/■ .^v '""V* THE PLANT WORLD A Monthly Magazine of General Botany Established 1897 Edited by FORREST SHREVE Published by THE PLANT WORLD ASSOCIATION Volume 18 OFFICE OF PUBLICATION 2419-21 Greenmount Ave. baltimore, md. EDITORIAL OFFICE TUCSON, ARIZONA 1915 THE PLANT WORLD INDEX TO CONTENTS OF VOLUME EIGHTEEN, 1915 Abscission. F. E. Lloyd; Review 91 Acid Accumulation and Destruction in Large Succulents. E. R. Long 261 Agricultural Atlas of United States ; Note 50 American Ecological Society ; Note 320 Antizymotic Action of a Harmful Soil Constituent. J. J. Skinner . . 162 Appleman, C. O. Rest Period; Review 151 Armstrong, M. Western Wild Flowers; Review 293 Atmometry and the Porous Cup Atmometer. B. E. Livingston 21, 51, 95, 143 Bailey, L. H. Plant Breeding; Review 170 Bakke, A. L. Transpiring Power of Leaves; Review 222 Brenchlejr, W. E. Inorganic Plant Poisons and Stimulants; Review 203 Broun, A. F. Tropical Silviculture; Review 19 Burns, G. P. Relative Transpiration of White Pine Seedlings. ... 1 Calkins, G. N. Text-Book of Biology; Review 89 Cannon, W. A. Manometer Method of Determining Capillary Pull of Soils 11 Chemistry of Colloids. W. W. Taylor; Review 344 Cypresses and Junipers of the Rocky Mountain Region; Note 259 Desert Vegetation of America. 0. Paulsen 155 Dissemination of Virginia Creeper Seeds. B. T. Harvey 217 Doctorates in Botany; Note 346 Dunes of Lake Michigan. T. J. Stomps 205 Effect of Vanillin as a Soil Constituent. J. J. Skinner 321 Ferns of Washington. T. C. Frye and M. M. Jackson; Review. . 49 Flora of California. W. L. Jepson; Review 127 Flora of New Mexico; Note 259 Flora of Tusayan National Forest, Arizona. A. D. Read 112 Forest Climatology. G. A. Pearson; Review 150 Free, E. E. Relative Score Method of Comparison of Plant Condition 249 Fromme, F. D. Phototropism of Urediniospore Germ-Tubes; Review 172 Georgia, A. E. Manual of Weeds; Review. 48 Grafe, V. Methods in Physiology of Nutrition; Review 124 Harshberger, J. W. Vegetation of Florida; Review 220 Harper, R. M. Vegetation of Florida; Review 220 3 Harvey, B. T. Dissemination of Virginia Creeper Seeds 217 Hitchcock, A. S. Text-Book of Grasses; Review 257 Holman, R. M. Useful Drawing Camera 313 Howe, C. D. and White, J. H. Trent Forest Survey; Review. . . . 174 Humphrey, H. B. and Weaver, J. E. Natural Reforestation in the Mountains of Idaho 31 Improved Non-Absorbing Porous Cup Atmometer 7 Inorganic Plant Poisons and Stimulants. W. E. Brenchley; Review 203 Internal Temperatures of Desert Plants. H. H. W. Pearson; Review 258 Investigation of Causes of Autonomic Movements in Succulent Plants. E. B. Shreve 297 331 Jepson, W. L. Flora of California; Review 127 Klebs, G. Periodicity in Trees; Review 19 Limiting Factors and Plant Growth. A. M. Smith; Review 201 Livingston, B. E. Atmometry and the Porous Cup Atmometer 21, 51, 95, 143 Lloyd, F. E. Abscission; Review 91 Long, E. R. Acid Accumulation and Destruction in Large Succu- lents 261 MacDougal, D. T., et al. The Salton Sea; Reviews 14, 16 Manometer Method of Determining the Capillary Pull of Soils. W. A. Cannon 11 Manual of Weeds. A. E. Georgia; Review 48 Marine Algae of Peru; Note 20 Methods in Physiology of Nutrition. V. Grafe; Review 124 Montane Rain-Forest. F. Shreve; Review 168 Naming of Plant Communities; Note 176 Natural Reforestation in the Mountains of Idaho. H. B. Hum- phrey and J. E. Weaver 31 Natural Regions of North America ; Note 93 Observations in the Colorado Desert. S. B. Parish 75 Origin of the Galapagos Islands. A. Stewart 192 Parish. S. B. Observations in the Colorado Desert 75 Paulsen, O. Desert Vegetation of America 155 Pearson, G. A. Forest Climatology; Review 150 Pearson, H. H. W. Internal Temperatures of Desert Plants; Review 258 Periodicity in Trees. G. Klebs; Review 19 Phototropism of Urediniospore Germ-Tubes. F. D. Fromme; Review 172 Plant Breeding. L. H. Bailey; Review 170 Presentation of Scientific Papers; Note 204 Prize Offers; Notes 128, 319 Read, A. D. Flora of the Tusayan National Forest 112 Relation between Floras of Subantarctic America and New Zealand. C. Skottsberg 129 Relative Score Method of Comparison of Plant Condition. E. E. Free 249 4 Relative Transpiration of White Pine Seedlings. G. P. Burns. ... 1 Rest Period. C. O. Appleman; Review 151 Root Systems of Prairie Plants of Washington. J. E. Weaver 227, 273 Salton Sea. D. T. MacDougal, et ah; Reviews 14, 16 Shive, J. W. Improved Non-Absorbing Porous Cup Atmometer ... 7 Shreve, E. B. Investigation of Causes of Autonomic Movements in Succulent Plants 297, 331 Shreve, F. Montane Rain-Forest; Review 168 Skinner, J. J. Antizymotic Action of a Harmful Soil Constituent . 162 Skinner, J. J. Effect of Vanillin as a Soil Constituent 321 Skottsberg, C. Relation between Floras of Subantarctic America and New Zealand 129 Smith A. M. Limiting Factors and Plant Growth; Review 201 Standley, P. C. Vegetation of Brazos Canon, New Mexico 179 Stewart, A. Origin of the Galapagos Islands 192 Stomps, T. J. Dunes of Lake Michigan 205 Symposiums on Plant Geography; Note 225, 294 Taylor, W. W. Chemistry of Colloids; Review 344 Text-Book of Biology. G. N. Calkins; Review 89 Text-Book of Grasses. A. S. Hitchcock; Review 257 Transpiring Power of Leaves. A. L. Bakke; Review 222 Trent Forest Survey. C. D. Howe and J. H. White; Review 174 Tropical Silviculture. A. F. Broun; Review 19 Useful Drawing Camera. R. M. Holman 313 Vegetation of Brazos Canon, New Mexico. P. C. Standley 179 Vegetation of Florida. J. W. Harshberger; R. M. Harper; Review . 220 Vegetation of Katmai Region; Note 153 Weaver, J. E. Root Systems of Prairie Plants of Washington . 227, 273 Western Wild Flowers, M. Armstrong; Review 293 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published bv The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University ( )tis William Caldwell i University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDoug.»l Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelgon Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. 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Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. THE RELATIVE TRANSPIRATION OF WHITE PINE SEEDLINGS1 GEORGE P. BURNS University of Vermont, Burlington, Vermont The study of plant ecology and the study of many phases of agriculture and forestry have emphasized most clearly the neces- sity for a scientific study of the habitat and the importance of the habitat upon the distribution and development of the plant. The ecologist works with a group of plants which forms the society of plants in a given habitat. This society is named after one or more of the leading plants in the society — maple- beech, heath, Carex filiformis, etc. The plant society of the ag- riculturalist and the forester usually consists of one species or variety growirig in larger numbers. The ecologist attempts to work out the distribution of plants and to discover the laws which determine such distribution. He seeks to locate the present region where conditions are best suited for the development of any given species or plant. He has determined that the requirements in the habitat are more and more rigid the farther a plant gets from such region — its center of distribution. Such data are of the greatest importance to the agriculturalist and the forester, as they indicate the possible regions of growth for any plant and would furnish the basis for planning experi- mental work. Much of the work of the early ecologist has been descriptive, and the value of each contribution depends largely upon the training and ability of the individual writer — thus bringing in a very large margin of error. A second group of contributions begins with a detailed and 1 Read at the Atlanta meeting of the Botanical Society of America, 1913. 1 THE PLANT WORLD, VOL. 18, NO. 1, 1915 2 GEORGE P. BURNS sometimes lengthy description of the meteorological conditions of the region under consideration. These are usually taken from the nearest station of the United States Weather Bureau, and include sunshine records, air temperature records, wind records, etc. The next section in these papers gives a detailed account of the plant societies of that region, their distribution, history of their development, facts concerning the water, etc., of the habitat, but one looks in vain for any important use of the data obtained from the Weather Bureau. The writer feels that there is a mean- ing, and feels it so strongly, that he includes the data in his con- tribution, but he is at a loss to know what they mean in terms of the plant. A third group of ecologists, realizing that they can not use to good advantage the data from the Weather Bureau, has attempted to gather their own data, limiting themselves for the most part to a study of evaporation. Many valuable data are being collected by this group of workers. The method consists, roughly, in determining the amount of water evaporated from porous cups in different habitats. These cups are' usually placed near the surface of the ground even when determining the evap- oration in forest societies. A fourth group of ecologists is studying the effects of me- teorological conditions on plant activities. Recording instru- ments for percentage of sunshine, percentage of humidity, air temper, ^ure, soil temperature, etc., are placed not at some high elevation above the plant society under consideration, but under the same conditions as those in which the plants are working. For example, Livingston has attempted to determine the rela- tion of the evaporation from the porous cup to the transpiration from a given plant. He believes that the porous cup is the best means yet devised for measuring the factors which influence evaporation. But such data of themselves are not valuable until the relation of the evaporation from the porous cup to the transpiration from the living plant can be determined. He, therefore, works out the sun-shade ratio for white, black and brown atmometers, and several plants. This, to my mind, is one of the most promising fields of research in ecological botany. TRANSPIRATION OF WHITE PINE SEEDLINGS 3 The final answer to questions raised by the ecologists can only be found by experimental work, as in any other line of botany. During the past three seasons the writer has been studying the evaporation from porous cups placed in seed beds in the Vermont State Forest Nursery, and the present paper is an at- tempt to express the results of evaporation from the white and black atmometers in terms of transpiration from the seedlings of Pinus strobus. It is not necessary to describe in detail the seed beds. The usual nursery bed was used. These are 12 feet long, 4 feet wide surrounded by a frame 1 foot high. Three kinds of covers were used. One was covered with wire; a second, half covered with lath; and a third, entirely covered with lath. In each bed were placed black and white atmometers. The amount of transpiration was determined by weighing plants which had been previously potted. The data recorded represents the result of 15 four-hour periods during the first half of August, 1913. The effect of external conditions upon the various objects used in the experiments showed only a general agreement be- tween evaporation and transpiration. In the no-shade, half- shade and full-shade beds the agreement of the atmometers was rather striking. In comparing the plants with the atmometers, it was seen that although the response was not similar, yet there was a closer relation between the black atmometer and plants than between the white atmometers and the plants. Using the black atmometer as a basis for comparison, it was found that the relative transpiration (transpiration divided by evaporation) in the three beds was as follows: No shade 0.06332 Half shade 0.0346 Full shade 0.0088 With these coefficients it is possible to calculate the transpira- tion from the white pine seedlings from the evaporation from a second set of black atmometers which had been running all 2 In the report of the secretary of the Botanical Society given in Science New Series No. 998 p. 259 some of these values were out of order. 4 GEORGE P. BURNS season. Figured on this basis, from the beginning of the vege- tation period to the time of the experiment it was possible to determine that the approximate amount of water transpired from each tree was as follows: No shade 21 x cc. Half shade 8 x cc. Full shade x cc. That is, the seedling in no-shade used 21 times, and the seedling in half-shade used 8 times as much water as the one in full-shade. The questions naturally arise which was the best tree, which had the greatest amount of ash, what was the chemical composi- tion of these trees? Trees harvested July 31 were about 8 to 10 weeks old. The average green weight of the trees based upon the weight of 500 seedlings in the case of the "no-shade" and ''half-shade" trees and upon the weight of 1000 seedlings in the "full-shade" trees, was as follows : Green weight Dry weight No shade 0.304g- 0.063gr Half shade 0.166 0.034 Full shade 0.090 0010 The dry weight of the plant produced in "no-shade" was a little more than six times as great as that produced in "full- shade," and the plant produced in "half-shade" was almost three and a half times as heavy in dry weight as the "full-shade" plants only about one-half as heavy as the "no-shade" plant. The ash content of the plants was next determined and is here given in percentage of dry weight only. This showed that the total ash content was: No shade. 8.29% Half shade 9.35% Full shade 10.20%, The nitrogen content for the three trees in percentage of dry weight was: ■ TRANSPIRATION OF WHITE PINE SEEDLINGS 5 No shade 2 . 18 Half shade 2.70 Full shade 6.89 These figures show that there was a difference in the material taken from the soil by the three plants. Returning to the figures given for transpiration, it is seen that the plants which transpired the most water, the plants in no-shade beds, contained the smallest per cent of ash and that the plants which transpired only one-twentieth as much water contained the largest percentage of ash. Again taking the total amount of ash absorbed, it is seen that there is no very evident relationship between the amount of water absorbed and the amount of ash taken up, twenty times the water is accompanied by only five times the ash; eight times the water by three times the ash. The plants then are able not only to select the minerals which they take from the soil but also to control the degree of concentration of the solution which enters the root hairs. Pfeffer in describing the experiment of Schlosing, who found that tobacco plants grown under bell jars did not grow as well as others, says — "Though a variety of other factors enter into play here, such experiments suffice to show that transpiration favors the absorption of the constituents of the ash." This statement should be closely questioned — when applied to our pine seedlings. Oven has shown that even a clear glass cover greatly increases the nitrogen content and from the fact that the plants in full-shade and half-shade beds already have a surplus of ash over the no-shade or normal plants, it seems highly prob- able that some of the other factors may be more important in determining the amount of ash absorbed. The lack of growth of seedlings in full-shade cannot be due to lack of water or the .amount of ash. Lubiminko remarks that pea pods grown in the dark seem to have a higher percentage of ash. He asso- ciates the percentage of ash with light rather than transpiration. According to the work of Pagnoul and Oven, the nitrogen con- tent of sugar beets and potatoes increase as much as ten times when plants are grown in the shade. Oven associates this with 6 GEORGE P. BURNS absorption and assimilation and Pagnoul says that in the shade the nitrogen salts cannot be used. The data on white pine show no such great differences in nitrogen content in the no-shade and full-shade trees. White pine seedlings contain only about three times as much nitrogen when grown in the full-shade. The data given in this paper indicate that the explanation of the differences in size and chemical composition of the three groups of trees must be sought along the line of photosynthesis and assimilation rather than along the line of absorption and transpiration. AN IMPROVED NON-ABSORBING POROUS CUP ATMOMETER JOHN W. SHIVE The Johns Hopkins University, Baltimore, Md. Since Livingston's1 description of the rain correcting atmometer appeared in 1910, a large number of these instruments have come into use. Up to the present time, however, the instrument has had the disadvantage of not being self-contained. The automatic mercury valves which operate to prevent the water, absorbed by the porous cup in times of rain, from entering the reservoir, are externally situated. This renders the valves liable to break- age and rather difficult of adjustment. For this reason it seemed well to modify the instrument in such a way as to be self-contained and at the same time to reduce the liability of breakage and the difficulty of adjustment to a minimum. With this end in view the present form of the instrument was devised. The arrangement of the different parts of the instrument is shown in diagram in figure 1. From the reservoir (F) two glass tubes (A and B) extend upward through a paraffined cork stop- per, and then through a two-perforate rubber stopper into the porous cup, one passing to the tip of the cup, the other just to the upper surface of the rubber stopper. These tubes are of small bore, about 0.8 mm. inside diameter. Each is bent into a U and continued upward as A ' and B' . One (A ') extends through the paraffined cork stopper and ends about 5 cm. above it. The other (B') extends upward 6 cm. to 8 cm. and is again bent into a U (inverted), thus forming a loop, and terminates near the bottom of the reservoir. The tube B is expanded into a small bulb C, at its lower extremity,- and the tube A' , is expanded into a similar bulb 1 cm. to 2 cm. from its lower end. The tube E, 1 Livingston, B. E., A rain-correcting atmometer for ecological instrumentation. Plant World 13: 79-82, 1910. 7 D E B IB A NON-ABSORBING ATMOMETER 9 is about 1.2 cm. in diameter, and forms a shallow, inverted funnel with the lower surface of the paraffined cork stopper. This serves to conduct air bubbles, which may catch on the under surface of the stopper in filling the reservoir, to the exterior. The tube extends 5 cm. above the cork stopper, and is graduated to tenths of cubic centimeters. The zero point on the tube serves as a zero point in filling the reservoir. To install the instrument the paraffined cork stopper, into which the tubes A A', B and E, have been properly fitted, is tightly appressed into the mouth of the reservoir F. A suffi- cient amount of clean mercury is allowed to fall from a pipette into the openings in the upper end of each of the tubes A' and B, to form a column 5 cm. to 6 cm. high in tube A', and slightly more than this in tube B. After the porous cup has been placed in position and the reservoir filled with distilled water, a rubber tube is attached to the free end of the filling tube A' , and gentle suction is applied. Water rises from the reservoir into the tube B' ', at the same time that the mercury in this tube is drawn into the bulb C, where water passes freely and rises in the tube B, filling the porous cup. When the cup is filled water passes into the tube A A' , the mercury in this tube having been drawn into the bulb D, where the water is allowed to pass freely and escape into the rubber tube, which is then removed. The mercury in the bulbs C and D, drops back into the tubes below. To prevent water loss from the reservoir by evaporation through the tube E, and to prevent the entrance of water through this tube from without in times of rain, a vial is placed over the end of this tube. A suitable vial is also placed over the end of the tube A', to ex- clude dirt. The instrument is now ready for operation. To replace the cup with a new one it is only necessary to re- move the old cup from its support and to place the new cup into position, after which suction is applied to the tube A ' , as in in- stalling. A- water evaporates from the surface of the cup, the mercury rises in tube A, and falls in tube A', coming to rest with the mercury level in A, slightly higher than in A', the difference in the height of the two columns depending upon the height of the V 10 JOHN W. SHIVE cup above the water level in the reservoir. The mercury in B B' ', is drawn into the bulb C, where water rising from the reser- voir is freely allowed to pass, supplying, in the usual way, the water lost from the surface of the cup. The mercury columns in the tube A A', and B B', remain in equilibrium in the position indicated in figure 1, so long as the water loss from the surface of the cup by evaporation equals or exceeds the absorption from without by any part of its surface. In times of rain, when the water loss from the surface of the cup by evaporation is less than the absorption from without, the automatic mercury valves become reversed. The mercury column falls in A, and rises in A', at the same time that the mercury in bulb C, drops into the tube below and rises in the tube B' (the height to which the mer- cury rises in this tube depending upon the height of the cup above the water level in the reservoir), thus effectually preventing water from entering the reservoir from this direction. The readings obtained give the actual evaporation minus the error introduced by the volume change required for the operation of the mercury valves, the value of the error thus introduced depending upon the number of complete reversals of the valves. Harvey2 has estimated the error permitted by the Livingston mercury valves to be no greater than 0.01 cc, assuming the glass tubing used to have an inside diameter of approximately 0.8 mm. and assuming the cup to be not more than 30 cm. above the water level in the reservoir. In the present modified form of the instrument the volume change required for the operation of the automatic mercury valves is no greater than that esti- mated by Harvey. It is evident, therefore, that the error involved in one or several complete reversals of the valves is quite negligible excepting in cases where extreme accuracy is essential. 2 Harvey, E. M., The action of the rain-correcting atmometer. Plant World 16: 89-93, 1913. A MANOMETER METHOD OF DETERMINING THE CAPILLARY PULL OF SOILS W. A. CANNON The Desert Laboratory, Tucson, Arizona The apparatus to be briefly described has been in use by the writer at the Desert Laboratory for two years and has been found of service as a convenient means of determining the capil- lary pull of soils used in experimental work. No attempt is here made to relate the results to be given with results achieved by using the direct method of measuring the ascent of water, which is the method commonly employed. Whether the results of the two means of determining the capillarity are comparable, as they possibly are, is not germane to the present purpose. As used the apparatus is very simple and can be put together in a few minutes in any laboratory. It consists, in brief, of a U-shaped mercury manometer, with open ends, and a soil con- tainer holding about 500 cc, and, in addition, a reservoir of about 500 cc. capacity for water. The reservoir is connected with a T-shaped glass tube having a three-way cock. A rubber tube connects one free end of the T-tube with the manometer, and another rubber tube, which should be relatively long, connects the third end of this tube with the soil container. The various portions are easily attached by clamps to a horizontal iron rod which is fastened to a ring-stand. When the several parts of the apparatus are assembled water is put in the reservoir and the whole is so manipulated that water, to the exclusion of any air, fills the tubes which unite the container, the reservoir, and the manometer. The reservoir and the container are about on the same level so that, if the cocks are left open, water will stand equally near the upper edges of both. After the rubber tubes and the uniting glass tubes are filled with water the reservoir should be somewhat more than half 11 12 W. A. CANNON full. With the cocks joining the reservoir and the container open, so that water may flow between the two, the container is raised or lowered sufficiently to bring the water in it to a depth of about 2 cm. when the cocks are closed. A small plug of glass wool is put in the bottom of the container, to prevent the escape of the soil, and all air is removed from the wool by gentle pack- ing. The apparatus is then ready for the introduction of soil. The actual manipulation, so far as is necessary to give it in detail, is as follows: The container is filled with soil. The cocks are open, permitting the rise of water and its flow out of the reservoir, and the soil is at once run through several times with a small glass rod. The last operation is for the purpose of pro- moting the settling of the soil as well as to prevent the premature collecting of air bubbles at the bottom of the soil container. All of this time, it should be understood, the water is flowing freely from the reservoir into the container and is rising in the soil. As soon as the soil appears to be uniformly settled the cock beneath the reservoir is so turned as to cut off the flow of water from it and, at the same time, to connect the container with the manometer. The position of the mercury is observed at. this moment and the rise is watched until the upward move- ment ceases, or until the mercury falls. The uppermost point reached by the mercury is considered the measure of the capillary pull of the soil under the conditions of the test. When the mercury falls the experiment is ended. If it is desirable, as it generally is, to repeat the test, and if there are no air bubbles in the bottom of the soil container, it can be done in one of two ways. Either the soil can be removed and the test begun anew, as must happen should air be found in the bottom of the container,, or the following manipulation can be resorted to. Water is immediately run into the container and the soil is run through with a glass rod, after which the water is turned off and the position of the mercury noted and its rise observed as before. This operation can usually be repeated several times before the collection of air bubbles in the bottom of the soil compels the termination of the test. As illustrating tj^pical results the following experiments can A METHOD OF DETERMINING THE PULL OF SOILS 13 be cited. Tests of sand, and of* adobe, separate and mixed, were made. When mixed, equal parts of each were taken. In all cases the largest soil particles, or, more exactly, intrusions, like small pebbles, were removed by passing the soils through a coarse sieve. After this each kind of soil tested was separated into two parts by sifting through sieves of two sizes, namely, 20-mesh and 40-mesh (that is, 20 and 40 meshes to the inch). Repeated tests were made in every instance.- For the mixed soil, the highest point reached by the mercury was 22.5 mm. The 20-mesh sand registered 6 mm., and the 40-mesh sand, 9.5 mm. Unsifted adobe, '20-mesh, stood at 18 mm., and 40-mesh, 25 mm. The capillary pull of the sifted adobe soil is not easily determined, owing, probably, to its peculiar physical nature. An interesting and characteristic quality of the tests with sand, especially the coarse sand, is that the mercury rises very quickly at first, but for a brief time, after which it maintains an even height for a long period. For example, the mercury in a test with 40-mesh sand remained at 9.5 mm. for over three hours. Other results might be given as well, but those presented are sufficient to show the behavior of the soils mentioned as regards the quality in question. It is recognized that the method is not without theoretical, and, possibly, practical objections. Of these, possibly the most serious is the inevitable difference be- tween soils, even of the same kind, when treated in such tests, as regards their compactness. To this it can be suggested that settling under water, and parallel treatment otherwise so far as possible, makes the objection possibly less serious for this method than for other methods. The objection holds, in other words, quite as well for the direct observation of the capillary rise of water in soils. Errors from such a source, in the manner of de- termining the capillary pull in the way here described, can be minimized also by making the tests several times, and under parallel conditions of temperature, which is not feasible by the direct method referred to. Finally, the manometer method commends itself as a convenient and striking means of demon- strating an important physical characteristic of soils, whether, which is unimportant, it is an entirely new method or not, and independent of the probability that it is theoretically not ideal. BOOKS AND CURRENT LITERATURE The Salton Sea: Geography and Geology. — Monographs such as The Salton Sea1 are typical of the spirit of cooperation which is a dominant tendency of modern science. Dr. MacDougal has associated with himself no less than nine collaborators, each of whom deals with a distinct subject, but all of whom cooperate to give a comprehensive picture of a unique region. It is fortunate for science that when the Colorado River last overstepped its bounds and made a new lake, the Desert Laboratory of the Carnegie Institution was ready to investigate the complex and important changes, both geographical and botanical, which have since ensued. In its geographical and geological portions the book centers around three main points, namely, the nature of the Cahuilla Basin, its unique departures from the typical features of a desert basin, and the rela- tion of low forms of life to the production of tufa. The opening chap- ter is most fittingly allotted to Professor W. P. Blake, the first scien- tist to describe the region. The ancient lake which once occupied the Salton Sink and rose to about 40 feet above sea level before overflow- ing to the Gulf of California has been named Blake Sea in his honor. He discusses its geological history. The Cahuilla Basin in which it is located is a structural trough, the continuation of the Gulf of Cali- fornia. According to Professor Blake's view, which has hitherto pre- vailed almost unchallenged, the upper end of the trough, forming the part now known as the Salton Sink, was a part of the Gulf until recent geological times. Then it was gradually cut off by the growth of the delta of the Colorado River. Above the delta the isolated end of the Gulf formed a salt lake which eventually dried up and disappeared. From time to time, however, a diversion of the Colorado River, such as occurred in 1905, produced a temporary body of fresh water. According to this interpretation the Salton region possesses few of the characteristics of a genuine desert basin. The next contributor, Mr. Sykes, accepts Professor Blake's view. 1 The Salton Sea: A Study of the Geography, the Geology, the Floristics, and the Ecology of a Desert Basin. 4to, pp. xi + 182, pis. 32, maps 2. Carnegie Inst. Washn. Publ. 193. 1914. . 14 BOOKS AND CURRENT LITERATURE 15 His chapter describes the general surface features of the country, and discusses its exploration and early mapping. It forms the natural introduction, and would have been placed first except for the desire to pay a graceful tribute to Professor Blake's pioneer explorations. The next chapter, by Mr. Free, goes further into the question of the origin of the ancient lake and the general character of the basin. A series of Tertiary strata, now uplifted and folded, lies at the foot of the surrounding mountains. This formation is clearly of subaerial origin, a piedmont deposit washed down from the highlands under conditions of aridity. It indicates that for a long time during the Tertiary era the basin was not occupied by the sea, and was essentially like the other basins of the Southwest. In far more recent times, that is within the last few thousand years, the basin has also been free from the sea, for innumerable shells show that it was pccupied by fresh water. Moreover, the strands of Blake Sea, which may date back no more than 500 years indicate a very brief stand of the lake at the level of overflow. If an arm of the sea were cut off, the water must have stood at an approximately uniform level for many centuries while the delta was being formed, and there ought to be a pronounced bench in the rock, but none is found. Hence Free suggests that the whole region may have been above sea level for a long period. At first it was a simple trough. This was gradually depressed, but the delta of the Colorado was built up as fast as the. land sank and a genuine basin was thus formed in its rear. This was occupied by water only when the Colorado temporarily shifted its course. Aside from excep- tional periods of this sort, the Salton region appears to have had a history like that of the typical desert basin. Free's interpretation needs further study, but it seems likely to prevail. The relation of the Salton tufas to organic life suggests that the chemical deposits of interior basins can be understood only by a study of the effect of different types of bacteria or algae upon chemical reac- tions. Papers by Ross and Vinson give details as to the concentra- tion and composition of the water of the Salton Sea at frequent inter- vals since the last inundation. Pierce follows with an interesting ac- count of micro-organisms in highly concentrated brines. He shows that living algae are found in water of a surprisingly high degree of salinity, and that their activity varies in harmony with changes in the degree of concentration. Brannon considers another phase of the same matter. He immersed pieces of wood in Salton water for long periods. When the water was sterilized, little decortication took place. Chemi- 16 BOOKS AND CURRENT LITERATURE cal activity seems to depend upon the presence of certain bacteria, some of which were isolated. Jones confirm this conclusion by show- ing that both now and in the past the Salton tufas have been deposited only in the presence of algae. The presence of minute organism, is probably of much more importance chemically than has commonly been realized. In this respect and in other ways this monograph on The Salton Sea is likely to prove of great value in stimulating new lines of thought. — Ellsworth Huntington. The Salton Sea: Floristics and Ecology. — The papers of Parish and MacDougal occupy more than half of the Salton Sink volume. They give, detailed and in broad lines, answers to many questions of great interest concerning desert vegetation as a whole, the biology, dispersal and wandering of its plants, the relation of a sink to sur- rounding elevated land masses and especially concerning revegetation of bared land, the means which enable plants to get a foothold and the causes which make them again disappear. The latter part of the book, MacDougal's treatment of the revegetation of the beaches, is the prin- cipal one, giving as it does a vivid picture of movement and activity in nature under almost unique conditions. The paper of Parish shows us, as it were, the stage upon which the play is performed, or the ordinary order of things undisturbed. So we learn that the Salton Sink with its Atriplex vegetation is bordered on both sides by zones of more or less related vegetations of which the Opuntia zone is especially interesting, showing the curious feature of cacti living on the rim of the Sink without entering it. The Sink flora of which a very careful list is given, numbering 200 species, including sporophytes, is a part of the Colorado desert flora which is the western fringe of the arid lower Sonoran flora; from the southeast to the northwest species drop out successively, so we under- stand that the conditions of the Sink are very exclusive; only 122 species are indigenous. These are tabulated with regard to ecological classes, 51 are annuals, 30 perennial herbs, 23 shrubs, etc., numbers which indicate desert conditions, as emphasized elsewhere by the pres- ent writer. The factors in control of distribution are the chemical and physical character of the soil and especially its water content; of the formations accordingly established by Parish the xerophytic formation occupies an area exceeding the combined areas of all the other formations; its main plants are: shrubby Atriplices, Prosopis, Cercidium, Parasela, BOOKS AND CURRENT LITERATURE 17 Olneya. As general characteristics of the xerophytic formation Parish states that shrubs and suffrutices are prevalent but only in few species, the individual plants are separated by large intervals, have a condensed growth and small, often early deciduous leaves. There are no succu- lents at all. Induments have not been evolved to any marked degree, and there are only two species with storage roots. Seedlings of the desert shrubs have never been found (except of Parosela) although the seeds are known to be able to germinate readily. In MacDougal's paper it is described how the plants move onto the beaches as these are laid bare. The lake receded in 1907-1912 from 40 to 59 inches yearly, but the breadth of the emersed beaches varied of course with the angle of their slope. This angle also determines the duration of the wet stage of the newly emersed beach, steeper slopes desiccating faster than gentle ones, and this condition again determines the alkalinity. For the study of the differences of the beaches five areas were selected, of which two only need be named here, viz., Imperial Junction with a slope 1 in 300, and Travertine Terraces with a slope 1 in 20. The latter locality had a gravelly soil in which the waves cut banks during each winter when the evaporation was slight and the lake consequently receded slowly. All the areas were often visited during the years 1908-1913, every change in the conditions was noted and every plant was followed from seedling to death or to perfect establishment. Although propagating bodies of hundreds of species must have been carried into the lake by wind or water only 60 species in all appeared on the beaches. Most of these were species inhabiting the lower parts of the basin above water, but there was also a number of introduced species and some species native to the valley of the Colorado River. Comparing the beaches in the same place we find a considerable variation in number and composition of introductions in the different years, suggesting differences in the dispersing agencies (wind) during the time when seeds were ripe for dispersal. During later years some species are dropping out from the pioneer class, which fact is ascribed to the effect of the increasing amount of chlorine in the water of the lake. The beaches of the different areas studied had in part different pio- neers. For instance, at Imperial Junction Atriplex fasciculata, Spiro- stachys, Suaeda and Scirpus paludosus were common pioneers, rare THE PLANT WORLD, VOL. 18, NO. 1, 1915 18 BOOKS AND CURRENT LITERATURE or absent at Travertine Terraces, where Distichlis, Salix and Populus were establishing themselves in numbers. Also numerically there was a difference: the first named locality with its gentle alkaline slowly desiccating slopes presenting better opportunities for germination had a greater number of pioneers than Travertine Terraces. On the other hand very few pioneers were able to maintain them- selves when the beaches were drying out. Thus, at Imperial Junction, the number of species was reduced from 17 in 1907 to 5 in 1912, and here no secondary introduction took place. At Travertine Terraces the reduction in number of pioneers was counteracted by secondary introductions of more or less xerqphytic plants. Still, nowhere had the beaches reached a stable condition, equivalent to that in which they had been before the making of the lake. Of the species appearing on the beaches about 80 per cent might have been brought by wind, but only 12 per cent could only have been brought by wind. Of other agencies, birds have probably played a role, and some instances were found where ephemeral run-off streams had carried species down from the land above. Flotation played a very important part in the transportation of seeds; flotsam collected at the water side gave a number of seedlings. MacDougal has tested a number of seeds in the laboratory, keeping them in Salton water and observing the duration of flotation and the germination. The plant- lets were also "stranded" in imitation of the probable action in the lake. It came out that "in 10 of the 15 species tested the flotation period of the seed, which in the different species may be from a day or two to four months or more, may be followed by the survival of the plantlet for periods of such length as to render them liable to be carried about by many agencies." Thus buoyant plantlets may remain in the surface of the water for a long time and finally strike root on the beach. Inferential as this reasoning is it gives us the doubtless true but somewhat paradoxical conception of plant-dispersal by water in desert areas. This is beautiful evidence that "the origination of qual- ities or structures upon which dissemination would depend, in many instances at least, has no possible connection in a causal way with the agencies themselves" (quoted from MacDougal's "general discussion"). To this short review must be added congratulations to the authors for the publication of this magnificent volume, pleasing by its fine appearance, by its many beautiful plates, and attractive on account of the great interest attaching to the subject, the systematic manner BOOKS AND CURRENT LITERATURE 19 in which the investigation has been begun and carried out, and the thorough treatment of the whole result of the investigation. As true naturalists the writers have not concealed the shortcomings in their investigation — -let us hope that still existing problems will provoke continued publications on the Salton Sink. — Ove Paulsen, Copenhagen. Periodicity in Trees, — Rhythm and periodicity may not be so much a part of the life of the plant as has been taken for granted by physiologists. The beech has been cited for many years as imperturb- able in its resting period, and not to be awakened during the winter time by any high temperature exposures, ether threatment, etc. Pro- fessor Klebs1 of Heidelberg has been able, however, to maintain the European beech (Fagus silvatica) in continuous growth during the winter, and concludes that the countless experiences of the species with alternating favorable (summer) and unfavorable (winter) seasons have made no permanent impress on the organism in the way of an acquired rhythm. Confirmatory results with oak, ash, and hornbeam were obtained. Professor Klebs used a small enclosed chamber in a dark room, illuminated by tungsten lamps of a total intensity of 200 candle power, and the entire dark room with 1000 candle power. Moisture and temperature control and registration were secured. — D. T. MacDougal. Tropical Silviculture. — Under the title of Sylviculture in the Tropics, Broun2 incorporates in one volume a discussion of the problems of silviculture as applied to the tropics. The author frankly states that had he undertaken the publication on his own accord he would have restricted its application to the portions of the tropics and of the sub-tropics in which he had gained his experience. The author's work in India, Ceylon and Soudan is utilized to make many practical appli- cations. Aside from this the publication does not offer anything new to the art of silviculture. — H. N. Whitford, Canadian Commission of Conservation. 1 Klebs, G., tjber das Treiben der einheimischen Baiime, speziell der Buche. Abh. d. Heidelb. Akad. d. Wiss. Math-Naturw. Kl. 3 Abhandl. 1914. 2 Broun, A. F., Sylviculture in the Tropics. Pp. 309, figs. 96. Macmillan and Company, 1912 ($3.00). NOTES AND COMMENT Dr. Marshall A. Howe, of the New York Botanical Garden, has published a paper on the marine algae of Peru, based chiefly on col- lections made by Dr. Robert E. Coker while investigating the fisheries resources of that country. The waters of the Peruvian coast are tem- perate except at the extreme north, and are inhabited chiefly by tem- perate and sub-tropical algae, among which gigantic members of the Laminariaceae are conspicuous. Dr. Howe's report is notable in that the collections of Dr. Coker, made incidentally to other work, have nearly doubled the known alga flora of Peru, and in the fact that the Peruvian Department of the Interior has aided in the publication of the sumptuously illustrated report, which forms Volume 15 of the Memoirs of the Torrey Botanical Club. The Cambridge University Press announces the appearance of two new periodical publications. The Annals of Applied Biology is a quar- terly organ of the Association of Economic Biologists, devoted chiefly to pathology, horticulture, forestry and tropical economic botany. The Annals of the Bolus Herbarium is edited by Professor H. H. W. Pearson and is devoted to taxonomic, ecological, and other botanical work emanating from South Africa. The New York State College of Forestry at Syracuse University announces the establishment of an Eastern Forest Products Laboratory to be located in the State Forestry Building which will be ready for occupancy in the summer of 1915. In the State Forestry Building, for which the State appropriated a quarter of a million dollars, there will be nearly 14,000 square feet given up to experimental laboratories outside of laboratories especially for educational work with students. ATMOMETRY AND THE POROUS CUP ATMOMETER* BURTON EDWARD LIVINGSTON r;«*"~ The Johns Hopkins University, Baltimore, Md. .