'^A- ^A M /.'•■ .■^^K ■' '-irpfi- \ ,'- H -''^'T-.-^, ^^-^■ ■ { '^"^W >:Ct|^ . ^'■'kt'-'^^?';;: THE PLANT WORLD An JIlluBtralrb ilnntl|lg MasajUt* uf (Snirral Intatiij Edited by FORREST SHREVE .« / Published by THE PLANT WORLD ASSOCIATION Volume 14 Tucson, Arizona 1911 The Plant World Association IS COMPOSBD OF THB FOLLOWING MBMBSKS: Jocsrn Cmari rs Aktmur, l*iir<|iir I'nivrrsity Otis Wii.uiAw Cai.phki.i. L'nrv io»»- .if ChicaKO. WlkMAM Ar¥Tl>: CANXirtN. |tr-rrt l.tttxjfHlnrv. hrimklvn Institute. BDBTON Ki'U AKP I.IVINUSTOM. |.ihn« llnpL>ii!> University. Francis Krnksi j i.<»v»». A:hS:iiiih I'oivtrohnic Institute. Damibl Thkumlv .MAcDoncAL. Cumc^ie Institution ii( Wachinirton. lOHN JaMRS TlinilNBIIR, University of Arizona William Kknnktt MoCallum, C'<>iitii!rni»l Mmcan Rubber Co JAMRS BliKTKAM OVKKTOM. I'niverMiy «if Wisconsin. GboIIRII Iamk.s I'Klxi k SiHiitord L'fuvcrsity. ClIARLRK I.UIT|» l'<)LLAKI>. StHlrri Nl.ind A«sitri4tion HRRBRRI MauLR Kii'HAKItS CoMiiiibiu Univer>ity. F'orrkst Sukkvk. Hrvrn f.atviratory, VOLNBT MORRAN SHAIIUNO. Loma Linda, California. INDEX TO VOLUME FOURTEEN Arthur, J. C. — Some Alaskan and Yukon Rusts 233 Barker, Eugene E. — Notes on the Royal Moccasin Flower 190 Berry, Edward W. — Notes on the Ancestry of the Bald Cypress . . 39 Bessey, Ernst A. — The Hammocks and Everglades of Southern .... Florida 268 Blumer, J. C. — Change ci Aspect with Altitude 236 Books and Current Literature .. 23, 45, 69, 99, 123, 146, 177, 195, 227, 248, 277, 299. Campbell, Douglas Houghton — A Sketch of the History of Plant .Morphology in America 105 Clark, Charles F. — Observations on the Blooming of Timothy 131 Foster, A. S. — Some Botanical Observations in the Mountains of- Washington 222 Free, E. E.— Studies in Soil Physics, I 29 Studies in Soil Physics, II 59 Studies in Soil Physics, III HO Studies in Soil Physics, IV 164 Studies in Soil Physics, V 186 Hus, Henri. — Frondescence and Fascialion 181 Hus, Henri and Murdock, A. W. — Inheritance of Fasciation in Zea Mays 88 Lewis, Isaac M. — The Seedling of Quercus \ irciniana 119 Livingston, Burton Ed -ward — .\ Study (f the Relation Between Summer Evaporation Intensity and Centers i f Plant Distribution in the United States 205 A Radio-Atmometer fjr Comparing Light Intentities 96 Paper Atm'ptian or Smyrna wheat. But in the latter the branched character never is lost entirely, though it may be greatly reduced under unfavorable conditions. It is well known that fasciations have a tendency to split, especially when the crest assumes great proportions, /. e., when Fig. I. Fasciated Ears of Zea Mays everla XJ. the cross section becomes a mere fraction of the width. In a paper shortlv to be published, the senior author hopes to bring out the purely mechanical basis for such splitting. For the present purpose it is sufficient to point out that if a splitting mav occur during the later stages of development it is not at all improbable that instances may occur in which the same necess- arv conditions obtain during a younger stage. In Delphinium hyhridum fasciatum splitting of the inflorescence occurs not un- *Blaringhern, L. Heridite d'anonialies flolales presentees par le Zea Mays tunicata. Compt Rend. hebd. Soc. Biol., 57:^578, 1904. fGallardo, A. Xotas fitoteratologicas. Ccm. mvs. iia<.. Bueitos Aires, 1: 116, 1899. de Vries, H. Plant-Breeding, fig. 33. 94 The Plant World. frequently. Thus one of the flowerstalks of a plant showing fasciation in six of its nine flowerstalks, was split eighteen inches from the top, the divisions bearing respectively nineteen and twenty-three flowers. As a rule the splitting occurs verv much nearer the top. Of fourteen split inflorescences, ten were split within two inches from the top, one at five, one at eight, one at eleven, and one at eighteen inches from the top. This would militate against the assumption that the branching of the female inflorescence in corn was in any way related to fasciation. Nor do all compound ears show fasciation, though in our exper- ience they did in the majority of instances, as shown in the fol- lowing table. TABLE II, SHOWING THE RELATION BETWEEN FASCIATION AND COMPOUND EARS IN ZEA MAYS EVERTA. 11310 11510 Total Compound ears totally fasciated .5 13 18 Compound ears partially fasciated 1 9 10 Compound ears not fasciated 0 15 15 Total number of comnound ears . . . 6 37 43 Number of ears of all kinds 41 96 137 At the same time the fact that compound ears were also present in No. 11410 (non-fasciated stock) to the extent of 16% need not necessarily invalidate a contention that fasciation and branching are to be looked upon as due to an identical cause, for among the ancestors of these plants may well have been a fasciated ear, something rendered more probable by the fact that one of the components of one compound ear showed flatten- ing (table 1). Further, in the case of the ears under No. 11310, there was not a single compound ear which did not show some fasciation, which would indicate a close correlation between branching of the inflorescence and fasciation. This correlation is not so marked in the case of the ears under No. 11510. But even here 59% of the compound ears showed fasciation while of the single ears under this number only 46% were fasciated. In connection with this the question might be raised whethere th pressure exerted upon compound ears might have a tendency to either cause fasciation or to bring about its Inheritance of Fasciation in Zea, .95 simulation. The experiRents of Lopriore * and others show the former to be highly improbable, though Sorauerf notes fasciation in a stem of Tecoma radicans due to appression to a wall and of which the part reaching above the wall likewise showed fasciation. In view of other ex])eriments carried on by us it seems unlikely that the pressure exerted would cause a malformation similar in appearance to a fasciation. The relation between simple and compound ears is well shown in the following table : table III, showing REL.A.TION BETWEEN SIMPLE AND COMPOUND EARS IN ZEA MAYS EVERTA. Simple ears Compound ears Summation « •0 o en VI s "u 4-1 0 n W 1 T3 Non- fasciated T3 '3 X. #% 6 15 22 23 28 20 , a c'3 0 VI •s 'o •0 V ■M Co Total ears # 22 27 49 % 54 28 36 # 12 31 43 % 29 32 31 # 0 15 15 % 0 16 11 28 % 68 12 % 29 # % 1 1310 Red fasciated .... 41 100 1 1510 White fasciated. . 49 77 51 56 46 58 48 1 96 100 Total fasciated . . . 42 2 137 100 114 10 White non-fasc... . 0 0 26 84 1 3 4 13 1 3 30 97 0 31 100 ♦Decayed. This table sufficiently analyzes the results obtained to ob- viate the necessity of a detailed description. It does not, however, bring out the degree of fasciation shown by the various ears. In the majority of cases the fasciation was not as pronounced as that of the parents, though in several instances a bifurcation of the ear could be noted, in one case the two tips being almost three inches apart. In other words, the average of the offspring shows the abnormality to a lesser degree than do the parents, though among the descendants may be some which equal or even surjDass them. The table shows that e\en when the non-fasciated compound ears are left out of consideration, the conclusion is reached that fasciation may be inherited bv a large percentage of the offsj^ring, in one case 75^^^ > ^"d in another almost that proportion, of the plants bearing fasciated ears. If ♦I.opriore. G. I caratteri analoinici delle radici nablriforiiii.. 1902. fSorauer, P. Handbuch der I'flanzenkrankheiten, 1: 334, 1906. 96 The Plant World. the compound ears are to be considered as fa'sciated this number would be considerably increased. So high a percentage is not obtained when fasciation is considered by ear, showing that the fasciation does not always extend to every ear of the plant. At the same time a comparison of the results obtained from No. 11410, a non-fasciated ear, and those from No. 11310 and No. 11510, both fasciated ears, show that fasciation is not a matter of mere accident but one of inheritance and subject to the same laws as are other characters. University of Michigan. A RADIO- ATMOMETER FOR COMPARING LIGHT INTENSlTlEvS. Burton Edward Livingston In attempting to measure and compare the external con- ditions which influence the behavior of plants there has been brought out a striking relation between the plant population of certain habitats and the evaporating power of the air, the latter being measured and automatically summed by the porous cup atmometer. * But the rate of water loss from plants is usually more affected by sunshine than is the corresponding rate from the porous cup, so that the instrument, as heretofore arranged, fails to give a true measure of all the factors that tend to remove water from the aerial parts. The same is true of the rate of evaporation from the soil surface, which is usually greatly in- creased by sunshine. The foliage of ordinary plants, as well as the soil surface, absorb a considerable amount of radiant energy, thereby tend- ing to rise in temperature, and if water be present in the substance of these surfaces (as it always is in living leaves, etc.) a goodly portion of the absorbed energy becomes latent in transforming the liquid water to its vapor. Thus the rate of water loss is ♦The literature of the instrument and its '^se is given to date in Plant World 13; ) 12-118. 1910. Later has appeared: Brown, W. H., Evaporation and Plant Habitats in Jam- aica. Plant World. 13: 268-72. 1910. A Radio-Atmometer. 97 increased by the energy absorbed. The white porous clay cup absorbs comparatively little radiation and is thus not af- fected as profoundly as are the plants and the soil. It seemed desirable, therefore, that an intsrument be devised that should absorb as much as possible of the radiant energy of sunshine and should integrate the effects of this absorbed energy in a man- ner as satisfactory as that in which the porous cup atmometer sums the effects of the evaporating power of the air. An attempt in this direction, lasting over several years, has met with some degree of success, and it is to lay the resulting instrument before physiologists, agriculturists, and ecologists that this paper appears. '•' The radio-atmometer is merely the common form of porous clay atmometer with the clay surface so modified that it absorbs a considerable amount of the radiant energy falling upon it. Two forms of cup are available, one made of colored clay, the other coated with lamp-black. The former possesses a dark brown color and has the advantage of retaining its color in spite of rain, the latter is dead black. These cups are set up in the ordinary manner, excepting that the position of the cups with reference to the direction of the incident light and heat must be such that the angle of incidence will not vary throughout the period of observation. If this angle be allowed to change there will be introduced errors in the form of apparent varia- tions in the light intensity and the correction for such errors would be laborious and uncertain. The difficulty is readily avoided if we simply so place the cylindrical cup that the sun- shine falls upon it perpendicularly to its long axis at all times of the day, the source of radiation thus virtually rotating about the cylinder in a plane perpendicular to its long axis. The position of the cup thus depends upon the latitude and season. It may pe placed empirically at noon by seeing that it receives the sun's rays perpendicularly, and at the same time that its axis lies in the same vertical plane as the sun. For the northern hemisphere its tip will point more or less to the northward of the zenith. It will need to be readjusted every few da vs. Of ♦This instrument and its readings are compared to the plant and its rates of water loss, under varied conditions of solar radiation, in an article about to appear in the Botanical Gazette. Other instruments also are there considered. 98 Thh Plant World. course the angle at which the instrument is to be placed may be determined beforehand by reference to the almanac. It has been found convenient to mount the cups on a flexible tube of lead or copper, though a rubber section inserted between two glass tubes is as satisfactory, providing a proper support for the cup be arranged. To blacken the cups, ordinary lamp-black is clarified by boiling in distilled water, cooling and decanting, and repeating the process several times. The carbon paste thus obtained may be diluted with distilled water and applied to the cup (after the latter is filled and placed in operation) by means of a small brush. A little practice renders the operation easy. The blackened cup often, though not always, shows a somewhat greater sensitiveness to sunlight than the brown one. Whether this depends upon the quality of the light or on some other factor has not been investigated as yet. To have the re- sults comparable, the same form of cup must of course be used throughout any series of observations. The dark cups function as does the white one, to integrate the efifects of the evaporating power of the air, and they add to these the efi"ects of their more complete absorption of radiant energv. A dark cup in darkness or very weak light operates just as does a white one, while in strong light, especially in full sunshine, the difi"erence between the readings is very marked. Since the radio-atmometer, as so far constructed, sums the effects of absorbed radiant energy only in so far as these effects are in the direction of heating the surface of the instrument (that is, only in a photo-thermal way), the readings obtained therewith bear no necessarily direct relation to the light condi- tions as these determine the photosynthetic process of plants, which is photo-chemical in its nature. According to the re- searches of Blackman and Matthaei, * however, we may con- sider that temperature is more important for photosynthesis than is light intensity, providing of course that there is a con- siderable amount of light, and our instrument takes account of temperature as this would influence plant leaves. At any rate, we are able to compare the varying intensities of sunlight for ♦Blackman, F. F. and Matthaei, G. L. C, Phil. Trans. Roy. Soc. I,onci. Ser. B, Vol. 197. 1904 Books and Cvrrent Literature. 99 diflferent times, places, etc. with reference to their influence on transpiration. It need hardly be added that the radio- atmometer fails to take account of such secondary eff"ects of light as stomatal movements, wilting and the like, which must be studied by different means. The instrument here described is, then, a physical apparatus which embodies some of the properties of plant foliage, being affected in much the same manner as are plants by the two aerial factors, evaporating power of the air and intensity of radiation. Inasmuch as it adds photo-thermal effects to those of the evaporating power of the air, the new instrument is to be regarded as a better one for the study of these alterations in rate of transpiration which have been supposed to be due to purjioseful "regulation," than is the ordinary white atmo- meter. Of course the water loss from different i)lant forms, and even from different individuals, is not affected to the same degree by conditions of the surroundings, and we need not ex- pect to find the sunshine influence to be the same on all plants as it is on the dark cup. Some plants exhibit a greater sensi- tiveness to variations in solar intensity than do the cups, others are less sensitive and others approximatelyequal one or the other form of cup in their sensitiveness. We have here not only a means for comparing radiation intensities at different times and places, but also a method by which it should be comparatively easv to study the relative sensitiveness of different plant forms to the same variations in illumination. Such comparisons may furnish a much-needed ballast of quantitative data to the dis- cussion of xerophily and the like. The Johns Hopkins University. BOOKS AND CURRENT LITERATURE. A California Sylva. — It is only a year ago that Jepson gave us his "Trees of California," a manual adapted to popular use, and he now crowns his studies in forestry with a noble quarto * worthy of a place on the shelf by the side of vSargenfs great Sylva. The excellent mechanical execution of the volume is a credit to the Press of the University of California, and the vast stores of information it contains are not only of the highest ♦Jepson. Willi'; T.inn. Tlic Silva of California. Mem. Tniv. Cal. Vol 24to. pp 480. pis. 85, maps 3. text figs 10. Berkeley, The University Press. (SlO.OOy. 100 The Plant World. scientific value, but are presented in a style so interesting and so perspicuous as to make it a most readable book. The plates are in part reproductions of photographs, mostly taken by the author, and include a series illustrating the effects of wind in modifying tree forms, which is of unusual interest. Other plates are from drawings of uniform excellence. Two maps show the locations respectively of the northern and the southern groves of Big Trees, while the third, of the whole state, is designed with reference to the physical features which are of importance in influencing plant distribution. The author defines the leading object of this memoir to be the presentation of what is now known concerning the taxonomy and the distribution, both geographical and ecological, of the trees of the state. In addition, he discusses the biology, the habits, the uses and the history of all but the less important species. The systematic part of the work is preceded by chapters on the physiographical distribution and the dendrological characteristics of the California trees. He divides the state into five forest provinces: The Sacramento and San Joaquin valleys, the South Coast Ranges, the North Coast Ranges, (the last two divided by San Francisco Bay), the Sierra Nevada, and South- ern California. The forest features of each of these provinces are fully described, and referred to the physical conformations and other causes to which they are due. Their relation to Merriam's life zones is also considered, and a "census table" is given show- ing the distribution of each species in the five forest provinces. In this connection it is interesting to note that the Southern California province, a region less adapted than any of the others to forest growth, is credited with 57 species, out of a total for the state of 92, only two less than occur in the North Coast province, which has naturally the largest number of all; and that all of the five leguminous trees of the state are restricted to the deserts. The "typically Californian" species are 49 in number, and 18 are strictly peculiar to the state. Only two trees, the Aspen and the Black Willow, are common to California and to the eastern states. Under the head of Arboreal Characteristics the author treats of leaf variation, regeneration and seed production, wind influences, nanism and other topics. A table is given showing Books and Cikkhxt Litdratikh. 101 the ages attained b\- the mure important trees, and another giving the diameters aaid ages of sixteen Big Trees. An exami- nation of this table proves that size and age are not coordinate, for the largest tree, which had a diameter of 24 feet, 2 inches, was only 1,346. y.ears old',. TvhiJc' the oldest, with 2,17? annxiafrings, was only IS-feet, 4 inches' in diameter-. ' Much^reater ages'lrave been ascirbed to the Big Trees, but Jepson is of the opinion that iHone ar€ more than 2,500 years oldr ■ ■ '» ; The systematic part of the Sylva^occupies 220 pages. The descriptions are conscise and- clear, and 'good keys are siijjplied for the guidance of -'thetstu'de'nf. A>^'fuH s)*^nonomy is not at- tempted, buteach species is siipplied with references to the irrore pertinent literature^" The^xtensive field studies of the author -have, served him (well in giving accuracy to th'e delinritation of ranges, and in supplying a fund of varied information; It is •with no little satisfaction that we record this latest evidence of the activity of the. botantiss of the University' -of California, who have contributed so ably in recertt years to the elucidation of the flora of California. — S. B. Parisw; Atlantic PnyTOPt^it'NtLor^.'^tiiWe ieports * on i)lankton material collected from the Giilf Stream," the Canary 'Current, the North Equatorial Current^ the Guinea Cvirrent, the South Equatorial Current, and the Sargafsso §^a',''i'n all of which records w^re made of tecahty,-tinie, terilperatity'e of air aild'wafei;, depth and character 'of eolT^tidn:. ' At-the latitude of Brest, diktoins werie the chief component, arid ffotlithente^to the' Azores ocean 'plankton, chiefly ' Cerdiinrn, preponderated, "tii the 'Canary Curretrt tor' tHeCap^'VeMe Islands a Variety of 'form's' prevailed lil 'which 'diatoins were; again proriiiriyrtt. '' ih the North Eqiia- •torial stream" TrichoSes7itiufn''^v:a's the chief 'forrri,"but with it •Peridineafe bcciirred.'"- M-'tfte''G"uiirea' Curr^flt the flora was meager. Trichodesmium pr^p6hdferated in th'fe'Soutli Eqiiatoirial "Currefrt^, ahd'iri the-Bargossa vSea,'Cemimwtt ' 'As regards Vertical distribution, diatoms, and to -^dirie extent Pfefidirieae, occur Ut the surface when the water'^is ddld "vi'htrtit iS' wanner the' latter are tnbre riunierou:^] ' buf'they fill behind in warrh regions n— : -i . .r, t\ vc .t-.: ■ I ' ) ♦Stuwe, W., Phytoplankton aus 4pm Noid-Atlantik. Engler's Bot. Jahrb. XLIII, heft 4 22S'3«2r 4uh mar>9; ' i9W?^Y JtlK lu 5.riu:^jiJ( 102 The Plant World. where Trichodesmwm prevails. Quantitatively the Canary Islands and the North Equatorial Current surpass the Sargasso Sea and the branches of the Gulf Stream. — V. M. Spalding. Distribution of Hieracium. — Samuellson has recently discussed * the forms of the Acroleucum group of the genus Hier- acium, five in number, which occur in southeast Norway and Sweden. The several forms occupy areas not distinctly separate, and the group can not be broken up into smaller groups of re- lated forms. Intermediate varieties do not occur even w^hen two forms grow close together in the some habitat, and each form exhibits a manifest "center of distribution" where it is most numerously represented. The recent development of the form is, according to the author the most important cause of the facts of distribution recorded. Their areas of distribution are not climatic areas. There are, however, various other forms of Hieracium the areas of which are determined by climatic factor?. It appears probable that most species of Hieracium have arisen by mutation. — -V. M. Spalding. NOTES AND COMMENT. The first number of volume I of Phytopathology, the official organ of the American Phytopathological Society, has been received. It is published bi-monthly for the society at Ithaca, New York, under the joint editorship of L. R. Jones, C. L. Shear, and H. H. Whetzel, with a list of associate editors whose names are well known in the annals of plant pathology as it has devel- oped in America. It is well illustrated with half-tone plates and zinc etchings, the press v/ork is excellent, and the list of con- tributors a sufficient guaranty of the high character, both scientific and literary, of the new journal. The subscription price is $3.00 per year, subscriptions to be sent to Donald Reddick, Business Manager, Ithaca, N. Y. Among the several papers which appear in this first issue is one on "Crown Gall of Plants," by Erwin F. Smith. The results recorded are the outcome of six years' work in the Bureau of Plant Industrv on the part of the writer, with whom we are associated Dr. C. O. Towhsend, Miss Nellie A. Brown, and Miss Alice E. Haskins. The disease is conclusively shown to be due ♦Samuclsson G., Uber die VerbreitunK einiger endemischer Pflanzen. Arkiv fur Botaiiik IX. 12-28. 7 figs. 1910. NuTES AND COMMKNT. 10.^ to bacteria, "not to fungi, not to uiyxoymcetes, not to mites, not to frosts, not to disturbances in nutrition." Artificial cross innoculation has been successfully performed on a great \ariety of plants belonging to such widely separated families as Com- positae and vSalicaceae. The hope expressed by the writer " that in these plant tumors, now so easily producable b\- a definite microorganism, we possess means of determining the cause of cell division and possibly of shedding some light on the origin ai certain malignant animals tumor," is one that will be shared by all who grasp the far-reaching importance of such an outcome. Correlation of the results and generalizations in two con- tiguous sciences is a matter of great importance. When accom- plished in the proper manner, it greatly broadens the usefulness of knowledge in both lines. When a scientist seeks to project the principles of his ow n specialty into a related branch, however, many pitfalls await him. He is more than likel> to accept the fading generalizations and hackneyed statements of the sister science as the measure of its progress. This is well exemplified in the address, "A Universal Law," given by Professor Bancroft before the American Chemical Society at Minneapolis recently {Science, Vol. 33, p. 179 Professor Bancroft says: "The view of the biologists seems to be that each generation always varies spontaneouslv from the preceding one to a greater or lesser extent, and that these varia- tions are reproduced more or less completely in the succeeding generation. By the survival of the fittest we eventually get a race which is better adapted to the local conditions than the one from which Ave started.*' This version of unmodified natural selection as first formu- lated by Darwin does not represent the prevailing views of the subject among botanists and is not held by any modern worker — certainly not by any experimentalist. In the next paragraph, Professor Bancroft, as the result of the adduction of principles formulated in chemistry, says: "The view that I have outlined is that the external conditions tend to produce such changes in the organism that the next generation varies in such a way as to be more adapted to local conditions. Bv the survival of the fittest and bv the continued 104 The Pi.amt World. action of the external conditions, we eventually get a race which is better adapted to the local conditions than the one from which we started." This statement embodies the baldest lyamarckianism, which has absolutely nothing to support it in the way of actual exper- ience. Furthermore, a brief acquaintance wdth the activities of workers in evolutionary science, particularly among botanists, would show Professor Bancroft that the problems of the relation of qualities of organisms and external conditions occupy the foremost place in the amount of attention received at the present time — ^with some definite results available. Professor Bancroft's reckless scissoring from various publi- cations, with no attempt to weigh their relative value, does not strengthen the treatment given the subject. Chemistry does not aid natural historv by the criticism of outworn generaliza« tions and discarded results of biological science. In all the numbers of Torreya for 1910, possibly the most valuable series of articles are those by Professor W. F. Ganong on "Botanical Education in America." which is none the less helpful because of the previous presentation of its essentials elsewhere. One can not help being glad that the author has given himself so unreservedly to the great work of botanical education, and that his thought has been presented with such clearness, force and consistency. Those who are engaged in teaching bot- any— and upon them depends in a large measure the fature of American botany — will hardly be able to find, in our own or in foreign literature, any more perfect examples of scientific exactness combined with a true philosophical spirit than are found in the pedagogical writings of Professor Ganong. The American Fern Journal for January, 1911, (Volume 1, No. 3) has been received and gives promise of filling a useful place in botanical hterature. Subscriptions ($1.00) including membership in the American Fern Society for one year, should be sent to Mr. H. G. Rugg, Hanover, N. H. Volume 14 Number S The Plant World A Magazine ok General Botany MAY, 1911 A vSKETCH OF THK HLSTORY ()I< PLANT .MOR I'lK )L()GV IX AMKRICA. Douglas Hoi'Ghtox C.\.mi*i!i;m,. The history of botany in the United vStates previous to the middle seventies of the last century was almost exchisively a histor\- of taxonomy of the vascnlar plants. It is trne that in some of the text-books a certain amoimt of morphological work was inclnded, bnt this was of a \ery general character. The j)revailing ideas of morphology, especially those dealing with the homologies of the floral ])arts, were c|nite uninfluenced bv the discoveries of the Ivuropean morphologists whose work has since made a revolutitm in the fundamental princijiles of mor])liologv. Prior to 1870 we may say that practically no serious morjihological work had been done 1yv American bot- anists. That the work of tliis earlier j^eriod should be mainlv tax- ononiic is not to be wondered at since the rich and interesting flora of the I'nited States offered a most tempting field to the systematist, and, moreo\er, none of our botanists had })een trained in the Ivuropean laboratories, whence there had just begun to j)enetrate to the outer world the results of the labors of the brilliant workers in morphology and jihysiology who, in German V especiallv, made the middle decades of the nineteenth centur\- the most notable period in the whole history of the science. Probablv the name of Hofmeister will stand first in the distinguished line of morphologists who, contemiiorary with 106 The Plant World, Darwin, but working quite independently, effected a veritable revolution in the botanical world. Ilofmeister's principal work, his studies on the comparative morpliologv of the Archegoni- ates and Gymnospernis, which practically broke down the old barriers separating "Cryptogams " and "Phanerogams," was translated into English in 1862, and thus made accessible to students in England and America. This work, im])ortant as it was, seems to have had little immediate influence upon the trend of botanical work either in England or America. Perhaps even more influential, especiallv as a teacher, was the great Sachs, whose famous text-book forms an epoch in the history of botany, and probably did more than any other single volume to advance the teaching of the science ,not only in Ger- man}-, but in England and America as well. In the vSachs' text- book there was presented for the first time an adequate treat- ment of the vegetable kingdom in its entirety, and although some of his conclusions as to the relationships of certain groups of plants are no longer held, his classification was an immense advance upon any that had preceded it, and was a fairly success- ful attempt, at least, to indicate the genetic relationships exist- ing between the different main divisions of plants. The history of morphological botany in America ma\- be said to date from about the middle seventies. At that time a number of young botanists returned from Germany to America and inaugurated courses in cryptogamic botany and morphology which gave a great impetus to the study of what may be called the biological side of botany as distinct from the purely taxo- nomic aspect of the science. The establishment of a department of cryptogamic botany at Harvard was an event of no small importance, and the long series of important contributions to the morphology of the lower cryptogams which has ever since emanated from the crypto- gamic laboratory of Harvard University bears witness to the high standards maintained at our oldest and most important school of botany. About the same time that the department of cryptogamic botany was organized at Harvard, Professor Harrington of the University of ^Michigan, offered a course in botany which was largeh of a morphological nature and was the beginning of the large and well organized department of Plant Morphology in America. 107 botany developed by his successors. In those early days there were very few professorships of botany, and much credit is due the pioneers who, with inadequate facihties and small pay, did so much to lay the foundations of the well-eciuipped departments of botanv which now form a part of every university of any pretensions. When about 1880, an enthusiastic group of young English botanists, all of whom afterwards became distinguished, studied in Germany under Sachs and De Bary, and, on returning to lingland, put into admirable English dress the famous text- books of those German masters, they did a piece of work which was far-reaching in its effects. Shortly after the ap])earance of the translation of the great Sachs' text-book Professor Bessey offered to the American student his excellent text, largely based upon this, and there a])peared soon after a number of other books some of which were strictly laboratory manuals. All of these text-books strongly emphasized the morphological aspect of tlie subject, and everywhere the students were hard at work tracing life histories and studying comparative morphology. The results of this activity were soon evident in an ever increasing number of publications of a morphological character. .Moreover, during the ten years from 1885 to 1895, a large number of American students went to Germany for study, where many of them came under the influence of the great morphologist, Strasburger, who probably was the most potent factor in directing the work of the morphological students at that period. This was especially seen in the great number of cytological papers produced in his laboratory, or as a result of his writings. Among the most active American workers in this field may be mentioned Atkinson, Chamberlain, Davis, Harper, I.awson, Mottier, Schaffner and Shaw. It was during this period that the interest in cytological problems was probably at its height. This was due in part to the introduction among botanists of the more exact methods of fixing and staining, in which the zoologists had been rather ahead of the botanists. It was during this period also, that the microtome came into general use as an adjunct to botanical research. The use of the microtome, making possible accurate series of sections, marked a great advance in the study of plant 108 The Plant World. morphologw This was especially the case in etnbryological in\es'tigations, where free-hand sectioning had been practically universal among botanists up to about 18S.T. The adoption of the microtome in the botanical laboratories of America soon resulted in the solution of many very difficult i)roblems, such as the develo])ment of the juothallium of the heterosporous Pteridophytes and the minute details in the historv of the embryo-sac and embryo of the seed-plants. The study of the gametopliAte in the seed-plants has been a favorite theme with American Ijotanists. In this province the influence of the strong botanical department of the University of Chicago has been very great. The long series of papers on both Gymnosperms and Angiosperms, written b\" members of the staff or by students working in the Hull Botanical Labora- tory, and many other j^apers prepared b}- students trained in Chicago, make one of the most important contributions to mor- phology that this countrv has prf)duced. First in importance of the work of the Chicago botanists has been the series of investigations upon the Gvmnosperms, especially the papers dealing witli the Cvcads. The striking discovery of spermatozoids in Cycas and Ginkgo by the Japanese l)otanists, Ikeno, and Hirase and those of Zamia, discovered by Webber in America, aroused renewed interest in the develop- ment of the Gymnosperms, and this was especially the case in Chicago where the results of many vears of special investiga- tions were finally embodied in the admirable treatise on the G)^mnosperms recently jniblished by Professors Coulter and ChamV)erlain. Other inxestigators who have interested them- selves in the morphological stud}- of the Gymnosperms are Coker, Miss Ferguson, Jeffrey, Pawson, Penhallow, vShaw, and Webber. The number of investigations on the development of the Angiosperms, especially those dealing with the structtires of the embryo-sac, has been very large. Particular interest has been shown in the ([ucstion of the homologies of the embryo- sac structures, and a search for forms which connect the pre- vailing type with more ])rimitive ones. Of the manv contribu- tors to this important subject, the following investigators may Plant Morphology in America. 109 be referred to: Atkinson, Coulter, Campbell, Caiiiinu, Johnson, Mottier, and Schaffner. A phase of inorpholoj^fy that has been niDre diligentl\- pur- sued in l{ngland than in America, due largely to its bearing on the study of fossil plants, is the vascular anatomv of the higher plants, especially' that of the Gymnosperms and Pteridophytes. The best known exponent of this ])hase of morjjliology in Amer- ica is Professor Iv. C jefTrey. The morphology of the archegoniate j^lants, the mosses and ferns, has received its share of attention in America during the past twenty-live years. Among those who have been active in this department mav be mentioned Atkinson, Barnes, Campbell, Ivvans, Howe, Jeffrey, Johnson, l.von, and Underwood. The morphological work upon Alg^e has been less extensive l^erhaj^s than that upon the higher cryptogams and seed-plants, but a good many \ aluable contributions have been made by American botanists to the morphology of this group. vSome of those who have made important additions to oar knowledge of the morphology of these plants are Farlow, Davis, Howe, Kofoid, ^loore, Osterhout, Saunders, and Setchell. The Fungi, comprising as they do the largest number of plants outside of the Angios])erms, have naturally received a good deal of attention from botanists, but this has been for the most part rather from the taxonomic and economic side than from the side of pure morphology. Nevertheless, some notable morphological work on the Fungi has been done by American botanists. Farlow's early papers on Fungi were among the first American contributions to the morphology of the cryptogams, and among the notable work of more recent date must be mentioned the very important contributions of Harper and Thaxter. Of the more recent phases of morphological work, that of experimental morphology must be mentioned, although this might be considered to be rather a phase of physiologv than of pure morphology. Some of the most important botanical work done imder the auspices of the Carnegie Institution of Washing- ton comes under this head, and the work of MacDougal and his colleagues perhaps represents the most important contribution to this department of botany that has been done in America. no The Plant World. We have, finally, to consider the suggestive lines of work inspired by De Vries' mutation theory, and the re-discovery of Mendel's work. It is not necessary to call attention to the great influence which both the Mutation theory and the Men- delian law of heredity have had upon the work both of botanists and zoologists during the past decade. It must be admitted, however, that as yet the results obtained by the numerous students of this latest fashion in biological investigation have hardly been commensurate with the expectations of the earlier disciples of De Vries. Nevertheless, the careful study of varia- tion, stimulated by these important theories, has been very usefid in reducing to definite form many phenomena long recognized in a vague way, but never before clearly formulated. The tendency of any striking new theor}' to draw away from the older and perhaps more humdrum lines of work a large number of students is a familiar phenomenon, and perhaps some lines of morphological work have suffered of late from the desertion of older workers, and the natural tendency of the younger students to attack the latest problems presented to them. It may be safely assumed, however, that there is plenty of work still to be done along the lines of the older morphology, and the verv creditable showing of the work of American mor- phologists during the past twenty-fi\-e years makes one hopeful that in the years to come the students of morphology in America will not fall behind their record of the past generation. Sta njord Lhi iversity. STUDIES IN SOIL PHYSICS, III. Soil water and tme Plant.* E. E. TREE. The purely inorganic aspects of the occurrence of water in the soil and its movements therein were discussed in the pre- vious paper of this series. It remains to notice the more vital matter of the relation of this soil water to the plant by which it is used and for the life of which it is essential. Of the con- ♦Published by permission of the Secretary of AKricultuie. Studies in Soil Physics. Ill elusions of the previous papers it is necessary only to recall that in normal soils under usual conditions most of the water exists in the form of films aiound the soil grains and in the capillary spaces. It is this film water which forms the source of supply for most of the useful plants. The cases in which the roots of a crop actually reach the ground water are comparatively rare. Nearly always this ground water must be raised by capil- lary action before it can be useful to the plant. The Water K'^tiation of the Plant. Water is, of course, an important material of plant food but in all ordinary land plants the total water used is far in excess of that required for mere nutrition. Water passes not only into but through the plant — is both absorbed by the roots and "transpired" by the leaves. We know fully neither the mechanism of absorption nor the mechanism of transpiration and we know very little of the mechanism of transfer from roots to leaves — the much discussed problem of the' ' ascent of sap". But these gaps in our knowledge, however regrettable, matter little to the present "discussion. We need to know only that there w a water stream through the plant — ■ and here is the important point — that its rate of flowjmay be limited or restricted at two points: the point of exit and the point of entry. The water equation of the plant is determined by two rates, the rate of transpiration and the rate of absorption. Now these rates are not necessarily nor directly i elated. They ma> vary almost independently and either may be larger than the other. Obviously when transpiration is greater than absorp- tion the plant is losing water and drying, while, when absorption is greater than transpiration it is gaining water and swelling. Obviously, also, neither of these unbalanced conditions can long endure if there is to continue to be a plant. In one case it will dry up and die and in the other it will swell up and burst. Over extended periods of time, then, the summation of ab- sorption must equal the summation of transpiration, plus what water has actually been built into plant tissue. The plant might be compared to a water reservoir, into which water is running and from which it is being diawn. If the rate of exit be greater than the rate of entry the reservoir will run dry; if it be less it will run over. Either condition may be as- sumed fatal to the proper functioning of the system To 112 The Plant World. be useful the reservoir must be kept filled to a level which must be, if not absolutely constant, at least variable only within definite and lelatively narrow limits. Similarily in the plant, transient excesses of transpiration over absorption or vice versa are peimissable and harmless, long maintained differ- ences are fatal. * Since, then, these rates of absorption and transpiration are so important to the life and the health of the plant it is expedient to review a little the factors which control them even though, in the case of transpiration at least, these factors are fairly well known and appreciated. The factors which control the rate of transpiration are partly internal and de- pendent u] on the plant, and ] artlv external and dependent upon its environment. Of the former there are prob- ably two, the mechanism of exposure (including the amount and character of the surface of the internal spaces of the leaf, the character of the cell membranes the nature and number of the stomata, etc.) and the concentration (acting here through its effect on vapor pressure) of dissolved substances in the cell solution from which the evaporation is taking place. The former or mechanical factors are probably pretty nearly con- stant for any one plant. The external or environmental factors are the tempera- ture and the humidity of the air and its rate of move- ment— the wind. All t]:ese may be included in the one ex pression "the evaporating power of the air." This it is which practicallv controls the transpiration of any given plant. An increase in the concentration of the cell solution does, it is true, lower the rate of evaporation (here transpira- tion) but this lowering is small and seldom comparable with changes produced by variations in the evaporating power of the air. If this evaporating power be greater than that to which the plant is adapted or to which it has been accustomed the plant dies. The rate of absorption is also controlled by factors which may be divided into those determined by the plant itself and *Tn actual fact these is usually a difference between transpiration and absorption and it is usualy diurnaly reversed. The plant looses water during the day and gains it at night. There are some few plants also which have considerable capacity for storing water and are able to withstand long periods of excess transpiration by drawing on water which had ))een stored during previous periods pf excess absorption, Studies in vSoiIv Physics. 113 those determined by its environment. The former are again a mechanism — the mechanism of root absorption — and a factor depending upon the concentration of the solution in the root cells. This concentration factor is here osmotic in nature and depends upon the fact that water will pass through a semi- permeable membrane, such as the cell wall, from a solution of lower osmotic pressure to one of higher. If, then, the cell solutions of the root liave a higher osmotic pressure (which means, in most cases, higher concentration) than the soil solu- tion, water passes from soil to root and, other things equal, the rate of passage varies directly with the difference in concentra- tion, though perhaps not in exact proportionality thereto. The urging force which causes water to move into the plant at all is this same difference in osmotic pressure, and the greater the difference the greater the force. * The mechanism of root absorption, (the surface exposed, the permeability of the membrane, etc.,)is, like the mechanism of transpiration, nearly constant for any given plant and, like it also, is of practical importance only as setting an upper limit. Not more than so much water can pass into a given plant even under the best soil conditions, and if the transpiration exceed this amount the plant will die though its roots be bathed in unlimited water. The external factor in absorption is the capillary pressure X of the water in the soil. For any given soil against any given plant there is probably a certain content of soil water below which that plant is unable to further extract moisture. The pressure under which the water is held in the capillary spaces and in the films about the soil grains is then greater than the difference of osmotic pressures urging the w^ater into the root. But this limiting water content even if it be a physical reality] | is quite low and it is seldom that useful soils are so dry as this throughout their whole mass. The importance of the phe- •It may seem that this theor>' of the action of osmotic forces on root absorption is incon- sistent with the fact that dissolved food materials enter the plant through its roots. When the cell solution is more concentrated than the soil solution nothing but water can enter, and when it is less so nothing at all can enter. To the outline theor>', as above stated, this objection is perfectly valid. But not all of the osmotic theory has been stated. The considerations of partial and selective permeability and the effects of the presence of many different salts in the solutions have not been discussed nor will they be. The theory as stated applies accurately enough to the water stream, and with the more precise matters of nutrition and total absorption we are not here concerned. JSee the previous paper of this series. Plant World, 14.60, 1911. As there pointed out bygroscoptic forces are not practically important in ordinary moist soils. II Thi» matter is more fully discussed below 114 The Plant Wori.d. nomena lies elsewhere. It is apparent that the plant roots can be actually in contact with only a very small part of the soil at one time, and, as water absorption goes on, this soil which is touched by the roots would be very soon dried out were it not for one thing. More water is immediately supplied from other parts of the soil by capillary movement. * If the rate of this movement be low, the rate of water absorption must necessarily be low also even though there be plenty of water in the soil as a whole. The dearth of water is in the contiguous soil only. It is not that there is too little water but that it is too slowly supplied. This is often the case when plants wilt and die from sudden hot winds. The rate of transpiration sud- denly jumps up and the plant is dried out and killed before the saving water can move through the soil and reach the roots. It will be noticed that factors depending upon the concen- tration of the cell solution appear in both sides of the equation — as controllers both of transpiration and of absorption. This is why it was necessary above to say that the rates of absorption and of transpiration could vary almost independently. The concentration relations are the reason for the "almost." It will be remembered that transpiration decreases with increase in sap concentration, while under the same conditions absorp- tion increases. It is apparent, therefore, that if some means exist by which the sap concentration at leaves and roots is kept substantially the same, there really is some relation between transpiration and absorption. To be more precise, there is an influence of the water content of the plant on both transpira- tion and absorption, as well as of them on it. If the plant be- comes too dry the concentration of the cell solution increases, and, in turn, transpiration decreases and absorption increases; both of which changes tend to remove the condition which gave them rise. But this process of natural regulation is efficacious between narrow limits only. It maintains the balance of transpiiation and absorption under normal conditions — ^pre- vents a dessication or a drowning due to any possible " mistake" of the transpiring or absorbing mechanism. It is competent also to care for the constantly occurring slight variations in external conditions, which are the evaporating power of the air and the supply of moisture through the soil. . *As discussed in the previous paper. _^ vStudies in Soil Physics. 115 It must be remembered, of course, that this concentration factor has nothing to do with the total amount of water trans- pired or absorbed, or with the draft of transpiration and the plant upon the water of the soil. So long as water be freely supplied to the plant roots and freely absorbed by them the sap con- centration will be the same whether the yearly transpiration rate be one ton or ten tons. It is only when the soil water begins to run low or the rate of transpiration grows high enough to tax the absorbing and transmitting mechanism, that the in- crease of sap concentration begins to operate and restrict the outgo. In summary, we may say that the rate of transpiration is controlled by the mechanism of exposure, the concentration of the cell solution and the evaporating power of the air, and that the rate of absorption is controlled by the mechanism of contact, the concentration of the cell solution and the supply of capillary water by the soil. The upper limits of transpiration and ab- sorption are fixed by the mechanisms concerned, — -by the mechanical construction of the plant; the equality of transpira- tion and absorption is maintained, under normal conditions, by the concentration of the cell sap; and the actual amounts of transpiration and absorption are determined primarily by the evaporating power of the air and secondarily by the rate of capillary supply from the soil. These latter factors also deter- mine whether or not the plant can be kept within that range of conditions, which is called normal, and between the limits of which alone is change of sap concentration able to maintain the proper balance of outgo and income. The danger of the fatal disturb- ance of this balance is almost entirely in one direction only. Plants frequently surfer from a deficiency of water but very seldom from an excess. Too much transpiration or too little absorption are the ever present dangers; there need be no fear of too little transpiration or too much absorption. To sum- marize again, a plant may die of drouth either (1) because the soil water has given out; (z) because the transpiration rate is greater than the maximum rate of absor, tion which the absorb- ing mechanism will permit ;*or (3) because the evaporating power of the air is persistently high enough to require a transpiration *For an instance of this see Livingston. Plant World 10: 269, 1907. 