected. It is difficult to assign an explanation for such divergence of reaction among forms of supposedly similar physiological organ- ization. A large number of herbaceous species of this group including Aster divaricatus, Cypripedium montanum, Galium circaezans, Ipomea Batatas, Phytolacca Decandra, Saururus cernuus and Vagnera stellata, do not make any excessive elongation of the stems or shoots in darkness. Stems of these species developed about the normal number of internodes in darkness, which did not 244 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. exceed the usual length, except in a few instances in which the basal ones were slightly longer than the corresponding members of normal stems. The upper internodes failed to reach the normal length by such amount in stems showing this reaction, that the ordi- nary length of the axis was not exceeded. In some species etiolated stems were thicker than the normal, due to exaggerated development of cortical or parenchymatous elements, both in size and number, and the angular contour was more or less completely lost, the ten- dency being shown toward an isodiametric section. The advance from the embryonic condition reached various stages, but in no case was the differentiation and construction of the elements com- pletely normal. The primary annular and spiral vessels approached the normal in structure perhaps more nearly than any of the elements, but these generally showed altered dimensions of the lumina with thinner walls. Tissues with purely mechanical functions were more reduced than other forms. The rigidity of the etiolated stems was thus dependent upon the turgidity of the delicate and incompletely formed tissues, and they were consequently fragile and easily dam- aged by bending or mechanical contact. Branching was not shown to any extent and the shoot was seen to consist of a single stem bear- ing the reduced leaves. In some instances basal branches ordinarily having a propagative function were produced, and if So/anum might be included, it may be said to be the only species capable of forming reproductive bodies of any kind when etiolated. It is to be seen by reference to page 222 that the reactions of the climbers agree with those exhibited by the species included in the above group. Exaggerated elongations of the stem are shown by Botrychium obliguum, Brassica campestris, Delphinium exaltatum, Hydrastis Canadensis, Lysimachia terrestris, Pastinaca sativa, Podophyllum peltatum, Trillium erectum and T. erythrocarpum, and Viola rostrata. The excessive growth to which this elongation was due was variously distributed. Exaggerated growth in length took place in all of the internodes of Brassica and Lysimachia, and through- out the entire stalk of HWydrastis. The basal internodes of De/- phinium and Vrola were most elongated, although some excessive lengthening occurred in all of the stems, while in Botrychium the increase over the normal was found entirely in the upper part of the stalk, the lower portion being somewhat shorter than the average. Branching was much reduced from the normal habit. The develop- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 245 ment and differentiation of the tissues of the species of this group reached a much more advanced stage than those of the preceding group, and the period of endurance or existence of the etiolated stems consequently was as great as in the normal, in many instances. Etiolated stems were distinguished from the normal by having less angularity, but no species of this group. showed etiolated stems of greater diameter than the normal. Species having the largest amount of reserve food stored in the perennial portions of the plant might be expected to be capable of carrying onarelatively greater development of the stem in darkness, or under any conditions in which the plant is forced to rely upon its own supplies or activities. Asa matter of fact not all species are capable of carrying on growth and construction to the full value of the food supply. A few species, notably the seedlings of A#sculus exhibit this capacity and doubtless many others might be found ; hence nutrition must be the limiting factor in the development of many species in darkness. On the other hand, the shoots of some species perish, although ample and copious supplies of reserve material remain intact in the storage organs. In such instances it is seen that the difficulty may lie in the difficulty of transporting the food-material to distant parts of an elongating shoot, which customarily construct much of their carbohydrates locally, by means of conduction tissues which are much reduced in cross section and which, in common with other specialized tissues, have failed to reach normal differentiation. In order to give the evidence bearing upon the matter of ability to utilize the entire reserve greater conclusiveness, it would be neces- sary to make a special series of tests in which the requirements of the species when etiolated, as to moisture and temperature would be quite exactly complied with, and the activity of bacterial and fungal organisms upon the storage organs was checked. In so far.as de- fined above therefore, nutrition must be taken as important factor in the divergences of etiolated plants from the normal. It is not clear, however, that nutrition is a major factor in the process, as asserted by Sachs,'® who said: ‘‘ Moreover, the size of a plant developed in the dark, as well as the number of roots and leaves formed, are propor- tional chiefly to the volume and mass of the seed, or better, to the quantity of reserve materials accumulated in it.” ‘* At length, how- ever, after a few days, or in the case of very large seeds, after a few 178Sachs. Physiology of Plants. p. 531. 1887. 246 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. weeks, the growth in the dark always ceases, and the whole plant become diseased and perishes; in many cases, as with Phaseolus, etc., not until all the reserve-materials of the seed have been com- pletely used up for the formation of organs; in other cases, however, as with the gourd, growth and the development of organs cease while the cotyledons still retain considerable quantities of unused formative substance.” My own experiments lead to the conclusion that etio- lated growth is indeed not possible beyond the capacity of the stored formative substance, but the ability of the plant to use all of this material depends upon other factors, which are in fact the principal causes to which the characteristic form of etiolated plants is due. Without further discussion of these causes at this time it may be re- garded as quite well founded that the death of etiolated seedlings, or adult plants in darkness, is generally due to the incapacity of the im- perfectly differentiated conducting tissues, or to the destruction of the reserve-material by disintegrating or fermentative processes. The development of the transpiratory system must also be taken into ac- count in the consideration of the mechanisms for translocation of material in the plant. Influence of Etiolation on the Development and Differentiation of the Tissues and Emergences. — The meager facts recorded, con- cerning the effects of darkness and light upon trichomes, in my own observations are not sufficient to furnish a basis for any generaliza- tions upon this subject, and previous investigations have been made under various conditions of imperfect and partial etiolation. Hairs are ordinarily present on the aérial stems of AZzos, but were lacking from etiolated stems, although present in subterranean shoots, which the stems grown in darkness resembled in some particulars (see page 42). Etiolated hairs of Wydrastis were only about one-fourth of the size of the normal both on the stem and leaves, although the former was unduly elongated and the latter reduced. The stalked glands of Lys¢machia were unchanged on stems which underwent excessive elongation, and did not appear so numerous in J/enispermum, although of about normal size. The hairs of Populus were smaller than the normal, although the other epidermal elements were much elon- gated. No marked alterations could be seen in the hairs of Aster, Cornus or Fagus, although the first two species exhibited excessive elongations of the stems on which these structures were borne. The prickles of .Smz/ax were both more slender and shorter on etiolated MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 247 stems thanon normal plants. It is to be seen, therefore, that the con- clusions of Schober that the reaction of these structures is correlated with the habit of the member on which they are borne are not sus- tained (see page 22). Development of Stomata on Etiolated Stems. —The develop- ment of stomata was likewise subject to great variation among the different species examined, and an intimate connection was found between the degree of development of the leaf or stem, and the dif- ferentiation and number of these organs. Stomata were present on the stems of Afros, Asparagus, Bowiea, Hydrastis, Lystmachia, Menis- permum, Opuntia and Phytolacca, but as no