-/,■ ■#' ^»9^ I INTRODUCTION The importance of the porous cup atmometer in studies of plant and animal environment, and the fact that the literature of the instrument fails to present, in adequate manner, several very important considerations in regard to operation and in- terpretation of atmometric readings, have led to the presentation of this paper. For the sake of completeness it is here attempted to state all essential points as far as they have been worked out, whether or not such statement may involve repetition from the writer's earlier papers. In short, this publication aims to put before the worker in porous cup atmometry the various matters requiring his attention, many of which might not be appre- ciated without years of experimental acquaintance with the subject. ►Since so many names for the atmometer have been proposed by various writers, it is perhaps not out of place here to state that the term now practically in general use was first employed by Leslie2 in 1813. This word was adopted as official by the Com- mittee on Evaporation of the Vienna Meteorological Congress in 1874. The committee emphasize the fact that the word atmometer "possesses the merits of seniority and a correct classical derivation." It is constructed on parallel lines with the familiar barometer, thermometer, hygrometer, anemometer, etc., and thus enters readily into climatological and meteorological discussion. 1 Botanical contribution from the Johns Hopkins University, no. 43. 2 Leslie, J., A short account of experiments and instruments depending on the relations of air to heat and moisture. Edinburgh, 1813. 21 THE PLANT WORLD, VOL. 18, NO. 2, 1915 22 BURTON EDWARD LIVINGSTON ATMOSPHERIC EVAPORATING POWER AND ITS MEASUREMENT IN GENERAL Conditions Controlling Evaporation This is not the place for a detailed discussion of evaporation and its controlling conditions, but enough space may be taken to point out certain features of evaporation and certain re- quirements of atmometric measurements in general. In the first place it is to be emphasized that the water surface from which evaporation proceeds is as truly a control of the rate of water loss as are the atmospheric conditions. This consideration at once frees us from the still prevalent idea that there is any- thing fundamental and absolute in evaporation rates obtained from a free water surface. To make this clear, assume a water surface of known area, the water held in a pan or tank of known volume, the surface being a known distance below the margin, and the material and form of the container being also defined. Further assume a certain complex of aerial conditions, wind, temperature, humidity. Under such conditions it may be found that water is lost from the exposed surface at a given rate per hour, which may be reduced to an hourly rate from unit of surface. Now let the water container be altered in size, all other conditions remaining the same, and we shall find that the rate of loss per unit of area is not the same as before. Let the area remain the same and let the form or material of the container alone be altered, and another change in rate of water loss occurs. Of course it is understood that the changes here supposed must be of adequate magni- tude, otherwise the resultant differences in rate might hot be detectable by the extremely crude methods usually employed for measuring the rate of water loss. All the details of the con- struction of the water pan must have their influence upon the rate of evaporation per unit of surface, under any given set of surroundings. If, however, two instruments are assumed to be exactly alike, and if they be exposed to the same complex of external condi- tions, then the rates of loss should be the same. If, in this case, the external conditions to which two like pans are ex- ATMOMETRY AND THE ATMOMETER 23 posed be altered in the same way for both pans, then both rates of loss should change, but this change should be the same for both instruments. A somewhat less obvious result follows if two different kinds of water pan are exposed first to one external complex and then to another. For such a case, let it be supposed that one instrument loses twice as much water per hour as does the other, under the first conditional complex. Under the second com- plex of external conditions this relation between the two rates of loss no longer holds; the first instrument does not then lose just twice as much as does the second. In other words, if one of these unlike pans be standardized to the other, the coefficient of correction (by which the loss from one pan may be multiplied, in order to give the loss from the other) would be different for each new set of external conditions. It appears that the principle just dealt with is but vaguely appreciated by many students of atmometry, a conclusion reached by a perusal of the meteorological literature of evapor- ation; in spite of frequent publications establishing the influence of size, shape, etc., of pans used, workers in this field still per- sist in employing a variety of pans and tanks, thus rendering their measurements of but little lasting or generally compara- tive value. If it might be remembered that the evaporation rate depends upon the water surface and upon the surroundings of this surface (both below and above), then this misapprehen- sion should be avoided. From what precedes it is clear that no form of pan is any more a natural standard for measuring evaporation than is any other. When pans are to be employed in atmometry it is only essential that all pans be alike, if the measurements thereby obtained are to be compared. In any event, the pan used must be described in detail if the results are to be of any value to other workers. Another consideration that appears worthy of emphasis here is this, that the exposure of several atmometers must be com- parable if the readings are to be so. Thus, if one of two like pans be placed at ground level and the other at some elevation 24 BURTON EDWARD LIVINGSTON above the soil, there can be obtained therefrom no definite in- formation as to the relative intensities of evaporation in the two localities, at the' same level. It may be said only that the evaporating power of the air at one level in one locality bears such and such a relation to the same power at another level in the other locality. The exposure of an atmometer needs to be specified as much as does the nature of the instrument. These points apply as well to other forms of atmometer as to the form employing a free water surface. Different sized paper disks on the Piche and Piche-Cantoni forms (with their horizontal, saturated papers giving off water both above and below) are also influenced in their relative rates of water loss by changes in wind, temperature, etc. It is also clear that the alter- ation of evaporation rate from any instrument employing paper may not be at all the same as the corresponding alteration for any free water surface, these alterations being both effected by the same change in external conditions. Thus it is obviously impossible to reduce Piche readings, for example, to terms of depth from a pan of water, though this has often been attempted. A coefficient for this reduction can of course be obtained for any given set of external conditions, but when the conditions alter we must expect the coefficient to alter also. Likewise, evaporation rates from different forms or sizes of porous clay cups are dif- ferently affected by the same alterations in the surroundings, and it is quite impossible to obtain a coefficient by means of which the readings of one form may be reduced to those of another, excepting with specified surroundings. Nor can porous cup losses be reduced to losses from pans or paper disks. Reduction of Readings The apparent success which has sometimes appeared to at- tend attempts to derive coefficients for the reduction of evapora- tion rates from one form of atmometer to those from another form3 3 Russell, T., Depth of evaporation in the United States. Mo. Weather Rev. 16:235-239, 1888. Livingston, B. E., The relation of desert plants to soil moisture and to evap- oration. Pub. 50 of the Carnegie Institution of Washington. Washington, 1906. ATMOMETRY AND THE ATMOMETER 25 has doubtless been largely due to the fact that the general period of observation employed involved such slight alterations in the effective surrounding conditions that the crude methods of meas- urement failed to detect the variations emphasized above. It is of course possible, also, that certain different changes of the ex- ternal conditions might be found, which might happen to affect the rates of water loss from different forms of atmometer in the same way and to the same extent, but it is highly improbable that such changes are frequently to be encountered in the diurnal or annual march of atmospheric conditions anywhere in the world. Where only slightly refined measurements are made, and where the change in external conditions or the difference between the instruments lies within certain limits of nature and magnitude, it may frequently occur that the rates of water loss from one form of instrument may apparently agree in their fluctuations with those from another form. A closer study usually shows such agreement to be only apparent. The writer's own experience in this connection is of illustra- tive value here. When the porous cup was first employed in the study of plant transpiration (summer of 1904, at the Desert Laboratory; see Pub. 50 of the Carnegie Institution, already cited), the earlier literature of evaporation was not available and the now obvious mistake was made of supposing that the readings from the cup might be reduced to depth units as lost from a free water surface, without regard to alterations in ex- ternal conditions. The data presented on page 28 of the publica- tion just mentioned show clearly, however, just the sort of fluc- tuation in reduction coefficient, for different hours, that would be expected from the discussion just presented. Below the table of calibration data occurs the statement, "The fluctuations in the ratio are probably in large part due to the failure of slight air currents to accelerate evaporation from the dish as much as they Operation of the porous cup atmometer. Plant World. 13 : 111-118, 1910. Many other instances of similar sorts are cited in: Livingston, Grace J., An anotated bibliography of evaporation. Mo. Weather Rev. 36: 181-186, 301-306, 375-381, 190S; 37:68-72, 103-109, 157-160, 193-199, 248-252, 1909. This was re- printed, repaged, in pamphlet form, Washington, 1909. Reference may be made to this bibliography for papers on evaporation antedating 1908. 26 BURTON EDWARD LIVINGSTON hastened that from the porcelain cylinder." This is no doubt correct to a considerable extent, though temperature and humid- ity changes may also have had an influence. Nevertheless, in spite of the clear evidence that the ratio of hourly loss from cup to hourly loss from pan actually fluctuated as much as from 84.7 to 114.4, an average of all the hourly ratios was taken as showing the relation of the two rates for the entire day. Such a mean value does, of course, represent the period for which it was ob- tained, but the night hours were not included in that study. If the different days of the general period were nearly similar, and if the average ratio employed had been derived by use of night as well as day rates, then the reductions of cup readings to units of depth (given on p. 29 of the same publication) should be approximately correct. As it is, these reductions are at least highly questionable excepting in a merely approximate way. The mistake just mentioned befogged the writer's apprecia- tion of the general atmometric problem for several years, and the real condition of affairs in this connection came to conscious- ness but slowly. In the summer of 1909 the method of standard- izing porous cups was altered so as to make use of a water surface as a basis. At this time it was clearly appreciated that the kind of pan used must be highly important, but the possible difference between the effects of a given change in the surroundings, upon the rates of loss from cup and pan, was quite lost sight of — not- withstanding the suggestion of this difference already made in 1906. Accordingly, the fullest account of the porous cup at- mometer so far published (the writer's paper of 1910, already cited) gives an erroneous method of reduction of evaporation rates from this instrument to units of depth from free water. The experimentation upon which this procedure was based lasted for several summer months, and showed satisfactory agreement between the reduction coefficients from day to day, no doubt because no very great climatic changes were then encountered and the effective conditions for each day of the series were much like those for any other. During the following summer, however, a period of extraordi- narily hot weather brought the coefficient of the standard cup (of ATMOMETRY AND THE ATMOMETER 27 earlier work) to a value much lower than that exhibited in 1909, and suggested the carrying out of a series of experiments bearing upon the effect of temperature upon the value of this coefficient of the standard cup, as compared to the standard pan then em- ployed. These tests clearly showed that, as the temperature rises, the coefficient of the standard cup, referred to the standard pan, decreases, and it proved to be possible, by manipulating the temperature, to give this coefficient almost any desired value, within a broad range. It thus became clear that a rise in temperature produces a relatively greater increase in evaporation from the cup than from the pan. It may be suggested that the higher the temperatire of the air the more pronounced should be the convection currents about the cup, while the correspond- ing alteration in convection currents over the free water surfac'e is probably but slight, owing to the horizontal position of the latter. These comparisons of cups and pans were carried out, as far as possible, without breeze, so that the effect of differences in air convection should have been pronounced. Whatever may be the physical explanation of the findings of these experiments, they made it very obvious that it is im- possible to reduce the rate of loss from a porous cup to units of depth from a water surface, and this put an end to cup stand- ardization with the pan as a basis. The coefficients of the cups of 1908 were therefore recalculated, to the older basis of standard cups, and the fact of this return to the original method was stated in a later paper.4 The reasons for this change have never been presented until now. This whole matter of the influence of the atmometer itself upon the evaporation rate per unit of evaporating surface is quite clear from the fundamental principle that the rate of water loss depends upon the conditions of the entire surroundings, not merely upon the evaporating power of the air. The special con- ditions due to the nature of the instrument accompany the in- strument from place to place and affect the evaporation rate by variously modifying the influence of the surrounding conditions 4 Livingston, B. E., A rotating table for standardizing porous cup atmomcters. Plant World 15: 157-162, 19)2. 28 BURTON EDWARD LIVINGSTON at each locality. In other terms, the exposure of the evaporating surface to the remainder of the instrument forms an important and usually not negligible part of the general exposure. Thus, to say that atmospheric evaporating powers are to be comparably meas- ured only by giving the evaporating surfaces similar exposures, implies that the entire nature of every instrument should be as nearly alike as possible; what may be called the internal or instrumental exposure of the active surfaces must be the same if the external conditions are to register comparable effects. The mutual influences of the various conditions within and without the instrument, and the summed influence exerted by all these conditions acting together, are far too complex to admit of cor- rection being applied to bring the readings from different kinds of atmometers into a comparable state. Such corrections may become possible in time, through refined physical studies, but numerous attempts simply to deduce the evaporation rate of one kind of instrument from various measured conditions of the surroundings have not furnished results that are at all encour- aging in this direction. The literature contains many experi- mentally derived formulas for this sort of reduction, but none seem to have obtained a completeness or precision adequate to render them available excepting for the roughest sort of approx- imations. Summarizing the points thus far brought out, hazarding a repetition for the sake of emphasis, the evaporating power of the air — that is, its power to remove water vapor from a surface of liquid or solid water — can never be directly measured only with reference to some standard evaporating surface. For the preparation of duplicate evaporating surfaces it is necessary, not only that the areas of these be the same, but that their forms or shapes be also the same. Furthermore, all of the immediate surroundings of these water surfaces excepting the conditions of the air, the effectiveness of which are to be studied — must also be alike. The surroundings include the magnitude and form of the water mass behind the exposed surface, the sort of container which holds the water mass in place, etc. In brief, if the evaporating power of the air is to be measured at different places, or for ATMOMETRY AND THE ATMOMETER 29 different time periods at the same place, it is quite essential that the several atmometers employed shall be as nearly alike, in all particulars, as is possible. Of course it is physically impossible to construct several instruments exactly alike, and the slight differences which occur should always be cared for by calibration, as in the case of anemometers, thermometers and the like. Any alteration of the instruments that may occur during the period of operation should also be cared for by recalibrations carried out from time to time. It is positively essential that some single form of instrument be adopted throughout each series of comparative measurements, and it is quite impracticable— excepting in a roughly approximate way — to derive coefficients by which readings from one form of instrument may be made comparable with those from another form. Units of Measurement Connected with a discussion of atmometry in general, should go some consideration of the kind of units to be used in com- parative studies of evaporation rates. The misapprehension mentioned above, that free water somehow furnishes the true standard evaporating surface for such studies, is usually accom- panied by another misapprehension, that units of depth are somehow the truly fundamental units, in terms of which the evaporating power of the air should always be measured. This proposition is probably to be related to a desire, on the part of meteorologists and climatologists, to compare rainfall with evaporation. Rainfall is measured in depth units and its measurement is not attended with serious difficulties; the size, shape and ma- terial of the gauges exert relatively but negligible influence upon the readings, and the variations in exposure commonly allowed are not great enough to be considerable. Hence it may have seemed to follow, that evaporation (which is obviously a sort of negative rainfall) should be measurable in the same kind of units. As has been indicated, however, many con- ditions influence the rate of loss from an atmometer that do not 30 BURTON EDWARD LIVINGSTON seriously affect the readings of a rain gauge. To illustrate, a small pan of water loses relatively (per unit of surface) more by evaporation than does a large pan, while the size of rain gauge funnels is without appreciable effect upon the amount of water taken in, per unit of funnel area. It may be remarked, also, that the very presence and operation of an evaporating surface decreases the evaporating power of the air in its vicinity, while the receiving or absorbing action of the rain funnel is quite without influence towards decreasing rainfall. This is an im- portant consideration for those who regard units of depth of evaporation and precipitation as comparable units. The prop- osition is much more complicated than here indicated, but limited space precludes a more thorough analysis, Since it is aimed simply to measure the amount of water lost from a specified standard evaporating surface, it is clear that the only rational units thus to be employed are those of weight, or mass. Volume units are as satisfactory as those of weight only when the relatively small variation in specific gravity caused by changing temperature may be neglected; which may be safely done in practically all cases where atmometric measure- ments are employed. The investigator should be conscious of such neglect, however. Units of depth cannot be conveniently employed excepting with free water surfaces; other forms of atmometer lend themselves more readily to the employment of weight or volume units. In the case of pans or tanks of water, depth units (which are to be avoided, in any event, because of the widespread but mistaken idea that these are directly com- parable to similar units of precipitation) may of course be trans- formed into weight or volume units when the necessary co- efficient is given — but always for some specific size, shape, etc., of pan. Of course the most essential principle in this regard is that the same units must be used for all the instruments the readings of which are to be compared. (To be continued.) NATURAL REFORESTATION IN THE MOUNTAINS OF NORTHERN IDAHO HARRY B. HUMPHREY Bureau of Plant Industry, Washington, D. C. AND JOHN ERNST WEAVER University of Minnesota The factors affecting the natural reforestation of a fire-denuded area may, in general, be said to be the same in Idaho and Ore- gon as in Maine or Minnesota. There may be and actually are differences in detail as to what species of herbaceous and shrubby plants may prepare the way for the more delicate seed- lings of those trees native to the particular locality. But the principle prevails everywhere that certain plants or plant socie- ties are antecedent and probably essential to the appearance and permanent establishment of a forest. The first step in the reforestation of a fire-swept area is the restoration of the condi- tions necessary to insure the germination and vigorous early development of the tree seedlings. The presence of humus in the soil insures a certain degree of moisture conservation and the retention of certain ingredients of plant food so easily lost by drainage. Experience and observation teach us that however hardy, however well equipped, may be such trees as those which come to occupy the most trying situations, they were doubtless so sensitive to environmental factors during their first years as to have perished but for the fact that there must have prevailed a proper and essential balance of physiologic factors. To estab- lish this balance may have required but a year, or it may have taken a much longer time. In this paper it is not our purpose to discourse on the laws which regulate natural reforestation in different sections of the 31 32 H. B. HUMPHREY AND J. E. WEAVER continent; notwithstanding the fact that great practical benefit would very likely result from an extended and careful scientific study of the factors which determine such growth. Ordinarily the denudation of any considerable area of conif- erous forest land means an end of that chapter of forest his- tory. Witness, for example, the thousands of acres of "pine barrens" in Minnesota, Michigan, and Ontario where but a few decades ago stood splendid mixed forests of white and Norway pine, and spruce and fir, holding their own against time and the elements. It is because man in his exploitation of these forests imposed upon their territory an absence of certain growth factors vital to natural reforestation that it has since been impossible for these coniferous species to reestablish themselves. Time has shown that protection from destructive ground fires will in many instances promote natural reforestation. Zavitz,1 who has made an extensive and careful study of forest conditions in Ontario, states that the reforestation of the denuded land areas is a problem involving fire control rather than one calling for the hand planting of pines. In Sincoe County, for example, a cer- tain district comprising approximately 50,000 acres, and at one time covered with valuable red pine, still supports enough old seed-bearing red and white pines to insure reforestation were it not for the fact that destructive ground fires are allowed to run. That the production of a coniferous forest depends greatly upon a real balance of physiological factors can not be denied. No matter how favorable may be the moisture supply, an ex- cessive rate of evaporation will inhibit or make impossible the growth of a crop of seedlings for as long as a single season. Then, again, extreme exposure to sunlight may prove destructive. Or, two or more factors in excess or deficiency may prevent altogether the growth of young plants. The following example is illustrative. On Kamiak Moun- tain, an isolated butte near Viola, Idaho, evaporation stations were maintained during the summer of 1913. One Livingston's porous cup atmometer was operated on a south slope a few 1 Zavitz, E. J., Report on the Reforestation of Waste Lands in Southern On- tario, 10, 1908. REFORESTATION IN NORTHERN IDAHO • 33 meters from the top of the ridge, and a second atmometer was placed just over the ridge on the north slope. Neither station was occupied by mature trees, although Douglas fir and yellow pine grew on the ridge and north slope on both sides of the prairie in which data were obtained. Coniferous seeds were avail- able at both stations and pine cones were actually lying scat- tered about on the ground. On the sheltered slope a few pine and fir seedlings had established themsleves, while none occurred near the station on the south slope. The average daily evaporation in the area occupied by these small seedlings, from May 10 to September 5 was 19 cc, while the exposed side of the ridge gave an average daily evaporation of 27.7 cc. The greatest stress on the south side for any seven-day period occurred during the week ending August 29, when the average daily evaporation reached 50.8 cc. On the north side during the same interval it averaged only 34 cc. per day. Figure 1 shows a sharp ecotone between prairie and forest. This spur of Tekoa Mountain is illustrative of many similar situations of transition from grassland to forest. The shel- tered northeast slope supports a dense growth of yellow pine, Douglas fir, and some tamarack, but these invade the prairie of the windward slope with great difficulty. Figure 2 shows a similar situation and illustrates the effect of exposure to wind upon the few trees that have succeeded in growing upon the ridge. Likewise the destruction by fire of the accumulated humus constituting that all-important part of the forest floor may re- tard for many years the reappearance of young trees of sufficient vigor to endure. A study of the physiology of reforestation without taking into account the intimate relation of other plants to the reappearance and permanent establishment of the forest growth would be incomplete; for there can be no doubt concerning the vital impor- tance of these plants as agents modifying the factors influencing the restoration of that physiological balance so essential to the incipient growth of coniferous seedlings. The Thatuna Hills, a western spur of the Bitter Root Moun- Fig. 1. A sharp ecotone between prairie and forest. The sheltered north- east slope is clothed with a dense forest of yellow pine, Douglas fir and some tamarack. Tekoa Mountain, Washington. Fig. 2. A situation similar to that in Figure 1 showing the effect of exposure to wind upon the yellow pine. 34 REFORESTATION IN NORTHERN IDAHO 35 tains and located in northern Idaho, support a rich coniferous flora consisting of the Western larch, Larix occidenialis, the white fir, Abies grandis, the Douglas fir, Pseudotsuga mucronata, Englemann spruce, Picea engelmanni, yellow pine, Pinus pon- derosa, white pine, Pinus monlicola, lodge pole pine, Pinus contorta var. murrayana, white cedar, Thuya plicata and the Western yew, Taxus brevifolia. These hills, rising to a maxi- mum elevation of 4950 feet above sea level, offer an unusual variety of slope exposure, canons, and moisture supply. The western and southwestern slopes of these hills receive at all times the full brunt of the prevailing winds which sweep across the many miles of open prairie and desert of south central Wash- ington and northern Oregon and not infrequently attain a ve- locity of 50 miles an hour. These wind-swept slopes are clothed with a fairly dense growth of Douglas fir, tamarack, and yellow pine except in sheltered ravines where one may find the white cedar, the white fir and an occasional spruce. Pure forests of yellow pine are not unusual, but mixed forests of pine and Douglas fir, or of tamarack, white fir and cedar are more abundant, and it is interesting to note that where reforestation has occurred, slopes formerly occupied by any one of these forest tj^pes have in most instances been reclothed with the same species. Figure 3 shows a north slope which was cut over more than 25 years ago, while in figure 4 the steep southern exposure just opposite is shown. A belt transect 2 meters wide from near the top of the north slope to its foot showed this forest to be com- posed of 30% tamarack, 26% white fir, 39.5% cedar, 4% red fir, and 0.5% yellow pine. The exposed opposite slope was studied in a similar manner and revealed a decidedly different composition with 10% tamarack, 40% white fir, 14% red fir, and 36% yellow pine. Superficially the north slope appears to be clothed with a nearly pure tamarack forest, due to the more rapid vertical growth of this species. The cedars are mostly small; in fact many are mere seedlings. An actual count of the annual rings showed that they came in after the other trees had by their shade made con- ditions less xerophytic. Such mixed forests of tamarack, white fir and cedar are very characteristic of the sheltered slopes and ravines (fig. 5). The large percentage of white fir shown to occur 36 H. B. HUMPHREY AND J. E. WEAVER on the south slope occupies dense thickets near the protected base. That the south slope supports a very open forest (mostly yellow pine and Douglas fir above the ravine) is shown by the fact that the average number of trees per square meter is only one, as compared with 3.5 per unit area on the north slope. No less characteristic of the two exposures are the shrubs of the undergrowth. Opulaster pauciflorus, Ceanothus velutinus and Fig. 3. A young forest of white fir, tamarack, and cedar occupying a cut- over north slope in Thatuna Hills. Salix scouleriana make up the chief shrubby growth on the south slope, often covering many square meters exclusively. On the north slope both Opulaster pauciflorus and Ceanothus velutinus occur but rarely, while Vaccinium memhranaceum is more abun- dant than Salix scouleriana. Coptis occidentalism Clinlonia uni- flora, Thalictrum occidentale, Milella stauropetala, Galium sp., Asarum caudatum, Anemone piperi, Pyrola bracteata, Cytherea REFORESTATION IN NORTHERN IDAHO 37 bulbosa and species of Smilicina, all found here, are typical plants of the more moist slopes and contrast markedly with Calamagrostis suksdorfii, Bromus marginaius , Pteridium aquili- num var. pubcscens, Penstemon pinelorum, Phaca mortoni, Aster Fig. 1. The steep south exposure just opposite that shown in Figure 3, clothed with an open forest of yellow pine, red fir, and tamarack. conspicuus, Anaphalis margarilacea var. occidentalis, Aniennaria racemosa, Pedicularis racemosa, and Berberis repens, found on the more open south mountain side. THE PLANT WORLD, VOL. 18, NO. 2, 1915 38 H. B. HUMPHREY AND J. E. WEAVER About 26 years ago many square miles of these hills were overrun by a fire which destroyed more or less completely much of the virgin timber, leaving here and there a few living trees rep- resenting the different species to serve as seed trees in subse- Fig. 5. A virgin forest of white fir, tamarack and cedar. Characteristic plants are Acer glabrum var. douglasii, Lonicera ulahensis, Vaccinium membran- aceum, Ribes lacusire, Thaliclrum occidenlale, and Disporum spp., under which is a carpet of Smilicina sessili folia, Coptis occidentalis, Asarum caudatum, and Clin- lonia uniflora. Thatuna Hills, Idaho. quent years. These burns covered chiefly the north and north- east slopes of the mountains. In these mixed forests of white REFORESTATION IN NORTHERN IDAHO 39 fir, tamarack, Douglas fir and cedar, the thick-barked tamarack suffered least and often only the trees of this species less than 6 to 8 inches in diameter were killed. This gave rise to what are apparently nearly pure forests of tamarack; but in most all cases sufficient seed trees of the other species were left to insure re-seeding; and at present a new generation of white fir and tamarack are especially prominent (fig. 6) . In some of the more accessible canons, lumbering has been carried on and in some places the operations of the lumberman have been followed by ground fires, some of which must have occurred not more than 5 years prior to the time when the authors made their observations. On these most recent burns the predominating plants were Epilobium angustifolium, and Carduus breweri and occasional specimens of Erigeron acris. These three species along with other annuals and biennials and some young willows afforded conditions suitable to the early growth of the scattered seedlings of Larix, Pseudotsuga and Pinus ponderosa, which had already established themselves. On those slopes formerly occupied by a mixed forest of larch, Douglas fir, white fir, spruce, and white cedar, it was interesting to note that in the older burns these same species had succeeded in reestablishing themselves. Cutting off a large number of the trees of each species at the surface of the ground and counting the annual rings, it was found that the most xerophytic species, i.e., Douglas fir, yellow pine, and larch, were the oldest, and therefore, the first to establish themselves. It is also a matter of interest to note that a period of 2 or more years must elapse before any but a limited number of even the hardiest of these trees can launch into permanency. Naturally, those slopes and situations affording the greatest degree of protection from evaporation and excessive heat and light produce a more abundant stand of those annuals and biennials which pre- pare the way for the coniferous forest of later years. And observation has shown that the preparation of exposed slopes for coniferous seedlings is considerably delayed because of the lim- ited number of individual herbaceous plants produced in any season and the consequent slow accumulation of humus. 40 H. B. HUMPHREY AND J. E. WEAVER During the month of August, 1910, the greater part of north- ern Idaho and much of eastern Montana were swept by one of the most extensive and destructive forest fires ever experi- enced in that part of the country. In many heavily wooded Fig. G. Interior view of a forest burned over about 26 years ago. The older trees are mostly tamarack under which the white fir is especially abundant. canons the draft was so violent during the fire and the heat so intense as to destroy every vestige of life above ground (fig. 7) . The town of St. Maries, Idaho, lies against the slopes of foot- REFORESTATION IN NORTHERN IDAHO 41 hills which, prior to 1910, were covered with a more or less mixed forest of coniferous trees comprising the following species: Pseudotsuga mucronata, in practically all situations; Pinus pon- derosa, abundant on south slopes and in exposed and rocky situations; Larix occidentalis associated with Abies grandis and Pseudotsuga; Pinus monticola and Thuya plicata accompanied Fig. 7. An old "burn" in Ferry County, Washington. Typical representation of the destruction by fire of the coniferous forests of the Northwest. by individuals of Pseudotsuga and Abies, confined generally to the canons and rich levels at the bases of north slopes. These mountain slopes were overrun by fire on August 21 and 22, 1910. Seeming to represent fairly the average forest condi- tions for northern Idaho, it was decided that here if anywhere 42 H. B. HUMPHREY AND J. E. WEAVER would be the most satisfactory place to carry on a study of the problem of natural reforestation. The region was not visited during the summer of 1911, hence a complete account of the plant successions and list of species can not be furnished. But observations made on east, north and northwest slopes on May 25, 1912, established the fact that in all probability Funaria hygrometrica and Marchantia polymorpha were among the very first of the pioneers to help reclaim the unshaded and charred soil. It was also possible to identify the following angiosperms of the preceding year's growth: Carduus breweri, Erigeron sp., Epilobium anguslifolium, Arnica cordifolia, Salix sp., Physo- carpus pauciflorus, and Erythronium grandiUorum. It is not unlikely that other more perishable species were present, but identifiable remains were quite wanting. Plants observed on May 25, 1912, and belonging to the 1912 growth were the following: predominant everywhere, Epilobium anguslifoliwn, individuals of which varied in size from that of mere seedlings to plants 12 to 18 inches in height. These (fire weeds) often occur as abundantly as 34 individuals per square meter, and certainly do much toward reducing light intensities and evaporation. Thousands of the smallest of these were succumbing to an epidemic of Aecidium. Other herbaceous plants observed were Carduus breweri, everywhere abundant; and here, as observed elsewhere, one of the first seed plants to secure a footing in forest burns. Associated with Epilobium and Carduus were Erigeron acris, Arnica cordi- folia, Anlennaria luzuloides, and Salix scouleriana. These spe- cies all depend upon wind for seed distribution; and doubtless this accounts in some measure for the fact that they are among the very first seed plants to take possession of fire devastated areas. Every inch of ground seemed to be occupied by Funaria, a plant of very considerable importance to the complete develop- ment of other forms, because of the double role it plays in the conservation of soil moisture and the formation of humus. Other plants were Physocarpus pauciflorus, Rosa gymnocarpa, Poienlilla sp., Mitella stauropeiala (abundant), Lepiotaenia mul- REFORESTATION IN NORTHERN IDAHO 43 Hilda, Rubus nutkanus, Disporum trachycarpum, Arenaria macro- phylla, Antennaria luzuloides, Coplis occidenlalis, Viola canina, two species of Lathy rus, Vicia sp., Zygadenus venenosus, Frilil- laria lanceolala, and Erythroniwm grandiflorum. The three last named plants occurred in considerable abundance and upon investigation it was found that their bulbs were, in every case examined, at depths of 5 to 7 inches below the soil surface. These bulbous plants could have been hardly so abundant had they de- pended upon winds or other natural carrying agents for the distribution of their seed. It is also quite probable that many if not all the shrubs in which an underground root-stock develop- ment obtains were able to withstand the effects of the fire. In fact, one can with difficulty account for the abundance and general distribution of such plants in any other way, for their growth habits, are such as to preclude the possibility of so much development in a single season from seed. It is of interest here to note that in spite of the terrific heat which must have pre- vailed over those mountain slopes, except where the undergrowth was dense, a considerable depth of humus remained intact. Where this was wholly consumed and the soil had been washed bare by rains there was a fairly complete turf of Funaria and Marchaniia along with certain herbaceous plants already given. The effects of this forest fire were more profound in certain parts of the forest than in others, depending somewhat upon the topography of the devastated region. In the " draws" or small lateral canons where growth conditions were such as to produce the most excellent stand of white pine (Pinus monii- cola), Douglas fir, white fir and cedar, the fire was most destruc- tive, leaving no trees alive. Whereas, on lateral or secondary ridges it was frequently observed that from 25% to 75% of these species, 'including yellow pine, survived the heat. These con- stituted the seed trees so valuable in the reforestation now going forward. A diligent search was made for any seedlings of the cone- bearing trees characteristic of the region under observation, and a few were found. A limited number of these (all were Larix occidenlalis) were from seed germinated in 1911, but the 44 H. B. HUMPHREY AND J. E. WEAVER majority were but a few weeks old at the time of observation. They were indeed scarce; not more than sixty to eighty per acre on east and north slopes and none at all on south and south- east or southwest exposures. In two instances it was observed that as many as fifteen to twenty seedlings were growing in one spot as though a cone had become planted and all its viable seeds had germinated. The area investigated seemed to show no signs of any other conifer, which fact corroborates observations of a similar nature made 2 years earlier in a certain denuded sec- tion in the Thatuna Hills. In September, 1912, another trip was taken to the hills about St. Maries, and it was found that between May 25 and the September date many seedlings of Thuya, Larix, Pseudolsuga and a few of Abies had sprung into existence, apparently from seed of scattered surviving parent trees in the immediate neigh- borhood. Their distribution was very irregular. In some areas of a square meter or more none could be found, while in other more favored spots the seedlings would average as many as eight per square meter. The ground occupied by these seedlings was well covered with a mulch of the dead leaves and stems of such herbaceous plants as have already been described for the region. An examination of denuded south slopes where the original forest growth consisted of an abundant stand of Pinus ponderosa with scattered individuals of Pseudolsuga mucronata resulted in the enumeration of the following plants: Funaria hygromelrica, Achillea sp., Symphoricarpos racemosus, Pieridium aquilinum var. pubescens (most abundant), Epilobium paniculaium, Carduus breweri, all, excepting Pieridium, about equally abundant and intermingled so as to form a semi-shaded area. Stray speci- mens of Aster douglasii, Rosa nulkana, and Gnaphalium sp. were observed; and in spots Berberis repens was predominant. The most careful search failed to reveal any coniferous seed- lings even in the most favorably shaded ravines of these south slopes, an absence due, no doubt, to insufficient soil moisture and excessive evaporation, although the writers had no recording instruments in this field. That these same south mountain REFORESTATION IN NORTHERN IDAHO 45 sides and their ravines and canons will in the course of time be reclaimed by a new growth of yellow pine and Douglas fir can not be prevented so long as ground fires do not occur and natural growth conditions are not obliterated. An example of the yellow pine, our hardiest tree pioneer, tak- ing possession of an extremely xerophytic situation was care- fully observed on Kamiak Mountain during the summer of 1913. Near the top of the mountain where the soil is rocky, Fig. 8. A prairie on the exposed south slope of a quartzite butte near Viola, Idaho. It is being invaded by yellow pines which occupy the crest and the north- west side of the butte and the ravine in the foreground. Pinus ponderosa has succeeded in establishing itself on the ex- posed south slope. A weekly record was kept of the evaporating power of the air and of the moisture content of the soil near the edge of a group of pine trees under cover of which a few three- and four-year-old seedlings were growing. On May 10 a 25 cm. core of this quartzitic soil contained 21% of its dry weight (at 105°C.) of water. The soil moisture gradually decreased until on July 24 only 7.4% remained, and this was reduced to 4% 46 H. B. HUMPHREY AND J. E. WEAVER by September 5. The wilting coefficient of this soil free from rocks is 10%, and. records show that after July 20 of 1913 no moisture was available in the first 25 cm. of soil. During the whole period from May 10 to September 5 the average daily evaporation was 24 cc. and during the week ending August 29 it ran as high as 44.8 cc. daily; and still the seedlings were not Fig. 9. The northeast side of the same butte shown in Figure 8. Douglas fir and tamarack are the chief components of this forest. killed! In fact the soil mulch of needles and the shade afforded by the parent trees kept down the evaporation considerably both from soil and air, as compared with a prairie station a few meters lower down the mountain slope. 