116 The Plant World. rate greater than the maximum rate of capillary movement of soil water to the roots. All this concerns extreme conditions, — conditions which have become "abnormal ' and under which life itself is not long possible. From the practical viewpoint the more normal, less extreme, conditions are of far greater importance. We are less interested in why plants die than in how (or how efficiently) they live. Under these normal conditions, which we may define as the conditions adapted to the particular plant under consideration, the total absorption will be equal to, and deter- mined by, the amount of transpiration, the latter quantity being fixed by the variable factor of the evaporating powxr of the air and the relatively constant factor of the mechanism of transpira- tion. Changes in the evaporating power of the air will be fol- lowed by corresponding changes both in transpiration and in absorption and the necessary balance of the two will be main- tained without change in the internal conditions of the plant. Suppose, however, that the exaporating power of the air in- creases to a point at which the transpiration it necessitates can just be balanced and no more by the supply of soil water. Suppose, then, the evaporating j ower of the air to increase a little more. Transpiration will increase but absorption can not because water can not be supplied any faster. Obviously the plant will lose water. But this loss of water causes an increase of sap concentration, this causes a reduction of transpiration, and equilibrium is restored, the only difference being that the cell solution is a little more concentrated than it was. Un- fortunately, however, this increase of sap concentration is (for some reason not fully known) unfavorable to the plant. Life may go on but rapid growth does not and this is obviously a matter of extreme importance to practical agriculture. Maxi- mum yields can be obtained only when the possible rate of sup- ply of soil moisture is sufficient to balance any transpiration which the climatic situation is likely to require. The Wilfing Point. The ideas elaborated in the preceding section can be a])plied with profit to a few of the conceptions current in the borderland of plant physiology and soil physics. Let us take first the so-called "wilting point," usually defined as the water content at which a given plant will wilt permanently Studies in Soil Physics. 1 1 7 in a given soil. It ought to be obvious that this quantity will depend primarily, not on the plant nor on the soil, but on the evaporating power of the air. But strange to say this apparently obvious fact has been either overlooked or disregarded by nine- tenths of the workers who lia\e made wilting point determina- tions.'■■' The temperature and humidity are almost never stated and in most cases thev were apparently neither measured nor controlled. Another matter almost alwa\s neglected in deter- minations of the wilting point is the rate of movement of water through the soil. The plant may wilt, not because of a lack of water, but because the water is unable to move through the soil and to tlie plant as rapidlv as it is being removed by trans- piration. Nor will this possible error be removed by determining (as is usually done) whether or not the wilting be permanent. For permanent wilting and death will result from any continued excess of transpiration over absorption, whether the deficiency of the latter be due to total lack of water or to a too slow supph-. To have any meaning either for plant physiologist or soil physicist the wilting point must be determined with reference to the evaporating power of the air. Ivven so determined, local and occasional experiments are of little value and geneial ex- periments, though potentially very useful, would be exceedingly tedious and even more costly. If experiments are to be made in this field they had better l)e u])on the rate of transjjiration which is fatal with full water supply, upon the minimum rates of absorption and transjiiration which are jjossible, or, best of all, upon the amount of water which will be transpired (and hence extracted from the soil) l^y a given ])lant in air of a given evaporating i)ower. Available and Non- Available Water. The concej:)t of non- availaljle water is closely related to that of the wilting point. Non-availal)le water is usually defmecl as that percent of water which still remains in the soil after the ])lant lias wilted. As so determined land I am aware of no determinations made other- wise) it is subject to all the errors which affect the determination of the wilting jjoint and wliicli lia\e just been discussed. Hut further than this there is no real assurance tliat there is any sucli thing as non-a\ailable water. Nine times ottt of ten a plant dies ♦There are, of course, a few physiologists who have given full alteiilimi ts change the api earance of the grain the first season, and there is a strong ])r()l)a'nlit\' that on an ear on which crossed grains are visible there are other crossed grains which show no exte nal sign of mixture. The directions for growing stock seed are both of practical and theoietical interest and are rej^roduced in detail. First formulate a very clear conception of ])recisel\ what an ideal plant of the sort to be grown should be, not onl\- as to grain and ear, but as to stalk, husk, silk and tassel, for this is essential to the raising of the best seed of the sort. With this conception in mind, or what is far lietter, clearh- \vritten out and illustreted by photograj)!!, go into a field cf the sort at the time the plants are coming int) silk, and mark with a string or bit of cloth, or in some way a number of stalks. It is wise to select at least a hundred plants which are as nearly alike and as typical of the sort as can be found. 126 The Plant World. When the grain is in the dough state, assemble the marked stalks and, after stripping down the husks, very carefully select and tag those in which the ear and the grain are nearest to the ideal. The ears from each of tliese selected plants should be carefulh- numbered, dried and stored. The next spring mark out near tlie center of the largest available field of the sort, a block of 4, 9, or 16 square rods for each of the selected ears, and plant each block with seed from one of the selected plants. It is wise in making the planting to reserve at least one- fifth of the seed on each ear, not only for replanting, if necessar^', but so that reference ma\" be made to the exact character of the I)arent stock. \\ hen the corn is coming into silk carefully go o\ er the l)locks and select those in which the ])lants in stalk, leaf, husk, silk and tassel are most uniforralv of the desired character, rejecting the plants which show the greatest varia- tion, even if some of them, as will in all probability be the case, are among the most perfect plants in the field. When the corn is passing into the dough state go over the selected hi ;cks, and, stri])ping down the husks, select the blocks in which the ears are most uniforndy of the desired varietal character, i ejecting, as in the selection of the individual plants, all the ears, no mattei how perfect they may l)e, from the blocks showing the greatest variation. As a ride it will be best to select se\ cral blocks in order to the loss in vegetative vigor which in the corn plant, often follows too close breeding. From the chosen blocks select a number of the most per- fect ears, to be tagged, numbered, kept separate, and again planted in separate blocks next season. The balance of the corn from the selected blocks can be gathered and the better ears bulked and used the following season for planting the field in which the seed l)locks are to be located. Working in tliis way, never losing sight of or changing the ideal varietal characteristics of the sort, alwaAS selecting from the most uniform k)t, resisting the temptation to use an ex- rcptionall)- jjcrfect ear fotind in a variable block, one can have in a few years established strains which will be greatlv super- ior in practical \alue to most of the seed now used. The second half of the bulletin is devoted to the growing of garden beans and peas for seed, and includes important sug- Current Comment. 127 gestions based on experience in the eastern states, in California and elsewhere. — V. M. Spalding. Vegetation of the Galapagos Islands. — Stewart accom- panied the expedition of the California Academy of Sciences to the Galapagos Islands in 1905, and has written an extended paper * chiefly devoted to listing the flora of the islands. A detailed tabular scheme shows the distribution of the flora among the 20 princij^al islands of the group from whic^ the author deduces that there is a strong probability that the islands were formerly fused into a smaller group, or perhaps a single island. The num- ber of the species representative of the several genera and families of continental ])lants is so small that the hypothesis of a former connection of the Galapagos with the mainland does not appear to be valid. A brief description of the vegetation of the islands calls attention to four types occupying successive altitudes in the larger islands. The coasts are fringed with deserts in which the aborescent columnar cactus, Cereus sclerocar pus , and some eight other cacti are conspicuous, with species of Bur sera and Croton. A ' ' Transition P^egion" and a ' ' Moist Region' ' are described, in which the vegetation approaches the character of tropical rain forest. At altitudes of 2000 to .3000 feet the the forest is replaced by" Grassy Regions "chiefly covered with a species of Paspahim. The operation of several climatic factors is touched upon, and the invasion of tlie recent lavas bv vegeta- tion is brieflv described... — F. S. NOTES AND COMMENT. A distinct sense of pleasure is given by every writer on elementary and secondary school work who decries the pre- valent excessive attention to method, which so often leaves matter as a consideration of very secondary importance. Pro- fessor Suzzallo, af Teachers College, Columbia University lias written a critical review of recent tendencies in the teaching of arithmetic in the current number of the Teachers College record. ♦Stewart, Alban, A Botanical Survey of the Galapagos Islands. Proc. Cal. Acad. Sci. IV Ser.. Vol. 1. pp 7-288, I map, 18 pis.. 1911. 128 The Pi.ant Wori.d. Method, as a special professional technique, is all well enough in such a subject as arithmetic, as Professor Suzzallo insists. It is the method which exaggerates the importance of one idea and the tendency to make methods uniform among all schools to which he particularly objects, saving, ''It stifles teaching as a fine art, and makes of it a mechanical Ijusiness. Under these conditions onlv those actitivies which fit the machine routine can go on. Thus it hap])ens that we memorize, cram, drill and review, and soon the subtler processes of thinking and evaluating, which are the best fruit of education, cease to exist. ' ' Fortunate are the biological sciences, which lend themselves so poorly to niethodology ; both the inherent nature of these sciences and the temperamental structure of those who culti- vate them make it difficult to place the harness of pedagogy on a steed which moves so swiftlv. It is proposed to inscribe on the new laboratory of the Brooklyn Botanical Garden the names of men, ancient and mod- ern, who lia\e made noteworthy contributions to the science of botany. The attempt to obtain a concensus of opinion from living botanists as to who should be awarded the highest places suggests some interesting reflections. Suppose any of these worthies, from Aristotle to Linnaeus, came to Brooklyn and saw their names adorning this temjile of fame, and were then shown about by an assistant who should explain the use of various stains and modants, the clinostat, the experiments in chemo- tropism, the pedrigeed cultures, in short the outfit and work of a modern botanical laboratory. One can easily picture their confusion of mind. And yet it is very certain that few out of the long list of names tentatively ]:)roposed could be omitted without evident loss. So slowly did botany become a science; so graduallv did its modern content take form; so far removed from its simple beginnings are its modern methods and aims, that we now seem quite out of their world; and yet the early fathers mav well be honored for their fruitful thoughts that in vaiious form and measure have helped, even remotely, to build the foundation of the science as we know it. Volume 14 Kuinber tj The Plant World A Magazine oK Geni:rai, Botany JUNE, 1911 CLBLVTIC Sl'LlvCTlOX IX A PIVHRID PROGKXY. D. T. MAcDoroAi,. A number of acorns of Ouercus luicyof^Jijl/d were secured from some trees on Staten Island, X. \., in October, LS95, and germinated in the Xew York Botanical Gardens a few weeks later. The cidtures were made for testing the character of the living material grouped under this name by systema- tists, and with especial reference to the probable parents in case evidences of hybrid origin were found. '•' The 55 plantlets obtained were seen to vary widelv from each other as to leaf form, although the range of variation on any one plant was small. By the close of 1906 it was seen that the entire lot might be arranged in a linear series, in which the ])lants at one end i^ore broad lobed leaves much like those of the red oak, while the individuals at the other extreme resembled the willow-leaved oak {Oiicrcus Phellos). This fact was taken as evidence strongly sup])orting the conclusions of Dr. A. A. llollick and other bolantists that 0. hcicrophylla was a hybrid between the red oak (0. rubra) and the willow leaved oak((_>. Phellos). I'lants representing the suj^poscd h\ brid species have been known for a long lime, so that nothing might be said as to the relationshi]) of the plantlets grown and the original cross. The parental trees from which the acorns were taken might have been first generation crosses, or on the other hand they ma\' have represented the nXh generation with many possibilities ♦ MacDougal, Hybridizatioii of Wild Plants. Bot. Gaz.. 43: 11. 1907. 130 The Plant World. as to secondary hybridizations "svith either parent species or Avith various recombinations. The chief fact of interest in the present connection was that of the possible reaction af the various types to cHmate. To test this a series of tAvelve young trees representing the total range of leaf-variation %vas taken to the Desert Laboratory at Tucson, Arizona, and exposed to the extremes of the arid sub- tropical climate at that place. In addition to the direct action of the meteoric factors, the soil was of course widely different from that of the habitat of the plant on Staten Island, since soils are so largely a function of climate. First of all it was noted that these introduced oaks were attacked l)v the desert rodents which found their lea.es much ViH 1. — Plciiitlct-^ from progeny of tree of Qui reus heterophylla. J hears leaves not dij tinguishable from thoje of Q. Phellos, and 17 resembles Q. rubra- //. UI, J^', anrt V form a series between / and 1'/ — Pholognpheci Anril, 1906. more to their taste than those of the oaks natixe on theadjacenl mountain slopes. This fact, however, would not have operated verv stronglv as a selective factor. The hot, dry fore-summers and arid after-summers were the real selective agencies deter- mining survivals, and the notes on the cultures illustrate the fate of such a ])rogeny very clearly. The entire lot of plants survived tlie seasons of 1907 and had cast their leaves with the frosts of December, being noted as entirely dormant on Dec. 10. In 1*^)08 the individuals near the middle of the series rej)resenting the trees usually passing under the name of Q. hchrophy/la were latest in awakening. Elimination began in 1^.09 and by June \?>, only five plants of the narrower leaved types survived. On Oct, 22, but four The Blooming of Timothy. 131 remained. Three of these soon perished, so that the spring of I'JIO found but one survivor, that of a type represented by fig. 1, No. Ill (vSee also fig 8, Thk Plaxt World, Feb. 1907). This remaining indi\ idual did not live through the dry fore-summer. The anah sis of the observations shows that the leaves supposed- ly embodying (lualities of the red oak were least fitted to endure the desiccating action of the desert, which was endured longer by the narrower more indurated leaves resembling those of the willow-leaved cak. A jihysiological consideration of the lca\ es of these types would liave led to the expectation of such a result. The suggesti ui lies near that the action of the climate observed with these plants is one representative of countless occurrences in nature. A linear series from the ])rogenv described nl)f)\p was also established in the New York Botanical Ciardcn, but no report has yet been made as to their action cr survival. OBSERVATIONS ON THE BLOOMING OF TIMOTHY. Charles F. Clark. The flowers of timoth\-, like those of the majority of other grasses, are so small and inconspicuous that they rarely receive the attention given to more conspicucous floral organs. The observations described in the following pages were made by the writer in connection with the timothy breeding experiments which are in progress at the Cornell University Experiment Station and are being published with the hope that they may be of some scientific interest. The llowers of timothy are borne on a so-called head or spike which is in reality a contracted panicle in which the rachillae are much reduced, giving the inflorescence a spike- like appearance. Each flower, which with its two inclosing outer glumes comprises a s])ikelet, consists of a flowering glume, a palea, an o\ar\', two distinct st\ les with plumose stigmas, and three stamens. ' The process of blooming is simply a pushing out/df the stamens and stigmas, there being no distinct openinglof Jthe fl" if the ])lant is well ad\aneed in Ijlcxnn- ing, the greater part of the head may come into bloom on the same day. There is, howexer, a narrow zone at the base of the head which the writer has never observed to come into bloom initil the end of the bloomin.q- period for that particular head. Not all of the (low ers in a gi\ en area begin blooming at the same tinic;so that the same part of the head may come into bloom on several successive days. The blooming of tiniotlu' is very closelv associated with weather conditions. When these are favorable a large propor- tion of the llcnvers on a gixen head will often come into bloom on the same day while, on the other hand, conditions may be so unfavorable as to entirely prevent blooming. These inlluences seem to be the resultant of several factors so closely interwoven tliat they are diflicult of exact analysis. An attempt was made in 1910 to determine these factors by means of a self recording hvgronieter and thermometer w^hich gives continuous records for humidity and " temi)crature. The results were somewhat inconsistant and failed to give a complete solution of the ques tion. This was probably due in part to the difificulty of secur- ing an accurate hmnidity record at all times though the presence of other factors may also have been responsible for part of the inconsistencies. The records, however, showed unanimously that tempera- tures below 50° i'\ or above 65° F. and relative humidity be- low 75° or above 93° at 2 o'clock .\. .m., were followed by little or no blooming, also that several hours of stationary temper- ture and humidity during the preceding afternoon and evening, which condition often prevails during a stormy or cloudv period, resulted in the entire absence of bloom. Cornell University, Ithaca, N. Y. 136 The PlaxNT World. THE INFLUENCE OE LOW TEMERATUREvS ON THE DISTRIBUTION OF THE CxIANT CACTUS. Forrest Siikkve. 'i'lic work of ]\Iuller-Thurgaii and of Molisch has shown the variety of w a\s in which low temperatures may be fatal to dif- ' fcrcnt species of plants. Tropical forms may be killed by con- tinual exix:)sure to temperatures just above freezing; other forms sur^•ive temperatures slightly below freezing, but suc- cumli (ui tlie formation of ice in tlieir tissues. Certain plants will withstand the formation of ice in their intercellular spaces at a few degrees below freezing, but will die at a sudden pronounced lowering of temperature while tlle^' are in a frozen state; at the same time that very luany arctic species will withstand total freezing together with ver>' low temperatures. In many cases that have been investigated a sudden thawing proves fatal after a given set of cold conditions, although a gradual raising of temjierature enables them to survive. The low temperatures of winter have been recognized for a long time, both in scientihc and practical work, as important factors in limiting, the northward and vertical distribution of tropical and sub-tropical i^lants. The fact that these plants varv greatl\- among themselves in resistance to cold, and the fact that it is different ])hases of winter cold that are fatal to them, is i)ro\cd 1)\- the lack of a coincidence in the northern limit of distribution among an\- considerable number of them. The line which marks the extreme southern limit of frost is the most important climatic boundary in restricting the north- ward cxtensi'Mi of ])eremiial trop.ical s])ecies, and it is the line along which the inlhience of winter cold is the simplest in its operati n. In the huiitation of the sub-tropical species which extend nortjiward of tliis line a \ariety of phases of winter cold \\illiont (loul)t are o] eratixe. Chief among these are: the greatest number of consecutive hours during which the temj'jera- ture falls below freezing; the total number of hoius of frost in a single winter; the absolute mininnnn reached and the length of the winter, reckoned from the first frost of autumn to the Distribution of the Giant Cactus- 137 last one of spring. For all sub-tropical plants the greatest num- ber of consecutive hours of frost and the absolute minimum are the most im]:ortant of these factors, while the others mentioned are more strongly o}:^erative further north. In any consideration of the geographical importance of the operation of these factors it is obviously necessary to consider only the conditions of the coldest winters, which serve as a check on the movements made by species during the milder winters. A consideration of the factors which have to do with the distribution and activities of the Giant Cactus {Carnegiea gigan- 6 A.M. 7 10 11 12 1 P.M. 2 Fig. I. Cunes showing daily march of internal temperature in Giant Cac'i on a cold day. Dotted line: ;iir temperature. Heavy line, temperature of cactus 30 cm. high. Thin line: temperature of cactus S cm. high. tea, Ccreus giganteus) led me to believe that the greatest number of consecutive hours of freezing is the most important climatic datum in determining its northward range, and led me to in- vestigate its ability to withstand freezing temperatures, and the character of the winter cold conditions within its range. The Giant Cactus belongs to a group of about 65 species of trop- ical and sub-tropical arborescent columnar cacti all allied to the genus Cereus. Of this number Carnegia gigantea, Lopho- cereus schoiiii and Leviaireocereus thurberi are the only ones 138 The Plant World. which extend northward above the limit of frost. The distri- bution of Carnegiea stretches from the mouth of the Yaqui river, in Sonora, northward along the Gulf of Lower California and the Colorado river to the mouth of the Bill Williams river in Arizona, and eastward to the Santa Rita mountains in south- ern Arizona, and up the various tributaries of the Gila river to approximately 3900 feet (1190 m.) elevation. The vertical limit of occurence of Giant Cactus in the desert mountain ranges in the center of its area is 4500 feet (1375 m.), while its abundant occurrence ends rather abruptly at 4200 feet (1280 m.). The distribution of the giant Cactus to the westward of the Col- orado river is undoubtedly limited by the low summer rainfall of interior southern California. In order to ascertain the character of the winter cold con- ditions wnthin and just outside the range of the Giant Cactus an examination of climatological records was made for the four localities in Arizona at which thermograph records are regularly secured. Yuma, Phoenix and Tucson are within the range of Carnegiea, Flagstaff being considerably above it. The figures in the following table are for the winter of 1909-1910 — the most severe for several decades. STATION YUMA PHOENIX TUCSON FLAGSTAFF Elevation (feet) 141 UOS 2663 6907 Elevation (meters) 4.3 337 812 2106 Number of days with freezing tem- perature 13 14 15 193 Number of hours of freezing tem- perature 32 89 126 2200 Greatest number of consecutive hours of freezing temperature 8 13 19 132 Minimum temperature during great- est number of hours (Fahr.) . . 25 23 17 —22 Same (Centigr.) -4 -5 -8 -30 The most important figures of this table are those which show that the Giant Cactus is capable of withstanding 19 hours of continued freezing temperature and as low a minimum as 17°F.(-8.3°C.). It may be noted that Flagstaff possesses a climate much more rigorous than that of the other stations. The fact that Tucson is only 1300 feet below the limit of the Giant Cactus, while Flagstaff is 3000 feet above it indicates that the cold conditions at Tucson are nearer those which limit the Giant Cactus than are those of Flagstaff. Distribution op the Giant CactxJS. 13?> Curves drawn to show the changes of intensity of climatic factors, as followed from one locality to another distant one, commonly show a smooth rise or fall. However, on passing from lower to higher latitudes o' altitudes the number of con- secutive hours of freezing becomes gradually greater until the point is reached at which davs without a mid-dav thaw are first encountered; there is then a sudden rise from about 22 hours of frost to from 36 to 42 hours, according as the fall and suhse- FiG. 2. Young Ciant Cacti fro>en 42 and 29 hrs., respectively, showing destruction of tissues at base. quent rise of temperature are abrupt or gradual. In other words this factor is unique in that the curve expressing its changes of intensity possesses a sudden vertical rise, or indeed a number of such rises. The line along which this takes place in the severest of winters is bound to be an important limit of plant distribution, at least it is so along the line of sudden rise which lies nearest the absolute frost line. It has not been pos- sible to locate this isohoral line exactly from the climatological 140 The Plant World. data obtainable for Arizona, but the few figures at hand, when plotted in relaticn to altitude, and supplemented by tlie temperature data accumulating from the vork of MacC(.ugal and of the writercn the Santa Catalina rrountains, show a strong probability that the line lies in the vinicity of the limit of the Carnegica, which is also the limit of Parkinsoiiia microphyUa, Cercidium torreyannvi , Fouquicria splcndens, Encelia jarinosa Acacia greggii,Franscria deltoidea, Cassia covesii and a number of other characteristic desert species. The stout form and high water content of the Giant Cactus suggested the necessity of investigating the relation between the daily curve of its internal temperature and the daih' curve for the air, both for the sake of learning whether a given number of hours of freezing air temperature meant as long a subjecting to freezing for the cactus and whether as low a min- nnim A^ould be reached by the cactus. With this object incu- bator thermometers were inserted, to a depth of 3 cm. in two individuals, 8 cm. and 30 cm. high respectively, ani the tem- perature of the air was read simultaneously. Keadings were also made on the north side of an adult cactus at depths of 3 and 7 cm. All the observations made showed a rapid response on the part of the cactus to the changes of air temperature, and all showed a greater amplitude in the daily curve for the cactus than in that for the air, excepting in the case of the deep- er thermometer in the adult cactus. The curves shown in fig. I exhibit the data secured from the young cacti during a clear day (Feb. 22, 1911) and one of the coldest nights of the winter of 1910-191 1. Observations on the same cacti on a completely cloudy day showed a rise of temperature for the larger one almost exactly parallel with the march of the air temperature Clear days are usually juxtemporaneous with the coldest nights of winter, and under such conditions insolation carries the diur- nal temperatures of the cactus above that of the air, while rad- iation, together with a slight amount of transpiration cooling, carries the nocturnal temperature below that of the air. In other words the surface cells of the cactus are exposed to lower temperature than those indicated by the air thermometer, and the cactus is subjected to a slightly greater number of hours of freezing temperature than is indicated by the air thermo- Distribution of the Giant Cactus- 141 j;rapli trace. The actual conditions of temperature for a given individual are a function of the amount of heating or precooling it has received during the preceding day. In order to observe the actual eflectsofexpc.sures to freezing temperature varying v.ithin the Hniits of duration common to central Arizona, a number of }oung Giant Cacti were potted, of such size that they could be placed in large freezers. The fact that the Giant Cactus is able to survive for months without renewed supplies of water I'd me to pi eservecnly the mi in ] arts T'IG. 3. Young Giant Cacti frozen 6 and 1 5 hrs., respectively, showing uninjured condition of the root system, and to leave the potted plants without watering previous to their use. 'Ihree sets of experiments were made, in which a total of 11 plants of 18 to 28 cm., height were used and pot-grown seedlings less than 1 cm. in height. In each of the three sets of experiments there was one of the larger cacti in which an incubator thermometer was inserted to a depth of ^ cm., with its scale projecting above the lid of the freezer, while there was another thermometer placed to show the air 142 The Plant World. temperature surrounding the cactus. In the other experiments of each series only the air temperature was read. The freezing mixture of ice and salt was renewed as required. The several experiments differed in the amount of pre-cooling given, and in the length of time the plants were subjected to an air temper- ature below freezing. In each case the cacti were allowed to cool gradually by opening the lid of the freezer and allowing the ice to melt during the next 12 hours. This always resulted in surrounding the cacti with air that vas cool but not below- freezing. After from 12 to 20 hours they were removed from the freezers and placed in a cool room. On the following day they were placed in a green house where the temperature rose to 70° to 80° F. in midday. Following are given the corrected figures for the tempera- ture of the air (C.) and of the cactus at the outset of the three tests in which thermometers were placed in the tissue of the cactus. CACTUS No. 1 CACTUS No. 5 CACTUTS .Nfo. 12 NOT PRECOOLED PRECOOLED 15 HRS.AT NOT PRECOOLEU 3° TO 5° C. Air Ca ctus Air Cactus Air Cactus Jan. 14, 5 p.m. put in Jan.22, 6 .A.M. put in Jaii.25, 2 P.M. put in 6 p.m. 0. 10.5 7 A.M. -8 -3 4 P.M. -6 4.5 7 p.m. 0. 6.8 8 A.M. -8 -3 5 P.M. -6 2.0 8 p.m. 0. 4.0 9 A.M. -7-3 6 P.M. -5 0.5 9 p.m. 0. 2.0 10 A.M. -8 -3 7 P.M. -4 0.0 10p.m. -1.0 1,0 11 A.M. -8-3 8 P.M. -2 0.0 11 P.M. -3.0 - -0.5 12 N. -8-3 9 P.M. -7-0.5 12 m. -3.5- -2.0 10 P.M. -7-0.5 The temperature of cactus No. 1 fell no lower than -4° and it was kept between that temperature and zero for 42 hours. Cactus No. 5 was precooled, and when placed in the freezer was cooled vigorously and taken as low as -11°. It was not allowed to go above -5°, being kept at temperatures below freezing for 29 hours. Cactus No. 12 was taken only to - 3° but was kept below freezing for 46 hours. In each case the plant was allowed to stand in the greenhouse for several weeks after Distribution of the Giant Cactus. 143 freezing, alongside unfrozen controls of the same size which had been gathered at the same time and treated in every other respect in the same manner. Within two weeks after freezing all three cacti had begun to show a blackening of their tissues around the base, which through a disturbance of their turgidity lost them their natural erect position. By four weeks after the freezing No. 12 had become black and soft throughout its lower half. Six weeks aftei the f eezing No. 1 and No. 5 were photographed (Fig. 2) so as to show the injured tissues at the base. These individuals were kept for another month and failed to heal or show signs of recovery, at the same time that the controls were still in normal condition. Seven other young cacti were subjected to freezing tempera- tures for periods as follows: No. 4 9 hrs. No. 19 (jjrecoi led 4 hrs.) . . 6 hrs. No. 9 6 hrs. No. 24 14 hrs. No. 13 15 hrs. No. 25 14 hrs. No. 18 (precooled 2 hrs.) . . 6 hrs. None of these individuals showed signs of injury from frost on being kept for two months in the greenhouse with the others. Two of tlicm. No. 18 and No. 13, are shown in Fig. 3. Seven seedlings of Giant Cactus one }ear old were sub- jected to periods of freezing of from 6 to 42 hours. None of the three subjected to 42 hours survived, but one subjected to 9 hours, and one to 15 hours perished. The fact that the seed- lings were hot-house grown, more succulent and less heavily cuticularised than outdoor seedlings probably are * prevents me from drawing any conclusions as to their being less resistant than the juveniles and adults. Although the conditions under which these experiments were done were somewhat artificial as respects the coldness of the soil and the high humidity of the air surrounding the plants at the time of exposure to cold, yet I cannot believe that these conditions affect the results materially. The seven experi- ments in which individuals were subjected to periods of from 6 to 15 hours of frost reduplicated conditions under which the Giant Cactus is placed in nature, and their survival was no more than a confirmation of what might be observed in the •I have never seen any spontaneous seedlings of this size in the field, nor has anyone else, so far as I know. 144 The Plant World. field at appropriate times. The three experiments in which individuals were given from 29 to 46 hours of freezing redupli- cated the conditions to which they would be subjected at higher altitudes and to the northward of their natural range, and they indicate the inability of Carnegiea to withstand such longer durations of cold, 1 made no examination of the tissues of the cacti which were given the longer durations of frost. It is probable that 20 to 36 hours of frost would kill some individuals and would fail to kill others, and it is only the jump in the con- trolling climatic factor, to which allusion has been made, that fnakes the natural ojeration of this factor decisive and limits the distribution of Carnegiea in an abrupt manner. The oc- currence of a single day without mid-day thawing, coupled with a cloudiness that would prevent the internal temperature of the cactus from, going above that of the air, would spell the de- struction of Carnegiea; and the parallel evidence of the climato- logical records and of the experiments which have been described appears to explain the limitation of its northward distribution. The branched arborescent cactus Opuniia versicolor ascends in the desert mountain ranges to v5,800 feet (1,768 m.) and the small form Echinocereus polyacanihus reaches 7,800 feet (2, i80 m.), the highest altitude attained by any species of cactus in southern Arizona. Opuniia versicolor is common on the desert mesas and reaches its highest limit only on ridges and south- ern slopes, while the highest individuals of Echinocereus polyacan- ihus are found on cliffs and rocks where they are likely to be exposed to insolation and mid-day thawing. Freezing experi- ments similar to those described were carried out on young individuals of Opuniia versicolor 5 to 25 cm. high and on adults of Echinocereus polyacanihus. The 1 1 individuals of these species used were given various lengths of exposure up to 66 continuous hours of freezing without any injuries or fatalities. The longest of these exposures is about the length of time that frost would supervene when two consecutive days were without thaw, a condition which must exist in the mountains of Arizona at 7,1^00 feet altitude in every severe winter. The smaller and more widely distributed types of cacti nmst all be more resist- ant to frost than are any of the arborescent colunmar or the branched arborescent types. In the Rocky Mountains DlSTRIBUTlOX OF THE GlAXT CaCTUS 145 Ecliiuocaclus siuif^xojii is reported to range np to 11, ()()() feet altitude, while Opuniia wissoitricnsis lias been collected by Prof. J. Macoun on the Teaee In iver in Alhal)asea at lat. 3() deg. 12 min. An indication of the length of greatest exjjosnre to frost for Athabasca can be snrniised from the fact that the weather records for Ila\re, .Montana, 230 miles south of the limit of Opuntia luissojivunsis, show a continuous period of 2>^>i hotn-s (\^ days) of frost in the winter of 1909-1 'MO. In summarising it is necessary to bear in mind tliat the pJiNsical conditions of desert regions are such as to gi\e the dail\' temperature curve a nuich greater amplitude than it has in moist regions. At 'J'ucson there are very many da\s on which the mininnun and maxinnim tempera tiu'es are 50° h\ (30° C.) apart, and on exceptional da\s still further than this. ']*lic power of insolation to raise the mid-dav tem]:erature is so great in all deserts that occu];\- low latitudes and altitudes, that however cold the nights ma\' be the daib" maximum is carried al)ove the frost line. There ha\'c, in all ])rol)abilit \', been no da\s at Tucson in many hundreds of years on which the air temperature remained below freezing all day, and the ability of insolation to raise the internal temperature of the Giant Cactus makes it still more certain that none of the in- viduals of this species now li\ ing have endured more than 20 hours of frost, and ])criods as long as these are due sold}' to l^artialh' clouch' da\s of the winter rainy season. The winter tem])erature conditions of the higher altittides in the desert mountain ranges are very well indi ;ated b\ tlie figures given for I'^Iagstaff, w hicli itself occupies a i ass in a range of mountains surrounded by desert. An\ attemjjt to explain the limitation of the bulk of the desert sj eci s to altitudes of 4000 to ,S000 feet in the desert mountains mist lake account of the winter cold factors. l!etween those altitudes the condi- tions of atmospheric and soil aridity are stunewhat less seve e than on the desert lie or and ffotdiills, and 1 ct\\een 5000 and 7000 feet these conditions, as indicated by the natural \ege a- tion.are materiallv less severe. Between 5000 and 7000 feet, however, the vegetation is extremely o\ en, giving abundant opportunity for the invasion of desert sjecies into a region in which the atmospheric and soil moisture conditions are more 146 The Plant World. favorable, without by any means being moist. ]\Iy observation of numerous species of desert plants which ha\e l.een artificially irrigated or ]:rotected from extreme insolation shows that there is no one of tliem to which a slight amelioration of the atmos- pheric aridity, or a slight increase of the soil moisture, or of the number of tin:es the soil is made wet, does not permit both a greater vegetative and a greater reproductive activity. 'I'liese slighth' inijiroved conditions are to be found between ."^000 and 7000 feet altitude in the desert mountains, but they are to be found only where the winter cold conditions are such that desert species are unable to survive. In other words the failure of desert species to establish themselves in a region which seems at first sight to be a more favorable one than that in which they are common, is due to the oj^eration of a factor entirelv distinct from those which have to do with the appar- ent favoral)leness. Tlic Desert Lahoralory, Tucson. ' BOOKvS AND CURRENT LITERATURE. Altittdinal Limits ix .Mkditerraxeax \'egetation — Koch's ''Contributions to Our Knowledge of Altitudinal Limits of \'egetation in the ^Mediterranean Region" '"' emphasises especially and seeks to define the temperature re- lations of the vegetation, although recognizing the concurrent action of oilier factors. In Southern France, the Apenniiie peninsula, the Balkan region, Greece, Asia Minor, Syria and northern .Africa there is observed a horizontal distrilnition of the Mediterranean vegetation, of the forests, and the alpine vegetation and a vertical extension of the Mediterannean veg- tation as a whole and of such representatives as Laiiriis )iobilis, .\l]yht^ ri>iiiiuiiiti\\ I-iuius sy/raiica, Oiicrcus ilex and others. The principal results of the author's studies mav be summa- n/ed as follow,>: In the ^Iediter:anean region a parallelism of the lower and apper limits of ])lants is observed, with depar- tures i\\\ii to local inlluences. 'fhe upper limits are influenced bv tlie temjieratures of June and Jnh. In general the temper- ature of January influences the outline of the upper limit of * Koch, M., Bcitrage zur Kentnis der Hohen grenzen dci Vegetation im Mittelmeergebeite Dissertation, Halle, 100 pp. 1909. Books and Current Literature. 147 characteristic Mediterranean plants, ^vhile the Jnl\- temperature inlluences that of the middle iCuroiJean plants ocnrring in the regions studied. The isotherm of five degrees C. for January fixes the npper limits of the Mediterranean vegetation, and- the isotherm of ten degrees for July that of the forest; th.e upward curve of these isotherms defining in general the upward exten sion of the altitude limits in question. The annual ])recipita tion has a positive inlluence on the altitudinal limits of the middle European forest trees, while its inlluence on the xero- l)hilous representati\cs of the .Mediterranean vegetation is for most part negative. The altitudinal limits of nearly all the p'anls studied rise on api)roaching the African desert region, the con tinental lartsof Asia and the I'\ reman i.eninsula; while in gen eral the least upward extension is oljserved in. the Apennines and in the Balkan i eninsula. — \'. M. vSpai.dixc. Tiir: PilWT Di-posits < ii- Im.orii).\.- Tlar])er has published a rejort '■' of his reconuaisance of the ]jeat de] osits and peat- forming areas of I'lorida. In addition to a considerable mass of information relative to peat, the re] ort contains the best descrij^tion of the vegetation of iHorida which has yet been made. I'ourteen 'natural divisions" of the stale are outlined by maj) and brieily characterised as respects their topography, soils and vegetation. '1 he low elevation and immature topog- raphy of I'lorida give rise to a Ijcwildering variety of palustrine areas, which have naturally received more attention in this ])aper than the upland vegetation. Harper has described some 27 tyj^es of marshes, swam])s, bogs, "])rairies," "baxs" and other formations with wet substratum. He has used the charac- ter of the vegetation in distinguishing these areas and has fol- lowed the refreshing custom of giving them either such names as are locally used for them or else simjjle designations that are descriptive of their \egetation or their most ob\ious pli\sical characters. The alluvial and estuarine swamps and marshes appear to be clearlx differentiated from those in which the water is calcareous, the latter .uroup eml)racing the great majority of the areas described. Also of imi)ortance *Hurper, Roland M.. Preliminary Report on the Peat Deposits of I'-lorida Third .\uu . Rep. ria. State Geol. Sur\-., pp. PJ7, pis. 17-28. figs 17-30. 1 map. 1910. 148 The Plant WoRtn. in differentiating the palustrine areas are such matters as whether uater is running or stagnant, constant oi seasonally interniittent in level, and whether the area is young or old, in terms of the degree to which peat formation has gone on. It appears more than probable to the reviewer that many of the palustrine areas do not possess constellations of physical condi- tions which are sufficiently distinct to explain the differences in their vegetation, as c. q. the Gum {JJqnidamhar) swamps and the '\'\t\ iC/iftonia) swamps of western Florida. In fact, tlic work of I'ar] er suggests a most promising tield for work on the relative o] eration of i)hys'cal and historical factors in a com] arativel\- recent set of habitats. — I'. S. GkI'I-k Climatr Axi) A'lcci'TATiox. — -Koutos, in a pai)er * (in the infiucnce of climate on Greek forest \egetat'on, has d:scus^ed the clmatc of coast and hill c(nmtr\-, its changes corres])(inding to latitude and altitude, distance from the sea, direction of \\iiuls in relati n to rain, ; eographic features and climatic conditit ns incident to as] ect and exposure. The in- fluence of these varioiis climatic factors in their relation to the forest vegetation of Greece is consideied in some detail, as, for example, in regard to the influence of wind in determining the distribution of xero])hytic, h\groi?h>tic and tropM)ijliytic s] ecies of trees, and a somewhat extended account is given of the \arious f jrest zones a corrtlated with climatic factors. — -V. j\I. Si'.\i,i)iX(;. NOTKS AND CoALAllvNT.. iSritish l)otanists have shown no little activity within the ])a^t vear in ]?li\ togeographical work. Moss, Rankin, and Tans- lex- h"a\e re])()rted in 'Jlic New l^hyiohnjist on "The Woodlands of I'ingland," attem])ting to deal, in a general way, with the char- acter and distribution of different types of natural and semi- natural woodland in l{ngland. Types of Knglish woodlands are defined in connection with details as to composition and eco- logical factors. It a])pears that "climate shows its effects in ♦ Kontos, v., lipidrasis epi ten hellenikeii dasikeii blastcsin toy hellikoy kliinatos. 78 pp. Athens, 1909, Notes axd Comment. 149 ascending the larger hill masses, but in the lowlands iL does not tnateriallv affect the distribution of dominant trees, although it iniluenccs certain sj^ecics of the ground vegetation. vSoil is tlie greatest differentiating factor and influences the distribu- tion of woodlands thror.gh differences in mineral content, and humus-content". The same botanists have recently published other pa])ers. Rankin describes, in The NafKniliy't, the " Peat Moors of Lons- dale," with s] ccial reference to the lowland Moors, which arc either littoral or lacustrine. '1 he former, located in the drainage area around Morecambe Bav in north and west I{ngland, are a distinct ] In siogra] hie feature, and their vegetation sIuavs relaticmshi]) with the fens (f eastern I^ngland. "The hrst vege- tation grew in silt r.nder water, and in time became swamj) moor, to 1 e f( llowed later l)y heath moors; these phases being traceable from existing \ egetation and also from examination of remains in the peat, the lowest strata consisting of sedges and rushes, not lurch, as in the case of mcst upland peat moors." Moss, in llic New Phytoloqist, discusses "The Fudamental Units of ^'egetati( n," tracing the liistorical development of the concepts of the ])lant association and the plant fc.rniation fnun Humboldt and Criesebach down to the works of living writers. Warming's definition, "an association is a communitx of definite floristic com] ( sition within a formation"' ma\ be comjared with tliat of .M( ss, "A plant formatic n comprises the ]>n gressive associations which culn.inate in one or more stai)le or chief asscciatic ns, and the ietrcgressi\ e asscciatic ns which result from tlie deca\ of the chief ass( ciati: ns, so k ng as tliese changes cccui ( n the same habitat." Aside from the writers cited, all of whom ha\ e at least foruni- latcd a problem of scientific interest and imj^ortance, toward rhe solutifu oi which their wcrk has c( ntributed, there are ( thers who have for the ni< st ] art limited themselves to record- ing certain facts of distribution, which, like the lists ff species given in s' stenatic j^eriodicals, are likeh enough at some future time to ha\e more \ alue than is aj^j arent at present. On the whole, howe\ er. it is j Iain that if to the recent work of European botanists there is added that of American investigation in the field of ph} togeography, there is reason to feel that notw itlistand- 150 The Plant World. ing inherent difficulties this department of botanical study is more and more approaching the exactness characteristic of an advanced period of development. An article by i\rr. S. B. Parrish in recent numbers of Muhlenbergid on "The »Soulhern California Juncaceae" is \\()rth\ nf attention. This is cf)nc]uded in the December, 1910, number b) a tabular statement of regional and geographical distribuli'Mi, Avith a summary from which one at a glance may note which of the twenty-two sj^ccies listed are restricted to North America, which ones reach South America, Europe, and Japan, which are confined to the Pacific coast of North America, and those tliat are endemic in vSouthcrn Califfunia. The descriptions indicate character of habitat as well as distribution in altitude, and in elude critical notes on the constancy of characters. With this paper in hand one is in a position to study with satisfaction the dilTicult group of which it treats, over the territory covered by (he author, and to thank him for smoothing the Avay by telling the exact facts in clear English -with the succinctness and mature iudgment that come from many years of close oljservation and haljits of conscientious expression. In another number of the same journal there is a paper in which the writer makes new species out of such characters as the following: "The perianths are larger in the species here proposed as new; but a Ijettcr mark * . * * is the great length of the oblong and leaf like seg- ments of the involucre." Comment is unnecessarv. In a recent bulletin of the Bureau of Plant Industr}- (No. 204) entitled "Agricultural Explorations in the Fiuit and Nut Orchards of China," Mr. Frank M. Meyer gives a readable ac- count, illustrated bv recent photographs, of numerous A\ild and cultivated jilants studied bv him in China and [Manchuria, \\ith interesting suggestions as to habits and the availabilit\' of liard\' varieties for extending the range over which a given fruit ina\- be cnlti\ated in the United States. The need of dis- c-riniinatifn in the im])ortation of fruits is suggested by a judg- ment of one fruit as quoted : "it depends on what you eat them Notes and Comment. 