special record was kept of this feature it is probable that they might be found on many other etiolated stems. Furthermore, the simple fact of the occur- rence of stomata on any etiolated stem is of importance only when similar data have been obtained from normal stems, and this was neglected in my observations. So far as a general inspection of the results may be taken to be of value, stomata appeared to be most numerous on etiolated stems capable of long duration and extended development in darkness, although shoots that were capable of for- mation of foliar expansions sometimes showed stems entirely lacking these organs. It is notable that no stomata were found on the etio- lated aérial stalks of Podophyllum, and that the stomata on the stems of Viola rostrata failed to open. Only a small proportion of the entire number of prestomatal elements passed into the final stage in Phyto- lacca, and the stomata on the cylindrical etiolated shoots of Opuntza were much reduced in size. _ Lenticels of Etiolated Stems. — Lenticels appeared to be more numerous, especially on the basal portions of stems of etiolated seed- lings of Acer, and A #scudus than on normal seedlings, and lenticellar formations were also more abundant on the lower portions of the etiolated stems of /éervillea and Smzlax than in the normal. On the other hand, lenticels normally present in Populus did not develop beyond the first stage in etiolated stems (see Fig. 117). Structures of this character were to be seen in great number on roots of Cocos, but it could not be said that an abnormal number had been produced, for no exact comparisons could be made. No generalizations may be made as to the behavior of these organs with respect to light and darkness in view of the insufficient data at hand. Epidermal Cells of Etiolated Stems.— Epidermal cells were 248 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. found to be as long as the normal in all instances, except in JZenz- spermum, in which species alone the superficial measurements were less than in normal stems. The epidermal cells showed an increase in all dimensions in a great number of instances in which a multipli- cation of these elements had also ensued. Among the earlier investi- gators various contentions arose as to whether the excessive elonga- tion of stems was accompanied by increase in size, or by increase in number of the epidermal cells, the conclusions of the various workers being based upon the small number of species examined. It is to be seen however, that no general law has been discovered by which the action of the epidermis in darkness may be predicated. Bos } At . AS y sy Rou eee OK yeaa Se YO ’ M LOIS Keon) a 0 alG\ S % J A Al jelte) yl I Neo: Ma at sO) \) Q\ojol0 ; I VL i Vay ey Nf 3. A, B. Fic. 168. Polygonum cuspidatum. A, partial transverse section of normal stem; £&, partial transverse section of etiolated stem. After Rauwenhoff. In so far as the mechanical features of the epidermis are concerned it is to be said that these elements, without exception, either in my own work or in the experiments of previous investigators, fail to attain the thickness of wall and the consequent mechanical rigidity of the normal. The lack of thickening is most noticeable with re- spect to the outer wall, and the ordinary cutinization and deposition of secretions has not been observed in any of the species examined by myself. The end walls show a tendency to lie more nearly par- allel to the circumference of the stem. The epidermis, in common with many other tissues, does not advance beyond a certain primary stage of development, and retains the power of growth and division = MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 249 in the cells during a much longer period than in the normal plant; consequently it can respond to stresses and other factors, which may cause it to undergo increase in size, alterations in form, or multiplica- tion of the cells by division. Thus the epidermis is compelled to make adjustment to the augmented diameter which some stems attain by increase in bulk of the cortical and medullary tracts. Collenchymatous Layers in Etiolated Stems. — Collenchyma shares with other mechanical tissues in a general reduction which, in some instances, amounts to a total disappearance from etiolated stems. The collenchymatous layer ordinarily underlying the epi- dermis failed to appear in etiolated stems of Galiwm and Meni- spermum, and consisted of a tract of tissue with cells reduced in number, or thickening of the walls in Aster, Saururus and Viola. Phytolacca offers the single exception of the formation of this tissue in a manner approaching the normal in etiolated stems. The sub- epidermal layers generally shared the enlargement of lumen and lessened thickness of wall that was to be observed in the cortical tissues of the greater number of species examined. It seems justifi- able to conclude therefore, that collenchymatous tissue is not affected in its development by light and darkness directly, but that the differ- entiation of this tissue is due entirely to secondary causes dependent upon the phenomena included in the growth and development of the tissues interior to it. Formation of Periderm on Woody Etiolated Stems. — The epider- mal and cortical tissues of the trees examined in my experiments offer three types of reaction. Branches of Populus grown in darkness were characterized by the failure of the tissues to develop beyond an extremely simple stage and the cortex was composed of elements which were larger, and with thinner walls than in the normal, while they were variously distorted from the somewhat regular form of the normal elements. The differentiation of the cortex into an outer and inner region was wholly lacking. No activity of any kind was to be found that presaged the formation of bark. In a second type the behavior of the tissues involved only comparatively unimpor- tant departures from the normal. This procedure was seen in Acer, although differences due to lack of thickening in the walls of the epidermis, collenchyma, and cortex were to be seen. The elements of the latter were compressed radially. A similar state of affairs was to be seen in seedlings of A#sculus. Perhaps the least 250 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. ‘ variation from the normal was to be seen in branches of adult trees of Fagus grown in darkness, in which the phellogen, epidermis, collenchyma and cortex were present in an order differing from the ordinary forms only by a lessened thickening of the walls of all these tissues. In Cornus the cortical cells showed abnormally large measurements in all radii with a lessened thickening of the wall, while the epidermal cells began to collapse earlier than in the normal, the underlying tissues also being less thickened. This was accompanied by a precocious development of the phellogen, which however had much the normal structure and arrangement. The most striking departures from the ordinary formation of bark were offered by the various species of Castanea, Hicoria and Quercus constituting the third type. The seven species brought under observation agreed in the normal formation of phellogen in the epidermal region. In etio- lated specimens of Castanea and H/corra the epidermal cells remain intact for some time, and a layer of cortex in the median region in fficoria, and about in the locality of the collenchyma in Castanea begins to collapse (p. 93). Internal to the collapsing layer, and some- times in contact with it in H7corza, an abnormal layer of phellogen was formed. The cortical cells of plants of this group showed no increase in size or marked changes of form outside of those consequent upon the above alterations in behavior of the bark-forming tissues. The walls of these elements were less thickened than in the normal, and fewer crystals might be seen than in the normal. The procedure described above has the effect of reducing the external diameter of the portion of the stem in which the action takes place, in consequence of which the stems are smaller at the base than the normal, or than the upper, younger portions of the same stems. In Quercus the epidermal and subepidermal regions collapse early in the development of the stem. Ordinarily the epidermis endures for a long time and a phellogen is formed immediately underneath, consisting of eight to ten layers of cells. The cells which usually undergo collenchymatous thicken- ing internal to the phellogen seem to be involved in the collapse, and a median layer of the remaining cortex gives rise to a phellogen con- sisting of several layers of cells. The cortical elements appear larger in all dimensions than in‘the normal. The collapse of the epidermal and outer cortical cells begins with the outermost layer and extends inward slowly, having the final effect of reducing the thickness of the portion of the stem affected even more than is done by the similar MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 251 process in A/corza and other species. The difference in diameter between the base of an etiolated stem and the portion a few centi- meters above it is often very great comparatively. Bast Fibers of Etiolated Stems. — The extended periods over which the plants used in my own experimental tests were observed gave much better opportunity for the examination of the behavior of the bast fibers than have been enjoyed by any previous worker that has dealt with this subject. The differentiation of this tissue was but slight in Apzos, Acer, AEsculus, Aster, Castanea, Cornus, Fagus, Falcata, Lysimachia, Menispermum, Populus and Quercus, and but little thickening occurred in the walls, although some of the species in this group develop stems in darkness that continue growth for several months. On the other hand, the species of A/zcorza that were cultivated in the dark room carried the development of the bast fibers to an advanced stage, although corresponding to Castanea and Quercus in the general activity of the cortex, epidermis and phel- logen. So far as other features are concerned, a general inspection of the structure of the etiolated stem of Aecoréa and Quercus does not show that the woody tissues of the former are carried beyond those of Quercus. Development and differentiation of the bast fibers may be carried on in etiolated stems, but as stated above it occurs in but few species. Endoderm, Pericycle, Sieve Tissue, Cambium and Generative Layers of Etiolated Stems.