2 Weaver, John Ernst, Evaporation and Plant Succession in Southeastern Washington and Adjacent Idaho. The Plant World, 17: 273-294, 1914. REFORESTATION IN NORTHERN IDAHO 47 This, we believe, is an extreme case, but it illustrates possi- bility of tree growth. The junior writer has shown2 that although the yellow pine stage in succession is usually preceded by shrubs, especially Opulaster pauciUorus, Prunus emarginata, Spiraea corymbosus, or species of Ceanothus, it is still able to invade the prairie even without the protection of an intervening shrubby stage (figs. 8 and 9). In a region such as the Pacific Northwest where summer rains are rare or altogether wanting, a new growth of coniferous trees depends upon soil moisture conservation. Soil moisture in sufficient amount to tide seedlings over a four months' period of drought and sunshine depends upon the presence of sufficient humus to retain the moisture and at the same time support a forest cover-growth of early maturing plants which will afford some protection to the tree seedlings of all but the most xero- phytic species such as the yellow pine and Douglas fir. That the growth of herbaceous plants and shrubs may be so dense as to preclude the development of the young conifers not in- frequently happens. That the preclusion of tree seedlings is usually due to light is a question to be determined by experi- ment and in the field. Repeated observations and measurements of the soil moisture content and the evaporating power of the air together with light values show conclusively that, although the soil moisture may be far more than sufficient for tree growth and the humidity of the air relatively high, yet when the light values drop to yi of normal sunshine our hardiest pioneer, the yellow pine, is excluded. These observed facts invite the inference that light is here the factor of prime importance. Of soil moisture and humus there may be plenty, but if light beyond a certain degree is shut out these seedlings will not be found. BOOKS AND CURRENT LITERATURE A Manual of Weeds. — This delightfully written book1 forms a part of the series of Rural Manuals edited by Dr. L. H. Bailey. The vol- ume begins the subject by denning a weed as "a plant that is growing where it is desired that something else shall grow." The duration of life of the different kinds of weeds is discussed, also some general rules for preventing the growth of weeds, and the financial loss due to weeds. We are told that the loss to Minnesota alone from dockage because of weed seeds amounts to $2,000,000 annually. Weeds may be useful because they enforce tillage. This discussion is followed by a brief account of the dissemination of weeds and chemi- cal herbicides. Then follows the descriptive list of the weeds of the United States and Canada. The descriptions are all ample and most of the weeds are figured. These drawings are for the most part excel- lent. It would be difficult to recognize quack grass on p. 62, to dis- tinguish Setaria viridis and Setaria glauca, 32 and 33. To these and a few others detail drawings of the spike and the floret would have aided in recognition. A most useful feature of the book is the listing of all common names. Thus for Johnson grass there are given eight English names, for the common horsetail, six. The accepted common name is given in bold faced type followed by the botanical name. This is a most commenda- ble feature. Time of bloom, seed time, range and habitat all precede the description.* In some cases then, the author gives a little history on the introduction of the weed. When poisonous, something is said about its attack on animal and man. When the plant is useful for food or in medicine, the fact is mentioned. This is followed by means of control of the weed. The statements are very concise and will be most helpful to those who are interested in this important subject. Some of the plants described are weeds only in a few places in East- ern North America. It is always difficult to draw a sharp line between 1 Georgia, Ada E., A Manual of Weeds, with descriptions of all of the most troublesome plants in the United States and Canada, their habits of growth and distribution, with methods of control. Pp. 593, 385 illustrations by F. Schuyler Mathews. The Macmillan, Company New York. 1914. 48 BOOKS AND CURRENT LITERATURE 49 a weed and a plant that is not injurious. A plant may be a weed in one place and not in another. Epilobium spicatum is a most trouble- some weed in the northwest. It is, however, seldom seen in the southern Minnesota or in Iowa. Its range in the Manual is not correct, nor is the range correct for Ranunculus acris. This species is rare in Iowa, although common eastward and in the Lake Superior region. The figures of Lepidium apetalum and Lepidium virginicum should be trans- posed. Aside from a few such slips, the Manual is well prepared and is a worthy companion of other treatises on weeds, that have appeared in recent years. The make-up of the book is splendid. The volume should find a place in the public school library, where books of this kind are needed to supply information to those* who are studying weeds, and it will also prove a most serviceable and valuable book to many college students.— L. H. Pammel. Ferns of Washington. — Frye and Jackson's little book, The Ferns of Washington,4 is doing much to promote a more general knowledge of the ferns of that state. The edition is a limited one, only 500 copies having been printed. The writers find in the state, 30 species of Poly- podiaceae, and 66 species of pteridophytes in all. The habitat and general range of each species is given, but not the range within the state. The work has a key to families and keys to genera and species. These keys are admirable in that just as few technicalities as possible are introduced into them. The families, genera, and species are all described. The plates made from photographs and drawings aid greatly in the identification of species, and add much to interest in this attractive group of plants which form such a conspicuous feature of the vegetation in many portions of the state. — George B. Rigg. 4Frye, T. C. and Jackson, Mabel M., The Ferns of Washington. Reprint from Aril. Fern Jour. 3: 65:83 and 97-108, 1913, and 4: 6-14 and 41-57, 1914. Pp. 60, pi. 20. Lowman and Hanford, Seattle, 1914. (10.40.) NOTES AND COMMENT An Agricultural Atlas of the United States is being prepared by the Office of Farm Management in Washington, under the immediate di- rection of Mr. 0. E. Baker. The Atlas will exhibit cartographically the latest statistics of crops, live stock, forest products, and farm prop- erty, and will show the distribution of areas under irrigation or dry farming. An entire section of the Atlas will be devoted to climate, and it has been carefully planned to exhibit just those aspects or in- tensities of climatic conditions which are of importance to vegetation and to crops. There will also be a section devoted to hypsometric, geological, soil and other physical maps. The completed Atlas will be of great usefulness in educational and research work, as well as for reference. A tract of land near Greenfield, New York, has been given to the state for the purpose of preserving a large ledge of fossil algae situated upon it. A shelf of Cambrian limestone has been planed off by glacial ice so as to expose sections of Cryplozoon, a hemispherical calcareous marine alga. The tract will be named Lester Park, in honor of its donor, and it will be noteworthy as the first fossil botanical garden — ■ although it is by no means the first fossilized botanical garden. 50 yrx ATMOMETRY AND THE POROUS CUP ATMOMETER BURTON EDWARD LIVINGSTON The Johns Hopkins University, Baltimore, Md. II THE MAIN FORMS OF ATMOMETER Choice as to Form of Instrument From what has been said in the last section the question arises : if the readings of one form of atmometer cannot be reduced, by mathematical treatment, to readings that might have been had from some other form of instrument (operating in the same place and at the same time), then by what criteria is the investigator to decide what sort of instrument to employ in a series of compara- tive measurements? Obviously, from the very nature of evapora- tion and from the medley of conditions by which it is influenced, the kind of evaporation to be studied must form the basis for this decision. Where it is desired to approximate the rate of water loss from reservoirs and other large bodies of water, the floating pan is doubtless the most suitable instrument; it exposes a free water surface in much the same manner as does the reservoir itself. Where the study in hand involves the measurement of the evap- orating power of the air as this affects plant transpiration, some form of saturated paper or porous clay surface is to be chosen; such surfaces may be exposed in a manner fairly comparable to the exposure of transpiring plant parts. To study evaporation from soils, a box or pan of moist soil seems more logical as an instrument than does a pan of water, though paper and porous clay surfaces may be adapted to this need. In short, the surface by means of which the evaporating power of the air is to be meas- ured should possess as nearly the same form as possible and 51 THE PLANT WORLD, VOL. 18, NO. 3, 1915 52 BURTON EDWARD LIVINGSTON should be given the same kind of exposure as have the surfaces . upon which the action of evaporating power is to be studied. Aside from this general principle, however, there are various advantages and disadvantages connected with the use of each form of atmometer so far devised. A few considerations in this connection may find place here. The Open Pan or Tank One of the main difficulties encountered in operating free water surfaces of considerable extent arises from the secondary wind effect. Increased wind velocity increases the evaporation rate, but at the same time increases the extent and alters the form of the free water surface, throwing it into ripples or waves. Thus the effect of rapid air movement cannot ever be studied with free liquid surfaces; the fluctuation of the condition to be studied causes marked alteration of the instrument itself. Furthermore, with high wind there is great danger of mechanical removal of water from the pan, by spray and splashing. To prevent splashing it is essential to allow a portion of the lateral walls of the container to project above the water sur- face, and these projecting walls introduce variations in the effects produced by external changes. With a high wind the effect of the lateral protection may be negligible, with but slight air currents this effect is much more marked. In general, it is of course relatively more pronounced for small than large pans. Another serious difficulty in tank operation arises from the fact that the depth of the water surface below the margin of the tank and the amount of water beneath the surface can be main- tained only approximately constant, this usually by spasmodic additions. Here evaporation itself alters the nature of the ex- posed surface by changing the height of the projecting rim and the amount of water present. Also, the addition of water in times of rain is always a source of serious trouble, further com- plicated by the fact that raindrops frequently cause splashing and formation of spray. Besides the addition of water by rain and its mechanical removal by rain impact and by wind action, there is frequently ATMOMETRY AND THE ATMOMETER 53 danger of removal of water by animals, especially small birds, which can rest on the edge of the tank while drinking. More than that, small animals, especially insects, fall into the water and often remain floating, thus seriously altering the surface. To avoid such disturbance wire screens must be introduced. These modify the wind action seriously and thus complicate the instru- ment, for all instruments with screens must have similar screens. It is scarcely practicable to screen tanks from small insects, the wind effect is so greatly modified by fine-meshed wire cloth. In dealing with the evaporating power of the air as an en- vironmental condition for organisms, the free, water surface is practically useless beyond a rough approximation; it is next to impossible to give the evaporating surface any but a horizontal position (barring wave motion) and it cannot conveniently have any other form than that of a plane. Since it is essential, in such environmental studies, to give to the instrumental evaporat- ing surface approximately the same exposure as that presented by the animal or plant surfaces to be dealt with, it is clear that only water-imbibing surfaces (e.g., paper, porous clay) can thus be conveniently employed. Finally, even fair accuracy of reading for short periods has never been possible with free surfaces; only small pans can be carefully weighed, the instrument must be protected from wind during the process of weighing, which occupies considerable time, and the errors thus introduced become relatively very large when periods of minutes or hours are employed. The Piche Atmometer {Fig. 1) The Piche instrument,5 having a disk of saturated blotting paper held horizontally against the lower (otherwise open) end of a graduated glass tube, which is closed above, possesses a num- ber of advantages over the free water surface. The evaporating 5 Piche, A., Note sur l'atmismometre, instrument destinee a mesurer l'cvapo- ration. Bull. Assoc. Sci. France 10:166-167, 1872. In this connection and in that of the Piche-Cantoni atmometer, see: Livingston, B. E., Paper atmometers for studies in evaporation. Plant World 14: 281-289, 1911. Diagrams are there presented, and are reproduced in the present paper. s Fig. 3. Fig. 1. Diagram showing essentials of the Piche atmometer. R, water reservoir; D, saturated paper disk, the latter supported against base of reservoir by metal disk (C). Spring (W) is attached by clip (F) to reservoir and applies pressure to D. (Reprinted from Plant AVorld 14: 286, 1911.) Fig. 2. Diagram showing essentials of the Piche-Cantoni atmometer. R, burette reservoir for water, filled at will through tube (T) from higher supply, cut off by cock (P). D, absorbent paper disk, as in Piche instrument, held against the top of supply tube (E) by double spring (W) attached at F and applying pressure to plate (C). (Reprinted from Plant World 14: 286, 1911. Fig. 3. Diagram showing essentials of the Livingston paper cylinder at- mometer, the rest of the instrument as in figure 2. E, tin supply tube; D, ab- sorbent paper cylinder; L, cork supports holding lower edge of cylinder in place; S, tin seat, against which top of cylinder is appressed by glass cap (C). The latter is held in place by wire spring (V), cemented to C at K and flexed by fine wires {W), the latter attached to tube at F. (Reprinted from Plant World 14: 286, 1911.) 54 ATMOMETRY AND THE ATMOMETER 55 surface is here that of imbibed water, held in place by the cohe- sion of the surface films themselves (surface tension) and by their adhesion to the supporting paper fibers. Distilled water is sup- plied to the disk from the tube and air enters at the center of the disk, through a very small opening in the paper, as water is with- drawn. Waves and splashing, considerable removal of water by animals, and serious obstruction of the surface by the bodies of the latter, are here not encountered. Also, the entire instrument may be readily weighed or it may be read in volume units. The hydrostatic pressure upon the paper is rather irregularly variable, however; the entrance of air through the pin-hole is spasmodic, so that a considerable error is introduced into small readings. Also, the paper disk is apt to be deformed by strong wind, a feature comparable to that of ripples and waves on free water. The horizontally placed disk, with its central obstruction to free wind action, while furnishing an exposure to atmospheric conditions much more suitable to biological needs than that offered by the open pan, nevertheless leaves much to be desired. Especially noteworthy is the fact that the Piche instrument must always operate as a unit; it is practically impossible to place the evaporating portion at a distance from the graduated reservoir, an arrangement often desirable in physiological studies. Since all the water evaporated must pass longitudinally through the paper disk, from the central point of supply to the place of final vaporization, the size of the disk must be suited to the atmospheric evaporating power to be dealt with. In a region of low evaporation intensity the disk may be large, but must be smaller (to prevent the edges becoming dry at times) in an arid region.6 6 This phenomenon of dried disk edges has been described, in another con- nection, in the following: Livingston, B. E., and Brown, W. H., Relation of the daily march of transpiration to variations in the water content of foliage leaves. Bot. Gaz. 53: 309-330, 1912. See page 313. 56 BURTON EDWARD LIVINGSTON The Piche-Cantoni Atmometer (Fig. 2) This instrument7 is a modification of that of Piche, the reser- voir of water being here placed below and the paper disk above. Practically all the essential details of operation are the same as with the Piche, excepting that the spasmodic water move- ment (coincident with having the reservoir above) is here avoided, and that the evaporating surface may be placed at a considerable distance from the reservoir, in more satisfactory relation to plant foliage, etc. Distilled water should be used.' The Pickering A tmometer In the Pickering instrument8 a rectangular piece of absorbent paper or cloth is held vertically by a suitable frame, and evapo- ration proceeds from both sides. Water is supplied by means of a tongue of the absorbent material reaching from the lower edge of the rectangle into a covered reservoir of distilled water below. The Paper Cylinder (Fig. 3) The atmometer with paper cylinder9 is a modification of the Piche-Cantoni form, with the paper disk replaced by a hollow cylinder of absorbent paper, closed at the upper end, where it is applied against the supply tube. Distilled water is employed. It has all the advantages of the Piche-Cantoni instrument and the additional one of exposing a cylindrical evaporating surface. Its main weakness as a cylindrical form lies in the fact that air leak- age sometimes occurs at the junction of supply tube and paper cylinder, but a better form of mounting should obviate this dif- ficulty. It is notable that the Livingston paper cylinders evap- orate little or not at all from the interior surface, while the three paper forms above mentioned allow water loss from both sur- faces. 7 Cantoni, G., Sulle condizioni di forma e di esposizione piu opportune per gli evaporimetri. Rend. R. 1st. Lomb. II. 12:941-946, 1879. See also the writer's article on paper atmometers cited above. 8 Pickering, S. U., and Bedford, Duke of, A new form of evaporimeter. Wo- burn Exp. Fruit Farm Report 1897: 168-174, 1897. 9 Livingston, B. E., Paper atmometers for studies in evaporation and plant transpiration. Plant World 14: 281-289, 1911. ATMOMETRY AND THE ATMOMETER 57 The Bellani Porous Plate (Fig. 4) This kind of evaporating surface,10 which appears never to have been taken seriously during nearly a century that has elapsed since Bellani described it, seems to possess a number of advantages over the free water surface. A horizontal porous clay disk closes the top of a vessel completely filled with dis- tilled water, so that the lower surface of the disk is in con- tact with the liquid while the upper surface is exposed to the air. A small-bored, horizontal, graduated glass tube, open at its distal end, projects laterally from the vessel, and as evaporation takes place the air-water meniscus in this tube progresses toward the vessel, the tube being thus more or less slowly emptied of water. A suitable reservoir and controlling cock allows the meniscus to be pushed back over the scale, by admitting more water into the vessel. This is the earliest form of atmometer with an imbibed solid evaporating surface and the water reser- voir at a lower level. The possibility of such an arrangement results from the fact that it requires considerable gas pressure to force a passage of gas through such a plate, of porous pottery when saturated with water. Thus, atmospheric pressure is without influence upon the water mass in the vessel, excepting upon the index meniscus. As water evaporates from the porous surface more is imbibed from below and air pressure drives the meniscus inward along the scale, keeping the vessel filled and the plate continuously in contact with the water. It is to be noted that the Piche-Cantoni paper disk and the Livingston paper cylinder employ this same principle, only in those cases evapora- tion takes place from the marginal part of the paper project- ing beyond the end of the supply tube. The Piche-Cantoni form is not unlike what we should have if we suppose Bellani's porous plate to extend laterally much beyond the vessel which it closes, at the same time supposing the diameter of this vessel to be decreased until it becomes a mere supply tube from the lower 10 Bellani, A., Descrizione di un nuovo atmidometro per servire di contin- uazione e fine alle reflessioni critiche intorno all' evaporazione. Gior. Fis. Chim. 3U: 166-177, 1820. Also reprinted; Pavia, 1820. c Fig. 5 (I St c V) R Fig. 4. Diagram showing the essentials of the Bellani plate atmometer. R, burette reservoir for water; D, porous clay plate; S, metal support for D, connected to burette by supply tube (E). Fig. 5. Diagram showing essentials of absorbing mounting of the porous cup atmometer. R, bottle reservoir for water; D, porous clay cup, with thick- ened rim (\ ised by Shive. 61 62 BURTON EDWARD LIVINGSTON tact with the inner surface of the cup wall. The lower end of the cup is closed with a rubber stopper bearing glass or other suitable tubing connection to the reservoir. This tube is also full of water. The reservoir may be any suitable container; it is frequently a small mouth glass bottle with cork stopper and with a file mark on the neck to serve as zero point. In operation, this reservoir is filled to the file mark, the instrument is allowed to operate for a time period, and the reservoir is again filled, account being taken of the amount of water required, which is of course the amount lost by evaporation during the period. Where small readings are to be taken, the tube is often connected to the lower end of a bu- rette which is filled from time to time, the decrease in the volume of water in the burette reservoir being read directly on the scale. In all cases the level of the water in the reservoir must be lower than the base of the porous surface. It is obvious that the porous clay evaporating surface may have any desired form or size and that there is no danger of the drying of a part of the surface through excessive evaporation in- tensity, as is the case with the saturated paper surfaces mentioned above. It is also clear that, unlike the paper surfaces, the porous clay surface is in close proximity to a considerable mass of water, but the magnitude of this mass, in relation to the form and extent of the surface, may be modified to suit the requirements of the study in hand. With the porous cup form of instru- ment the evaporating surface may readily be placed at a con- siderable distance from the water reservoir. The details of the operation of porous cups will receive atten- tion farther on, after some important points regarding porous surfaces in general have been considered. THE POROUS EVAPORATING SURFACE IN GENERAL Nature of the Porous Surface Besides paper and porous porcelain several other solid ma- terials have been employed for evaporating surfaces. Woven fabric has sometimes been used. Perhaps the most frequent mention of porous surfaces in atmometry, however, refers to one ATMOMETRY AND THE ATMOMETER 63 of moist soil. Pans filled with moist soil, firmed to a smooth surface, have long been used by students of agricultural water relations. Regarding these, however, we need here make but the following observations. Some difficulty is usually experienced in preventing the soil surface becoming drier as evaporation pro- ceeds, thus producing a profound change in the internal properties of the instrument. This trouble and some others are avoided by the employment of the Bellani arrangement of a horizontal, porous porcelain plate in contact with water below; porous por- celain is in many respects merely a layer of soil, so bound to- gether that it will retain its shape. Thus, the general features of evaporation from such a plate should be in rather close agreement with those of water loss from a smoothly firmed soil surface. Porous surfaces, whether of paper, porcelain or any other fixed material, all agree in presenting to the action of the air a water surface mechanically held in position (by surface ten- sion, adhesion and the mechanical rigidity of the material em- ployed) and hence, as has been mentioned, they are not thrown into waves by the wind, so that the danger of splashing which is always imminent with open vessels is completely obviated. In- struments employing such surfaces can be read in terms of either volume or weight and they can be readily arranged so as to give small readings and to expose the evaporating member at some distance from the reservoir. These are the main advantages of such forms of atmometers over those with a free water surface. Two Classes of Porous Surfaces As has been seen we may consider two different arrangements of porous surface instruments. In one arrangement the satu- rated solid is in contact with unimbibed water for only a small portion of its extent; such forms are the Piche-Cantoni paper disk, the stretched paper or cloth of Pickering and the paper cylinder of the present writer. In the other arrangement the porous solid is backed by a mass of unimbibed water; of this form are the Bellani porcelain plate and the Babinet cup. Lj! library]* 64 BURTON EDWARD LIVINGSTON It is clearly possible, to decrease the amount of unimbibed water thus in general contact with the porous plate, per unit of surface, and thus to bring the two groups into closer similarity. The amount of this unimbibed water backing the solid, support- ing material is a matter of considerable importance; for the tem- perature of the active surface, an important feature in deter- mining rate of water loss, must follow temperature changes in the surroundings less promptly {i.e., with greater lag) the greater is the mass of water present behind the evaporating films. It was for this very consideration that the paper cylinder and its mounting were devised; it appeared clear that the porous clay cup, with its relatively thick, imbibed walls and its propor- tionally large amount of free water, should be less sensitive to external changes than such a water-holding device as the paper cylinder. For example, the temperature lag of the paper surface should be induced only by the small water mass actually held in the paper by imbibition or capillarity. In this respect such a surface should more nearly approach the form of exposure offered by ordinary thin leaves of plants. The porous clay cup should act in this regard more as do very succulent leaves, joints of cactus, etc., since here is a relatively large amount of water with relatively smalt surface. This matter was made the subject of a special study, in which paper cylinders and porous cups were operated side by side, and simultaneously subjected to sudden and rather great changes in their surroundings, these changes being accomplished by moving the apparatus from one position to another, from sunshine to shade, from the open to a closed room, etc. From these tests it appeared that the lag exhibited by the cup is exceedingly slight, so slight as to be quite negligible unless readings are taken every minute or oftener. On this account it has not yet seemed neces- sary to develop the paper cylinder farther than has been done. Sooner or later this form of evaporating surface may assume importance, as problems become more refined. ATMOMETRY AND THE ATMOMETER 65 Alteration of Porous Evaporating Surfaces by Operation All evaporating surfaces are apt to alter more or less with the progress of evaooration and with changes in the surroundings. As has been said, the secondary wind effect is completely removed in the case of non-flexible porous clay surfaces, while the removal of water by animals is practically serious only with free water. The accumulation of dust, etc., upon the saturated solid is per- haps more serious in its effects than the same sort of accumu- lation upon open water. Dust settling upon a pan of water decreases the rate of water loss, but usually (in its primary effect, at any rate) increases that rate from a paper or porous clay atmometer. Practically to remove this trouble, however, in case of porous porcelain, requires only that the surface be thoroughly cleaned occasionally. The papers, not being readily cleaned, should be replaced by new ones from time to time. Besides the primary effect of the accumulation of dust upon saturated solid surfaces, a secondary and more serious one lies in the incrustation of the latter by soluble salts, which may be derived from dust. Such soluble salts, crystallizing out at points of most intense evaporation, sometimes decrease the rate of water loss and at other times appear to increase it. With paper, this trouble can be removed only by frequent replacement; with por- celain, cleansing of the exposed surface at short intervals usually obviates the difficulty. Passing pure water through the porous porcelain, in the direction of the usual movement of water, largely removes soluble material, beyond the limit of its adsorp- tion. It is absolutely essential, with all imbibed solids that only very good distilled water be employed, to avoid accumulation of salts as the water is evaporated. Impure water, especially with calcium salts, clogs the pores and eventually almost glazes the surface. This accumulation seems impossible of correction by frequent surface cleansing, as has been shown by actual tests. It can be removed, if not too. pronounced, by forcing water or acid through the porcelain. 66 BURTON EDWARD LIVINGSTON Whether a solid surface has altered with use is to be determined by standardization at frequent intervals, an operation, with which we shall have to deal in the detailed discussion of the porous cup, to be presented below. Evaporation at Low Temperatures It is occasionally remarked that the porous cup atmometeris inadequate for many purposes because it cannot be operated when the air temperature falls below the freezing-point of water. Short periods of such low temperatures, a few hours in length, produce an ice or frost coating over the cup ; longer periods destroy the instrument with the bursting of the cup through freezing of the contained water. For measurements of evaporation under such conditions of cold the only instrument so far employed at all is the open pan of water, which thus exposes a free surface of solid water, or ice. Measurements are usually made by weighing. In connection with this matter it is to be observed that the freezing of a free water surface is another modification of the instrument, somewhat similar to dust accumulation, wave for- mation, etc. Evaporation does not progress at the same rate from an ice surface as from an equal surface of liquid water, at the same temperature,15 so that when freezing occurs it is as though the instrument itself were profoundly altered. Thus there is no logical direct comparison to be instituted between readings made with the liquid surface and those made with ice. Difficult as the problem thus raised undoubtedly is, the im- portance of winter evaporation is so great that some rational method for its measurement should be devised. We cannot go further at the present time than to state that there is no method yet described, suitable for measuring evaporation during 15 Juhlin, J., Bestamning af Vattenangans Maximi-spanstighet ofver is mel- lan 0° och - 50°C. samt ofver flytande Vatten mellan + 20° och - 13°C. Bihang K. Svensk. Vet.-Akad. Handlingar 171: 1-72, 1891. Marvin, F., Report of vapor pressure measurements and normal barometer construction. Part I. Maximum pressures of aqueous vapor at low tempera- tures. Ann. Rept. Chief Signal Office, Washington, 1891 : 351-3S3, 1S92. ATMOMETRY AND THE ATMOMETER 67 periods of frost; porous cups burst and leave blanks in the record, open pans freeze and introduce misleading readings into the record, readings which are not directly comparable with those from the same instrument with liquid water. THE POROUS CUP ATMOMETER The Porous Cups The atmometer cups now generally used in ecology, agricul- ture and forestry are practically of the same form and size as those described by the writer in 1906. The only improvement has been to make the closed end more nearly hemispherical, less pointed, than was the case at first. This change was made in 1913. These cups are cylindrical, about 13 cm. long and 2.5 cm. in diameter, closed at one end and strengthened at the other by a thickened rim. The wall is from 3 to 4 mm. thick, with the exception of the rim, which is about twice as thick. They are white, with a smooth, porous and absorbent exterior surface. The cup is closed, in use, by a rubber stopper which bears the tubing connection to the reservoir. Since it is absolutely essential that the evaporating surface change as little as possible, it is unsafe, in handling, to allow contact of the hands with the porous surface. To avoid the necessity of this, the basal portion (at the open end) of each cup is made water proof; details of manufacture have so far made use of a glaze for this purpose impossible and ordinary orange shellac in alcohol has been mostly employed as coating. Melted sulphur, into which the previously heated cup is dipped, gives a more serviceable coating, in some respects, but its application is somewhat troublesome. Before the coating is put on each cup is numbered on its rim, so as to be easily identified in use. The dipping in shellac is repeated till a satisfactory covering is obtained. The original standard cup of 1907 was free of coating for a length of 6 cm. from the closed end. Some cups were still more highly coated, but it was found more advantageous to have a large evaporating surface (both because of reduced error in read- THE PLANT WORLD, VOL. 18, NO. 3, 1915 68 BURTON EDWARD LIVINGSTON ing and because the larger surfaces remain without serious al- teration for a much longer time) , and most of the cups used and distributed for the last five years have had uncoated portions 8 cm. long. Thus the evaporating cylinder has the last-named length, an outside diameter of about 2.5 cm. and a hemispherical closed end, the whole being continuous below with the non- porous remainder of the cup. Other sizes and shapes of cup have been described from time to time and some of these have been furnished to the market. Yapp's16 and Transeau's17 cups differ from the usual one in minor points, but neither of these has come into very general use. The present writer has been able to procure, especially, two other cups, which have been placed upon the market. One of these, the insoluble cup, is of about the same form as the regular one, somewhat smaller, and made of a much more resistant material. In future this will have the same size and form as the regular cup. It has a glazed base, making shellac unnecessary. The other cup mentioned is termed "thin-walled." It is a straight cyl- inder 14 cm. long, 1.8 cm. in diameter, closed above by a some- what flattened top and glazed at the base to a height of 2.5 cm. This was obtained largely for its very thin wall, about a milli- meter in thickness, which suits it to certain comparative studies which need not be discussed here. Both of these special cups are now obtainable in pure white, though earlier lots of the insoluble form were slightly yellowish in color. The two smaller forms were designed for special uses. The Standardized Cup The main feature which has given the porous cup atmometer its present importance as an instrument of research is that it can be standardized and that standardization may be repeated as often as is desired. The cups are standardized by operating them with pure water, along with a cup of previous standardiza- 10 Yapp, R. H., On stratification in the vegetation of a marsh and its relation to evaporation and temperature. Ann. Bot. 23: 275-319, 1909. 17 Transeau, E. N., A simple vaporimeter. Bot. Gaz. 49: 459-460, 1910. ATMOMETRY AND THE ATMOMETER 69 tion, upon a rotating table,18 either indoors or in the open — in the latter case, without rain. Where radio-atmometers (which receive attention below) are employed, sunshine must be ex- cluded, as well as any other form of strong radiant energy. To accelerate evaporation, and thus give larger readings for shorter time periods, an electric fan is frequently so placed as to pass a strong current of air across the rotating table. The results are the same, aside from the time required, whether the fan is em- ployed or not. The rotating table now in use in the Laboratory of Plant Physiology of the Johns Hopkins University is somewhat over 2 m. in diameter and rotates two or three times per minute. At the Desert Laboratory Mr. J. W. Shive constructed, in the summer of 1913, a rather similar but smaller table, about 130 cm. in diameter, built upon a single bicycle wheel in a manner somewhat similar to that adopted by Nichols.19 It makes no difference, as far as these matters have been studied, what size of table is employed or at what speed it rotates. Of course the purpose of the rotation is to give the various cups equal treatment; since it is practically impossible to main- tain exactly similar or even constant air conditions throughout a group of stationary cups, this is not attempted, but each in- dividual cup is made to march through the same series of condi- tions as does every other cup of the group. The principle of this procedure is related to that upon which is based the long familiar use of clinostats, to equalize one-sided influences, as these affect growing plants. The cups may be mounted, for operation upon the rotating table, in any convenient manner, usually on small-mouth bottles or upon burettes (see the following section on installation), but it is to be borne in mind that every cup should receive the same influence due to the trailing vapor blanket emanating from the next preceding one in the series. This means that all cups should be at the same elevation from the table and that they should be equally spaced in the same circle. 18 Livingston, loc. cit., 1912. 19 Nichols, G. N., A simple revolving table for standardizing porous cup at- mometers. Bot. Caz. 56: 148-152, 1913. 70 • BURTON EDWARD LIVINGSTON A group of cups, with one of previous standardization, are first operated without reading for a period of from 12 to 24 hours, to allow the water films in the walls to come into equilib- rium, after which they are operated on the rotating table until the water loss from each is sufficiently great (say from 20 to 50 cc.) to make errors of reading negligible. The corrected read- ing of the cup of previous standardization is divided by that of each cup to be standardized, thus giving what is termed the coefficient of correction in each case. The coefficients are at once seen to be numbers by which the readings of the respective cups are to be multiplied, in order to give the loss which would have been shown from a cup with coefficient of unity, operated under the same conditions and for the same time. By "corrected reading" of the previously standardized cup is here meant the product obtained by multiplying the actual reading by the co- efficient derived at the earlier test. The group is operated for a second period and the calculations are repeated, giving a second coefficient in each case. Where the two coefficients thus obtained agree, or show differences not greater than 0.03, the cups are regarded as satisfactorily stand- ardized. They are then removed from the table, dried and wrapped in paper, the cup number and the mean coefficient from the two tests being written upon the wrapper. Cups' which show larger fluctuations in the value of the coefficient are left on the table and operated, with the same or' other standard cups, till a coefficient is fixed upon, or until they prove themselves impos- sible of satisfactory standardization, in which case they are dis- carded. The basis of standardization is still the old 6 cm. form of cup, but only for historical reasons. The first standardizations, car- ried out at the Missouri Botanical Garden and at the Desert Laboratory, in 1907, amounted simply to comparing the readings, under similar conditions, from a large number of 6-cm. cups. It was found that about half of these agreed very closely among themselves and that their water loss for any test was about the average loss from the entire group, some seventy-five cups alto- gether. The largest number of cups with agreeing rates were ATMOMETRY AND THE ATMOMETER 71 designated standards, and their coefficients were arbitrarily placed at unity. Thus those which lost more water had coeffi- cients below 1.00 and those losing less had coefficients above 1.00. It was to individuals with coefficient of unity, as thus established, that the earlier 8-cm. cups were standardized, under the conditions of early summer in Tucson, Arizona, and the majority of this larger type gave coefficients of about 0.73. It is doubtful whether this coefficient would stand, as showing the relation of the 6-cm. to the 8-cm. cup, under all climatic condi- tions— since the two instruments are not strictly of the same form, but only similar in certain respects. However, the 6-cm. cups are no longer in general use and the application of the coefficients of the 8-cm. standards now used simply reduces their readings to terms of an hypothetical cup, whose loss, under the same surroundings, is taken as *££ of that from the average 8-cm. cup. For practical purposes, as far as experience has gone, it seems quite safe actually to standardize 8-cm. to 6-cm. cups, and vice versa, though the procedure is obviously objectionable on theoretical grounds and has not been latterly practiced by the writer. The above explanation shows why it is, as some users of these cups may have noticed, that 6-cm. cups (about half shellacked) have coefficients approaching 1.00 when new, while the co- efficients of 8-cm. cups, as now marketed, are in the neighbor- hood of 0.73. Actually, these latter values usually lie between 0.67 and 0.79. In general it may be said that if the reading of any 8-cm. cup be multiplied by its coefficient the result is the same as though a large group of similar 8-cm. cups were operated under the same conditions as those obtaining around the one in question and the mean loss of the group were multiplied by 0.73. In other words, the average 8-cm. cup is now arbitrarily taken as having a coefficient of 0.73 instead of 1.00. An important precaution in standardization arises from the fact that the porous clay surface is apt to alter with continued use. Such alterations become evident as change in the value of the coefficient, and may be due to dust accumulation, to salts 72 BURTON EDWARD LIVINGSTON from water not strictly pure, to salts from the porcelain itself, or to removal of the shellac coating, etc. To avoid the effects of this possible alteration of standard cups it has long been the practice to use a given cup as of known coefficient only once (for not longer than three days) , or during the process of standard- izing a single group of cups. The cup so used for the first group became a cup to be standardized and a member of the next group, the standard for the latter being a new cup, unused since its standardization at some previous time. Some of the cups whose coefficients from two periods of operation on the table agreed (coefficients are actually calculated only to the second place of decimals, for cups placed upon the market), were laid aside for future standards and a large stock of these was always on hand. To insure clearness in regard to the calculation of coefficients, the operation may here be stated algebraically. If R is the reading of the cup of known coefficient (the one used as stand- ard) and this coefficient is C, while the corresponding reading of any other instrument in the group is r, then the required coefficient of the latter instrument (K), for this period of opera- te 7? tion upon the rotating table, is deduced as follows : K = — . Whenever this cup is used its readings are to be multiplied by K, to make them comparable with the similar corrected readings of any other standardized cup. As has been already emphasized, it is theoretically possible to derive a coefficient of correction (for reducing the reading of one cup to what would have been the reading of another in the same time and place) only when the two cups compared have very nearly the same form, size, etc. As in other similar instances met with in physical science, the importance of this whole matter depends upon the magnitude of the differences involved. In the present instance it also depends upon the sort of study to be carried out. It is quite readily possible to derive a coefficient which will express the relation between the evapo- rating powers of any two cups as shown by their operation on the rotating table for, say, a single day. If the cups are not alike, ATMOMETRY AND THE ATMOMETER 73 however, hourly readings through the day may show that the value of the coefficient fluctuates from hour to hour, for all hours of the day are not alike in the atmospheric conditions which they present. The conditions presented by one hour may accel- erate water loss from one cup more than that from the other; those occurring in another hour may accelerate loss from the second more than from the first, etc. Similarly, the average coefficient derived from operation on another day may be dif- ferent from that first obtained. But if two days present the same march of hourly conditions, or if they are so related that the average effective hourly conditions for one are in agreement with