151 as; as turnii)S they are certainly fine, but as pears I would rather not express any opinion." A storv of fascinating interest is the history of the coconut palm in America as it has been worked out, parth- from histor- ical and ethnological evidence and jiartly on botanical grounds, and set forth in Contributions from the National Herbarium by C). v. Cook. The first contribution of the author to this subject appeared in 1901, and the results of his further studies are sum- marized in tlie present ])aper {X'ol. l4, part 2). It is shown that all the palms related to the coconut, comprising about 200 genera and 200 species, are natives of America, witli the possi- ble excei)tion of a single species, the West African oil palm. The structure af the fruit, contrary to a long standing assumption, does not indicate adaptations for maritime distribution, but rather for ])rotecting tlie embryo, assisting in germination, and establishing the young plants in dry interior localities. The habits of the coconut palm atTord no indication that its original habitat was on the seacoast, and in fact it does not appear to be able to sustain itself under littoral conditions without the assistance of man. It has not been able to establish itself as a wild plant on any tropical coast, but is always crowded out by other vegetation after human care is withdrawn. The rela- tive uniformitv of the coconuts of America is in accord with the probabilitv of an origin in this hemisphere. The discovery of distinct varities in isolated localities accords with the probali- tics lliat llie many di\erse varities in the ^lalay region, for ex- ample, have arisen like other cultivated varities, through segre- gation and mutation rather than by gradual evolution and natural selection. It seems therefore "that the botanical n)mance of the coconut, ])rotected by its thick husk and lloated from island to island in advance of human habitation, nuist go ihc \\a\- of man\- other ]jleasing traditions," and that the oj^n- i(,n of Pe Candolle, based on such evidence as he could obtain, that the c )C.)niit palm was introduced into South America and tilt- \Vc•^t Indies ])\- luiropean settlers has no warrant in historw Teachers will find much useful information in Farmers' Bulletin 428 on Testing l-'arm Seeds in the Home and in the Rural School, while Bulletin 431 of the same series, on the Pea- l52 The Plant World. nat, well illustrated and well written, is also filled with a va- riety of valuable data which could hardlv he found elsewhere in such convenient and accessible form. I'liese and still other bulletins of the Agricultiual Department are accessible practically to every citizen of the I'nited States who cares to make use of them. The great service thus rendered to education by the Department, quite apart from its immediate function of supply- ing farmers and horticulturists with practical information, is not likely to be overestimated. We are in recei]3t of the first numlier of tlie f'oniona College Journal of Econowic Botany, a quarterly which has for its aim the advancement of sub- tropical horticulture and a;,^riculture. The editor, Mr. C. F. Baker, is a man of long experience in the tropics, and the spirit of his 'Foreword' 'in the opening pages of the journal, together with the character of its contents, would indicate that it will merit a lieartv support. The address of tlie editor is Claremont, Cal , the subscription is r'l.no. lujlLllHARY Volume U X^^^ ■% K Number 7 The Plant World A Maoazine ok General Botany JULY, 1911 THE RELATION OF THE OSMOTIC PRESSURE OF THE CELL SAP IX PLANTS TO ARID HABITATS. Burton Edwvkd Livingsto:v. Plant physiology and the various fields of its application are indebted to Hans Fitting * for the first extensive study of internal osmotic pressure as a plant character ecologically re- lated to environmental conditions. Although numerous deter- minations of the magnitude of the osmotic pressure in plant cells, both by the method of plasmolysis and by that of the freezing point, have already been carried out, these have dealt with comparativelv few plants and with restricted ranges of condi- tions. From the hitherto available information, the usual pressure in the cells of the ordinary land and fresh-water plants may be taken as from 5 to 1 1 atmospheres (Pfeffer-Ewart 1 : 139), but cases are on record of pressures much outside of these limits. So far as I am aware, the highest pressure hitherto observed in ordinary plants is that of 40 atmospheres, found by Pfeller in the internodes of grasses (citation in Jost-Gibson, p. 419). In a very thorough-going study of the osomtic pressures ocurring in the foliage of a large number of plant forms growing naturally in the vicintyof Biskra, Algiers, Fitting finds that the pressure of the cell sap may often reach magnitudes very much higher than those mentioned above. In this study,' the leaf epidermis, or sections of mesophyll — always from leaves gathered in the forenoon of the same day — were tested plasmolytically ♦Fitting, Hans, Die Wasserversorgung und die osmotischen Druckvcrhalnisse der Wiistenpflanzen. Zeitsclir. f. Bot. 3: 209-75. 1911. 154 The Plant World with potassium nitrate solution in the usual manner. The solu- bility of potassium nitrate limits the possible osmotic pressure of an aqueous solution of this salt to about 100 atmospheres * and it ^vas found impossible in many cases to obtain plasmoly- sis with the saturated solution. In certain of these cases a saturated solution of sodium choloride, containing 5.42 gram- molecules per liter, produced plasmolysis. I As many plants as possible, from a number of different soils, were tested to determine the influence of the latter (espec- ially in regard to their moisture content) upon the magnitude of the foliar osmotic pressure. In many instances it was possi- ble to test the same species on several soils. The main soil types considered were: The mountain desert (Felsen- Wiiste) of the Chaine de Sfa, the boulder desert (Gerollwiiste) , dry soil, formerly cultivated but now abandoned (trockenes, wiistenahnliches Kulturland), sand dunes, saline swamps and moist, non-saline soil (either irrigated of near water in the Oued Biskra. The results obtained are so important, not only with regard to the possible magnitudes of plant osmotic pressure, but also with reference to the relation of this pressure to environmental conditions, and to our general knowledge of the fundamental water relations of plants, that I have selected from Fitting's tables a few of the observed pressures for pre- sentation here. The e are given below, the quantities being all in terms of gram-molecules of potassium nitrate per liter,** and all referring to the leaf epidermis. In many cases the mesophyll was found to exhibit a somewhat higher pressure than the epidermis. In the mountain desert and in the boulder desert the conditions, both of plant and sziil are in close agree- ment, so that I have not deemed it worth while to quote separate examples for these two soil types. For such details, as well as for determinations upon many more forms, the reader must consult the original paper. ♦The most concentrated solution used by Fitting was saturated at 22o C, and contains 2. "50 gram-molecules per liter. This concentration is assumed as 3-normal. with a pressure of about 100 atmosphetcs. tThis method of using as a basis for dilution a solution saturated at a given tempera- ture. avoiJiug .as it does the use of the balance, has much to reccommend it for field studies which require the preparapration of salt solutions. There is no advantage in haying the stock solutions, from which dilutions are to be made, of any integral number of gram- mo'ecules per hter. * *These may be reduced, approximately, to atmospheres by multiph-ing by 36.9, 34.07, or 33.3. according as the obser\-ed isotonic solution approaches respectively! 1.0, 2.0, oi 3.0 gram-molecules per liter ^see original paper). Osmotic Pressure in Plan'Ts. 155 Mount' in or Dry soil, Sand M.OIS T SOIL rUAXTS. boulder formerly dunes Saline Non- desert culliv't'd saline Trees Phoenix dadylifera 1.2-1.5 0.8-1.2 Large Bushes, Sitrarii fridenfafa 1.2 1.2 0.8-1.2 Rhus OX} rant ha 3.0 + 1.5-2.0 7i:yphus lotus 1.0-1.2 0.5-0.6 Small Bushes. Suaeda vermiculaia 3.0+ 2.0 3.0+ 3.0^ Suaeda pruino^a 3.0 + 3.0-3.0 + 3.0+ 1-5 Tra ga n u m n udatii m 3.0 + 1 0-1.2 Zy-Qophyllum cornutum 1.2-2.0 + 1 . .5-3 . 0 1.2-2.0 OpunHa 0.4-0.5 Perennials, Fran' en ia th\ mi folia 3.0 + 1 . 5-3 . C 0.8-1.5 0.8 Faqonia qluiinosa 0.9-3.0 + 0.2-0. 3 Annuals, Adonis microcar! a 1 0-1.2 0.8-1.2 1.0-1.2 0.5-0.8 Anagallis coerulea 0.3-0 -S 0.3-0.4 C'.eome arahi a 0.8-1.0 0 . 4-0 . 6 0.4-0.5 hi esemhtinnlh. mum ao'ifluium 3.0 + 1.0-1.2 1.0-1.2 Wheat 0 6-0.8 If we compare the isotonic concentrations determined by Fitting with those which are usual with ordinary plants in humid regions (0.15-0.3 gram molecules of potassium nitrate per liter), we find that the hi\jhest pressure developed by those desert forms is more than thirteen times what we have hitherto considered as usua/. They are perhaps three times as great as the pressure observed in grass stems by Pfeffer. Here- after the highest pressures observed for ordinary green plants must be cited as at least over 100, perhaps as high as 130 atmos- pheres, or even higher. By the use of other solutes — perhaps cane sugar is the most promising — it should be possible to de- termine these high pressures more accurately. It is to be noted especially that not all forms growing under the most arid conditions are capable of exhibiting these enor- mous pressures; Anagillis coerulea, for example, even in the driest situations, fails to develop pressures above that of a half- normal potassium nitrate solution. Tests by taste show that manv, but not all, of the plants which exhibit great pressure are highly charged with sodium chloride. Some have an acid 156 The Plant World. ^ taste, but it is clear that high osmotic pressure is not necessarilly correlated with the presence of sodium chloride nor with acidity. To determie the nature of the solutes to which the osmotic pressure is due must remain a problem for the laboratory, not for the field. Turning our attention now to the influence of the sub- stratum upon the magnitude of the foliar pressure, it appears that the highest pressures are usually manifest in plants grow- ing in dry soil, and that extremely high pressures are not met wnth in moist, non-saline soils. The pressures exhibited by the plants growing in irrigated land are, however, usually somewhat higher than those met with in the humid regions. In this connection Fitting calls attention to Stange's experiments with water cultures, *which showed that with nutrient solutions of high concentration the osmotic pressure of leaves and roots is much higher than otherwise. Thus non-halophytes like wheat, bean, pea, etc., (which in weak solutions or on ordinary moist soil have pressures about isosmotic with a 0.25 normal solution of potassium nitrate) develop pressures about equivalent to that of a 0 6 normal solution when grown in concentrated liquid media or saline soil. Salt-accumulating forms, such as Plantago maritima, Sa/sola kali, etc., (usual pressure, in non- saline soil, about equivalent to that of 0.25 normal sodium chloride solution) exhibit pressures about isosmotic with a 0.76 normal solution of the salt, of even higher, when grown in con- centrated media. The irrigated soil of Biskra is much more highly charged with salts than the cultivated soils of the humid regions, and our author believes that this fact accounts for the occurrence of rather high pressures in the fields of the des- ert oasis. While wheat has a usual pressure balancing about 0.25 normal potassium nitrate solution, and Stange succeeded (through the use of a concentrated substratum) in increasing this to that of a 0.6 normal solution, the pressure of this plant as grown at Biskra is found by Fitting to be equivalent to that of a 0.6 to 0.8 normal solution of the same salt. It is i .ter- esting to note, as does Fittin^, that the litt'e annual AnagaUis coerulea exhibits pressures little if at all higher in the most ♦Stange, B., Beziehungen zwischen Substratkonzentration, Turgor iind Wachstum bci einigen phanerogamen Pflanzen, Bot. Zeitg, 50. 253. 1892. Osmotic Pressure in Plants. 157 arid conditions than on the irri,<(ated land. It barely succeeds at all in extremely dry soil. \'ariations in the moisture supply appear not to produce any corresponding alterations iu the foliar pressure of this i)lant. The pressures found in plants upon the dry cultivated land are much higher than those upon irrigated soil, and closely approach, or actually attain, the magnitudes obtained with plants from the true desert. That Opuntia is found at Biskra only in irrigated land makes it appear that tliis form is unable to succeed under the natural conditions of this locality. Like Angallis, this cactus was not found with high pressures, but, as noted, Anaqallis is able to grow, to some extent at least, in very dry situations. The Opuntias tested by Fitting were shrivelled and apparently not in good condition, from lack of nijisture. Fitting calls attention to the fact that the very low concentration of the cell sap (isotonic with 0.4 to 0,5 normal potassium nitrate) exhibited bv his Opuntias is in excellent agreement with the results ob- tained bv myself (Publication .50 of the Carnegie Institution, 1906) at Tucson, for another species of this same genus, as well as for other succulent cacti. MacDougal (Publication 129 of the Carnegie Institution, 1910) has had the osmotic pressures of the expressed juices of Opuntia and other cacti determined bv the f reezin ,^ point method, with the result that, though the pressure was found to increase considerably with the dr-.ness of the season, yet the tests yielded no very high magnitudes. The xerophvtism of this sort of plants is then, not correlated with high osmotic concentration (jf the cell sap. Fitting emha- sises the fact that these succulent cacti are not to be considered as tvpes of extreme xerphytes. Onlv three plants were tested for both irrigated (non- saline) soil and that of wet salt spots. One of these {Mesem- bryanthemiim) showed the same pressure in both situations, while the others {Phoenix and Fr(i)ikctiii) showed a considerably lower pressure in the irrigated, soil. The couse of the lower pressure in the last two cases is considered as related to the greater lesistance to water absorption produced by the high concentration of the salt, swamp water, that is, to external osmotic pressure. Thus high osmotic pressure of the soil solu- 158 The Plant World tion is seen to affect the organism in the same manner as does actual dr}ness of the soil. Several salt-accumulating forms, growing in wet salt-spots showed pressures equivalent to that of an 0.8 to 1.5 normal solution of potassium nitrate, while the same forms in the much less saline and at the same time much drier desert soil exhibited preystircs isotonic with a 1.5 to 3.0 normal solution. "Thus the pressure is the higjiest, not where salt may be most easily accumulated, but rather in the driest positions, where salt is nmch less easily available.'' (p. 249). This must not Ije taken to mean (a point which our author does not mention) that actual dryness is more potent in increas- ing the pressure of the call-sap than v:, that form of physiological dryness which is due to high concentration of the soil solution ; it seems to denote simply that the magnitude of physiological dryness in the saline swamps does not equal that of the actual dryness in the desert soil. If it were possible to obtain a non- toxic solution sufiliciently concentrated, we might, on physical grounds, expect to obtain the same sort of response it plants growing therein as occurs in the nearl}- dry, non-saline soil. Forms in which sodium cholride does not accumulate thrive likewise in the salt swamps, a good example being the date palm {Phoenix), which there develops nuich higher pressure than in the non- saline irrigated land. Uur author brings out clearly the point (of which I was long ago convinced by superficial observations on the dunes of Lake Michigan) that the sand dune is to be considered as a relatively moist substratum. The dunes of Biskra possess a more luxriant vegetation than that of the surrounding deiert and upon them occur, together with generally distributed species many forms which are rare or wanting elsewhere. I have re- peatedly made a similar observation on the sand dunes of the Salton Basin (^California), a region which seems quite closely to resemble that of Biskra. I have also noted that generally distributed desert plants often attain a more luxriant growth upon some of these Salton dunes than upon the stony loam of the basin floor. * *It must be remarked in this connection that such detert dunes sometimes owe their origin to springs or moist soil. In such cases the blowing sand is more or less permanently Osmotic Pressure in Plants. 159 Many of the dune plants tested by Fitting possessed an osmotic pressure markedly lower than that of the same forms in the mountains and boulder desert. Iwtting concludes, ■'The lower pressure upon the sand seems to indicate that ths water suppl\- in the sand is less limited than in other dry desert soils."' (]). 2.^1). He also calls attention to the low resistance offered by sand to abso&ption by roots, and cites the rapid downward penetration of rainwater in such soil and to the possi!)ility of extensive root growth therein. Fitting repeatedly asserts that the power to develop such high pressures as he has demonstrated is a purposeful adapta- tion for living in dry soils! * In phvsical terms, ij wc assume that the movement of water from soil to plant depends upon the gradient of diffiusion ten- sion which exists between the soil films, on the one hand, anJ the solutions within the roots, on the other; it follows that the lower the internal diffusion tension, the drier will be the soil wdien e:iuilibrium is reached. \'apor pressure is proportional to diffusion tension (is, indeed, a special case of this) and we have merely to consider that the vapor pressure of the internal solu- tions decreases as their osmotic concentration rises, while the vapor tension of the soil moisture films decreases rapidly as as tlie films becomes more tenuous. Thus we have an attrac- ti( n (f the cell sap of roots, for water, opposed by an attrac- tion of the s:)il, the former force depending upon the osmotic c oncentration of the sap and the latter upon the thickness and arrangement, as well as upon the osmotic concentra- tion ff the soil moisture films. It is from these con- arrested by being moistened and thus a dtinc is built up. (See MacDougal. I). T., Publi cation Of of the Carnegie Institution. 19()S. p. .^O) Such a dune may attain a hcii^ht of sev era! miters, being miinly held in place by stem? and roots of thrifty plants, which derive moisture from below and suggest to the eye the presence of a continuous supply of water. Dunes of this sort, well covered with vcgct^'.tion. often occur where the sf)il is apt to be moi^t for the longest perio:Is. as along the niargin of an out cropping drainage stratum, and the accumulated sand shouUl act as a very perfect mulch to conserve the natural soil mois ture of such localities. Tnus.tho more vigorous plant growth here m ly be largalv due to the sand mulch \\'hethor or not th^se considerations may have any bearing upo.n the nature of the dunes and dune vegetation in the vicinity of Biskra I am unable to surmise. That th?re are out croppi ig drainage strata in that vinicity is clear from the existence of the original ori. itse'.f. the spring; of Hammam Salahin. etc. *''.Manwird dice Befahgung als jiussert zweckmassig betr.ichten miissen, um auf : ehr trockcnem Ho ien gedeihen zu. koanen." (p246) To m\- mind nothing at all is gained and the general muddle of ecology is greatly augumented by such methods af statemeat It were fully as well to anthropomorphose the soil as well as the plant, and to hold that extreme dryness is a svtl adaptation by which the Sahara soil better succeeds in preserving itself largely untrammelled by vegetation! 160 The Plant World. siderations (p. 218) that Fitting formulated the experimental project which he has so he successfully carried out. The supposition that high pressures in the leaves indi- cate correspondingly great powers of absorption from dry soils it the form in w'hich it is advanced by our author, depends iipon the assumption that these pressures are accompanied by similar- ly hiqh pressures in the root cells (which has been rendered highlv probable by Stange — loc. cil. — -,h\\i \\hich needs more thorough study) and also upon the assumption that the entrance of ivatcr into the root is a function of the osmotic-capillary or osmotic-adsorption relation described in the last paragraph. This last assumption is by no means an established fact; we know as vet practically nothing of the energy relations of w-ater a' sorption from non-saturated soils, and the work of Dixon on tlie tensile strength of minute water columns '^ renders it apparentlv possible that "osmotic pressure does not indeed play the important part in water absorption which has hitherto been assigned to it. ' ' * This one of the two alternatives i)re- sented bv mv experiments with soil-osmometers meets with no approval from Fitting (p. 219). I must, however, remain undecided in regard to this whole question of the physics of root absorption till more quantitative information is at hand (the question will be referred to again below), but agree thor- ouglilv with Fitting that "this question can be answered by the research-methods of physical chemistry" (p. 219), and that the osmometer method described in Publication 50 "might have been replaced by a better" (p. 220). But, after several years if experimental contact with this problem of the resistance offered b\ the soil to root absorption, 1 am unable to agree wath him that a satisfactory method may be attained "without difficulty '("wohl unschwer, " p. 220). This is perhaps the most important problem that confronts the plant physicist todav, and is well worthy of careful study. One rather fundamental aspect of the relation between soil and roots, at least so far as my own studies in this connection have led me, is one that seems completely to have es- *Sum;naii'y prpsenlcd in this p;ipcr, "Transpiration and the Ascent of Sap," Prog. Rei. Bot. 3: 1-66. 1900. tPub'iitation 50 of the Carnegie Institution, 1906, p. 21. Osmotic Pressi'Re in Plants. 161 caped the notice of our author. Whatever may be the nature of the forces which determine whether or not water will migrate into root cells from an adjacent layer of nearly dry soil, the Duiintenance of sucli mo\ement must depend, not merely on the initial gradient of the forces involved, but upon the relation between the rate of removal of moisture from the absording cell membranes into the plant interior and the possi- ble rate of water movement through the soil. Thus, if the con- ditions were such (as they must often be in arid regions) that moisture were more rapidly absorbed from the soil laver im- mediatelv adjacent to the absorbing cells than the soil condi- tions would allow it to be replaced from more remote layers, it is obvious that the absorbing surfaces of the plant must soon become surrounded by a layer of soil too dr>' to give up any more moisture. Thus absorption would be checked, although there might be large amounts of water in the soil as a whole. The possible rate of moisture movement through the soil and the relations of this rate to the physical properties of the latter must ever be an important factor in the control of plant absorp- tion from nearly-dry soils. At several points in the paper Fitting expresses the idea though it is nowhere strongly emphasized, that a high osmotic concentraticn of the foliar cell sap must act directly to retard transpiration. This must be undoubtedly true, on physico- chemical grounds, but the amount of such retardation cannot be large enough to exercise a primary, or even a great, intiu- ence upon the success or failure of plant forms. I have else- where * discussed certain aspects of this question, and shall reserve its fuller consideration for a future paper, but may state here that a solution of the strength of the highest concentra- tions found by Fitting in the foliar cell sap of desert plants (something over 100 atsmospheres of osmotic pressure) pos- sesses a vapor tension less than 10 '-/c below that of pure water, and should therefore evaporate more than 90 % as rapidly. It is thiis clear that no great ecological importance is to be attributed directly to the checking of water loss by low vapor tension of the foliar solutions. f What may be the indi- ♦Livingston, B. E., "Relation of the Daily March of Transpiration to Variations in the Water Content of Foliage Leaves." Bot. Gaz. In press. tThis has been clearly showa by Drabble and Drabble, for a humid region. See Drab- ble, E. and Drabble, H., The relation between the osmotic strength of cell sap in plants and their physical environment. Bio-chem. Jour. 2: 117-132. 1907. 162 The Plant World reel effects of such high concentrations as Fitting has demon- stiated need not be considered here. The very moderate lowering (about 10 %) of the vapor tension in the presence of enough solute to yield an os- motic pressure of 100 oi more atmospheres renders it improbable that the concentration of the cell sap of roots should play a direct role in determining the lower limit of available soil mois- ture. When the roots are bathed in a solution ( as in the case of the salt swamps'), and not merely wetted by imbibed or ad- sorbed moisture (covered by a capillary film), then the internal osmotic pressure should be directly opposed to the pressure of the surrounding solution, and it seems quite possible that high sap concentration may accelerate water entrance. At any rate, such osmotic pressures in submerged roots must play an important role in maintaining cell turgidity, which appears to be very necessary for root absorption. Until more is known of the quantitative relations between the energy of surface tension, imbibition, etc., and that of vapor tension and osmotic pressure, as these forms of energy are manifest in the plant and its en\ironment, the whole problem here touched upon must rest in abeyance. An interesting suggestion is made by Fitting (p. 257-8) to the eftect that transpiration water in certain desert forms may possibly, during the driest seasons of the year, be derived from the decomposition of carbohydrates, etc., through the pro- cess of respiration. I am not aware that this has ever been suggested before, and the idea seems well worthy of an investi- tion. It is thus rendered paradoxically possible that there may sometimes occur a continuous loss of water from an organ or tissue, which, upon being tested, exhibits almost none of this liquid and which receives no moisture from without! Our author supf oses that this consideraiton may apply to forms which possess accumulated carbohydrates, as in tubers and enlarged roots. Fitting's statement (p. 2L5) that "from a purely physical standpoint, all the hinderances to water supply in a saline soil seem to be overcome when the plants growing therein, by an increased cell sap concentration, maintain a concentration Osmotic Pressure in Pi, ants. 163 gradient corresponding to that in a non-saline soil, ' ' seems to apply only to saline soils whose solutes are not to tic to the plants. Of course a chemically poisonous substance existing in the soil in comparatively low concentration may produce apparently the same effect upon plants growing therein (dwarfing, loss of leaves with increasing eva orating power of the air or with increasing sunshine intensitv, etc.,) as does a nontoxic salt at a much higher concentration. * As 1 have long since pointed out, j the stimulating effect produced by the toxic materials of an unproductive soil upon plants growing therein seems to be primarily due to a more or less complete inhibition of the formation of laterals and an early senescence of the primaiy roots, rendering them very poor absorbers of water. Such phenomena probably occur also in the acid humus soils t which, since Schimper's time, have been called ''physiologically dry."' These considerations, while not of the quantitative nature which Fitting quite right- ly desires as a basis for our theory of physiological aridity, do, it seems to me, render the general problem somewhat clearer than our author's sentences would indicate. There are appar- ently two very distinct kinds of physiologically dry substrata. In one of these the resistance to water absorption by plants is due simph to a high osmotic concentration of the soil solution,^ With this form Fitting has had to deal in his work upon the Biskra salt-spots. In the second kind, the osmotic pressure of the soil solution is not markedly higher (indeed it is sometimes actually somewhat lower* •=)than that in non-arid soils, but there are here present small amounts of chemically toxic materials. In the presence of these substances root development is mark- edly abnormal and the abnormal root structures may hinder the en- trance of water from the soil. Thus, we may conclude that in the first variety of physiologically arid soils the hindrance to water *The reader may refer, for examples, to the interest'ng papers of Kand^ and of Jen- sen upon the toxir limit'; for plant activity in regard to salts of copper, zi"c, nickel, etc in the soil: — Kanda M .Stiidieniiber die Reizwirkung einiger Metallsalze auf dasWachatum hjherer Pflanzen. Jour. Coll Sci Imo. Univ Tokyo 11: Article 1.?, pp. 1-37 1904 Jen- sen. G. H , Toxic limits and sti.mulation effects of some salts and poisons on wheat Bot Gaz. 43: 11-44. 1907. tLivingston, B. E., Note on the relation between growth of roots and tops in wheat Bot. Gaz 41 139-143. 1906. See also Schreiner, O , Some effects of a harmful organic soil constituent. Bot. Gaz. 50: 161-181. 1910. tTivingston. B. E., Physiological propreties of bog water, Bot. Gaz, 39 :348-3 55. 1905. Dachnowski A , Phvsiologi-^a'.ly arid habitats and drougth resistance in plants. Bot Gaz 325-339. 1910. * *Livini{ston. B. E.. Physical properties of bog water. Bot. Gaz., 37: 383-385. 1904 164 The Plant World entrance is due to lack of the resquite osmotic gradient, while in the second it is probably due to properties of the absorbing surfaces or osmotic membranes, the resquisite gradient, how- ever, being present. Numerous fundamentally important considerations in Fit- ting's highly admirable, though somewhat loosely presented, researches, have received no mention at all in the present paper; whoever is interested in the water relations of plants must study the original, the author of which is to be congratulated upon the success and thoroughness with which he has carried out, under rather difficult conditions, what will long remain a fundamental pioneer research not only for desert ecology but also for ecology in general and for scientific agriculture. The Johns Ho(^\ins Uiihersiiy. vSTUDIES IN SOIL PHYSICS, IV. * The Physical Constants of Soils. E. E. Free. Soil science has begun its introduction to the quantitative, and its votaries are newly but rapidly learning to"observe"a lit tie less and to measure a little more and a little more accurately. It is a much needed change — one of great promise and already of some fiuition, but perhaps its greatest service has been to call attention to the weaknesses of present methods and the in- adequacy of present tools. There are so few measurements that can be applied to problems of the soil. In soil physics, for in- stance, we are accustomed to refer the various physical behav- iors of the soil to a hypothetical "physical nature" or "physi- cal character" which is supposed to be fundamental and causal of all more superfical properties and behaviors. Whether we call this physical character the "nature and numbers of the constituent particles' ' or whether we define it more exactly (and less luminously) as the expression of the possible ranges of variation of all the physical properties, or whether we shirk *Publishcd by permission of the Secretary of Agriculture. Studies in Sou. Piiysics, IV. 165 defiinition altogether, is unimportant. Physical character remains something which cannot be measured directly and which we must examine, if we examine it at all, by devious and indirect paths. Nevertheless some quantitative express- sion or indication of physical character seems quite necessary to further advance of the science. The actual, momentary phvsical condition of a soil is indeed susceptible of some quantitative examination and perhaps of sufficiently accurate measurement, but this does not touch the core of the matter. It is necessary to know, not what the soil is temporarily like, but what it can belike — not its exhibited properties but its potential properties. Within limits physical condition is un- der human control; physical character is very seldom so, and it is phvsical character that we most need to learn to know. This iG— phvsically — the fundamental property of soils. But physical character is not even accurately decipher- able let alone measurable. It is probably far too complex ever to be measured by one process or in one unit. We must fall back upon a subterfuge. If we cannot measure ths thin^ itself we must select something dependent upon it and measure that. We want some measurement which will indicate, if it does not completly express, the more fundamental physical character. The electrical engineer has certain curves which express the behavior and cabapilities of a dynamo, Avhich curves he calls the "characteristics" cf the machine. We want a physical "characteristic" of the soil. I have spoken, and shall speak, of this "characteristic" as a "physical constant"for it must bear a constant relation to physical character and must be, for any one soil, fully constant and reproducible. Of the qualities \\ hich must be possessed by this constant the first is simply this constancy of relation to the ultimate physical character of the soil, regardless cf the condition it may happen to be in at the moment. Our constant must not be affected, for instance, by accidental variations in the treat- ment of the sample or by its recent history. Secondly, the constant must vary closely and in rigid correspondence v^ith changes in the physical character and its variations must be of sufficient magnitude to enable the detection, through them, of important differences in this physical character. Thirdly the 166 The Plant World. constant must be measurable with fair ease and accuracy. If the constant be numerically simple and if its relations to other physical properties and to the physical character be rational ones, so much the better. If, however, numerical complexity cannot be avoided and if the needed correlations must neces- sarily be obtained empirically, we must needs make the best of it, and the fault will not be fatal. vSuch a constant would be of incalulable value not only in purely scientific soil investigation, but also in practical agri- culture. It would place the classification and comparison of soils on a far better basis than any now available, and it is not too much to hope that correlations might be obtained with fertility itself, at least in so far as this very complex quantity is related to the physical nature of the soil and to its physical properties. This need has not gone unappreciated. There have been many and various suggestions of possible physical constants, and in particular the mechanical analysis has been much used and has been long enjoyed (wrongly, as I believe) some reputa- tion for adequacy. Mechanical Analysis. This mechanical analysis, and the mechanical composition which it appropriately expresses, have been discussed in the first paper of this series and need not now be reviewed. Nor need anything be said concerning the various methods used or suggested for the separation of the soil particles into groups of the various sizes or concerning the difi"erent systems of limits between these groups. * For de- tails on these matters the reader is referred to the textbooks of agricultural analysis. The merits and demerits of the mechan- ical analysis as a soil constant depend upon inherent character- istics which have little or nothing to do with the details of ma- nipulation or the form of the results. And, as I expect to be critical, let me say first that mechanical analysis is by no means useless nor to be belittled as a means of soil investiga- tion. It has been much used and, on the whole, pretty success- fully, and we now are in possession of man}' thousand analyses and of at least some beginnings toward correlations with the phy- sical properties observed in the field. But it can hardly be con- sidered as fully satisfying the requirements which we have seen ♦Studies in Soil Physics I, Plant World, 14: 31. 1911. Stidies in Soil. Physics, IV. 167 to be essential for the needed constant, and the sooner we cease believing that it does, and begin to examine critically its use- fuhiessesand its limitations, the sooner shall we be able, not only to find a better constant,hut to attain to a rational use of the mechanical analysis itself. In the fisrt place it must be remembered that the whole business is purely empirical. The mechanical composition of a soil doubtless determines its physical properties but the laws according to which the determination is affected are still un- known and quantitative correlations, if they exist, remain imdiscovered. We can do no more than to examine the external properties of soils and determine the corresponding mechani- cal analyses in order that, by the gradual accumulation of such comparative data, we can come more and more to say that a soil of a certain mechanical analysis will probably possess certain properties — which properties we have learned b y e x- perience usually belong to soils giving that, or nearly that, analysis. However, this empirical character of the process is un- fortunate mainly because it makes impossible exterpolation or wide interpolation and hence requires that over the whole field of possible mechanical compositions correlations with observed properties be obtained by actual experiment. Except for the extra labor thus required it makes no great difference whether the process and its correlations be empirical or not. The correlations of phosphorous content with breaking strength in steels are useful enough for all that they are empirical. The main trouble with mechanical analysis and the main reasonwhy it can never be satisfactory as a physical soil constant lies in the complexity of the final ' 'constant" to which it leads. The mechanical analysis must be expressed as a series of unrelated quantities — the percentages of the particles in the various groups. It can never be expressed in any one unit but must always refer to several — one for each group in the series. And there is no common denominator. It is impossi- ble, for instance, to arrange soils in the "order of their mechani- cal composition ' ' as one would arrange minerals in the order of their specific gravity or wires in order of their electrical conductivitv. This makes mechanical analvsis a verv hard 168 The Plant World. thing to think with. The mind must not carry one quantity but several and compare them jointly and severally (but all at the same time)with that external property whose correlation with mechanical composition is being sought. The requisite degree of mental dexterity is not common. Furthermore the lack of unity in the expression of mechanical analysis precludes the application to it of curves and of graphic methods generally — a loss, the great proportions of which can be partially appreciated by recalling the immense service which these methods have rendered in other branches of physical science. Closely related to this fault of disunity in expression is the error introduced by the fact that the particles within the limits of any one of the size groups are necessarily lumped together in the result. From the mechanical analysis we learn merely that so much material is within the size limits of a given group. We do not know whether the particles comprising it are of sizes mainly near the upper limit or are mainly near the lower, or whether they are more or less uniformly distributed among the intermediate sizes. W^ith finer soils this error is of great practical importance. For instance, according to the usual American system, all particle 3 below .005mm. in diameter are classed as ' ' clay ' ' though in one soil this ' ' clay ' ' may consist mainly of particles just inside the limit, (say .002 mm. to .004 mm. in diameter) while in another it is composed largely of particles so small as to approach the colloidal state. The physical properties of two such soils are radically different but their mechanical analyses are exactly the same so long as the same quantity of material lies below the .005 mm. limit. Exactly this case is of such frequent occurrence in pracf.ce that various attempts have been made to devise methods for the determination of the ' 'colloidal clay" as an adjunct to the ordi- nary mechanical analysis. These methods have not been particularly successful, but even if they were the solution of the difficulty would be but partial. It would amount to no more than the addition to our present system of size limits of another one below our present lowest. Within the new groups thus established the difficulty would be nearly as great as be- fore, and the slight improvement in accuracy which might be Studies in Soil Physics, IV. 169 expected to ensue would be attained at the cost of an additional operation (and a very troublesome one) with a consequent in- crease in time and labor expended. The error could be made insignificant only by the employment of a very large number of groups and the determination of the amounts of material lying within each. Obviously, such a large number of groups means a multiplicity of analytical operations and an expensive and laborous method. Any system of analysis with few enough groups to be ])racticable is going to give at best onh a somewhat rough approximation of the real mechanical com]:»osition. Fur- thermore,in the place where the greatest practical errors occur, namely in the finer particles, our laboratory methods for the separations of are hardly accurate enough for any greatlv closer spacing of the limits and these methods are probably not susceptible of much improvement. Our present svstems of mechanical analysis are about as good as we can hope to get.* There is still a third major error in the mechanical analysis, that introduced by the variations in the shapes of the soil par- ticles. Shape and degree of roughness have various effects upon the physical properties and still other and unrelated effects upon the mechanical analysis. Indeed, since some of the group separations are made by sieving, and some bv water elutriation, the shape effects will be different on the different groups of the same sample. Ordinarily, perhaps, these shape effects are not particularly important .since soil particles are usually roughly spherical in form and of about the same shape- character in all ST^ils. But in special cases the error is by no ne,.;ligible. A very micaceous soil, for instance, has very different jdiysical properties from one of the same mechanical anahsis bnt composed of particles which are mainlv spheres insteads cf disks. These three errors of the mechanical analysis are all incor- rigible. They may be denoted as (1) disunity of expression; (2) failure to express conditions A\ithin the limits of the indi- vidual groups; and (3) failure to take account of variations in the shapes of the particles. All are inhe ent in the nature f f the process and if we are to use at all tlie mechanical analysis ♦Unless air elutriation for clays can be rendersd practicable, and this seems very unlikely . 170 The Plant World. as a soil "constant" it will be in spite of these errors and not because they have been removed. In the process as at present conducted there are indeed other errors: the failure to take account of the permanent and semi-permanent flocculations; the errors caused by organic matter and by dissolved salts; the variations caused by the diflerent methods of sieving and of elutriation, etc. But these errors are not inherent. They can probably Ije removed if it seems useful to dj so. The three previously discussed are the crucial ones, and if mechan- ical analysis is ever replaced by something else it will be on their account. The Siujace Constant'^. Of course these imperfections of the mechanical analysis have not been suddenly and recently discovered. They have long been appreciated and manv sugges- tions have been made looking toward their avoidance or the substitution of another and more satisfactory physical constant. First of these, chronologically, was probably the suggestion to use as such a constant the total amount of surface of all the particles in a certain weight (or volume) of soil. Indeed it was early suggested that the internal surface (as this is called) might be determined from the mechanical analysis itself and that the inconveniences due to the disunity of expression of the latter might thus be climated. If the mechanical anahsis were reduced to, or expressed as, a surface it coidd be expressed in one unit. Unfortunately, however, the lack of knowledge of conditions within the group limits and of the shapes of the par- ticles make it impossible successfully to determine the internal surface of the soil from the mechanical analysis and if this sur- face is to be used as a constant it must be otherwise measured. Direct measurement being obviously out of the question, it is necessary to find something dependent on the surface and to measure that. This something has been found in the heat of wetting. When a dry powder is placed in water a considerable quan- tity of heat is evolved and the quantity of this heat vaiies direc- tly with the total internal surface of the powder and probably in close proportionality thereto. ='' This fact, long known to * For the purelv phvsical side of this problem and for references to the literature see Patten, — Trans. Amer. Electrochem, Soc. 11; 387-407 (1907) Studies in Soil Physics, IV. 171 physicists, has been applied by Mitsclierlich to the soil. Using a Bunsen ice calorimeter and very ingenious devices for intro- ducing and wetting the dried soil he is able to obtain values which are concordant and reproducible for any one soil and which vary from soil to soil with variations in the physical character. Of course the correlation of the heat of wetting with the general physical properties is just as empirical as was the correlation of the mechanical analysis therewith, but this as before is comparatively unimportant. The heat of wetting is a single quantity expressible in a single unit; it is free from the shape error and the group error that beset the mechanical analysis; and it is probably closely and rigidly related to the fundamnetal physical character(as distinguished from ])hysical condition) of the soil. As a soil constant however, it is open to two errors; (i) the elTects due to tlie heats of solution and dilution of the soluble material present in the soil; and (2) the effects of the organic residues, largely the remains of plants. The former is probably unimportant. In all ordinary soils the soluble salts are so small in total quantity and so nearly the same in nature and amount that their effect on the heat of wetting is probably almost constant, especially if the same relative amounts of soil and water be employed in each case. The effect of theor- gani: material , is less easilypredicted. They may behave similarly to the inorganic materials, or they may not. They are known to effect both the general physical behavior of the soil and the heat of wetting. If they affect both in the same way and ratio, the exact forms of the relations are unimportant — the heat of w etting is nevertheless a true representation of physical character. If the effects on physical character and on heat of wetting are diverse the latter will fail to properly indicate the former when much organic matter is present. More complete eluci- dation of this matter must aw ait further experiment. In any event the heat of wetting seems to ofi'er much promise as a substitute for, complement to, mechanical analysis, and it has actually been so used by Mitscherlich and his co-workers, apparently with satisfactory results. *ror details see his Bodenkunde fiii Land und Forstwirte. 1905. P. 51-70 172 The Pi. ant World. Besides the heat of wetting there have been proposed two methods of measuring the internal surface of the soil. One of these is the measurement of the amount of a given dye d- sorbed from solution by a given quantity of soil. This has proven of some utility in the classification of fine clays for porcelain manufacture and similar uses. Otherwise it has never been, nor is likely to be, of any importance. The third and last internal surface method is the determination of the hygroscopicity or the percentage of water absorbed by dry soil from a saturated atmosphere. Essentially this is a measure- ment of the vapor pressure of the water in the soil interspaces and, as no experiments have ever been made specifically on this point, no one knows whether this vapor pressure depends direct- Iv upon the nature of the soil or not. Probably it does not and probabh the determination of the hygroscopicity has neither theoretical warrant nor practical utility. At any rate the case for it is still unproven. llie IWiier Reicniivity Methods. Both the mechanical analysis and the internal surface methods attempt to get at, directly or indirectly, some fundamental, inherent property of the soil, with which property its general physical nature is sup- posed to be in close relation, This is perhaps not entirely neces sary. If, for instance, there were some constant expressing the physical relation of the soil to water and from which the water- holding and water-moving properties of the soil could be deduced, this would probably be all that is needed. Water relations are so much more important than other physical properties that, with thcni known, we could afford to forgo the rest. It is probable, however, that any constant expressing satisfactorily the water relations of a soil would express pretty nearly other physical properties as well. All are probably dependant upon the same, more fundamental, characters. Of the many suggestions towards some such "water con- stant' ' the most elaborated is the method of Briggs and McLean for the determination of the "water equivalent. "* This may be defined as the percentage of water which will rema'n in a soil when it is so whirled in a centifuge as to be subjected to a force of definite and considerable intensity. Essentially this ♦Bulletin 45 Bureau ot Soils, U. S. Department of Agriculture. 1907. Studies in Soii. Physics, IV. 173 is a draining under a force acting like gravity but many times as stronglv. With the same centrifuge running at the same speed, or witli a proj)cr ritio of speed and diameter of drum whatever these may be, the cotiditions are closely reproducible and it is believed that the percentages of retained water thus measured stand in close and pretty rigid relation to the physical nature of the soil and esi:>ccial to its behavior towards water. The exact forms of these relations are not known, and, as be- fore, all correlations are purely e npiri:al. Furt'iernnre, the method itself is empirical and the numbers obtained on the given soil types will not var\-,not only in numerical value but also in relation to each other, with variations in the intensity of the centrifugal force. The amount of water retained by anv given soil varies with the centrifugal force applied, and as the force becomes more and more intense, more and more water is extracted, but, as usual, equal increments of force produce progressivelv decreasing decrements of water content. The amount of water retained falls (as the force is increased) toward a limiting, asvnijitotic value below wliich still further increases of force produce very little extraction of water. Both the actual percentage of water corresponding to this asymptotic condition and the intensity of the force by which it can be ob- tained varv with the physical cliaracter of the soil. In sands it is low and easily attained, in clays it is higher and is attained onlv with greater forces. Now the forces usually employed in determining the water ecjuixalent are intermediate between those competent to produce the asymptotic extraction in sand ^ and those necessary to produce it in clays. Consequently the va'ues thus obtained for the retentivity of different soil types are not comparable with each other, being made by methods not physically aUke. The water equivalent, thus determined, is not really a physical constant but merely an empirical determina- tion made by an arbitrary method and n:jt comparable in any sense with similar determinations made by slightly varied methods. As will be seen later this condition is not insusceptible of improvement, but even if it were, the practical usefulness of the water equivalent would not necessarily disappear. It could 174 The Plaxt World. still furnish a means of soil classification and of the coi relation of physical nature and field properties, provided only that the water equivalent of any given soil type be characteristic of that tvpe and constantly gi^■cn by it. Empirical as it is, such a "crnstant" is better than mechanical analysis and if nothing better can be de\"ised it is doubtless destined to a large useful- ness in future soil investigation. As yet, howe\er, it has been \ery little used or studied. The Critical Moisture Contcni. The foregoing include all the ''constants'' so far used or prominently suggested. There remains, hoA\ ever, one other possibility, as }et nearly unnoted but perha; s the best of all. In the first and second papers of this series there were discussed the relations of the film water to soil structure and to water mo\ement in the soil, and there was nc ted the discovery by Cameron and Gallagher'" of the"critical moisture content'' as a percentage of contained water, definite and constant for each soil, at which contert all the physical properties of the soil are either at a maximum or a minimum. It will be recalled that this critical moisture content is believed to correspond to the point of maximum efficiency of the forces resident on the surfaces of the water films between the soil particles. If this be true here is a soil constant worth Avhile. It is closely (and nearly exclusively) related to the phvsical character of the sjil (since the water-film-system is so related) ; its variations with this physical character are wide enough to be easily measurable; it is expressed simply and in a single unit; and, best of all, its relation to the physical character and to other physical properties is real and rational. It is a real property of the soil — ^a constant which means something. It may le determined in a dozen different ways and neither the accidents of the determination, the history of the sam])le, nor the personality of the experimentor will afi"ect its value. Un- fortunately it has one very serious disadvantage — its determina- tion is exceedingly tedious, laborious and costly. '^' So much is this the case that the critical moisture content, as at present determined, is entirely out of the question as a generally useful constant and can find utilitv onlv in the most extensive scientific ♦Bulletin SO Hun.au of Soils, U. S. Department .if .