— The numerous questions connected with the origin and occurrence of the endoderm and pericycle made it impossible to carry out a critical study of these formations in the time at the disposal of the author, and but little study was made of the sieve cells in the various stems. The last-named tissue seemed to be differentiated but slightly in most of the etiolated stems, so far as the records at hand may be relied upon. The following striking facts concerning the activity of generative tissues may be cited at this place. A distinct cambium is not normally formed in Afvos, the stem soon ceasing to increase in thickness in light. Etiolated stems however show a diameter greater than the normal, and a generative layer arises in the customary position of the cambium, while a second is formed in the pericyclic region, which is about half the thickness of the primary generative layer. A marked cambium was present in etiolated stems of Castanea, Fagus, Hicoria and Quercus. Phytolacca formed the first of the secondary layers of cambium 252 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. characteristic of this plant, when grown in darkness. The differen- tiation of cambium is of course closely connected with the general advance of the stele from the embryonic stage, but it is difficult to connect its development with that of any single tissue in the species used in the tests. Effect of Etiolation on the Stele.—The walls of the elements of the xylem were less thickened in the etiolated than in the normal stem. In some instances the lumina of the vascular elements were smaller than the normal, in others no noticeable difference from the normal size was to be made out, and in a few, of which Quercus is an example, the lumina of the vessels were greater than the normal in cross-section. The inter-fascicular parenchyma, and the thin- walled cells throughout the xylem were smaller in etiolated stems than in the normal, while the pith or medulla attained at least nor- mal bulk and were generally greater than in normal stems. The increase of this tissue has led many investigators to attribute the altered dimensions of etiolated stems to be due to its direct action as acause. The central parenchymatous mass of a stem however, is seen to continue growth and perhaps multiplication of the elements during the embryonic stage, and if this is lengthened by any cause such as etiolation, the natural increase of the parenchyma would lead to the increase of the bulk of the stem by its unchecked action. The polystelic stems examined increased notably in diameter as a result of etiolation, the added bulk being largely made up of paren- chymatous elements, and the central lysigenous splitting did not always occur, as was found in Asparagus. A consideration of the reactions of the various tissues of the stem in darkness fails to detect a single universal and invariable reaction on the part of any tissue, except perhaps in the lessened thick- ening of the cell-walls that is found in all of the external regions of the stem. This lack of deposition of aplastic matter is very clearly a matter of continued growth and development of the etiolated axis, and is not a direct response to darkness or the absence of light. The behavior of the etiolated stem is, therefore, not reducible to its first cause by an analysis of the activity of its constituent tissues, although an examination of the components of the stem indicate the gen- eral nature of the etiolative reaction. The continued simple growth made by the plant, unaccompanied by the customary morphological development and differentiation of the tissues, may be taken to ac- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 253 count for all of the anomalous structures of plants grown in dark- ness. The general relation of this condition to light and darkness. will be taken up in the latter part of this paper. Etiolation of Leaves. — The observations of the behavior of the stem in darkness showed a uniform reduction of the branches of the main axis of the shoot, but this decreased volume, and extent of the ramifications of the stem was not seen to extend to the foliar mem- bers of the shoot. It will be found most convenient to take up these organs in groups according to their morphological character and the general habit of the plants concerned. An observance of these dis- tinctions leads to the separation of the foliar organs of pteridophytes. into two groups, viz., sterile and spore-bearing leaves. — The etiolated leaves of Lycopodium lucidulum attained less than a half of the normal size and were slightly tinged with green, due to the presence of chlorophyl, which was present in but minute quantities. An erect position was assumed (p. 199). a bole= m4 S oD | q i iE | 2) ea a ee ee ee ee ee ee Fats 4.9 | 4.15} 3.5) 3-48) 2.69] 2.54, 3.9 | 3.16) 2.55] 3.13] 2.7 | 2.79) 1.18 Sugar aia .39| .585| -166| .438 .02| .39 3.86] 2.93) 8.84 Gums 20.21/18. | 19.2 |18.1 |14.9 |14.6 |18.89 15.53/14.5 |14. |16.4 |13.1 [12.9 Starch se3 0a p72 oll PA ae eal ele | 2.2 | 4.7 4.8 |19.9 |19. |18.4 Cellulose O77 | Gale |2E-3 05:0) | 22576 20:3)120:) 412A SITS.9)/1O.4 ule aOulmAate As Protein 36.3 |53-3 | 24.4|35-7 |27-5 [43-1 |29.4 '38.1 |24.41/33.8 |21.9 |20.2 |21.9 Ash 5-9 |10.9 Diet eA 2) O.36 || O.2aG)5.e5e3, NO. le Se eleseoeledee Residue 21.7 | 2.9 | 28.8|12.9 |24.4 | 9.3 |16.9 | 7.4 |29.3 |I9. |26.4 132.7 |36. Nitrogen 5-8 | 8.5 | 3.9] 5-7 | 4.4 | 69 4.7 | 61 | 3.9 | 5-4 |3:5 | 3-2 135. The proportion of fats is seen to decrease in the leaves during etiolation, to remain stationary in the hypocotyl, to decrease in the stem, and increase in the roots. The proportion of sugar undergoes a marked decrease during eti- ‘ olation throughout the entire plant, the greatest percentage remaining 304 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. in the cotyledons. The amount of starch was greatest in etiolated leaves, normal hypocotyls, etiolated first internodes, normal inter- nodes above etiolated roots, and normal cotyledons. Cellulose was present in smaller proportions in etiolated leaves, hypocotyls and lower internodes, and in greater proportions in etiolated upper internodes, roots and cotyledons. ‘These determinations of cellulose are undoubtedly faulty, especially in the stems. Protein was present in greater proportion in etiolated leaves, hypocotyls, stems and roots, and in smaller proportion in cotyledons than in the normal. These results do not agree with those obtained later by Palladin (p. 23). The amount of ash in a given weight of mate-_ rial was greatest in etiolated leaves, hypocotyls, internodes and roots, and less in cotyledons than in the normal, which is in general agree- ment with the results obtained in my own analyses. Rzentkowsky’s™ examination of seedlings of Phaseolus multiflorus led him to con- clude that etiolated plants do not take up mineral substances from the substratum a conclusion which is undoubtedly wrong, as demon- strated by André and myself. THE RATE AND MODE OF GROWTH AS AFFECTED BY LIGHT AND DARKNESS.™ The rate of growth of any organism varies in such manner that a more or less irregular acceleration is shown during the earlier stages of development until a maximum of increase is reached, when a simi- lar diminution brings the action to zero. Minor maxima are also shown before or after the major in some instances. In addition to this major movement which traces the curve of the grand period of growth of the organism, minor deviations occur, which may be due to alterations in temperature, food-supply, moisture and other causes. Running through the major and minor alterations as above there are seen to be more or less regularly recurring accelerations and dimi- nutions of the rate, which have been shown to be due to a rhythm 204 Rzentkowsky, T. Untersuchung ueber Entwickelung des etiolirten Phaseolus multéfiorus. Mitth. d. Universitat z. Warschau. 