the corresponding average for the other (although it may be that no hour of one day gives the same coefficient as the same or any other hour of the other day), then the coefficient derived on the two days should be the same. From this sort of consideration it emerges that, the more detailed the work undertaken, and the greater the range of external conditions dealt with, the more attention should be given to having the cups exactly alike. For usual purposes of work in the field, experience points to the conviction that the 6-cm. and 8-cm. cups are not sufficiently diverse to make it practically impossible to reduce the read- ings of the shorter form to terms of loss from the longer, and vice versa, it is clear that these two forms are of the same shape, but the porous portion of one is 2 cm. longer than that of the other. The effect of various climatic complexes in altering the relation between evaporation rates from these two forms of cups is, at any rate, only slight, and has not been definitely brought out in standardizations carried out by night and by day in the summer of southern Arizona and indoors in the Baltimore winter. It is therefore safe to conclude that the corrected readings of the 8-cm. cups are at least practically comparable with the cor- rected readings of the 6-cm. cups formerly widely used. In spite of the theoretical difficulty here encountered, it may be assumed that the earlier results, obtained with 6-cm. cups, are practically homogeneous and comparable with the later ones obtained with the longer form. Thus, all published measure- ments of the evaporating power of the air, in so far as these 74 BURTON EDWARD LIVINGSTON have been corrected to the Livingston standard, may be re- garded as comparable for all practical purposes, regardless as to whether 6-cm. or 8-cm. instruments were employed. Further study of the behavior of these instruments, and of other modifications as to form and size, will be necessary before we shall be able to state within what sort of limits of external conditions the relation between the evaporating powers of two different kinds of cup may be considered approximately constant. Where the greatest accuracy is derived it is advisable to employ cups whose coefficients are alike. This matter of cup size and shape has no reference, of course, to modifications of the cups, produced by dust, handling, impure water, etc., which are apt to occur with use. With these altera- tions we shall deal below, in considering the operation of the instrument. This is, however, the place to mention one feature of this general problem, which is involved in the standardiza- tion procedure. It has been stated that serious changes in the standard cup have been avoided by frequently replacing the standard with a new cup, unused since its standardization. It has also been stated that serious alterations in cup surface may usually be prevented by frequent cleansing. The question then arises, would it not be better to hold the same standard continuously and to cleanse it from time to time instead of replacing? This suggestion is perfectly feasible with the insoluble cup, which is permanently glazed at base, but is to be followed with caution in the case of the regular form. The latter has been thought to be soft enough so that repeated rubbing might alter the porcelain surface, and there is little doubt that such treatment would alter the shellac coating. Recently the new form of insoluble cup, quite like the regular cup in size and form, has been em- ployed as standard. With thorough cleaning between standard- ization series, a single one of these cups may be repeatedly used. {To be confirmed.) OBSERVATIONS IN THE COLORADO DESERT S. B. PARISH Scm Bernardino, California An historic highway leads from Fort Yuma, on the Colorado river, to Warner's Ranch, situated at an elevation of 3000 feet in the mountains of San Diego county, California. In the early days of the American occupation it was the great thorough- fare from the regions beyond that river to the primitive settle- ments of southern California. Not until this grassy valley was reached did the weary traveler feel that the perils of the desert were passed, and a comparatively easy way was open to San Diego or Los Angeles. Several of the botanists connected with the early government surveys passed over this route, and places along it find mention in their reports. Later the construction of rail- ways, and the building of another and better road, deprived the old one of its former importance, and at present it is little trav- elled. Early in April, 1914, the writer drove over a part of it, and the following notes, the last two excepted, relate to places situated upon it. SAN FELIPE Five miles beyond the Hot Springs in Warner Valley, as one travels desertwards, the summit which divides the desert from the seaward mountains is passed at an altitude of 3780 feet and San Felipe Valley is reached. San Felipe is 1600 feet lower than Warner's, and both of them drain through steep canyons to the Colorado desert and the lower part of Carrizo creek. They are, therefore, part of the catchment area of the Cahuilla basin, but their flora, especially that of the first named valley, belongs largely to that of the arid San Diego Mountains. Both valleys contain considerable areas of coarse grasses, and numerous herbs and shrubs which are common in the dry mon- 75 76 S. B. PARISH tane region. In addition there is much Arlemesia tridentala, which is not common. But in San Felipe desert conditions prevail, manifesting themselves in the presence of Larreas, Fou- quieras and Agaves. The species of the last named genus is A. deserti Wats, which extends in a broad belt from the base of San Jacinto mountain to the borders of Lower California, where it connects with A. Palmeri Wats. Trelease has proposed a second species, A. consociala,1 for a part of the plants of this belt, founding it on specimens collected at San Felipe, but the characters relied upon were not recognizable in the field. LA PUERTA DE SAN FELIPE At the lower end of San Felipe a narrow gorge affords a bare passage for vehicles through a rocky ridge. Formerly it bore the appropriate Spanish name which indicated that it was the portal of entrance to the valley, but now it is more prosai- cally known as "Box Canyon." On its rocky sides grow Juni- perus calif ornica and specimens of Opuntia echinocarpa, 0. chlorot- ica, Cereus Engelmanni, Echinocactus cylindraceus and Mamil- laria phellosperma. Other shrubs were Lycium Cooperi, Con- dalia Parryi and Prunus eriogyna. In narrow seams Arabis perennans and tufts of Cheilanthes Fendleri and Chamcesyce poly- carpa hirsuta found root. Desert conditions are unfavorable to the growth of lichens, and where these prevail lichens are seldom present, so that it was interesting to find a number of crustaceous species in abundance on the more sheltered rock surfaces.2 LA PUERTA VALLEY The pass opens upon a small valley, whose gentle slope is abundantly grown over with Agave, intermingled with Yucca Mohavensis, Larrea and other shrubs. On the nearer side for- bidding and arid mountains of low altitude divide it from Salton 1 Rept. Mo. Bot. Card, xxii, p. 53, 1912. 2 The following species were collected: Acarospora squamulosa (Schrad.) Th. Fr., A. xanlhophana (Nyl.) Fink, Buellia myriocarpa (Lam. & DC.) Mudd, Dermatocarpon hepalicum (Ach.) Th. Fr., Gyrophora grisea Borr. & Turn., Parmelia conspersa (Ehrh.) Ach. and its var. isidiala Neil. OBSERVATIONS IN THE COLORADO DESERT 77 Fig. 1 . La Puerta de San Felipo, between La Puerta and San Felipe Valleys. 78 S. B. PARISH Basin; opposite a steeper ascent flanks Pine Lake Mountain, on whose summit small conifers can be discerned. Climatic conditions are austere in this valley. The range of temperature is from 15° to 115°F., and the rainfall, which is very uncertain, from 3 to 6 inches per year, while the violence of the winds is manifested by the sand heaped in the lea of every obstacle. But with all this, vegetation is more abundant and varied than in the still more arid desert beyond. The Agaves do not extend to the center of the valley, which is nearly flat. Here stunted Larreas constitute the principal growth, subordinate shrubs being Lycium Andersonii var. Wrighlii, Hymenoclea salsola and Croton calif ornicus. They afford some shelter to a number of annual herbs: Abronia aurita, Dithyrea calif ornica, Coreopsis Bigelovii, Lupinus gracilis, Oenoth- era pallida, Narna demissum, Bceria gracilis, Pectocarya linearis, Salvia carduacea, and others past recognition. The only in- troduced plants noted were Erodium cicutarium and a little Bromus rubens, both much reduced in size, as were the native herbs. The soil in which the. above plants were growing is a washed sand, much of it coarse, but further down the valley it is finer and loamy, and evidently contains some alkali. Here the plant most in evidence was a low form of Atriplex canescens, which had been closely browsed by cattle. There were also a few small mesquites (Prosopis glandulosa), some growing free and others buried in low dunes. All were alike leafless, a testimony to the severity of the winter climate. In this soil herbs were almost wholly absent. The slope toward the higher mountain on the southwest side of the valley is exceedingly rough with rocks, both in place and in strown fragments, and is cut up by shallow ravines. The vegetation exhibits a manifest zonalization. To the Larreas of the valley floor succeeds a nearly unmixed belt of a shrubby Eriogonum, whose glaucous foliage gives it a slaty-blue aspect. As it was not yet in flower the species could not be determined. This was succeeded by a mixed chaparral, in which Condalia Parryi and Prunus eriogyna were markedly dominant. Next in OBSERVATIONS IN THE COLORADO DESERT 79 prominence was Rhus ovata, large and vigorous, and as subor- dinate shrubs Simmondsia californica, Stenotus linearifolia, Salvia apiana and Eriogonum fasciculatum. Opuntia basilaris var. ramosa and two spinose platopuntias in many places obstructed passage. Among the stones scattered over the surface grew Pellaea ornithopus, Cheilanthes Fendleri and a small Dudleya. Along the main drainage wash, now dry, but doubtless having some percolating underflow, were a few small cottonwoods (Popu- lus Fremonti var. Wislizeni) and sycamores (Platanus racemosus) , and thickets of Baccharis sarothroides. Only at this place has the writer found the sycamore on the desert side of the mountains, but a consideration of the plants growing on this slope will show that, with two exceptions, they all are to be found in greater or less abundance on the cismon- tane side. This is in marked contrast to the vegetation of the hill on the opposite side of the valley, which belongs to the exclu- sively desert flora. The two exceptions above referred to are Prunus eriogyna and Condalia Parryi* These two species are often companions, and are found in numerous places, at from 500 to 2000 feet altitude, along the flanks of the range bordering the desert, from White- water, at the eastern base of San Gorgonio mountain, at least to the Mexican bolder. The Prunus seldom exceeds 6 feet in height, and is always a shrub. As seen at this place most specimens contained much dead wood, and the general aspect suggested that their struggle for existence was difficult. Condalia, while often shrubby, is properly a tree, reaching a height of 15 feet usually with a single trunk. Both were loaded (April 1) with fruit more than half grown. Time did not permit the ascent of the mountain slope beyond 1000 feet above the valley floor, but to have continued it would doubtless have revealed instructive and interesting successions. VALLECITO The road which descends into the desert follows the course of Carrizo creek, a typical desert "wash," whose sand-filled channel carries water only as the ephemeral sequence of a torrential - erus), and Therophytes are as in Akron. 3. In Tucson the Hemicryptophytes have decreased under the percentage of the normal spectrum so that this region is 160 OVE PAULSEN not characterised by them as is Akron. Here, in Tucson, Thero- phytes are very prominent, and the Fanerophytes are rather numerous. 4. Salton Sink is like Tucson, the only difference being that Fanerophytes have increased at the cost of Hemicryptophytes being still under the percentage of the normal spectrum. Death Valley shows the same features. Summing up, we find three distinctly different types of plant- communities namely : Hemicryptophytic : The Colorado plains. Chamaephytic : The Utah desert. Therophytic : The Tucson, Salton and Death Valley deserts. The yearly precipitation of Akron, Tooele and Tucson is respectively 47, 40, and 27 cm.,1 of Salton hardly over 20 cm. So we find a coincidence of drier climate with development of other growth-forms: Hemicryptophytes give way to Chamae- phytes and these to Therophytes and partly Fanerophytes. In the old world we have at least partly a parallel transition: in Southern Russia Hemicryptophytes dominate (the govern- ment of Jekaterinoslaw has 55%), and in Transcaspia Thero- phytes preponderate (41%); as to Fanerophytes the percentage of the two regions is respectively 5 and 11%. Thus also here there is a parallelism. The interjacent Chamaephyte region has not been numerically demonstrated in the old world, yet we know that in the countries between Southern Russia and Trans- caspia proper waste regions are covered with a vegetation of Artemisias and similar plants. So we may be justified in believ- ing that the Chamaephyte region is there. Finally it should be emphasized that the material upon which my conclusions are based is not complete and that if perfect biological spectra could be made they would without doubt give a more vivid and detailed picture of the relations between plains and different deserts in America. Yet I hope that there are no fatal errors in the preceding remarks. 1 Quoted from Kearney, Briggs, Shantz, McLane and Piemeisel and from Briggs and Belz. DESERT VEGETATION OF AMERICA 161 LITERATURE USED Briggs, Lyman J. and Belz, J. O. : Dry farming in relation to rainfall and evapo- ration (U. S. Dept. of Agric, Bur. of PI. Ind. Bull. No. 188) Washing- ton, 1911. Coulter, John M. and Nelson, Aven: New manual of botany of the central Rocky Mountains. Now York, Cincinnati, Chicago, 1909. ( Iarrett, A. O. : Spring flora of the Wasatch region. Lancaster, Pa., 1912. Kearney, T. H., Briggs, L. J., Shaxtz, H. L., McLane, J. W. and Piemeisel, R. J. : Indicator significance of vegetation in Tooele Valley, Utah. (Journ. agric. research I No. 5) Washington, 1914. Parish, S. B.: A catalogue of plants collected in the Sal ton Sink. (Publ. 193 Carnegie Inst, of Washington) Washington, 1913. Paulsen, Ove: Studies on the vegetation of the Transcaspian lowlands (the second Danish Pamir exp. conducted by O. Olufsen) Copenhagen, 1912. Raunkiaer, C. : Types biologiques pour la geographie botanique (Bull. Ac. Roy. Sc. Danemark 1905) Copenhague. Raunkiaer, C. : Livsformernes Statistik som Grundlag for biologisk Plante- geografi (Botanisk Tidsskrift 29). Kobenhavn, 1908. Translated in Beih. Bot. Centralbl. 87. 1910. ("Statistik der Lebensformen als Grundlage fur die biologische Pflanzengeographie"). Raunkiaer, C: Formationsundersogelse og Formationsstatistik (Botanisk Tidsskrift 30). Kobenhavn, 1909. Abstracted in English in Bot. Centralblatt, Vol. 113, p. 662. Shantz, H. L. : Natural vegetation as an indicator of the capabilities of land for crop production in the great plains area. (U. S. Dept. of Agric, Bur. of PI. Industry, Bull. No. 201) Washington, 1911. Spalding, Volney M. : Distribution and movements of desert plants (Publ. 113 Carnegie Inst, of Washington) Washington, 1909. For the study of Raunkiaer's methods the following papers might be con- sulted: Smith, W. G. : Raunkiaer's Life-forms and statistical methods. (Journal of Ecology, 1), 1913. de Forest, H.: Recent ecological investigations. (Proceed. Soc. American Foresters), 1914. THE ANTIZYMOTIC ACTION OF A HARMFUL SOIL CONSTITUENT: SALICYLIC ALDEHYDE AND MANNITE J. J. SKINNER Bureau of Soils, Washington, D. C. In an investigation of the soils on the Mount Vernon estate, Virginia, several organic compounds were isolated and identified1 in a sample taken in the flower garden from among the box hedges. Two of the compounds isolated are salicylic aldehyde C6H4.OH.COH and mannite C6Hi406. The effect of these com- pounds on growth have been studied. The salicylic aldehyde has proven to be very harmful to plants, grown in nutrient solutions, in soils in pots and in the field.2 The subject of this paper is concerned with the effect of man- nite on growth and the circumstances under which it exists in soils. This sugar alcohol was found in the Mount Vernon soil in an amount of about 500 lbs. per acre. Mannite can readily be produced by certain soil fungi, yet it is remarkable that it can persist in soils for it is a very unstable compound, being an excellent medium for the development of bacteria. Its effect on growth was studied in the green-house and some indications of its physiological action obtained but no very definite results were secured, because of the fact that the mannite solutions with the fertilizer salts were good media for the development of bacteria. The tests were made by growing wheat seedlings in distilled water culture and in nutrient solutions. Ten plants were grow» in each bottle holding 250 cc. of solution. The seedlings were 1 Shorey, E. C, Some organic soil constituents. Bull. 88, Bureau of Soils, U. S. Dept. Agric. (1913). 2 Schreiner, 0. and Skinner, J. J., Harmful effects of aldehydes in soils, Bull. 108, U. S. Dept. Agric. (1914). 162 HARMFUL SOIL CONSTITUENTS 163 supported in a notched cork which fitted closely in the wide mouth bottle. The first experiment was made using mannite dissolved in pure distilled water, as a culture solution. The mannite was used in concentrations of 10 to 200 parts per mil- lion, and the plants were grown in the "solutions from January 12-25. Growth in some of the mannite concentrations was about equal to that in pure distilled water, some of the cultures produced larger growth and others made less growth than in distilled water. A large experiment was made using nutrient solutions com- posed of calcium acid phosphate, sodium nitrate, and potassium sulphate. These salts were used in solution singly, in combina- tion of two, and of three salts, in all possible proportions, varying in 10 % stages. In this set there were 66 solutions, which were used as a control and to a second set of 66 solutions similar in composition was added 100 p.p.m. of mannite. The composi- tion of each of the 66 solutions is given in the second, third and fourth column of table 1. Wheat plants grew in these solutions from February 14 to February 26. The solutions were changed every third day and replaced by fresh solutions of the same composition. These solutions were analyzed for nitrate after the plants had grown in them. They were also tested for ni- trites and ammonia, to determine if decomposition was going on. In table 1 are given the composition of the culture solu- tions together with the green weight produced in the solutions without mannite and with 100 p.p.m. of mannite. • The total weight produced in the 66 solutions without mannite was 151.2 grams against 142.4 grams for the cultures containing mannite. While the total growth was less in the mannite cul- tures than in the control solutions, a close examination of the table shows that in those solutions containing no phosphate, Kos. 56 to 66, the growth was larger in the mannite solution, with the exception of one, No. 56, than the control solutions. The mannite caused less growth in nearly all of the other cultures which contain phosphate in some amount. Among the 46 so- lutions containing phosphate only ten of the mannite solution produced larger growth than their checks. The roots of the 164 J. J. SKINNER TABLE 1 Effect of mannite on wheat in nutrient solutions composed of calcium phosphate. sodium nitrate and potassium sulphate CULTURE NO. COMPOSITION OF CULTURE SOLUTION GR. WT. WITH- OUT MANNITE GR. WT. WITH 100 P. P. 11. MANNITE CUL- TURE NO. COMPOSITION OP CULTURE SOLUTION ■ < . 0 K O O GR. WT. WITH 100 P. P. M. MANNITE P2C>6 NH3 K2O P206 NH3 K2O p. p. m. p. p. m. /;. p. ///. grams gram* p. p. m. p. p. m. p. p. m. grams grams 1 SO 0 0 1.10 0.97 34 24 40 16 3.06 2.60 2 72 0 s 1.30 1.30 35 24 48 8 2.18 2.43 3 72 8 0 1.31 1.30 36 24 56 0 1.85 1.74 4 64 0 16 1.40 1.36 37 16 0 64 1.45 1.30 5 64 8 8 2.02 1.80 38 16 8 56 2.68 2.03 6 64 16 0 1.27 1.32 39 16 16 48 2.61 2.58 7 56 0 24 1.41 1.43 40 16 24 40 3.45 2.26 8 56 8 16 2.44 1.74 41 16 32 32 3.02 2.56 9 56 16 8- 2.10 2.04 42 16 40 24 3.18 2.70 10 56 24 0 1.71 1.50 43 16 48 16 2.77 2.87 11 48 0 32 1.56 1.59 44 16 56 8 2.57 2.45 12 48 8 24 2.45 2.32 45 16 64 0 1.75 1.46 13 48 16 16 2.55 2.50 46 8 0 72 1.49 1.55 14 48 24 8 2.26 2.01 47 8 8 64 2.70 1.92 15 48 32 0 1.62 1.61 48 8 16 56 3.05 2.98 16 40 0 40 1.55 1.55 49 8 24 48 2.92 2.47 17 40 8 32 2.88 2.58 50 8 32 40 2.80 3.33 18 40 16 24 2.90 2.47 51 8 40 32 3.03 3.11 19 40 24 16 2.51 '.'.40 52 8 48 24 3.12 3.03 20 40 32 8 2.26 2.17 53 8 56 16 3.00 2.57 21 40 40 0 1.50 l.CO 54 8 64 8 2.57 2.46 22 32 0 48 1.58 1.39 55 8 72 0 1.72 1.61 23 32 8 40 3.29 1.81 56 0 0 80 1.30 1.22 24 32 16 32 2.60 2.63 57 0 8 72 2.08 2.29' 25 32 24 24 3.20 2.54 58 0 16 64 2.37 2.62 26 32 32 16 2.46 2.52 59 0 24 56 2.38 2.72 27 32 40 8 2.07 2.17 60 0 32 48 2.60 2.68 28 32 48 0 1.66 1.63 61 0 40 40 2.43 2.60 29 24 0 56 1.32 1.66 62 0 48 32 2.33 2.65 30 24 8- 48 2.88 2.58 63 0 56 24 2.30 2.33 31 24 16 40 3.29 2.63 64 0 64 16 2.28 2.32 32 24 24 32 2.89 2.00 65 0 72 8 2.00 2.05 33 24 32 24 3.23 3.07 66 0 80 0 1.58 1.80 HARMFUL SOIL CONSTITUENTS 165 plants in the no phosphate cultures containing mannite wefe healthy and clean and fully as good as the control cultures, while the root growth in the mannite solutions which contain phosphate, were unhealthy and short and made a poor growth. When the solutions had grown plants for three days they were replaced by new solutions and the old solutions analyzed. More nitrates had disappeared in the set of solutions containing man- nite than in the control set of solutions. In the mannite cul- tures nitrite and ammonia were detected in solutions Nos. 1 to 46. The amount of nitrite varied from 6 to 10 parts per mil- lion, and each culture gave a good test for ammonia. There was no nitrite or ammonia in the mannite solutions Nos. 56 to 66 which contained no phosphate. The set of nutrient solu- tions containing no mannite, and used as a control, contained no nitrites or ammonia, nor have they ever been observed in these control sets.3 These data show that the mannite in the nutrient solutions containing all three of the nutrient elements, underwent decom- position, there was a formation of nitrites and ammonia, and that consequently the decomposition caused poor plant growth. The solutions in which there was no phosphate was not a good medium for the development of bacteria, consequently there was no decomposition of the mannite. Mannite as such does not seem to be harmful to wheat seedlings, and when decomposi- tion does not take place the material would seem to be used by the plants and an increased growth results. In view of the fact that the Mount Vernon soil was found to contain both salicylic aldehyde and mannite, an experiment in nutrient solutions was planned and conducted in which both these substances were added to the culture solution. In this experiment the nutrient solution contained calcium acid phosphate, sodium nitrate and potassium sulphate in amounts of 16-32-32 p. p.m. of the fertilizer constituents P205.NH3 and K20. Mannite was added in amounts of 100 p. p.m. and the salicylic aldehyde added, varied in the different solutions, from 3 Schreiner, O. and Skinner, J. J., Nitrogenous soil constituents and their bearing on soil fertility. Bull. 87, Bureau of Soils, U. S. Dept. Agric. (1912). 166 J. J. SKINNER 1* to 100 parts per million. Duplicate sets of these cultures were prepared, in one set plants were grown and in the second set the bottles containing the solutions were allowed to stand. At the end of three days the solutions were analyzed for nitrates, nitrites and ammonia. This was done every three days, until the plants had grown twelve days. The results of the analysis after the plants had grown the first three days, and the final green weight of the plants grown in each solution are given in table 2. TABLE 2 Effect of salicylic aldehyde in preventing decomposition in man n i te solu lions 6 55 TREATMENT So m S ^ H < «32 ~o. COMPOSITION OF SOLUTIONS AFTER 3 DAYS GREEN « Without plants With growing plants WEIGHT OF PLANTS P o NO3 N02 NH3 NOs NO2 NHj 1 Nutrient sol + 100 p.m. mannite ii. p. m. 117 117 117 117 117 117 117 117 p. p. m. 83.4 82.0 50.0 100.0 115.0 115.0 118.0 118.0 p. p. ?;;. 20.0 23.0 40.0 26.6 2.5 None None None p. p. m. Trace Trace Trace Trace • None None None None p. p. m. 40.0 16.6 30.0 60.0 90.8 111.0 111.0 111.0 p. p. m. 22.2 22.2 20.0 14.2 6.6 3.5 None None p. p..m. Trace Trace Trace Trace Trace None None None grams 2.75 2 3 4 5 6 7 8 Nutrient sol + 100 Same + 1 p. p.m. sali- Same + 5 p. p.m. sali- cylic aldehyde Same + 10 p. p.m. sali- cylic aldehyde Same + 25 p. p.m. sali- cylic aldehyde Same + 50 p. p.m. sali- cylic aldehyde Same + 100 p. p.m. sali- cylic aldehyde 2.80 2.35 2.20 1.87 0.93 0.56 0.38 An examination of the tables shows that nitrites and ammonia formed in the duplicate mannite solutions Nos. 1 and 2 and in those solutions which contained mannite together with 1, 5 and 10 parts per million of salicylic aldehyde. In the solutions which had no plants 25 p.p.m. and more of salicylic aldehyde prevented any decomposition in the solution. In the solutions with plants it required as much as 50 p.p.m. of salicylic aide- HARMFUL SOIL CONSTITUENTS 167 hyde in the mannite solutions to prevent decomposition. Other sets of solutions similar to these were analyzed, and the results were substantiated. In every case 25 to 50 parts per million of salicylic aldehyde in nutrient solution with mannite prevented any bacterial action. The green weight of the plants grown in one set of the solutions is given. in the last column of the table. It is again seen here, that the salicylic aldehyde is harmful to growth of plants as well as to bacterial life. The existence of mannite in the Mount Vernon garden soil is probably made possible by the simultaneous presence of salicylic aldehyde. Without any antiseptic action of this kind, mannite, if formed, would immediately be destroyed by soil organisms and probably could not exist as such for any length of time. This garden soil has grown box hedges, roses, and other peren- nial garden plants for years and manure has been liberally ap- plied. The subsoil is of such a nature as to prevent the proper movement of air and moisture. An examination of the soil in the laboratory showed that the surface soil was acid and the sub-soil decidedly so. The growth of the garden plants had become poor, and they showed signs of going backward in cer- tain locations. As a result of the laboratory examination lime and phosphatic fertilizer were applied and provision made for better drainage so that moisture and air may better circulate, and better results have been secured. Data have been secured in this laboratory which show that the harmful effects of aldehyde on plants is partly overcome by lime- and by phosphates. When conditions in the soil are such as to change or destroy the harmful com- pound salicylic aldehyde, soil organisms and other natural proc- esses of the soil would prevent the formation or destroy im- mediately after formation such an unstable compound as mannite. BOOKS AND CURRENT LITERATURE A Montane Rain-Forest. — Graphic descriptions of characteristic plant formations are always welcome and stand out in pleasing con- trast to mere lists of species masquerading as ecological studies. Es- pecialfy are such descriptions of importance where the communities dealt with are truly virgin; indeed, the correct delineation of the fast vanishing primitive vegetation of the earth is the most urgent phyto- geographical work at the present time. Shreve, in his recent book, A Montane Rain-Forest,1 has supplied a notable contribution in this regard. But he has done more than this, for the scope of his work is well indicated by its supplementary title, A Contribution to the Physio- logical Plant Geography of Jamaica. The forest treated of is situated on the Blue Mountains of Jamaica at an altitude of 4500 feet to 7428 feet. The climate of this area has a yearly rainfall of 105 inches to 168 inches, 172.4 rainy days and an annual mean temperature of 60.8°F.; frost is virtually unknown. The forest itself is in part temperate in character both in its ecological and florist ic composition, and evidently resembles in no small degree the lowland rain-forest of New Zealand, though this latter, strange to say, appears to bear ecologically a more pronounced tropical stamp. This striking resemblance between a tropical and a temperate plant formation is emphasized by several of the fine photographs that add greatly to the value of the book. Plate 1, with its wealth of ferns and Plate 8 with the pendant moss draping the slender, straggling tree- trunks, recall exactly typical scenes in New Zealand rain-forest, not only of the warmer parts but even where the climate is of a semi- subantarctic character. After dealing with the physical features and climate of the area, the author gives a list of the characteristic species of the florula, citing 270, of which no fewer than 93 are pteridophyta. In New Zealand, at a generous estimate, no piece of forest would contain more than 212 species, of which about 65 would be ferns and lycopods. . Next comes 1 Shreve, Forrest, A Montane Rain-Forest: A Contribution to the Physio- logical Plant Geography of Jamaica. Carnegie Inst. Wash. Publ. 199. Pp. 110, pis. 29, figs. 18. 1911. 168 BOOKS AND CURRENT LITERATI! !. 169 a clear account of the physiognomy of the forest, its ecological char- acteristics and a classification of the vegetal ion according to distinctions in habitats, such differences arising from position with regard to sun and the prevailing wind, the highly dissected erosion topography and altitude. Work of this kind is considered by Warming as not difficult, and in comparison with some of the problems presented by plant ecology which seem almost impossible to solve this is true enough, but it is nevertheless far from an easy matter to paint an accurate word-picture of a complicated closed association or to properly appreci- ate and keep in their proper place the facts of observation when quite minor distinctions may be of crucial importance. Above all, any account of a plant formation loses half its value if it cannot be readily used for purposes of comparison with related formations in other regions. In this latter regard the author has succeeded in no small degree, so that it is quite easy for one acquainted with a Xew Zealand rain-forest to see wherein lie its resemblances to that of montane Jamaica or its differences therefrom. The vegetation of ravines and ridges presents in a most striking- manner the effects of erosion topography, that of the former being strongly hygrophilous and of the latter almost xerophilous. So, too, in certain New Zealand forests a ravine will contain hygrophilous rain-forest and the ridge subxerophilous Noihofagus Solanderi forest, this an altogether different formation. Epiphytes are a most important group in this Jamaican forest, every type being represented, but on the other hand lianes, so much in evi- dence in New Zealand, are not numerous. The epiphytes show a zonal distribution in harmony with the moisture conditions, so that the most hj'grophilous occupy positions near the ground, midway come those that can tolerate an occasional scarcity of water, while in the forest roof xerophytes flourish. These latter differ from those of a sim- ilar station in New Zealand in that there is only one large plant, Cara- guata sintenesii (Bromeliaceae), whereas in New Zealand this specie's is represented by the epharmonically similar Astelia Solandri (Liliaceae), while various spreading shrubs several feet in height are also present. Possibly the most remarkable fact about these epiphytes is the physio- logical capachy of certain Hymenophyllaceae to tide over considerable periods of drought, whereas others of apparently identical structure die rapidly in the absence of sufficient water. From the standpoint of general ecology, the concluding portion of the book is of especial moment, dealing as it dot's with the transpiration 170 BOOKS AND CURRENT LITERATURE of rain-forest plants based on actual experiment. For the purpose of this valuable research a number of plants were selected, including two of the commonest trees, a common shrub, a thick-leaved herb, two herbs of the forest floor and two extremely hygrophilous ferns. Without going into details here, the author found that the rates of relative transpiration of the rain-forest plants dealt with and those of certain xerophytes of the Arizona desert are of the same order of magnitude, i.e. the rates of transpiration in the two regions are pro- portional to the rates of evaporation that prevail in them. While the plants of the rain-forest are capable of losing much more water per unit area than are those of the desert when the two kinds of plants are exposed to identical conditions, yet as each set exists in its habitat, the desert plant loses far more water per unit area than does the forest plant. This, though in line with certain recent publications, is contrary to the accepted opinion which is based not on experiment but on a con- sideration of the reduced transpiring surface of desert plants. One is apt to look upon rain-forest as a purely hygrophilous formation in which xerophytes have no place. This the author rightly shows to be a false conception. "There is no type of vegetation," he declares, "in which may be found a wider diversity of life forms than exist side by side in a tropical montane rain-forest. Together with the structural diversities discoverable in the field or at the microscope, are diversities of physiological behavior, discoverable by observation or experiment, and sometimes correlated with the structural features. There are quite as high degrees of specialization to be found in the rain-forest as may be sought in the desert." Much more could be extracted with profit from Shreve's admirable book, the chief fault of which lies in its brevity. One would have welcomed, for instance, a special account of the growth forms ac- companied by statistics for comparative purposes. Ecological works, with few exceptions, seem to take it for granted that the reader is acquainted with the species cited, whereas he frequently knows but little regarding them, and even if assisted by afloramay get far astray — L. Cockayne, Wellington, New Zealand. Plant Breeding. — In 1895, Bailey incorporated some excerpts from the writings of Verlot, Carriere and Focke with three of his own lectures relating to the improvement of plants and published the material under the title Plant Breeding. The author's reputation as the leading American agricultural botanist together with his charming BOOKS AND CURRENT LITERATURE 171 literary style carried the volume through three editions and several reprints during the next ten years, although it did not have the intrinsic value of most of his other works. It was a compendium of opinions which were often unsupported by facts; nothing in it was very helpful, nothing very wrong. One laid it down with no distinct idea of having read anything positive relating to plant breeding. In 1906, with the appearance of a fourth edition, there was a decided change in form. The author had sublet various parts. This entailed a sacrifice of style and unity; but there was a gain in facts — an incli- nation toward practicability and usefulness probably due to the guiding hand of Webber. In the present edition,1 the valuable qualities of both types of the earlier imprints have been retained. There is unity of purpose through the efforts of one reviser, Dr. Gilbert; there is the old simplicity of style through the supervision of Dr. Bailej^. The book is now really an introduction to scientific plant breeding, and as such will doubtless be of very great interest to the many laymen who wish to become conver- sant with modern ideas of plant improvement. It can also be heartily recommended as a text book for classes in general plant breeding in agricultural colleges if used with discretion by a teacher with some first hand knowledge of the subject and if supplemented by other works. It is not of a sufficiently advanced character, however, to be used for serious instruction in genetics. The first few chapters deal with variation in much the same hazy way that characterized the earlier editions. While no doubt the beginning student may gain something from them it is to be regretted that some of the numerous recent discoveries relating to reproduction, development and variation are not given as a foundation upon which the remainder of the discussions could be placed. There follows a brief discussion of statistical methods in Chapter IV and a resume of DeVries' facts and philosophy regarding mutations in Chapter V. The brief treatment of biometry is good, though there are several typographical errors and a certain vagueness concerning the meaning of probable errors. The reviewer suggests that in future editions, the1 chapter be placed in an appendix. The mutation theory is treated wholly from the DeVriesian standpoint of 1903. Possibly the account would have had a somewhat greater value if a description of the more important modern researches on the subject had been incorporated. 1 Bailey, L. H., Plant Breeding. Fifth Edition, revised by A. W. Gilbert. Pp. 474, figs. 113. The Macmillan Company, New York, 1914 ($2.00). THE PLANT WORLD, VOL. 18, NO. 6, 1915 LI t 172 BOOKS AND CURRENT LITERATURE Chapter VI, on hybridization, includes many things. There are discussions of natural selection, limits of crossing, natural hybrids, artificial hybrids, effects of inbreeding and crossbreeding, and graft hybrids. As indicated, it is a dip here and a dip there into some of the most important questions of plant breeding, with hardly an adequate treatment of each phase. Heredity, in the next chapter of sixty pages, is dealt with more ably, though one may be skeptical as to the desira- bility of continuing to use the coefficient of correlation, a measure of somatic resemblance, as a test of heredity after the confusion it has led to through the efforts of the English biometrical school. Further- more, the reviewer feels that the beginning student may get an errone- ous idea of Mendelian inheritance, or rather of the meaning of the Mendelian notation, from the author's method of treating the subject. Presumably, the very literal interpretation of a plant as a unit char- acter mosaic is due to the need to compress a large amount of material into a small space, but it might work considerable harm. Perhaps the best chapter in the volume is that on How Domestic Varieties Originate (Chapter VIII). It contains much historical matter that would be difficult to obtain elsewhere. The remainder of the book is much like the fourth edition. It deals with the technique of crossing and "the forward movement in plant breeding" as illustrated by practical work in various parts of the world. There are five appendices, including a glossary, a list of plant breed- ing books, a bibliography brought up to date (from 1905, the year of the last citations in the fourth edition), and a series of laboratory exercises. The bibliography is especially valuable, though one notices that many important foreign publications are omitted. The defini- tions given in the glossary for such terms as allelomorph, dominant character, factor hypothesis, and segregation, will hardly be accepted by geneticists. — E. M. East. Phototropism (?) of Urediniospore Germ-Tubes. — A short paper by Fromme1 presents the newly-demonstrated fact that urediniospores of Puccinia rhamni, and their young germ-tubes, are sensitive to one- sided illumination. The large majority of these spores, when germi- nating with one-sided lighting, protrude the germ-tube from a spire on the shaded side. If a tube protrudes from the more strongly lighted 1 Frooime, F. D., Negative heliotropism of urediniospore germ-tubes. Amer. Jour. Bot. 2: 82-85. 1915. BOOKS AND CURRENT LITERATURE 173 portion of the spore wall it almost always bends very soon, so that its tip becomes directed away from the source of light. The process of germination is thus apparently related to differences in light intensity on the different sides of the spore, and the young tubes are, at least apparently, negatively phototropic. The evidence presented seems to the reviewer to indicate an orien- tation of growth activity with reference to different intensities of the impinging light received by different portions of the surface of the spore or filament; these reactions are not apparently related directly to the direction of the light propagation. This somewhat important distinc- tion is not considered by the author. The purpose of this note is to emphasize the question that at once arises to the reader, whether the reactions here described are to be con- sidered as related to light at all. May they not be due to asymmetrical heat or moisture conditions? Fromme's spores germinated on an imbibed substratum (gelatin) exposed in a moist chamber, and a small beam of diffuse daylight was allowed to fall upon the spores from one side and from somewhat above the level of the substratum. It is obvious that a light reaction may be involved in the behavior of the germinating spores, but it seems just as obvious that moisture and heat relations are here to be considered. The author does not take up this consideration at all, though he does remark: "That positive hydrotropism may' partially explain stomatal entrance [of such hyphae, as germination occurs on leaves] is suggested by the work of Balls and Fulton but it is doubtful that this can be a factor of primary importance." There appear to be about four logical possibilities here involved. (1) Light intensity may be the controlling asymmetrical condition and one-sided photochemical alterations within the cell may be the internal control of the reaction. This seems to be the interpretation adopted by the author. (2) The direction of the impinging light may be the important external condition; as has been remarked, this seems improbable from the data given, and it needs no more than mention here. (3) A temperature difference between the shaded side of the spore or filament and the illuminated side may bring about the ob- served orientation. Here we meet with several possibilities. (3a) The illuminated side receives more radiant energy and should therefore be warmer. (3b) The air of the moist chamber may be warmer on the illuminated side, so that that side of a cell may be warmed by conduction. (3c) Convection currents in the air about the cell, brought about by asymmetrical income of heat from the more distant surround- 174 BOOKS AND CURRENT LITERATURE ings, may render either the illuminated or the shaded side warmer than the other. Which side might be warmer cannot be foretold, under such conditions as are here considered, without detailed knowledge of these currents. (3d) Differences in the evaporation rate from shaded and lighted portions of the air-exposed surface may cause temperature differences in several ways; these possibilities need not be further analyzed. (4) Finally, differences in the moisture content of the cell- wall, on the illuminated and shaded sides, may produce the observed reactions as hydrotropic responses. The lighted side should be some- what drier than the other side, whatever may be its temperature con- dition. If one of two like water-imbibed surfaces receives radiant energy and the other does not, it is quite possible for the former to evaporate more water than the latter, even though the other conditions may make the former the cooler of the two. It may be added that differences in moisture content between the two sides of the cell need not be postulated as a result of greater evaporation from one side; the moisture content of all the portions of the cell may remain alike, but the movement of water through the cell (from absorbing to trans- spiring surface) may bring about chemical differences between two regions of the protoplasm. It seems highly probable to the reviewer that the author's inter- pretation is the correct one, but the experimental evidence seems to be no more in its favor than in favor of any one of several other possible interpretations, some of the most obvious of which have been mentioned in the incomplete logical analysis that has just been outlined. There is no doubt at all that these organisms do respond to one-sided illumi- nation by diffused daylight, under the other conditions of Fromme's experiments; whether they respond directly to the light influence has not been investigated. — B. E. Livingston. Trent Forest Survey. — Eighty years ago the Canadian govern- ment started work upon the Trent Canal, which was to provide a waterway connecting Lake Ontario and Georgian Bay, and to aid in opening up the immense pine forests of that part of Ontario. The numerous lakes and rivers of the region were to be utilized in the project. The work was carried on irregularly, abandoned and begun again many times, and even today is far from completion. In the meantime exploitation of the pineries outran the development of the canal. The forests were cut clean and burned overmany times, so that the canal itself was frequently damaged by the resulting floods. In BOOKS AND CURRENT LITERATURE 175 spite of the deterioration of the region, the great sum already expended ($10,000,000) would alone justify an attempt at conservation of what resources remain and improvement of present conditions. The Com- mission of Conservation of Canada therefore authorized the investi- gation by Dr. Howe and Mr. White.1 Dr. Howe reports upon the forest conditions of the region : that the forests types number four; (1) hardwood type (beech-maple); (2) mixed hardwood-conifer type; (3) conifer type (white pine, hemlock, or swamp conifer); (4) poplar-birch type (on burned over lands, and at present by far the most extensive). The relations of these forest types to soils and to each other are those that have been described for other portions of the transitional belt between Northeastern Conifer and Eastern Deciduous Forests. The recommendations for methods of conservation and recuper- ation are as follows: (1) abandonment of all attempts at agriculture, as the region is thoroughly unsuited to such use; (2) careful protection of the region from fire, by governmental ownership of the watersheds, which would result in the growth of a timber crop (hardwoods, espe- cially pulpwood — the pines are doomed) , and the prevention of destruc- tive floods; (3) encouragement of local industries such as the manu- facture of small woodenware, utilizing the canal for transportation, and the abundant water power which is awaiting development. Dr. Howe has been commissioned to make further investigations of the possibilities of future forest development. — William S. Cooper. 