\griciihurc. I'iO?. ♦For the actual methods the reader is rtferred to Bulletin 50, Bureau of Soils, U. S. Department of Agriculture, above quoted Studies i.\ Soil Physics, IV. 175 researches where labor and expense are minor considerations. Whether this condition is hopeless, we shall see jiresently. Co)tc/usioiis. In the preceding j^ages there have been dis- cussed four '"constants'' whicli have been used or suggested: (I) the mechanical analysis; (.'.) the heat of wetting; (3) the moisture equivalent; and [4) the critical moisture content. Of these the water equivalent is purely and entirely empirical both in method of determination and in its correlations with other properties. It does not attempt to measure any constant propertv of the soil, but onlv the reaction of the soil to a set of arbitrarily chosen conditions. The mechanical analysis is similarlv empirical in its correlations with other properties, but not so much so in its methods. The mechanical compo- sition is a definite and constant property of the soil and is so far as tlie mechanical analysis actuallv measure; this compo- sition, in so far is it a soil constant. But this is not very far. E^ecause of the group error above discussed the mechanical analy- sis is never more than a moie or less accurate approximation to the real mechanical composition, and it is usually less accurate rather than more. I'urthermore the mechanical analysis is expressed in complex and distinctly unserviceable numbers. The heat of wetting is a little better oiT. It is similarly empir- ical in correlation and similarly rational in determination (since it tries to measure a real soil property — the internal surface) It surpasses the mechanical analysis however, in that it actually measures the things which it aims to measure and does it pretty accuratelv, even if not directly nor in absolute figures. But from the logical viewpoint the critical moisture content is the best of all, since it is rational not only in method of determina- tion but also in some of its correlations with other properties. In relation to phvsical condition the value of the critical mois- ture content means something immediately, directly, and in itself regardless of what further correlations may be estab- lished empirically. But logical correctness is not the whole of the matter. Prac- tical utilitv is the essential criterion and here the critical moisture content (because of the difiiculty of its determina- tion) is woefully lacking. Taking all matters into account one must conclude that the heat of wetting is the best of the 176 The Plant World. four. It measures a real soil property with sufficient accuracy and sufficient ease and the empirical character of the correlations between it and field properties is a fault which seems more serious than it is. But the heat of wetting is by no means perfect. It is perhaps the best we have, but it does not follow that it is the bett we can get, and further search is well worth the effort. I am convinced that the most promising line for such search to fol- low is in the devising of a new and practicable method for the determination of the critical motsiure content and there is at least one indication of what such a method might be. In the discussion of the water equivalent it was pointed out that, as the centrifugal force is increased, the percentage of water retained falls toward a limiting or asymptotic value which varies with the physical character of the soil. Now this limiting retenti- vity, or asymptotic water equivalent, is very probably a real proj^erty of the soil and just as much a soil constant as is the critical moisture content. Furthermore, in the few cases so far studied, the critical moisture content and this limiting water equivalent seem to be not only related but identical. So httle experimental work has been done that it is not yet possi- ble to say definitely that this so, but if it is, the whole situation is simplified. We need but to determine the water equivalent with a centrifugal force high enough to attain the asymptotic extraction in all types of soil and — -presto — we have attained the critical moisture content. The problem would be solved and there would be to hand a more capable tool than any which soil investigation has yet possessed. The visi(-n is entrancing but as yet it is only a vision, and it behooves us to set rapidly to work uj)on such experimenta- tion as will prove this vision for mirage or for truth. We need more studies of the critical moisture content, of the water equiv- alent, and, especially of the relations of the two. Aside from its organic relations this is (to my mind) the most vital and the most urgent field of sail physics today. The most impor- tant thing about the physical soil constant is the search for it. Bureau of Soils, U. S. Department of Agriculture, Washington, D. C. Books and Current Literature. \71 BOOKS AND CURRENT LITERATURE. Transpiration in Salt-marsh Plants. — -Ouantitative and analytic studies of plant transpiration are becoming fre- quent. The paper before me, by E. Marion Delf, * is a well- conducted piece of work of the newer type, on water loss from such halophvtic forms as Snlicornja and Suacdi. In the open ing paragraph is to be read a bit of the most egregious teleology which it has been my misfortune recently to come upon. The passage reads that halophytes ''are unable to absorb water freely from the soil, owing to the danger of thereby bringing into the tissues injurious amounts of salts. Since the absorp- tion is thus limited, the transpiration must be also ditnished,'' etc. The idea is attributed to Schimper and it is stated to have been accepted by PfefTer and Jost. Gibson's translation of )ost has it in a form nearly as poetical as the one quoted, but I do not find it thus in Ewart's translation of Pfeffer. Per- haps it may be a long time before current physiological literature may be free from teleology, but the time for actual personifica- tion of plants is surely past, and to suppose them to avoid a danger is closely approaching that. The physiological dry- ness of substrata is in crying need of much more study than it has yet received. To obtain the area of the little boat shaped leaves of Suaeda ten leaves were laid side by side upon the coordinate paper, a tracing made around the whole, and the squares counted in the usual way. The use of the planimeter, which 1 have found accurate and verv much more expeditious than the method of counted squares, was not resorted to. An ingenious method was devised for checking the determinations of area obtained bv calculation in the case of the regular stems of Salicornia. This consists in coating the shoot with a celloidin film, slitting the latter along one side, and removing, after which the method cf squared paper is used. The film nmst not be allowed to dry too thoroughly. The initial transpiration rates of cut shoots of the mesop- phvtic Mecurialis annua, green and crimson Salicornia and Suaeda, all side by side in the open, were determined by weigh - ♦Delf E Maiion. Transpiration and behavior of stomata in halophytes. Ann. Bot 25. 485-505. 19U. 178 The Plant World. ing. For the first 150 minutes the Mercurialis shoots lost 0.173 g. per hour, per 100 sq. cm. of area. For the first 90 minutes the corresponding rate for Siiacda was 0.350 g. The last named plant exhibited the highest rate of water loss per unit area, while Mercurialis showed the lowest. The author determined the ''degree of succulence" of each plant as the water content per 100 sq. cm.; for Mercurialis it was 0.95 g., for Sahcornia 6.5 and 6.1 g., and for Stiacda 10.0 g. Thus t e highest degree of succulence is accompanied by the highest transpiration rate per unit area! Under a bell-jar with liumid- ity about 56%, the relaiiie transpiration, (related to evapor- ation from a water surface, =^) of cut shoots of Salicornii was 0.32 and of Vicia cracca, 0.26 for the first 2 ) minutes. This means the unit area of Salicornii lost 32 '''r,<'>i Vicia 26 % as much water as an equal area of free water surface Here again the succulent loses moisture more readily, ^^r unit of area exposed, than dees the mesplntc. Additional evidence of a similar nature is presented b}- the author, who also points out that, while other succulents (e. g. Sedum) thrive in rather dry air, if plenty of water is applied to the roots. Sahcornia under such conditions does not abs'^rb water through the roots as rap idly as this is lost by transpiration. It thus appears that this form of Salicornia (5. annua), at least, would not succeed unde conditions of intense evaporation, even though its roots were in salt-marsh water. But the air which usually bathes the stems is of high humidity, and furthermore, as is shown in this article the green surfaces absorb water rapidly when submerged, though the absorptive process is not nearly so rapid as that of transpira- tion in moist air, surface for surface. But little absorption takes place from a nearly saturated atmosphere. Determinations were made of the number, size and dis- tribution of stomata in several plants. It appears that, in Salicornia and Aster tripolium these organs open and close with light and darkness, while the plant is young, but that with the coming of the flowering time this power of movement is lost and the pores remain permanently closed. It is to be hoped that the author may continue this work and determine the physical influence of stomatal movements ♦Livingston, B E., The relation of desert plants, to soi moisture and to evaporatii/D . Publication 50 of the Carnegie Institution 1906. Notes and Comment, 179 upon the rate of water loss in such halophytes. — Burton E. Livingston. NOTES AND COMMENT. The report of the fifth annual meeting of the Botanical Society of America contains a list of members and associates from which it appears that the society now has 98 members and 62 associates members, the latter presumably being condi- tionally eligible for full membership. These combined lists include the names of more than 75 professors, associate and assistant professors of botany (including a very few in forestry and plant pathology) ; the remaining names, approximately 85 in number, are of investigators, directors of laboratories, and others, practically all of whom are now or have been until recentlv actively engaged in botanical work. The constitu- tion of the Society provides that "Candidates for membership must be actively identified with botanical work, and umst show special abilitv in original research, as indicated by published papers or merit. A single generation ago a society of this character and of such requirements for membership, if it could have been or- ganized at all in the United States, would hardly have had a dozen members. In the late seventies very few institutions in the countrv made any attempt to maintain a botanical de- partment. Harvard was the best equipped, and while Dr. Grav, relieved of teaching, was devoting himself to the herbarium and the Flora, his assistant professors, Drs. Farlow and Goodale, were offering almost the first and only opportu- nitv in plant physiology and cryptogamic botany that has been known in America. At Yale Professor Eaton set his stud- ents to working on mosses, while he worked on his fern books and buill up his fine herbarium. Cornell had organized a more comprehensive course of botantical instruction with Professor Prentiss at its head, and in Michigan Professor Beal at the Agricultural College was training students in his own unique way and collecting material for his book on grasses. Other lights were rising here and there — among others Britton, Coul- 180 The Plant World. ter and Bessey, and here and there a single worker Hke Peck in New York or Yasey in Washington pursued his lonely way as a special student of fungi or grasses or some other group of plants. Young men were not usually encouraged to choose botany as a specialty unless they had independent resources. The future of the science in America was, to say the least, problematical. No one could have predicted the remarkable development of botany both as a pure science and in its prac- tical application that has has been seen in the last third of a century. Still the leading teachers and botanical investigators of the country are not satisfied, and doubtedless this is well, though one cannot help wondering what he should see if their ideals were fully realized. A resolution adopted by the botan- ical Society of America the Bureau of Plant Industry alleges that the Bureau has suffered severe losses of scientific men during recent years and calls for the Council of the Am- erican Association for the Advancement of Science to investi- gate and recommend such improvements as promise increased efficiency; and the heart to heart talk at the Minneapolis meeting of a group of veteran botanical teachers, through less lugubrious than sometimes happens, recalls the words spoken by a great educator to his embryo teachers ' ' Well, they will learn something in spite of you." Despite all of our shortcomings the botantists of America, nearly all of whom have been trained in the United States, constitute such a body of men and women as cannot possibly be duplicated in any other land, and their work, both in teaching and in research, constitutes a chapter in the history of botany that by no means justifies a pessimistic outlook.— V. M. S. Volume 14 Number 8 The Plant World A Magazine op General Botany AUGUST, 1911 FRONDESCENCE AND FAvSCIATION. * By Henri Hus. It is but natural that forms which show striking morpho- logical changes should attract our attention more readily than do others, color variations perhaps excepted. Thus it required no great effort to find the abnormal dandelion shown in fig.l. It was observed in the spring of 1910 at Ann Arbor, i\Iich., on a plant growing in an empty lot in a spot level with and within a few inches of the sidewalk. During 1909, specimens of both Taraxacum officinale and T. erythrospermum growing here had shown numerous fasciations, especially during the early part of the summer. Throughout 1910 fasciations in this species were few and far between in this same locality, though in other species, especially in Linaria vulgaris, they were fre- quent, though lacking, or at least so few as to escape observation, during 1909. In this particular lot I found but a single fasciation, in the latter part of the year, when, during the preceding week and more especially ten days earlier an exceptionally heavy rain had fallen. The abnormality in the capitulum illustrated, perhaps analogous to that recently described for Gossypium, f is due to the foliaceous development of the outer row of scales of the involucre. *••' De Candolle tt described a similar abnormality in Centaurea Jacea which he recognized as the variety phyllo- ♦Contributons from the Botanical Laboratory of the University of Michigan, No. 122 tAl'.ard, H. A.. An Abnormal Bract Modification in Cotton. Bot. Gaz. 49: 303 Fig. 1910. * *This abnormality is mentioned by Penzig, Pflanzen Teratologic, 2 99 for both T. officin- ale and T . palustre and for the first species also by Masters, Vegetable Teratology, 243. T tProd. 6: SI. 182 '"^ The Pi^ant World. r ccf>hala, specimens of which later were found by Clos, * though in this instance the plant bore both normal and abnormal capi- tula. A similar abnormality has been described for Ct7Uau- rea Icpidophylla. t It is not infrequent in both Plantago major and P. lanceolata [vars. polystachya) and also has been reported for Armeria planiaginea. * * In the appendix to his ' ' De Antholvsi Prodromus ' ' Engelmann describes the same thing for Hieracinm, Pyrethrum and (\)reopsis. An answer to the ciuestion whether such a deviation could be inherited, involved the collection of seed and, since the plant was in an exposed position, its immediate transplantation to the experi- ment garden. Notwithstanding the care used in this operation the plant failed to re-establish itself and the flower had to be collected to make an alcohol specimen. It was a source of great satisfaction therefore, when, a week of so later, on another street, there was found growing upon a sloping bank, and in a position which precluded the ])robabilitv of mechanical in- jury, another plant which showed two instances of the same abnormality. ^Mechanical injury might be supposed to have existed in the preceding instance. It is an important consideration, for there is undoubtedlv a connection between mechanical injury and fasciation. 1 have noted during the last two years that the percentage of fasciated fiowerstalks of Taraxucn))i, when growing along a street, appears to be greater in close jiroximitv to the sidewalk than at some distance from it. In a single instance, when a large number of fasciations were found three feet from the sidewalk, i. c, where I had been led to expect none or few, and on the contrary found a large number within a circle of a diameter of three feet, we were able to explain this apparent deviation from the rule by the fact that this particular spot was frequently trampled by the children of the neighborhood during their play.1t In an earlier' paper attention was called to the fact that fasciations may Ije accompanied by other ab- *Clos, D.. Recherohes sur Tiiiv olucre dcs Sniaiitlierees Aun. So nat 3. Ser 16 •' 40. 1851. tCassat, E.. et J. Ueyssoii. Coiitribulion a I'etuiie des phfenomeiies de Teratologic vcgetale. Bull. Assoc. Franc. Hot. 3: 81) 1900. * *Howles. Armeria plaiitaginea foliaceous. Card. Chron. Ser. 3. 30: 421. 1091. t tThis may have been a mere coincidence for there are not lacking observations show- ing nitmerous fasciations in places which probably never were disturbed by man or animal aiid where other txi^lanalions, iucluding inheritance are in order. It is hoped systematic experiments to settle tliis point may be undertaken in the near future. Frondescence and Fasciation. 183 normalities, * such as tiibular flowers, something well illus- trated by fig. 2 for which 1 am indebted to "Mr. F. C. Gates. An ai'parently normal s;>ecimen of Rudbeckia hirla was collected in 1*?H and transferred to a garden The next ^ ear it still \\ar> n'^rma', at least no j.eculiaritics were noted. In 1906 the plant produced several fasciated stems, bearing inflorescences of which the flnwers were more or less tubidar. The plant continued to show fascia tions up to 19o9 when it died Mrescence often is noted in fasciated specimens, f Yet there a'C manv instances on record where virescence existed Fig. 1. I'r<.>!idc>cciit i-Lipilu'.iim of Taitixiu inn officinale X 1 . without fasciation. Thus, s')me years ago, the cultivated asters seemed to suffer from virescence. In the same vear we noted both virescence and frondescence in Ruiheckia hirta and in Echinacea purpurea without the slighest indication of fasciation. But on the roots of the different species an Aphis was found to exist. That the presence of an insect was the probable cause of virescence has been noted by oth?.s. =^= -^ In some cases the doubling of llowers has been asc-il)ed to insects infecting roots t j. And while, without furth?r proof, we cannot attri- bute the abnormality of the Inraxncnm to this insect, at the *Hus. H Fiisici itions of known causalioii Am Xat. 42: 81. 1908. tUe Viies found in a sin.lc locality siieciincns of Crefns biennis which showed fi^^ciatio^. specimens showinK torsion and viresccnt individuals. Over de erfelyUhcid der fasciatieu. Bot. Jaarb. Dodonea. 6:72. 1894. • •Orrber. Ch , Flcurs vircscentes de la Valeriana Chaussetrappe. Compt. rend. See Biol Paris 60: 5'J.^. lOOfi. fDu<» to Trin^a Cevtrar.lhi) t tMolliard, M., Flcurs doubles et parasitisme. Compt. read. 2: 548. 1902. 184 The Plant World. same time the fact that no such insect was found on the roots of the dandeUons in question is not sufficient to ascribe frond- escence of the bracts to possible mechanical injurv, since in all probability this would have brought about fasciation. Phtzka * observed numerous instances of virescence in dif- Fig 2 Fasciation of J?M(//)t'cA! a /i!r/a X 4,'l^ ferent Compositae and ascribed them to the eft'ect of a fungus, Puccinia compositarum. He also noted that the abnormality was limited to those plants which grew on a soil rich in Ume. Molliard f ascribes virescence of Trifolium re pens to Polyn- thrincium Trifolii Kunze, while Phytoptus seems to have been *Plit7.ka, A , Beitrag zur Teratologic der Komposileii. Ocster. Hot. /.riischr. 52' 100, 159. 1902. t.MolHard, M., Cas de virescence et de fasciation d'origine parasitairc. Rev. gcu. dc Bot. 12: 325. 1900. Frondescence and Fasciation. 185 responsible for virescence of Trijolium procumbens, * and of Trifolium arvense. f The virescence of certain of the individual flowers of our Taraxacum evidently was not as pronounced as that of the plants mentioned by Pluskal, * * for he calls especial attention to the infertility of the flowers. The Ann Arbor specimen how- ever produced abundant seed, which was sown and \ ielded some eighty or ninety plants which up to the present have not flow^ered. From the results obtained we will be able to judge in a year or two whether this abnormal form is entitled to varietal rank. And while, a priori, we would not be inclined to take this view, it must be remembered that cases of vires- cence are known where not only the virescence reappears vear after year, as in the strawberry f f.but that the virescence may be transmitted through the seed as in the case of Oxalis stricta viridiflora. In neither of these instances, certainly not in the last, the virescence appears to be of a pathological character. Other instances of virescence are known which could be ascribed to other organisms, plants or animals, as in the instances above quoted. Peyritsch|| has shown that by transferring aphids from virescent to healthy plants, virescence may be induced. A third kind of virescence, of which the cause never was ascer- tained, has been known to assume the proportions of an epi- demic which may last for years. The second frondescent specimen of our Taraxacum enabled us to carry on experiments to determine the inheritance. It is rather expected that during the next year other such speci- mens will be found, for though the two described were the first we encountered, similar specimens have been noted before as shown by by the instances given above. A remarkably good specimen of this character appears to have been the one referred *Schlechtendahl, H. ^R. von., Uebcrsicht der Ph> toptocecidien. Zeitschr. f. Naiurw. 55: 1882. tKalepa, A,, Neue Arten der Gattung Phytoplus und Cecidophyes. Densch. k. k. Akad. d. Wiss. 59 525. 1893. • *Pluskal. F S.. Beitrage zur Teratologic und Pathologie der Vegetation. Oest. Bot. Wochenbl. 2: 371. 1852. I'nfortunately I am unable to find Bruhin.s " Xeue Beitrage" which contains the original description of an abnormality similar to the one figured here and to which reference is made in his "Teratologische Beitrage," in Verh. k. k. zool. bot. Gesell. Wien. 17: 97. 1876. t fHolmes, Plymouth Strawberry. Gard. Chron. 3rd Ser. 30: 58. 1901. |Hus, H.. Virescence of Oxalis stricla. Ann. Rep. Missouri Bot. Garden. 18: 99. PI. 10, 11. 1907. The distinction between virescence and frondescence shoule be kept in mind. llPeyritsch, J., Zur Aetiologie der Cholranthein einiger Arabisarten. Jahrb. f. wiss. Bot. 13: .1 1882. 1 I |De Vries, H., Een epidemic van vergrocningen. Bot. Jaarb. Dod. 8: 66. 1896. 186 I'he Pi,ant W0R1.D. to recently *, and in which the abnormality was so great that, facetiously, the name Taraxacum paradoxa was suggested for the "new species." University of Michigan. Ann Arbor, Michigan. s STUDIES IN SOIL PHYSICS, Y. i Soil Temperature. E. E. Free. The close dependence of plant growth upon the existence of a proper surrounding temperature is a commonplace of plant physiology and as a part of the ''surrounding temperature," the temperature of the soil is scarcely less important than that of the air. Furthermore, germination is even more closely controlled by temperature than is growth, and for germination the soil is the sole environment and its temperature the only one effective. Among the soil factors to which the physiolo- gist and ecologist must give attention temperature is by no means the least. Nor is it legitin ate to assume, as is often done, that the soil temperature is sufficiently indicated by the average temj:erature of the air. There is a relation, of course, but not a direct nor exclusive one. Soil temperature is not a static thing but results from a balance between the quantities of heat being added to the soil and being taken fr( m it. When more heat is entering than is lea\ing the soil grows warmer; when the reverse condition obtains it grows cooler. Its tem- perature is seldom constant, being subject not only to the usual diurnal and annual c\cles,lnit also to many accidental changes. The wider of these variations are climatic matters, under the the control of meteorological factors v. ith which the specific nature of the soil has little or nothing to do. Such are outside our present interest. The soil character does, however, influ- ence its temperature, and sufficiently importantly to have some phvsiological and ecological significance. This matter de- ♦American Botanist 15: 27. 1909. t Published by permission of the Secretary of Agriculture. Studies in Soil Physics, V. 187 serves a little nearer attention but as a preliminary thereto it will be well to review briefly the means by which heat is added to or abstracted from the soil The ultimate source of nearly all soil heat is the radiant energy of the sun, and indeed this is the source of much of it immediately as well as ultimately. Direct or reflected sunlight is the great soil warmer. The soil also loses heat b\' radiation, mainly during the ni,';ht, but the amount is usually less than that gained similarly during the day. Next to radiation the largest additions or subtractions of heat are by means of the entering or leaving water. If the soil is cooler or warmer than the rain which falls on it this rain will warm or cool it and indeed this is frequently the most practical factor aff'ecting the soil temperature. It ma\ require days of sunshine to counter- act the cooling effect of a few hours of cold rain. Of course the amount of heat "added" or "subtracted" by rain falling on the soil is measured not simply by the temperature of the rain but by the amount and sign of the difference in temperature between the water entering the soil and the same water as it leaves in the drainage. If the water leaves cooler than it en- tered it has warmed the soil, and conversely. Besides radiation and added water there is only one major means of heat transfer-the loss of heat occasioned by the evap- oration of water from the soil surface. Even this is only oc- casionally of practical importance and the previously named factors remain the only ones which need \crv careful consider- ation. There are also many still less significant ways in which heat is lost or gained, among which may be enumerated: (1) the heat deri\ed from or given up to the air in contact with the soil, (2) the heat transferred by conduction to or from lower strata; (3) the heat derived from radioactive materials in the soil; and (4) the heat given up by ])lants * and animals to the soil. All these are very small in amount and entirely unimportant. From our present viewpoint it is also unnecessary to concern ourselves with the mechanism of the transfer of heat from place to place in the soil, especially as this matter has already been •Contrary' to an opinion still sometimes expressed the soil does not give up heat to the plant Quite the reverse Under usu;il growing conditions the plant is nearly al- ways warmer than the soil and heat flows from root to soil instead of in the reverse direction. The plant nui'-t be kept in warm soil not because heat, as such, is necessary to its growth but because it must be maintained at the temperature at which the rrzymolic reactions upon which growth depends are able to go on. If the soil he too cold the plant looses heat k) r.ipjdly lh.it (his optiiiiuni temperature cannpt be maintained 188 The Plant World. thoroughly discussed by Patten. * Essentially the heat equa- tion of the soil is the balance of, (1), the heat added by radiation plus, (2), the heat added in rain water; against, (1), the heat lost by radiation plus, (2), the heat loss in the drainage water plus (in some cases), (3), the heat "absorbed" by evap- oration from the soil surface. This, however, is not the whole of the matter. We are interested not only in the temperature of the soil at any given moment but also in the rapidity with which this temperature will change under any given rates of heat supply and removal. For instance one of the most important questions in soil ther- mics is that of the rapidity with which various soils become warmed in the spring. These questions of rate of change are largely questions of specific heat.t The more heat required to warm a body the more slowly will its temperature rise under given heat supply. Now the solid constituents of the soil have all about the same specific heat, but the specific heat of water is about five times as great. Hence it takes much more heat to warm water than to warm dry soil, and much more heat to warm a wet soil than a dry one. Other things equal the wetter soil will warm more slowly and conversely, cool more slowly. This is a matter of no small practical importance and upon it depends the necessity of arranging that soils be well drained in the spring when tbeir rapid warming is most desirable. Turning now to the influence of the nature of the soil on these various thermal questions, we see, first, that the heat addded or subtracted as a result of warm or cold rains need receive no consideration. Such heat movements have nothing to do with the soil as such and are not sensibly affected by its nature, nor under the control of those who handle it. This leaves only the radiations, and of these,the positive radiation only is affected by the soil character. The amount of heat radiated f r o m a soil depends only upon its temperature and not at all upon its individual properties. The amount of radiant energy absorbed is, however, considerably affected by one soil property — the color. In general darker colored bodies absorb and retain a larger proportion of the radiant energy which falls *Bull. 59. Bureau of Soils, U. S. Department of Agriculture. tThe specific heat of a substance is defined as the quantity of heat necps-ary to raise a given quantity of the substance through a given temp raturc interval. This .same quantity of heat vn\l be given up by the substance in cooling though this same interval. Studies in Soil Physics, V. 18§ on them than do bodies of lighter hue, and soils behave like other substances in this respect. The darker the soil the more radiation it will absorb and, other things equal, the warmer it will become. However, the light colored soil by no means fails to absorb radiant energy altogether. It simply absorbs a little less and indeed, there is seldom sufficient color diflference between ordinary soils to make any very great dif- ference in the thermal absorption. Nevertheless color is of some importance, and it is the only soil property which mater- ially affects the gains and losses of heat. From the practical viewpoint the variations in exposure (dependent upon topo- graphy, vegetal cover, etc.) have much more effect upon the supply of radiant energy, but these matters are so obvious and well known that their discussion here is hardly necessary. The really important way in which the character of the soil influences its temperature is connected with the second question of rapidity of temperature change rather than with the gains and losses of heat. The amount of water which will be normally held by a soil depends upon its physical nature, * and it is obvious from the above that the more water retained by, and present in, the soil the higher will be the total specific heat of the system, and the more slowly will the soil be warmed. Thus a clay which holds thirty percent of water will warm much more slowly than a sand which holds only five percent. To this factor must be ascribed the well known tendency of sandy soils to warm early in the spring and their proverbial utility for the ' ' early ' ' vegetables. So important is this matter of water content that it far outweighs color and any ordinary differences in exposure. Of two soils, one sandy, well drained and light in color; the other heavy and wet but very dark, the sandy soil will warm much the faster in spite of the apparent advantage given to the other by its darker color. Exactly this case is common in the truck regions along the Atlantic seaboard where the light colored sandy soils of the rises alternate with the much darker heavier soils of the slough bottoms. The light colored sandy soils are so much earlier that it would be quite impossible to convince *As discussed in the second paper of this series Plant World 14, No. 3. (1911) 190 The Plant World. a farmer of this region that dark colors assisted the warming of a soil. Bureau of Styils, U. S. Department of Agriculture, Washington, D. C. NOTES ON THE ROYAL MOCCASIN-FLOWER. Eugene E. Barker. The royal moccasin flower (Cypripedium reginae Walt, or C. spectabile, Salisbury and Swartz), as it grows in the foot- hills of the Adirondack Moinitains, shows interesting and marked response to the intensity of sunlight it receives. This response to the amount of insolation is apparent in the size of the plant, the posture of the leaves, the abundance of bloom, and lastly, though probably indirectly, the number of flowers that set seed. The more open parts of cedar swamps, where its fibrous roots feed in the cold, wet muck, are its favorite habitat Here it attains to maximum luxuriance. When it groA\s in open sunliijht, among onlv small cedars and stunted willows, the plants are stocky and the leaves point sharply upward, curving somewhat around the stem, and the flowers are pale in color for the most part. Those plants which grow in difl'use sunlight under the cedars are taller (about three feet high), the flowers have a richer hue, and the great expanded leaves spread horizon- tallv to the light There are however, fewer stems from each root, and a larger percentage bear no flowers than among those growing in the open. When one cuts a stem close to the ground, he is surprised at the amount of water that runs from the cut end. This water was not in the stem, however, but held in the lowest leaf, which is small and clasping. Rarely one finds a flower with the labellum pure white. Two such flowers were noticed this season growing together in the sunlight. The interior, as in normal flowers, was stieaked. Two monstrosities were found, one with an anther on the face of the stigma, another that lacked the labellum. Notes ox the Royal Moccasin Flower. 191 There seems to have been little actual observation done upon the polHnation of this flower. Darwin mentions bees as the implied fertilizers for the genus Cypripedium, and Gibson says "doubtless many of the smaller bees do effect cross- fertilization in the smaller species." He says that he has often sat long and patiently in the haunt of the cypripedium, await- ing a natural demonstration of the cross-fertilization of C. Fig 3 Sketches of the flower of Cypripedium regtriae. showing manner of pollination acaule, but his devotion was never rewarded. He gives a charming description of the process however, as demonstrated for him by a captive bumble bee with cut flowers in his study. In C. hirsutum Dawin found that small bees were more ser- vicable. Prof. Herman Miiller studied C. calceoliis for many years and gives the following description of its cross-fertiliza- tion, which I quote in full, as it applies equally well to C. reginae, so far as my observations go. "I have observed", he says, 192 The Plant World. "five species of Andrena fertilizing the flower, viz. A. nig- roaenea K, A. fulvicus K, A. albicans K, A. siriceps K, {A. irihialis K.) and A. pratensis Nyl . . These bees attracted by the color and perfume of the flower, fly into the slipper-shaped lip, and bite the hairs lining its floor, which are sometimes covered with small drops of honey. They try for some time to escape by climbing up the vaulted sides of their prison towards the orifice that they entered by; at last, after creeping beneath the stigma, they manage with a great effort to escape by one of the two small lateral openings at the base of the lip; in doing so they smear one shoulder with a sticky pollen from the anther immediately above. In the next flow- er the bee, as it creeps up the stigma, leaves some pollen on its papillae, which are long and point obliquely forw^ards, then squeezing itself again through one of the small orifices it ac- quires another load of pollen : cross-fertilization is thus eff'ected regularly. ' ' Last summer I spent several hours in the habitat of the royal moccasin flower watching the plants and their insect guests. The only insects seen to visit the flowers were bees, and they effected cross-fertilization for this species in exactly the manner described by Miiller for C. calceolus. The bees were captured in the act, and later identified as all belonging to the genus Andrena. What good they obtained when visiting the flowers I have not discovered. So far as I can detect, no nectar is secreted, either inside the labellum, or within its tissues. Possibly the hairs fringing the lining are eaten as Miiller observed. Darwin speaking of the genus in general says, ' ' I have never been able to detect nectar in the labellum, ' ' and Kurr makes the same remark with respect to C. calceolus. Last year's stems persist bearing the seed pods, and attest an intimate relation between plant and insect. The great num- ber of seedling plants to be seen gives further evidence. In order to get a more definite idea of the exact proportion of flow- ers that are pollinated I made a careful count of blossoms and last year's seed capsules. As the amount of bloom on each plant is very constant from year to year, the comparison of the seed of last year with the bloom of this year seems valid. The following tables give the data obtained. Notes on the Royal Moccasin Flower. 193 TABLE I-PLANTS GROWING IN THE OPEN. No. of No. of No. of No. of No. of No. of Total stems stems stems stems last stems bloom bearing with with with year's to a on a two single three no seed plant ]ilant flowers flower flowers flowers pods 7 10 4 2 0 1 8 9 12 5 9 0 2 6 12 12 5 2 0 2 6 11 18 8 2 0 2 7 11 21 8 2 1 0 9 15 28 11 3 1 0 23 6 10 4 2 0 0 7 15 28 10 2 2 1 25 22 32 12 8 0 2 13 17 29 10 6 1 0 12 6 8 2 4 0 0 1 4 7 3 1 0 0 3 19 34 15 4 0 0 38 16 23 9 5 0 2 11 2 4 2 0 0 0 1 7 13 6 1 0 0 1 13 16 4 8 0 1 6 7 8 3 2 0 2 6 4 1 1 3 0 0 3 203 326 124 60 6 13 191 TABLE II — PLANT.S GROWING UNDER CEDARS IN SHADE. No. of No. of No. of No .of No. of Total stems stems stems last stems to bloom on bearing with a with no year' s a plant a plant two fluwers single flower flowers seed pods 13 18 8 2 3 3 1 2 1 0 0 0 3 1 0 1 2 0 6 7 9 3 1 2 3 4 1 2 0 0 3 6 3 0 0 2 5 9 4 1 0 1 11 2 0 2 9 2 8 4 0 2 5 0 1 2 1 0 0 0 2 2 1 0 1 1 3 2 1 0 2 2 59 59 23 13 23 13 194 The Plant World. TABLE III COMPARIXG PLANTS IN OPEN AND SHADE. Total nviinber of plants counted Total number of stems counted Total numlier of flowers counted *Average numl)er of stems to a plant . . Per cent of stems bearing no bloom Per cent of stems bearing bloom Per cent of stems bearing two flowers . . Per cent of stems bearing one flower . . . Per cent of stems bearing three flowers. . Per cent of last year's pods to this year's flowers In open J In shade 91 19. 12 20.3 59 .326 59 10.68 4 6 01 .39 9.3 . 99 61 61. .^9 21.56 22 2.95 00 58 58 22 *Not a fair conclusion for the whole population, because many sin- gle stems and smaller grouj)? in the open were not counted. Table III brings out quite strikingly the differences of growth due to amount and intensity of sunhght to which the plant is exposed. Those growing in shaded situations (although the flowers are more deeply colored) bear hardly more than half as many flowers as those growing in the open, the percentage of barren stalks is over six times as great, and the profusion of flowers to a single stem is markedly less. No measurements were taken as to height, but my opinion is, that the shaded plants would average several inches taller. Bees of the genus Andrcna were found to be the customary agents for effecting fertilization in this species. As they work during the warm sunny hours, and would naturally frequent most the more conspicuous and accessible flowers growing in the open glades, the fact that over half the flowers in the open set seed, while only a little more than one-fifth of those among the cedars do so, would seem significant as evidence that An- drena is the pollinating agent for this plant. Cornell Lniversity, Ithaca, New York. Books and Current Literature. 195 BOOKS AND CURRENT LITERATURE. The Physics of Transpiration. ^ — Students of plant transpiration in its pyhsical aspect will be interested in the recent studies of Renner '•' upon the influence of the size, shape and position of an evaporating surface upon its rate of water loss. This paper is a continuation of the author's earlier studiesf upon the relation of form, position, etc., of foliage leaves to their transpiration rates, with especial reference to the vapor blanket which tends to cover foliar sur- faces in quiet air. In the recent contribution, Renner is occu- pied with physical evaporation from water surfaces and from the surface of wet blotting paper. Pieces of the latter material were supported on glass plates and care was taken that neither too much nor too little water was added, to produce complete saturation. After wetting the rate of evaporation remained constant (under constant conditions) for an hour or longer, during which time the experiments were carried out. The rate of water loss per unit area was, in this first hour, not markedly less than that from a free water surface. The following points are brought out:- Paper circles and circular pans of water, placed upon a balance, lost about ten percent more water when the balance was slowly and just perceptibly swinging than when at rest. If the rate of evapor- ation from horizontal paper surfaces be increased by wind to six times its original magnitude, the original rate is regained in not over two minutes after the wind ceases. Two parallel vertical paper surfaces fail to influence each other sensibly when but two cm. apart. When nine mm. apart their rate of water loss is decreased only twenty-five percent. The water vapor thus diffuses but little laterally from such surfaces. Circular and rectangular papers lose moisture more rapidly when vertically than when horizontally placed. Water loss is more nearly proportional to the linear dimensions of the sur- faces than to their areas, though various conditions modify the proportionality. Of two rectangular surfaces with equal areas but with different forms (in still air), the narrower always loses considerably more water per unit of time than does the broader. This is of great fundamental importance in comj arisons *Renner C, Zur Physik der Transpirati. n. Be", d d. Bot Ges. 29: 12135 2. 1911. •fReuner, C. Beitratie zur Thysik der Transpiration. Flora, 100: 48S. l^JlO. i96 ^HE iPLANT World. between the rates of transpiration from differently shaped leaves; it is to be related to the effect of the vapor blanket, the margins of a surface being much more efficient in evaporation than the central portion. It is clear from Renner's admirable analytical studies that the underlying physical principles of plant transpiration (even when all intra-foliar changes such as stomatal movements etc., are corrected for) are not simply those of gas difl'usion. The phenomena are modified by size, shape and position of the leaves, so that, as the author well points out, it is essential to understand these physical modifications as far as possible, so as to avoid confusion of these with supposed physiological regulation. — Burton E. Livingston. Mendelism. — Punnett has published a new edition of this excellently written treatise on ]\Iendelism,* which brings it up to date and makes it, like the two preceding editions, the most readible account of recent progress in working out the laws of heredity. No attempt is made at exhaustiveness but each phase of the subject is illustrated by typical cases chosen most- ly from the experiments of Bateson and the author's other associates at Cambridge, England. The checker board method of solving Mendelian problems is presented ^^ith great simpli- city and used with such frequency that the reader will gain a clear conception of the method and its usefulness. In one of these checkerboards (p. 52) three squares are blackened which should be white, and three squares which contain C and B and which should therefore be black are labeled "albino." The author omits all discussion of the chromosomes on the ground that there is not sufficient unanimity of opinion as to their significance in relation to I\Iendelism to make a discussion of them suitable for popular treatment. The reviewer considers this omission unfortunate, and believes that a chapter on the chromosomes presented with the same clarity that characterizes the other chapters, would have added value to the book. The introduction of many excellent figures and six plates, five of ♦Punnett, R. C, Mendelism. ThirJ. edition tntirely rewritten and enlarged; pp. 14 192. Figs. 3'. Pis. 6 and frontispiece portrait. 1911. New York: Macmillan Co. $1.25 Notes and Comment. 197 which are colored, lend attractiveness to this new edition and will materially aid the reader in comprehending the nature of the problem and the method of its solution. General readers, teachers and those primarily interested in other fields of science, but who desire to keep in touch with the work being done in genetics, will find Punnett's book a delightful source of infor- mation.— ^Geo, H. Shull. Dry Farming. — Briggs and Belz have made a study*of the rainfall and evaporation conditions which prevail in the semi arid portions of the United States in their relation to the practise of dry farming. The region in which this form of agricultural endeavor has been developed is the northern part of the Great Basin and the western edge of the plains, where the annual rain- fall is less than 20 in and more than 10 in. The authors call attention to the importance of the seasonal distribution of the rainfall, to the deceptive appearance of annual totals of rainfall in regions of torrential rains, and to the vital importance of evap- oration in offsetting the apparent value of a given amount of rain. In southern Washington dry farming is being successfully conducted in a region with winter rainfall of 10 in. and less, by the method of alternate cropping the summer fallowing. In Utah 13 in. of rain is the minimum fall that permits of dry farming methods. In North and South Dakota low yields of wheat are obtained on from 5 to 8 in- of rain, which falls chiefly between April and July. Near San Antonio, Texas, the growing of sor- ghum has been possible with an annual fall of 13 in., a seasonal fall of 8 in., and a doubling of this fall in other years has given seven times as great a yield. The total evaporation from April to September, as measured in the tanks of the dry farming stations of the Buieauof Plant In- dustr3^ are from 50 to 60 in. for Nevada, southern Arizona, the panhandle of Texas and southern Kansas, and from 30 to 38 in. for the DakDtas.— F. S. NOTES AND C JMMENT. .\ recent l)ulletin of Washingt. n University, in cooperation with tliC Mssouri Botanical Garden, announces twenty-live ♦ Briggs, L. J. and Be'.z, J. O , Dry Fanning in Relation to Rainfall and Evaporation Bur. Pl.Ind. null. 188. 198 The Pi.ant World. courses in botany and opportunity for research in Taxonomy, Applied Mycology, and Ph\siology, as well as independent re- search open to persons qualified to carry it on. The extensive equipment, consisting in part of a new and well equipped fire- proof laboratory, a library of over 60,000 books and pamphlets, an herbarium of over 600,000 sheets of specimens, and a col- lection of living plants including upwards of 10,000 species or varieties, may l:»e taken as some indication of the facilities nov.- offered to botanical students and investigators. From this institution, whose complete equipment for such work is compara- tively recent, if we pass in review such of the older universities as Harvard, Columbia, Cornell, Pennsylvania, Michigan, Chicago, and as manv more state and other institutions, we can not fail to observe in this country a development of facilities for instruc- tion, and especially for research, in various departments of bot- any that is hardly short of phenomenal. The explanation ap- pears to be that the subject which within the memory of manv of us was treated with kindly indulgence, or in some cases with supercilious contempt, by members of the philosophical faculty has proven its educational value, which is now freely admitted on every hand, and furthermore that its practical applications have become so numerous and important that they are frankly recognized and liberally provided for as matters of state and nation-wide ccncern. There is perhaps no subject in the school curriculum the status of which has so completely changed within a relatively short period of time. — V.M.S. The Catalogue of the Agricultural Exhibition of Switzer- land held at Lausanne in 1910, contains various suggestive contributions, among which is a noteworthy one on the plants of Switzerland that serve as soil indicators, by Dr. C. Schroter. The author divides the plants under consideration into three classes: 1. Such as are strictly confined to a particular quality of soil, c. q. humus plants. 2. Those that show a preference for certain soils without being strictly confined to them. 3. Plants so far indifferent to the substratum that they cannot be employed as indicators of soil factors Certain principles stated at the outset show that the study involves constant allowance for and widespread knowledge^ of the concurrent action of various factors. These include (1) Notes and Comment. 199 'The behavior of other species. Many halophytes thrive in cultivation on soils that are salt. They do not require the salt; they merely endure it better than other species, occuring in nature in salt spots, on or the sea shoree, etc., where the latter cannot compete with them. (2) Influence of other soil factors. The soil presents a trying composite of physical, chemical and or- ganic factors which may mutually influence and replace each other, so that the dependence of plants on one of them is often influenced by the action of others. Many plants that shun limestone, for example, will endure large quantities of lime in the soil if they are provided with a sufficient supply of potash. (3) Influence of climate. Climatic factors may to a degree replace soil factors; in a moist climate the same plants may thrive on a dry soil which would avoid this in a dry climate. With optimum climatic conditions a species is often in- different to soil in the center of its range, while at the periphery of its area of distribution, where it is less capable of resisting unfavorable climatic conditions, it becomes established only on soils best suited to it, and it becomes there a soil indicator. (4) Physiological varieties. There is no doubt that certain kinds of soil influence many plants in such a way that "soil varieties "arise which in cultivation on other soils may return to their normal form. Examples of these are the well-know forms of fern on serpentine and of violet on zinc soils. Such "soil varieties" occur in nature only on the soils to which they belong. Physiological varieties, not distinguishable by external characters, may arise on granite or limestone for instance which deport themselves quite difi'erently under difl'erent external conditions. In regions where other conditions are better suited to the "limestone form" this may become dominant and ap- pear to be an indicator of limestone, in others the "granite form" thrives best, and in a third region both thrive and the plants appear as if indifferent to the kind of soil. Plants as soil indicators are considered in their relations to chemical constituents of the soil, humus content, and moisture. Only the first and second are discussed, the former at length and with special reference to plants belonging to limestone and other rocks as studied by the author in Switzerland. The pains- 200 The Plant World. taking collection of data and the theoretical considerations and conclusions are too voluminous for reproduction but should be duly weighed by students of plant distribution.