1875. Abstract by Batalin in Bot. Jahresber. 4: 745. 1875. : 205 Presented before the Botanical Society of America, at Washington, I). C., Jan. I, 1903. MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 305 set up by inherent causes. Baranetzky concluded that the rhythm exhibited by plants in a dark room was an after-effect due to the lasting influence of alternating exposures to daylight and darkness, and pointed out that in continued confinement the diurnal periodicity was lost and the variations no longer occurred with sufficient regu- larity to constitute a rhythm. Sachs seems to have been the first to formulate the opinion that light retards growth and his position with regard to minor periodicities may be best given in his own words: ‘*J, on the contrary, am of the opinion that in the plant, or at any rate in its growing parts, periodic variations occur in some way quite independent of variations of temperature and light; and these, as I conclude from Baranetsky’s observations, may continue for periods of very different lengths. If now the plant is subjected to the regular alternation of day and night, and the variations of temperature are very small, the above-mentioned influences on growth make their appearance, by which its maximum is transferred to the morning hours, and its minimum to the evening, the above-mentioned period- icity arising from purely internal causes being concerned as the weaker factor in a definite daily period of time.” Sachs *” did not agree with Baranetzky however in the assertion that the daily periodicity of plants in darkness was an after-effect of light or temperature, and Vines took the position that the coincidence of the variations with those of normally illuminated plants was prob- ably accidental, although he conceded that the daily periodicity of a plant continued for several days after it had been confined in a dark chamber. Both Sachs and Vines” held that it was improbable that the periodicity of fully etiolated plants was due to after-effects ; indeed Sachs adduces the fact of periodicity in such a plant as a refutation of the theory of after-effects in the matter, and likens it to the starting of pendulum spontaneously after it had come to rest. It is to be seen however, that geotropic and other stimulatory effects may be hindered and the response delivered long afterward, and Darwin and Pertz have shown by a beautiful series of experi- ments that geotropic rhythms may be induced in stems, which are maintained after the stimulus is withdrawn. ‘The position taken by 206 Baranetzky, J. Die tagliche Periodicitét im Langenwachstum der Stengel. Mem. d. l’Acad. Imp. d. Sc. de St. Petersbourg. Ser. 7. 1879. 207 Sachs. Physiology of Plants. Eng. Ed., p. 560. 1887. 208 Vines, S. H. Physiology of Plants. p. 403. 1886, 306 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. Baranetzky therefore, that the periodicity of growth maintained by a plant after it has been deprived of illumination, is an after-effect, and which supported by Vines seems well defended, to whatever this daily periodicity may be due. Furthermore, it might be expected an organ would carry on growth with a rhythm due to the action of factors concerned with an extremely early stage of its existence. Itis probable that the behavior of any single species however, may not be safely predicted. Thus the auxanometric measurements of Av7saema triphyllum disclose a rhythmic action, quite as well marked as that of the normal plant, when grown in a dark room at constant tem- peratures (pp. 68-70). The measurements of a leaf of Quamasza during a continuous period of fifty days in a dark room at a constant temperature (p. 86) gave opportunity for observations of growth under conditions in which the food-supply, moisture, temperature and darkness were practically uniform. A consideration of the facts shown in the curve plotted from the auxanometric data brings to light the fact that the variations in this instance were exceedingly irregular, and seemingly subject to no rule of any kind. No control observations were made on this species for the purpose of obtaining the variations in normally grown plants. The variations of Arzsaema, on the other hand, were fairly parallel to those of the specimens under normal alternations of daylight and darkness with the temperature fluctuating. The observations described in this memoir, together with the records of previous investigations upon etiolation demonstrate most conclusively that the growth of the aérial organs of green seed plants in darkness is not accompanied by the usual degree of differentiation of the several tissues. The amount of growth, or increase in volume, that may be accomplished by the shoot by the extension of the im- perfectly developed tissues in the absence of illumination is subject to great variation. In many species the total length, diameter and volume of the etiolated shoot, and its various members is not so great as in the normal, and the rate of growth may not be so rapid as in the normal. The buds and seeds of a number of species, and also the spores of many pteridophytes will not awaken from a resting condition and begin the growth leading to the development of the shoot except under the influence of light. On the other hand, some species of the higher plants, as well as some of the lower forms, carry on the growth of the main axis at an accelerated rate in dark- “MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 307 ness, and to such an extent that shoots are formed which may exceed the normal both in length and diameter. It is obvious that, in the above phenomena, the effects are due to the stimulating influence of light, and of darkness (or absence of light). The differentiation of the tissues, and the development of certain reproductive bodies constitute positive reactions to the stimu- lating influence of the rays, and the exaggerated elongations shown by many shoots is a response to darkness, which may be adapta- tional in its character, and which might serve to lift the chlorophyl- bearing organs past an imaginary obstruction into illumination. The failure of a large proportion of the forms examined to make an accel- erated or exaggerated growth when freed from the influence of light, even when provided with an adequate food supply, shows that light has no invariable and universal relation to increase in length, or thickness, or to the multiplication or increase in volume of the sep- arate cells. When a green plant is suddenly deprived of illumination a marked acceleration of the rate of elongation ensues, and a diminution ensues when a plant is brought from darkness into light, which Pfeffer, as a result of a consideration of the investigations upon this point, esti- mates to amount to changes in the rate not greater than fifty per cent. of the existing rate. Many of the observations bearing upon this point were made with plants which do not exhibit an abnormal elon- gation in darkness. In my own investigations the peduncles and scapes of Arisaema, which had ceased to make an amount of growth equal to a total of 1 mm. per day, underwent a comparatively enor- mous acceleration which reached a maximum about twenty-four hours after being deprived of illumination, and then decreased to a minimum correspondent to the original rate in about a hundred hours. Arisaema is a plant which shows a marked adaptational elongation in darkness during etiolation, and this increase may only be ascribed to the stimulative action of darkness, since it would be an obvious ab- surdity to ascribe such an enormous increase in rate to the absence of any direct or paratonic action of light. This seems still more justifiable when it is pointed out that the rate of growth is never di- minished by the action of light to the extent that it is by temperature. It is clear therefore, that no evidence is afforded by the behavior of plants in darkness to support the conclusion that light directly affects the rate of growth, since not all species exhibit increased 308 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. growth when freed from its influence, and the accelerated rate shown by mature organs when placed in darkness may be only ascribed to a stimulative action and an adaptational response. Another aspect of the effect of light on growth remains to be considered. It is well established by hundreds of observations that the rate of growth of a large number of normal greenorgans, or of shoots, decreases when deprived of illumination for a period, such as that of an ordinary night, or even briefer, and then suddenly exposed to the action of the rays. This has given rise to the generalization that light exerts a direct or paratonic action on growth. Now it has been demonstrated most conclusively that light does not exert any direct effect on the growing region either in the way of influencing cell-division, or the processes depending upon the motility of the protoplasm, or of the material entering into the construction