1Howe, C. D., and White, J. H., Trent Watershed Survey. Pp. 156, Com- mission of Conservation, Canada. The Bryant Press, Toronto, 1913. NOTES AND COMMENTS Dr. Eduard Riibel has recently called attention (Journal of Ecology, December 1914) to the confusion that has arisen in plant geography through the use of popular names for the designation of important plant communities. The words macchia, garigue, tomillares, and phrygana, for example, are shown to be used in different parts of south- ern Europe for vegetations that are closely similar, while such terms as heath and steppe are applied to very unlike plant communities. The action of the Brussels Congress in voting to retain these and other vernacular names in the technical terminology of plant geography has raised many voices in dissent. The plant geographers of the world are pre-eminently a body of men who can rise above any national bias in favor of the terms that have originated in their own particular language. There is no reason whatever for laying any weight on the matter of priority in seeking a rational and acceptable system of nomenclature for plant communities. We have perpetually before us the spectacle of taxonomy, devoutly sworn to the principle of priority, and thereby chained to the imperfect type specimens, the incomplete knowledge and the false judgment of a century or more ago. There is no valid reason why plant geographers should not arbitrarily create a system of naming for vegetational groups, — a system that would be international, logically complete, and authoritative through general agreement, without being inflexible or so sacrosanct that it could not be abolished whenever it was desirable to do so. Just such a scheme of nomenclature was proposed by Brockmann-Jerosch and Riibel in their Einteilung der Pflanzengesellschaften nach Okologisch-Physiog- nomischen Gesichtspunkten, of which an English edition is now in preparation. There is much to be said in favor of the use of such a system, and the matter deserves careful consideration at the hands of plant geographers, and the fullest possible discussion. If by the adoption of such a system it should become possible to eliminate all further discussions of nomenclatorial matters in plant geography and ecology, and if the energy that has gone into them heretofore could be liberated and directed to some of the fundamental problems in these lines of work, the occasion would be one for profound congratulation. 176 NOTES AND COMMENT 177 Dr. H. C. Cowles and Dr. J. G. Coulter have issued a small manual of the spring flora of the north central and northeastern states (Ameri- can Book Company). The book has been adapted to high school use by the omission of grasses and other difficult groups, and by the prefixing of a very simple analytical key. Trees, shrubs, and other plants of importance in ecological work have been included, and are described and illustrated in their spring condition. Mr. B. C. Wallis has made a study of the rainfall conditions of the southeastern states in relation to the production of the cotton crop (Scottish Geographical Magazine, February, 1915). Cotton is grown in localities which vary in annual rainfall from 54 inches at the east to 31 inches at the west, but the crop is timed in such a manner that the precipitation during the growth of the cotton plant varies only from 17 inches in Texas to 23 inches in Florida. The Monthly Weather Review for October 1914 contains a paper by Prof. W. J. Humphreys on frost protection, a paper by Prof. C. F. Marvin on the principles of air drainage, and several articles that describe the methods and results of extensive efforts that are made for the protection of orchards from frost in California, Ohio and other states. VEGETATION OF THE BRAZOS CANYON, NEW MEXICO' PAUL C. STANDLEY National Museum, Washington, D. C. During August and September, 1914, Mr. H. C. Bollman and the writer camped for four weeks along the Brazos River, near the mouth of Brazos Canyon, in Rio Arriba County, New Mexico, some thirty miles south of the Colorado line. A large collection of plants was secured, and a general study of the vegetation was made, some of the results of which are stated here. The Canyon is reached from the railroad at Chama, New Mexico, twenty-two miles distant on the Denver and Rio Grande Railroad. The narrow gauge line starting from Alamosa, Colorado, runs southwestward across the plains to Antonito, then turns westward and begins a gradual ascent of the southern spurs of the San Juan Mountains. The adjacent plains are covered chiefly with sagebrush, rabbit-brush (Chrysothamnus sp.), and blue grama (Bouteloua gracilis), no individuals of the former shrubs exceeding perhaps three feet in height. After a short distance, as the hills are reached, the ascent becomes steeper and the road very tortuous. The foothills show many evidences of comparatively recent volcanic activity; there are many isolated cones surrounded by gently sloping lava beds which end in abrupt cliffs. The first trees are seen here, pinyon (Pinus edulis) and cedar (Juniperus scopulorum) , but they are few and scattered. In one place there was noticed a large clump of aspens, which, by some strange anomaly of distribution, are two zones lower than they should be! Straggling pines (Pinus brachyptera) soon make their appearance, and as the tops of the lower hills are reached, the pinyon entirely disappears, to be re- placed by a thin growth of pine. 1 Published by permission of the Secretary of the Smithsonian Institution. 179 THE PLANT « (■HID, VOL. 18, NO. 7, 1915 180 PAUL C. STAND LEY As the railroad first detours into New Mexico it reaches the Toltec Gorge, one of the finest bits of scenery in the state, where the Rio de los Pinos has cut through the mountains a deep pass with precipitous sides, similar to the Brazos Canyon, but prob- ably not so deep and certainly not so long. As the train winds along its summit there is an excellent view of its northward wall, covered with a magnificent growth of Colorado blue spruce. The trees are the finest the writer has ever seen, each of large size, perfectly symmetrical, and with sufficient space to show itself to best advantage. The less steep hillsides above the gorge support a moderately heavy growth of Douglas spruce, white fir, and aspen. The railroad soon recrosses the Colorado boundary, and, gradually ascending, reaches Cumbres Pass, the highest point on the line, having an altitude of 10,100 feet. The country east of the pass is very beautiful, consisting of wide, rolling, grassy meadows, flanked by densely forested slopes. Brooks and small lakes or ponds abound in the valleys. One of the lakes near Cumbres is the southernmost station for Nymphaea polysepala. Leaving Cumbres the train descends a very steep grade along the valley of the Chama River and soon reaches the town of Chama, which has an elevation of 7800 feet. Several high peaks rise to the northward, but unfortunately they lie in Colo- rado, and the writer has not visited them, being always interested primarily in New Mexican plants. He botanized for ten days about this station in 1911, securing a large number of species that are known from nowhere else in the State. The vegetation in the vicinity of Chama is similar to that of the Brazos Canyon. The wagon road to the latter place follows the Chama Valley for perhaps twelve miles, then turns eastward to the canyon. The valley is broad with gently sloping sides, and toward Tierra Amarilla, the county seat, it is irrigated and apparently very productive. Much of the land is seeded to timothy, a crop that is rarely grown in the Southwest. The valley lies mostly in the lower part of the Transition Zone. It has been overgrazed by sheep with the result that much of the grass and other natural VEGETATION OF BRAZOS CANYON 1S1 vegetation is replaced by weeds, such as that omnipresent southwestern plant, Ximenesia exauriculata, which in spite of its abundance apparently has never received a common name. In many places the alluvial flats are carpeted with a dense brown mat of some Polygonum, probably P. litorale. This short valley is not to be taken as typical of grazing conditions in Rio Arriba County, for the low mountains in this part of New Mexico are probably' the best stock ranges in the state. The Rio Brazos is a tributary of the Chama River, flowing into it near Tierra Amarilla. From its mouth eastward for about nine miles it flows through an open valley between low hills, but farther up it traverses a high plateau, through which it has cut a sinuous canyon from two to three thousand feet deep, and often less than a hundred yards in width. The can- yon is bounded by perpendicular granitic cliffs, and ends abruptly at the southern escarpment of the plateau. For nearly a mile on the north side of the stream this escarpment is as abrupt as the walls of the -canyon, then it changes into steep forested hillsides. At its foot is a great talus slope, along whose base the Brazos runs. The opposite side of the valley is inclosed by steep slopes, which rise to a level plateau, this finally falling gradually toward the west to the Chama Valley. The Brazos itself is a typical Rocky Mountain stream, swift, clear, cold, dashing over polished boulders, deepening here and there into great green pools which are the favorite haunts of trout. As it comes out into the wider valley toward Tierra Amarilla, it slackens, of course, and becomes wider and shallow. In the region about the Brazos Canyon two life zones are represented, the Canadian and Transition, and on the highest summits there are faint traces of the Hudsonian. The Cana- dian Zone embraces the plateaus and all the higher slopes of the mountains, the "box" or the canyon proper, and the north- ward lower sides of the mountains, extending in narrow strips well down into the Transition along the streams, while the Transition Zone covers all the lower slopes, except the more abrupt northward ones, and spreads, in a modified form, down to the Chama River. Near Tierra Amarilla the Upper Sonoran 182 PAUL C. STAND LEY is said to appear, coming in from the south, but the writer did not visit that region. The two zones are well marked in most places, except along the rock slides and rarely on the slopes at middle elevations, where there is sometimes an intricate associ- ation of plants which makes it impossible to refer a certain area definitely to either zone. The Canadian and Transition zones are not as sharply separated in New Mexico as are the Transition and Upper Sonoran, or the Upper Sonoran and Lower Sonoran; but, on the other hand, they are much more clearly differentiated than the Canadian and Hudsonian. The two latter zones in New Mexico are distinguished only artificially, even on the highest peaks where there is a broad expanse ofthe Arctic-Alpine Zone. CANADIAN ZONE The vegetation of this area consists of heavy forest, frequently interrupted by open grassy meadows. The trees are Picea parry ana, Abies concolor, Pseudotsuga mucronata, Pinus flexilis, Negundo interior, and Populus aurea, the first three being most abundant. Picea parry aria forms almost pure stands at the higher elevations and scattered trees extend far down along the small valleys. It is conspicuous inside the canyon, especially on the faces of the cliffs, where many individuals manage to secure a foothold in small pockets or crevices. The white fir and Douglas spruce grow on the lower slopes and are often mixed with yellow pine. Pinus flexilis occurs only occasionally, and at the higher levels. The box-elder is rare, along the banks of the streams. Aspen is the most abundant tree in number of individuals, occurring everywhere as an undergrowth where the shade is not too dense, and forming nearly pure stands over large areas where the timber has been destroyed. Of the shrubs several are common: along the streams Alnus tenuifolia, Sorbus scopulina, Amelanchier sp., and Dasiphora fruticosa are most abundant; in the Picea forests on the plateau above the canyon one finds Distegia involucrata and Sambucus microbotrys, the latter with small clusters of bright red fruit; while among the aspens there is an abundance of Rubus arizoni- VEGETATION OF BRAZOS CANYON L83 cus, Vaccinium oreophilum, Atragene pseudoalpina, Odostemon repens, Pachistima myrsinites, Lepargyrea canadensis, and Junip- erus sibirica. The last is frequent on the rock slides and extent Is well down into the Transition. This zone is rich in herbaceous vegetation and many of the most interesting plants of the region occur here. In aspen groves and on slopes among the coniferous trees the following are characteristic: Pteridium aquilinum pubescens, Pyrola picta, P. secunda, and P. chlorantha, Erigeron superbus, Pedicularis grayi, Oreochrysum parryi, Anthopogon barbcllatus, Dasystephana Fig. 1. Along the Brazos. The trees are Douglas spruce, with a few aspens. parryi, Silene menziesii, Anticlea elegans, Artemisia franserioides, Peramium menziesii, Antennaria microphylla, Caloehortus gun- nisonii, and Thermopsis pinetorum. In crevices of the cliffs inside the canyon and on the rock heaps at their base the follow- ing are common: Senecio pagosanus and S. taraxacoides , Rhddiola polygama, Draba helleriana, Erigeron leiomeris, Oxyria digyna, Cerastium scopulorum, Scrophularia montana, Rubacer parvi- florus, Heuchera rubescens, Ionoxalis violacea, P seudocymopterus anisatus, Leptasea austromontana , Poteniilla concinna, Primula (ingustifolia, and Cryptogramma acrosticholdes. 184 PAUL C. STAND LEY On the summit of the plateau through which the canyon runs are many wide treeless expanses, thickly covered with grasses and other herbaceous vegetation. Here and there through the meadows are small ponds and sluggish streams bordered with sedges (Carex sp.). The ponds often contain Sparganium angustifolium, Callitriche palustris, and two species of Lemna. The meadow grasses are the tall-growing Festuca thurberi, Poa interior, Danthonia intermedia, Stipa lettermanii, Sitanion californicum, and Phleum alpinum. Dugaldea hoopesii, Pyrrocoma crocea, Veratrum tenuipelalum , and Campanula petio- lata are abundant and showy plants. It is along the small brooks tributary to the Brazos and having their source in springs at the foot of the escarpment of the plateau that herbaceous vegetation is rankest. Some of these streams fall down over rounded boulders; others have cut deep and narrow channels through the soil among the trees, often spreading out to form swamps. Characteristic of these hydrophilous plants are Aster canbyi and A. burkei, Aralia bi- crenata, Viola nephrophylla, Rumex occidentalis , Crunocallis chamissonis, Panicularia pauciflora, Calamagrostis canadensis., Actaea viridiflora, Aconitum bakeri, Rudbeckia laciniata, Cap- noides brandegei, Senecio chloranthus, Epilobium novomexicanum, Ligusticum porteri, Conioselinmn scopulorum, Alsi?ie baicalensis, Sagina saginoides, Sanicula marilandica, Heracleum lanatum, Cirsium pallidum, Castilleja sulphur escens, Humulus lupulus neomexicana, Geum oregonense, Streptopus amplexifolius, Cynthia viridis, Hydrophyllum fendleri, and Mimulus pubescens. The wild hop is very abundant on rocks along the brooks, and equally so is Aralia bicrenata, which gets to be four feet high or more. One of the most conspicuous plants is Athyrium cyclosorum, forming great clumps at the very edge of the water. Mosses and lichens are abundant in this zone, as to number of individuals if not of species. The rocks along the streams are usually carpeted with mosses. Lichens are not frequent on the trees, although a species of Usnea is conspicuous locally, hanging from the branches of the spruces; but rock lichens are very abundant, covering the faces of the cliffs and the loose rocks of the talus slopes. VEGETATION OF BRAZOS CANYON 185 Fig. 2. Face of the escarpment of the plateau through which Brazos Canyon runs. Aspen in the foreground; yellow pine, Douglas spruce, and white fir in the distance. 186 PAUL C. STAND LEY TRANSITION ZONE Extensive lumbering operations have been carried on about Tierra Amarilla and well up toward the Brazos Canyon, where- ever surface conditions are favorable. It is chiefly the timber of the Transition Zone that has been cut, for that of the Canadian Zone is usually on slopes or in canyons which are difficultly accessible. On the lower hills and in the valleys about Chama the general aspect of the vegetation has been much changed by man, and most of the large trees have been cut off. Apparently lumbering has been carried on in a rational fashion, and there are none of the burns or of the tracts covered with dead branches that spell desolation where the country has been "skinned," as it has in so many places in both the west and the east. The yellow pine is being gradually reestablished by nature and young trees are seen everywhere, while the white fir reproduces rapidly where conditions are at all favorable. The vegetation of the Transition Zone in this region may be divided into two areas, typical Transition and Transition in which there is a large Upper Sonoran element. The first in- cludes the mountain sides and the banks of the streams at their bases : and the second embraces the valley proper of the Chama River and the slopes of the low hills. The line between the two is rather sharply marked; for while both are, or have been, covered with yellow pine, the herbaceous vegetation is com- posed largely of different species, although many herbs and shrubs are common to both, just as many are common to the Transition and Upper Sonoran zones. In the life zone map of New Mexico published recently2 there is shown a broad belt of the Upper Sonoran extending along the Chama River from Tierra Amarilla to Chama. This is certainly incorrect, if one is to judge of the zones by the limits laid down by the author of the text which accompanies the map. The Transition, in northern New Mexico, is the zone of yellow pine, and all of the area under discussion is or was once covered by that tree, except along the banks of the streams. There is 2 Bailey, Vernon, Life zones and crop zones of New Mexico. N. Amer. Fauna No. 35. 1913. VEGETATION OF BRAZOS CANYON 187 too great a tendency among makers of life zone maps to show the lower zones extending up into the upper ones along the streams. In New Mexico this is true in a general way of the large streams. In the great valley of the Rio Grande, for instance, taking the valley as a whole and not merely the flood plain of the river, the Lower Sonoran vegetation extends far to the northward. Along small streams, like the Chama and Brazos, just the reverse is true in a region of low rainfall like New Mexico. Here, under the favorable conditions of mois- ture, as well as temperature (although this latter is not readily apparent but is easily accounted for) , the vegetation of the higher zones is carried far down into the lower ones and should be shown on a map as tongues extending down, not as recessions. This is probably not true in a humid region, but it certainly is the case in New Mexico. Typical Transition Zone The one tree here is the yellow pine (Pinus brachyptera) , except along the creeks, where the mountain cottonwood (Popu- lus angustifolia) replaces it. The stand of pine about the Brazos Canyon and Tierra Amarilla is nowhere heavy, but this is doubtless the result of lumbering, for, farther west, on the Jicarilla Apache Reservation, under similar conditions, the stand is equal to any in the State. The vegetation of this division of the Transition Zone is very uniform, except along the streams and on the rock slides, be- cause the conditions of moisture, soil, and exposure are every- where similar. On the rock slides few trees can find a foothold, but there are many shrubs, chiefly A melanchier sp.,Padus melano- carpa, Grossularia leptantha, and Sericotheca dumosa. A few scattered shrubs of Juniperus scopulorum were seen on the rocks, probably introduced by birds. Some of the herbaceous plants noticed as common are Pericome caudata, Coleosanthus grandiflorus, Eupatorium fendleri, Chrysopis villosa, and Cap- noides aureum, these mingling with others that are properly Canadian. The banks of the Brazos are lined with mountain cottonwoods, which extend up as far as the mouth of the canyon. 1SS PAUL C. STAND LEY Accompanying these trees are shrubs like the choke-cherry, service-berry, gooseberry (Grossularia leptantha), and willow (Salix bebbia?ia), and numerous hydrophilous herbs, such as Aster laevis, A.frondeus, and A. wootonii, Apocynum scopulorum, Epilobium novomexicanum, and Prunella vulgaris. Elsewhere, on the slopes having normal conditions of soil, moisture, and exposure, there is usually a heavy shrubby under- growth, composed chiefly of deciduous scrub-oaks. The thick- ets are often very dense, but there are many open places among Fig. 3. Yellow pine with undergrowth of scrub-oak. Young pines may be seen on the right. This is typical Transition vegetation. them and at higher altitudes they gradually disappear. Other accompanying shrubs are Padus melanocarpa, Amelanchier , Uva-ursi uva-ursi, Ceanoihus j'endleri, Symphoricarpos oreo- philus, Odostomon repens, Berberis fendleri, and Sericotheca dumosa. It was interesting to find Yucca angustifolia common in the Transition Zone, a few individuals growing in the shade even of firs. It had been believed hitherto that in New Mexico only one species of Yucca, Y. baileyi? reached such a high altitude. 3 Contr. U. S. Nat, Herb. 16: 114. 1913. VEGETATION OF BRAZOS CANYON 189 The herbaceous vegetation is varied, including numerous species, but the season was so far advanced that many of the earlier plants had withered. Prominent among those in flower or fruit in August and September were several species of Eri- geron, Machaer anther a bigelovii, Aster laevis and A. commutatus, Chrysopsis villosa, Orthocarpus luteus, Moldavica parviflora, Gymnolomia multiflora, Agoseris purpurea, Villariova dissecta, Achillea lanulosa, Gilia aggregata, Collomia linearis, Pentslemon torreyi, Gnaphalium strictum and G. sulphur escens, Andropogon furcatus, Yiciaamericana, Lathyrus'leucanthus, Anisolotus wrightii, Rhinanthus crista-galli, Gayophytum intermedium, Polygonum douglasii, Lithospermum multiflorum, Castilleja confusa, Solidago trinervata, Arenaria confusa, Xanthoxalis stricta, Arabis hirsuta, Pterospora andromedea, Galium boreale, Thalictrum fendleri, Epilobium adenocladum, Lappula occidentalis , Oxytropis deflexus, Urtica gracilis, Anemone cylindrica, Geranium richardsonii and G. atropurpureum , Mentha penardi, and Silene hallii. Despite the lateness of the season many plants of the wild strawberries, Fragaria bracteata and F. ovalis, were still in flower. The vegeta- tion of this zone in the Brazos region, as a whole, is very similar to that of the corresponding tracts in the Santa Fe and Las Vegas Mountains, most of the species being common to both areas. The greater part of them, too, are found in the moun- tains farther south in the State, such as the Sandia, White, and Mogollon ranges. Lower Division of the Transition Zone As stated before, in addition to many species typical of the Transition Zone, this area includes many plants common also, in the Upper Sonoran. It is confined, in this region, to the valley of the Brazos, from Tierra Amarilla to within about four and a half miles of the mouth of the canyon, or the point where the river leaves the hills and comes out into a broad, open valley, to the lower slopes of the hills, and to the broad open valley of the Chama. The pines here have mostly been cut away, only the stumps remaining to show their original distribution. On 190 PAUL C. STAND LEY the hillsides the scrub-oak gives place to sagebrush (Artemisia tridentata) and rabbit-brush (Chrysothamnus graveolens, C. vaseyi, and C. parryi), but these shrubs occur only sparsely and are nowhere so dense as one often finds them in typical Upper Sonoran areas. Some of the characteristic herbs are Amaran- thus powellii, A. pubescens, and A. blitoides, Pentstemon xylus, Chenopodium leptophyllum,Eriogonum cernuum and!?, racemosum, Gutierrezia tenuis, Aster crassulus, Stanleya glauca, Helianthus annuus, Hymenoxys floribunda, Grindelia pinnatijida, Sideran- thus gracilis, Bouteloua gracilis and B. prostrata, Agropyron smithii, Atriplex rosea, Boebera papposa, Madia glomerata, Anogra coronopifolia, Artemisia dracunculoides , Ratibida colum- naris, and Senecio multicapitatus. Nearly all of these are Upper Sonoran plants, but associated with them are fully as many others that are typical of the Transition Zone. Where the valley of the Brazos widens there are broad flats, sometimes on one and sometimes on both sides of the stream. When the winter snows are melting the water cuts new channels across this flood plain, where it is not protected by cultivation, depositing soil in some places and in others washing it away and leaving beds of rounded stones or gravel. This area is overgrown with mountain cottonwoods, which reproduce rapidly and often reach a large size. Cedars (Juniperus scopulorum) grow with them in places, usually in thick shade, where they seem out of place. Probably cedars were more abundant formerly in the valley and on the "hillsides, before they were cut for firewood. There are scattered shrubs of sagebrush and rabbit-brush here, as well as on the hills. The herbaceous plants of the flood plain are much like those of the hillsides, except that there is a greater proportion of typical Transition plants. Clematis ligusticifolia climbs over many of the cottonwoods. Large areas are covered with a thick growth of Antennaria microphylla and a white-flowered perennial lupine. Many species of grasses abound, but the number of individuals is smaller than on the hillsides. On gravel banks and in moist soil common plants are Argentina anserina, Halerpestes cymbalaria, Sideranthus gracilis, Aster VEGETATION OF BRAZOS CANYON 191 wootonii, Verbena bracteosa, Munroa squarrosa, Castilleja linariae- folia, Madia glomerata, Marilaunidium angustifolium, Stachys scopulorum, Lactuca pulchella, Rumex mexicanus, and Lathy rus decaphyllus. The vegetation of the Brazos Canyon region thus illustrates two of the most characteristic life zones of New Mexico, the Canadian and Transition, the second of which shows two well differentiated subdivisions. It is typical of many of the moun- tain areas of New Mexico, although the writer is not prepared to state that the same divisions of the Transition can be made everywhere. Although scenically the region is equalled by'few in the State, floristically it is surpassed in interest by many other areas, for in number of species the flora appears to be much inferior, for example, to that of the Santa Fe and Las Vegas ranges, and there is found none of that Mexican element which makes the White and Mogollon Mountains so interesting botanically. FURTHER OBSERVATIONS ON THE ORIGIN OF THE GALAPAGOS ISLANDS ALBAN STEWART University of Wisconsin, Madison, Wis. Probably the origin of insular faunas and floras will ever re- main a fascinating problem for students of geographical dis- tribution. I have read with much interest ScharfFs excellent book, Distribution and Origin of Life in America,1 and with especial interest that chapter that deals with the biological conditions on the Galapagos Islands. I wish to offer no criti- cism on this work as a whole, nor do I consider that I am in a position to do so, but I do feel that an entire year of residence upon these islands and my subsequent study of their flora, ex- tending over a period of several years, enables me to speak with some confidence about the conditions which occur there, and to express an opinion concerning the origin of the flora, and of the islands themselves. For one who is fairly well acquainted with the conditions upon these islands, I do not feel that ScharfT has treated the subject with entire justice. Rather it seems that he has brought forward the evidence which best supports his own views in re- gard to the origin of these islands, etc., and has overlooked much other evidence that might well have been presented in a work of so extensive a nature. It is hardly necessary to present in detail the different theories that have been advanced to explain the origin of these islands. It is sufficient to say that such authorities as Darwin, Wallace, Agassiz, etc. believed that they were oceanic, and that each island had arisen separately from the ocean. This theory was held for many years, and Baur2 was the first one to oppose it 1 The MacMillan Company, N. Y., 1912. 2 On the Origin of the Galapagos Islands. Am. Xat. xxv, pp. 217-229, 307- 326, 1891. 192 ORIGIN OF THE GALAPAGOS ISLANDS 193 seriously. His theory was, that the islands had all been joined together at some time in the past, and at a still earlier period they had been connected with the continent of North America, presumably in the region of Central America. Baur had not been upon the islands when he formulated his theory, but he visited them subsequently, apparently in part to obtain evi- dence to support his views. My own study of the flora of these islands3 led me to a somewhat different view from either of the above — viz., that they are truly oceanic in their origin, but that they have been connected together at some time in the past in such a way as to form one or more larger islands, which by subsidence has resulted in the present condition. From the study of the flora I found no evidence which would lead me to believe that a land connection with either of the American con- tinents had ever existed. In fact most of the evidence would lead to the opposite conclusion. As these views have been set forth in a former paper,4 it is unnecessary to repeat them here. I do not wish to go into the zoological side of the question to any extent as there are others who are better qualified to criticise this part of the work than myself. I will, however, dwell briefly on a few important matters. It would have been rather appropriate for Scharff to have offered some explanation as to why there is a fairly abundant reptilian fauna upon the islands and at the same time an entire absence of batrachians. It would also have been well for him to have explained why the mammalian fauna, other than that which is known to have been introduced by man, consists only of bats, mice, and rats, for it is not likely that these would have been the only mammals that would have wandered there if the islands had ever been a part of the continent. It is hardly likely that the conditions could have been so adverse on the islands, since their supposed separa- tion from the mainland, as to exterminate all but these few re- maining forms. The ability of the land tortoises to get to the islands seems to 3 A Botanical Survey of the Galapagos Islands. Proc.Cal. Acad. Sci., fourth .series, Vol. 1, pp. 7-288, 1911. 4 /.. c, ])]). 233-243. 194 ALBAN STEWART have been difficult for Scharff to explain, unless a former land connection with the continent be admitted. This has probably come about through an error that has crept into the literature concerning the ability of these tortoises to remain alive in water. Scharff quotes a statement from Gadow,5 in which it is stated that land tortoises are drowned after a few hours' immersion in water, a statement. that may be true enough for land tortoises in general but will not apply to the Galapagos Island tortoises as our own experience proved. While collecting at Iguana Cove, on the southwest side of Albemarle Island, it became neces- sary to load some tortoises into a small boat at some distance down the coast from where our vessel was anchored. The shore was unprotected at this place, and there was a strong swell running which broke heavily on the shore at times. The boat was capsized while loading one of the tortoises into it from the water, and before it could be gotten to a place of safety was caught by a heavy breaker and completely demolished on the rocks. The tortoises thus escaped in the water and it was thought that we had seen the last of them. We were very much surprised the following day, however, to find that the remains of the boat had been floated down in the vicinity of the vessel, and by keeping a sharp lookout we were able to pick up both of the lost tortoises during the day. They had been in the water twenty or more hours and did not seem to have suffered any particular damage, except that one of them had been slightly injured by being thrown against the rocks when the boat capsized. . That they are able to live in the water for a much longer period is shown by the statement of Admiral David Porter6 who spent some time in the vicinity of the Galapa- gos Islands during the early part of the last century. Porter mentions with regret the fact that the crews of some of the vessels, recently captured by him, had thrown their supply of tortoises overboard in preparing for action and states further: "a few days afterwards, at daylight in the morning, we were so. 5 Amphibia and Reptiles, p. 373. 6 Journal of a Cruise made to the Pacific Ocean in the 1 nited States Frigate Essex, p. 162. ORIGIN OF THE GALAPAGOS ISLANDS 195 fortunate as to find ourselves surrounded by about fifty of them, which were picked up and brought on board." He also says in this connection that these tortoises can be piled away in the hold of a ship for eighteen months without suffering any diminution in fatness or excellence. It can be seen from this that there is no reason for believing that these tortoises would not be able to remain afloat for weeks or even months without suffering greatly. They always float right-side-up in the water, and if they are inverted immediatehr right themselves as soon as they are released. The suggestion of Dr. Stearns7 that much animal life might have been transported on floating trees, etc., is criticised by Scharff, and the impression is given that the Humboldt is the only oceanic current that bathes the shores of these islands. This is probably true for the southern islands of the group, but not the northern, as they lie within the Panama current and the waters surrounding them are about ten degrees warmer than around the southern islands at the same season of the year, s a fact that is also mentioned by Baur.9 Pieces of bamboo and cocoanut husks are common constituents of the drift cast up on the shores of the Galapagos Islands. These could hardly be brought hence by the Humboldt current. Such a method of transport is thus possible, but whether or not mollusks, in- sects, etc., would be able to withstand so long a sea voyage I am unable to say. Presumably Dr. Stearns was sufficiently well acquainted with these to speak with confidence in regard to their tenacity of life. The question is asked10 why the agencies of accidental trans- port should have been so much more potent in the distant past than the}* are now. The vascular flora seems to answer this question by showing that these agencies might not have been more potent in the past, and that it is possible that many plants have been brought to the islands within comparatively recent 7 Mollusk-fauna of the Galapagos Islands, p. 366. 8 Stewart, I.e., pp.* 226-227. 9 Baur., I.e., p. 222. 10 Scharff, I.e., p. 301. THE PLANT WORLD, VOL. 18, NO. 7, 1915 196 ALB AN STEWART times, or at least since the different islands became separated from each other. There are upon these islands some two hun- dred and sixteen species, varieties, and forms of plants, or 35% of the flora, which are confined to a single island. Of these one hundred and one species are endemic, leaving one hundred and fifteen species, or about 18% of the flora with a wider distribu- tion on the mainland. It is likely that further collecting upon the islands will extend the range of some of these species, but a large number of them must be confined to a single island, as many are of such a size that they would hardly be overlooked by even the most casual collector. Sapindus Saponaria L. is a conspicuous example of this class. There is such a similarity of climatic conditions at like elevations on many of the islands, as well as a similarity of soil, that it is improbable that so many species would be confined to such restricted areas if they had been present upon the islands before their final separation from each other. Furthermore, each succeeding expedition to the islands brings back a considerable number of species not before known to occur there, which have a wider distribution on the main- land. This might indicate that there is a more or less con- stant introduction of plants by the various agencies of chance distribution. There are a number of erroneous ideas prevalent concerning the botanical conditions on these islands, among which is the supposed alpine flora. This idea has probably arisen through Wolfs'11 observations on Charles Island. This author states that the vegetation at an elevation of 900 feet on this island bears a striking resemblance to the vegetation in the Andes mountains at an elevation of 9000 feet, a statement that was seized upon by Baur12 to support his subsidence theory. If Wolf had made his observations at similar elevations on either the south side of Albemarle or Indefatigable Islands, or, at a somewhat higher elevation on James Island, he would have found the conditions entirely different from those he describes, and might have con- cluded that the general make-up of the vegetation was more like 11 Die Galapagos Inseln, pp. 257-260. 12 L. c, p. 309. ORIGIN OF THE GALAPAGOS ISLANDS 19< that of the moist costal region of Ecuador than the mountainous part. On the three islands just mentioned, there are lofty for- ests covered with lianes and epiphytes, while the ground be- neath is carpeted with ferns and mesophytic plants, conditions which are about as far from alpine as could be well imagined. The peculiar conditions on Charles Island seem to be due to the loose nature of the soil and the smaller amount of precipi- tation. The same species, Scalesia pedunculata, forms a very large per cent of the forest trees on Charles, Indefatigable, and James Islands; they are low and rather stunted on the first of these, but lofty on the last two. The highest mountains on the islands must have been 14,700 feet high, according to Baur,13 before the supposed land connection between the islands and the mainland was lost. Such mountains would evidently have sup- ported, quite an extensive alpine flora, some little of which should have persisted to the present time. I found but little evidence of anything of the kind in my collecting around the summits of the Galapagos mountains, the species which occur in such localities being usually of a more or less mesophytic type. They are in most instances, the same species which occur lower down, in the moist regions of the islands, but when they grow on the wind-swept areas around the summits, the3r are usually greatly reduced in size. There are no plants which have the rosette habit, large and brilliantly colored flowers, excessive pubescence, or other characters that one would expect to find in an alpine flora. If one confines his observations to the dryer islands, a desert flora will be found there but not an alpine flora. The conditions around these mountain tops are such that alpine plants would probably have persisted if the}' had ever been present there. The vegetation is very low in many places so that it is hardly possible that alpine plants would have been exterminated by shading. Furthermore, the temperature around the summits of the mountains is far from tropical. I spent a night at the top of the mountain northeast of Tagus Cove, Albemarle Island, at an elevation of 4000 feet, and I passed the most of the time huddled over a small camp-fire shivering. 13 L. c, p. 309. 198 ALBAN STEWART It was actually cold there, and this was in the month of March before the coolest part of the year had begun. Air temperatures below 70° F. are not at all uncommon at sea level. The forms of Euphorbia viminea, which Scharff14 discusses at some length, have little bearing on the subject of origin if we admit the possibility of a former union of the islands with each other but not with the mainland. If he had taken the trouble to examine the latest flora of these islands15 he would have found that two of the forms described for this species have already been collected upon more than one of the islands. I believe that this will eventually have but little to do with the subject anyhow because there is some question about the distinctness of some of the so-called Galapagos Island forms. In fact I will shortly show that they do not exist in one of the species in which varietal forms have been described. We are jlealing upon these islands with a variety of climatic conditions as well as different kinds of soil. It is often the case that a few hun- dred feet difference in elevation will show almost an entire change in the character of the vegetation, from extremely xerophytic to mesophytic types. A considerable number of species are not confined to any one of such zones, however, but may occur to a greater or less extent in all of them, with a corresponding change in habit and general appearance in each.16 Some of the species which occur near sea level as mere bushes, assume the size of forest trees in the moister interior regions of the islands. Such marked changes in stature have a corresponding effect upon the length of internodes, size of the leaves, etc. Formal differ- ences are of course very slight, and it is rather unsafe to establish them in woody species which may occur under a variety of con- ditions, unless we have a larger series of specimens upon which to base them than has thus far been collected from Galapagos Islands. My own work on the flora of these islands is dismissed by 14 L. c, pp. 314-335. 15 Stewart, I. c, p. 93. 16 See Stewart, I. c, p. 77 for changes brought about in the appearance of Rhynchosia minima (L.) DC. by the different climatic conditions at different elevations. ORIGIN OF THE GALAPAGOS ISLANDS 199 Scharff17 with the statement that I have produced no new data for or against a former land connection with the mainland. It is true that I did not discuss this phase of the subject at great length in my former paper on the Galapagos flora, because, after I had tabulated my results18 the evidence was so strongly against the theory of a continental origin that I considered an extended discussion superfluous. This table shows that of the eighty-one families. of vascular plants represented upon the is- lands, only thirteen contain ten or more species. Of these Filices, and Compositae stand at the top of the list with seventy- seven and sixty-nine species respectively. Such a condition as this could hardly be possible if the islands were the remains of an extension of the continent, because many of these families are represented by a much larger number of genera on the main- land at the present time. We might well ask the adherents of a continental origin, why this condition should be, or why so many families are represented by but a single genus or even species. Surely the mere fact of isolation would not account for it because approximately 60% of the species of plants on the islands at the present time have a wider distribution on the mainland. Such a large per cent of non-endemic species would hardly remain if the conditions in the past had been very adverse. It seems that this condition can hardly be accounted for unless an oceanic origin of the islands is admitted. My work on the botany of Cocos Island19 strongly bears out this view, as I have shown that the flora of this island differs greatly from that of the Galapagos. If we exclude those species which are known to have been introduced on both islands, there are but twenty- four common to the two, eleven of which are ferns. There are several more species of rather wide distribution common to the two, which might easily have been introduced with garden seeds, etc. In fact, Captain August Gissler, a resident of the Cocos Island for many years, told me that Fleurya aestuans Gaud, had appeared upon the island since he had been there, and 17 L. c, pp. 315-316. 18 Stewart, /. c, p. 235. 