^ — V.M.S. The choice of crops for alkaline land is discussed by Thomas H. Kearney in Farmer's Bulletin 446 of the United States Department of Agriculture. To get rid of the excess of salts in alkali soils by flooding and drainage is expensive, and often impracticable, hence it becomes necessary to investigate care- fully the relations and possible adaptations of various crop plants to such soils. Thus a question primarily economic becomes one of great scientific interest andinspiteof its difficulties good pro- gress is being made towards its solution. The author's state- ment of principles suggests at once the complicated nature of the problem. In the first place it is shown that the mere state- ment of the percentage of alkali in a soil tells us little about how plants will be affected. Some plants which can endure one percent of alkali if present in a heavy soil, would quickly perish in a sandy soil containing the same quantity and the same kind of salts, the reason being that the heavier soil can hold more water. Again in regions of winter rainfall like California a winter crop might succeed better in alkali land of a given con- centration that a summer crop that is actually more resistant. The vertical position of a given quantity of alkali in the soil in relaiton to the depth reached by plant roots is also an important matter. Thus, for example, a comparatively small quantity of alkali near the surface will prevent crops starting that might grow well if a heavy rain or irrigation has occurred just before planting, resulting in driving much of the alkali into lower depths of the soil. Crop plants adapted to difi"erent grades of alkali in soils are discussed at length and useful practi- cal suggestions are given which give the impression of careful scientific weighing of the complicated interrelations of the factors involved. — V.M.S. William Hussell Dudley, Professor of Systematic Botany in the Iceland Stanford Junior University from 1892 till 1911, Notes and Comment. 201 died on June 4, 191 1, at the age of sixty-two. By ancestry and place of birth a New Knglander, a graduate and for twenty years a member of the botanical staff of Cornell University, a student of De Bary's for a time in Strassburg,he brought to California the mature powers of an enthusiastic student and sympathetic lover of nature, the ripe scholarship and the win- ning personality of the inspiring teacher. At home in the lab- oratory,he was still more strikingly the gracious host when he was with students and other friends out of doors, in the fields and woods and mountain forests. He knew the forests of middle California as no one else; his acquaintance was with individual trees, as his collection of tree portraits testifies. And his studies of their geographic- al distribution, following and amplifying the earlier studies of Asa Gray and others, gave his knowledge a degree of accuracy and detail, as well as breadth, which was very prec'ous. It is to be hoped that his notes and other manuscripts are in such condition that his associates and successor can give them to the world. Professor Dudley's nature was so sensitive, his percep- tions so fine, and his ideals so high, that he could but rarely bring himself to publish what he knew. He wished always to add to and improve what he had learned and written. Thus the botanical world had little opportunity to know his accom- plishments and achievements. Besides the young men and women whose lives he has en- riched, and llic Forest .Service wjiich he long assisted in various ways, he contribute:! to the great gift to California and the Nation whi::h the State and National Forests of California constitute. The "Bi; Basin Park,' the property of the state, will preserve to all time a part of tiic natural redwood forest of the Santa Cruz Mountains. Profesi:)r Dudley assisted in secur- ing and preserving as a state park tliis part of the virgin forest of Seju^ia sempervireri''-. It wa=; his interest too which stim- ulated and directed the federal authorities in the selection of others of the mountain forests of California as national forests. nf courtly manner, ctiltivated as well as educated, of ripe scholarship and rich in the knowledge of nature, he was a love- able and elevating associate, an inspiring teacher, a devoted 202 The Plant World. man of science, an honor to Stanford University of which he was an honored member. — G. ]. P. Mr. George B. Rigg, of the University of Washington, has devised a useful method for preparing large algae such as Nereo- cystis, Lamimria and Alaria for demonstration purposes, re- garding which he writes as follows : " If specimens of any cf thelargeralgaearetakenfrom the water and dried at once in the sun they will keep, but they are too brittle to be handled with- out breaking. Specimens, may of course, be preserved in liquid preservatives but they are not convenient for handling on account of the liquid dripping from them. If preserved in formalin they tend to become soft after a few months The writer has used the method of soaking these algae in the following solution : tap water, 84 percent; glycerine, 15 percent, formalin, 1 percent. The plants were taken directly from the water and placed in the solution in a wash tub, where they were left for 48 hours and then spread out in the sun to dry. About two dozen spec- imens of Nereocystis leutkeana were first prepared. Later a few specimens of Alaria valida, Lamina ria saccharina, and Rhodymcnia pertnsa WQX^ prepared. The first plants prepared have been used during the past year for demonstration pur- poses and for gross study in the laboratory in the elementary botany course in the University of Washington. They have all been kept in a wooden box without cover. At the present time (I\Iay 1911) they are in satisfactory condition, being flex- ible enough to be handled without breaking. It is observed that those kept in the top of the box show a slight tendency to be- come brittle, but the flexibility of those kept deeper in the box is entirely satisfactory. None of the sporophylls of Alaria have broken off, and there has been no collapsing of the bulb or of the hollow part of the stem in the Nereocystis specimens. All of the plants are slightly oily to the touch but not enough so to be very objectionable, and are of the consistency of very thin leather. No attempt was made to procure the largest speci- mens available, the plants selected being of ordinary size. The largest specimen of Nereocystis prepared measures 27 feet from the holdfast to the bulb, and the fronds measure 10 feet, mak- Notes and Comment. 203 ing a total length of 37 feet. The largest specimen of Alaria prepared is 10 feet in length, and the largest one of Laminaria is 3 feet. The only difficulty met with in treating these plants was that of removing them from the solution and spreading them out without tearing the fronds. This difficulty was espec- ially great in the case of Nereocystis because the numerous narrow fronds tangled badly, When, however, they were once spread out in the sun, they became tough in a day or two." In September 1910 I came upon a young sycamore tree with unusually large leaves, the largest of which measured 16, 18 and a little over 21 inches across. The tree, which had a height of only seven or eight feet, was situated in a very shady place on the banks of the Little White Oak Bayou at Houston, Texas. It grew under a full grown sycamore, which came in contact with a dense growth of tall weeds on the steep slope above and interlocked with the branches of trees on the other side of the bayou. By this practically all the sunlight was ex- cluded. The young tree was very slender, scarcely more than an inch thick at the base, and bore no lateral branches, its whole energv being apparently spent in the manufacture of leaves. The size of the leayes of Plaianus occidental ix '..., the sycamore of this region, is given by various writers as from 4 to 9 inches in diameter. These leaves were, therefore, far in excess of the maximum recorded size. — R. A. Studhalter. The manner is well known by which the pollen masses of the Asclepiads are extracted and carried off by insects whose limbs are caught by the gland which unites these twin masses It does not seem to have been noted, however, that this apparatus may also sometimes act as an insect traj). »Such is the case with the large flowers of Asclepias eriocarpa, a species common on the plains of southern California. Not infrequent- ly honev bees, alighting on the umbels of this species, have several of their legs seized by the sensitive glands of different pollen masses, which they are then unable to extract, and so are held until they die. As many as six or seven dead or dy- ing bees may be found on a single umbel. — S. B. Parish. 204 The Plant World. The reference in the June number of The Plant World to the work of Mr. S. B. Parish on "The Southern California Juncaceae" was, unfortunately, worded so as to leave the clos- ing lines quite ambiguous. The writer of the notice lequests us to make plain that Mr. Parish is no! the man who published in Muhlenbergia a species distinguished as follows: "The per- ianths are larger in the species here proposed as new ; but a better character * * * is the great length of the oblong and leaf-like segments of the involucre. ' ' Volume 14 Number 9 The Plant World A Magazine of General Botany SEPTEMBER, 1911 A STUDY OF THE RKLATIOX BETWI'I-X SUMME^l EVAPORATION L\TENSITV AXD CENTERS OF PLANT DISTRIBUTION IN ,THE UNITED STATES. Bi'RTON Edward Livingston. Since by far the major portion of the water absorbed by ordinary gieen plants merely passes through the plant body and is lost in transpiration, it naturally follows that the trans- piration rate is itself the main condition \\hich determines what may be an adequate rate of water supph' to such organisms. But, as was first quantitatively shown in Publication 50 of the Carnegie Institution (1906), the main condition which deter- mines the intensity of transpiration from any plant is the evaporating power of the air, and when an instrument became a\ailable bv means ( f which it is possible rather readily to measure and integrate this complicated climatic factor some- what as it affects plant transpiration, it was suggested that com- parative determinations of the various intensities of the evap- orating power of the air which prevail in the different parts of the United States in summer should furnish us with an approx- imate measure of the demands of transpiration water which the surrounding air makes during the season of greater plant activity, upon the vegation of the different regions. In other terms, it appears that the intensity of evaporation during the growing season should offer a climatic criterion from which might be derived a somewhat satisfactory correlation with the general facts of plant distribution. This seems the more prom- 206 The Plant World. ising ^A•hen considered with the fact that the same general meteorological conditions which promote evaporation tend to render the precipitation low The publication of Transeau's pioneer study * of the relation between vegetation and the precipitation-evaporation ratios for the eastern part of Xorth America gave added interest to this problem, for the charts of this author seem clearly to indicate a very definate corres- pondence between the nature of any vegetation type and the ratio of annual rainfall to annual e\aporation for the region occupied by that type. In so far as climatological features control the present dis- tribution of the vegetation of the world, it is to be expected that the quantitatixe relations existing between these features and the vegetaticnal characters will prove to be rather a complex one, and it will no doubt require long continued study to enable us definitely to express these relations. The integrations of many meteorological elements, for various portions of the year, will need to be considered, in the synthesis of the much- desired climatological formula for plant distribution. Since Transeau's (1905) and the writer's (1906) studies on the relation of plant occurrence and behaviour to evaporation intensity seemed to attribute an importance to this particular factor which had never before been emphasized, it seemed desirable that the gen- eral relations between the evaporating power of the air and the nature of the vegetational cover be explored from several different standpoints. It must thus he understood that the present study aims, not at all to displace the method of annual ratios, which was the first recorded attempt to inter] tret plant distribution quantitativeh' in terms of a climatic function in- volving evaporation, but rather to test cne other method for studying the relationship concerned. It was of course to be ex- pected that the two methods, of annual ratios and of summer evaporation intensity, would not exhibit a detailed agreement; the very nature of the problem and of the data involved pre- cludes such agreement, and it is only along broad, general lines that the results of such studies may at the present time be scrutinized. *Transeau, E. N.. Forests of Easteu America. Amer. Xat. 39: 875 98. 1905 Idem, Climatic centers and centers of plant distribution. Micb. Acad, of Sci., 7th Ann. Report, 1905. A Study of Evaporation' and Plaxt Distribution'. 207 The only series of observations on the intensity of evapor- ation in the United States,* which has been heretofore avail able, and that used by Transeau. is that made by T. Russell f for the period July, 1887, tn June, 1888, inclusive. These are not direct observations, but deductions from readings of the wet and dry bulb thermometers and the barometer, and aie of uncertain accuracy on account of the incom] leteness of the fornnila by which they were computed. It was theiefore deemed worth while to attempt a series of direct evaporation observations over the United States throughout the summer months and to compare the results with the general vegetation- al characters of the various parts of the countrv. The measure U'ed was the rate of water loss from the porous cup atmo- meter, which is affected by external conditions in much the same manner as aie ordinary plants, and which automatically sums the records, so that readings may be taken at any suitable intervals of time. This work was carried out---' under the auspices of the Department of Botanical Research of the Carnegie Institution. The plan was first put into operation in the spring of 1907. Porous cups were sent to twenty-four stations, fairly well dis- tributed over the United States, and were operated, with weekly readings, for a period extending from May to September. The cups were placed in the open, with free access of sunshine and of wind. The center of the cup was fifteen centimeters above the soil surface, so that the records may be considered as approximately proportional to the evaporating power of the air as this would affect the transpiration of a plant of about the above named height, giowing in the open. ft The details ♦Perhaps the best series of obsen-ations on the intensity of evaporation which has so far been recorded is that of T Okada, Evaporation in Japan. Bui. Cent. Met.Obs.. Japan. 1904. No 131. A general review of the literature of evaporation of throughout the world has been published by Grace J. Livingston, An Annotated Bibliography of Evaporation. Monthly Weather Review for June. Sept.. and N'ov , 190S. and Feb.. March. April. May and June. 1909. The student of this subject will find many suggestions and much of general interest in the recent publication by Briggs.L.J .and Belz. J. O., Dry farming in relation to rainfall and evaporation. Bulletin 188. Bur Plant Ind . U. S. Dept. Agric. pp. 71. 1911 tRussell, T., Depth of evaporation in the United States. Mo. Weather Rev . 16: 235-9. 1888. * *The instrument was first devised in its essentials by Babinet (Compt. rend 27: 529-30. 1848). It was later independently devised by A Mitscher.i.-h il.andw Ver- suchsstat. 60 63. and 61: 32'.1 1904) and by the writer (Publ 50. Cirnegie Institution. 1906). The literature of this form of atmometer is presented in Plant World 13; 111. 1910. On a modification of the instrument, see Transeau. E. X.. A Simple Vaporimeter. Bot. Gaz. 49: 459-60. 1910. t tAs has been later pointed out (Bot. Gaz. 191 1). evaporation from the white clay cup is not influenced so much by sunshine as is transpiration from green leaves. Thus the results here reported do not adetjuatcly include the influence exerted by sunshine. But. since the regions of highest evaporation intensity are usually those of greatest solar illumination, our records may probably be considered as showing at least the correct order of magni- tudes, even if the influence of sunshine be included. 208 The Plant World. of the installation of the instrument have been presented in a paper on ' ' Evaporation and Plant Development, ' ' (Plant World IJ: 269-276. 1907), and need not here be repeated. At the end of the season the porous cups were returned to Tucson and there standardized, the readings obtained by the observers being afteiward corrected according to the coefficients thus ob- tained. The results of this series of observations have been pub- lished in the author's article upon "Evaporation and Centers of Plant Distribution,'" {Plant World, 11: 106-112. 1908), on page 110 of which will be found a table showing the 'Relative evaporating powei of the air at 16 stations in the United States, June 3 to Sept. 30, 1907," together with the names of the observ- ers who so kindly co-operated, and thus made this work possible by attending to the instruments. These results were unsatisfactory and inadequate to our purpose, one reason for this being the smallness of the number of stations, so that anything like an evajwration chart of the country could not be attempted therefrom. An attempt was, however, made (in the last article cited), to draw tentative comparisons between the intensities of evaporation for the re- gions occupied by three of the vegetation centers, and the corre- sponding rain-evaporation ratios for the entire year as these were derived by Transeau (1905). Since typographical errors rendered the conclusions fiom this comparison obscure, they may be repeated here. We may take, from Transeau 's map, the annual rain-evaporation ratios: 1.25, 1.05, and 0.20 as representing approximately the regions occupied by the north- eastern conifer center, the deciduous forest center, and the south- western desert center, respectively. Considering the first ratio as unity, this series of ratios becomes 1.00, 0.84, 0.16. From our own data we derive the generalization that the dif- ferent evaporating powers of the air for the summer of 1907, for these three centers should be about 1.00, 1.16, and 2.86, respectively. The reciprocals of these numbers give us 1.00, 0.86, 0.35, to compare directly with 1.00, 0.84, 0.16, from Tran- seau. The agreement between 0.86 and 0.84 is surprisingly good. The discrepancy between 0.35 and 0.16 means little A Study of Kvaporation and Plant Distribution. 209 when taken with the data for the following year which are to be given below. The data derived in 1907 were so satisfactory, and at the same time so incomplete, that it was decided to continue the operations through another season. Steps were accordingly taken, with very helpful suggestions from Dr. H. N. Transeau, now of the Pvastern Illinois Normal School, and with Dr. h'orrest Shreve, now of the Desert Laboratory, to increase the number of stations and otherwise improve the character of the results. The writer's absence from the United States during the year 1908 would have made it impossible to secure a series of obser- vations for that summer, had it not been for the hearty and efficient co-operation of Dr. Shreve, to whose enthusiasm and perseverance the 1908 results are entirely due. Dr. Shi eve took complete charge of the operations throughout the season. In this series, the results of which it is the purpose of the present paper to report, two standardized porous cups were sent to each observer at the beginning of the season. These were installed side by side, each placed as in 1907, and weekly readings were made on both until mid-summer, when one of the cups was returned to the Desert Laboratory and restand- ardized by Dr. Shreve. This restandardized cup was then re- turned to the observer, by whom it was again installed in its old position, and operated with its mate till the end of the season. By this method determination was made possible of the amount of variation occurring in the correction coefficients of the various cups, without at the same time interrupting the series of obser- vations. At the end of the season both cups were returned to the Desert Laboratory and all were standardized by the writer during the spring of 1909. All standardizations in this series were made with reference to standard cups, the standard being directly or indirectly derived from the original standard of the fall of 1907. It is this same standard to which all coefficients derived since that time have been made to refer. It will be remembered that the reading of any cup is to be multiplied by its coefficient of correction, to give the reading which the stand- ard cup should have given for the same time and place. Where the coefficient of correction of any cup altered, as shown by the mid-summer and final calibrations, interpolations Til o Q O PS H (k. H S O ;z: Pi t> Q O V E d CO o (N 00 >0 oc 00 o 00 o 00 tn o < I-" tn Q W Q a o u w oi en tn W H < Pi o H < Pi O P. < > w > J i4 W w & z < a. 00 t/3 Pi o -t-t E O lb oo o t^ U k" .—1 bi) B 3 ^ I- * < o W o R H O C- S w H I/l < o . H- ( a. f-l c D >o ro W o fs ►-I tn > bi) 3 PQ t> < < < O s o , H O o E o H EC Pi f- i« 3 W 1— > > w • m w ON (N a 3 n c E u o ■4-» c ■4" vO o o fN o rn o On CI o >— < z: >*i rt c 00 to o OO o rO CN 03 C Sf &H K c o On fO On On o N£) NO 00 NO W3 c a! C o c 5 E N o m o o On On CN NO CN >o ON HI 'So C pa P NO 00 ■>4< 00 CN O ON 00 J2 On O' CN 00 On (N o o xf CM O CnI 1^ CI r o O ^ O, C u, 0:^ CO ON fO to fO On O o o »o o VO 00 < c o o 3 H I 1 E H 00 00 o o o E C5 vC »o >n u vO O o o Ml o (4 CN O t^ (N > ^ VC o c ly- CJ 00 (^ 00 ■* u "-■ ■^ (^J — ' (VI 00 (N o ^ f o C X c a % (« s O lO X X cj 00 vO vO fo u ■-" lO (N '- o C o VO O VO X VO CN o en CO CN 't VO rr> ^^ (N X u a 3 "a; 2: V. _d E ca C . 2 O C3 X n z "rt c7 •«^ "o rv^ _(U u -.-' C3 O U c" is J3 OJ a. u ►— * , 7 W 0 ry* N-i C o 1 W 2 **-! rt c tc _- rt ^^. 0 5 "S ^ o k- XIX n Q 0 z Ui * ■Jl . ri •o c C •^ c ^ J2 rt o •s. _n s w •V^ - 1u 2 "o S E ^^ x » S tZ ^ s ^ z > > O •^ 4J >-. S X ^ G < b ^ < f »• o ■ --s ■-J x E ^ T^ c < c J N-1, c fe •<». ',J '3 i^-x O c c •^^ U s 0^ S C ^ •«-» 11, rt S i3 W ii 1-^ U2 O 00 00 o c O c r- c ,— o be t-i < c o o c (N 00 fN 00 (N C c o 00 o 00 in bJo < C o o 00 c o o o ^ f>. O 00 fo o o o bJ9 3 < O o o "f C X lO fN c:^ o ^— ^^ (N ^ to c vu U rt ^ C tr ■r- 0 « o m O X ^ 3 o i u '7, O < C C xi o c" ui c C/l' c ■■J 3 5 'J 3 8 ,** J >< 3 3 '3 CQ > 5 < > cS 3 0 X C3 0. «J-i u 3 o o *- ^ 3 CL, 7; O 00 (N 00 c o 00- o O ID rM O O O be 3 C CI u r-j X ■* rf c c a J M < < c > «k J C C '-I 'v^ k^ W^ '-^ n o c o > c -r I-. O i- "^ >- '■'' o 2; W > 2: > 2? cr> o O o C o (A ■o 3 rt 5 C 214 The Plant World. were made to derive probable coefficients for the different weeks intervening between calibrations, it being borne in mind that where two cups are in operation side by side, their weekly readings constitute a continual series of measurements of the fluctuations in their coefficients with reference to each other. After the derivation of the coefficients, all readings were corrected and the resulting pair of records (where two cups had operated simultaneously at the same place) were averaged to give the corrected rate for each week and station. Thirty-eight co-operators in the United States and Canada were provided with instruments. Accidents and interruptions of various sorts occurred, so that the final records are not nearly all complete, but an excellent series of weekly rates was obtained, thanks to the careful foresight and persistence of Dr. Shreve and to the general efficiency of the co-operators at the several stations. There was consideiable variation in the date of ori- ginal installation at the various stations, and some in the date of discontinuance. For the majority of the stations, the avail- able series of readings extends over a period of fifteen weeks, from May 25 to Sept. 7, 1908. In order to indicate the general change in evaporation intensity as the season advances, and not to complicate matters by too much detail, the corrected weekly rates have been averaged in three groups of five weeks each, the averages thus obtained roughly corresponding to the three sum- mer months. The three five-weeks averages have again been averaged to obtain the mean weeklv rate throughout the season. These averages, together with the names of the various stations and of the co-operators, are given in Table I. The superscript figures after certain averages denote the number of weeks, if not five, and the number of five-weeks periods, if not three, from which the average is derived. Since measurements of evaporation have heretofore usu- ally been made in terms of linear xmits of depth, the averages from the porous cup atmometers have been reduced to centimeters and inches, and these are also given in the table. In this con- nection it cannot be too strongly emphasized that no unit of evaporation is of any value unless the surface from which evap- oration occurs is accurately defined, (see Plant World 13: 115 1910). In making the reductions here presented, our standard A Study of Evaporation and Plant Distridution. 215 water surface has been that of a nearly l:emis]:)herical copper pan 25 cm. in diameter and 12 cm. deep, filled to within 3mm. of the edge at each daily reading. It has been found that the standard porous cup loses one cul)ic centimeter of water for each 0. 1416 mm. of de]:>th lost by this pan, indoors and under sum- mer conditions at Tucson. 'This constant proved to be 0 137 for the conditions of June, 1909, when the two-foot pan used bv the Weather Bureau at .Salton, California, was taken as standard for depth measurements. Inasmuch as different pans of water, under different conditions exhibit different relations in their rates of water loss, not only to the losses from the porous cup but also to one another, there seems to be no advantage in con- sidering evaporation measurements in terms of dejDth, and the criterion in terms of cubic centimeters of loss per time period NWCc-.r 1-: i V....C...... L-iil c~ ..lhi±!i Dcc.ix.ou* L_ ] D..^ L_] NECo-.r br_=,J c..^. l^f';■''?^ S EC.r — ^E3 Figure 1 from the standard porous cup is as satisfactory as any other. This is especially true when we consider that the cup be- haves, as far as the evaporation of water is concerned, more like a plant than does a free water surface, and we are here pri- marily interested in the evaporating power of the air as it affects plant transpiration. To obtain a clear picture of the geographical variations in the summer evaporating power of the air, as brought out in the table, reference may be made to the four accompanying profiles (Figs. 1-2) and to the evaporation chart of the United States (Fig. 3.). The profiles aim to present graphically the changes in summer eva]:)oralion intensitv which would be en- countered in crossing the country from west to east and from north to south. The graphs express average weekly loss in 216 The Kaj^t WoRtb; cubic centimeters from our standard instrument (the names of the stations are shown above the base Hne, which rei~>resents a rate of 100 cc), and the amovmts fcr the different stations are placed upon the graphs. Below tl.e base hne are indicated, by conventional hatching, the ap]:iroximate distribution of the main vegetational types of the areas through which a profde passes. Here are considered: the northwestern, northeastern, and southeastern conifer centers; the deciduous forest; the more or less poorly defined belts of transitic>n between the latter and the two eastern conifer areas; a prairie belt or zone of transition from the deciduous forest to the grass land or plains region ; the grass land area; the California chapparal and the desert. Oui terms are general, our limits merely appioximate,and a host of smaller details explainable on the basis of variations in soil, altitude, etc., are here ignored. Information for our present purpose as to the vegetational typ'cs and their geograihical distribution has been obtained from an unpublished map pre- pared by Dr. Shreve, which he has most kindly placed at our disposal. The uppei diagram of Fig. 1 rej^resents a profile of the variations in vegetational types and in the intensity of evapoiation for the summer of 1908 along a line drawn from San Diego to Kaliegh, through Tucson, Dalhart, Stillwater, St. Louis, and Pisgah Forest, the latter station being in the mountains west f f Asheville, X. C. In this diagram the highest intensities cf evaporation are seen to cor- respond aluK st exactly with the limits of the desert region. The California chapparal occupies a strij) near the Pacific, with an a\erage"rate somewhat above 200 cc. per week. From Dalhart to Stillwater there is a raj id dow nward gradient in the summer evaporating power of the air, and the vegetation takes the form of jrairie, or grassland-deciduous forest transition, with an average weekly rate c^f from about 150 to 200 cubic centimeters. The change of vegetation to that of the deciduous forest, as we progress eastward, is not marked by any corres- ponding change in the rates of cxajjoration, St. Louis, indeed, seeming to pcssess a somewhat higher rate than Stillwater. With the very marked depression in the e\a})orating power of the air over the high land at Pisgah Forest, we have a marked A Study of Evaporation and Plant Distribution. 217 alteration in the vegetation, it taking almost the same form here as that of the northeastern conifer center. With the return to an average weekly rate of about 100 cc. tlic vegetation is again deciduous forest. Tlie lower profile, Fig. 1 , is drawn across the northern limits of the United vStates and passes into Canada. It extends fiom Seattle to Frederictcn, X. R., through Legina, Houghton, and Quebec. The station for the latter j^lace was MacDonald College, vSt. Annes. Although data for an indication of the limits of the different vegetational types along this entire profile are not at hand, it is clear that the highest evaporation intensities accompany the grassland vegetation (this profile does not traverse true desert) and that the lowest occur with either the nortliwestern or northeastern conifers. CoNtrcR-DcctD- t'"'T"''i"''H Swamps amb Mafbhis. llilll^'^'-^*li^|lM Otheti Types as on FonEQOiNt Protilis. Heci Camion Figure 2 The up er profile of Fig. 2, passes fiom Fredericton,N.B., to Miami, through Orcno, Ivaston, Raleigh and Gainesville. The most striking feature of the diagram is its evidence that the highest summer e^•aporaticn intensities occur with • the southeastern conifers or with the Florida marshes. The lower diagram, Fig. 2,is a profile from Regina,Sask,to Cam- eron, La., passing thiough Dickinson, North Platte, and Stillwater. The highest atmo metric rates, in the north, accomjany grass- land, being about 150 to 280 cubic centimeters, or above. The lowest rates, in middle latitudes, represent roughly the decid- uous forest or prairie vegetation; and the somewhat higher rates, at the south occur with the southeastern conifers. It is hardly necessary to disavow here any attempt at detailed accuracy in connection with these profiles; neither 218 The Plant World. may they be taken to represent what the writer might beheve to be the truth, but merely what appears from the Hmited data at hand. Everything considered, however, they probably do not go far wrong, and seem at least worthy of consideration in connection with the various non-quantitative theorizings and rather academic discussions of present-dav ecologv. The evaporation chart (Fig. 3) prepared from the fifteen weeks averages of the weekly water losses from the standard porous cup atmometer, may be taken to represent for the sum- mer season, 1908, the variations in the intensitv of evaporation over the United States as accurately as the data at hand will permit. The dotted portions of the isoatmic lines on the chart have been tentatively inserted by an interpretation of the humid- ity chart for the three summer months of the same year, data therefor being taken from the Monthly Weather Review. For some reason, impossible of defmtiton at present, the evaporation data obtained from Bozeman and Salt Lake City are apparently too low; no commensurately high humidity is indicated for these stations. They have therefore been neglected in the preparation of the chart. The most significant features of this chart are the following : (1) The Canadian region of low summer evaporation extends southwestward from Lake Superior, as far as the valley of the Arkansas River. It occupies the northern peninsula of Michigan but not the southern. (2 Another southern extension of the northern area of low evaporation intensity extends southwestward from southern New England and occupies the whole of the Appalachian moun- tain system south of Pennsvlvania. In the highest mountains, of North Carolina, the average weekly rate is shown to be lower than at Fredericton, N. B. (3) The valley of the lower Great Lakes is occupied by an area of exceedingly high summer evaporation, which ap- parently extends, roughly, over eastern Michigan, the penensula of Ontario, and the state of New York. (4) The southeastern coast exhibits about the same evap- oration rates as middle New England, \\estern ?klichigan, and the Mississippi-Ohio valley. A Study of Evaporation and Plant Distribution, 219 V -^ .^ CI u 3 220 The Plant World. (5) Westward from a line drawn from Winnipeg, Man., to Corpus Christi, Tex., the rate rapidly rises. The highest evaporation intensity is exhibited by western Texas and New Mexico, and this area is extended northwestward to western Washington, and westward to include the desert of southern California. (6) vSan Diego appears to have about the same rate as New York state. From the information here brought forwaid, the evapora- tion rates for a single summer, any attempt to relate plant distribution to this factor in any but a verv superficial war would Vje imfounded, but it is aj^parent that the northwestern and northeastern conifer vegetational centers are characterized by average weekly rates of less than 150 cc. from our standard instrument, — i erhaps about 100 cc. would be a truer limit for the northeastern center. The well-known southern prolongation of the northeastern center in the eastern mountains is clearlv paralleled on the evaporation chart. The deciduous forest of the middle east occupies a region with over 100 cc, often over 150 and even 200 cc, as the mean weekly summer rate. The southeastern conifer center occupies the southern part of the evaporation area which is characterized bv rates of from 100 cc. to 200 cc. Summer evaporation alone can not explain its exist- ence as a distinct vegetational type. The geneially cultivated area of Oregon and California appears to have summer rates of 150 cc. to 200 cc. ]:ier week, and the great arid region is clearly indicated by our atmometric data. The piairie region appears to be climatically a potential deciduous forest, as is suggested bv the success which has attended tree planting in Iowa, eastern Nebraska, eastern Kansas, etc., as well as by other considera- tions. The grassland represents the transition from the evapor- ation conditions of the deciduous forest center to those of the arid region. It will be interesting to apply the method used in 1907 to the evaporation rates as exhibited by the northeastern conifer, the deciduous and the desert regions for the summer of 1908. Inspection of the map leads us to set the average summer (1908) eva])oration rate for the northeastern conifer area at about 100, that for the deciduous forest at about 1 75, and that for the desert A Study of Hvaporation and Plant Distribution. 221 region at about 350 cc. per week. The reciprocals of these rates are 1.00, 0.57, 0.29, to compare with 1.00, 0.84, 0.16, from our summer approximations of 1907, and with our approximations from Transeau's annual ratios, 1.00, 0.86, 0.35. It is ai)parent that the agreement between the annual index (from Transean's ratios) for the deciduous forest center (the index for the north- eastern conifer area being assumed as unity) is in much closer agreement with that for oar first summer approximation than with that for 1908, while the annual index for the desert region agrees more satisfactorily with our summer index for 1908 than with that for the previous summer. Such a condition seems to exhibit the low degree of detailed accuracy which may be possessed by any method which depends upon climatic data for a single year; it is practically certain that such indices as we have used must fluctuate between wide limits in difl'erent years. Transeau's ratios, while calculated form the data of mean annual precipitation based upon observations for many years, also involve the evaporation rates for a single year, as obtained by Russell in 1887 and 1888, The time for nice quantitative distinctions and critical studv in these matters has obviously not arrived. From the above general deductions it is apparent that the summer evaporation intensity alone furnishes a climatic criterion for studying the different vegetation centers with which we have to deal at least as promising as the ciiterion furnished by any other meteorological element. Summer evapoiating intensity while exhibiting relations not in detailed agi cement \\ith those shown by the annual rain-evaporation ratios of Transeau, may be considered of as great promise in this general problem as are the latter; the fact that the annual ratios and the two series of summer data are all for different years might give as discordant results as we have obtained, even though the mean intensities for an adequate period of years might still show agreement. The summer data, especially if obtained by some such means as ours, offer much less difliculty in their derivation than do those used for the annual ratios, so that theie may be more hope of getting an adequate series of them to extend over a number of years. The importance of the relative intensities of evaporation, to ecology and agriculture, are only surpassed by the present 222 - The Plant World. dearth of informatiDn in this connection, and it may be regarded with some sur]:)rise that two decades intervened between the dates of the first and second attempts to prepare an evaporation chart of the United vStates. As soon as the fundamental prob- lems of agriculture attract public and scientific attention, it is probable that evaporation measurements may become a promi- nent feature in climatological and phenological work. The Johns Hopkins University. SOME BOTANICAL OBSERVATIONS IN THE MOUNTAINS OF WASHINGTON. A. S. FOSTER. The region in which the observations have been made which are recorded here, is a huge triangle,— or more nearly the face of a vast pyramid, — -the western edge of which is the Nisqually Glacier, the source of the river of that name, the eastern edge the Paradise Glacier, and its eastern lobe the Cow- litz Glacier, while its southern edge is formed by the summit of the Tatoosh Range, the highest peaks of which attain 6,500 to 7,200 feet altitude. Within this area are numerous mountain torrents, deep canyons, escarpments, snow fields, mountain meadows, orchard-like groves, springs and lakes. The Paradise River traverses the triangle, with a southwesterly course of some six or eight miles within which it falls about 4,000 feet, i)lunging over the rim of the snow field as Shuskin Falls, and further down dropping 150 feet in the beautiful Narada Fall. From what- ever part cf this area one may locjk there is a giand panorama of snow-clad peaks, including Mt. Adams, St. Helen's, and Mt. Hood. My visit to this region was made in the ten davs following August 3, 1909, during which time the atmosphere, usually clear, was made very smoky by distant forest fires. A month earlier the snow had been ten feet deej) in manv places, and large drifts were still to be seen in sheltered spots. Heavy frost occurred on every night excepting those on which a pene- trating fog enveloped the mountains. Botanical Observations in Washington. 223 The lower portion of this triangle it — or was not long since — a continuous coniferous forest in which the Douglas Spruce and Hemlock, Tsuga hcUrophyl/a, range ui)warcl and mingle with Abies lasiocarpa, Tsiicjti Mfttensiana and the less frequent Alaskan Cedar, Chamaccyl^arts nootkatensis. The chief under- shrubs in this forest are Vnccinium oialijolium, \' . dcliciosum, V. macrophyilum, Azalcastrum albiflornm and Menziesia glabra, while along the streams grow Salix Gcycriana and 5. ienera. Vaccinium ovalifolnim was in abundant fruit during my visit, and the Azaleastrnm in full ilower. The willows were just be- ginning to flower on August 4th, and by the 12th they were in full leaf. Common among the herbaceous plants of the forest Fig. 1 TIk' 1' Misqually river. 1 thi- Mi'(HU[ll\- t'Luic r were Pyrola rotundijolia, P. bracfcdta, Strcptopiis roseus, and GauUheria ovalijolia, while in the open timber Eryihromum montanum and Clinto}ua itiiij/oni were in full bloom. Poly- stichum munitum was found in these forests growing to a height of a few inches, in strong contrast to the indi\ iduals of this s])ecies several feet in height that had been observed at lower altitudes. Xear the Xarada Falls Piuiioptcris 'hyopteris was cf)mmon and also Cornns ccuuuh >im^, while at the bases of the trees the' liverwort Ptilidium L'(i/i/<'r)ii(ii)ii grew luxuriantly. All of the above-mentioned groups of plants may l)e found on the coast of Washington, where the climate is moist and never very hot, and here thev reappear in the higher mountains near the transi- tion from the Canadian to the Hudsonian zone. 224 The Plant World. On climbing out of the valley of the Paradise P.iver one comes into stretches of open park-like forest with a floor of mead- owy character. Over this regie n heavy snowfall often occurs as late as the first week in July, while at the Inn at 5,820 feet altitude frost occurs on every calm night throughout the summer. On the morning of August Sth we observed plants of Xerophyllum tenax, Pctlicu/dyis bracfeosa and R(tnn7ici4lus Suksdorfii which had been thawed Ijy the early morning sun and were limp from frost. Tlie cc^ld air currents that flow down -the mountain slo})es during the night are followed b\- midday temperatures of 7.S degrees to 80 degrees, changes which follow so rapidly FiE 'I'suf/a Xlei Icnsiaua and CItamaecyparis iioolkatensis near timber line that plants frequently perish for lack of water. The principal trees in these park-like forests are the Fir and the Hemlock. They reach a height of from fort\- to eighty feet, and branch from the gnuuid up with a spread of limbs of no more than ten feet, Tliesc trees commonly grow in groups of four or five to fifteen or twent\-, and tliis habit is also characteristic of the shrubs; including Pi;?/r occidrntn/i\. PhyJIodoce empetriformis (the red heather), I'achisiima myrsiniies, and Spiraea densifiora. The Willow r f these altitudes, Salix ienera, and the Alder, A/nu.'^ \nuiat(i, are found only in the most favorable situations. One of the hardiest of the herbaceous plants is Pulsatilla occidentalis , Botanical Observations in Washington; 225 which has a large root system, and is one of the earliest plants to break through the remaining crust of snow. When three or four inches in height it blooms, after which a single very toment- ose leaf is developed, followed successively by another flower and a second leaf. Along with the Pulsatilla grow Lupinus Lyallii, Polygonum bisiortoidcs, Scnecio triangularis, Oxyria digyna, Epilohinm alpinum, Lcptorrhina amplcxifolia, Poa alpina, and numerous other grasses, sedges and junci, all ex- tremely depauperate in size. Fig. .■?. The Tatoosli Range a>; seen from Paradise Park. In Uie foreground Tsuga Mertenstana and Alris lasiocaipa The effects of wind and snow on the vegetation are ex- tremely manifest at these higher altitudes. What the greatest depth of snowfall is I was unable to learn, l)ut all of the herba- ceous plants of the ])receding season are pressed quite flat to the ground, and moreover show the down-hill movement of the snowbanks. Indeed the largest trees are seldom without a crook at the blse resembling a sled runner, and doubtless due to this same cause. The winds, strong even in summer, are re- 226 The Plant World. sponsible for the procumbent habit of many plants. Juniperus communis is common on the ridges, and may often trail the ground for eight or ten feet without reaching a height of that many inches. On the peaks and ledges at 7,000 to 8,000 feet the Alaska Cedar is only semi-erect or completely prostrate, growing in crooked, gnarled form, with a spread of twice its height. Only two specimens of Piniis albicaulis were seen, both of which were dwarfed, although this species reaches a height of ten feet on Mt. Hood at these altitudes. Even such herbaceous plants as Phlox diffusa, Leutka pectinata, Pyrola stxunda, and Poa arciica are found onlv jirostrate in habit on the ridges and wind-swept ledges. The southwest wind of summer is responsible for small sand drifts, which are colonized by the shrubs and trees, while the snow movements of winter accumulate beds of shale in which I have found Empctruui nujrum, Pedicular is raccmosa, P. bract- eosa, Aster integrifolius, A)itcn)iaria rosea, Saxijraga Bongardi, S. Tolmiei, and Phyllodoce glandulijiora. The surface of the larger rocks is covered with the crustaceous lichen Lecanora joveolaris forma dealbata, and in the crevices of the rock grow Pentstemon Mendesii, P. procures, Sibbaldia procumbens and Saxijraga odontoloma. Pinnacle Peak, 7,200 feet in altitude, was scaled on August 7th, and on this highest point in the Tatoosh Range dwarfed Alaskan Cedars were found in the crevices of the rocks, and about them a very interesting assemblage of j^lants. Among these were Linnaea americana, Erigeron aureus, Sedum divergens, Cheilanthcs Feei, and Cryptogramma acrostichoides, the last of which also grows among the cobbles of the beach at Seaside, Oregon. Among the lichens which endure the tremenduous range of conditions on this peak are Parmelia lanata, P. tristis, P. siygia, Gyrophora hyperborea, G. vella, Cetraria icelandica, and C. Fahlunense. Also of great interest in the crvptogamic flora is the Red Snow, Sphaerella nivalis, which frequently turns the remaining banks of snow a brilliant red, giving a verv pleas- ing touch of color to an otherwise austere landscape. On the more exposed slopes where the wind i)revents the heavy accumulation of snow and the sun first melts that which remains in the spring, the vegetation is heavier and more varied Books and Current Literature. 227 than elsewhere. The level depressions are also heavily covered with grasses, sedges, and rushes. A number of interesting ferns, mosses and lichens were found in these situations and in the so-called "pumice fields." Among the debris of the slides in the pumice fields were found Polytrichtim pilijcrum and P. gracile, and in the midst of the larger boulders of the lateral moraine of the Nisqually glacier Polytrichadelphus was discov- ered, a rare alpine form. The sharp angles and edges of boulders in ojieii situations are colonized bv Buellia geoqraphica, and with it &rimmia M iihlenbeckii is extremely common. \\ e also found Rhacomiirium Macounii on wet ledges of rock about the boulder fields, and Rhacomiirium has also been collected in this vicinity. Immature specimens of Gyrophora were collected at Gibraltar Rock, altitude 12,000 feet, and Placodium eleqans at Camp Muir at 10,000 feet. Indeed, this is practically a \ iigin field for the brvologist, and among the thirty-five species which I collected fNere such rare forms as f:iistichia Norvegica and Pseudoleska radicans, and the Arctic forms Andreaea alpestris, Grimmia ovata, and G. manniae. Some fifteen species of liverworts were collected also, including Jungermannia Allenii, Nardia Brideleri, Hygrohiella laxijolia, Marsupella Sullivantii, and Targionia hypophylla. Among the ferns some seven forms were collected, including, in addition to those already mentioned, Polystichum, tonchitis and Poly podium hesperinum. Such a rich and diver- sified field well deserves more thorough exploration. Paciic Beach, Washington. BOOKS AND CURRENT LITERATURE. (lEOGUAPiiicAL Studies in Palestine. — Students of plant geography are greatly indebted to Professor Hunt- ington, of Yale University, for his extended studies of des- ert conditions in connection with climatic changes. In the course of these changes, whether in historic or prehistoric times, there can be no doubt that the plant life of various arid and semi-arid regions of the earth's surface has under- gone profound modifications, but our know ledge has hither- 228 The Plant World. to been so inexact as n'oai'ds the actual climatic couditioas even of relatively recent periods, — say from two to thr^iC or foni' tlionsiind years a^o, — that any correlation of the piienoMiena of i»lant h dej^ree of uncertainty. There is no doubt that when the data are all in the problem will still present many, in some cases possibly insuperable, difficul- ties, but it is certain that in such work as Dr. Huntington has been doing in Central Asia, in Palestine and in the south-western United States the foundation has been laid for a far more definite knowledge of the phytogeogeography of these regions from a historical point of view than has hitherto been attainable. His work on Palestine* is a specially noteworthy contribution in that, as pointed out by the autlior, clinuitic variations (with consequent changes of vegetation) would there produce notable varia- tions in habitability, while at the same time its known his- tory extends back to remote antiquity. Such a study as this, therefore, which was carried out by the Yale Expedi- tion in 1901), might reasonably be expected to throw a con- siderable amount of light on the problem of climatic (and therefore vegetational) changes in Palestine during the period covered by recorded history. Although many, perhaps a majority of geographers and historians assume that climatic changes within this period are of negligible importance, the author shows, as it seems witli convincing proof, that the climate of the region inves- tigated has been subject in the course of the past five thous- and years to numberless changes and that these have been a potent factor, — largely or chiefly through their effects on vegetation, — in the guidance of some of the greatest his- torical movements. Omitting through sheer necessity all discussion of this most fascinating part of the work, refer- ence may be made to certain facts of special interest to students of plant geography. •Hunting-ton, lOllsvvnrtli Pal^stinp nnd its Transformation. Houghton, Miff- lin & Co., Boston and Kew York, 1911. Books and Current Literature. 