of the membranes. In fact none of the phenomena of etiolation or of diminished growth in light may be ascribed to the direct influence of light upon the tissues or cells concerned but rather upon the organism as awhole. The lessened increase in volume taken into account in measurements of the growth of plants exposed to the action of light may be due to one or both of the following causes. First, it is to be pointed out that the action of the rays on any mass of proto- plasm is to accelerate the rate of transpiration, and the loss of water may be sufficient to cause a decrease in bulk, which might neutralize the outward effects of the actual constructive processes, which may continue uninterrupted during the apparent decrease or cessation of growth. On the other hand, it is entirely probable that some of the apparent retardation may not be due to a direct mechanical influence of the rays, but is a stimulative reaction. That the slowing down of the rate of growth under the influence of light is an irritable response is supported by the behavior of plants exposed to continuous illumination for long periods, such as might occur in the polar re- gions, and which has also been brought about in several series of experiments. Inthe former instance the specimens grown in locali- ties in which the daylight period embraces the entire vegetative sea- son of several months, the shoot and its members did not exhibit an increase, which either in rate or amount would justify the assertion of a direct retarding influence. The same results have been attained in another form by the exposure of growing plants to continuous ex- posure to electrical illumination, or to an illumination in which day- MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 309 light was supplemented by nocturnal illumination from electric arcs, or flames. In all such instances the amount of growth, as indicated by the length of the shoots and of the separate members, was greater than under ordinary conditions of alternating daylight and darkness. If light exerted a direct retarding, or paratonic influence upon the processes of growth, such results would be impossible. On the other hand, if the slowing down of the increase of shoots when sud- denly exposed to light is due to a stimulative action the continued il- lumination of a plant to the action of the rays would soon result in an accommodation to the continuance of the stimulation, and the be- havior of the plant after becoming attuned to increased illumination would embrace some features due to the altered conditions of nutri- tion, and to the supposedly disintegrating effects of the blue-violet rays on chlorophyl and other substances. INDEX TO CONTENTS, Abutilon, 22 Acer, 247, 249, 251, 295 ctrctnatum, 188 rubrum, 188-190, 239, 240, 241, 242, 266 AEFsculus, 218, 224, 245, 247, 249, 257, 268 Hippocastanum, 190, 191-194, 196, 230, 231, 239; 290 Agave Americana, 37, 235 Allium, 214 Cepa, 8, 38 Neapolitanum, 37, 38, 39, 255, 256 porrium, 10, 39 vineale, 39, 40, 255, 256 Allosorus sagittatus, 34 Aloe obliqguum, 7 Amaryllis, 214, 269 formosissima, 16 Johnsonit, 40 Amelung, E., researches of, 10 (Ueber Etiolement. Flora. 78: 204, 1894), 26, 273 Amorphophallus, 48, 220, 257, 269, 300 Fzviert, 40, 41, 42 Anchusa officinalis, 22 Andre, G. (Action de la temperature sur V’absorption minerale chez les plantes etiolées. Compt. Rend. 134: 668-671, 1902), 302 Aneimia Phyllitidis, 34. Antirrhinum majus, 17 Aptos, 222, 224, 227, 228, 229, 246, 247, 251, 268 Apios, 42, 46, 194 Apium graveolens, 8 Afplectrum, 215, 221, 255, 256, 269 spicatum, 47, 48 Afposeris, 265 foetida, 262 Aquatics, etiolation of, 215-218 Arisaema, 42, 215, 268, 271, 286, 296, 297, 301 Dracontium, 48-50, triphyllum, 50-71, 296, 306, 307 Aristolochia, 71-73, 215, 219, 222, 225, 226, 228, 229, 264 Arodes (see Calla), 220, 258 Arum maculatum, 221, 231 Askenasy, E. (Ueber der Einfluss des Lichtes auf die Farbe der Bliithen. Bot. Zeitung. 34: 1, 27, 1876), 17, 273 Asparagus, 247, 252, 264, 268 officinalis, 73-75, 238, 263, 295 Aspidium molle, 34 spinulosum, 34. Asplenium alatum, 34 220 220 eon 22 On 200, Gene a7 22 - yy 310 AND TO LITERATURE: Asplenium lasiopterts, 34 platyneuron, 75-78, 253, 278, 296 Aster divaricatus, 77,79, 243, 246, 249, 251, 263, 264, 286 patulus, 30 Atriplex hortensis, 30 Avena sativa, 6 Baccharis halimtfolia, 80, 239,"240, 266 Baeomyces, 21 Bailey, on influence of electrical illumina- tion, 293 on effect of light on Petunia, 276 Bailey, L. H. (Some preliminary studies of the influence of the electric arc lamp upon greenhouse plants. Bull. No. 30. Cornell Univ. Agric. Exp. Station. 1891), 210 Second report upon electro-horticul- ture. Bull. No. 42. Cornell Univ. Agric. Exp. Station. 1892), 210 Third report upon electro-horticul- ture. Bull. No. 55, Cornell Univ. Agric. Exp. Station. 1893), 210 Baranetzky, J. (Die selbstaindige tagliche Periodicitit im Liangenwachstum der Internodien. Bot. Zeitung. 35: 639, 1877), 17, 305 Batalin, A. (Ueber die Wirkung des Lichtes auf die Entwickelung der Blat- ter. Bot. Zeitung. 29: 669, 1871), 11, 13, 283 Beans (see Phaseolus), 1, 7 Beech (see Fagus), 26 Beet (see Beta vulgaris), 211 Begonias, 8, 274 Benecke, W. (Ueber Cultur Bedungun- gen einiger Algen. Bot. Zeitung. 56: 1st Abth. 89, 1898), 33 Berthold, G. (Beitrige zur Morphologie und Physiologie der Meeresalgen. Jahrb. f. Wiss. Bot. 13: 569. 1883), 25 Beta vulgaris, 8, 9, 262 Beulaygue, L. (Recherches physiolog- iques sur le dévelloppement de la fleur. Montpelier. 1901), 275, 290 Bicuculla, 221, 259, 260 cucullaria, 80 Boehm (Die Nahrstotfe 1886), 20, 283 Bombax, 234 Bonnet, Ch. (Usage des feuilles. p. 254. 1754), 1 Bonnier, G. (Influence de la lumiere électrique continue sur la forme et la structure des plantes. Rev. Gen. d. Bot. 7: 241, 289, 332, 407. 1895), 28, 194, 196 der Pflanze. INDEX. Bonnier, on influence of electric illumina- tion on plants, 205, 206, 207, 208, 210, 275, 292 Bonnier, on etiolates, 284, 293 Bonorden (Handbuch _ der Mykologie. 1851), 51 Borodin, J (Physiologischer Untersuch- ung iiber die Athmung der _ beblat- terten Sprosse. Arb. d. St. Petersb. Ges. d. Naturf. 7: 1-114, 1876. Ab- stract in Bot. Jahresber. 4: 919. 1876), 16. (Ueber die Wirkung des Lichtes auf einige héhere Kryptogamen. Mel. Biol. 6: 529. 1867), 34 Botanical Convention, Weekly, 280 Botanical Society of America, 304 Botrychium obliguum, 80-82, 243, 244, 255, 278 Botrytis cinerea, 22 Bowitea, 214, 222, 226, 227, 228, 229, 236, 238, 247, 256, 268 volubilis, 82-84 Brassica, 9, 265, 271 campestris, 83-85, 243, 244 Napus, 227 Brefeld (Ueber die Bedeutung des Lichtes fiir die Entwickelung der Pilze. Bot. Zeitung. 35 : 386. 1877, also Sitzungsber. d. Ges. Naturf. z. Berlin. April, 1877), 17 Brenner, W. (Untersuchungen an einigen Fettpflanzen. Flora. 87: 387. 1900), 32, 237 Brown and Escombe (The influence of varying amounts of carbon dioxide in the air on the photosynthetic processes of leaves and on the mode of growth of plants. Phil. Trans. Roy. Soc. 193: 278. 1900, abstract in Nature. 66: 621. 1902), 274, 292 Bryonia, 8, 9, 230 dioica, 222, 224, 230 Buchenau, F. (Die Wachstumsverhalt- nisse von; Bowzea volubilis. Ukr. fil., Abhandl. d. Naturw. Ver. z. Bremen. 6: 433), 84 Bulbs, etiolation of, 216, 217 Bullot, E. (Sur la croissance et les cour- bes du Phycomyces. Ann. d.1. Soc. Mi- croscopique d. Belge. 21: 84. 1897), 31 Busch, H. (Untersuchungen ueber die Frage ob das Licht zu den unmmittel- baren Ledensbedingungen der Pflanzen, oder einzelner Pflanzenorgane gehort. Inaug. Diss. Bremen. 1889), 23 allgemeine Cabomba, 217 Cactus spectosus, 8 Caladium esculentum, 85, 86, 215, 219, 257, 258 Calla, 215, 257, 258 (cultivated), 86, 87 palustris, 87, 216 311 Camassta (see Quamasia), 87, 89, 256 Cambium in etiolated stems, 251 Canna, 219, 257 (cultivated), 88-91 Cannabis sativa, 12, 23, 30 Capsella, 238 Carpenter, M. B. (Vegetable physiology, and systematic botany. p.198. 1848), 6 Carpinus Betulus, 206 Castanea dentata, 91-93, 99, 230, 231, 239, 250 Caulerpa, 25, 216, 217, 218 Ceratophyllum, 27, 217, 218 Ceratopterts thalictroides, 34 Cereals, etiolation of, 115 Chapin, P. (Einfluss der Kohlensaure auf das Wachstum. Flora. gt: 348- 379- 1902), 275 Chara, 217 Chetranthus Chetrit, 9 Chemical composition, influence of etiola- tion on, 300-304 Chenopodium album, 30 Chestnut (see Castanea), 91-93 Cicuta, 259 maculata, 93-94 vtirosa, § Claytonia Virgintca, 94, 95 Climbing plants, etiolation of, 222-230 Cocoanut (see Cocos nuctfera), 95-97 Cocos, 247 nucifera, 95-97, 230, 231, 257, 258 Cotx Lachryma-Jobi, 97, 230, 231, 267 Collenchymatous layers in etiolated stems, 249 Colocasia, 97, 257, 258 Colutea arborescens, 29 Coprinus stercoriartus, 279 Corbett, on the effect of artificial illumi- nation on plants, 275 Corbett, L. C. (A study of the effect of incandescent gas-light upon growth. Bull. No. 62. W. Virginia Exp. Station. 1899), 211, 293 Corms, etiolation of, 216, 217 Cornus alternifolia, 97-100, 115, 189, 239, 240, 242, 246, 250, 251, 266, 295 Coronilla, 210 Crataegus monogyna, 16 Crocus, 8 vernus, 271 Cucurbita, 8, O;710;2 14; 20,307 220,02 71, 272; 273, 274 Melopepo, 22 Curtel, M. Y. (Recherches physiologiques sur la fleur. Ann. Sc. Nat. VIII. 6: 220. 