19 Notes on the Botany of Cocos Island. Proc. Cal. Acad. Sci., fourth series, Vol. 1, pp. 375-404, 1912. 200 ALBAN STEWART that he thought it had been introduced from Panama. I found it only in the cultivated region around Wafer Bay. It would seem that Cocos Island should give us the key to the whole situation. Baur evidently considered this to be the most likely part of the ocean in which to construct his land bridge, as he states20 that the 4000 m. line connecting the Galapagos with the central American coast, extends through Cocos Island. If such a land connection had ever existed it. is very likely that there would be a much greater similarity in the floras of the two islands than is the case, as the climatic conditions are not so dissimilar but that eleven species of ferns are common to both. A relationship, though remote, between the floras of the Galapagos and Hawaiian Islands, is implied by Scharff.-1 We unfortunately have no very recent complete flora of the Hawaiian Islands, but from what is known I find that there are approximate- ly twice as many of the Galapagos genera represented upon the Hawaiian Islands as there are Galapagos species. This is a relationship that is about as remote as it well could be, and if we exclude the single species of the Hawaiian genus Lipochaeta, which occurs on the Galapagos Islands, the relationship is prac- tically nil. Hillebrand, in his work on the Hawaiian flora extending over a period of years, found no reason to believe that the Hawaiian Islands were ever less isolated than they are now. The water between these islands and the American continent is uniformally 3000 fathoms deep according to Hille- brand. To try to establish a land connection between these islands and the Galapagos, either directly or indirectly, seems to be preposterous so far as the botanical evidence shows. My work on the Galapagos flora has led me to strongly be- lieve that the only way we can account for its origin is through the chance methods of distribution of seeds and spores over large bodies of water. If we must invoke the aid of geographical changes to account for all the anomalous biological conditions that we find, truly the Pacific Ocean would look like a spider- web if the ghosts of all the supposed land-bridges should suddenly rise up to confront us. 20 Baur. /. c, p. 221. 21 L. c, p. 317. BOOKS AND CURRENT LITERATURE Limiting Factors and Plant Growth. — A most interesting con- tribution to the subject of climatic conditions as related to plant growth, and one that has apparently escaped the notice of many students of this subject, is Smith's1 study of the giant bamboo (Dendrocalamus giganteus), carried out in Ceylon. Lock's2 previous studies in the same locality indicated that the growth of this plant is controlled by atmos- pheric humidity, while other workers had secured contradictory results, or ones indicating that temperature is the important control- ling condition. In the study here considered Smith presents compari- sons of the rates of growth of giant bamboo with both temperature and humidity conditions, and shows that the one or the other of these two conditions acted as the limiting factor, accordingly as one or the other was more variable during the particular time period in question. The veiy rapid growth rate of the plant here used, which exceeded two centimeters per hour in some instances, made it possible to compare the growth rates with the climatic conditions for relatively short time periods. The rapid growth is supported by a large reserve food supply and thus may not be compared directly with growth under conditions where there is no such supply. The records of air temperature were obtained from shaded mercurial thermometers and those of relative humidity from readings of wet and dry bulb thermometers. Relative humidity does not, of course, fully express the moisture conditions of the environment as they may affect plant growth, but it may have been the most important factor influenc- ing the moisture conditions in this case. The bamboos grew in moist soil along the borders of "tanks" or reservoirs, where the water supply was abundant. Large well-established clumps were selected for study at each of three stations, in different climatic zones: at Anuradhapura, in the hot, dry lowlands, 300 feet above sealevel; at Peradeniya, in the warm, moist region, 1500 feet above sealevel; and at Hakgala, in the cool, moist mountain region, 5600 feet above the sea. At each of these stations observations were made upon the growth of young 1 Smith, A. M., On the application of the theory of limiting factors to measure- ments and observations of growth in Ceylon. Ann. Roy. Rot. ( rard. Peradeniya 3: 303-375. 1906. 2 Lock, R. H., On the growth of the giant bamboos. Ann. Roy. Hot. Card. Peradeniya 2 (Pt. II). 1904. 201 202 BOOKS AND CURRENT LITERATURE culms at two-hour intervals during several days, and the growth rates were compared with the data of relative humidity and air temperature for corresponding periods. At Hakgala the humidity varied during the day, but was very close to the saturation point throughout the night. During the day the growth rates of the bamboo culms varied directly with changes in rela- tive humidity, which ranged from 88 to 100 per cent, in spite of changes in temperature, which ranged from 10°-21°C. The rates of growth at night were usually much higher than the day rates. They gradu- ally decreased from sunset until sunrise, thus varying directly with the rather small changes in temperature from 17° to 13°C. Tempera- ture also seemed to be effective in producing very rapid growth during daylight periods of rain; since humidity was high at such times and the higher diurnal temperatures produced more rapid growth than occurred at night even with the same humidity. Thus, with nearly constant humidity, during cloudy days and at night, temperature changes appear to have been of primary importance in controlling growth. Within the same temperature range, but with larger variations in humidity, the day rate was apparently mainly influenced by vari- ations in humidity. Thus there were two limiting factors operating at Hakgala, temperature and humidity. ' At the other two stations the relations of growth rates to temper- ature and humidity conditions were similar to those just described, but the response of the plant to temperature changes were here less marked than was the response to humidity alterations; changes in tem- perature were here comparatively slight (from 22° to 27°C), but the humidity varied markedly and frequently. The author emphasizes the point that relative humidity can be the limiting factor only in an indirect way, the real limiting condition being probably the transpiration rate, which is influenced by direct solar radiation, wind movement and the degree of stomatal closure, as well as by humidity. At all three stations the growth rates increased very markedly at sunset and decreased as promptly at sunrise, but the changes in humidity and temperature at these times were not considered to be rapid enough to account fully for these sudden alterations in growth. Smith attributes these alterations rather to the closure of the stomata at sunset and their reopening at sunrise and to the changes thus brought about in the rate of transpiration than to any direct influence of light upon growth. Somewhat similar results were also obtained with a number of other plants.— F. T. McLean. BOOKS AND CURRENT LITERATURE 203 Inorganic Plant Poisons and Stimulants. — Under the editor- ship of T. B. Wood, professor of agriculture in the University of Cam- bridge, and of E. J. Russell, director of the Rothamsted Experimental Station, the series of Cambridge Monographs is making its appearance. Of these a thin volume of about one hundred pages by Miss Brenchley,1 of the Rothamsted Station, presents the literature and our knowledge of the influence of copper, zinc, arsenic, boron, and magnanese com- pounds upon plants and the soils in which they are cultivated. Pointing out that different concentrations of the same compound may act as stimulants to growth, or to other activities, or as repressants or poisons, Miss Brenchley briefly discusses the bases of the difference in behavior, without however leading to any definite conclusion upon the foundation of present knowledge. In regard to this and the other topics discussed, perhaps the most valuable contribution of the author is the evidence that, at present we know very little about the subject. At the same time it should be gratefully acknowledged that Miss Brench- ley has saved the average plant physiologist much time and trouble by bringing together the major part of the literature and briefly dis- cussing the principal contributions. Doubtless the specialist on plant poisons will miss the reference to certain papers, but to him such a book is less useful. Two of the elements in this list of five are particularly interesting to Americans because of their general use in sprays, fungicides and insecticides, namely, copper and arsenic. The other three, zinc, boron, and manganese have a much more limited interest, although Miss Brenchley concludes that manganese may, under certain conditions, be a valuable stimulant to growth and crop production. Copper and arsenic appear not to act as true stimulants, the beneficial results of their use depending entirely upon the toxic action of dilute solutions of their compounds upon the parasites attacking their less readily permeable hosts. The effect of copper on germination, for instance, is nil or repressant; but the net result of its use may be advantageous, because the copper compound may have killed fungus and bacterial spores adherant to the seed coats. This book confirms the impression, increasingly strong in the re- viewer's mind, that the greatest need of the biological sciences today — of agriculture, horticulture, botany, zoology, and all their divisions — is the application to the study of living organisms of those qualities of mind, as well as the tools, which the chemist and physicist must possess or cease to be chemist and physicist in any proper sense, namely quantitative, not merely qualitative, accuracy. Biology has lagged behind, is still too largely a descriptive science, is still mistaking what is purely aviation for scientific hypothesis. — George J. Peirce. 1 Brenchley, Winifred E., Inorganic plant poisons and stimulants. Pp. 110, figs. 19. Cambridge University Press, 1914 ($1.25). A NOTES AND COMMENT A writer in the April issue of Torreya criticizes severely the manner in which papers are presented at the scientific meetings, giving a de- tailed diagnosis of the defects which he discovered in attendance at the Philadelphia session of the American Association. The titles are uninforming, technique and principles are intermixed, charts and dia- grams are not allowed to speak for themselves, and the accompanying remarks are unduly prolix as well as tardy in arriving at the main point. Such is the verdict on what most of us have saved up as our supreme effort of the year! We may feel that the verdict is a little severe but we can at least recall other members of our section who have com- mitted some or all of these defects. Our critic states that "contrib- utors too often insisted upon laying before us their day-book instead of the ledger; indeed, the balance sheet itself would often be preferable." By all means! Let us have the balance sheet! There is no objection to having the most important items of the balance sheet in red ink. It would be highly undesirable to make papers too brief and con- densed, at least so long as our Sections and Societies refuse to print preliminary abstracts of the papers. It is a bad habit which causes many participants in scientific meetings to be highly detailed at the outset, while there is still plenty of time, and then to be so hurried after the secretary has whispered to them, that they are unable to present adequately the chief conclusions of their work. Whether we are listen- ing to a paper or reading it in a journal the first thing that we want is a condensed statement of the problem attacked and the main results secured. It is a universal custom to summarize results at the close of a contribution. It is an equally universal custom to turn to the last pages of a published paper and read the summary before we begin to read the paper. It would be an extremely sensible proceeding to place the summary of conclusions at the beginning of a printed paper and to present the main conclusions of an oral paper during the first two minutes of its delivery. Announcement has been made of plans for the celebration of the twentieth anniversary of the establishment of the New York Botanical Garden. The exercises will be held during the week of September 6, 1915, and will comprise addresses, the reading of scientific papers, opportunities for inspection of the grounds and collections, as well as a visit to the Brooklyn Botanic Garden, and two field excursions. 204 THE DUNES OF LAKE MICHIGAN THEO. J. STOMPS Amsterdam, Holland It was a great delight to me to be invited by Professor Cowles to join the International Phytogeographic Excursion in the United States during the months of August and September, 1913. In fact I feel inclined to acknowledge that the months I have spent in America, belong among the most happy ones which I have known in all my life. Friendship is the one thing we all need, whether scientific men or not. Friendship has fallen to our share from all sides during the excursion all along. A most hearty companionship always existed among the members of our party, leading to a better understanding of each other's work and to a higher appreciation of opinions which were not our own. And wherever we came, we were received in a most cor- dial way not only by fellow scientists but also by others who, though knowing little about our work, still showed a great inter- est in it; a continuous display of American hospitality. The excursion programme was arranged in a splendid way, allowing us to get an insight into the vegetation of a whole continent. One must get a feeling of perfect happiness by living, traveling, working for several weeks under such favorable circumstances. I wish to render thanks to my American friends for this most memorable summer and especially to Professor Cowles, our emi- nent leader. I can assure him, that I learned much in many respects, more than I ever could have expected. I think we all got the impression, that our excursion was ar- ranged in a progressive way. Gradually we passed to more interesting plant-formations and to more beautiful scenery. In order to fulfil my promise to Professor Cowles, to write a treatise on some point that has struck me most in the vegetation, I would therefore have to deal with my impressions of some trip or other 205 THE PLANT WORLD, VOL. IS, NO. 8, 1915 206 THEO. J. STOMPS made towards the end of our excursion. I shall not do this, however. Perhaps I can give proof of my indebtedness to Pro- fessor Cowles best by showing that the beginning of his excur- sion was already very interesting to me. Is it not a matter of course that one whose native country could not exist if it were not protected by dunes against the sea, felt especially attracted by the study we made of the dunes of Lake Michigan? Let me therefore say a few words about this region, which we visited immediately after our excursion had started in Chicago the first of August, and compare it with our Dutch dunes. Of course I cannot enter into particulars and must confine myself to the de- scription of some general impressions. The water of Lake Michigan is fresh and that of the North Sea is salt. This stands to reason, but is important to him who studies the flora of the adjacent territories, because it is con- nected with differences in the chemical characters of the soil. These differences are of two kinds. They bear upon the amount of common salt in the soil on the one hand and on the amount of lime on the other. Of course the shore of Lake Michigan does not contain any salt at all. On our Dutch coast on the contrary salt in the soil plays a considerable role in the development of the flora, not so much in the dunes proper, but mainly on the middle and the upper beach. Middle beach I call, in agreement with Professor Cowles, that zone of the beach that lies between the high-water- marks of summer-storms and winter-storms and is colonized only by some annual herbs, because the possibility of survival through the winter period is excluded. The upper beach, not even flooded by the high storms in winter, presents the same species and in addition to these many others, especially perennial herbs with creeping rhizomes. As the middle beach is sometimes washed by sea-water and the saline water in the soil lies at a slight distance below the surface, as the air at the sea-side is usually very rich in salt-particles and during low-tide often large quantities of much salt-containing sand are blown landward from the lower beach, it is clear that our strand at least must bear a halophytic vegetation. It is generally known, that this THE DUNES OF LAKE MICHIGAN 207 is really so. All the annual species that grow on the middle beach, as for instance Cakile maritima, Salsola kali, A triplex Uttoralis and Atriplex laciniata, are more or less succulent and belong to the halophytic type of growth. The same holds good for the species of the upper beach: here we find the same forms that occur on the middle beach and besides these many other halophytes, such as the succulent Honkenya peploides and Con- volvulus soldanella and the glaucous wax-coated A gropyrum jun- ceum — all three in possession of subterranean runners — and the also succulent Euphorbia Paralias, a form that assimilates even in winter — as do many plants in our dunes — and multiplies by adventitious shoots from the roots. In short, we may say that the vegetation of our shore is distinctly halophytic. Even in our coastal dunes species with distinct halophytic characters are found, e.g., the wax-covered Eryngium maritimum and Glau- cium lutum, forms that dislike to grow away from the sea and seem to need, if not salt in the soil, then at least salt in the air. If we now compare with these conditions the situation on the shore of Lake Michigan, it must strike us at once, that there the aspect of the beach-flora is not halophytic. Such characteristic beach-plants as Euphorbia polygonifolia, Artemisia caudata and A. canadensis, Cirsium Pitcheri, Xanthium canadense, which we collected near Miller and Dune Park, Indiana, or Strophostyles helvola and Petalostemum purpureum, which we saw at Lake Bluff, Illinois, can not be said to have a halophytic appearance, nor can Potentilla Anserina, which Fuller mentions as charac- teristic of the beach in the list of dune-plants in his The vegeta- tion of the Chicago Region, but which I cannot remember, to have found. So we have learned to know a first interesting point of difference between the dunes of Lake Michigan and those in Holland. This point becomes still more interesting, when we hear that after all some true halophytic species are to be found on the shore of the fresh water Lake of Michigan. The some- what fleshy annual Euphorbia polygonifolia is properly speaking an example of this kind. I have found this same species near Wood's Hole, Massachusetts, on the beach of the Atlantic. Some other instances can easily be given. On the eastern shore 208 THEO. J. STOMPS of Lake Michigan the chief character-species of the middle beach, but thriving also on the upper beach or on windward slopes of active dunes, is the annual succulent Cakile edentula. This species also, a perfect imitation of our European Cakile maritima, I have collected near Wood's Hole, Massachusetts, and towards the end of our journey we have met with it again on the Pacific Shore at Carmel, California. Another halophyte, that we saw on the beach and in the dunes near Miller and Dune Park, Indiana, is the succulent annual Corispermum hys- sopifolium, in Europe often locally a characteristic plant of the dune-flora of the coast. In Holland too it has been found, though in our country Corispermum Marshallii is more common, typical of abandoned potato fields in the dunes in the neighbor- hood of the sea. On the upper beach at Lake Bluff, Illinois, we studied among others a very interesting association of Lathyrus maritimus. This too is a marine species, occurring frequently on the Atlantic shore of America. It belongs also to the European coast-flora, having been found, e.g., on the Dutch beach. Finally I could mention the Russian thistle, the variety tenuifolia of Salsola Kali, which I remember from our visit to Miller, Indiana. This example however is less important, because we are treating the feature of the beach-flora, but we did not find this species on the beach, but only in the dunes proper. Coming to a con- clusion we may say, that, though the beach-flora of Lake Michi- gan on the whole is not so halophytic as it is in Holland, still some true halophytic types are present. It is not difficult to explain this fact, which at first sight might cause surprise. Life- conditions on the shore of Lake Michigan are extremely xero- phytic, the summer sun being very hot and a strong wind loaded with sand blowing generally along the plants. We know that halophytes are merely a form of xerophytes, as much salt in the soil renders it physiologically very dry. It is therefore clear that the life-conditions on the non-saline shore of Lake Michigan are xerophytic to such a degree that they become almost equivalent to the halophytic conditions that exist, e.g., in the neighborhood of Wood's Hole, Massachusetts, enabling in this way such plants as Euphorbia polygonifolia, Cakile edentula, Corispermum hys- THE DUNES OF LAKE MICHIGAN 209 sopifolium and Lathyrus maritimus to grow on this shore. So we have seen that the stucty of the beach-flora of Lake Michigan is interesting from a double point of view. It is especially fit to make one feel, that halophytes and xerophytes are in reality similar adaptations. I cannot close these notes on the beach-flora of Lake Michi- gan without calling attention to one very characteristic feature of the beach itself. I mean the line of driftwood, marking the upper limit of the middle beach, which is absolutely missing in my native country. It tells us on the one hand how rich the American country still is in primeval forests. We saw plenty of them ourselves. But on the other hand it shows how very prodigal Americans have been of their woods until now. So much wood has recklessly been cut in the forests on the moraine near Lake Michigan that large quantities of it could escape from the sawing-mills along the rivers and float to the lake without attention being paid to it. And one feels inclined to warn, to warn for the future, when all those forests will have disappeared, climates will change and no wood for human purposes will be available. Time has now come for a wise and economical man- agement of American forests, as we have long known to be true for our European ones. We now come to the second above mentioned point of differ- ence between the dunes of Lake Michigan and those in Holland, that is connected with the freshwater character of Lake Michi- gan in contrast with that of the salt North Sea. We have al- ready said that it is concerned with the quantity of lime in the soil. As the water of Lake Michigan is fresh, it does not hide the enormous numbers of testaceans, that are usually present in salt water and of which we find the shells in heaps on the strand. Hence the diluvial sand, that builds the dunes of Lake Michigan, must be very poor in lime. The sand of our dunes on the con- trary is, as a rule, very rich in lime and generally contains 3-4% of it. On the windward slopes of the fore-dunes the percentage can be much higher and rises to 12 or even 29%. Only in very old dunes, mostly situated far away from the sea, has the lime 210 THEO. J. STOMPS disappeared from the superficial layers of the soil. It has been dissolved by rainwater containing carbonic acid and by the influ- ence of humus substances. In this way the soil of these old dunes has regained the properties of a normal diluvial soil, as it is found in those parts of Holland that are covered by heath. Only here such typical calciphobous heath-plants as Pteridium auilinum, Juniperus communis, Empetrum nigrum, Ilex aquifo- lium, Genista anglica and G. tinctoria, Calluna vulgaris and Erica tetralix may be met with and they do not occur on the lime- containing sand of the younger dunes. If we now revert to our discussion of the dune-floras of Lake Michigan, we can not ex- pect to find here something like the succession just described. In fact lime is missing everywhere in the soil of the dune-region and the visiting botanist can gather this immediately from the composition of the flora. Everywhere his eye discovers species that are known to be more or less calciphobous. An interesting example that we found growing at Miller, Indiana, quite near to the Lake, is e.g., Pteridium aquilinum. This species is surely one of the most strictly calciphobous known and is nowhere to be found in our lime-holding dunes. Another example, also seen near Miller, Indiana, in the pine-dune-association, is Juniperus communis. This species passes for not so typically calciphobous as Pteridium aquilinum is. Still in our dunes it behaves as such and is strictly limited to the heath-covered parts, not being able to grow elsewhere. At Lake Bluff, Illinois, especially it showed to us with certainty, that even in young dunes no lime can be present in the soil. It was growing there almost on the beach, e.g., near the entrance of the ravine, in which we saw Thuja occidentalis in abundance, and on the third row of the miniature dune area, which somewhat farther to the north, has drawn our attention. So this second example turns out to be still more instructive from our point of view than the preceding one. More instances can easily be cited, but I believe that my argu- ment has been sufficient to show, that the freshwater character of Lake Michigan causes indeed a second fundamental point of difference between the dunes surrounding this Lake and those THE DUNES OF LAKE MICHIGAN 211 in Holland, the absence of a well pronounced succession, such as is found in the dunes of our country. In passing, a short remark may be made on some peculiar representatives of the flora of Lake Bluff, Illinois. One of them I have named already, Thuja occidentalis. We were told, that this is a tree of relatively northern distribution, which on the east side of Lake Michigan only occurs in the northernmost parts. Yet it is included in the flora of Lake Bluff, which is situated near the southwest corner of the Lake. This case be- comes still more interesting, when we hear that it does not stand alone and that the same holds true for several other species. The second and third row of small dunes on the beach at Lake Bluff were covered by Populus balsamifera, undoubtedly repre- senting the cottonwood and conifer dunes of other places, ac- tively moving dunes being absent here because of the feebleness of the easterly winds, that determine this dune-area. This too is a tree of relatively northern distribution, replacing at Lake Bluff the cottonwood, Populus deltoides, which we might, for instance, have expected from our studies of the dunes at Miller. Another example is Juniperus Sabina procumbens, one of the chief character-plants of the third row of the dune-area in ques- tion. Finally we could mention Betula alba papyrifera, large quantities of which grow on the forested cliffs near Lake Bluff. It is certainly interesting to note that so many northern species are found together here and it seems difficult to give an explanation. Thus far we have mainly dealt with the influence of the fresh water character of Lake Michigan on the adjacent territories. The principal difference between the dunes in my country and those of Lake Michigan is however caused by another factor. I mean the value of the soil behind the dunes, which is much higher in Holland than it is in the Chicago region. In conse- quence thereof much more attention has been paid to our dunes by man and great care has been taken to prevent them from moving farther landward, As is generally known, this has been attained by planting them with tufts of Ammophila arenaria, 212 THEO. J. STOMPS one of the sand-reed-grasses, wherever it seemed necessary and natural vegetation was only sparingly present. The resultant impression is one of artificial rather than of natural vegetation in our dunes. In the dunes of Lake Michigan, however, nothing of the kind is seen and nature rules supreme. This especially makes the study of this dune region so extremely interesting. Nowhere can the formation of new dunes and the encroachment of the dune-complex on pre-existing plant-societies be better studied. Seen from the beach our Dutch dunes offer a rather monoto- nous aspect. A low row of sandhills, almost equal in height and covered on their slopes and crests by tufts of the sea marram, extends all along the shore. Formation of embryonic dunes cer- tainly takes place on the windward slopes of these shore-dunes, but in a very slight degree. As sand-accumulating species only some of the above named halophytic beach-plants can be men- tioned, especially Agropyrum junceum and Honkenya peploides and besides these Cakile maritima and Convolvulus soldanella. The sand, that is blown landward is completely captured by the plantation of A?nmophila on the foremost row of dunes. In binding the sand still other species are concerned, as Elymus arenarius, Agropyrum pungens, Festuca rubra, Sonchus arvensis, Glaucium luteum, Eryngium maritimum, Cakile maritima, Sal- sola Kali, Convolvulus soldanella, Atriplex littoralis and several other inhabitants of the Ammophiletum. Thus it will readily be understood that it is altogether out of the question that actively moving dunes could originate in my country. Not even do the fore-dunes grow considerably in height, because exceptional high storms take as much sand back to the sea as has been heaped up during a long period. Consequently, when one looks towards the interior from the top of a shore-dune, one sees an undulating country, here and there three miles broad, covered by vegetation all over. Some dunes are overgrown with thickets of Hippophae rhamnoides, others with Salix repens, others again with a dense carpet of mosses and lichens, the most important of which is Barbula ruraliformis, Near the horizon the eye may discover a line of wood, the border of human plantations on the oldest THE DUNES OF LAKE MICHIGAN 213 dunes. Somewhat dreamy is the aspect of the whole region. It is hardly necessary to say that nowhere wandering dunes are seen to encroach upon human possessions on the inside. How different from this is the situation on the shore of Lake Michigan. Here very many species help in building embry- onic beach-dunes. In the first place the above named herba- ceous plants of the beach, and besides these many others such as Salix syrticola and glaucophylla, Prunus pumila, Calamovilfa longifolia, Ammophila arenaria, Elymus canadensis and usually growing farther inland than the other types, Populus deltoides (cottonwood) or, northward, also at Lake Bluff, Populus bal- samifera. It is clear that the difference in halophytic appear- ance between our coastal flora and that. of Lake Michigan be- comes still more striking, if we take the dune forming plants into the sphere of our considerations. Still it is worthy of notice, that here again there is a resemblance, in so far as many of the just-named species or at least narrowly allied forms also occur in our shore-dunes. This holds true especially for the sand- reed-grasses. Equally richly varied as the formation of new embryonic dunes on the beach of Lake Michigan, is also the aspect of the dunes as seen from the Lake. Here high cottonwood-dunes arise immediately behind the beach and its embryonic dunes, and a complete study can be made of the dunes in the order of their development. There an extensive tract of bulky moving dunes, almost without any vegetation, presents itself to the eye. Yon- der the shore has been largely eroded by lake-action, the cotton- wood and pine-dunes have been swept away and oak-dunes bor- der the beach. In short, the appearance of the shore-dunes as seen from the beach of Lake Michigan is far from monotonous. In the same way the bird's eye view of the dune-region is much more interesting than it is in my country, especially where there are large areas of moving dunes with sparse vegetation, as is* the case at Dune Park, Indiana, Michigan City and Sawyer, Michigan. I shall never forget the splendid view we had from the top of the "Crater," the well known 200-foot-high dune at Dune Park, lying in the midst of an extensive tract of wandering 214 THEO. J. STOMPS dunes. A mighty impression they make, those enormous vol- umes of rolling sand. And that they are mighty can be seen, when they encroach upon swamps and forests, which they meet on their way, cover- ing them up as they go. Nothing is then able to resist their power. We were lucky enough to see something of this encroach- ment on preexisting plant societies near Dune Park and Sawyer. About these observations, however, I will not enter into a lengthy discussion. Dr. Cowles has done this in an excellent way in his The Oecological Relations of the Vegetation on the Sand Dunes of Lake Michigan.1 There is one point, however, which I should like to mention here. It is the behavior of certain swamp-plants, such as the willows and the red osier dogwood, Cornus stolonifera, when a moving dune is encroaching upon them. This behavior can very easily be understood by one who is acquainted with the habits of Salix repens, which is quite common in the dunes and swamps of Holland. He knows that Salix repens occurs in two types, the one on moist soil, standing erect, the other on slopes of dunes, crawling along the ground. So different are these two forms, that one might feel inclined to consider them as distinct elementary species. Still, that this assumption is unfounded is shown by the following observation. In order to prove this let us see what happens, when a moving dune has approached to the above named swamp-plants and begins to cover them. The erect habitus is lost and they begin to creep along the slope of the advancing dune, in the meantine shooting roots from their branches. This holds good of the willows as well as of Cornus stolonifera. Thus we see that these plants are able to leave their swampy localities and to adjust themselves to the dry conditions of the sandy slopes and this behavior is exceptionally important, because it enables the plants in question to partake in a powerful manner in the capture of an actively moving dune-complex by vegetation, in other words in preparing the dune-soil for the development of the pine-dune-association. But to the botanist this behavior is still more interesting from another point of 1 Bot. Gaz. 27, 1899. THE DUNES OF LAKE MICHIGAN 215 view and I wish to conclude my paper with this remark. We have already treated of the similarity between xerophytic and halophytic adaptations. Now we have seen, that certain swamp- plants are able to thrive on a dune-soil, which is dry to such an extent, that even most of the xerophytic dune-species are not able to stand these conditions. No wonder then, that in many books on oecology the supposition is admitted that swamp-plants and xerophytic species also belong to the same class of adapta- tions.2 A priori it does not seem difficult at all to argue this assumption. Swamp-soil, we read, is physically wet, of course, but physiologically speaking it is said to be very dry, mainly be- cause of the large amount of humous acids present in it. On swampy soil the plants would therefore behave as if they were living in xerophytic life-conditions. In other words, it is ex- pected a priori, that swamp-plants and xerophytes are similar adaptations and will be able to grow in each other's places. In Holland there are certainly plenty of species, that seem to prove the truth of this conclusion. Salix repens has already been named and other examples can easily be cited. There is e.g., Polygonum amphibium, which usually grows in ditches and swamps, but often also on the driest places in the dunes. In- versely several of our heath-plants, e.g., Calluna vulgaris and Em- petrum nigrum, are to be met with in our peat-bogs. Very in- structive in this regard are likewise the so called pine-bottoms, which we studied at Dune Park, Indiana. When a coniferous forest develops on established dunes, it usually happens on windward slopes and summits. But in certain low swampy de- pressions the pines may also appear and produce the pine-bot- toms in question. Here the life-conditions are "oxylophytic," there they are certainly xerophytic and again we could get the conviction, that the two sorts of conditions are in reality iden- tical. Still I am of the opinion, that we must be very careful in assuming the correctness of this hypothesis. Indeed I do not believe that swamp-soil may be called physiologically dry and I should say, that the explanation of the remarkable fact, that so 2 See e. g. E. Warming, Oecology of Plants, Oxford, 1909, p. 193 a. f . 216 THEO. J. STOMPS many species are common to both xerophytic and swampy lo- calities, must be looked for in quite another direction. Inthe first place I rather believe, that true swamp-plants, such as Polygonum Amphibium, that are able to thrive under xerophytic conditions, are extremely rare and only can do so by means of a double adaptation. Most of the plants in question — Salix re- pens also for instance — probably are typical of xerophytic life- conditions. These species are able to thrive on a swampy soil as well as in a botanical garden, if the struggle for existence with other swamp-plants be not too intensive. This is rarely the case, as a swampy soil is generally very poor in nutriment, which must exclude, of course, many species. If we further take into consideration that the xerophytic types in question are accus- tomed to bad life-conditions themselves, it can really not cause surprise that we meet them now and then in swampy places. In this way I believe that we must understand the phenomena just described, though I will not decide, of course, whether the swamp-plants growing on the dunes of Lake Michigan, are origi- nally oxylophytic or xerophytic types. Coming to a conclusion I may perhaps say, that the main result of our visit to the dunes of Lake Michigan has been, that we got a better understanding of the value of the adaptations of halophytes, xerophytes and swamp plants. NOTES ON THE DISSEMINATION OF VIRGINIA CREEPER SEEDS BY ENGLISH SPARROWS BARTLE T. HARVEY Bureau of Entomology, Colorado Springs, Col. On February 19, 1914, while on a collecting trip in the out- skirts of Colorado Springs, Colorado, my attention was at- tracted to a large number of bird excrements adhering to the rough bark of the trunk and limbs of a Cottonwood tree (Populus deltoides) , which was growing in a sandy flood plain some fifty feet from a small stream. Closer examination of this tree revealed the fact that it had evidently been used, for some time, as a roosting place by the English sparrow (Passer domesticus). Each excrement, then hard and dry, contained many seeds of the Virginia creeper (Parthenocissus quinquefolia). The excrements were plentiful and occurred from 10-25 feet above the ground. The Virginia creeper seeds in nature are covered with a berry-like pulp, which fact may explain why the seeds were eaten by birds. Moreover, for many weeks after the big storm of December, 2-5, 1913, in Colorado Springs, deep snow covered the ground, which fact may have compelled the sparrows to feed upon the berries in order to escape starvation. At once the idea suggested itself to test the fertility of these seeds, and many were gathered. Also berries were collected from a living Virginia creeper vine some two hundred yards distant. The seeds of these berries were used as a check in the experiment. A. SEED FROM BIRD EXCREMENT The twenty largest seeds were selected from ten excrements and planted one-quarter inch deep in a mixture of sandy quartz and loam soil. From four to eight seeds were found in each excrement. And, frequently the bird excrement completely enveloped the seed forming a hard covering over it. 217 218 BARTLE T. HARVEY B. SEED FROM VIRGINIA CREEPER The twenty largest seeds were chosen from the ten largest berries and planted one-fourth inch deep in a mixture of sandy quartz and loam soil. From three to six seeds occurred in each berry. It was a noticeable fact that the seeds from the bird excrements were larger on the average than those taken from the Virginia creeper berries. Of course, it is quite possible that the two classes of seeds did not come from the same vine. Again, it might have been due to the birds naturally choosing the largest berries for food. The seeds from both vine and excrement were planted on February 20, 1914, and examined on March 24, 1914, thirty- three days later. The following table indicates the results ob- tained, being based on a planting of twenty seeds from each of the above mentioned sources. Table showing the percentage of germination SOURCE Of SEED < o CONDITION HEIGHT IN INCHES NUMBER OF PLANTS PER CENT From the Virginia creeper. . . From the Virginia creeper. . . From the Virginia creeper . . . A B C Good Fair Poor If and over 1-lf 1 and under 7 5 5 35 25 25 Total germination percent 85 From bird excrement From bird excrement From bird excrement A B C Good Fair Poor If and over 1-lf 1 and under 10 6 3 50 30 15 Total germination percent 95 Referring to the foregoing table, it can be seen at a glance that the seeds taken from the bird excrement gave a higher percentage of good plants, a lower percentage of poor plants, and a higher total percentage of germination than did those seeds which came from a living plant. Again, the best developed plant from bird excrement seed measured 2\ inches in height, while the best developed plant from the Virginia Creeper berry DISSEMINATION OF VIRGINIA CREEPER 219 seed attained a height of but two inches. However, the seeds from the Virginia Creeper berries appeared to germinate, on the average, a few days sooner than did those seeds taken from the bird excrement. The seeds, in germinating, first sent down a tap root, and then raised their two seed leaves sidewise above the ground, while the stem formed an arch. Gradually this arch straightened until the seed leaves were borne erect, yet still enclosed within the seed coat, which finally split open and gradually wasted away until it dropped to the ground. Growth by the stem after that was more rapid. The seed leaves appeared to absorb the nutriment contained within the seed coat, for they were rather thick at first but soon became thinner and rapidly as- sumed a deeper shade of green. On July 23, 1914, fifty square feet of space was marked off on the ground surface beneath the tree from which the bird excre- ments containing seeds were gathered on February 19, 1914. This space was clear, shaded, and of southeast exposure, sur- rounded by a heavy growth of grass. The soil was alluvial sand. On fifty -square feet, seventy healthy Virginia Creeper seedlings were counted that had germinated under natural conditions. It seems reasonable to suppose that the most of these plants must have sprung from seeds that had passed through the digestive tract of English sparrows, as few excreta were found adhering to the trunk and limbs of the tree at this time. From the foregoing observation, it would appear that seeds of the Virginia Creeper can pass through the digestive tract of the English sparrow and still retain their germinating power to a marked degree. This being true, it follows obviously that the English sparrow may, under certain circumstances, be an im- portant agent in the dissemination of Virginia Creeper seeds in central Colorado. BOOKS AND CURRENT LITERATURE Vegetation of Florida. — Two recent papers have treated the vegetation of portions of Florida with a greater degree of detail than any of the previous publications on this extremely interesting state. Harsh- berger1 has described the region south of Indian River Inlet and Tampa, including the keys and the everglades, and Harper2 has described the portion of the state north and west of Cedar Keys and St. Augustine, which is the least known portion of Florida from a botanical standpoint. Harshberger treats the coastal vegetation and the less known plant life of the everglades and the interior swamp, marsh, and forest regions with equal detail. A large-scale map shows the precise distribution of the types of vegetation and a large number of uncommonly fine illus- trations give proof of the distinctness of these types. The leading up- land vegetations are the forests of Pinus clausa covering the sandy ele- vations along the coast and in the northeastern portion of the area; the forests of Pinus caribaea on oolitic limestone throughout the region; and the flatwoods of Pinus palustris. The region is depicted as one of climatic uniformity in which differences of soil and 'very slight differ- ences of elevation are responsible for the dissimilarities of the vegeta- tion. The porous soil and the rapid evaporation subject plants of the upland to extremely dry conditions, but the author has observed periods of heavy rainfall in which a saturated soil and a saturated atmosphere placed plants under conditions so unlike the customary ones as to lead him to suspect that the xerophily of the plants is due as much to the amplitude of the extremes of moisture as to the commoner conditions of low water supply. Topographic conditions are also responsible for the distribution of vegetation in the everglades, with their 4000 square miles of marshland dominated by Cladium effusum, their ponds, streams, and minor lakes, with a wealth of emersed and aquatic plants, their marginal prairies and pine forests, and the unique belt of Anona glabra which fringes the southern shore of Lake Okeechobee. Harper's treatment of northern Florida is based on some twenty 1 Harshberger, John W., The Vegetation of South Florida. Trans. Wagner Free Inst. Sci. 7:49-190. Pis. 10, with map. 1914. 