229 American botanists who are familiar with tho south- western I'nited States will be interested in the striking romi)aris()n of I'alestine with southern California. In the latter, from Los .Vnjicles fifty miles north-eastward across the mountains to tlic Mojave Desert the same mai-ked and rai)id chanucs are observed as in the same distance from the Meriditerranean to the Dead Sea. ''The immediate coast of California is cooler than that of Palestine .... but the orange «»roves at the foot of the mountains corres- pond to those of Jaffa, tlu^ urain fields in the u])land valleys are not unlike those of Judea and the ^lojave Desert at the eastern l)ase is of the same ty])e as that which surrounds the Dead Sea." What southern California would be without irriuation may be jdctured in part from the ])res(Mit cimdi- tion of Palestine. The latter country, like the former, lacks summei- rains, and if the winter rains are either late in be binnino- or cease too early, a famine is the likely re-^ult. The inevitable outcome of such untoward conditions, which as sh(>wn by the author liavc become greatly accentuated within the historical period, is seen in a gi-eat decrease of productivity of the soiL the disappearance of olive orchards and vineyards from the terraces they once occupied and the loss from the landsca])e of noble oaks and other trees that J,^^V(' the land so mncli of its beauty in the days of psalmist and prophets. Tlie evidence foi- these concjusioiis is cumnhilive, and those who would feel its full f(U'ce must follow the author in the ,<»ra]»hic story of his joui-neys from the Dead Sea and the Neireb to I^ebanon and ]*almyi-a, and in bis masterly pre- sentation of jthysical and iiistoi-iral data. T<» tliose who have read "Cosmos," or any other nionnuiental "shy at the universe," with resultini: weariness; of soul, or h iv > found it an unjirateful task to read "The Laud and ilie ISook" and other works which us<' the jdivsical features of Palestine merely as contii-mation cd" biblical nari-ative, this ]»ook of nnntiniiton's will prove a double treasure, i-iiiidly scientific in its methods and conceptions and at the same time broad- ly hospitable to every form of truth that history or tradi- 230 The Plant World. tion have broiijilit to lijiiit. r>otanists who hare occasion to draw ronclusioiis rcoardino plant life in arid or semi-arid re.ii'ioiis will tiud it es^icntial to become conversant with the antlior's arjinments and couclnsions, which seem likely to lead to important modifications of doctrines that have been wid(dv h(4d ami tanu'ht. — V. M. Spalding. NOTES AND COMMENT. Tbe resnlts of a carefnl examination of the histolooical relations of ('u.sciitd and Sement ])robably disturbs as little as possible the n«)rmal me(dianics of the sieve tubes of the host and ensures for the jiai-asite a lonii-continued supply of nutri- ment." I'nrther "That the i)arasite takes so much trouble to nmke nse of ilie host sieve fields as they are, and not to distni-b the meidmnics of the sieve tubes, is important testi- mony in favor of the functional etiiciency of sieve tubes in general and sieve fields and sieve plates in particular." Tlie^e statements are abundantly refreshinu; both as to lit- erary construction and as to scientific point of view. The actual work on which they are based was well planned and lacks m)thin_ij as 1o thoroughness and exactness. The advance of knowledue concerninn- hydrolysis and kindred processes has made ])ossible a substantial addition to the onrlier results on the subject, ])ublished by Peirce in 1893 ami 18!)4.— 1). T. :\r. Professor Adolfe Prunet, Associate Director of the Agricultural Experiment Station of the University of Tou- Notes and Comment. 231 louse, has been attompting for several years to work out uu'thods for attacking problems in plant patbob\iiy that wonhl fnrnish a sonnd, sciciitirtc basis for cb'aliiig wilh plant diseases. A suuiniary of his "method echelounee" was presented before the French Academy of (Sciences (12 June, 11) Uj. In studying the lUack-rot of the grape-vine, he divided the fields in which the experiments were to be made into a number of lots, each with one or two vines. As soon as the vonnji- leaves beor«leaux mixture, and each day (or every other day) after tlmt one lot was sprayed. The dates of the ap- l)lications were recorded, and the first appearance of the black-rot was noted. In ISDIJ this was on the IGth of .May. Every lot had been sprayed; those that had been sprayed between the 19th and iJotli of April escaped the disease; all the others were attacked. The ])lants treated between these t\No dates escaped because the treatment ju'^^vented the germination-tube of the black-rot spore from entering the leaf. The applicatiim after the 25th of April was not ellicacious lu'cause the infection was already complete. This method allows the exi)erimenter to determine the date of the infection and duration of the incubation period — that is, the time between the entrance of tlu' fungus into the leaves and the breaking out of the rot upon the surface. The stages in the (levelo[»m(mt of the jiarasite upon the host u[» to the time of spoi-ula(i(tn were also marked off by this method, and Ihese stages were then c. ( \ Guuknberg. We are in receipt of the first issue of The Journal of the W'dfiJiiiigtoii Acadvniji of Sciences, a semi-monthly pub- lication devoted to brief articles and to abstracts of work done bv men in the scientific bureaus of the government. The Journal is ai)pa]'ently destined to fill such the same place among physicists and chemists that The Experiment IStalion h'ccord does among botanists and agriculturists. It does not fail, however, to contain much that will interest b(>tanists in its abstracts of work in forestry, meteorology, I^hysiography and paleontoh)gy. In these da.ys we natural- ly crave the journal in which the contributions are short and to the point, and in which the reviews and abstracts are numerous and are discrinunating as well as informing. Volume 14 Number 10 The Plant World A Magazine of General Botany OCTOBER, 1911 SOME ALASKAN AND YUKON RUSTS. J. C. Arthur. Very little is known of the uredineous flora of Alaska. The most extensive series of specimens yet reported is that made by the Harriman expedition of 1899. Forty species were listed,* largely collected and determined by Dr. William Trelease, Director of the Missouri Botanical Garden. All but two spec- ies (three collections) of the list were secured along the southern border of Alaska and the Aleutian Islands. The two exceptions are Puccina laurentiana Trel., on Saxijraga, and Melampsora aipina Juel, with I on Saxijraga, and II (III) on Salix (the I being listed as Caeoma saxijragarum) , both obtained from the northern part of Bering sea. Besides this series only occa- sional srecimens have come to hand in various ways, and prac- tically all from along or near the southern sea-coast. During the summer of 1909 an extensive collecting trip was made through the interior of Alaska by Prof. A. S. Hitchcock, agrostologist of the U. S. Department of Agriculture. Although devoting his attention primarily to the grasses, he secured a few excellent specimens of rusts, which he kindly turned over to the writer for stud\-. All, with two exceptions, the aecia on Rihes and uredinia on Ledum, belong to species not listed by Dr. Trelease in the Harriman report. Only three locahties are represented by the collection, but these three localities are long distances apart and are typical of as many highly distinct climatic regions: the temperate region along the southern sea- coast, the interior arctic region about Dawson, and the coast arctic regie n near Berirg strait. Itisnoeworthy that none of the species ♦Alaska: the Harriman Expedition 5:36-41. 1904. 234 The Plant World. can be said to be strictb/ arctic, although mostb/ preferrin-j boreal or mountanous habitats. The following is the list of species, given in regional groups. 1. Southern Coast Species, collected at Sitka, June 21, all in the aecial stage onlv. Picccinij Grossuliriae (3chum.)Ivagerh. (i^ciiiun Gros- ndariae Schum.), on Ribcs laxifloriim Pursh. This is probably one of the racial forms belonging to the abundant cosmopoli- tan rust with telia on various species of Carex. The exact status of the form must await knowledge derived from cultures. vSimilar collections have been made along this coast by a number of collectors. Puccinia Veratri Duby, on Epilobium adenocaulonliansskn. This heteroecious species, cultures of which were made by Tranzschel in 1908, has not before been reported north of Glacier, B. C, for either aecial or telial stages, the latter being on species of Veratrum. Aecidium sp.,on Petasiies jrigida (L.) Fries. The host was determined by Mr. W. F. Wight, November, 1910. This rust is seemingly identical with the aecia on Tussilago Farfara, which is known to be the aecial stage of Puccinia Poaruvi, hav- ing telia on species of Poa. Repeated trials by Tranzschel, however, have failed to infect Peiasites officinalis by sowing teliospores from Poa. This does not preclude the Alaskan rust from belonging to the Poa combination, nevertheless, for the habit and texture of Peiasites jrigida are much like those of Tussilago Farfara, while P. officinalis is a quite dissimilar plant. Other collections of the same rust have been made in Alaska on Peias- ites corymbosa (R. Br.) Rydb. by J. M. Macoun at St. George Island in 1891, and by C. V. Piper at Kadiak in 1904. 2. Interior Arctic Species, collected July 17-19 at Dav-son, Yukon territory, a little north of the 64th parallel of latitude, and about 300 miles from the southern sea coast. Dawson is close to the eastern boundary of Alaska, and less than 150 miles from the Arctic Circle. Its boreal and interior ( osition give the collections unusual importance, and especially as these are the first rusts to be recorded for all this great in- terior territorv, so far as the writer knows. Some Alaskan and Yukon Rusts. 235 Puccinia rubefaciens Johanns., on Galium boreale L., a rust common to both hemispheres. Aecidium Allenii CUnt., on Shepherdia canadensis (L.) Nutt. This is a heretoecious form of wide distribution in North America, and probably belongs to some grass rust, indications pointing to an unnamed form on Calamagro^tis, Agropyron and Bromus, hut no cultures have yet been made. The most northern station heretofore known for it is Banff, Alberta. Mclampsora RihcsH'Salicum Bubdk (Uredo conJJuens Pers.), II on Salix glauca L. The host was determined by Dr. F. V. Coville, November, 1910. This is probably a common and widely distributed species, but very few sporophytic collections can be referred to it with certainty. It is a mountainous form extending through a wide range of latitude in both the Old and New World. The specimen in hand is scanty, but seemingly characteristic. Melampsoropsis leduola (Peck) Arth. {Chrysomyxa ledicola Lagerh.), II on Ledum groenlandicum Oeder. This abimdant American rust has been collected on the same host in Greenland (in 1886), and at Fort Wrangell, Alaska (in 1883, by Thomas Meehan), and also on Ledum palustre at Turnavik island, Labrador (in 1896, by the Cornell-Peary expedition), and at Virgin Bay, Alaska (in 1899, by Wm. Trelease of the Harriman expedition). It is evidently a common Arctic species, ranging south to the northern border of the United States. Peridermium boreale Arth. & Kern, on Picea candensis (Mill.) B. S. P. This little known and ill defined species has not be- fore been reported north of Banff in British Columbia. The leaves on the specimen have fallen from the stem in drying, but otherwise the collection is typical of the species. 3. Ccast Arctic Species, collected between Aug. 20 and Sept. 1 at Nome, less than a hundred and fifty miles south of the norrowest part of Bering strait. This is within the region from which Puccinia laurentiana and Melampsora alpina have been reported as mentioned above. Puccinia septentrionalis Juel.IIand III on Polygonum vivi- parum h. This species has also been found in Newfoundland by Rev. Waghorne, and its aecia, which occur on Jhalictrum alpimim, were collected July 28, 1904, at Kadiak, on the southern 236 The Plant World. coast f'f Alaska, by C. V. Piper, no. 4474. These are the onlv Ainerican stations so far definitely known for the species. Puccinia Gentianae (Str.) Link, i. III on Gentiana frigida Ilaenk. The specimen is especially interesting as it shows a few veil developed aecia and an abundance of telia, while no uredinios'^ores were to be found. The microscopic characters agree with more southern collections in which urediniospores are usually in the majority, but the aecia rare. Puccinia ? sp., II on Arctagrostis ariindinacea (Trin.) Beal. This rust in its uredineal form is so much like Puccinia pyg- maea Erikss., on Calamagrostis epigeii, occurring in Sw^eden and Finland, that it would have been referred to this species but for the following reasons: The uredinial sori of this species are much larger and more conspicuous, being darker in color, than those of the European form; they are also amphigenous, while the European form is chiefly on one side of the leaf. The urediniospores in the American form have somewhat thicker walls, and somewhat more numerous and far more evident germ- pores, than in the European form. The paraphyses are also strongly capitate and much thickened above in this specimen, while in the foreign ones they are chiefly clavate with a wall of practically uniform thickness throughout. These dift'erences, and the total absence of telia, make it unwise to list the collection as Puccinia pygmaea, although it seems to be closely related, possibly the same. It is the first collection of the kind from America or elsewhere. Purd^ie University, Lafayette, Indiana. CHANGE OF ASPECT WITH ALTITUDE. J. C. Blumer. The striking dissimilarity of the species growing upon two slopes opposing one another in the general direction of a merid- ian is well known, because easily observed. Much more elusive is the fact that the same species changes its aspect, or slope- exposure, from north to south in rising from its lower to its Change of Aspect with Altitude. 237 upper altitudinal limit. In a previous paper * the writer noted the behavior of Lippia wrightii in this respect. Since then other species of the desert mountain ranges of Southern Arizona, have been found to exihibit the same distributional character. The second plant found to behave similarly was Calliandra eriophylla. On Tumamoc Hill, near Tucson, this dwarf shrub is found sparingly in places of good soil moisture conditions, preferably on north aspects. It is more adundant on rocky north slopes in the foothills of the Tucson mountains, associating with Selaginella. One thousand feet higher, as for instance near the Sierrita IMountains, and in similar country of the same altitude elsewhere, it spreads abundantly over the plains and foothills. Rising another thousand feet, it was found in the Oro Blanco Mountains on the timberless south side of the high hills, often coming well down into the oak scrub, but leaving the opposite side to the oaks. Similarly, at the same elevation of 4,500 feet in the Santa Rita IMountains, it is associated with Mimosa dyscoarpa on a slope falling southward into Sawmill Canyon, while the north side of the ridge is given to the oaks and Nolina. The herbaceous perennial Perezia wrightii is found on the north slopes of Tumamoc Hill at an elevation of 2,500 feet, a closely related plant (P. thurhsri) was found in the Chiricahua Mountains at 5,800 feet elevation at the southern base of a cliff. Equally infrequent as in the preceding locations, the latter was encountered in the Rincons at 4,900 feet on a west slope. Although annuals are frequently of wider vertical distribu- tion than perrennials,and not so closely limited to special habi- tats, a similar case appears to be found among the former in Lupinus kptophyllus. Near Tucson it is abundant on the north side of Sentinel Hill, but absent from the south side. In the the Oro Blanco Mountains, it was seen growing on the south side of mountains near 5,000 feet, and collected on canyon bluffs of similar aspect at about 4,000 feet just acrosss the Interna- tional Boundary. In the Santa Catalina Mountains, decending from Oracle Ridge on the Leatherwood Trail, on a slope of schistose granite, the physiognomy of the forest growth on a protected southerly ♦ Plant World, XI, p. 117, June, 1908. 238 The Plant World. aspect is si:nil.ir U) that <>f a mf)re open, easternly one a few hundred feet fa -ther down. An open forest of the Arizona pine is imdergrown \vith whiteleaf oak {Ouercus hypoleuca), a tall, viv^orous shrub, and someti'Ties a shapelv tree as high as fifty feet. A few netleaf oaks (Q. reticulata) and manzanita {Arc- tostaphylos pungens) are ]:)resent, and a rather large number of madrone {Arbutus arizonica) are conspicuous as tall shrubs or gnarled trees. The otherwise unoccupied interspaces are largely taken up by coarse mountain grass {Epicampcs ligulata) and low, thorn}' underbrush {Ceanothus fendleri). Where the pine stands more closely, Muhlcnhergia gracilis takes the place of many shrubs, and immediately across a V-shaped gully, with a northeast instead of southeast aspect, this grass and the pine have almost displaced the shrubbery and the other grass, and the transition is strikingly complete. This is but one example of what may be constantly observed in aspect relations, whenever the opposing slopes extend in a more or less east-vv'est direction laterally. We need only to climb 1,000 feet to the vicinity of Mount Lemmon, to find the same grassy pine forest of the above noted northeast gully slope on a mountain side facing in a south- erly direction. In the Santa Rita Mountains a number of the character- istic plants change their aspects between the lower and upper limits. In ascending by the way of Stone Cabin Canyon, net- leaf oak (Quercus reticulata) is first found in shaded gullies and strictly north acclivities at about 6,000 feet It becomes more common upward in company with the whiteleaf oak (Q. hypoleuca), which appears about the same time in similar places. At 6,500 feet it was seen to assume tall, clean, coppice form about twelve feet high, in the gulches frequently with large, obovate, flat leaves. Ascending, it increases in abundance, spreading now over east and west slopes. Upon reaching Horse Ridge which extends east and west at the head of the canyon at an elevation of 8,000 feet,it is practically absent from the north side, on the south side however.it is seen to mix freelywith the other two oaks {Quercus hypoleuca and g. arizonica), displacing ih'^^iu more and more as the stuation becomes higher, steeper, more rocky and exposed. At length the other two are left behind, the netleaf oak is the typical chaparral growth under the scattered pines, Change of Aspect with Altitude. 239 sometimes dense, again very open, all the way to the high summits on all southeast, south, and east aspects, reaching the ultimate summit of Mt. Wrightson within a few yards of its height of 9,432 feet above sea. On the northwest side of what once may have been a crater's rim it is absent, and on certain parts of this elevated and extremely sharp crest extending a little east of north, it is cleanly replaced by a deciduous oak {Quercus submollis) as soon as the edge is crossed. Here we see Q. reticulata always with the small, revolute, oblong leaf and small stature, dwindling to less than two feet on the summits. This change of aspect is equally well exemplified in the oc- currence of other oaks, and to a lesser extent also in their change of form. Arizona White Oak {0. arizonica) appears first in the Upper Soncran zone, on the north side of a ridge lying at an altitude of about 4,500 feet near the McBeth ranch, but is en- tirely absent from the grassy south side. Thence upward, as usual, it is almost everywhere present, linking the Upper Sonoran and Transition zones, and at about 8,200 feet its uppermost out- posts finally disappear from a southeast slope. It undergoes a change of form with ascent, from the size of a tree with large, obovate, often toothed leaves, frequently found in the lower gulches, to small but always erect brush form, growing five or six feet high in mixture with other shrubs, bearing a smaller, thinner, more oblong, less coriaceous leaf. Many slight varia- tions occur in this oak, here as elsewhere, but in this region the transition from one form to another is usually so gradual as to escape notice in the field, making it an unquestionably homo- geneous species. So that any ill-founded segregates that might be made would not disturb the unity of type for purposes of the present comparison of its different aspect habitats. The same may be said of the other, less variable, and very distincet s: ecies of oak. The whiteleaf oak, in the Stone Cabin Canyon, likewise makes its first appearance on north slopes, with the advent of the Transition zone, it is heavily represented thence upward, especially in the cooler, better protected gulches, where it pro- duces tall, vigorous shrubs with stems of post size, and often fine, tall trees. It becomes general on various aspects, but is almost displaced by the Douglas fir on the north side of Horse Ridge. 240 The Plant World. On the south side it reappears in abundance, and much reduced in size. At an altitude intermediate between the upper Hmits of the two preceding species, it is last seen on the same open southeast mountain side where Q. arizonica dsappears. Plere it is an erect shrub of about the height of the latter species at its upper limit, with smaller leaves than below, and these more com- pactly placed. Both species are strictly absent on a northeast aspect just over the crest of a sharp, sloping ridge. As before, at least where the presence of rocky outcrops favors it, the de- ciduous white oak chaparral {Q. submollis) appears here. Similar features of local distribution, only less well marked, are shown by the conifers. The Douglas Fir {Pseudotsuga tayijolia) on the very steep northerly declivities toward the bottom of Stone Cabin Canyon must reach down to within 6,000 feet of sea level at most. It reaches its local center of density, as a fine forest, in the cool, hanging gulches draining northward at about 8,000 feet, but at 9,000 feet it appears to some extent on east and west as well as north aspects. Here it is rather scarce once more, probably due less to high elevation than to the un- usually exposed and semi-arid character of these rhyolitic heights. Mexican white pine {Pinus strohiformis) was first encount- ered at a spring in the bottom of a gulch at 6,500 feet. A few hundred feet higher it first appeared away from water on a steep slope of north aspect.while strictly absent on other aspects. It increases upwards and on the highest peaks it ranks with P. arizon- ica in numbers,or even exceeds it. While here it still prefers the slopes and pockets at the base of cliffs facing toward the north, it can be found in almost any other situation. The Mayr pine (P. mayriana) was noted at 6,500 feet, mixing with the Arizona pine on similar north-facing habitats. On the sunny, south side of Horse Ridge, at 8,000 feet, a few trees were seen again that probably belonged to this sparsely represented species. The principal pine of the forests of southern Arizona (P. arizonica) is encountered in Stone Cabin Canyon, which drains the north side of the high Santa Ritas, on slopes toward the bot- tom of gulches at about 6,500 feet. Like the more shady and precipitous hanging habitats of Douglas fir, its first occurrences at this level are upon northerly slopes, and like the fir and all Change of Aspect with Altitude. 241 the other species noted, it descends farthest in the bottom of the V-shaped draws and gulches, and ascending, gradually climbs the siopes on either hand. Going higher, it presently replaces the oak brush on east and west slopes. It is the most abundant forest tree on many slopes of lesser gradient thence upw ard, is largely replaced by oak chaparral on the austral side of Horse Ridge, reaches quite to the summit of the high crest westward, and almost to the top of Mt. Wrightson. While at these eleva- tions hardly producing a continuous forest, it is quite general on all sides of the higher mountains, occupies many slopes al- most exclusively with Oiiercus reticulata or Muhlenbergia gracilis, while in moister, colder places Pimis strobijormis s imetimes successfully disputes its ground. If the mountains were high enough, there is little question that the same concentration on southerly aspects that obtains among the oaks, vv ould ultimately appear in the pines as well. In fact, at the same elevation in the Chiricahua Mountains the Engelmann spruce and Dcuglas fir replace it entirely on a number of areas on the north side of the several main summits. The \^ idely prevalent, low and thorny evergreen underbrush known as Ceanothus jendleri was first noted in small numbers, ^■et as a distinct constituent element, on a west slope well covered with thrifty oak brush, the deciduous Schmaltzia, and other Transition species, at an altitude not exceeding 6,000 feet, indicating a habitat comparatively mesophytic for this aspect and level. In the still more mesophytic forest ensuing it v. as absent, but immediately upon getting over the crest of Morse Ridge, 2,000 feet above, a cover of shrubs of this species, pene- trable only with difficulty, took complete possession of the inter- spaces in the evergreen oak chaparral very similar to that t)elow. On the north side opposite, the smooth, grassy floor of the Douglas fir forest, entirely devoid of the chaparral species, bore as conspicuous plants only lupine and a slender, deciduous wafer ash (Ptelea). Another example is the madrone (Arbutus arizonica), found on the most favorable slopes of Stone Cabin Can^•on at the unusually low altitude of 5,500 feet, in the middle of the L'p- per Sonoran. It is here a large shrub, or a small tree, but a large tree occurred at the lowest limit in a thicket in the bottom 242 The Plant World. of a gulch. Again near the main crest of several gnarled indi- viduals V. ere noted, advancing on the open side of the forenoon sun to a height of 8,500 or 9,000 feet. The most remarkable range of any species on this route up the Santa i ita ]\Iountains is possessed by Y^icca schottii. Found on the sunny southeast mountain side at a height of fully 9,000 feet, it v. as common and conspicuous at 8,000 in similar habitats. Like a number of other species already noted, it vanished in the Canadian forest of Douglas fir, ^vafer ash, walnut and lujnne at the head of the canyon, only to reappear far below at the lover edge of the Transition, and to continue down to 5,500 feet into the Emory oaks of the middle Upper Sonoran. Ihus it spans a vertical distance of two-thirds of a mile, and like the other interrupted species, unquestionably continues with- out interruption wherever a more open route is followed. In the Chiricahua Jlountains, the different species behave likewise. As elsewhere noted * Quercus reticulata accomplishes complete re\-ersion within a rise of 2,000 feet. Pinus arizonica as already indicated, shows the same features as in the Santa Ritas. Douglas fir descends to 6,500 feet, on some steep, strictly north slopes only, but while still manifesting preference for the north sides, becomes somewhat "careless" of aspect about the highest elevations. Mexican white pine, found at the head of Chaperon Canyon at 7,500 feet on one of its steepest and shadiest north slopes, increases upv^ard and is strongly and generally represented about the summits, on south as v^ell as north sides. Where the high elevations fall off southerly toward head of Rucker Canyon, the three preceding species hide their lower limits in the gulches at points several hundered feet higher than elsewhere, as may be expected. The handsome white fir {Abies concolor), much more restricted in range, having been seen in company with Pinus strobiformis at the lowest station of this species above noted, seeks only the shady pockets and springy spots below, but is at home more openly on some Doug- las fir slopes at higher altitudes, particularly about Long Park. Even the boreal Engelmann spruce {Picea engelmannii, limited in characteristically dense forests to the highest northerly slopes, descending to 9,000 feet in places, on the immediate summit of Cave Peak at 9,700 feet, the highest summit of this range, begins •Plant World. XI. 120. 1908. Change of Aspect with Altitude. 243 to emerge upon east and west sides, and associates with aspen, Nuttall willow, and Pteridium aquilimim pubescens. Its com- panion, the aspen {Populus tremuloides) , though descending to about 8,000 feet with the white and Douglas firs in places simu- lating most closely its northern habitat, appears for the first time on the side of the afternoon sun on the southwestern flank of Fly Peak at an elevation of 9,200 feet. No rocky talus, often giving rise to colonies of mesophytic species out of place, is present, and the slope is compapratively smooth and open. Here is also met Holodiscus australis, of similar, though less pronounced ha! itat affinities. Though best developed about shady boreal nooks and northerly slopes at this altitude, Salix nutiallii is also encountered here, while on the north side of IMonument Peak it descends to 8,400, and in certain gulches on the north side of the Rincon Mountains to 8,400 feet. At the latter altitudes it is limited to the aspect named. In the last named mountains the reversal of aspect between altitudinal limits was found clearly repeated. During an ascent of Rincon Peak, the blue oak {Quercus ohlongijolia) was first met at 4,000 feet, on northerly slopes of the spur flanking Rincon Creek on the south. It continued with slight interruption in its char- acteristic open stand on top of the spur, confined itself at length to the sunnier aspects, and disappeared at last on the most open west and southwest aspects. In ascending the Manning Trail to the northern Rincons, it is first seen hugging the north- west slopes of the gulches, marking here the first outposts of the Upper Sonoran zone at approximately 4,500 feet. About 300 feet higher it becomes general in its orchard-like disposition, and already at 5,600 to 5,700 feet the last blue crowns of this pretty oak become confined to the last open, grassy areas on slopes receiving the most sunlight. At approximately 4,500 feet Quercus emoryi made its first appearance in rocky gulches and north slopes in the southern P-incons, but in the chaparral belt bet.'. een 6,500 and 7,000 feet its final occurrence was on steep southv. est and west slopes only. Ascending the Manning Trail, which lies open to desert winds on the southwest mountain side, it first appears a little higher on the northwest side of the trail- bearing ridge, and its last representatives are seen at 7,000 feet, on a striclty southern slope. On the southern Rincons, Quercus 244 The Plant World. arizonica, seen Trst in shaded, northerl\' places, soon lecame in- creasing! pre.alent, v as still occasionally present high up on the south, est side of i.incon leak, but consistently absent from the steej), north est slope taken l)y its tvv o congeners next higher in range. J eturning to the Manning Trail, it is first met on the shad;- side of a rocky projection at about 5,400 feet in as- cending, and on the first sunny slope below the pine forest in descending. Cn the other route, Quercus hypoleuca first ap- peared on a steep northwest ascent with Ceanothus jendleri at a point between 6,500 and 7,^00 feet, ushering in true chaparral. It is the principal constituent of large bodies of chaparral thence upward, continuing almost to the summit, but above the limit of the Arizona pine is more and more displaced by Quercus reticulata. It approaches the ultimate summit only on the most direct south slopes, w here it is still a little taller than its more numerous neighbor last named. Again returning to the Manning Trail, it first shov. s itself on the left or northwest side of the ridge, and barely disappears from the austral side of the hills before the summit is reached, though replaced by the herbaceous plants of the pine forest on boreal aspects. Its companion, Q. reticulata, appears on this route in similar northerly and otherwise sheltered situations, displacing the other more and more on the higher slopes toward Mt. Ochoa. Given similar topographic conditions, one or both together replace the pine invariably on the most southerly aspects. The same is true at similar altitudes in the Chiricahuas and the Santa Catalinas. On the Rincon Peak ascent, the netleaf oak was not seen until reaching the shade of the pines, but above the more level pine forest it formed dense bodies of typical and almost insurmountable chaparral on the steep slopes^ either loose or rocky, approaching the summit on the south as well as the northwest side. It was especially tall on the latter aspect, being here diversified by an occasional small Douglas fir and Mexican white pine. It remained the principal part of the chaparral to the ultimate summit at 8,465 feet. On the razor-edge crest dropping eastward just under the summit, however, it was absolutely confined to the dense ever- green chaparral on the open south side. The north side, partly enclosed by precipitous crags, in the complete absence of the chaparral, was possessed to the very edge by the two coniferous Change of Aspect with Altitude. 245 trees named above, deciduous white oak, woods, grasses and sub-alpine herbs. In descending the Manning Trail, the first specimens of pinyon {Pinus cemhroides), Garrya wrightii, Yucca sckottii, Nolina eruynpens, the first manzanita chaparral, and other characteristic species denoting the advent of semi-xero- phytic conditions, appear together where the trail turns out of the Arizona pine forest do^^n a south slope, at an altitude of little under 7,500. \\ ith these are associated, also making their first appearance, such other species as Aristida schiedeana, Hedeoma drunwiondii, Oryzopsis fimbriata, Lycurus phleoides, Calliandra reticulata, Parosela albiflora. Here are also the first Chihuahua pine, Arizona white oak, and the first considerable numbers of alligator juniper {Juniperus pachy phlcea) . As we descend, all of these become more or less general, and finally, more or less completely, and many of them in company, seek seclusion on the shadiest slopes, all disappearing before the Lov.er Sonoran is reached, and the first giant cactus rears its head on the sun-scorched opposite side. The phenomenon of change of aspect with altitude may also be oV>served in more general features of plant geography. An instance is beautifully shown in Happy Valley. Here sev- eral parallel ridges extending east and west at the same level have only open grass country, dotted here and there with a solitary oak, on the south side, while the oak woods are well developed on the north. The sharp crests of the ridges mark with equal abruptness the change from one to the other type. On the ridge \\ hich marks the northern boundary of the valley also extending east and west and some 2,000 feet higher, the same oak-woods type is now seen on the south side, while im- mediately on the north loom the spires of pine trees. On the opposite side of the Rincons, the scattered outposts of the pine forest, marked by Pinus chihuahuana, appear on the northwest side of the ridges as low as 6,500 feet. On the southerly aspects, however, the first stragglers are detected far up toward Spud Rock, some 1,200 feet higher. The desert traveler, in following an arroyo or wash near the transition between the Lower and Upper Sonoran zones, may often find one zone developed on the bluffs on the one hand. 246 The Plant World. and the other zone on the side opposite. The bluB's facing- the fiercely burning sun are usually clothed with such types as Acacia constricta, A. greggii, mesquite, other thorny shrubs, and cacti. The sides of the bluffs facing north, particularly if they are steep and well set back between other protruding bluffs, are usually clothed with perennial grasses, dotted v.ith Yucca, Nolina, Agave or Dasylirion, and not infrequently, particularly toward the base, are found thickets of such shrubs as Rhoeidium, Schmaltzia, and Moms celtidijolia, true t^-pes of the Upper Sonoran. Similarly, a canyon bottom or the top of a ridge in the mountains may give us a clean-cut division between Upper Sonoran and Transition societies. The altitude for the canyon, forour region.will be near 6,000 feet and for the ridge often above, 7,000 feet. The Upper Sonoran has now reversed its position with reference to the sun. Again, about 1,500 feet higher, another ridge or canyon having the direction of a parallel will give a similar abrupt change to the Canadian zone, and the Transition has changed its position. Higher still, as for instance, on the summits of the Chiricahuas and less distinctly so on ]\Iount Lemmon, the Canadian in turn is found to have appropriated the south sides, having yielded the cold boreal slopes to the Hudsonian. Without multiplying instances, it may be stated that this reversion of aspect with altitude is a general truth, at least in the Southwest. From desert to mountain top, no species has been observed to behave to the contrary. The same tendency may be discerned between the heart of the Arizona desert and sea-level. The fact holds true not only for the great character species upon which our zones are based, but appears true also for those of discontinuous distribution, like Lippia urightii. It mav be expected to hold in similar mountainous desert re- gions in the northern as ^\ell as southern hemisphere, in the latter with the points of the compass resersed, It should not hold for equatorial mountains, but, except as modified by other influences, should be true for more humid regions, and increas- ingly true with ascending latitude, for it appears to be simply a question of the obhquity of the sun's rays, their effect probably being intensified in acting through a highly rarified desert atmosphere. The primary cause of the floral difference between Change of Aspect with Altitude. 247 two directly opposing aspects is a difference in insolation. Although precipitation and atmospheric conditions may inter- fere, the same primary cause is oj^erative in change of aspect with altitude. The sim is the direct source of both heat and light, and, aside from precii)itation, modifies to a large extent the moisture supply in both soil and air. A high slope receiving direct rays will in its conditions be equivalent in some measure to a lo\\ slope with oblique rays. The following remarks, it is needless to say, are based on much more observation than is detailed above. It has been suggested that some of our species do not occupy as much ground as they are capable of doing, either within or without their geographic areas, and that the way is open for their active ad- vancement and invasion of unoccupied areas. However well this may fit plants under cultivation and a certain class of do- mestic weeds, whose living conditions are made for them, it certainly can not hold true of the wild plants that lend the Southv/estern desert and mountains their true physiognomy. Go where vou will, the recurrence of the same kind of habitat is almost invariably accompanied by the reappearance of the same plants and plant associations. In the desert, the same soil and other features of ph}siography bear quite generally the same societies. In the mountains, without instrument or map, one can determine the altitude within a very few hundred feet by the species he meets on the slopes. If direction should be lost, one can quickly re-orient himself by the plants found on the various aspects. Every similar situation bears a similar coterie of species, and a very few species give any indication of movement, either forward or backward. As seen above, many of the variations found in some species are distributed according to the different altitudes and aspects, and also to the geology and soil. Both in form and local dis- tribution, there is constantly apparent a close fitting of the plant to the place ^^here found. Local ranges of the various species, which are usually circumscribed areas within their geographic ranges, are exceedingly well defined, each corresponding to a certain range of habitat conditions. These conditions consist of various components, chief among which are moisture and temperature. As already indicated, in their effects upon the 248 The Plant World. presence or absence, life history, form, and structure of the p'lant in a given habitat, these components may balance or ofiset each other to a certain extent. For example, the hi^h temperature of a canyon at low altitudes appears often to beoiTset in the plant economy by an abundance of moisture. W hat all the difierent components are, and especially how they act, is for the [thysiol- ogist to determine. The species of widest local distribution, v, hich are frequently also those possessing, for their size, the largest number of indi- viduals per square mile, are usually those exhibiting the largest number and the widest range of variations. It is this versatility or comparative plasticity that must enable such a plant to achieve predominance over its fellows, and to extend or hold its range. But even to it, no considerable or rapid extension of its range appears possible, nor will it on the other hand be likely to lose its ground while the present geologic age and climatic conditions endure. Tucson, Arizona. BOOKS AND CURRENT LITERATURE. Plant-Animals. — The little book under consideration* brings to the layman in popular form the contents of sev- eral scientific papers on two worms belonging to the genu^ Convoluta. It consists of two parts, one devoted to th:* structure, activities and general habits of these animals, the other to the relation between them and the symbiotic algae which they contain. Among the most interesting characteristics in the behavior of the Convoluta is the periodic activity they have acquired in correspondence with that of the tides. This is especially marked in the green species C. roscoffensis which is found only on certain sandy beaches of Normandy and Brittany just below the high- water mark of the slackest neap tide. When the tide is out they are found on the sur- face forming a thin green film, but as soon as it comes in they crawl into the sand and disappear from vieAV. Twice •Plant- Animals :— A Study in Symbiosis, by F. Keeble, 163 pp. Cambridge, 1910. Books and Current Literature. 249 a day then these animals, in response to the rythmic move- ment of the tides, alternately expose themselves to the light on the surface of tlie sand and bury themselves in it. How- ever when the tide is out at night the animals do not come to the surface unless there is strong moonlight. This oc- curs every other week, and it is at this time that the ani- mals deposit their eggs, another periodic phenomenon con- trolled by the movements of the tides. In the laboratory, although not subjected to the action of the tides, the animals keep up their periodic movements for nearly a week if exposed to light, but in total darkness only a dav or less. These movements the author holds are due to the tonic effect of light on the response to gravity. Light he maintains induces certain chemical changes which make the animals positive to gravity and darkness pro- duces the opposite effect. However, the fact that periodic movements continue in darkness, even if for but a short time, appears to militate directly against this theory. The periodic movements must depend in some way upon inter- nal periodic processes which in some instances continue in the absence of immediate external stimuli for considerable periods of time, sixty days and more as recently discovered bv Menke. There are according to Keeble four different methods of response to light — tropoisms, taxes, back-ground reac- tions and phototonic responses. The assumption, however, that the back-ground reactions are essentially different from the others mentioned does not appear to be well founded. Taxes are defined as movements in a definite direction and tropisms as "purposeful curvatures," — an- other addition to the multifarious definitions alreadv devot- ed to this term. Keeble concludes that the reactions are highly adap- tive. After opposing the idea that reflexes are "unalterable and inevitable" he says p. 43 : "They are but servants, and tropistic reflexes serve the master-organisms, to draw it this way or that according as it is well that, this or that route be taken." And again, p. 44: "The organism takes the 250 The Plant World. habit, for example, of relying implicitly on the stimuli of light and gravity. l>y responding to these stimuli, it finds its proper place with such certainty (hat other mode ; of response to other stimuli are ignored habitually." By means of isolation and sterilization the author \v;is able to prove that the green cells in the Convoliita oripiiiaie from a free swimming alga, one of the clamydomonads, v.hich infects the larvae soon after hutching. He raise 1 colorless larvae but found that they went to pieces long ].c fore maturity, indicating that these animals are depe ide.sr upon the algae for essentials in their food supply and f,)r the elimination of nitrogenous wastes, the excretory sys- tem being entirely lacking. The algae when free have a cell wall, four flagellae, a nucleus, a pyrenoid, an eye-spot and several ch]oroplast>. All of these except the chloroplasts degenerate and disap pear after existence in the larvae for a few generations. This the author thinks lends support to the suggestion of Schimper and Lankaster that the chloroplasts in the higher plants originated by the degeneration of symbiotic algae. The book as a whole is verv interestins: and well worth while, but I cannot forbear entering a protest against ex- pressions such as the following, which, in the mind of the present writer are neither popular nor scientific and serve only, especially in the layman's mind, to mystify Avhat actually occurs in the responses of these organisms. "They phototrope themselves to the light," p. 64 ; "It takes the hint and photrotropes," p. 70 ; "Vibrations troping," p. 67.— S. O. Mast. Vegetation IN THE Alps. — Riibel has published * the results of an extended study of the climate and vegetation of the Ber- nina Valley and its adjacent peaks, in the upper Engadine region of the Alps. The author lived for over one year at the Hospice of Bernina and carried on personally the principal part of his instrumentation, at the same time that he used for compari- son all reliable climatological records for his region. The Hospice of Bernina is at an altitude of 7,S78 feet; (2,309 m.) •Riibel, E.. Pflanzengeograohische Monographic des Beminagebietes. Botan. Jahrb.. 47 1, pp. 1-296; 36 plates and map; 1911. Books and Current Literature. 251 the entire area studied reaches from 5,610 feet (1709 m.) at Samadcn to 13,303 feet (4055 m.) at the summit of Bernina Peak, embracing the drainages of the Bernina and the Roseg rivers, ilie climatological data presented by Riibel include the various phases of temperature conditions; readings of black bulb theremometer in vacuo; percentage of cloudiness; force and direction of v.ind; evaporation during the summer months; humidity; precipitation; soil temperature and light intenstiy. All of these data are presented in such a manner as to show the seasonal march in diiTerent seasons. Many comparative data are given from St. Moritz, Pontresina and Vienna. The evaporation readings are from the Wild instrument, protected from insolation, and largely from wind action. The light in- tensity data were secured by the Wiesner method. At the Hospice of Bernina the temperature extremes are — 9° Fahr. (—23° C.) and 75° Fahr. (24° C), frost being liable to occur in every month of the }ear ;the precipitation is 63 inches (1,600mm.), higher than at any of the low er localities in the vicinity; the evap- oration varied from a monthly minimum of 1.4 inches(36mm.) in August, 1905, to a maximum of 4. 1 inches (104mm.) in August, 19i6, being hi her than at \'icnna in the former and lower in the latter summer; the hicrhest mid-day light intensity was to that for Vienna as 6 : 5, the lowest to Vienna as 12 : 1. The vegetation is described under the following principal groups of formations: the coniferous forests of larch and Scot's pine, the tall scrub of pines and alders, the low scrub of Vaccinium, Arciosiaphylos, Jujiiperus and Erica; the moist and dry meadows; the "hochmoor" and "tlachmoor"; the aquatic vegetation and that of the rocks, sand and gravel. The description of the vege- tation is most thorourh-':oing and embraces detailed facts as to the occurrence of every plant association and the vertical limits of the species involved. The numerous illustrations and the very detailed map of the distrihution of the various formations aid in giving a clear portrayal of the botanical aspects of the hirher Al-)s. An attempt to determine the entire constellation of cli- matic conditions for a region, and to make also an exact study of the occurence and distribution of its p ant associations and individual species, is an undertaking of no mean magnitude, 252 The Plant World. and Riibel has accomplished these ends ^\ith conspicuous suc- cess. An attempt to draw from these two sets of facts some inferences regarding the relative weight of the several factors, and the critical points in their operation, as related to the controlling of plant occurence and the distribution of the associa- tions involved, is a still more difficult undertaking. It can only be regretted, however, that Riibel has not made this additional ttep. He has given an admirable presentation of two great sets of facts without making any attempt whatever, in the present paper, to correlate them. — F. S. NOTES AND COMMENT. The entrance of any person into science in a serious manner is usually connected with the woik carried out during his can- didacy for the doctor's degree, and the details of the 437 doctor- ates granted by American Universities in 1911, may be taken to indicate with considerable probability the character of the life-work of the botanists included. Twenty theses are credited to departments of botanical fcience, but as nine others in agriculture and bacteriology are so fundamentally botanical, they are included in the following list extracted from the original article. * Charles Orval Appleman: "Some Observations on Catalase.'' (Chicago). Grace Miriam Charles: "The Aantomy of the Sporeling of A/afa«»a alata." (Chicago). William Skinner Cooper: "The Climax Forest of Isle Royale, Lake Superior." (Chicago). Thomas Haigh Glenn: "Variation and Carbohydrate of Bachilli of the Proteus Group." (Chicago). Mary Sophia Young: "Morphology of the Podocarpineae. " (Chi- cago). Le Roy Abrams: "A Phyto-geographical and Taxonomic Study of th Southern California Trees and Shrubs." (Columbia). Ralph Curtiss Benedict : ' ' The Genera of the Fern Tribe Vittarieae. ' ' (Columbia). Frank Dunn Kern : " A Biologic and Taxonomic Study of the Genus Gmynosporangium." (Columbia). Alvin Carey Beal: "A Study of the Genus Lathyrus." (Cornell). George John Bouyoucos: "Transpiration of Wheat Seedlings as •Doctorates conferred by American Universities. Science. 34: 193. 1911. Notes and Comment. 253 affected by Soils, by Solutions of Different Densities, and by Various Chemical Compounds. ' ' (Cornell). Harold Joel Conn; A Study of Seasonal Variation among the Bacteria in Two Soil Plats of Unequal Fertility." (Cornell). Hing Kwai Fung: "An Ecological Study of the American Cotton Plant with Incidental Reference to its possible Adaptability in China." (Cornell). Lewis Knudson: "The Relation of Aspergillus niger and Penicillium sp. to Tannic Acid Fermentation. ' ' (Cornell). John Pogue Stewart: "Factors Influencing Yield, Color, Size, and Growth in Apples." Cornell). Frederick Adolph Wolf: "The Life History and Development of a some Fungi." Cornell). Robert Fiske Griggs:" The Development and Cytology oi Rhodochy- trium. ' ' (Harvard). Alban Stewart: "A Botanical Survey of the Galapagos Islands." (Harvard). William Ralph Jones: "The Development of the Vascular Structure of Dianthera Americana L." (Johns Hopkins). Harlan Harvey York: "The Origin and Development of the Embryo- sac and Embryo of Dendropthera opuntiodes (L) Eicli. and D. gracile Eich." (Johns Hopkins.) Neil Everett Stevens: "The Meitoic Phase in Heterostylous Plants." (Yale). Frederick McAllister: "The Cytology (i Coavallariaceae. " (Wis- consin). William Alderman Matheny: "Biology of Sclerotinia jructigena and Sclerotinia cinera." (Clark). Walter Byron Gernert: "Unit Characters in Corn and their Behavior in Transmission." (Illinois). Louis John Gillespie: "The Gas Metabolism of the Colon and Ty- phoid Bacilli." (Brown.) Eugene Clarence Howe: "A Biometric Investigation of certian Non- spore-forming Intestinal Bacilli." (Mass. Inst. Tech.) Leonard Dixon Haigh: "A Study of the Variations in Chemical Composition of the Timothy and Wheat Plants during Growth and Ripening." (Missouri.) Caroline Rumbold: "The effect of the a idity and Alkalinity of the Substratum on the Growth of Wood-destroying and Wood-staining Fungi, with a discussion of the Systemiatc Relation of Ceratostomella and Graph- turn." (Washington). Otto E. Jennings: "The Mosses of Western Pennsylvania." (Pitts- burg.) Sevenof the twenty are almost purely taxonomic, nine are of a definite morphological character, two are ecological and two physiological. Very few botanists could be found who 254 The Plant World. might assert that these figures represent the relative importance of the subdivisions of the subject, and the casual examinaticn of the contents of a recent volume of the Botanisci^es Cent:al- bJatt would make is obvicus to the most prejudiced reader that the actual present actixity in botany is far dilierent from that indicated from the analj sis cf this thesis list. It may be profitable therefore, to inquire into the conditions responsible for this botanical misfit. This v. ill lead at once to a considera- tion of the things \\hich determine the direction of the activi- ties of a ; oung botanist. The factors in the order of their actual force appear to be, first, the specialization of the instructor, second, the equipment, facilities and material available, and third, the predilections of the student. The training of the incumbents of the principal chairs and most important teaching positions in America has been one in which morphoIog\- pre- dominated and it is readily apparent that e [uipment for v^ork in anatomy, ftmbryology, cxtology and taxonomy are much more easily procurable than the facilities for experimental vvork in physiology. The content of most problems in taxonomy and morphology is snugly definable and sharply limited. Both instructor and student are inclined to follow the line of least resistance in selecting \\ork, and vath more regard to the possi- bilities of mechanical completion than to the elemental im]-)or- tance of the questions to be ansv ered. 