1897), 29 Cyclamen, 100, 101, 219, 259, 260 Cynoglossum officinale, 22 Cypripedium, 264, 267 montanum, IO1, 102, 243 Dahlia variabilis, 8, 22 Darkness-rigor, 11, 12 312 Dark room at N. Y. Bot. Garden, 36 Dark-chamber, portable, 36 Darwin, F. (Etiolation asa phenomenon of adaptation. Jour. Roy. Hort. Soc. 19: 345. 1896), 28, 284 researches of, 305 Davy, H. (Elements of agricultural chem- istry. pp. 208, 209. 1815), 4 De Bary (Recherches sur le Te selgane | ment de quelques champignons para- sites. Ann. Sc. Nat. IV. 20: 40, 54. 1863), 5 DeCandolle, A. P. (Expériences relatives & Vinfluence de la lumiere sur quel- ques végétaux. Mem. Math. et. phys. Inst. Nat. Paris. 1: 332. 1806. Presented in 1799), 3 (Physiologie végeétale, 3 : 1069. 1832), 4, 280, 300 DeCandolle, C. (Etude de l’action des rayons ultra-violet sur la formation des fleurs. Arch. des Sc. Phys. et Nat. Genéve. 28: 265. 1892), 24, 272, 291 Deherain (On influence of electrical il- lumination on plants. Ann. Agron. 7: 551. 1881), 209 De Lamarliére, L. G. (Recherches phy- siologiques sur les feuilles dévellopées a V’ombre et au soleil. Rev. Gen. d. Bot. 4: 481. 1892), 24 Delphinium exaltatum, 102, 103, 243, 244, 263, 264 De Saussure, Th. (De l’influence de la lumiere sur la germination. Recherches chimiques sur la végétation. p. 21. 1804), 3 Detmer, W. (Die Formbildung etiolirter Pflanzen, in Vergleichende Physio- logie des Keimungsprocesses der Samen. pp. 464-478. 1880), 234 (Ueber den Einfluss verschiedener Lichtintensitaten auf die Entwick- elung feiniger Pflanzen. Landw. Versuchss. 16: 205. 1873. See also Detmer, Practical Plant Physiology, pp- 404-411. 1898, and Detmer, Vergleichende Physiologie d. Kei- mungsprocesses d. Samen. 1880),14 (Ueber Photoepinastie de Blatter. Bot. Zeitung. 40: 787. 1882), 14 Development and differentiation, effect of etiolation on, 246-247 Dicotyledons, leaves of, etiolation of, 259- 263 Dictyostelium mucoroides, 279, 280 Digitalis purpurea, v7 Dioscorea Batatas, 9, 222, 226 Dolichospermum, 274 Draper (Chemistry of plants. York), 6 Dufour, L. (Influence de la lumiére sur la structure des feuilles. Bull. Bot. Soc. dy brance. Ul 8): 3925, 1S86));220 1844. New INDEX. Duhamel du Monceau (Des plantes étio- lées, in La physique des arbres, 2: 155),2 Duration of etiolated organs, 218-222 Dutrochet (Rapport sur un mémoire de M. Payer intitulé: Mémoire sur la ten- dance des racines a fuir la lumiére. Ann. Se: Nat: TEL. 2:66. 1844), 6 Echallium elaterium, 22 Electric illumination, effects of, 27, 28 Elfving, F. (Studien ueber die Einwir- kung des Lichts auf die Pilze. Hel- singfors. 18g0), 18, 23 Ellis, D. (Farther inquires into the changes induced in atmospheric air by the germination of seeds, the vegeta- tion of plants and.the respiration of animals. p. 132. 1811), 281 Elodea, 27, 217 Endive, 211 Endoderm, in etiolated stems, 251 Epidermal cells on etiolated stems, 247- 248 Efpiphegus, 270 Equisetum arvense, 3 103, 104, dls 278 Ervum lens, 297, 298 Erythrine, 7 Erythronium Hartwegt, 104, 255 Escombe, Brown and (The influence of varying amounts of carbon dioxide in the air on the photosynthetic processes of leaves and on the mode of growth. Phil. Trans. Roy. Soc. 193: 278. 1900), 274 Etiolation, nature of, 280-283 Faba vulgaris, 30 Fagopyrum, 9 Fagus, 246, 250, 251 Americana, 105, 239, 242, 267 sylvatica, 195, 196, 239 Falcata comosa, 105, 106, 222, 224, 226, 229, 251 Famintzin, A. (Die Wirkung des Lichts auf das Wachsen keimenden Kresse. Mem. Acad. St. Petersb. 8: p. 13. No. 15, 1865), 13 (Die Wirkung des Lichtes auf Algen und einige andere ihnen nahe ver- wandte Organismen. Jahrb. f. wiss. Bob. 6): 1 1867)),.02 Ficus elasttiea, 210 Filix fragilis, 106, 220, 278 Flammarion, C. (Physical and meteoro- logical researches, principally upon solar rays, made at the station of agri- cultural climatology. Juvisy, France, Abstr. Exper. Sta. Record. 10: 103. 1898), 211 Flowers, etiolation of, 268-178 Frank, B. (Lehrbuch der Botanik. 1: 389. 1892),:2 106, 194-197, 226, INDEX. Frank, on the nature of etiolation, 283-284 Frank, A. B. (Ueber die Lage und Rich- tung schwimmender und _ submerser Pflanzentheile. Cohn’s Beitr. z. Biol. d. Pflanze. 1: Hft. 2, 31-86. 1872), 216 Frankfurt, S. (Ueber die Zusammenset- zung der Samen und etiolirten Keim- pflanzen. Inaug. Diss. Wilna. 1893), 2 Fries, E. (Systema mycologicum.1: 502. 1821; also3: 265. 1839; and Syst. Orb. Veg! 8s 212+ 1825), 5 Fuchsias, 274 Galium circaezans, 24, 106, 109, 243, 263, 269 Gardner (London, Edinburgh and Dublin Philosophical Magazine), 6 Gasterta disticha, 109-112, 219, 226, 265 Generative layers in etiolated stems, 251 Gies, Kirkwood and (Chemical studies of the cocoanut and its changes during germination. Bull. Torr. Bot. Club. 29: 321-359. 1902), 95 Gleditsia triacanthos, 113, 230, 233; 239 Gloxinia hybrida, 22 Godlewsky, E. (Abhingigkeit der Starke- bildung in den Chlorophyllkérnern von den Kohlensduregehalt der Luft. Flora. 56: 378. 1873), 14 (Die Art und Weise der Wachstums- retardirenden Lichtwirkung und die Wachstumstheorein. Anzeig. d. Akad. d. Wiss. z. Krakau, Résumés. p- 166. 1890), 20 researches of, 283, 284 (Studien iiber das Wachstum der Pflanzen. Abh. d Krakauer Akad. d. Wiss. Math.-Naturw. Cl. 23: 1- 157, abstract by Rothert, Bot. Cen- tralbl. 55: 34. 1893), 25 (Ueber die biologische Bedeutung der Etiolirungsercheinungen. Biol. Centratblatt. 9: 481. 1889), 20 (Ueber die Beeinflussung des Wach- stums der Pflanzen durch aeussere Factoren. Anzeig. d. Akad. d. Wiss. z. Krakau, Résumés, p. 206. 1890),20 (Zur Kenntniss der Ursachen der For- manderung etiolirter Pflanzen. Bot. Zeitung. 37 : 81, 97, 113,137- 1879), I Goebel (Influence of light, Organog- raphy of Plants. Eng. Ed., 227-259. 1900), 204 (On relation of illumination to sporo- phylls and leaves. Flora. 80: 116, 1895), 278 Goebel, G. (Organography of Plants. Part I., pp. 231, 244, 248. 1900), 215, 230,272 Goebel, K. (Organographie der Pflanzen. Part II.,-p.432. 1898), 200 Part Il. p. 499. 1898), 262 313 Goebel (Ueber die Einwirkung des Lichtes auf die Gestaltung der Kakteen und anderer Pflanze. Flora. 80: 96. 1895), 26 Goff, E. S. (Influence of light on the length of the hypocotyls in Indian corn. Science. 13: 395. I901), 32 Grantz, F. (Ueber den Einfluss des Lichtes auf die Entwickelung einiger Pilze. Leipzig. 1898), 18, 30 Green, J. R. (Action of light on dias- tase, and its biological significance. Proc. Roy. Soc. 188: 169. 1897), 29 Gris, A. (De étiolement, Recherches mi- croscopiques sur la chlorophylle. Ann. Nats ScreLV.07i:) 207. kosy ey Guarequi, 197, 198 Guillemin, C. M. (Production de la chlorophylle, et direction des tiges sous linfluence des rayons ultra-violets, cal- orifiques, et lumineux du spectre solaire. Ann. Se: NateLV: 7154. 1857) 7 Hales, S. (Statical Essays. 1: 334. 1727 ; also p. 336; ed. of 1769), 1, 280 Heckel, E. (Du mouvement végétal. Paris. 1875. Review by Pfeffer in Bot. Zeitung. 34: 9. 1876), 17 Helianthus annuus, 8, 9, 16, 25 tuberosus, 30 Hellebore, 267 Flelleborus niger, 28, 208 Hemerocallis, 113, 214, 255 Herbaceous biennials and perennials, etio- lation of, 243-246 Hicorta, 113-114, 189, 218, 224, 250, 251 mint~ma, 114-115, 230, 239 ovata, 115-116, 230, 239 Hieractum Pilosella, 32 Hill, J. A. (Anatomy of plants. 1759), 242 HHippuris vulgaris, 217 Hordeum vulgare, 6 Horse-chestnut (See AZsculus) 26 Humulus, § Lupulus, 30 Humboldt, observations of, 2 Hyacinthus, 8, 9, 116-117, 214, 255, 256, 268 p. 213. orientalis, 17, 27 Hydrastis Canadensis, 117, 118, 243, 244, 246, 247, 259, 260, 263, 269 fTydrocharis Morsus-ranae, 216 Hypopitys Hypopitys, 119, 243, 269, 270, 277 Hlura crepitans, 243 Hymenomycetes, relation to light, 5 Ibervillea Sonorae, 197, 198, 222, 224, 229, 238, 247 Illumination of etiolated plants, 295, 295 Impatiens, 274. Inflorescences, etiolation of, 268-278 Ipomaea, 226, 262, 265 314 Ipomaea Batatas, 120, 243 purpurea, 10, 223 Tris, 8, 120-123, 255, 256 pumila, 271 Istvanfh, G. (Influence of light upon the development of flowers. 1890), 22 Jost, on etiolation, 290 Jost, L. (Ueber den Einfluss des Lichtes auf das Knospentreiben der Roth- buche. Ber. d. Deut. Bot. Ges. 12: 188. 1894), 26, 195 (Ueber die Abhingigkeit des Laub- blattes von seiner Assimilations- thatigkeit. Jahrb. f. wiss. Bot. 27: 403. 1895), 26 Jalapa, 9 Kalanchoé, 274 Kalmia latifolia, 210 Karsten, H. (Die Einwirkung des Lichtes auf das Wachstum der Pflanzen beo- | bachtet bei Keimung der Schmink- bohnen. Inaug. Diss. Jena. 1870), 13, 302, 303 ( Vergleichenden Untersuchungen von in Lichte und Dunkeln gezogenen Pflanzen. Der Chem. Ackersman. INO? 3:) 1870) 503 Kirkwood and Gies (Chemical studies of the cocoanut and its changes during germination. Bull. Torr. Bot. Club. 29: 321-359. 1902), 95 Klebs, G. (Die Bedingungen der Fort- pflanzung bei einigen Algen und Pilzen. 1896), 28 (Zur Physiologie der Fortpflanzung einiger Pilze. Jahrb. f. wiss. Bot. 35: 140. I9g00), 31 Klein, L. (Ueber die Ursachen der aus- schliesslich nachtlichen Sporenbildung von Botrytis cinerea. Bot. Zeitung. 