2 Harper, Roland M., Geography and Vegetation of Northern Florida. Ann. Rep. Fla. Geol. Surv. 6:163-452. Figs. 41-90. 1914. 220 BOOKS AND CURRENT LITERATURE 221 geographical subdivisions, corresponding closely to those used in his report on the peat deposits of the state. The topography, soils, lead- ing economic features, and vegetation are separately described for each of these areas. A "quantitative" method devised by the author has been applied to the vegetation in such a manner as to give a rough approximation of the relative abundance of the leading species. Little attention has been given to habital differences in vegetation, but the contrasting features of the twenty areas with respect to the vegetation as a whole are very distinctly brought forth. Although the method of securing vegetational statistics is an indirect and somewhat arbitrary one the author confesses that he has sometimes adjusted them a little "if the results are obviously inconsistent with known facts." If there are some "known facts" in reserve why can't we have them? The au- thor has, nevertheless, covered a very large extent of country with his rapid field method and has brought out some interesting results in cor- relating the vegetation with the geographical and agricultural features of this regions. Only six of the areas have less than 60 % of their vege- tation composed of pines and other evergreens, and the general obser- vation is made that the richest soils produce the smallest percentages of evergreens. A list of the 126 species of trees in northern Florida is appended, with a brief statement of the habitat of each. A large num- ber of illustrations are collected at the close of the paper and a care- fully elaborated index is given, designed to further the use of the bulle- tin by the non-technical reader. Both of the papers under notice give internal evidence of the zealous emphasis which their authors place upon the investigation of vegeta- tion as contrasted with the study of the flora. In alluding to the fact that he made no collections in his field work Harper states that "those parts of the country where botanists are most particular about the cor- rect identification of plants are generally those where the least progress has been made along phyto-geographical lines." If this geographical observation is indeed true for the United States it is because our oldest botanical institutions and our best stands of highly diversified or nearly virgin vegetation are separated by great distances. We must not for- get, too, that most of our knowledge of the flora of the remoter portions of the country is due to the work of men located in the taxonomic centers. An impatience with regard to nomenclatorial exactness can be willingly brooked in a man who knows the flora of a region as well as our author knows that of the southeastern states, but it would seriously discount the phytogeographical work of a less experienced man. THE PLANT WORLD, VOL. 18, NO. 8, 1915 Ui LIBRA R 222 BOOKS AND CURRENT LITERATURE Harshberger, in discussing the same matter, states that accuracy in specific determinations is highly to be desired, but continues "vegeta- tion can be described without mentioning specifically a single plant." No one has yet done this but it is highly desirable to keep in mind the fact that in such work as Harshberger has done in Florida the names of the plants are a mere convenience, like the numbering of the buoys which mark a channel. It would be a notable event for some one to describe the vegetation of an extended region without using the names of any of the plants, for he would then be compelled to tell us a great deal more about the plants, and in fact would have to work much longer be- fore being ready to publish. To the navigator who depends upon the numbering of the buoys the numbers are very important; to the naviga- tor who takes his own soundings the numbers become superfluous. — Forrest Shreve. The Transpiring Power of Leaves. — Physiologists and ecologists will be particularly interested in BakkeV recent article on foliar trans- piring power as indicated by tests with cobalt chloride paper. The method used was essentially Livingston's modification of Stahl's well- known cobalt chloride method of studying plant surfaces as to their ability to give off water. A determination is made of the time required for the change in color (from blue to pink) of slips of filter paper im- pregnated with cobalt chloride, when they are placed over a standard water-supplying surface of saturated blotting paper blanketed by a millimeter of air. The time required for the same change of the same slips is then determined when these are applied directly to the transpir- ing plant surface, by means of small glass clips. The ratio of the length of the first time to that of the second is the index of transpiring power of the plant surface in question ; it is a number which expresses the relative ability of the plant surface to supply water to the atmos- phere, and is directly comparable with other indices similarly obtained for different plants, or for the same plant at different times. It was the object of the investigation here reviewed to test the method upon a large number of plant species and upon different individuals of the same species. The work was done at Tucson, Arizona, upon plants growing mostly under irrigation. A detailed study of the daily march of the foliar transpiring power of 1 Bakke, A. L., Studies on the transpiring power of plants as indicated by the method of standardized hygrometic paper. The Journal of Ecology, 2:145-173. 1914. BOOKS AND CURRENT LITERATURE 223 Quamoclidion multiflorum gave results similar to those previously ob- tained hy this method2 and by the method of "relative transpiration."3 The latter method, as will be remembered, consists essentially in deter- mining the ratio of the rate at which a plant gives off water to the rate at which a standardized atomometer loses water by evaporation. To obtain a preliminary idea of the relative magnitudes of the diurnal and nocturnal indices of transpiring power, day and night observations were made upon a number of plant forms. There was found to be a broad range in the day-night ratio. The direction of the variation was found to be especially interesting: in the case of the more xerophyllous forms the ratio was generally less than unity; while it was usually greater than unity for the more mesophyllous forms. Plants of Verbascum thapsvs furnished opportunity for comparison of the relative transpiring powers of leaves upon the same stem but at different heights above the ground. The indices obtained for upper and lower .surfaces, and the averages of these indices (representing the whole leaf surface) showed that the lower, older leaves exhibited lower transpiring powers than did the higher, younger ones. A necessary conclusion was that position upon the stem and age of leaves may be important in determining transpiring power, and also that an adequate idea of the foliar transpiring power of the plant as a whole can only be obtained by tests of a fairly large number of leaves. Tests upon trans- piring power of floral parts showed that there was variation in this characteristic between different species, but that floral and foliar trans- piring power were of about the same order of magnitude in plants of the same species. Wilting has deservedly received much attention at the hands of in- vestigators of the water-relations of plants, and studies here reported by Bakke upon wilting plants indicate that the method of standardized cobalt chloride paper should prove of great value in the study of this phenomenon. These studies showed that there is a marked fall in transpiring power as the plant wilts. Furthermore, they indicate that the time required for wilting in the case of plants surrounded by air having a high evaporating power is longer than that required with low evaporation rates, but that the amount of decrease in transpiring power is greater in the latter case. The author suggests that the need of 2 Livingston, B. E., The resistance offered by leaves to transpirational water loss. Plant World 16:1-35. 1913. 3 Idem, The relation of desert plants to soil moisture and to evaporation. Pub- lication 50 of the Carnegie Institution, 190G. 224 BOOKS AND CURRENT LITERATURE irrigation might be predicted by this method of testing leaves, long before wilting is evident. Probably the most valuable point brought out in this article, and certainly the most interesting one to ecologists, relates to an ecological classification of plants based upon foliar transpiring power as shown by this method. The diurnal transpiring powers were determined for a large number of plants growing under irrigation. Plants which are un- questionable mesophytes exhibited indices of diurnal foliar transpiring power of 0.70 or higher, while all plants exhibiting similar indices of 0.30 or less would be pronounced xerophytic without hesitation, on the basis of simple observation. Although much more work must be done before a relative scale of xerophytism or of mesophytism can be erected, this preliminary study makes it certain that the method here employed offers a simply applied means for an ecological classification based upon quantitative measurements. Drought resistance in cultivated crops, in S3 far as water withholding capacity is concerned, can also be meas- ured by this method, as Bakke shows by experiments upon two very different varieties of alfalfa and upon two forms of Sorghum halepense, Johnson grass, and Sudan grass. Further work in this direction should prove very interesting and valuable for economic purposes. The paper here reviewed merits the attention of those engaged in studies in pure physiology, as well as of those investigating plants in the field, from either the agricultural or ecological point of view; the method seems to be very promising. — Samuel F. Trelease. NOTES AND COMMENT A committee of representative investigators in heredity and varia- tion have announced their intention to inaugurate a new journal en- titled Genetics, provided a substantial body of support can be secured for it. The new periodical will be published bi-monthly, will contain about 600 pages per annum, and the subscription price will be $6 per volume. Dr. George H. Shull, of Princeton University, is the Manag- ing Editor, and he has secured from the Princeton Press a promise of their willingness to manufacture the journal provided they can do so without too great an annual deficit. About seventy-five of the neces- sary two hundred and fifty subscriptions have already been pledged. The proposed size of the journal is exactly equal to the number of pages of American genetical work which Dr. Shull states were published last year in foreign journals. At the San Francisco Meeting of the American Association there will be three symposiums on botanical subjects: on the Gymnosperms, on the influences of light upon plants, and on the geographic distribution of plants. The titles to be read in the last of these are as follows : Dr. John W. Harshberger, The Diversity of Ecologic Conditions and its Influence on the Richness of Floras; Prof. D. H. Campbell, Factors Affecting the Distribution of the Components of the Flora of Califor- nia; Dr. Forrest Shreve, The Role of Physical Factors in Determining the Distribution of Plants; Prof. F. E. Clements, Plant Evidences of Climatic Cycles; Succession in the Bad Lands; Dr. W. A. Cannon, Dis- tribution of Cacti with Reference to the Role played by Root-Response ; Dr. W. S. Cooper, The Chaparral and its Habitat, and Plant Succession in the Palo Alto Region. A third edition of Chamberlain's Methods in Plant Histology has been issued by the University of Chicago Press. The book presents all of the valuable features of the second edition, at the same time that it embodies the improvements in microtechnique made in the ten years that separate the two editions. A chapter on photomicrographs and lantern slides has been added. The detailed and trustworthy descrip- 225 226 NOTES AND COMMENT tions of the use of various reagents and imbedding and staining methods, as well as the specific descriptions of the best methods for use in the several plant groups, and the directions for the laboratory management of living material, make this an invaluable book for students and teachers of the morphology of plants. Among the papers which will appear in early forthcoming issues of The Plant World are the following: A Study of the Root Systems of Prairie Plants of Southeastern Washington, by J. E. Weaver; Acid Accumulation and Destruction in Large Succulents, by E. R. Long; The Effect of Vanillin as a Soil Constituent, by J. J. Skinner; A Rela- tive Score Method of Recording Comparisons of Plant Conditions and other Unmeasured Characters, by E. E. Free; and Notes on the Ances- try of the Beech, by Edward W. Berry. The Rural Science Series, published by the Macmillan Company, now comprises some thirty-four hand-books and text-books, the most recent of them being the thoroughly revised twentieth edition of Pro- fessor Bailey's Principles of Fruit-Growing. The volume is not only concerned with the principles of the subject, but is even to a greater extent devoted to a complete exposition of the practices of fruit growing, from the selection of an orchard site to the packing of the ripened crop. A STUDY OF THE ROOT-SYSTEMS OF PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON rf% "*>*« HERA University of Minnesota, Minneapolis, Minn. V"""^\. i. & m EAVE "^* j While carrying on a study of the plant formations and associ- ations of semi-arid southeastern Washington in 1912-1914, it soon became apparent that for a proper understanding of the development and structure of these associations a knowledge of the root-systems of the more important prairie species was imperative. Consequently, during the fall, winter, and spring of 1913-1914, more than 350 root-systems of 25 of the most important ecological species were examined. This paper con- tains descriptions of these, together with a discussion of the con- ditions under which the plants grow. The prairies of southeastern Washington, and their eastward extension into adjacent Idaho, occupy a position between the foothills of the Bitterroot Mountains on the east, and the sage- brush region of western Adams, eastern Franklin, and western Walla Walla counties, Washington, on the west. On the south they are bounded by that high upfold of the lava-rock known as the Blue Mountains. Northward the Spokane gravels, ex- tending somewhat southward of Spokane, with their open growth of yellow pine, mark at once the general northern bound- ary of the exposed part of the great lava sheet and its accompany- ing prairie formation. As the great Columbian Plateau with its wind-moulded hills ascends to an altitude of 2700 feet near its eastern border, the precipitation correspondingly increases, and this reflects itself in a more highly developed type of prairie vegetation. In fact, the well-developed high prairies occupy a relatively narrow belt of 30-50 miles in diameter along the eastern edge of the plateau, while the area westward is char- THE PLANT WORLD, VOL. 18. NO. 9, 1915 228 JOHN ERNST WEAVER acterized by a very open type of Bunchgrass vegetation.1 Pull- man, Washington, the base station, where these studies were carried on, lies 85 miles south of Spokane and in the midst of the best developed type of prairie. THE FACTORS OF THE HABITAT Since the supply of water in this region is the chief limiting factor to plant growth, we shall first consider the total amount of precipitation, with its seasonal distribution (which is of greater importance than the total), after which the water content of the soil will be considered. Hemmed in on all sides by mountains, and especially cut off from the moist winds of the Pacific by the Cascades, the Colum- bian Plateau has a very low annual precipitation. In much of the area it is less than 10 inches, and even where the prevailing southwest wind, cutting through the mountain gap of the Colum- bia River and rising over the great High Plains, loses much of its moisture near the high eastern border, the annual precipita- tion is but 21 inches. In this semi-arid region where evaporation rates are very high, a knowledge of the distribution of rainfall and humidity is very important, for it is well known that scanty rainfall throughout the year, or relative dryness of the air and soil during the growing season, favors a sparse vegetation and the development of xerophytic forms. Since vegetation is not only an expression of present conditions, but to a greater extent a record of conditions that have obtained during a period of years; and since this record is not likely to be altered greatly by a year or two in which conditions may depart from the normal, a study of the precipitation in table 1 is instructive. This table gives the mean monthly precipitation at Pullman covering a period of 22 years, and is very representative of conditions in the High Prairies. It may be seen at a glance that over two-thirds of the pre- cipitation occurs during the non-growing season, and that the 1 The writer has under preparation a paper dealing in detail with the vegeta- tion of the prairies of southeastern Washington together with the plant associ- ations of the adjoining mountain-woodland formation. PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 229 light showers of July and August seldom have much influence on the water content of the soil. We may compare the soils of this region to a gigantic reservoir replenished mostly during the non- growing season, and (as will be shown) rather thoroughly emptied of its water during the summer. It is not the absolute rain- fall figures alone which furnish a criterion of climate, for the maximum duration of the drought period constitutes a limiting factor of the greatest importance. The great problem is the extent to which soil water derived from the winter precipitation is conserved through the weeks of drought. The rains in south- eastern Washington are so gentle that there is practically no run-off; and the silt-loam soils have a wonderfully retentive TABLE 1 Precipitation at Pullman (in inches) October 1 .70 April 1 .50 November 3.41 May 1 .84 December 2.66 June 1.20 January 2 .55 July 0 .57 February 2.18 August 0.68 March 2.02 September 1.29 Total 14.52 Total 7.08 n power of holding the moisture. As pointed out by Shreve the influence of rainfall upon the distributional and seasonal activities of plants is obviously exerted chiefly through its power to replenish soil moisture, and while rainfall is only mediate in its relations to plants, soil moisture is immediate. SOILS AND SOIL MOISTURE The prairie soils of the region have originated from the de- composed underlying basalt. By the action of water, and especially by the prevailing southwest wind, the prairie topography has been moulded into rounded hills which reach a height of 100 to 360 feet, and resemble sand dunes. The soil is usually many feet deep, and only along the canyons of streams is the lava-rock exposed. The wind has drifted much surface soil and humus 2 Shreve, Forrest, Rainfall as a Determinant of Soil Moisture. Plant World, 17:9-26, 1914. 230 JOHN ERNST WEAVER material from the exposed south and southwest slopes and de- posited it upon the steeper north and northeast leeward slopes. Table 2 gives the mechanical composition of the first foot of soil on a northeast and southwest slope respectively. As is characteristic of dry regions, the transition from soil to subsoil is not well marked, although the lighter colored subsoil appears much nearer the surface on exposed than on sheltered slopes. The humus content of the soils of north hillsides is greater at all depths to 5 feet, in some cases more than 12% greater, than on the exposed slopes, as was shown by six sets of humus determinations made for each foot of soil on the two slopes, respectively. This combination of more clay and more humus on the north and northeast slopes reflects itself especially TABLE 2 Mechanical composition of the firstfoot of prairie soils on a southwest and a north- east slope respectively STATION TINE GRAVEL 2.00 TO 1.00 MM. COARSE SAND 1.00 TO 0.50 MM. MEDIUM SAND 0.50 TO 0.25 mm. FINE SAND 0.25 to 0.10 MM. VERY FINE SAND 0.10 TO 0.05 MM. SILT 0.05 to 0.005 mm. CLAY 0.005 to 0.000 MM. Southwest slope. . . Northeast slope... . 0.00 0.40 0.60 0.40 0.60 0.90 0.40 1.50 23.58 33.16 73.30 53.50 1.49 10.03 in the increased water-holding capacity of the soil. An average of six determinations gave a mean water-holding capacity of 56% (based on dry weight at 104°C.) for the first foot of soil on north slopes, as compared with 48% on south slopes. This margin of 8% is rather an important difference in favor of the soils on the protected slopes, since the wilt- ing coefficients of the two soils differ but little. These sub- stratum differences are pointed out here since it will be shown later that certain plants are quite confined to moist north and northeast hillsides. Studies of the water content of these soils have been carried on since the spring of 1912. It will be unnecessary to burden the reader with all of the data and graphs obtained, and only enough will be given to make plain the seasonal march of soil water. In figure 1 are graphs giving the march of soil water from April 25 to September 25, 1913, on a typical northeast and PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 231 southwest prairie slope, respectively. The ordinates represent percentages of soil moisture in the first 10 inches of soil, on the dates indicated by the abscissae. The rainfall between the intervals of readings is also shown in inches, each ordinate rep- resenting 0.1 inch. The horizontal solid and broken lines show the wilting coefficients of the soils on the northeast and south- west slopes respectively.3 The greater amount of moisture on the northeast slope (in some cases being twice that of the south- west slope) may be noted at a glance ; while the fact that the soil on the exposed slope reached its wilting coefficient about July 15, and more than five weeks before similar conditions obtained on the sheltered slope, is significant. Records for the fall of 1913 were discontinued when the rains of late September re- plenished the moisture of the parched soil. In 1914 these 10- inch soil moisture determinations were made only at longer intervals and with the object of determining the time at which the wilting coefficient was reached. The water contents on the dates of these determinations are indicated by the light lines (fig. 1), the solid line representing soil moisture on the northeast slope. The rainfall for June, 1914, being approximately normal (and not 1.6 inches in excess of the mean, as in 1913) the wilting coefficient of these soils was reached much earlier than in the preceding year. An examination of these determinations to- gether with the rainfall records at Pullman, shows that at no time after June 28 and until September 14 was there water avail- able for plant growth in the first 10 inches of soil on the south- west slope. Only 0.13 inch of rain fell in July, none in August, and the light showers of the first 13 days of September gave a total precipitation of only 0.33 inch. The autumn and winter rains replenish the water lost during the long period of drought and in the following spring the soils again show a maximum water content. Soil moisture records obtained at 6 inches and 12 inches respectively, at the prairie stations on the two slopes from October 15, 1912, to January 1, 3 Samples of 100-150 grams of soil were invariably taken in duplicate, dried in an oven at 100-104°C, and the water content calculated in percentages on the basis of the dry weight. 232 JOHN ERNST WEAVER 1913, well illustrate this process. On October 15 the north-side soil had a water content of 17.4*% and 23% at 6 inches and 12 inches respectively, while that on the south slope had only 11% and 12% at the two depths. The graphs show a general in- crease of water content (except for a trough in late November) May June July August Sept. ■36 •32 •30 ■16 ■26- ■24 / / / ■20 ■18 •16 ■14- "m.. V, < \ \ l-\ V- \ / f 1 \ \ \ X I < N f \ \ \ \ / / / — V ■>, > f ' 12 ■10 fl - \ \ ■»* » ^ -T ■*- \ > i ■•^ ^ < s / 181 1 ffi ' > ** — \ \ • / \ t b mm I! 11 ki ill IIBL ill ill lilllli 'i mini mm ^ ■ HI 1 Fig. 1. Graphs showing the march of soil water to a depth of 10 inches from April 25 to September 25, L913, (heavy lines), and from May 22 to August 10, 1914, on a northeast slope (solid lines), and a southwest slope, respectively. and on January 1 the water content had increased to 31% and 41% respectively, on the north slope, and 28% and 28% on the south slope. It is apparent from these data that prairie plants must obtain their water from greater depths than 10 inches, at least during the dry summers. In fact, some of these plants penetrate to a PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 233 depth of 12 or 13 feet, while most of them get the bulk of their water from the second to the sixth foot of soil. ( 'consequently a consideration of soil moisture at these depths is imperative for a proper understanding of root environment. These deeper soil water determinations (many to a depth of 8 feet) were taken at intervals from December, 1912, to August, 1914. Samples were taken in duplicate from separate holes. Figure 2 (solid lines) Fig. 2. Graphs showing the march of soil water to a depth of 5 feet on a southwest slope from April 18 to August, 15, 1914; and the water contenl of the soil on December 13, 1913. The dotted lines indicate water contents on a nor, h- east slope. shows the march of soil water from early spring until late summer of 1914, on a southwest slope. It is apparent that there was still a downward movement of water at depths of 4 and 5 feet after April 18; but from June 3 to August 15 the soil moisture was gradually depleted at all depths to 5 feet. The heavy horizontal bars give the wilting coefficients at the depths indi- 234 JOHN ERNST WEAVER cated. On July 6 no water was available in the second foot of soil and only a small margin over the wilting coefficient was present at 3 feet. The broken line indicates that on December 13 of the preceding winter the soil was drier at 3, 4 and 5 feet respectively, than at any other time indicated. The fall rains had not then penetrated beyond 2 feet. While excavating root-systems during the fall, winter, and spring, an excellent 7o o •6" 6 ■12" z' 3' 4' 5' _ August 15 12 -14 X / •N. ^^^m^00^ i6 Ju|y6 X / ^ X ' June 3 - 20 / x /< ■22 1 ^ / / -24 1 /X / \ / . £6 / >. 2B Dec.6,1913 ^ -30 -32 -34 April 18 36 Fig. 3. Graphs showing the march of soil water to a depth of 5 feet on a northeast slope from April 18 to August 15, 1914, and the water content of the soil on December 6, 1913. opportunity was offered to study the rates of penetration. The water penetrated very slowly and at about equal rates on all slopes. By October 18 only the surface layer of 8 inches was wetted, and in late March the wet soil reached a depth of not more than 4 feet. The dotted graphs in the figure indicate the soil moisture on the northeast slope. Aside from the lower PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 235 temperatures and greater humidity of the north slopes, the actual amount of moisture available to these soils is important in ex- plaining the observed differences in moisture content. The same agency that has so profoundly affected the topography, namely the wind, also drifts over to the sheltered slopes much snow, which upon melting adds to the soil water. Two examples will suffice. In February 1914, exposed prairie slopes had a blanket of snow from 5-8 inches deep, while on the sheltered slopes at the same time drifts 48-52 inches in depth were measured. The second, while an extreme case, is illustrative. During February TABLE 3 The march of soil water on a northwest and south slope respectively. 1914 MAY 22 JULY 6 AUGUST 15 0"-6" N.W 23.4 12.5 25.7 17.9 27.0 19.9 30.2 20.2 27.2 22.0 24.3 22.4 15.2 11.1 13.7 11.4 18.9 12.6 23.7 13.2 24.9 17.3 21.3 19.6 11 6 S 6"-12" N.W 6.7 12.1 S At 2' N.W 10.2 11.8 S 10.2 At3' N.W 14.4 S 10.6 At 4' N.W.... 18.0 S 10.5 At5' N.W 19.5 S... 12.3 and March, 1913, while only 1 foot of snow lay on the south and southwest slopes, the protected northeast slopes were covered with drifts of well packed snow from 10-13 feet deep. In figure 3 is shown the march of soil water similar to that in the preceding figure, but for soils of a northeast slope. Here again, the downward movement of water at 3 to 5 feet after April 18 is apparent, as is also the gradual depletion of soil water at all depths to 5 feet. Likewise, the broken graph indicates conditions similar to those explained for the corresponding graph in figure 2. On August 15, no soil water was available above the 2-foot level. If the graphs in this figure are compared with the corresponding graphs in the preceding, it may be readily 236 JOHN ERNST WEAVER seen that in all cases, except on July 6 and at a depth of 5 feet, a higher water content was, maintained in the soils on the north- east slope. In order to further check these deep soil water conditions samples were again taken in duplicate on the northwest and south slopes of another prairie-covered hill. These findings, indicated in table 3, check very closely with the preceding, and the striking difference between soil water content on the two hillsides at all depths is well shown. It may also be noted that at each determination the soil at any depth was much drier than at the same depth at the pre- ceding determination. On the south slope, it is interesting to note that without exception the soil moisture increased with depth, and that the same condition maintains in most cases for north-side soils. Thus, it may be seen that topography with soil texture is the great middleman that distributes the soil moisture to fill the gigantic earthen reservoir, which again is largely emptied during the following growing season. The common farm practice in the Palouse region of alternating season after season the growing of wheat with summer fallow, is a method of storing the moisture from one year for use in the growth of the next year's crop. TEMPERATURE The observations on the temperature of the soil consist of two series of readings, namely, of a continuous one by means of a thermograph and of a very large number of readings of ther- mometers. The thermograph records are at a depth of 4 inches ' April 22 to June 9, 1913) and 3 inches (June 5 to August 15, 1914) respectively, on a southwest slope. Comparative tempera- tures on the northeast slope were taken at frequent intervals. The other thermometer readings are mostly for depths of 1 foot, and a number of readings were made at each foot to depths of 8 feet. The thermograph records show an undulating line of which the curve crests correspond to the warmest period of each day, and the depressions to the coldest. The crests for any (7 day) MAY June * July ,'\Aug. ■ • I / \ -9d / i \ \ 1 / \ \ 1 1 - ck? i \ \ \ \ 1 1 / t i \ \\ 1/ 1/ s\ - 86 // j/ > ^ 7 i N / 4 - Aft - _ ""•^ i \ T 1 ; / \ T / / \ T / \ t / \ r A 1 ' - (V q . -68 / / \ / / \ \ ' / i -64 / / \ \ ' / / / } bZ / / \ / - 60 / - DO / i / / -56 - f i ^ / * -54 / > / / ' \ / -50 * / / t / V / / -42- i i \ / f / \ i / / / \ \ I i i ' -38- / / > t i i / / - oo / / Fig. 4. Graphs showing the average weekly maximum and minimum soil temperatures (solid lines), and air temperatures for 1913 (first series), and L914, on a southwest prairie slope. 237 238 JOHN ERNST WEAVER ■ record are remarkably uniform in height, as are also the depres- sions uniform in depth. The difference between the crests and the depressions is shown in figure 4 where the average weekly minimum and maximum soil temperature (solid lines) are recorded, since these are more important to plant growth than the mean. The differences between these averages increase from about 10°F. (at 4 inches depth) April to June, to about 24°F. (at 3 inches depth) in July and August. For purposes of com- parison graphs representing the average weekly maximum and minimum air temperatures (at 3 inches above the soil surface and in the shade) recorded at the same station are also given in figure 4. TABLE 4 Soil temperatures at a depth of 3 inches N.E. slope S.W. slope N.E. slope S.W. slope N.E. slope S.W. slope MINIMUM TIME MAXIMUM TIME RANGE a.m. p.m. 63.5 5, 75 3 11.5 67 7 93 4 26.0 59 5 71.5 3 11.5 68 7 94 4 26.0 61 5 73.5 3 12.5 67 7 95 4 26.0 July 27 July 27 July 28 July 28 July 29 July 29 It is interesting to note that, while the soil temperatures at night were always warmer than those of the air, on many days during June, July, and August the air temperatures were lower than those of the soil. Owing to the lagging of the soil temperature the maximum was not attained until about 4 p.m. and the minimum at 7 a.m. as compared with 3 p.m. and 5 a.m. respectively, for maximum and minimum air temperatures. The seasonal march of soil and air temperatures varies inversely with the soil water. That is, the temperatures steadily become higher in proportion as the soils become drier. This condition occurred on both slopes, but the temperatures were lower and the extremes of variation less on the sheltered side. A single example of maximum and minimum soil temperatures on the two slopes and at 3 inches depth must suffice here. PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 239 The three days from July 27 to 29 were clear, and, judging from records of preceding and following days, quite typical. The daily maximum air temperature was reached somewhat earlier on the north than on the south slope, and was from 2°F. to 3°F. lower. A comparison of a large number of temperature readings at 1 foot on the two slopes brings out the facts that at this depth the daily range of temperature is seldom over 1°F.; that the south- west-side soils are from 3°F. to 5°F. warmer in early spring than those of the north slopes, and that these differences may increase by late summer to 7°-10°F. Table 5 indicates these temperature differences of the soils of the two slopes to a depth of 5 feet, in TABLE 5 Soil temperatures at 1-5 feet on April 18 and August 15, 1914, on a northeast and southwest slope, respectively APRIL 18 AUGUST 15 Depth 1' N.E. 45.7 45.1 45.0 45.0 45.0 s. w. 50.3 50.0 48.2 47.0 46.4 N.E. 65.0 61.7 58.0 57.2 54.5 s.w. 73.0 70.0 3' 4' 5' 66.2 64.4 62.6 early spring and in late summer. Undoubtedly the higher soil temperatures prevailing on the south side have much to do with the earlier seasonal activities of many plants.4 OTHER FACTORS Just as the possible growth of the aerial parts of plants is affected by the extent of the development of the root system, conversely the environmental conditions to which the aerial parts are subject, especially as concerns their water relations, must reflect themselves in the root development. Therefore, it will be instructive before passing on to a consideration of the 4 Several species of plants were observed to blossom from 10 to 17 days later on north than on south slopes. 240 JOHN ERNST WEAVER root-systems themselves to consider briefly the above-ground environment. Enough will have been said about summer temperatures, if we add that the long days, mostly cloudless, are followed by cool nights, during which the temperature usually reaches 45°- 58°F. During the winter the ground seldom freezes below 4 inches in depth, and, of course, on the expqsed slopes the proc- ess of alternate freezing and thawing is most pronounced. A continuous record of humidity has been kept for more than two complete growing seasons and it has been" found that the air is often 5 per cent to 10 per cent drier on the exposed than on the sheltered slopes. It is not uncommon on the dry slopes and during late afternoons for the humidity to fall to 15-30 per cent, while during the night it may rise again to about 75 per cent or even 95 per cent. The wind, prevailingly from the southwest, is of great impor- tance to vegetation, because it increases the evaporating power of the air, and the greater saturation deficit increases transpi- ration. During the season of 1913 (April 16 to September 3) a total of 13,605 miles of wind passed over the southwest slope at a height of 0.5 meter, while only 56 per cent as many miles were recorded by the anemometer similarly placed on a northeast slope. In general, these conditions were duplicated in the season of 1914 with the ratio of 100 : 49 (April 18 to August 15). However, these factors of temperature, humidity, and wind movement, as Livingston has shown,5 may be quite satisfactorily summed up by measuring the evaporating power of the air. A rather detailed report of evaporation rates as determined by Livingston's standardized porous cup atmometers in prairie and other stations has already been made,6 in which it was shown that from May 5 to September 23, 1913, the average daily evaporation on the northeast prairie slopes was only 64 per cent of that on southwest exposures. Similar records for 1914 bear 5 Livingston, B. E., Evaporation and Plant Habitats. Plant World 11 : 1-10, 190S. 6 Weaver, John Ernst, Evaporation and Plant Succession in Southeastern Washington and Adjacent Idaho. Plant World 17: 273-295, 1914. PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 241 out this condition in general, with higher average daily evapo- ration on both slopes (23:9 cc. on northeast and 33.0 cc. on south- west) and a ratio on the two slopes of 72 : 100. *^ 1 Fig. 5. One end of a trench used in excavating root systems. Many roots of prairie plants reach depths of over 10 feet. When we consider that the daily evaporation in July and August often reaches a maximum of 40-55 cc, and at a time when the available soil water may be depleted to a depth of two feet, we can see the necessity for extensive root-systems in the sub- 242 JOHN ERNST WEAVER stratum, as well as aerial structures for enduring drought. Another fact of importance must not be overlooked. Owing to the cool nights the greater bulk of these high water losses (82.5 per cent as determined for three days in July) occurs during the day, and thus very xerophytic atmospheric conditions are brought to bear upon the plant. Summarizing briefly the factors of the habitat in which these studies were carried on, we find a region of moderate winter and low summer precipitation. The soils are composed of a fine silt-loom of high water-holding capacity, they are usually very deep, and the soil water extends down many feet beyond the greatest root depth.7 In early summer the superficial layers of soil soon lose all of their wTater available for plant growth, and as the season advances this condition occurs in the deeper soils, while the entire soil mass to a depth of 5 feet and beyond, gradu- ally yields up most of its available water. Soil temperatures at 3 inches show a daily range of from 3°F. to 24°F., while at 1 foot the daily range is seldom over 1°F. The seasonal range (April— August) of the soil temperatures varies from 22°F. at 1 foot to 16°F. at 5 feet. Air temperatures show a mean daily range varying from about 25°F. in April and May, to 38°F. in July and August. The cool nights on the high plateau tend to counteract the low humidity of the day and to reduce the high daily rates of evaporation. North and northeast slopes are less xerophytic than the south and southwest slopes. This is due in part to actually greater precipitation caused by blowing snow and in part to soil texture which is more open, has more humus, and a greater water- holding capacity. These factors are reflected in the greater amount of soil. water and in lower soil temperatures. Likewise, these slopes are sheltered from the drying southwest winds, and from the perpendicular rays of the sun. This is reflected in slightly lower air temperatures and greater humidity, and especially in the lower evaporating power of the air. 7 Wells dug only into the soil often afford a good supply of water, although usually they are drilled into the porous layers of basalt. See also Landes, Henry, Underground Waters of Washington. Water Supply and Irrigation Paper, No. Ill, 1905. PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 243 SCOPE AND METHODS OF THE STUDY OF ROOT-SYSTEMS The object of this study was to determine the depth at which the most important prairie plants obtain their water supply; to get accurate data on the distribution and extent of the root- systems in the soil ; and to examine enough plants of each species so that the conclusions might be thoroughly reliable. Finally, it was hoped to use these data in helping to solve the problems of succession and structure of prairie vegetation. Owing to the tenacious structure of the soil and the great depth of most roots, it was found impracticable to wash out the 1 Fig. 6. Lumps of soil taken at a depth of 5 feet on a northwest slope, showing the numerous large earth worm burrows. They are from 7 to 8 mm. in diametor and reach depths of more than 13 feet. root-systems. The method finally employed was to dig a trench 2 feet wide and 8 to 16 feet long to a depth of about 6 feet on the hillside where roots were to be examined. This offered an open face into which one might dig with a hand pick, and, after suffi- cient practice, and acquaintance with the soil texture, success- fully excavate a root-system almost in its entirety. Of course the trenches were deepened as work progressed and the working level sometimes reached to a depth of 10 or 12 feet. (See fig. 5.) Five of these larger pits were used and several smaller ones. THE PLANT WORLD, VOL. 18, NO. 9, '915 244 JOHN ERNST WEAVER The soils on the sheltered slopes were much more open in texture at all depths, and roots were removed with much greater facility than on south slopes where it was often necessary to use a pickaxe to open the trench. Root-systems were examined on the southwest slope, and on a northeast slope, both, respectively, near the stations where factor determinations were made; and also on a northwest slope near the station where deep soil moisture samples were taken as a check (see table 3). It should be made plain here that this last station was on a slope only slightly north of west but sheltered by a low westward extension of a ridge in such a manner as to combine more nearly northside substratum conditions with the aerial conditions, as regards exposure to wind and sun, approach- ing those of a south slope. A biotic factor affecting soil texture and one which shows a marked effect upon root-systems is the earthworm, a species of Lumbricus. The soils of north and northeast slopes especially, were literally honeycombed with holes ranging from 7 to 8 mm. in diameter and reaching depths of over 13 feet. (See fig. 6.) In the soil of south slopes the work of earthworms is much less in evidence, — perhaps less than half as many holes occur he:ce. Black soil was noted in these burrows at depths of 9-13 feet, perhaps in part worm-casts and in part surface soil washed down from above. Certainly these holes play a large part in the penetration of soil water, and it seems that the additional aeration they afford in these fine-textured soils might be of great importance. All the roots examined were of mature perennial plants. The practice followed was to examine six or more roots of a given species and then to write a working description of the roots. These descriptions were kept at hand in the field and as new roots of the same species were studied any variation from the original description was carefully noted. It is believed in this way that thoroughly reliable results have been obtained for the species studied. A few of the root-systems were photographed in place, but most of them were removed from the soil and afterward photo- PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 240 graphed, together with a meter stick, for purposes of comparing lengths. It was usually necessary to double the root one or more times in order to get it all on the ground glass at a distance close enough to' show the details of structure. Root-systems of the following plants were studied. NaOH with phenol- phthalein as indicator. In the tables to follow, the acidity of the sap, which was determined by the titration of 25 cc. samples, is 4 MacDougal and Spalding, Carnegie Inst., Wash., (Publ. 141) have shown that the proportion of sap to dry tissue varies considerably within the same plant in the sahuaro and bisnaga, the water content being greatest near the apex of the trunk and least at the base. ACID ACCUMULATION IN SUCCULENTS 263 recorded in the number of cc. of -nr NaOH required to neutralize 1 cc. of the sap. The increase in acidity in the morning samples is "apparent. This is what is to be expected in view of the greater intensity of VlRTICAL StCTlO/1 / v Vlbtical StCTIOM Cross - Stc-non E.CHIAIOCACTUS Cross -Stc-non Carnlgie.a Fig. 1. Diagram of Echinocactus and Carnegiea in section, showing regions from which samples were taken for analysis. light and heat acting upon the plants during the day. Relieved from the destructive action of these agencies, the