'J he attaiumeiit cf a formal stage in an academic career, especiall} for a l)e.uii nor, does not suggest plans for experimental research in pkiKt \h sies, chemics, or morphogenies, consequently candidates are fre- quently permitted to spend two or three }ears upon topics, which may yield little beyond discipline, and a moiety of assort- able information. Neither this training nor the perspecti\e required with it.however, fits the young botanist for an appre- ciation of the direction of the mo\ ement of botanical science at the present time. Lacking this comprehension, he may not be expected to render very efircient service in presenting the essen- tials of the subject in teaching, to contribute materiallv to its development or to aid in the articulation of its principles w ith those of nearly related sciences. That the unhampered choice of a normal proportion of candidates would lead them into experimental work is well Notes and Comment. 255 attested by information reaching this journal, and that the beginner with a training in exact methods of experimentation would find opportunities for v ork equal to those in any phase of botany is bevond question. In addition to the tasks of instruct- ion and development of the principles underlying physiologic- al science, there also may fall to him the task of applying botanical information in genetics, horticulture, agriculture, soil phvsics, etc. That the Adams Fund for agricultural research in the experiment stations has attained only a fraction of its possible usefulness due directly to a lack of skilled experimenters to take up its problems is a matter of common knowledge. Bv the very nature of the problems the ph)siologist must be prepared for a wider range of original activity than is the worker in any other phase of the subject. He must hold him- self in readiness to go far afield; to build cantilever bridges the farther end of which may rest well within the domain of phvsics and chemistry. It was by such methods that DeVries established the conception of isotonic coefficients, and Pfeffer made his experiments in osmosis, both discoveries being no less vital to ph sics and chemistry than to botany. The acknow- ledged desirabilit cf the meeting and conjunction of the separate sciences (if there are such things) is one which may be well illusfrated by the fact that the candidate with a wisely chosen subject may find in his minors, methods and information es- sential to the development of his main theme. The results of a research of this kind v. ill be likely to interest a wide audience. It is thus to be seen that v, hile research in physiology may make heavy drafts upon the time and energy of the young investigator, vet his re.- ard is that of a wide horizon, and of countless oppor- tunities for profitable cooperation and contribution to the ad- vance of biological science. The nine titles of interest to botanical science in addition to the tentwy credited to the departments of botany are all of a ph'siolgicaol character. Two of the twenty ar physiological making it appear that the student who desires to make a physio- logical study of plants must usually seek his guidance and facil- ities elsewhere than in the existing departments of botany. It is gratifying to note that this abnormal condition is becoming recognized and \\ hile but two universities have rezentiy made 256 Th2 Plant World. or-,' 13. ' provision for additional facilities for ^ ork in j lant \ h siolo a half dozen others are considering pros; ects for i samilar de- velopment. Meanv. hile the beginner, like those now engaged on the subject in America, must get his experience by hook and crook in the great majority of institutions. — D. T. M. During my residence in Miami, Florida, in charge of the Subtropical Laboratory and Garden, I oljser\ed frequently the common l-ubiaceous shrubs of the hammocks and was much impressed with their similiarity to the cof.ee plants \. hich v.ere growing at the Subtropical Garden. This similiarity v, as so great that I collected a c uantit}' of the 1 errics of the commons, est of these plants, Psychotria utidata, separated the seeds from the pulp and made the follov> ing experiment. '1 he seeds v. ere heated in an open test tube over a Bunsen burner, stirring them constantly in order that the bro\^ni^g might be carried on evenly. During this process a delightful aroma as of coffee was given off. On the completion of the brovning process the seeds were ground up in a mortar and put into boil- ing water and kept at the boiling point for some time (perhaps two or three minutes). The odor and color of the resulting solution were those of weak coffee. Unforluiiateb' my experi- ence in coffee making was so slight that the amount of v atcr used in this experiment was far more than shou'.d ha\e been used had it really been coffee that I was using. In spite, hov. - ever, of its diluiton several people who were given the oppor- tunity to taste the concoction all agreed with the writer that the taste was that of weak coffee. The writer's permanent removal from Florida soon after prevented the matter being followed up further, as it should be. Analyses should be made of the seeds to determne whether we have in the country a real coffee plant even though it belongs to a closely allied genus instead of to the true Cofjea. * — Ernest A. Bessey. ♦Read before the Michigan Academy of Sciences at the meeting April, 1911. Volume 14 Numb«- 11 The Plant World A Magazine of General Botany NOVEMBKR, 1911 CERTAIN PHASES OE THE BEHAVIOR OE THE STIGMA LIPS IN DIPLACUS GLUTINOSUS NUTT. Francis E. Lloyd The Bush IMonkey-Elower, DipJaciis, the monotype of its genus, possesses, in common with MimuliiSf Torenia and Mar- tynia a sensitive two-lipped stigma. Responding to the tempta- tion of an abundance of material growing at Carmel, California, near the Botanical Laboratory of the Carnegie Institution of Washington, during the summer of 19n, I attended somewhat closely to certain features of the behavior of the stigma lobes, with the result that there emerged conclusions at some variance with those stated in current text-books, and indeed with those of previous investigators. Correns * in his study of the dependence of irritable phe- nomena upon the presence of free oxygen included in an exten- sive series of forms examined by him, the movements shown by the r.tigma lips of Mimuliis moschatus and M. luicus. He ob- served that the li- s close under reduced atmospheric pressure, but showed that this is due to the reduction of the oxygen ten- sion, and not to any physical effect of the reduced pressure. If the period of exposure is too long, the lips remain closed, but if not, they open again and respond to mechanical stimuli as be- fore. A similar behavior was observed on exposure to ammonia gas. Correns regards the change in the amount of oxygen as the stinuilus, since • s effect is analagous to that due to variation in the amount of light, as in the case of Mimosa. Ammonia, how- ever, he believes to be a chemical stimulant. ♦Correns, C. Ueber die Abhiingigkeit der Reizerscheinungen hoherer Pflanzen von der Gegenwart freien Sauerstoffes. Flora 75:87-151 1892. 258 The Plant World. The first critical study of the question of transmission of the stimulus in these plants was made by Oliver f. the species receiving attention being Mimulus cardinalis, M. luteus, Mar- tyma lutea and M. proboscidia. Oliver's purpose was to deter- mine the path of transmission of the stimtilus from one stigma- lip to the other, since, according to him, this occurs in all these species except in Mimulus luteus, in which the stimulus is not so transmitted. This I am able to confirm. By a nice method of excising a portion of the vascular tissue from one lip, it was proved by Oliver that there was no hindrance to the transfer of the stimulus to the other, thereby showing that, in these forms, the path of transmission lies in the parenchyma. Oliver believed that this is made possible by the presence of protoplasmic continuity, a conclusion which seems reasonable, but not yet demonstrated to be true. The immedi- ate cause of the movement of the stigma lip this author finds in the movements of water into the intercellular spaces, the pres- ence of which has been previously denied by Kabsch J and by E. Heckel * and affirmed by Mitchell* with whom Oliver proper- ly agreed. Oliver's description of the structure of the stigma- lip appears to be applicable to Diplacus except for a slight and not important omission, namely that the epidermis of the outer face is relatively quite thick, and has in the absence of turgor in the motile tissue a considerable power of recovery when bent away from the plane of the style. * f Burck * studying Torenia fournieri and Mimulus luteus. found that the presence of appropriate pollen causes the stigma to remain closed, the closure following mechanical stimulus. This work will be referred to more specifically beyond. THE NATURE OF THE STIMULUS Under normal conditions the entrance of a large enough ♦Oliver, F. W. Ueber Fortleitung des Reizes bei reizbaren Narben. Ber. d. D. Bot. Gesellsch. 5: 162-169. 1887. *Kabsch W. Uber die Einwirkung der gase usw. Bot. Zeitung, 1862, p. 341. (through Correns 1. c.) * *Du inouvement vegetal, Paris, 1875, p. 89 (through Oliver). t tArchives des sc. phys. et nat. de Geneve, 15 Feb. 1875 (through Oliver). fOn the importance of similar mechanical tissue, but of greater extent, in the motile stamens of Berheris and Centaurea see .Tuel, H. O., Einige Beobachtungen an reizbaren Staubfaden . Bot Stud, tillagn, F. R. Kjellman, 1906. *tBurck, W. On the irritable stigmas of Torenia Foiirtiieri and Mimulus Culeus and on means to prevent the germination of foreign pollen on the stigma. Proc. Kon. Akad. v. Wet. te Amst. Sept. 20, 1901. (Ref. in Bot. Central) bl. 89 (No. 23) 645. 1902. Behavior of Stigma Lips. 259 insect into the mouth of the corolla causes the displacement of the lower lip. This then moves forward, straightening and fin- ally curving upwards to oppose closely the upper lip (Fig. 1). After an interval of about half an hour the lower lip resumes its former position, whether pollen has been received on the stigmatic surface or not. Mechanical Displacement the Normal Stimulus. — Merely touching * the papillate stigmatic surface, or bending the papil- lae does not constitute a stimulus. This is shown by the fact that stroking the surfaces with a delicate rod (a broken style) without causing any displacement of the lip as a whole produces no response. The experiment was repeated a number of times, a dozen or more strokes being given in succession. It is hardly possible that the operation could be done without actually dis- placing the papillae in a direction at right angles to their longer axes, from which it would appear that the epidermis of the inner face of the stigma is either not sensitive, or, if sensitive, is in- capable of effecting a visible response to either touch alone or later displacement of the papillae. Further, the stimulus, if effective in any degree, does not pass beyond the epidermis into the tissue below. In this connection it may be noted that the shape of the epidermal cells is such that the mechanical eft'ect of turgor changes will be minimized, namely, by the free walls of the papillae. Backward Displacement. — By this is meant displacement of the lip by pressure on its stigmatic surface. The pressure mav be applied so as to move the whole lip or to bend it within a definite zone. The entrance of an insect has the effect of bend- ing the lower lip transversely throughout its whole extent. In order to cause response this displacement must be suf- ficiently rapid. I have been able, by steady pressure from the finger-tips, to disj^lace the lower lip (this being more convenient to work wuth than the upper) through a wide angle quite slowly, allowing eqaally slow recovery, without response. The same gentle displacement through a small angle at a temperature of about 70°Fahr. repeated five times at two second intervals, pro- duced, on several trials, no response. If, however, the displace- *J. R. Green (Vegetable Physiology, p. 384) says "The stigma of Mimulus — ^will, if either lobe is touched with a fine point, close — ." 260 The Plant World. ment is produced by a sharp thrust a definite, rapid response follows. If such a thrust is applied so as to bend the lip chiefly in a transverse zone near the base, as indicated in a, Figures 2 and 3, the consequent bending will be confined to that zone, and the curvature of the lip, seen in profile, will be represented in Fig- ure 4. If, however, the thrust is applied to the apex of the lip so as to bend it in a transverse zone near the apex, (Fig. 2 b) the curvature is similarly confined to this zone. The resulting re- sponse is as shown in Figure 5. Either lateral edge of the lip behaves similarly by appropriately confining the thrust, e. g., to the zone c, Figure 2. * A complete curvature of the lower lip so as to oppose itself against the apper (Figure 1) results only from such displacement as directly affects all the cells of the mot- ile parenchyma. The above is equally true of the upper lip also, but there is no transmission of stimulus from one to another, Diplacus agreeing in this regard with Mimidiis lutciis (Oliver /, c). Further, if the pressure is not applied symetrically with reference to the median plane, by applying pressure with a very slender, lead-tipped glass rod at, say, a point indicated by d, Figure 2, the movement is greater on the side receiving the greater pressure. The one lip thus takes an oblique position with reference to the other, (Figure 2, d.). The most obvious inference to be drawn is, that the stimu- lus is not only not transmitted from one lip to the other, but that it is not transmitted at all. The alternate inference, that it is transmitted weakly for a short distance only, has logical value as a possibility and is, indeed, suggested by the fact that the cognate forms which have been mentioned fall, according to the results of the workers above mentioned, into a series of decreasing sensitiveness with Diplacus the lowest member. Forward displacement, that is, pressure on the outer face of the stigma-lip (Figure 3, c). Because of the curling back of the edges of the lip, it is important to avoid bending them in applying pressure to the back. The bead-tipped glass rod was successfully used for the purpose. The following experiments are typical. *I have found this account true of Mimulus luteus. Behavior of Stigma Lips. 261 (a) A single forward thrust against the middle of both upper and lower lip produced no response, nor was there when the stimulus was repeated after 30 seconds. The lip closed after a single backward thrust. (b) Stead\- pressure for 20 seconds repeated after 20 seconds was followed by no response. If the pressure was con- tinued steadily for one minute, there was displayed a tendency of the lip to remain in the displaced position, though repeated trials produced inconstant results. In all cases, a single back- ward thrust caused closing. (c) Five thrusts repeated at intervals of one second, no response. Ten thrusts with similar intervals caused a displace- ment from the original position, but no active closing move- ment. Normal stimulus caused the usual response The forward thrust causes a compression of the irritable cells, while the backward thrust, which alone is effective in caus- ing response, stretches the tissues. The displacement resulting from the former is, I believe, purely passive. It seems then, that the stimulus which cause? closing is a sufficiently vigorous stretching of the motile tissues consequent a backward thrust. Brown and Sharp * found that the closing response in Dionaea follows the compression of cer- tain cells at the bases of the sensitive hairs by the bending of these, but that release from the bent position does not constitute a stimulus. In both Dionaea and Diplacus, therefore, a mere shock appears to be insufficient since the factor of direction en- ters in. In order to harmonize my own conclusion, that the sen- sitive cells must be compressed, we may say that the plasmatic membrane must be stretched. It is probable that, if a turgid cell is distorted by pressure applied unequally (as the basal cells of a trichome such as that in Dionaea would be byflexure) a portion of the plasmatic membrane would be stretched, unless free to glide on the inner surface of the cell wall, a condition which probably does not obtain. Indeed, Haberlandt t showed that the sensitive cells of the convex side of the zone of bending in the Dionaea hair lengthened 21 percent of the original dimensions. On the other hand the bending back of the stigma-lip oiDiplacus may have the *Brown. W. H.. and Sharp, \.. W. The closing Response in Dionaea. Bot. Gaz. 49: 290-302 April, 1910. tPhysiologische Pflanzenanatomie, 4th Ed. p. 481. 262 The Plant World. effect of compressing those cells nearer its outer surface in the manner, but not to the extent, that the basal cells on the concave side of the hair of Dionaea are by flexure of it. Indeed this may be said to be true of all the cells, in reduced degree, approaching the stigmatic surface, but we do not therefor remove the difficulty of explaining the effectiveness of stimulus in one direction and not in another. It appears more satisfactory at the present mo- ment to regard the local stretching of the sensitive cells as the critical condition which calls out a response. THE EFFECT OF POLLEN In the third English edition of the Bonn text-book (p. 296) the statement is made that "the stigmas of Mimidus and Torenia after closing on mechanical stimulus open again shortlv unless active pollen has been deposited, \\ hen they remain in a closed position." This is evidently based on the work of Burck, (/. c.) of which a somew hat more s; ecilic account is given bv Jost *. Burck, working -with the above mentioned forms, came to results of very great interest in this connection. In Torenia, the stigma-lips close on lollination only after mechanical stimulus and remain closed only if they have leceived pollen from the two long stamens. If that from the shorter stamens, or from other genera is used, the lips reopen. In Mimulus pollen from any of its stamens ensures a closed condition. Burck found, however, that in Torenia if the pollen from the shorter stamens be dried, it becomes equally effective with that from the longer ones, or that if from the latter be first moistened, it becomes non-effective. The conclusion drawn by Burck is that the effect of the pollen is to withdraw water from the stigma cells, thus reducing their tur- gor and causing closure, f The movement of the stigma pro- duced by the action of pollen is therefore not to be regarded as an expression of irritability, any more than the closure of the lips if effected by dry heat, as e. g., when a hot glass rod be held near ♦Jost Lectures on Plant Physiology, p. 520. ♦In the review, to which I alone have access, (Bot. Centralbl. 89: 645. 1902) the word ' 'Nnrbenschleim ' ' is used. I do not find that a mucilage is present on the stigma in nplacus or Mimulus, and I believe that this word is unfortunate. Behavior of Stigma Lips. 263 them. Under such treatment, one can easily be assured that the closure is due to withering.. Without knowing of Burck's work, at the time, I was led to identical conclusions with regard to Diplacus. An examination of the naturally pollinated flowers shows that, especially in the earlier part of the day, there are many stigmas which, in spite of the presence of pollen, are not closed. Towards the close of the day many will be found closed and in practically all cases in which pollen is present the lips will be more or less curved. Further, pollinated stigmas display a withered aspect, and are character- ized by an opacity absent from unpollinated stigmas. It is im- portant to remark here that the closure due to the presence of pollen is not such as to closely approximate the stigma lips, and the vigorous curvature seen after mechanical response is absent. These observations led me to investigate the matter experimental- ly. It was found that, unpollinated, the stigma persists (in the laboratory in the climate of Carmel, Cal.) for ten or twelve days, retaining its ability to respond to mechanical stimuli during that period. Pollinated stigmas, however, do not close at once, unless pollination is accompanied by mechanical stimulus, in which event they reopen in a short time. In the absence of mechanical stimulus the stigma-lips either approach each other or each may display bendings in various directions, but only after the lapse of several hows, the same occuring, of course, when the pollinated stigmas reopen after mechanical stimulus. They wither com- pletely in three or four days after pollination. The following experiments are typical. Four fresh stigmas were pollinated by placing a mass of pollen across the throat (Figure 6, a). They were stimulated mechanically, but the lips reopened. All four closed later. In two cases some curvature was noted in two hours and twenty minutes, in an upper lip, with which there was more pollen in contact than with the lower, it being difficult to place it in precisely the desired position. In another hour the change in position was still more marked, and was visible in all four cases. On the following morning, 24 hours after pollination, the lips were closed together at their bases, while the apices v ere curled away from each other., in which position (Figure 7) sub- stantially, they remained until withering ensued three days later. 264 The Plant World. Again, a mass of pollen was placed near the apex of the lower lip, either transversely or obliquely (Figure 6, b). In nearlv every instance in twenty-four hours there was a marked curvature in the tissue beneath the pollen (Figure S), but not elsewhere, the lips remaining distinctly open except when withering began. In a few exceptional cases, the failure to curve may be due to the condition or character of the pollen, though I found no evidence of differences such as are observed by Burck in Torenia but not in Mimulus with which latter Diplacus has agreement therefor in this regard. Fig. 1. The conclusion appears therefore to be justified that the curvatures observed in the stigma-lips after the application of pollen are due entirely to the withdrawal of water from the un- derlving tissues, either before or during the germination of the pollen, but between these I have made no effort to decide. The potent factor in bringing the Ups into their final position is, I believe, the mechanical quality of the coUenchyma-like outer epidermis. Mv observations therefore substantiate the con- clusions of Burck on Mimulus, except that in Diplacus the stigma lips open after pollination and close only after the lapse of some time, beginning in about three hours. An inquirv into the character of the pollen in these plants and into its behavior toward the stigma might very well elucidate this difference. Heat. In order to avoid the drastic effect of dr\' heat, which causes withering, I used a tubulatured bell jar standing BthAViok OF StiGMA Lips. 265 in a vessel of vater to which heat was applied from below. A thermometer was introduced from above, the bulb being placed near the stigma of a flower standing in water in a vial. The corolla was removed sufficiently to expose the stigmas. Other experiments were done as indicated bebw. If an open stigma is placed carefully in hot (nearly boiling) vvater the lips close on being killed. The same is true if the lips are held with their stigmatic faces near the surface of the hot water. When killed the tissues become opaque and yellow- ish in color. This closure is h )wever preceded by a slight curl- ing back of the lips, a movement which is probably caused by the expansion of the water in the cells just previous to its escape through the protoplasm. There appears to be no clos- ing response to heat below the thermal death point. This was indicated in the follo\\ing manner. Three stigmas, attached to the flo\. eis, from which for convenience the upper part of the corollas had been removed, were held near a hot water surface, until the slight curling back was noticed. Two of these were killed by the exposure. The third survived, remaining open, in which positi'^n it was found the following morning. The edges of the lips had been killed however, and w^ere withered. The thermal death point was determined by exposure of the preparation to heat in the apparatus above described. A series of trials showed that the point lies very near to 58 degrees C. Thus an exposure for one minute to temperatures beginning with 58.5, falling to 57.5 and rising to 58.3 resulted in killing the stigmas but not the limb of the corolla, which had not been removed. Similar exposure with a range of temperatures of 59, falling to 58 and rising to 58.3 killed both the stigmas and corolla. One minute at 57, or a small fraction of a degree above and below did not kill. At the conclusion of the trials, the remo\al of the bell-jar caused air-currents which were sufficient to cause in some cases the closing of the lips. That this was due to the mechanical disturbance and not the heat was shown by the result that, with very careful manipulation, so as to avoid an inrush of air, closure did not ensue. Thus, after a four minute exposure to 45 to 41 degrees and to 44 to 43 degrees, there was no response, nor after a one minute ex- 266 The Plant World. posure to 48 to 47 degrees, when removal of the bell- jar was carefully accomplished. In one instance however, the evidence was not unequivocal, and there was observed some straightening of the lip, even before the removal of the bell-jar after one minute exposure to 50 to 51 degrees. The positive evidence obtained appears however to point to another explanation rather than to a true response. The behavior toward alcohol and its vapor is analogous to that toward heat. When gently placed in nearly boiling absolute alcohol, the lips close instantly. In cold absolute alcohol closure occurs more slowly, beginning in 20 seconds and being completed in about 50 to 60 seconds. In cold alcohol, however, there is a slight backward curling previous to clo„uie which may perhaps be referred to the shrinkage of the thick epidermis of the outer surface of the lip. The closing move- ment is of the same character ^\ hether induced by heat or alcohol, and ends when the lips have straightened. Exposure to alcohol vapor under a glass for 28 minutes caused closure from which there was no recovery, the tissues being evidently dead, as three hours later they had quite shriv- elled. There was no movement after 15 minutes exposare (ap- proximately the maximum non-lethal dosage) but the lips closed on being stimulated mechanically. They subsequentlv opened, showing that no permanent deleterious effect of the alcohol was had. Alcohol, therefore, unlike ammonia gas (ac- cording to Correns) does not act as a stimulant but, like hydro- cliloric acid vapor, (Correns) and heat causes closure only by killing. It seems probable that anaesthetization by alcohol cannot be accomplished without injury. CONCLUSIONS The closing response of the stigma-lobes in Diplacus is eff- ected by mechanical displacement , only if of sufificient rapidity and when applied against the stigmatic surface. When the sti- mulus is applied against the outer, non-papillate face of the lip it is non-effective. The case is thus analogous to that of the sen- sitive trichomes in Dionaea (Brown and Sharp, /. c). If mechanical stimulus is applied so as to bend only the cells within a particular zone of the stigma-lip, the response, con- Behavior of Stigma Lips. 267 sisting of curvature, is confined to the stimulated zone. There appears therefore no evidence that the stimulus is transmitted either from one lip to the other (as occurs according to Oliver, /. c, in Marlynia and in Mimulus cardinalis, but not in Mim- ulus luteus) or within the sensitive areas of either lip. That there is a slow transmission if possible, but such has not been observed in the course of the work. Mimulus lateus appears to me to be in the same case. There appears to be no cumulative eflfect of mechanical stimuli of slight amount, each ineffective in itself. Mechanical stimulation of the papillae of the stigmatic sur- face sufficient to bend these, but not the lip, is non-eflfective. "Touch" is not a stimulus and the stigmatic papillae are not sense organs. The piesence of pollen does not prevent a reopening of the stigma-lips, when these are closed at the time of pollination by mechanical stimulus. Whether so closed or not, the pollen causes closure beginning in about three or four hours, by the withdrawal of water from the underlying tissues. According to the position of the pollen this closure may be complete and in- Volve both the lips, or partial, consisting of more or less pro- nounced curvatures in one or the other lip. This conclusion is in general agreement with that of Burck cited above, with whose observations on the effect of pollen in preventing the reopening of the stigma-lips my own on Z)i/'/actw are in disagreement. The closure due to pollen is not an irritable response, but is analog- ous to that induced bv heat or alcohol and its vapor, in that it is accompanied by partial or entire disorganization of the tissues. The position of the stigma-lips, under such conditions, is to be referred to the physical properties of the thick outer wall of the epidermis of their outer faces, and not to turgor differences within the motile tissues. A comparison of the conditiofis in Dionaea and in Diplacus, suggests the view that mechanical stimulus is made eft'ective through a stretching of the sensitive cells, either local or involv- . ing the entire cell. Alabama Polytechnic Institute Auhtirn, Alabama. 268 The Plant World. THE HAMMOCKS AND EVERGLADES OF SOUTHEi.N FLORIDA * Ernst A. Bessey. To the botanist visiting soathern Florida for the first time the objects of greatest botanical interest are usually the ham- mocks and the Everglades, although the mangrove swamps, the tropical strand formation and the marine algae will not lack in interest. Let me at once dispel any notion that may have been given by my use of the word hammock that the visiting botanist will take his ease in one of those net-like contrivances so popular in the summer time on moonhght nights. As used in Florida the word hammock means a dense wood of broad-leaved trees, usually Dicotyledonous but sometimes of palmettoes, in marked contrast to the open pine woods which form the greater part of the forest covering of Florida. In order to understand just what a hammock is it will be well first to describe the pine woods in which these hammocks are set, as it were,as islands. In Southern Florida, especiallv in the vicinity of Miami, where the observations of the writer were made, the species of pine concerned is Pinuscaribaea,th.e Cuban or slash pine. Trees of this specie? may attain a height of over 30 meters and a diameter of a meter, although this is larger than the majority of trees of this species. They stand rather distantly from one another, frequently being 6 to 10 or more meters apart, thus forming a very open forest. The tops are rather small and do not give much shade, so that these open pine forests are bright and sunny and have few of the characteristics of the dense coniferous forests of the North. It is frequently possible to see objects at a distance of 800 or more meters in such a forest, .>o scattered are the trees. Among these pines grow dwarf pal- mettoes and other palms with prostrate or underground stems, as well as Zaniia and various other low plants, Typically there is no dense shrubby undergrowth in these pine woods but only scattered small shrubs and herbaceous plants. The hammocks form the greatest possible contrast to the pine woods in which they are generally found. They may be of •Read before the Michigan Academy of Sciences, April, 1911. Hammocks and Everglades of Florida, 269 but a fraction of a hectare or so in area or may contain up to several square kilometeis. Ordinarily, however, their area is from two to five hectares. Instead of the open growth of the pines they are dense jungles of large and small trees, shrubs, vines and herbaceous plants, frequently forming an almost im- penetrable tangle, through which progress is at best slow and difficult. In many places it is impossible to see more than three to five meters in any direction, even upwards. To be sure it is only in the densest hammocks of Southern Florida where no fires or other destructive influences have thinned them out that such thick growth can be found. vSo dense is the shade in some of these hammocks thatat noon on a bright day the light is a sort of dim twilight, while on a cloudy day the darkness is very marked. As a consequence of this dense growth the aii within the ham- mock is moist, the wind being almost entirely checked, while the shade reduces the drying out to a great extent also. As a further indication of the great humidity of the air within the hammocks is the presence of epiphytes of all descriptions, ferns, orchids, bromeliads, liverworts, etc. The trees making up the arborescent flora of these hammocks are entirely diff"erent from those of the regions further north. They are, with few exceptions, not Coniferous It will not be out of place heie to enumerate a few of the commoner or more striking trees as they will show very clearly the difference between these forests and those of the North. By no means are all the families represented in the hammock trees given in the list nor all the genera in the families mentioned. Moiaceae: Morus and two species of Ficus, one of which always and the other often starts Hfe as an epiphyte, eventually in that case destroying the tree upon which it is located. Polygonaceae, represented by the Pigeon Plum, Coccolobis laiirifolia. Allioni- aceae, with a small tree, Pisonia longijolia, and a woody vine, P. aculeata. Euphorbiaceae, represented by Dry petes and Gym- nanthes, fair sized trees. Anacardiaceae, represented by Meto- pium, a sumac reaching a height of 12 to 20 meters. Sapin- daceae, with Sapinius and Exoihea. Myrtaceae, with Eugenia, Anamomis and Chytraculia, Sapotaceae, with four or five genera, one species, Sideroxylon mastichodeniron, attaining a height of 270 The Plant WdRLD. 20 or more meters and a diameter of 60 to 100 cm. Verbena(:eae, represented by Ciiharexyion, a small tree. Bignoniaceae, \^ith the c'alabashy a species of Crescentia. Kubiaceae, \ ith tvo or three arborescent species of Guettarda. The list might be in- creased much more. Perhaps the most important tree in manv hammocks has been left until the last, Quei'ctis vifginiana, the Live-oak. With only a few exceptions all these trees are ever- green. To a large extent the\ possess shiny, often rather thick leaves, the prevailing shape being elliptical. Many of these trees have low hanging branches and some, e.g. Ficus aurea, called locally on that accoimt "wild banyan,'' send down roots from their branches ^^ hich enter the ground and root there and form, as it were, secondary trunks. The trees \\ith very smooth bark, especially those whose outer bark scales off or weathers away as powder, remain mostly free fiom epiphytes on their branches, but the others are sometimes so covered with mosses, ferns, orchids, bromeliads, etc., that their own foliage is quite hidden. In such a hammock the ground is covered with a profusion of ferns and slender shrubs, as well as a thick growth of small and large herbacecus plants. Some of the latter are vines that run up over any support they can find. Among the climbing plants are two or three species of Vanilla. A ver\ disagieable woody climber, which has already been mentioned, is Pisonia aculeata. The writer has seen speci- mens of this in a hammock near Homestead attaining at the base a thickness of over 15 cm. and a length over all of 30 meters or even more. With its festoons of two centimeter thick vines, covered with claw-like thorns, it makes progress through a hammock in which it is abundant anything but rapid or pleasant. One of the most striking features is the startling abrupt- ness of the transition from the pine woods to the hammock. Frequently the trees of the latter are of almost of as great size near the margin as at the center. This is not the case, however, in hammocks that are increasing in size. There is but a fringe, often not over three or four meters wide, of smaller shrubs and when this is traversed one is in the dense hammock. This sud- den transition from a semixerophytic to a decidely humid Hammocks and Everglades of Florida. 271 formation has led many botanists to conclude, at first glance, that there must be marked soil differences to account for the difference in the vegetation. Yet, strange as this mav seem, it is apparently not the case. The soil in the region about Miami is a more or less porous limestone rock, nearly solid in places but more often \\ith numerous crevices and pits filled with sand. Sometimes the rock lies bare, but perhaps more often it is covered by a layer of sand several centimeters deep. Here and there occur peculiar \vell-like pits from 15 cm. to two meters in diameter and up to three or four meters in depth, the deeper ones containing water, at least at the bottom. These so-called pot holes are probably the result of the solvent action of water at a time w hen the ground was submerged. They are frequent- ly lined by the most delicate ferns, e. g. species of Hymeno- phyllaceae. Except for a greater amount of humus in the soil due to the decay of the dense vegetation it supports, the soil in the hammocks appears the same as that in the pine woods. How, then, can we account for these marked differences in vegetation? The soil is the same, except for the differences noted, and these are better explained as a result of the presence of the hammock than as the cause. Some hammocks seem not to be increasing in size, but the fact that some are spreading would show that it is not entirely a question of soil dift'erences. The writer's observations led him to suppose that the genesis of a hammock is about as follows: Somewhere in the pine woods a few of the small shrubs or occasional small persimmon {Dios- pyros virginiana) or other broad leaved trees of which a few- kinds are found also in the pine woods, form a somewhat sheltered place within which the air is somewhat moister. Here, owing to the increased shade, the soil does not dry out so much as where the sun is more direct. Other trees, favored by this increased moisture of soil and air, especially the live-oak, are thus en- abled to get a start. Soon more trees and shrubs appear, the conditions becoming more favorable the more numerous and larger they become. The whole space underneath the trees grows up to underbrush. The denser the growth becomes and the laiger the trees, the more humid is the air, while the dense shade protects the soil from drying out. Many of the plants 272 The Plant World. that in the open pine forest are Small shrubs become fair-Sized trees when thev encounter these more favorable conditions. Thusiti'j not necessary to suppose that all the hammock species -'J ^ R V; Y^^^^^^^K''- ^^ ^~^V if^' ^I^HHP'^' Fig. 1. The interior of a hammock, with the Royal Pa!in. Roystonia regia. must migrate from some distant hammock to take part in the formation of a new hammock. Examples of such plants that are small in the pine woods but form trees in the hammocks Hammocks and Everglades of Florida. 273 are a species of Guettarda, fruiting at a height of 30 to 60 era. in the former situation and forming a tree six or more meters in height in the hammock, Icacorea paniculata, Tetrazygia bicolor, and many others. The denser the growth, the more humid the air and the moister the soil, so much more fullv do these and other tyj^ical hammock plants reach their full develop- ment. Soon epiphytes begin to appear, other typical hammock plants come in and v\e have a typical hammock. This may gradually spread, the nairow margin of shrubs forming condi- tions in many respects similar to those in the first cluster of shrubs or small trees in which the hammock took its origin. That it is the slightly increased moisture and shade that favor the origin of a hammock as well, as its spread seems borne out by the fact that many hammocks have as the center from which they spread, as their base of operations as it were, some naturally moister spot, such as a depression in which water stands or lies near the surface and occupied by some trees that love such locations, e. g. Anona glabra, Magnolia glauca, Diospyros vir- giniana, etc. Thus along the margin of a stream the border of trees that occupy the moist banks furnishes the base from which the hammock can spread into the surrounding dry pine woods. It must be borne in mind, however, that the hammock proper is that portion occupying the land \^on away from the pine woods and not the moister belt of trees bordering the stream from which the hammock got its start. The typical hammocks are so dense that it is doubtful \\ hether they ever have freezing temperature clear within them as far south as Miami. In the pine woods, on the contrary, frosts are fairly frequent and tem- peratures of -5 C. are not unknown. Thus it is that the ham- mocks may contain within them species typical of the tropics, e. g. Swietenia mahagoni, the mahogany, Carica papaya, the papaya, Alvaradoa amorphoides, Sideroxylon mastichodendron, etc., while the pine woods are far less tropical in their flora and the Everglades actually contain many northern plants. The Everglades are much misunderstood. To those not familiar with them the name probably conjures up a picture of a dense, almost impenetrable swamp, with large trees, covered with hanging "moss", slimy pools swarming with alligators 274 The Plant World, and venerrijus snakes and air alive with deadly mosquitoes, This, however, is far from the truth. Perhaps the Everglades can be described best as low prairies, submerged for most of the year. They are free from trees except as noted below. Their level is from a few centimeters to as much as half a meter below that of the pine lands. The soil is frequently a sort of a marl, although vast areas have sandy and others muck soil. Not rarely does the limestone crop out as in the pine and hammock Fig. 2. A hammock in the Everglades. In the distance pine woods of the upland. land. The vegetation consists largely of Monocotyledonous plants, chiefly sedges, grasses, rushes, Eriocaulaceae, etc. Or- chids occur also in the parts not deeply submerged. The vege- tation is not so strange to the botanists from the North as is that of the hammocks or even the pine woods. To be sure Carex will be missed but there will be f 3und in its place many other sedges such as Selena, Rhynchospora, Dichromena and all too manv species of Cyperus. Peltandra virginica will remind Hammocks and Everglades of Florida. 275 him of home while species of Ludwiga, Utricularia, etc., will also a])pear as old friends. When the Everglades aie submerged the danger from freezing is absent; indeed when the water is high even the ad- j« ining pine lands are to some extent protected from frost. Usu- ally, however, the winter is the season for low water so that it happen, that very severe frosts strike the Everglades. Hence it is that strictly tropical forms are largely lacking. Here and there where the land is a little elevated, so as not to be so subject to inundation, we find the so-called "islands" covered with a dense growth of trees. The smallest of these islands mav not contain over four or five trees, semi-aquatic in nature, such as Magnolia glauca, Anona glabra, several species of .Sa/i.x:,etc. The larger of these islands may contain a portion that lies permanently above inundation and such portions are usually occupied by true hammocks, bordered, where occasional flood- ing takes place, by a margin of the trees just mentioned. Next to these, where the ground is submerged most of the time, begins the true glade formation. It Is true that there are a few large islands which contain not only hammock but also pine woods. As one glances across the Everglades in some places but few of the islands can be seen, while in other places they are numerous and fairly close together. The ground is not per- fectly level but at more or less frequent intervals are depressed water courses which usually remained filled with water even A^hen most of the area is dry. In these swales the "sawgrass" Cladium effusum, abounds, often growing as tall as a man on horseback. The water is clear and abounding in fish, and is, probably on this account, remarkably free from mosquitoes. It is only near the islands, where may be found pools where they may breed, that these pests are really bad. These three types of plant formation (not using this word necessarily in its strict ecological signification), hammock, pine land and glade, stand in need of careful ecological investi- gations by precise methods. The writer has outlined conditions as they appear to an observer who has made no instrumental observations to confirm his theories. It is highly desirable that the following problems be studied caiefully: 276 The Plant World, the relative humidity of hammock and pineland and its relation to the development of the hammocks; the temperature, especially the extremes, in hammock, pineland and glade; the influence of soil moisture, insolation, etc. It seems likely that, as has been demonstrated for some marshes in the North, the tops of the Everglade plants are really in a semi-xerophytic location, even when they are standing in water. This should be determined. To work out these and other kindred questions properly would require residence in the vicinity. The necessary observations would be extended over a period of several weeks, if not months. This paper is written in the hope that bome botanist may take up the problem and carry it on to its solution. The writer intended to do this but his removal from Florida makes it im- possible and he hopes that some one else may find it possible to spend the time necessary for these investigations. Doubt- less he could make use of the buildings of the Subtropical Gar- den in his work. Michigan Agricultural College, East Lansing, Michigan. Books and Current Literature 277 BOOKS AND CURRENT LITERATURE. Phytogeography of North America. -Harshberger's monu- mental work, "A Phytogeographic Survey of North America," has recently appeared as the thirteenth volume of Engler and Drude's series ' ' Die Vegetation der Erdc. ' ' * The volume comprises (a) a sketch of the history of botan- ical exploration and botanical institutions in America (45 pp.), (b) a description of the salient features of the geography and climatology of North America, with some statistics of the flora (77 pp.), (c) a literature list (47 pp.), (d) an outline of the geo- logical history of the flora (77 pp), (e) a description of the ' 'phy- togeographic regions, formations and associations" of North America (359 pp.). The first two of these sections are inserted in accordance with the custom of some of the volumes of Die Vegetation, the first being quite as detailed as is necessary to the purpose of the volume, the second very cursory and well designed to orient the foreign reader of the following pages. The bibliography, for which the author does not claim completeness, is a very full one and forms an extremely useful feature of the book. The outline of the geological history of the flora takes up the thread at the commencement of the Cretaceous, the mo- ment from which the history begins to throw strong light on the present assorting of the flora. The influences ot the changes in the configuration of the continent during Cretaceous and Tertiary time and of the occurrence of the glacial period are treated in detail for the several phytogeographical regions. This section of the volume is well done, and to it belongs a large share of the interest of the book. We have had no comprehen- sive treatment of the phytogeography of North America, as interpreted by the geological history of the flora, for 30 years, a period during which geology and paleobotany have made great strides. The description of the vegetation of the contin- *Harshberger, J. W. Phytogeographic Survey of Xorth America. Die Vegetation der Erde Vol. 13. pp. 863, 32 figs., 18 pis., 1 map Leipzig, Engelmann. 1911 (S13.00). 278 The Plant World, ent is the core of the volume, being at once the part for w hich the author planned his preliminary studies and the part in which he approached his most difficult undertaking. He has made a digest of the descriptive literature \\ hich is available,- — • a most prodigious and thankless task, — to which he has added his own observations in several portions of the United .States, Mexico and the West Indies. The phytogeographical subdi- vision of North America b\ Harshberger is the first that has been made by an American w liter, and is, as we might expect, more detailed and more natural than the partitions made by Drude (Atlas dcr Pflanzenverbreiiung, 1887) and by Engler {Die Pjlanz- engeographische Gliederung Nordamerikas, 1902), to mention only the best of the previous attempts. Harshberger's map of North America has been prepared so as to depict the floristic areas, but comes near to being an equally good representation of the regions of vegetation as well. This circumstance is partially inherent in the facts and partiallv an index of the extent to \^ hich floristics has been influenced by physiological plant geography in recent years. The map is not quite so de- tailed as its scale would have permitted it to be, in fact there are a number of minor particulars in \\ hich Engler's map is superior to it. A work of this character and magnitude can be accomplished only by a heavy reliance on the observations of other men, not only entailing a dependence on their accuracv, but an equally important one on their ability to see the things that are most significant. Superadded to this is the necessity that the com piler see in each paper the features and facts that the author considered most important. The Survey has suffered in some respects from these difficulties, inherent in such a great under- taking, but it is nevertheless an extremely valuable volume, rising far above its errors of detail to give a delineation of the botanical features of our continent which will be very useful to American botanists, and, by virtue of its ])lace in Die Vege- tation, V ill stimulate European interest in our vegetation. The editors of Die Vegetation der Erde should not escape without censure for having alloted the whole of North America to a single volume of their series. They have driven the author Books and Current Litekatlki'-. 