43: 6. 1885), 22 Klemm ( Desorganizationserscheinungun- gen der Zelle. Jahrb. f. wiss. Bot. 28: 627. 1895), 27 Klemm, P. (Ueber Caulerpa prolifera. Flora. 77: 460. 1893)),.25 Knight, T. A. (On a method of forcing rhubarb in pots. Trans. Hort. Soc. Lond. 3: 154. 1820. See also a selec- tion from the physiological and horti- cultural papers published in the Trans- actions of the Royal and Horticultural Societies. 1841), 4 Koch (Abnorme Aenderungen wachsender Pflanzenorgane durch Beschattung. Ber- lin. 1872), 15 Krabbe, G. (Entwickelung, Sprossung und Theilung einiger Flechten Apothe- cien. Bot. Zeitung. 40: 93. 1882), 22 Kraus, C. (Ueber einige Beziehungen des Lichtes zur Form und Stoffbil- INDEX. dung der Pflanzen. Flora. 61: 145. 1878), 19, 235 (Ueber einige Beziehungen’ des Lichtes zur Form- und Stoffbildung der Pflanzen. Flora. 61: 145. 1878), 235 (Ursachen der Formianderung etio- lirter Pflanzen. Bot. Zeitung. 37: 332. 1879), 15 (Pflanzenphysiologischen Untersuch- ungen, VI. Wachstum und Chloro- phyllbildung. Flora, 58: 346. 1875), is Kraus, G. (Ueber die Ursachen der Formanderungen etiolirender Pflanzen. Jahrb. wiss. Bot. 7: 209. 1869), 11 Kraus, G. (Ueber die Wasservertheilung in der Pflanze. I. Halle. 1879; III. Die tagliche Schwellungsperiode der Pflanze. 1881; IV. Die Aciditit des Zell- saftes. 1884), 11 Kraus, G. (Versuche mit Pflanzen im farbigen Licht. Abdruck a. d. Sitzungs- ber. d. Naturf. Ges. z. Halle. 1876), 11 Kraus, G., investigations of, 281, 282, 283 Lasareff, N. (Ueber die Wirkung des Etiolirens auf die Form der Stengel. Beil. z. Protocoll d. 45th Sitzung. d. Naturf. Ges. a. d. Univ. z. Kasan. Ab- stract in Bot. Jahresber. 2: 775. 1874), 14, 234 Leaves, etiolation of, 253-255, 263-268 with parallel venation, etiolation of, 255, 256 Leavitt, R. G. (Subterranean plants of Epiphegus. Bot. Gazette. 33: 376. 1902), 270 Lendner, A. (Des influences combinées de la lumiere et du substratum sur le devéloppement des champignons. Ann. Se. Nat. VIII. 3: 60. 1867), 29 Lenticels, on etiolated stems, 247 Lepidium sativum, etiolation of, 3, 11, 12 Lettuce, 210, 211 Leveille (Considerations mycologiques. 1846), 5 Light, manifold relations to shoot, 202— 204 phototropic effect of, 203 modes of influence upon plants, 201 morphogenic influence of, 204, 205, 206 Link, D. H. F. (Grundlehren der Anat. u. Physiol. d. Pflanzen, p. 291. 1807), Linnaeus, observations of, 2 Linum grandifiorum, 9 Livingston, B. E. (Further notes on the physiology of polymorphism of green algae. Bot. Gazette. 32: 298. 1901), 32 Lobelia erinus, 272 INDEX. Lupinus albus, 14, 293 Lycopodium lucidulum, 198, 199, 253 Lysimachta terrestris, 121-125, 234, 244, 246, 247, 251, 263, 267 MacDougal, D. T. (Critical points in the relations of light to plants; read before the Society for Plant Phys- iology and Morphology, Baltimore Meeting, Dec. 28, 1900; abstract in-Science. 13: 252. 1901), 202,216 Investigations of, 35 (Practical text-book of plant physiol- ogy. pp. 291, 292. Igo1), 88, 201 (Relation of the growth of foliage leaves and the chlorophyl func- tions Jour.” Linn, ‘Soc: | 31: 526. 1896), 28, 292 (Seedling of Arzsaema. Torreya. 1: 2, \IGOV), 50, 221 (Symbiotic saprophytism. Annals of Botany. 13: 1. 1899), 47 (Vegetative propagation of Lysz- machia terrestris. Bull. N. Y. Bot. Garden. 2: No. 6. p.82. 1901), 125 Maige, A. (Recherches biologiques sur les plantes rampantes. Ann. Sc. Nat. Bot. Ser. 8. Ii: 345.) 1900));°325. 215 Manda suaveolens, 226 Maple, 26 Marchantiaceae, germination of gemmae of, 28 Marchantia polymorpha, 29, 294. Mariolle, A., drawings by, 37 Mees, observations of, 2 Menispermum Canadense, 125-128, 220, 222 OTA W225 220, 229, 220, 240, +247; 248, 249, 251 Mentha crispa, 22 piperita, 22 sativa, 32 Mer, E. (Recherches sur les anomalies de dimensions des entre-noeuds et de feuilles étiolées. Bull. Bot. Soc. d. France. 22: 190. 1875), 16 Miagrum sativum, etiolation of, 3 Milde. (Zur Entwickelungsgeschichte der Equiseten und Rhizocarpen. Nova Acta GAR Win G. 22102), 24 ayes uniflora (see Tritelia) 182, 184, 256, 209 Mimosa, 12, 26 Mimulus Tillingtt, 274. Minnesota, University of, at, 36 Mirabilis, 9 Mobius, M. (Ueber einige an Wasser- pflanzen beobachtete Reizerscheinun- gen. Biol. Centralb. 15: 1. 1895), 27 Monocotyledons, petiolate leaves, etiola- tion of, 257, 259 experiments Montagne (Esquisse organographique et physiologique sur la classe champig- nons. 1841), 5 . 315 Morphogenic influence of light and dark- - ness, 285 Morren, E. (La lumiere et la vegetation. La Belgique Horticole. 13: 165. 1863), 300 Mucor, 29, 31 Myriophyllum, 27 spicatum, 217 Nabowick, A. (Wie die Fahigkeit der ho- heren Pflanzen zum anaeroben Wach- stum zu beweisen und zu demonstriren ist. Ber. d. Deut. Bot. Ges. 19: 222. 1901), 34 Natias major, 217 Narcissus, 214, 255, 256, 268, 269, 289 poeticus, 129 Tazetta, 128, 129 Neljubow, D. (Ueber die horizontale nu- tation der Stengel von Pisum sativum und einiger anderen Pflanzen. Beih. Bot. Centralb. 10: 128. 1901), 34 New York Botanical Garden, experiments in, 36 Nicotiana, 8, 274 rustica, 271 Noll, F, (Ueber das Etiolement. Separate a. d. Sitzungsber. d. Nied-Rhein. Gesell. f. Natur- u. Heilkunde z. Bonn. 1901), 33, 216, 284 (Ueber rotirenden Nutation an etio- lirenden Keimpflanzen, Bot. Zei- tung. 43: 664. 1885), 22 (Ueber die Einfluss der Lage auf die morphologische Ausbildung eini- ger Siphoneen. Arb. a. d. Bot. Inst. i. Wurzburg. 3: 466. 1888), 25 Nuphar luteum, 215 Nymphaea, 215 Observations, scope of, 35 Oedogonium, 28 Onoclea sensibilis, 129, 130, 220, 278 Opuntia, 219, 247 Opuntia, 131, 132, 236, 237, 264 leucotriche, 237 Orchts ustulata, 17 Ornithogallum umbellatum, 130, 214, 255, 256 Osmunda cinnamomea, 132, 136, 220, 254, 278 Oxalis, 7, 259, 260 lastandra, 137, 141 vtolacea, 141, 143 Palladine, W. (Eiweissgehalt der griinen und etiolirten Blatter, Ber. d. Deut. Bot. Ges.g: 191. 1894), 23, 300, 304 (Ergriinen und Wachstum der etiolir- ten Blatter. Ber. d. Deut. Bot. Ges. Git) 2295 1691) bre (Recherches sur la respiration des feuilles vertes et des feuilles étiolées. Rev. Gen. d. Bot. 5: 449. 1893), 2 316 Palladine (Transpiration als Ursache der Formanderung etiolirter Pflanzen. Ber. d. Deut. Bot. Ges. 8: 364. 1890), 23 Papaver, 271 somniferum, 10 Pastinaca sattva, 143,144, 243, 244,259,261, 286 Payer (Mem. sur la tendance des racines a fuir la lumiere, Compt. rend. d. 1. Acad. d. Sc. I: 1194. 1842), 5 Peas, etiolation of, 1 Peltandra Virgintca, 144-147, 215, 216, 220, 257, 259, 286, 296 Pericycle in etiolated stems, 251 Periderm, formation of on woody etio- lated stems, 249 Pertz, researches of, 305 Petiolate leaves, etiolation of, 257 Petunia, 245, 276 Pezizaceae, relation to light, 5 Pfeffer, on nature of etiolation (Pflanzen- physiologie. 2: 114. 1901), 284 Phaseolus, 26, 147-149, 224, 230, 246, 263, 265 multifiorus, 8, 9, 30, 226, 282 vulgare, 16 Phegopteris effusa, 34 Philotria Canadensts, 217, 218 Photo-epinasty, 14, 23 Photo-hyponasty, 14, 23 Phototonus, 18, 216 Phycomyces, 19, 31 Phyllocactus latifrons, 237 Phytolacca decandia, 149, 150, 243, 247, 249, 251, 263, 265, 267, 286 Pilobulus, 291 Pisum sativum, etiolation of, 7, 34 Pilobolus microsporus, 17, 30 Podophyllum peltatum, 150, 152, 220, 243, 244, 259, 261, 263, 265, 269 Poggioli, S. (Opuscules scientifiques de Bologne, I: 9), 4 Polygonum, 9 cuspidatum, stems, 248 Polystichum acrostichoides, 151-154, 220, 254, 278, 295, 297 Populus Simonit, 154-156, 239, 240, 241, 242, 246, 247, 249, 251, 268, 286, 295 Potentilla, 157, 26: reptans, 32 Potts, G. (Zur Physiologie des Dictyos- normal and_ etiolated telium mucoroides. Flora. 91 : 281-347. 1902), 279 Prantl, R. (Ueber den Einfluss des Lichtes auf das Wachstum der Blatter. Arb. a. d. Bot. Inst. Wiirzburg. 1 : 371. 1673'),'13, 282 Proserpinaca palustris, 217 Prunella grandiflora, 17 Pteris chrysocarpa, 9 longifolia, 157, 158, 220, 254, 278 Pulmonaria officinalis, 17 INDEX. Polygonum Fagopyrum, 227 Polypodium repens, 34 Quamasia (see Camassia), 214, 255, 306 Quercus, 115, 161-169, 189, 250, 251, 252 palustris, 158, 159, 230, 231, 239 rubra, 159-161, 230, 231, 239 Radish, 211 Rane, F. Wm. (Electro-horticulture with the incandescent lamp. Bull. No. 37. W. VirginiaExp. Station. 1894), 201, 293 on the effects of artificial illumination on plants, 275 Ranunculus Asiaticus, 205 divaricatus, 27, 217 Raphanus, 19 Rate and mode of growth as affected by light and darkness, 304-309 Rauwenhoff, on etiolated stems, 248, 283 (Sur les causes des formes anormales des plantes. Ann. Sc. Nat. VI. 5: 267. 1878), 18 Ray, J. (Historia plantarum. 1: 15. also in imprint of 1693), 1 Re, F. (Saggio di nosologia vegetabile. p- 23. 1807), 4 (Saggio teorico-pratico sulle malattie delle piante, p. 147, 1807), 4 Rennert, R. J. (Seeds and seedlings of Arisaema triphyllum and Arisaema Dra- contium. Bull. Torr. Club. 29: 37-54. 1902), 50, 221 Pheum, 167-169, 259, 260 Rhizomes, etiolation of, 216, 217 Rhododendron, 26 maximum, 210 Phus, 169, 239, 240, 241 Richards, H. M., observations of, 33 Picinus communis, 169, 170, 230, 231, 299 Ricome, M. H. (Action de la lumieére sur les plantes préablement étiolés. Rev, Gen. d. Bot. 14: 26,72, 120. 1902), 33, 297, 298, 299 (Sur le développement des plantes étiolées ayant reverdi 4 la lumieére. Compt. Rend. 131: 1251. 1900), 33 1686 ; | Robinia pseudacacia, 29 Roots, etiolation of, 233-235 Rowlee, W. W. (Effect of the electric light upon the tissue of leaves. Proc. 19th Annual Meet. of the Soc. for Promo- tion of Agric. Science. Boston, Mass. pp- 50-58. 2 pls. 1898), 210 Rumex, 168, 170, 171, 219, 260 Rzentkowsky, T. (Untersuchung iiber die Entwickelung des etiolirten Phaseolus multifiorus. Mitth. a. d. Univ. z. War- shau ; abstract in Bot. Jahresber. 4: 745. 1876), 16, 304 Sachs, investigations of, 39, 281, 282, 305 on etiolation, 275 INDEX. _ Sachs, on etiolation of seedlings, 245, 246 (Handbuch d. physiol. Bot. 1865; see Lotos. Jan. 1859), 7 (Gesammelte Abhandlungen ueber Pflanzenphysiologie. 1: 229, 261, 1892), 10 (Physiology of ‘plants. English ed., p- 531- 1887), 234 (Vorlesungen ueber Pflanzenphysiol- ogie. 1865), 10 (Text-book of Botany. 2ded., p. 835), #5 (Ueber den Einfluss des Lichtes auf die Bildung des Amylums in den Chlorophyllkérnern. Bot. Zeitung. 201: 265. §1 S02) 77 (Uebersicht der Ergebnisse der neu- eren Untersuchungen ueber das Chlorophyll. Flora. 45: 129. 1862), 7 (Ueber den Einfluss des Tageslichtes auf Neubildung und Entfaltung ver- “ schiedener Pflanzenorgane. Bot. Zeitung. 21: Beil., p.31. 1863), 7, 223, 262, 272 (Wirkung farbigen Lichts auf Pflan- zen. Bot. Zeitunge. 22:°3253; 361, 369. 1864), 10 (Ueber die Wirkung der ultravioletten Strahlen auf die Bliithenbildung. Arb. a. d. Bot. Inst. i. Wiirzburg. 33) 3722, TS07), 10, 272 (Ueber den Einfluss der Lufttempera- tur und des Tageslichts auf die stiindlichen und_ tiaglichen Aen- derungen des Langenwachstums (Streckung) der Internodien. Arb. - d. Bot. Inst. i. Wiirzburg. 1: 99. 372)), 10 Seis. 171, 269 argentea, 22 Sansevieria, 215 Gutneensis, 171, 173, 255 Saponaria officinalis, 30 Saprolegnia, 29 Sarracenia, 260, 262, 286 purpurea, 173, 176 vartolaris, 177, 179 Saururus, 249, 266, 267 cernuus, 178-180, 217, 243, 249, 263 Schmitz, J. (Beitrige zur Anatomie und Physiologie der Schwamme. Linnaea. 17: 475. 1843), 5 Schober, on trichomes, 247 (Ueber das Wachstum der Pflanzen- haare an etiolirten Blatt- und Ach- senorganen. Zeitschr. f. Naturw. IV. 58: 4: 556. abstract in Bot. Centralb. 28: 39. 1886), 22 Schubeler (The effects of uninterrupted sunlight on plants. Nature. 21: 311. 1880), 207, 300 Schulz, N. (Ueber die Einwirkung des Lichtes aut die Keimungsfahigkeit der Sporen der Moose, Farne, und Schach- 317 telhalme. Beih. Bot. Centralbl. 11: 81. 1901), 34 Schulzer von Muggenburg (Des alleleben- den Lichtes Einfluss aut; die Pilzwelt. Flora. 61: 119. 1878), 17 Scilla campanulata, 17 Scorzonera Hispanica, 9 Sedum dendroideum, 7 Seedlings, growth of in darkness, 230-235 Sempervivum assimile, 237 Haworthit, 7 Senebier (Hypothese pour expliquer l’eti- olement. Physiol.-vegetale. 4: 295- 308. 1800), 280 Senebier, researches of, 280 Senebier, J. (Observations sur les fleurs du quelques plantes élevées dans Vobscuritié. Mem. Physio-chim- iques. 2: 99. 1782), 270 (Mémoires physico-chimiques. 2: 51- 4162"',2782)5.2 (Physiologie végétale. 4: 264-308. 1800), 2 Siemens, C. W. (On the iffluence of electric light upon vegetation and on certain physical principles involved. Nature. 21: 456. 1880; see also Proc. Roy. Soc. 30: 210-230), 208 Sieve tissue in etiolated stems, 251 Silene pendula, 17 Sznapis album, etiolation of, 3 Skototonus, 216 Smilax, 222, 224, 229, 246, 247, 267, 268 Beyrichit, 199, 200, 263, 2 Smith, J. E. (An Introduction to syste- matic and physiological botany. pp. 206, 207. 1807), 4 Solanum, 8, 12, 25, 227 tuberosum, 22, 30, 180, 181, 243 Soja hispida, 22 Sparaxis, 180, 214, 255 Spinach (see Sfznacza oleracea), 209, 211 Stinacia oleracea (see spinach), 209 Strraea opulifolia, 16 Spirogyra, 13, 16 Sporangia, effect of etiolation on, 278 of fungi, relation to light, 279 Spores, effect of etiolation on, 278 Sporophores of fungi, relation to light, 279 Stachys lanata, 22 Stahl, E. (Ueber die Einfluss des Stan- dortes auf die Ausbildung der Laub- blatter. 1883), 22 Stameroff, K. (Zur Frage iiber den Ein- fluss des Lichtes auf das Wachstum der Pflanzen. Flora. 83: 135. 1897), 29 Stebler, F. G. (Untersuchungen iiber das Blattwachstum, Jahrb. f. wiss. Bot. Es) Aye, 1 O7ON.te Stele, effect of etiolation on, 252 Stewart, drawings by, 174-176 Stigeoclonium tenue, 32 Stimulative influence of light, 288 318 INDEX. Stomata, development of on etiolated | Veronica speciosa, 10 stems, 247 Victa Faba, 7, 9, 23, 263 Strehl, R. (Untersuchungen iiber das | Vines, S. H. (The Influence of Light Lingenwachstum der Wurzel und des hypokotylen Glied. 1874), 14, 234 Succulents, effects of darkness on, 235-238 Taraxacum, 181 Taylor, A, drawings by, 37 Temperature at which observations were carried on, 36 Teodoresco, investigations of, 290, 291, 293, 294 : Teodoresco, on effect of light and dark- b ness on Victa Faba, 263 Teodoresco, E. C. (Action indirecte de la lumiére sur la tige et les feuilles. Rev. Gen. d. Bot. 11: 369, 430. 1899) , 30 (Influence des différentes radiations lumineuses sur la form et la struc- ture des plantes. Ann. Sc. Nat. Bot. VIII. 10: 141-164. 1899), 30 Ternetz, C. (Protoplasmabewegungung Fruchtk6rperbildung bei Ascophanes ‘carneus Pers. Jahrb. f. wiss. Bot. 35: 2173. LOOO) resi Tessier (Expériences propres a _ deével- loper les effets de la lumiere sur certaines plantes. Mém. l’Acad. d. Sc. Paris. p. 133- 1783), 3 Thaspium trifoliatum, 94 Thomas, J. (Anatomie comparée et ex- périmentale des feuilles souterrainnes. Rev. Gen. d. Bot. 12": 394. 1900), 32 Tipularta, 215, 221, 268 untfolta, 181, 255, 256 Tomato, 211 Tragopon porrifolius, 8 Trillium, 220, 269 erectum, 182, 243, 244, 257, 259 erythrocarpum, 131, 243, 244, 257, 259 Tritelia (see Milla) unzflora, 182-184, 214, 255, 256, 269 Triticum, 8, 12 Tropaeolum, 8, 9, 271, 274 Majus, 227 Tulasne (Fungi hypogaei) p. 2. Tulipa, 8, 214, 255, 256 Gesneriana, 271 patens, 185 sylvestris, 185 1852, 5 Uhlitzsch, P. G. (Untersuchungen iiber das Wachstum der Blattstiele. 1857), 22 Ulothrix, 28 ‘Urtica dioica, 12 Urticula pilulifera, 22 Vagnera stellata, 185, 186, 243, 263, 264, | 267 Vaucheria sessilis, 16 Van Swinden (Account of Mees’ observa- tions. Journal de Physique. 6: 445. 1776. and 7: 112), 193, 2 | | upon the Growth of Leaves. Arb.a. d. Bot. Inst. i. Wiirzburg. 2: 114. 1878), 19 (The Influence of Light upon the Growth of Unicellular Organs. Arb. a. d. Bot. Inst. i. Wiirzburg. 2: 133. 1878), 19 (On Epinasty and Hyponasty. Annals of Botany. 3: 415. 1889), 23 On Growth of Leaves in Darkness, 268 Vines, researches of, 305 Viola obliqua, 186, 187, 260, 269 rostrata, 187, 188, 243, 244, 249, 263 Vochting, H. (Organbildung im Pflan- zenreich. 2:66. 1884), 22 (Ueber der Knollenbildung. Bibl. Botan. 1>-Hiit. 4. 1887), 22° (Ueber die Abhangigkeit des Laub- blattes von seiner Assimilations- thatigkeit. Bot. Zeitung, 49: 113. 1891), 22, 274 (Ueber den Einfluss des Lichtes auf die Gestaltung und Anlage der Bliithen. Jahrb. f. wiss. Bot. 25: 149, 1893), 22, 273 (Ueber die Bedeutung des Lichtes fiir die Gestaltung blattformiger Cac- teen. Zur Theorie der Blattsteil- ungen, Jahrb. f. wiss. Bot. 26: 438. 1894), 22, 238 (Zur Physiologie der Knollenge wiichse. Jahrb. f. wiss. Bot. 34: 1. 1900), 22 Vogel, A. (Beitrage zur Kenntniss der Verhaltnisses zwischen Licht und Vege- tation. Flora. 39: 385. 1856), 6 Vogt, C. (Ueber Abhangigkeit des Laub- blattes von seiner Assimilationsthatig- keit. Inaug. Diss., Erlangen. 1898), 30 Von Wolkotf, Measurements of etiolated plants, 115 Walz, J. W. (Ueber die Wirkung des Lichtes auf einige Processe des Pflan- zenlebens. Schrift. d.k. Neuruss. Univ. i. Odessa, 17: —, 1875; abstract in Bot. Jahresber. 3: 786. 1875), 15 Ward, H. M. (The Action of Light on Bacteria. Proc. Roy. Soc. 185: 961. 1895), 27 Water-etiolations, 216 Weiss, A. (Untersuchungen ueber die Zahlen und Gréssenverhiltnisse der Spalt6ffnungen. Jahrb. f. wiss. Bot. 4: 125. 1865-1866), 13 Wiesner, J. (Vorlaufige Mittheilung tiber den Einfluss des Lichtes auf Entste- hung und Zerestérung des Chloro- phylls. Bot. Zeitung, 32: 116. 1874), 15 INDEX. Wiesner (Die heliotropischen Erschein- ungen im Pflanzenreiche. II: 7. 1880), 20 (Formanderungen von Pflanzen bei Cultur im absolut feuchten Riume. undim Dunkeln. Ber. d. Deut. Bot. Ges. 9: 46. 1891), 33, 238 (Photometrischen Untersuchungen auf Pflanzenphysiologischen Ge- biete. Sitzungsber. d.Kaiserl. Akad. GaWwiss-l.) Vein); 102); “Abth.) 1. 1893), 25 (Untersuchungen ueber den Licht- genuss der Pflanzen in Arktischen 319 Gebiete. A. d. Sitzungsber. d. kaiserl. Akad. d. Wiss. i. Wien. tog: Abth. 1. May, 1900), 208 Woodwardta radicans, 188, 220, 254, 278 Woody perennials, etiolation of, 239-243 Xerophytes, etiolation of, 238 Zed, 230, 221, 267 Mays, 8, 12 Ziegebein, E. (Untersuchungen iiber den Athmung keimende Kartoffelknollen sowie anderer Pflanzen. Jahrb. f. wiss. Bot..25: 563. 1803) 25 Tpit» 4 ; a it eee iT 1 a y : A \ ay, ¢ ‘ ‘ / ¢ i hPa ty ; : an f ener Vt ili pil 17) SU i f ¢ Net gat al ee Sk “ye yo r ar. sags Hate <