279 to the committing of a most pardonable and natural error in giving more extended treatment of the regions best know to him personally than their botanical features warrant. The Maritime Provinces and New England have 29 pages devoted to them, \\ hile the vhole of the magnificent, diversified vegeta- tion of Mexico receives only 30 pages. That this is not due merely to the redundancy of literature relating to the former region as compared with its scarcity for Mexico ,is shown by the covering of 18 pages \\ ith the description of the coastal plain region of New Jersey, Delaware and Maryland, whereas only 20 pages are given to the Great Plains and the same number to the Great Basin and its mountain ranges. Either the editors or the author must also answer for not having given more space to illustrative matter in dealing with a subject which invites liberal illustration and is so greatly illuminated by it. The vol- ume contains a number of excellent illustrations of vegetation, but sufl"ers greatly in this respect by comparison with the recent volumes on Africa. The whole of the West Indies, Central America and Mexico is illustrated by only ten cuts, the Great Plains by three and the Great Basin by not a single one. The volumes of Die Vegetation der Erde by Pax,Willkomm and Graebner dealt with small areas, thoroughly known to the author. The volumes on Africa by Engler are the product of his own many years of interest in African vegetation, the co- operation of several of his colleagues and the combined attack upon its flora that has been made by the strong forces of the Berlin Botanical Garden. Americans have only to regret that this continent has been deemed worthy of so small a place in a series which began with such thorough treatment of small but characteristic areas in Europe. Every adverse criticism of any importance which can be made of HarshlDCrger's work gro^^ s out of the immensity of his task, and we can onlv admire the zeal and enthusiasm with which he accepted the invitation of the editors to undertake the treatment of so large an area; at the same time that we prize his volume as a most valuable work, serving at once as the most complete picture of North American vegetation which we possess and as a back -ground for the future woik of American plant geography and for the work of those 280 The Plant World, to whom the facts of plant geography are in the nature of raw materials. — F. S. NOTES AND COMMENT. Prof. Douglas H, Campbell has just contributed to the American Nature Series (Henry Holt & Co.) one of the best of the scientifically popular books on the evolutionary history of the vegetable kingdom that has come to our notice. ' ' Plant lyife and Evolution" is essentially Prof. Campbell's earlier "The Evolution of Plants" brought down to date as respects mophological therories, together with a consideration of the factors in evolution and the origin of species, and some dis- cussion of the bearing of the larger features of plant distribution on phylogenetic history. The most noticeable feature of the book is its catholicity towards all the existing views on the operation of the evolutionary processes, and on the phylogeny of the larger groups of higher plants. This is doing no more than to reflect the current state of biological opinion on these matters, but we may well congratulate ourselves that the gen- eral public is being presented with reading matter of this timely and authoritative caracter. The principal features of interest at the annual meeting of the Botanical Society of America in Washington will be the address of the retiring president, Dr. Erwin F. Smith, on the re- lation of the crown gall disease to cancer, and the symposium on "]\Iodern Aspects of Paleobotany," in which the partici- pants will be Dr. F. H. Knowlton, Prof. John M. Coulter, Prof, E. C. Jeffrey and Dr. Arthur Plollick. The results of the collective activity of the Central Com- mittee for the Survey and Study of British Vegetation have been issued by the Cambridge University Press in a volume entitled "Types of British Vegetation." The contributors are Tansley, Moss, Rankin, Cole and West. Volume 14 Number 12 The Plant World A Magazine of General Botany DE:CBMBKR, 1911 PAPER ATMOMETERS FOR STUDIES INVj^ EVAPORATION AND PLANT x'j^^^^^^^^^^' TRANSPIRATION ^M^ f^ K Burton Edward Livingston The porous-cup atmometer * and its light-absorbing modi- rication f ^vere devised to record the effects of the evaporating power of the air and the intensity of sunshine as these factors might influence the rate of water loss from ordinary leaf\ plants. The instruments, however, fail to simulate the essential struc- ture of plant foliage in respect to the relation existing between the amount of exposed water surface and the volume of con- tained water. While the amount of contained water in leaves is very small, relative to the moist cell walls (internal and ex- ternal) from which evaporation occurs, the volume of water in the poious-cup is very much greater, in proportion to the moist clay surface exposed. It thus comes about that the tempera- ♦Livingston, B. E. — Operation of the Porous-Cup Atmometer, Plant World, 13: 111-118, 1910. The literature of the instrument is there cited. Additional citations bearing upon the instrument and its use are the following: Dickie, M. G. — Evaporation in a Bog Habitat, Ohio Naturalist. 10: 17-23, 1909. Dachnowski, A. — Physiologically Arid Habitats and Drouth Resistance in Plants. Bot. Gaz., 49: 325-339, 1910. Transeau, E. N. — A vSimple Vaporimeter. Bot. Ga/., 49: 459-460, 1910. Brown, W. H. — Evaporation and Plant Habitats in Jamaica. Plant World, 13: 268-272. 1910. Livingston, B. E. — A .Study of the Relation Between Summer Evaporation latensity and Centers of Plant Distribution in the United States. Plant W'orld. 14 205-222, 1911. I-ivingston, B. E. and Brown, W. H. — Relation of the Daily March of Transpiration to Variations in the Water Content of Foliage Leaves. Bot. Gaz., in press. Dachnowski, A. — The Vegetation of Cranberr>' Island (Ohio) and its Relations to the sub- stratum. Temperature and Evaporation. Bot. Gaz., 52: 1-33, 1911. Fuller, E. G. — Evaporation and Plant Succession. Bot. Gaz. 52: 193-208, 1911. fLivingston, B. E., Light Intensity and Transpiration. Bot. Gaz. 52: 417-438, 1911. Idem — A Radio-Atmometer for Comparing Light Intensities. Plane World, 14: 96-99, 1911 > 282 The Plant' World. ture lag of the cup is sometimes more pronounced than that of a leaf; as the air cools at sunset or is warmed at sunrise the large mass of water in the cup keeps the exposed surface warmer or cooler for a time, as the case may be. The coming and going of clouds sometimes brings out similar failure of the instruments quickly to respond to changes in the external temperature. A leaf, on the other hand, responds to many such changes almost instantly. Thus, for detailed analyses of conditions the instru- ments as hitherto constructed are sometimes inadequate, and the results may be misleading. In seeking a practical modification of the apparatus, by which this defect might be remedied, my attention was first drawn to the Piche atmometer *. This valuable device con- sists essentially (see Fig. 1) of a graduated glass tube, closed above and covered below with a circle of absorbent paper, the latter having a pin-hole in its center. The tube is filled with distilled water, the paper disk applied and affixed by an ade- quate clamp, and the whole inverted. The entire disk soon be- comes wet, and evaporation therefrom draws water from the tube, air rising through the pin-hole to replace the water with- drawn. The central portion of the disk is covered above by the end of the reservoir-tube, below by a small plate which sup- ports the paper. This instrument possesses little temperature lag; a paper may be used which ii thinner than many comm.on leaves and holds but little water, and the lag-effect of the water mass above its central portion, and of the thin metal disk below, is negligible, so far as I have been able to detect. But the Piche atmometei has four chaiacteristics which makes it unsuitable for detailed transpiration studies: (1) the hydrostatic pressure upon the paper is irregularly variable; the entrance of air through the pin-hole is exceedingly spasmodic, so that a considerable error is introduced into small readings. (2) It is practically impos- sible to place the evaporating portion at a distance from the graduated reservoir, an arrangement which is often desirable or necessary when the moist surface must be in close proximity *Piche, A. — Note sur L'atmismometre, Instrument Destinee a Measurer L 'evaporation. Bui. Assoc. Sci. de France, IQ: 166-167, 1872. For other references see Livingston, Grace J., An Annotated Bibliography of Evaporation, Mo. Weather Rev., 1908-1909. Paper Atmometers for Studies in Evaporation. 283 with the foliage of a plant. (3) The soft paper circle fails to maintain its horizontal position when openly exposed; slight air movement alters the exposition from time to time, and the wind often throws the instrument completely out of operation. The use of a thicker paper involves a larger amount of con- tained water. (4) The plane evaporating surface is unsuited to the purposesand needs of sunshine records with the radio-atmo- meter; the evaporating surface of the latter instrument mufet be placed so as to receive sunshine ever at the same angle throughout the day, and the only way to meet this condition with a disk is to mount it upon a heliostat, which is manifestly impracticable. I have obviated the first two difficulties essentially by in- verting the whole instrument, placing the reservoir below and the paper disk above. This is, in piinciple, the modification of the Piche Atmometer described by Cantoni. f The lower end of a burette (see Fig. 2) is attached by rubber tube to a vertical glass tube (about 6mm. in diameter with smooth end) which may be at any convenient distance. A second reservoir for filling the burette (usually a bottle with siphon and pinch-cock) is also attached, either by means of a T-tube or simply to a side opening. The burette is filled with water, the glass tube is lowered till water over-flows at its upper end, and the center of a disk of filter paper is firmlv appressed to the latter. Maintain- ing some pressure with the finger upon the center of the paper, to prevent air entering the tube, the latter is now carefully raised until the paper is some distance (10 to 30 cm.) above the level to be taken as zero on the burette. The finger is then re- moved and the instrument is in operation. A suitable plate and clamp, similar to that used on the Piche tube, renders the paper less liable to be displaced. The water level in the burette should not be allowed to fall more than a few centimeters; the water seal where the paper is appressed will not bear high pressure. A freer movement of water is obtained if one or more little paper circles be placed upon the center of a large circle, over the end of the tube. The evaporating disk may be several ■{"Cantoni, G. — Sulle Condizioni di Forma e di Esposizione pui Opportune per gli Evapori- metri. Rend. r. inst. Lomb, 12 (Ser. 2): 941-946, 1879. Abstract in Zeitscher. Oest Ges. Met.. 16: 39-40, 1881. 284 The Plant WorIvD. centimeters in diameter; I find the smallest size of cut filters suitable for rather intense evaporation, for lower rates larger papers may be used. Care must be exercised that the evapora- tion rate never exceeds the possible rate of supply by lateral diffusion past the wall of the tube. When such is the case (the same consideration applies to the Piche instrument), the mar- gin of the paper becomes diy and the readings have no value. Such an arrangement operates a day or two in the greenhouse without attention, but is highly unsuited to w^ork in the open. It will be observed that this form of atmometer resembles the porous-cup form, excepting that the cup is replaced by the paper disk. For radio-atmometry with this device, the black cut fil- ters now prepared by Schleicher and Schiill are admirable. In this form, which may be called the Cantoni-Piche atmometer, the spasmodic variation in hydrostatic pressure and the diffi- culty of separating the reservoir and scale fioni the evaporating surface have both been removed. A wire support foi the edge of the soft paper circle obviates the troubles arising from air currents, but this,with the clamp, which is also necessaiy in the open, renders the device cumbersome and difificult of manipu- lation. The fourth objection mentioned above cannot leadily be overcome so bng as a disk is used for the evapoiating surface, but is completely obviated b\ the cylindrical poious-cup. It was tbeiefore highly desirable to combine the good pointj of the Cantoni-Piche apparatus with that of a cylindrical evaporating surface. This has at length been ac- complished, through what may be termed the paper cylinder atmometer. The evaporating surface is furnished by one of Schleicher and Schiill's extraction thimbles. These are made of pure filter paper, pressed into the form of a test tube, and may be obtained from dealers in chemical supplies. I have used the size 19 x 90 mm., S & S Extractions Hulsen No. 603. Originally, the thimble was merely inverted over the end of the filled glass tube and pressed firmly into place by means of the finger, in a manner quite paralell to that of placing the paper disk of the Cantoni-Piche form. This operation flattened the rounded end Paper Atmometers i^or Studies in Evaporation. 285 of the thimble, howevei , and proved unsatisfactory for other reasons. A better contact between paper and tube was attained by the construction of a s])ecial seat for the thimble, of metallic tin. While the latter might be made of glass the tin is more readily manipulated and its extremely slight solubility in dis- tilled water renders it quite satisfactory. The seat is constructed as follows: The rounded portion (less than 1 cm.) of the end of a paper thimble is cut off and the little paper cup thus obtained is sup- ported, concave side uppermost, in a mass of sand, care being taken not to alter the original form of the thimble end. A piece of "block' ' tin tubing (about 6mm. ciitside diameter and 10 cm. or more in length) is placed and supported upright in the center of the little paper matrix thus prepared, and the latter is filled with molten tin. After cooling the casting is trimmed and smoothed with knife and file, the bore of the tube is reopened, and the seat is finished. Where a number of inr.truments are to be prepared, better procedures than the one above described may readily be devised; this one has proved satisfactory and can be followed in any laboratory. The tin tube is now attached to the burette, in place of the glass of the Piche-Cantoni arrangement, a paper cylinder is passed down over the tin casting and carefully pressed into po- sition, where it should fit snugly (see Fig. 3). W'ith the finger pressing the paper firmly against the opening in the seat, water is now made to rise in the tube, expelling all air before it, until the closed end of the papei cylinder is thoroughly wetted, when the finger is removed. The instrument as thus set up, operates several days in the gieenhouse; frequent filling of the burette should pi event the occurence of a pressure of more than a few centimeters of water column. The instrument is completed and rendered stable enough for almost any sort of woik by two additions, that of an arrange- ment to hold the cylinder more fiimly in place and prevent the entrance of air, and that of a support at its lower free margin. My clamp was made as follows. A test tube is selected, into which the filter thimble will just fit, its closed end is cut off (by means of an emery wheel) and ground down till it forms a small, 286 The Plant World. r^ Fig. 2 Fig. 1. Diagram of the Piche Atmometer. R, graduated glass reservoir; D, absorbent paper disk; F, metal clip about reservoir; W, metal spring; C, metal disk holding paper in place. Fig. 2. Diagram of the Cantoni Piche Atmometer. R, graduated glass reservoir (burette); T, Supply tube from higher reservoir, for filling burette; P, pinch cock; E., tube supplying the evaporating surface; D, absorbent paper disk; F, cork ring on tube E; W, metal spring; C, metal disk holding paper in place. Fig. 3. Diagram showing mounting of the paper cylinder, the rest of the instrument as in Fig. 2. E, tin tube; D, Paper cylinder; L, cork wedges to hold lower edge of cylinder in place; S, tin seat; F, cork ring on tube E; V, metal spring, flexed by W, fine wire; K, ce- ment holding V to C, concave glass cap, wliich presses upon closed end of cylinder, holding It in place Paper Atmometers for Studies in Evaporation. 287 concave shell (3 or 4 mm. in depth) which fits perfectly upon the rounded end of the paper cylinder. Across the center and on the convex surface of this little glasr cap is cemented by its middle (De Khotinsky cement is excellent) a short piece of spiing brass wire (5 or 6 cm. long) slightly turned upward at its ends. Two fine wires are affixed to the tin tube somewhat be- low the free edge of the paper cylinder and these teiminate in loops to pass over the hooked ends of the springs just mentioned, when the glass cup is in place. The fine lateral wires must be of such length that the proper amount of pressure will be exerted upon the closed end of the paper cylinder. To place the clamp in position, the glass cap is caiefully laid in position upon the top of the thimble and pressure is applied with the fingers to hold it and its cross-wire in place. The looped end of one lateral wire is now hooked over one end of the cross-wire. Then the opposite end of the latter is slightly flexed downward till the second lateral wire is brought into place upon its hook. The tension of the spring cross-wire thus distorted supplies the needed pressure, and the tube may now be moved about with little fear of air leakage. To prevent wind from loosening the paper cylinder, pressing it against the tube on this side or the other, three or four tiny bits of paratTined cork are cemented to the latter to form little wedges upon which the free margin of the paper rests, or a deep- ly fluted cork stopper is properly placed upon the tube. These little coik piojecti'ns do not close the annular opening between the tube and paper and ^et furnish to the latter the needed sup- port. Thus arranged, the paper cylinder atmometer may be safely exposed to the strong wind. Under very intense evapora- tion the thimble must be shortened, otherwise its free edge be- comes dry. Another method of affixing the paper cylinder to the tin seat, which has given very good service in the open and which possesses several advantages in the preparation, if not as many in operation, is the following. Common red sealing wax is melted in a suitable container and the closed end of paper cylinder is diy^ped therein, so as to form a heavy, very slightly elastic cap oi sealing wax a centimeter in height. 288 The Plant World. The wax does not penetrate the papei but adheres firmly to its outer surface. In setting up the instrament, the cylinder is lowered over the seat till it comes into position, the water reser- voir is raised till water drips from the lower edge of the paper, and the wax cup is pressed firmly against the seat while the res- ervoir is lowered. With proper care the reinforced cylinder tip grips the tin seat with sufiicient force to maintain itself in position. The base of the cylinder should be supported as above. In the paper cylinder atmometer, the evaporation takes place almost entirely from the exterior of the cylindrical surface. At the same time an ample air space separates the moist paper from the water-filled metal tube, and very rapid adjustment to changes in the surrounding temperature is allowed. For some purposes it may be desirable completely to close the annular opening below, as by a thin cork ring. The volume of water held, while considerably greater (proportionately to the active sur- face exposed) than in the thinner paper disk forms, is not large. These thimbles hold water to an amount about equalling 70 per cent, of their dry weight, this being less than the amount held in the foliage of many^ thin-leaved plants. The surface may be blacked by the use of washed lamp-black and water, as on the porous-clay cup, for the measurement of light effects, and the whole cydinder may be placed in any position, at any angle, with perfect safety. It has been found that the process of washing sometimes results in a more or less pronounced agglutination of the lamp-black into larger granules, (at least in the case of cer- tain varieties of this material) and a substitute therefor has been found in the finely divided manganese dioxid which results from the reduction of potassium permanganate by boiling its solution with a little cane sugar. The precipitate is washed and decanted several times and then used in the same manner as lamp-black. In the perfecting and testing of the paper cylinder atmom- eter I have been assisted by Mr. Lon A. Hawkins, to whose in- genuity the details of the metal seat are especially due; also by Prof. J. S. Caldwell, to whose able co-operation at the Desert Laboratory during the summer just passed are due the working out of the sealing-wax cap and the manganese dioxid coating. Establishment Behavior of the Palo Verde. 289 It needs also to be stated here that tlie new atmometer now- described — and indeed the porous cup forms as well — are to be largely attributed to financial aid from The Department of Bo- tanical Research of the Carnagie Institution of Washington. The Johns Hopkins University, Baltimore, Md. ESTABLISH MEiNT BEHAVIOR OF THE PALO VERDE. Forrest Shri: vk One of the most striking cha-actevistics of the deserts of southern Arizona is the diversified assemblage of ''vegetation forms" or "life forms" which they exhibit. These fall sharply into two classes, — the succulents and the sclerophylls, — the former of which is represented by fewer species than the latter but is of quite as great importance in determining the physiognomy of the vegetation. Among the succulents ma^" be distinguished the leafless stem-succulent cacti, greatly diversified in size and form, the leaf-succulent Agave, the leafy stem-succulent Yucca and Dasylirion, and the root-succulent Ttimanwca. Among the sclerophylls there are less striking differences of gross form, but equally important distinctions in character of foliage and seasonal habits. As examples may be noted Covin ca, with small evergreen leaves, Celtis pallida, with broad, evergreen leaves, Prosopis and Acacia, with deciduous dissected leaves, Jatropha cardiophylla with broad deciduous leaves, F ouqiiieria , with ephemeral broad, thin leaves, Parkinsonia, with minute deciduous leaves and chloro- phyll-bearing bark, and Ephedra, with leafless chlorophyll- bearing stems. Spalding has shown * for this region that a number of the characteristic types are limited to certain topographic sites, and that many occur abundantly in certain situations and only sparingly in others. However, on the higher mesas, the basaltic hills and the foothills of the larger mountain ranges may be *Spaldiag, V M. — Distribution and Movements of Desert Plants. Pub. Cam. Inst., 1909. 290 The Plant World. found a relatively dense vegetation in which occur examples of nearly all, if not all, 3f the types which I have mentioned, grow- ing intermingled under identical environmental conditions. The larger differences of soil texture and topographic site deter- mine the flora of a given hectre of ground in such situations as these, but the relative abundance of this or that type or species of plant is not, I wish to maintain, so much a matter of physical conditions as they affect the adult plants, but rathei an outcome of the vicissitudes of germination and establishment for the species of the flora of that area. After the larger features of the habitat have determined its flora, I am convinced that the ac- tual make up of the vegetation, the relative abundance of the different types or species, and even, to a large extent, the density of the stand itself are products of the conditions which con- trol germination and the activities of the seedling during its first twelve months. This is indicated by the extreme irregu- larity of admixture of vegetation types in small areas. The work of Cannon f has shown that great diversity of root habits exists among plants of the different types, which may have much to do with enabling a mixed population to survive on an area where a uniform population of the same number of individuals could not do so, owing to the fact that the different types secure their supplies of soil water either at different levels of the soil cr at different seasons of the year. Serving merely as an extreme case of the irregularity of the allotment of desert plants are the not infrequent dense colonies of the same species, near which, and under identical conditions, may be colonies of other species. These cases are nearly conflned to the cacti, however, which ob- tain their annual store of water during the summer rains and do not therefore invalidate the explanation of the usual diver- sity of stand which is afforded by the work of Cannon. These pure stands must also have their explanation in the chances of seeding, geimination and establishment (or of vegetative multi- plication) rather than in any physical differences of habitat. I am still further convinced that the chances of geimina- tion have a very important part in determining the character and density of desert vegetation, by the extreme slowness with tCannon, W. A. — The Root Habits of Desert Plants. Pub. Cam Inst.. No. 131 1911. Establishment Behavior of the Palo Verde. 291 which a piece of cleared desert becomes repopulated. Here is no question of the clearing having made the conditions for re- popiilation any less favorable than they are at any unoccupied spot in a virgin stand of desert plants. For example, there has come under my notice a block of ground within the city limits of Tucson, which is occupied by a stand of Covillea of the aver- age density, through which there formerly ran three roadways. Ten > ears ago the block was fenced off and has not been used as a highway since. The roads had never been worked, but were simply made by the clearing of the ground and the wear of wheels. They are still conspicuously visible, and in them have not grown any young plants of Coiil/ca. The rate at which new individuals are added to natural stands of desert plants is also extremely slow in very many species. In the spring of 1906 Prof. V. M. Spalding surveyed and carefully charted an area near the Desert Laboratory on which there were growing, along \\ith other plants, some 72 in- dividuals of Encelia farinosa. In the spring of 1910 I went over this area and located each of the 72 plants and searched care- fulh for new individuals, finding only one, which died in the following month. My interest in these phenomena l^d me to inaugurate work looking to the determination of: (a) the character of geimina- tion and seeding in different types of desert plants; (b) the na- ture of the vicissitudes which control germination and estab- lishment, (c) the possible differences of establishment rate in different types of deseit perennials. The first two of these ob- jects are designed to secure knowledge as to the importance of the early ontogeny of the peiennial types in determing their local distribution and in contributing to the characteristic com- plexity and openness of desert vegetation. The third of the ob- jects is looking not only to the phenomena which may be opera- tive in changing the character of the desert vegetation, but to- ward a possibility that secular changes of climate are rendering the conditions less suited to some of the desert plant types and more suited for others. I have undertaken two lines of work as sources of evidence on these problems: statistical work on adult populations and observational woik on the actual occurences of 292 The Plant World. germination and seedling mortality on a limited area. My work on this area has been confined to six common types, four of cacti and two of sclerophyllous trees. In addition to deter- mining their germination behavior I have secured continuous records of the atmospheric evaporation rate and the moisture of the soil at depths of 3, 15 and 30 cm. In a previous papei "^^ I have reported on statistical work with the Giant Cactus, which went to show that it is not maintain- ing itself at its former rate of establishment. I have since en- deavored to get similar statistics for the Palo Verde {Parkin- sonia micro phylia), which is a Leguminous tree, with chloro- phyll-bearing bark and very small leaves, which are borne onlv in the rainy seasons of late winter and midsummer. In the stems of Palo Verde very nairow rings of giowth are visible. By polishing and varnishing sections of trunks it is possible to count these rings by the aid of a hand glass. By counting the rings along several radii, and by recounting each section after I had recorded and forgotten how many rings it had, I was able to determine the number with no errors in my extreme differ- ences of count of more than 10%. The fact that Palo Verde has two periods of foliation in the year made it seem probable that it might have two periods of growth in trunk diameter, although I had noted that its shoots made no growth of elongation in the late winter rainy season. In order to determine whether the rings of the trunk are annual or semi-annual I made a careful measurement of some thirty stem diameters on six individuals in two localities. The places at which the measurements were first made were marked by touches of paint, which proved to do the stems no injury. The measurements were made with mi- crometer calipers, reading to .1 mm. The result was that no growth was detected during the late winter period of foliation, showing the rings to be annual. In order to secure a curve of growth rate I cut 22 trees of difl'erent diameters and counted their rings. I then secured trunk diameters of a j)opulation of 146 treees on the north slope of Tumamoc Hill, over the same area on which I made one of my determinations of establish- ment rate in the Giant Cactus. The trees were measured with *Shreve, Forrest — The Rate of EstabJishinent of the Giant Cactus, Plant World, 13, 235- 240. 1910. ESTABLTSHMEXT BEHAVIOR OP THE PaI.O VeRDE. 293 metal calipers such as are used in lathe work. The fact that the Palo Verde branches close to the ground made it necessary to measure the trunk diameter at the surface of the ground, and in some of the largest trees even to dig below the surface. When- ever the trunk was elliptical or irregular in section I averaged its greatest and least diameters. I then converted the set of dia- meter measurements into ages, by use of the curve of growth rate, and secured the following groupings of the number of in- dividuals that became established during the periods indicated. TERIOD. NUMBER OF TREES. 1490-1520 -- - 1 1520-1550 - 4 1550-1580 4 1580-1615. - 7 1615- 1640... ..1 1 1 640- 1 670 1 2 1670-1710.... 11 1710-1760 ......18 1760-1810 13 1810-1 840. 1 7 1840-1860.... 21 1860-1885 17 1885-1910 . 10 It is manifest from the anti .uity of this population that I have no warrant for considerin;; the above figures as any indica- tion of the rate of esta1)lishment. Scores of individuals must have germinated, grown to considerable size and perished on this area since 1490. The ligures merely indicate the age of the suiviving individuals. Howcxer, the number of survivors from the 1840-1860 period to l*nO has steadily fallen, so that this portion of the curve, at least, is fiee from the error of having been seriously reduced by d"cath of adult trees. How much I have to reckon with human interfeiencc 1 am unable to say, but such interference wnild at least be directed chiefly to the taking out of the laigest trees for firewood, anil might account in part for the low number of smvivors of the greater ages, but would scarcely affect the individuals of the last three periods. I am 294 The Plant World. inclined, then, to consider the figures just given as showing nothing with regard to a rise or fall of the establishment rate from 1490 to 1840, since the rise in number of individuals dur- ing that period merely indicates a shortening of the period over which various causes of death might overtake the trees. Th*^. fall in number of survivors in the last three periods, however, is not influenced by this erroi, oi lather if the error is effective it has merely served to make the fall in that pait of the curve less steep. The figures of the last three periods indicate, then, that there has been a fall in the rate of establishment during the last 60 years. That this fall lies over the same period in which I found a decrease in the establishment rate of the Giant Cactus indicates, tentatively, that whatever secular changes of climate may be taking place are affecting the largest of the succulents and the largest of the sclerophyllous trees in the same manner. My detailed observations of the present rate of germination and seedling mortality have been made over an area of 640 sq. m., lying within the area over which the above mentioned census was taken. My method has merely been to go over the area carefully every few da}s at the time of the first summer rains, and to drive a numbered stake near each seedling. No germi- nations take place at any other time of the year. At periods of every two or three weeks during the year I go over the area and remove the stakes from all seedlings that have died since the last visit. The summer of 1910 was a very favorable one for Palo Verde germinatic ns, and the total number was 542, over an area on which there are only eight adult trees living at the present time. Without giving the detailed record of the annual march of soil moisture and evaporation conditions, which 1 hope to do latter in a more detailed treatment of this entire matter, I will merely refer the number of deaths in the seedling crop of 1910 to the somewhat unique seasons of southern Arizona in the following table, SEASC>N NUMBER OF NUMBER OF DEATHS SURVIVORS Humid Mid-Summer, 1910 43 499 Arid After-Summer, 1910 157 342 Winter, 1910-11 74 268 Arid Fore-Summer, 1911 146 122 Humid Mid-Summer, 1911 60 62 Establishment Behavior oi? the Palo Verde. 295 The arid after-summer and the arid fore-summer are found to give rise to the greatest number of deaths, while the winter season and the humid mid-summer season give rise to a lesser number. The 62 seedlings surviving at the end of sixteen months are 11% of the original number of germinations. What the fate of these survivors will be may be inferred from the results of an examination which I made of all the dead seedlings which oc- cupied my observational area when I began work on it in May, 1910. These represented, presumably, the ('eaths of the preced- ing 12 to 18 months, being 160 in number. After a prolonged soaking in ghcerine and alcohol the seedlings were sectioned and their ages determined, with results as follows: Age in years 1 2 3 4 5 6 7 8 9 10 Number 105 32 20 1 0 0 1 0 0 1 These figures indicate, as "\\ould be anticipated, that the greatest mortality occurs in the first year, that it continues at a rate \\ hich is high relatively to the number of survivors through the second and third years, and falls thereafter to a rate which is very low. The number of survivors at the end of the third year is probably never more than 3% of the number of germina- tions, and must often be none at all. I have noticed that the severely arid conditions of the fore- summer cause the death of a great many twigs on Palo Verdes that must be from 10 to 20 years old, and on all sizes larger than that. The death of these twigs of coirrse serves to cut down the water requirements of the plant a|j^ must operate in the direc- tion of saving the remaining portion of the plant at a time of extreme transpiration and very dry soil. It is, iir effect, anala- goirs to the leaf-fall of the decidious trees in the dry rrronths of morrsoon climates, and is more crudelv analagous to the con- traction of volume under severe transpiration that is exhibited by the larger cacti. When a Palo Verde seedling becomes large enough to withstand the loss of some of its branches in the most critical portion of the year, its life is safe from all but droughts of the most extreme severity. When this age is attained, and it must be a variable one, the death rate falls to an extremely low- figure. I have had a great many thousands of Palo Verdes come 1% The Plant World. under my observation within a radius of 75 miles of Tucson, and have seen only two dead trees of full size. I have found that the shade of adult trees and other large plants does not materially lessen the death rate, for the condi- tions of soil and atmospheric aridity are just as pronounced on the north side of trees and shrubs during the arid fore-summer as they are in other situations. I have not found that there is any importance in the number of seedlings occupying the same spot, as respects their chances of survival. There are several cases among the seedlings of 1910 in which two and three indi- viduals growing as close together as possible have all survived to date, and on a single square metre w ith a population of nine seedlings the percentage of survival has been much higher than on the area as a whole. These considerations, together with the seasonal fluctuation in death rate, lead me to conclude that the ''vicissitudes" and ''chances'' which determine the survival of Palo \'erde seedlings are almost wholly physical, as distinguished from the so-called biological conditions, which is to say the physical conditions which are initiated by assoc'ated plants. By far the most important of the physical conditions are those which have to do with the maintenance of the trans- piration-absorption balance of the seedlings. The Desert Laboratory, Tucson. TPIE COMMERCIAL RAISING OF SEEDS A. J. PlETERS The personal experience of the writer has been confined to the raising of vegetable and sweet pea seed, but the fundamental problems are much the same in all kinds of seed raising, diffeiing more in details than in the nature of the problems. In geneial, these may be grouped under two heads, the growing of the seeds, "making the crop," and the selling of them. The latter is per- haps the most difficult, and the root of probabl} nine-tenths of the trouble of the honest seedsman is to be found in the matter of price. The Commercial Raising o? Seeds. 297 There is no inherent difllculty in raising good seeds, but it is impossible to raise them foi the same price as poor seeds can be raised. The keenness of competition and the tendency of many dealers to buy where they can bi.y the cheapest has a de- pressing effect on the quality. The fact that the quality of vegetable seeds is not what it should be is the fault of the letail dealer. Theie is a good margin of profit in the retailing of seeds, and there is no reason why the retailer should not pay a fair price for his seed. If instead of paying the low'est possible price for a pound of lettuce seed he paid five cents a pound more he could get the best seed that is produced. If this seed is sold by the packet 100 of them will be filled from this pound, making the increased cost of the seed to him, all other items of cost remaining the same, l-20th of a cent per packet. If the seed is sold in ounces and fractions, as is usual in the market garden trade, the added cost will be about 1-3 of a cent pei ounce. These examples will serve to show that there is no excuse for the practice of many dealers who place their orders with a grow- er who will contract at the lowest price, rather than with one of the best growers. This is the real problem of the giower. While experience and a good knowledge of horticulture are necessary to raise good seeds, there is nothing about this that could not be under- taken by most good gardners. In the growing of crops there are always local problems to be sohed, soil and water conditions and labor, but these matters are incidental to all lines of agri- culture. The special problem of the seed grower is keeping his stocks true. The types of our vegetables and sweet peas are not as a rule well fixed. This is due to the fact that there is no uni- form method of describing new varieties, and but little efi"ort is made to describe them at all. Many of the older sorts are pretty well fixed as to their main features, but the leading seeds- men are not agreed as to the details of the type. For instance, some claim that ' ' New \'ork ' ' lettuce should have a pointed head and others claim that the head should be spherical. Some sell white seeded 'Tennis Ball' lettuce and "'Boston Market" for the same thing, \^ hile otheis point to certain differences in shade of color and firmness of the head and claim that they are distinct. 298 - 'J^JJg Plant World. This lack of definiteness makes it difficult for the grower. He may have what he and some of the trade consider a good stock of a variety and find that another dealer does not consider the variety true to name. The writer some two years ago bought stock seed of a new variety of sweet peas form one of the best dealers and specialists in sweet peas. From this he grew a crop of seed and sold some to another dealer. In the course of time a complaint was received to the effect that the seed was not true to name. The whole trouble was that the two dealers did not agree as to the type of this variety. It is important that the grower should have clearly in mind what type he is going to grow. With this type in mind he makes his selections in accord- ance with the system he follows. As a rule those glowers who do any selection at all confine this to a general selection of the best plants in the field. There is perhaps no pedigree work done at all. This requires too much time and expense, but the best growers follow a system of double selection. Each year they stake several plants as nearly perfect as they can find. The small quantity of seed produced by these plants is sown in a sep- arate block, and from this block the general seed stock for the following season is taken. By this system no stocks will ever become absolutely pure, but only a small number of the ' ' rogues will appear every year. These are cut out before they bloom in case of the vegetable seeds, and as soon as the flowers aie out in case of the sweet pea seeds. Financially the pressure is in the direction of placing new varieties on the market or of raising the standard sorts at as low a cost as possible. The better growers do a certain amount of selection, but there is little eflort to produce pedigree stock of the better sorts. The standard of the vegetable seeds sold by American dealers is much lower than it should be, but the reme- dy is in the hands of the dealer and not the grower. The latter must grow what his tiade demands and at a price the trade is billing to pay. There are, of course, dealers who will pay a fair price for good seed, but this tiade is rather limited, and any grower catering exclusively to it would do. a very small business indeed. For the student of plant variation there is no better place than a large seed farm. The number of individuals is Books and Current Literature 299 large, running into the hundreds of thousands for each variety. Sports are constantly appearing, and the fields afford unlimited opportunity for crossing. University of Michigan. BOOKS AND CURRENT LITERATURE. The Dunes of New Zealand. — Cockayne has recently made a second valuable contribution to the literature relating to sand dunes and their reclamation. * His previous report, published in 1909, and reviewed in this journal for June 1910, presented the partial results of a scientific survey of the New Zealand sand dunes, made in the austral summer of 1908-09, under the direction of the ]\Iinister of Lands. It was confined to a consideration of the nature and the flora of the dunes of western Wellington, but the present paper covers those of the whole New Zealand biological area, and a second part is added which treats with great thoroughness the subject of their recla- mation. The dune areas of the North Island comprise 290,000 acres, that of the South Island 24,000 acres. They are for the most part situated on the coasts, but some of smaller extent in the interior. It is evident that the proper management of this large extent of territory is a matter of no small importance. In Europe the prime object of dune reclamation has been the preservation of the coast lines, but in New Zealand it is the protection of adjacent fertile lands, as well as the utilization, as far as possible, of the dunes themselves. It is believed that before the entrance of civilized man upon the scene, nature herself had made the dunes stationary by clothing them with a protective indigenous vegetation. The number of plant species now growing on the dunes is 147, of which 82 are endemic and 43 Australian. Several of these nat- ive species are excellent sand binders or sand collectors. The author gives full descriptions of these, pointing out the special adaption which they possess for these purposes. The most 300 The Plant World. efficient is Spinifex hirsutus, a rapidly growing perennial grass, having numerous stout, branching rhizomes of great length. Its method of seed dissemination is remarkably adapted to its habitat. It is dioecious, and has a globose female inflorescence, often a foot in diameter, composed of radiating spines some five inches long, at the base of each of which there is a one- flowered spikelet. Borne by the strong breezes these balls go bounding over the sand, ultimately breaking up and scattering their seeds far from the parent plants. Since the settlement of the country the native covering has been largely destroyed by fires, grazing and cultivation, and the result has been that the dunes have become active, and are occasioning great damage, and threatening more. Even slight wounds in the surface, such for instance as might be made by a sheep rubbing its tick infested back, are liable to be scooped out and enlarged by the powerful winds, until eventually the whole hill is set in motion. A few attempts have been made at reclamation, and in some cases a limited success has been achieved, but no compre- hensive, intelligently directed scheme has been adopted. Plant- ings made in ignorance of the conditions of the problem have been ineffectual, and some injurious, for plants may create as well as restrain dunes. Much of the report is devoted to a state- ment of the principles and practices which must be observed for successful reclamation. In New Zealand, as elsewhere, afforestation must be re- garded as the ultimate solution of dune reclamation, but under the conditions there existing this can be accomplished only as the climax of a series of preliminary plantings. The author recommends beginning with Marram Grass {Ammo ph da aren- aria), to be succeeded by the California Tree Lupine {Lupinus arboreus), and then by some of the native shrubs, and at last, under their shelter, by trees. Of these the most esteemed are the two Monterey conifers Cupressus macrocarpus and Pinus radiata, and Firms muricata. An extended annotated list of plants worthy of tiial is given, for it is felt that wide experi- mentation is needed to determine the species best adapted to varying conditions. Notes and Comment. 301 A curious instance of the inappropriateness of a popular name may be noticed. In the United States the European Carduus arvensis bears the misleading name of Canada Thistle; but according to this report in New Zealand it is called California Thistle, which is even more undeserved, since California is one of the few states of the Union in which this weed has not yet made its ap- pearance.— S. B. Parish. NOTES AND COMMENT The investigations of the Agricultural Department into the feasibility of utilising various crop wastes in the manufacture of paper have been recently summed up b}- Charles J. Brand in a Circular of the Bureau of Plant Industry (No. 82), which is not onlv interesting as respects reading matter but is an effective demonstration of the products that have resulted from this experimental work. The five sheets of paper ^^ hich form the circular are made respectively from cornstalks and cotton hulls, broom corn stalks, rice straw and spruce wood, broom corn stalks and popular wood and from cornstalks. The quality of all these papers is very good, for, as Brand says, it has been possible to produce good paper from crop wastes, but it has not been possible to produce it at a c< st lower than the present cost of other paper making materials. Cornstalks are- one of the largest agricultural wastes and are one of the poorest paper- making materials tried. Broom corn produces a longer fibre than Indian corn, but is not grown in verv large quantities. Rice straw and the bagasse from sugar cane both make good grades of paper, and they h:ive the practical advantage that they are by-products of centralised agricultural industries. In all these cases it is possible to extract the soluble constituents from the waste, which are rich in protein and sugar, and will serse to lessen the cost of the ])a])er made from them. The author states that the cro'p waste pajH-rs will l)c suitable for books, writing paper, etc , pointing out the features in which wood pulp paper is superior to any other lor newspaper stock. The well-known rapid e:.haustii)n of the supplies of spruce and other woods suitable for pulp making will, however, soon give an 302 The Plant World. economic importance to the crop wastes as sources of all grades of paper. This little circular gives a cheerful tone to the pros- pects for the conservation of the Sunday Edition. In a recent bulletin of the New York Botanical Garden Dr. Frank D. Kern has published ' 'A Biologic and Taxonomic Study of the Genus Gymnosporangium. " Dr. Kern has made the usual taxonomic study, in connection with which, as his title in licates, he has carried out several lines of investigation which give his published results far wider interest than is usually pos- sessed by the monograph of a genus. He has made over 200 in- door cultures with a view to confirming and extending our know- 'edge of the life cycles He has made a detailed study of the dis- tribution of the species of Gymnosporangium and of the known host plants of its two stages, concluding that the ^^presence of suitable hosts will assure the presence of the fungus, without regard to the environmental factors that are commonly con- cerned in the occurrence or absence of plants. A complete under- standing of the genesis of the present distributional relations of Gymnosporangium cannot be had without further knowledge of the geological history of the movements of the host genera. Evi- dence is brought forward to show that there is a correlation between the suppression of uredospores in Gymnosporangium and the performance of the characteristic functions of uredos- pores by the aecidia and teleutospores. A discussion is also given of the pathological effects, economic importance and con- trol of the genus. Dr. F. L. Stevens, of the North Carolina Agricultural Col- lege, who has recently been appointed Dean of the College of Agriculture of the University of Porto Rico, is making plans for the establishment in Porto Rico of a research laboratory for bo tan v and zoology. Of the everal attempts which have been Notes and Comment. . 3o3 made in the United States to establish permanent tropical bo- tanical laboratories in this hemisphere, this is the first that has looked to a location which is under the American flag It is doubtful if this somewhat sentimental crnsideratirn will ofTset the much more advantageous natural conditions which char- acterise other localities in contrast with Porto Rico. However, such a station, maintained in connection with the University of Porto Rico, will have great usefulness, especially in researches relating to tropical agriculture. \^arioas bulletins of the Bureau of Plant Industry bearing date of 1911 are well worth the attention of botanists. Natural Vegetation as an Indicator of the Capabilities of the Land for Crop Production in the Great Plains Area, by H. L. Shantz (Bui. No. 201), brings out the capital fact that in the area under investigation (eastern Colorado) the general conditions of soil and climate, whether favorable or unfavorable to crop produc- tion, are indicated by the character of the native plant cover. Thus, for example, the land which bears a pure short-grass cover was found to be supplied with water only in the surface foot or two of soil and for a brief period during spring and early sum- mer, while land with a uniform cover of tall grass was found to be supplied with water to a much greater depth and to offer conditions favorable to plant growth during a much longer season. Areas of greatest agricultural value, one year with an- other, are those marked by the presence of wire-grass vegetation. Bunch-grass land is best for crops during very dry years. Short- grass land (grama-buffalo-grass association) produces more than any other type during wet years, but fails in time of drouth. These are but examples of the various correlations between the natural plant cover and the crop-producing capabilities of land in the areas studied, as they are presented by the author. The careful account of plant association, added to determinations of physical conditions, especially with soil moisture and run-off are of much interest to the student of ecology and also indicate something of the great value of such an investigation to the intending settler. — V. M. S. 304 -^ The Plant World The eruption of Taal volcano on an island of the same name in the vicinity of Manila, which occurred on the thirt'eth of last January, affords botanists an opportunity similar to that of- fered by Kraktoa for studying the rehabilitation of an area over which vegetation has been destroyed as the result of vol- canic action. The accessibility of the island renders it possible to maintain almost continuous observations, and the position of the volcano in the midst of a lake suggests problems of special interest.— V. M. S. No more tangible evidence of the progress and practical character of the educational work going on in the Philippine Islands can come to us than is embodied in ' ' The Philippine Agriculturist and Forester. ' ' This is a monthly magazine start- ed in January, 191 1, and published by the students of the College of Agriculture at Los Banos. Its articles have the familiar fla- vor of our own agricultural bulletins, with an added dash of interest in rubber, fibre plants and tropical fruits, while the names of the authors would indicate that practically all of its contributions are from the native student body of the College. Much of the credit for the good work which this indicates must go to Dr. E. B. Copeland, the Dean of the Philippine College of Agriculture. 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