organic acids which are formed wherever carbohydrates are being burned, tend to accumulate during the night faster than they are de- 264 ESMOND R. LONG stroyed, while in the day the reverse process takes place, so that the acidity of the sap is higher at the day's beginning than at its close. It would be expected furthermore that the accumulation of acidity during the night would bf the greatest where the concen- tration of carbohydrates is greatest, that is in the outer parts near the chlorophyll tissue, the seat of carbohydrate formation, and this is confirmed by the analytical tests. Taking the figures TABLE 1 Shoiving dry weight {in per cent), density of sap, and acidity of sap in three samples at different depths from each of three plants of Carnegiea. All plants collected July 18; analyses made at 5 p.m. on July 18, 19, and 21 , and at 8 a.m. on the morn- ings following. Plant No. 1 : height 126 cm., sampled 70-90 cm. from base; No. 2: height 134 cm., sampled 80-100 cm. from base; No. 3: height 110 cm. sampled 55-75 cm. from base 5 P.M. 8 A.M. PLANT SAMPLE Dry wt. Density Acidity Dry wt. Density Acidity f A 10.1 1.013 0.404 9.1 1.014 0.492 No.l B 5.9 1.010 0.324 7.4 1.012 0.388 1 C 11.6 1.014 0.148 12.6 1.015 0.172 r A 11.4 0.980* 0.368 9.4 0.987 0.556 No. 2 | B 8.6 1.008 0.408 8.2 1.010 0.456 ■ C 10.7 1.012 0.268 12.2 1.013 0.304 t A 5.5 1.008 0.544 6.1 1.009 0.616 No.3 | B 4.9 1.009 0.452 5.5 1.009 0.524 ■ C 5.7 1.009 0.320 6.4 1.008 0.300 Large amount of air in sap. from table 1 and subtracting the late afternoon value for acidity from that of the early morning, we obtain the results shown in table 2. The difference between morning and evening acidity is thus seen to be relatively great in the outer parts and slight in the cen- tral tissues. This is probably to be explained as follows. Near the surface of the plant, where soluble carbohydrates are plenti- ful, we have a relatively large carbohydrate metabolism as com- pared with the inner tissues, which because of their distance ACID ACCUMULATION IN SUCCULENTS 265 from the source of soluble carbohydrates, receive their supply- slowly and are therefore limited to a smaller carbohydrate metab- olism, so that acid production is less rapid than near the surface. Furthermore, as the center of the plant is approached, the in- creasing insulation tends to minimize temperature and light dif- ferences of night and day. Briefly stated there is a large accu- mulation of acids during the night in the outer parts and a large destruction of acids during the day, so that diurnal differences in acidity are large, while in the inner parts there is much slower formation of acids and only a slight diurnal difference in the TABLE 2 Showing differences in the acidity of sap in samples taken in afternoon and morning at different depths from plants of Carnegiea collected July 18 PLANT TIME SAMPLE A SAMPLE B SAMPLE C No. 1 < 8 a.m. 5 p.m. 0.492 0.404 0.388 0.324 0.172 0.148 - 0.088 > 0.064 > 0.024 * No. 2 • 8 a.m. 5 p.m. 0.556 0.368 0.456 0.408 0.304 0.268 • 0.188 ; 0.048 > 0.036 No. 3 \ 8 a.m. 5 p.m. 0.616 0.544 0.524 0.452 0.300 0.320 { 0.072 0.072 > -0.020 action of light and heat upon them, so that diurnal differences here are small. In the protocols to follow it will be seen that the same condi- tions exist in the bisnaga (tables 4 and 5). The facts expressed in the accompanying tables agree in the main with those outlined above in the case of the sahuaros. Bisnagas 28, 29, 32 and 33 are distinctly more acid in the early morning than in- the late afternoon and with only one partial exception the difference in acidity of corresponding samples of the two periods progressively becomes smaller as the cen- ter of the plant is approached. In bisnaga 29 the increase 266 ESMOND R. LONG in morning acidity over preceding afternoon acidity, is greater in the case of B than in A. It is probable that the lateness of the hour of analysis (9 a.m.) is partly responsible for this condi- tion, i.e., that the photolysis of acid in A was already under way. From B to D the usual condition of a progressive decrease in the subtraction value, is observed, until at D the acidity of morning and afternoon sap is practically the same. Bisnaga No. 27 pre- sents a contrast to all the other specimens studied in that the sap of A is more acid in the afternoon than in the early morning, and the subtraction value becomes larger instead of smaller as the center is approached. No satisfactory explanation can be given for this discrepancy. Apparently metabolism was not very active, for the differences between day and night acidity are not great at any point. Owing to adverse weather conditions early morning analyses were not made of Nos. 30 and 31, these being included in the protocols merely to show some other rela- tions of interest in the general discussion. DISCUSSION A glance at the tables shows a constant feature with regard to the water distribution. In morphologically similar tissue, that is from A to D inclusive in the bisnaga and in A and B in the sahuaro, the dry weight of the tissue decreases as the center is approached. (E of the bisnaga and C of the sahuaro, each within the fibro-vascular cylinder of the plant are more woody than the tissues peripheral to the ring and are characterized by a relatively low water content and low acidity.) This is presumably the re- sult of an active transpiration in which water is removed from the superficial tissues more rapidly than it is supplied by conduc- tion and diffusion from the interior. It would be expected that in the nightly checking of transpiration the outer tissues would tend to " catch up" in water content at the expense of the inner ones, that is, that the inside tissues would become drier and the outside ones wetter during the night, and that the morning anal- ysis would show a more even distribution of the water than in the preceding evening. And this is actually found to be the case ACID ACCUMULATION IN SUCCULENTS 267 TABLE 3 i Showing dry weight (in per cent) and acidity of sap in four samples at different depths from each of seven plants of Echinocactus. Plants 27 to 29 collected June 30; Plants 30 to 32 collected July 8; Plant 33 collected July 18 AFTERNOON MORNING PLANT WEIGHT DATES AND HOURS SAMPLE Dry wt. Acidity Dry wt. Acidity No. 27 kg. 20 June 30- July 1 A 11.9 0.376 10.0 0.342 4 p.m., 8 a.m. B 10.7 0.269 9.0 0.278 C 7.7 0.154 7.5 0.166 D 6.7 0.143 7.1 0.166 No. 28 12 Julyl-July2. A 11.1 0.145 10.6 0.184 3 p.m., 9 a.m. B 9.0 0.142 9.4 0.168 C 7.5 0.147 7.7 0.172 D 6.8 0.152 7.2 0.168 No. 29 25 July 4- July 5. A 12.1 0.400 10.9 0.472 4p.m., 9a.m. B 9.2 0.320 9.1 0.472 C 7.4 0.196 5.9 0.256 D 7.1 0.166 6.6 0.180 No. 30 17 July 8*. A 10.0 0.136 3p.m. B C D 9.3 7.8 7.3 0.144 0.216 0.212 No. 31 20 July 9*. A 8.2 0.124 3p.m. B C D 6.5 4.7 4.3 0.120 0.100 0.088 No. 32 15 July 10- July 11. A 6.0 0.156 6.4 0.232 4p.m. ,7a.m. B 5.3 0.180 4.7 0.208 C 3.9 0.192 3.3 0.192 E 9.6 0.120 No. 33 12 July21-July22. A 8.0 0.140 6.4 0.256 6p.m., 7a.m. B 6.6 0.176 5.4 0.232 C 5.9 0.236 4.6 0.192 * Because of heavy rains during the night, which probably affected the plants through the exposed surface, morning analyses were not made. in most of the plants studied. For example, the difference in water content of A and B in sahuaro No. 1 is 4.2 per cent (of the wet weight of the plant) at 5 p.m., and only 1.7 per cent at 8 a.m. 268 ESMOND R. LONG the next morning. Similar calculation for all the plants exam- ined gives the results shown in table 5 for the varying water content. If we assume that at a given time of day two halves of the plant are similar in water distribution, and this is probably fair in view of the symmetry of these plants, then the above figures simply show that generally the difference between the water content TABLE 4 Showing differences in the acidity of sap in samples taken in afternoon and morn- ing at different depths from plants of Echinocactus collected June 30, July 8, and July 18 PLANT TIME SAMPLE A SAMPLE B SAMPLE C SAMPLE D No. 27 • 8 a.m. 4p.m. ' 0.342 0.376 0.278 0.269 0.166 0.154 0.166 0.143 • -0.034 < 0.009 < 0.012 < 0.023 No. 28 < 9a.m. 3p.m. 0.184 0.145 0.168 0.142 0.172 0.147 0.168 0.152 ■ 0.039 > 0.026 > 0.025 > 0.016 No. 29 - 9a.m. 4p.m. 0.472 0.400 0.472 0.320 0.256 0.196 0.180 0.166 '• 0.072 < 0.152 > 0.060 > 0.014 No. 32 7a.m. 4p.m. 0.232 0.156 0.208 0.180 0.192 0.192 1 0.076 > 0.028 > 0.000 No. 33 7a.m. 6p.m. 0.256 0.140 0.232 0.176 0.192 0.236 ■ 0.116 > ' 0.056 > -0.044 of the external and internal simply diminishes during the night. During the day water evaporates from the surface more rapidly than it can be supplied by conduction and diffusion from the in- ternal parts. The lost water of the surface layer is replaced again at the expense of the interior (which by the excision of the plant was cut off from its water supply) during the night. Thus we may conclude from the general observation that the water ACID ACCUMULATION IN SUCCULENTS 269 content of the outer parts is higher (while that of the inner is lower) in the morning than in the preceding evening. Obviously this movement must be taken into consideration in a study of acidity. Since the dissolved acids of the interior sap will be carried along in the stream, they will tend to accumulate in the outer parts and thus increase their total acid content. The main features of the conducting system of the sahuaro and bis- naga are a central, woody, fibrovascular cylinder, with ramifica- tions extending from it to the chlorophyllous tissue. With such an extensive conducting system changes in the acidity of different zones due to movement of fluids might be expected. However as closer consideration and a study of the last tables will show, this effect is not marked. The amount of acid carried to the outer parts by conduction from the inner must be in proportion to the water, and the net result might be an in- crease or decrease in the acidity per cc. of the outer sap, accord- ing as the sap of the interior had a higher or lower concentration than that of the exterior. However the increase of water con- tent in a given area by movement from neighboring interior tissue is only 1 to 3 per cent (see tables on a.m. and p.m. water dis- tribution) , while the morning acidity may exceed that of the pre- ceding afternoon by as much as 50 per cent. It would seem therefore that sap movements play a very small part in the case in question and we may safely assume that the observed effects are due to nightly accumulation and daily destruction of the acid products of carbohydrate metabolism. As a glance at the tables will show, diurnal differences in the density of the sap are so slight as to be negligible. One point to consider further is the relatively high concentra- tion of acid observed in the outer parts in the early morning analysis. The acidity near the surface is often double or even triple the acidity of the sap at the center and usually becomes progressively lower as the center is approached. While no estimations of sugar concentration were made, it seems probable that this higher acidity in the outer parts is due to a higher con- centration of carbohydrates in the same regions. The synthesis of carbohydrates can take place only in the green tissue of the 270 ESMOND R. LONG TABLE 5 Showing differences in water content (in per cent) in samples taken in afternoon and morning at different depths from plants of Carnegiea (C) and Echinocactii* (E) CI. C2. C3. E27. E28. B A B A B A B A C B D C B A C B D C AFTKIiNOON 94.1 89.9 MORN'IXG 4.2 91.4 88.6 2. > 95.1 94.5 89.3 88.1 92.3 89.3 93.3 92.3 91.0 88.9 2.1 > 92.5 91.0 92.6 90.9 1.7 93.2 92.5 91.8 90.6 1.2 94.5 93.9 0.6 = 0.6 91.0 90.0 1.2 > 1.0 92.5 91.0 3.0 > 1.5 92.9 92.5 1.0 > 0.4 90.6 89.4 1.2 92.3 90.6 1.5 < 1.7 92.8 92.3 0.7 > 0.5 E 29. E 32.. E33.. B A C B D C B A C B B A C B AFTERNOON 90.8 87.9 MORNING 90.9 89.1 2.9 > 1.8 92.6 90.8 94.1 90.9 1.8 < 3.2 92.9 92.6 93.4 94.1 0.3 > -0.7 94.7 94.0 95.3 93.6 0.7 < 1.7 96.1 94.7 96.7 95.3 1.4 = 1.4 93.4 92.0 94.6 93.6 1.4 > 1.0 94.1 93.4 95.4 94.6 0.7 < 0.8 ACID ACCUMULATION IN SUCCULENTS 271 surface, which in the sahuaro and bisnaga is approximately 5 mm. in thickness, so that the cells of the rest of the plant are dependent for their carbohydrate nutriment upon diffusion and conduction from the exterior. It seems logical to suppose, as long as metabolism is continuous and no storing up takes place, that the further an area is from its source of supply of sugars the lower its concentration of sugar will be. And as the sugars are continually being broken down with the production of acids the concentration of the latter will be greatest where the sugar concentration is greatest, that is, near the exterior of the plant. It will be noticed in the tables that the situation is frequently reversed at the close of the day, that is, that the acidity is great- est in the interior and decreases toward the exterior, this being due as explained above, to the daytime destruction of accumu- lated acids. But it is significant that the nightly accumulation of acid always leads to a higher acidity of the exterior than of the interior. SUMMARY The acidity of the sap of Echinocactus wislizeni and Carnegiea gigantea is higher in the early morning than at sunset, the acids formed in the metabolism of carbohydrates tending to accumu- late during the night and being partially destroyed by higher temperature and photolysis in the succeeding day. The acidity of the sap of these species following the nightly accumulation of acid is higher in the outer than in the inner regions. This higher acidity is probably resultant from a higher concentration of sugar in the outer parts, that is, in the region of sugar formation. The diurnal difference in acidity of the sap becomes smaller in succes- sive zones as the center of the plant is approached, being as much as 50% in the exterior and slight in the innermost tissues. In the outer parts where carbohydrates are plentiful, sugar metabo- lism is great and acid production and nightly acid accumula- tion are large ; these parts are on the other hand the most exposed to the action of light and heat, so that the daily destruction of acid is great. Accordingly here diurnal differences in acidity are large. In the innermost tracts of tissue carbohydrates are 272 ESMOND R. LONG less plentiful, acid production is correspondingly less, and the increasing insulation as the center is approached tends to mini- mize diurnal temperature and light differences, so that in these parts diurnal differences in acidity are small. The movement of sap of low acidity from the central cylinder to the peripheral layers of these thick succulents has little effect upon the acid con- tent of these tracts, while variations of great amplitude result from the conjoint action of light and temperature. A STUDY OF THE ROOT-SYSTEMS OF PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON JOHN ERNST WEAVER University of Minnesota, Minneapolis, Minn. (Concluded) II. Agropyron spicatum (including var. inerme) (Fig. 10) This is the most common bunchgrass in eastern Washington. It has its best development westward of the high upland prairies of extreme eastern Washington and along the rim-rock through the eastern part. The bunches are often 10 inches in diameter and reach a height of over 3 feet. As many as 300 to 350 individual stems may occur in a single bunch. The plant blossoms in June and dries out in early July, only to take on renewed growth after the autumn rains, and remain green all winter. Figure 10 shows Agropyron on the rim-rock with its roots penetrating the rock crevices to depths of 45, 46 and 48 inches. Ten plants were examined under these conditions. The roots of all followed the cleavage planes of the basalt on an average to a depth of 4 feet and 1.3 inches, but one extended along the deeper moist crevices to a depth of 5 feet. In the well-developed highland prairies the bunch habit is partially abandoned and long rhizomes are produced. The clumps are always much smaller here, perhaps only a few centi- meters wide, but there are usually as many as 5-6 per square meter. Twelve prairie Agropyrons were examined. This grass has coarser roots than any of the other three important native grasses. These coarse, fibrous roots have many short laterals. Some of these roots reach a depth of 4 feet and 9.5 inches, al- though on an average 4 feet and 2 inches was the greatest depth attained. Five plants on a southwest slope gave an average depth of 4 feet and 1.6 inches, while seven on a northwest slope reached an average depth of only 3 feet and 2.6 inches. 273 274 JOHN ERNST WEAVER Festuca ovina ingrata (Fig. 11) The blue bunchgrass ranks in importance with Agropyron spicatum on the well-developed high prairies west of the foothills Fig. 10. Agropyron spicatum growing on the rim-rock and securing its water supply from the moist rock crevices of the broken basalt. of the Bitter-root Mountains between Spokane, Washington, and Lewiston, Idaho. Because of its abundance (often 10-13 bunches per square meter), the very appropriate name Palouse (Fr. Pelouse, a land clothed with a short, thick growth of herbage) PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 275 was early applied to the region. The slightly pale green plants are densely tufted into bunches from 1 to 4 inches in diameter, and, while the numerous setaceous leaf blades are mostly basal and about 12 inches high, the stems which bear flowers reach a height of 12 to 18 inches. The whole plant dries out considerably by the middle of July, but the autumn rains revive it, and it is green throughout the rest of the year. Festuca ovina has a great mass of jet black roots which occupy the soil thoroughly from the surface to a depth of about 18 inches, below which depth relatively few roots extend. None of the roots are over one millimeter in diameter. They branch pro- fusely to the third order mostly, and the laterals are usually less than an inch in length. This branching continues to the very tip, and there the laterals are usually longer. Twenty- two plants were examined. The longest root found was 3 feet and 3 inches, the average length 2 feet and 1.5 inches for the deepest roots, but the great bulk of roots were less than 18 inches long. All the plants examined were on a southwest slope. Poa sandbergii (Fig. 11) Sandberg's Poa is one of the earliest plants to gain a foothold upon the thin rocky soil of the scab-lands, and along the rim- rock. It grows in small tufts usually only from 0.5 to 1.5 inches wide, puts out new roots when the fall rains begin, grows through- out the winter and spring, and evades drought by flowering late in May or in early June, and remaining dormant the rest of the growing season. On the prairies it is an interstitial plant, often as many as 30-40 small tufts occurring in a single square meter on the dry south slopes. Poa has smaller roots than Festuca ovina ingrata, they are more profusely branched, and the fine laterals which are short (usually less than 1 inch) are more numerous, smaller, and much more branched. The creamy-white roots spread laterally 3 to 5 inches and occupy thoroughly the first few inches of soil, relatively few extending below a depth of 8 inches, and none were found beyond 13 inches. The root branches are longer and more 276 JOHN ERNST WEAVER numerous at the tip than are those of Festuca. Poa roots branch to the fourth order. Six plants were examined on the rim-rock with an average root depth of 7.2 inches. Eight prairie spe- cies of Poa growing on a southwest slope gave an average maxi- mum depth of 9.7 inches. Fig. 11. Three imporant prairie grasses. Koeleria cristata (to the left), Festuca ovina ingrata (center), and Poa sandbergii. All are relatively shallow rooted. Koeleria cristata. {Fig. 11) This is a very common bunchgrass on the prairies of eastern Washington, not infrequently occurring as abundantly as 6 clumps per square meter. However, the bunches are smaller in diameter (0.5 to 2 inches, usually) than those of Festuca ovina ingrata, and also of less height (1-2.5 feet) than Agropyron spicatum. Koeleria flowers in late June or early July and like Poa remains dormant until revived by the autumn rains. % PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 277 The roots, which are a dirty-gray in color, resemble those of Agropyron but taper down faster, and have finer laterals which branch mostly to the third order. These laterals, like those of the shallow rooted Poa, are more numerous than in Agropyron. Six plants were examined. The deepest root found was at 28 inches, and 15 inches was determined as the average maximum depth. Balsamorhiza sagittata {Fig. 12) The balsam root is, with the exception of Agropyron spicatum and Festuca ovina ingrata, the most characteristic plant of the high prairies of eastern Washington. Its abundance, size, and duration all unite to make it a very important ecological species. It is not unusual to find a dozen of these plants in an area of 4 square meters. Only on the steeper northeast slopes and wet valleys is it absent. A medium sized mature plant occupies an area of 4-5 square feet, may have as many as 50-80 of the large sagittate leaves, and a total leaf surface of 30 square feet. From the short, thick, multicipital stem (I have counted 39 individual shoots on a stem 9 inches in diameter) the new leaves appear in April. By the first of May the plant is often in full bloom and is the most conspicuous member of the vternal aspect which lasts until about June 1st. After this the whole aerial part dries up, but the dead leaves are conspicuous throughout the year. Twenty-five root-systems were excavated and examined. Balsamorhiza has a tap root sometimes reaching a diameter of 4 inches and an extreme depth of 8 feet and 10 inches. The laterals seldom come off in the first 6 inches of soil, but below this numerous strong laterals occur, sometimes 1 inch or more in diameter, and these often run rather horizontally for 2 or 3 feet before they turn downward. They may ultimately reach depths of 5 feet or more. The lateral branching is profuse, and in all directions the soil is laid hold upon. Sometimes the tap splits up into nearly equal parts at a depth of a few feet. The tip of the tap root is often dead, and, if alive, never much branched. Small branch orders near the tip are not abundant. The older THE PLANT WORLD, VOL. 18, NO. 10, 1915 278 JOHN ERNST WEAVER part of the root especially is covered with a deeply furrowed bark. These furrows in old roots are sometimes 0.5 inch deep. The taste is characteristic, and a balsam-like substance exudes from the old roots when injured. Five feet and 6.1 inches was determined as the average root depth. Nine plants on a south- west slope gave an average depth of 5 feet and 1 .5 inches; fourteen on a northwest slope, 5 feet and 9.8 inches, and two on a north- east slope, 5 feet. ^*%fo Fig. 12. Two roots of Balsamorhiza sagittata partially uncovered and photo- graphed in place. Note the deeply furrowed bark andextensive system of laterals. Geranium viscosissimum {Geranium incisum) {Fig. 13) Just as Balsamorhiza is characteristic of dry slopes, so Geranium is found most abundantly on moist northeast hillsides and in the valleys. It seldom occurs abundantly on exposed hillsides. Geranium is a large plant reaching a height of from 20 to 30 PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 279 inches, with a wide spreading top which often covers an area of 4 to 5 square feet. It begins blossoming in late May or early- June, and its large red flowers (sometimes as many as 80 to 100 in bloom at one time on a single plant) are conspicuous in the estival aspect especially of moist situations. By the second week in July blossoming ceases, but the plant often remains green till late into the summer, if not all fall. Geranium has a well-developed tap root which may reach three inches in diameter. It is often more or less decayed and may split up into two or more parts, thus giving rise to new plants. The tap sends off many laterals both large and small at all levels, all of which may branch profusely to the fifth order. The larger laterals usually run off in a horizontal direction, some- times for nearly 3 feet before turning downward. The end of the tap root is either unbranched or branched but little, and is often dead. The bark is reddish and scaly on the older parts. Hard soil seems to be a marked limiting factor to root growth, and under this condition especially the usual very irregular course of descent is greatly emphasized. Twenty-four root-systems were examined. The greatest root depth, 9 feet and 6 inches, was reached on a northwest slope, and an average depth of 5 feet and 3.4 inches was determined. Thirteen plants on a northeast slope gave an average root depth of 4 feet and 8.1 inches,while eleven on a northwest slope reached an average depth of 6 feet and 0.2 inch. Wyeihia amplexicaulis (Fig. 14) The black sunflower, at home in the moist meadows, also often occurs on rather dry hillsides. Like Balsamorhiza, it is large and abundant and of considerable duration, being conspicuous even after drying out, but, unlike it, its distribution on the high prairies is local and patchy. When we recall that a single plant may have from 14 to 31 leaves, each from 3 to 5 inches in greatest diameter and from 13 to 17 inches in length, the enor- mous transpiring surface may be realized. This shiny, resinous, dark green plant blossoms during the last week of May or the first week of June and rapidly dries up in early July. The 280 JOHN ERNST WEAVER numerous large yellow flowers 2.5-3 inches in diameter make these societies very conspicuous. The fleshy tap root sometimes measures 9 inches in circum- ference and may reach a depth of 6 feet and 5 inches. It usually has several strong laterals which come off from 8 inches to 3 feet in depth, and may run out in a somewhat horizontal direction Fig. 13. Fig. 14. Fig. 13. Geranium viscosissimum. The crown is partly decayed. The roots are so brittle that they are removed from the soil with extreme difficulty. Five hours were spent in securing the above specimen. Fig. 14. Two roots of the black sunfl6wer, Wyethia amplexicaulis. Note the numerous short laterals. for 3 or 4 feet from the main root. Sometimes, however, only a single lateral occurs. Often at a depth of 1-3 feet the whole tap breaks up into 2-5 nearly equal parts which pursue a downward course, or later extend out as laterals. Primary laterals are not much branched. The whole root from crown to near the tip is covered with scattered small laterals usually not over 2 milli- PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 281 meters in diameter. These are poorly branched, not often giving off roots of the fourth order. The tip of the main root likewise is little branched. The roots are black externally, grayish inside, have a characteristic odor, and dry out and shrink rapidly upon removal from the soil. Eighteen plants on a northeast slope were examined. They had an average root depth of 5 feet and 0.4 inch. Heuchera glabella This plant, so characteristic of the rim-rock crevices especially on the more moist exposures, also occurs rather frequently (often 2 or 3 per square meter) on moist slopes in the prairie. The tufted radical leaves mostly remain green all winter. It belongs to the estival aspect. An examination of seven plants gave an average root depth of 5 feet and 1.4 inches. One root reached a depth of 5 feet and 11 inches. The strong tap is triangular in section near the top and often retains this shape to a depth of 2 feet. The laterals, which are quite numerous, usually come off in the first foot of soil. The root-system as a whole is poorly branched, even the root tips are poorly supplied with branches. Leptotaenia multifida This large, much branched, umbelliferous plant occurs quite commonly on both dry and moist hillsides. The great ternately decompound, pinnatifid leaves, together with the main stems which stand up well above other prairie vegetation, are very conspicuous even when the plants are not abundant, and especi- ally so in June, when after flowering, the leaves turn yellow be- fore drying up. Fourteen root-systems were examined, mainly incidentally while excavating other roots. These large fleshy roots are some- times 7 inches in circumference and may reach a depth of 5 feet and 7 inches. The fusiform roots may narrow down gradually or rather abruptly, even to a diameter of one or two millimeters and then again enlarge at a greater depth to a size equalling the original. This is sometimes repeated several times, thus giving 282 JOHN ERNST WEAVER the root as a whole a beaded appearance. In general the roots are very poorly branched. Ten plants on a northwest slope gave an average depth of 3 feet and 11.3 inches, while five on a northeast slope reached an average depth of 4 feet and 6.7 inches, thus giving a total average root depth of 4 feet and 0.7 inch. Helianthella douglasii {Fig. 15) This and the following composite are both important and abundant prairie species. They occur typically on dry hill- sides, often as many as 2-8 per square meter. While Helian- thella adds much to the estival prairie aspect, with its large yellow flowers, its blossoming period is well past when Hoorebekia racemosa comes into bloom in late July. The latter is one of the few species giving tone to a poorly defined autumnal aspect. Helianthella has a tap root with a diameter seldom more than 0.8 inch. It throws out many big laterals just beneath the sur- face, most of which come off within the first 18 inches of soil, although there are some lower, and a cone may be formed all the way to the tip. The laterals usually pursue rather a vertically downward course, and are profusely branched. Helianthella branches more at the tip than does Hoorebekia, and it also throws out more laterals than that species. The roots are reddish- brown in color, those of Hoorebekia are white. They have a strong, characteristic odor, and an oily taste slightly resembling carrots. By these characters it is easy to distinguish Helian- thella roots from others. Twenty plants were examined. An average depth of 4 feet and 4.5 inches was found; the deepest- rooted plant exceeding this by only 12.5 inches. Six plants on a southwest slope gave an average root depth of 4 feet and 4 inches; five on a northeast slope 4 feet and 8.6 inches; and ten on a northwest slope 4 feet and 7.1 inches. Hoorebekia (Aplopappus) racemosa (Fig. 16) Thirty-four plants were examined. The deepest roots reached 7 feet and 7 inches, and 11 feet respectively, but the average depth was 5 feet and 5 inches , Hoorebekia has a strong tap root PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 283 which tapers gradually to the end. The larger laterals (if any) are often thrown off within the first 18 inches of soil. These are branched to the third order, and may run off in a rather hori- zontal direction. The tap grows directly downward and is sparingly branched all the way to and at the tip. The main root is not usually more than 0.5 inch in diameter. It changes in color from light yellowish near the surface to nearly white below three feet. It has a sharp bitter taste and lacks the odor so characteristic of Helianthella roots. Twelve roots on a north- east slope averaged 5 feet and 3.4 inches in depth; twelve on a southwest slope 5 feet and 4 inches; and ten on a northwest slope 5 feet and 8.2 inches. Lithospermum ruderale These plants occur as isolated individuals, but their large size, densely tufted leaves, and numerous if not showy flowers, make them conspicuous objects in the bunchgrass association of the rim-rock as well as in the prairie. Five root-systems were examined. The large tap roots, from 3 to 10 inches in circumference, give promise of deeper root- systems than are actually attained. Only one plant reached a depth of 6 feet and 3 inches, and the average depth was only 4 feet and 10.3 inches. Large laterals were sent off from the main root at various depths from 1 to 2 feet. These ran hori- zontally several feet before turning downward. One main root curved and twisted a great deal finally ending 3 feet northwest of the place where it started. The tip of the largest root examined had decayed. These roots have a very thick cortex, which sepa- rates easily from the stele. The outer part of the cortex is bright reddish especially on the parts below 1 foot. The old root bark is shreddy and gray, but firm. A peculiar taste and odor characterize these roots. Two p'ants on a northwest slope each reached a depth 16 inches greater than any examined on north or south slopes. 284 JOHN ERNST WEAVER Sieversia ciliata The soft hairy, tufted, radical leaves of Sieversia often remain green throughout the winter. The simple erect stems reach a height of 12-18 inches and bear their blossoms in late May or early June, while in late July or the first of August the aerial Fig. 15. Fig. 16. Fig. 15. Root-system of Helianthella douglasii. It may be noted that the tap root was decayed. Fig. 16. Hoorebekia racemosa. This specimen had no large laterals. plant parts largely dry up. This is a common, abundant, and cosmopolitan prairie species. Few roots of Sieversia penetrate beyond depths of 5 feet and 6 inches. It sends out as many as 20-30 roots from a single inch of its thick rootstock. None of these roots are over 3-4 millimeters in diameter. They pursue a vertically downward PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 285 course and branch profusely all the way to the tip, sending off laterals seldom over 3 inches long but branched to the fifth order. The roots are jet black. Eleven plants were examined on a northeast slope and an average root depth of 4 feet and 8.6 inches was determined. Sidalcea or eg ana This mallow is confined to north hillsides and low ground. While much less abundant than Geranium viscosissimum , it is similar in habit in exposing a great number of large leaves. This plant may reach a height of over 3 feet. It blossoms later than Geranium but like it retains green foliage until frost. Only two root-systems were examined. In both numerous strong laterals were thrown off within 4 inches of the surface. At 24 inches the tap broke up into three nearly equal parts, the largest and longest part reaching a depth of only 3 feet and 1 inch. The other plant reached a depth of 4 feet and 1 inch. Sidalcea roots cannot easily be confused with others for they send off small laterals in groups ranging from 3 to 8 in a group. This is most pronounced in the older parts of the roots. Often where a big lateral comes off one or more little ones originate with it. These groups of small laterals are usually less than 2 inches in length. Hier actum scouleri (Fig. 17) The Hawkweed, with its densely hairy clusters of basal leaves, and its similarly leaden colored cauline leaves and stems reaches a height of about two feet. The rather small yellow flowers appear late in June and blossoming continues until August, even after the basal leaves have dried and turned brown. It is an important prairie species. Twenty-six root-systems were examined. They gave an average depth of 5 feet and 4.3 inches. Hieracium sends out numerous roots, — as many as 50 from a single inch of its corymb — which in turn is from 8-12 inches long. None of these roots are over 3 millimeters in diameter. They pursue a nearly 286 JOHN ERNST WEAVER vertically downward course and throw off practically no laterals, except when they enter earthworm holes. Here, strong laterals equaling the main root in diameter, are thrown off and run parallel with it in the hole a foot or two or further. All give rise to abundant root hairs and it is seldom that these roots again enter the soil. The main root may branch very profusely or very little (in hard soil) at the tip. These light-cream-colored roots are very brittle but are easy to follow because of their latex. The acrid taste also is very characteristic and this character was sometimes used to distinguish Hieracium roots, especially near the tip where the latex is less abundant. The longest root reached a depth of 7 feet and 9 inches. Fifteen plants on a northeast slope gave an average depth of 5 feet and 2.8 inches; five on a southwest slope 5 feet and 3.4 inches; and six on a north- west slope 5 feet and 8.8 inches. Potentilla blaschkeana This very common prairie plant occurs in all situations, but shows a decided preference for the more moist conditions. A few new leaves may appear in the fall, but the plant starts re- newed growth early in April. It blossoms in late May and dries out during July or August, depending upon the environmental conditions. The tufted stems are borne on a short, thick crown from which several (2-5) main roots originate. These average about 7 millimeters in diameter. They taper off gradually till at about two feet in depth they are often only 2 millimeters in diameter. Here they usually branch dichotomously, and again branching break up into numerous small roots — mere hairs — which have a strong tendency to grow in earthworm holes. These they follow for two feet, perhaps, before entering the soil again. In these holes they give off many threadlike branches which follow down the same hole branching profusely, and often never re-entering the soil. The roots are dark brown in color. They are unbranched or very poorly branched at the tip. Thirty root-systems were examined. Three of the longest roots pene- PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 287 trated to depths of 6 feet and 9 inches; 7 feet and 5 inches; and 7 feet and 5 inches respectively. The average depth was found to be 5 feet and 1.8 inches. Twelve plants on a northeast slope gave an average root depth of 4 feet and 11.2 inches, while 17 on a northwest slope reached an average depth of 5 feet and 4.3 inches. Fig. 17 Fig. 18 Fig. 17. This shows the numerous roots sent out from the corymb of Hieracium scouleri. The total length of only one root is shown. Fig. 18. Eriogonum heracleoides from the rim-rock. A single branch of the large mat is shown just above the meter stick. Note the adventitious roots. Only a small part of the complete root-system is shown in the figure. • Eriogonum heracleoides (Fig. 18) This plant seldom occurs except on the very driest ridges of high basaltic prairies, but is a very important ecological species upon the rim-rock and in the bunchgrass association. The great mats often cover an area of 2-3.5 square feet and the prostrate branches with their adventitious roots serve both to 288 JOHN ERNST WEAVER anchor the plant in place and lay hold upon the moisture of the superficial soil layers. It is a notable fact that the Eriogonums (including E. compositum and E. niveum) blossom and appear to thrive when most other plants of the rim-rock have long since dried out. This is explained in part by their extensive root- systems, of which the one shown in the figure will be described. A few others were excavated as checks. The strong, woody, tap root 1 inch in diameter broke up at a depth of 6 inches into seven nearly equal laterals; only about one-fourth of the old tap root is shown in the figure. One of these laterals extended a distance of 13 feet and 6 inches as measured in a direct line from the plant, but had an actual length of 14 feet and 3.6 inches. It tapered off gradually, throwing off both large and small laterals which branched to the fifth order. Upon leaving the main tap it ran along in very shallow soil for 7 feet and 6 inches before turning down in the rock crevices, where it followed a very devious route dipping up and down more than a foot, and branching profusely to the tip. Some examinations were also made of the roots of Rosa nut- kana, and Symphoricarpos racemosus, both very common in nearly all prairie situations. They were found extending to depths of from 6 to over 8 feet. Iris missouriensis roots pene- trated the soils of dry hillsides to 3 feet and 10 inches, and Ber- beris repens to a depth of over 10 feet. The orange-yellow roots of the latter, arising from the great system of horizontal stems on the rim-rock (where it often forms societies), resemble Eriogonum heracleoides in their abundant laterals and in the devious route they pursue in following the basaltic crevices. Likewise, two species of Lomatium,L. grayi andL. inacrocarpum, both abundant on thin soils, were examined. The long, fleshy, poorly branched taps are usually flattened, folded, and twisted as they crowd into the narrow crevices of the rock to depths of 3 to 5 feet or more. On the other hand, Polygonum majus, growing with Poa on thin stony soil, has a shallow but well de- veloped root-system. The tap, seldom over 6.5 inches long (and usually less), sends off laterals profusely. In spite of the PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 289 small leaf surface of this knot-grass, it has always been a puzzle to the writer how the plant could keep alive and even thrive and blossom abundantly from July to October upon the parched soils of the rim-rock. DISCUSSION AND CONCLUSIONS The most obvious result of a consideration of these data is the fact that the response of the plant to these severe environmental conditions is met by well-developed and extensive root-systems. For just as the evaporating power of the air and the nature of the transpiring organs determine the water-requirements of plants, likewise the soil water and the nature of root-systems determine the water supply. It is interesting to note, however, that while the condition of light summer rainfall is quite un- favorable for shallow-rooted grasses, still three of the most important prairie grasses are shallow-rooted. Of these Poa sandbergii is the first to appear on the thin soils of the rim-rock and scab-land, where the underlying rock is little broken. In the prairie it is an important interstitial plant. It is only in the deep soils of the prairies that the shallow-rooted Koeleria cristata and Festuca ovina ingrata play their important role. The water- retaining capacity of the soils certainly favors these shallow- rooted species. On the other hand, the deep-rooted Agropyron spicatum early assumes importance as a crevice plant where sufficient cleaving of the rock has occurred. Indeed, from then on it becomes dominant in the bunchgrass association, where the soils of only a few inches depth overlie more or less decom- posed basalt. In the prairie it is one of the facies, but under the new substratum conditions it partly abandons the bunch habit and may become more or less of a sod former. However, a discussion of the relation of root-systems to succession had best be considered at another time. While the purpose of this study was not to arrive at a classi- fication of root-systems, it is instructive to note that according to the types of root-systems as set forth by Cannon,8 all the roots 8 Cannon, W. A. The Hoot Habits of Desert Plants, Carnegie Inst. Wash. Publ. 131. P. 87, 1911. See also Von Alten, Hermann, Wurzel-studien. Bot. Zeit. 67: 175-200, 1909. LIBRA V- 290 JOHN ERNST WEAVER here described (with the possible exception of Leptotaenia multi • fida) fall under the generalized class. By a generalized root- system is meant one that has both the tap and the laterals well developed. They penetrate deeply and reach out widely. In contrast, the specialized root-system has either the tap root as the chief feature, or the laterals are placed near the surface, and especially well developed, as in cacti. The generalized type of root is much more plastic and consequently reacts to a wider range of conditions than does the specialized type. In considering the question of the susceptibility of roots to modification through variation in the soil texture or its water content, as against the conservative inheritance tendencies, table 6 is instructive. TABLE 6 Average root depths of plants on different slopes Lupinus ornatus Lithospermum ruderale. . Potentilla blaschkeana. . Geranium viscosissimum Hoorebekia racemosa. . . . Hieracium scouleri Helianthella douglasii. . Balsamorhiza sagittata. . Leptotaenia multi fida. . . , Agropyron spicatum S. W. SLOPE i7iches 72.1 64.0 62. S 52.0 61.5 N. E. SLOPE inches 71.0 48.7 59.2 56.1 63.4 63.4 55.6 54.7 49.6 N. W. SLOPE inches 128.4 74.5 64.3 72 68 66 55 69.8 47.3 38.6 It appears that the root lengths on northeast and southwest slopes are about the same and that the marked environmental differences play little part in determining root depth. However, the writer is of the opinion that the hard soil on dry southwest slopes is a limiting factor to root growth. When we note the greater root development on the northwest slope, which, as has already been pointed out, combines a porous moist soil with rather extreme xerophytic above-ground conditions, this con- clusion would seem to be warranted, although the evidence of Leptotaenia and Agropyron is to the contrary. But more data, PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 291 both experimental and from field observations, are needed in this and other regions before this question can be answered. The illogical neglect of most ecologists in not working in this interest- ing field is to be deplored. However, we must not overlook the fact that the real solution of the problem of adaptation to environ- ment will be solved only when the extent and character of both absorbing and transpiring parts of plants are studied and cor- related. The writer has under way an investigation of the ecological anatomy of the leaves of the plants mentioned in this paper, together with the extent of the transpiring surface. Cannon (loc.cit.) points out that for desert plants having gener- alized root-systems it is probable that the penetration of the roots, the character of the soil permitting, is equal to the penetration of rains; also that "the generalized roots are often extremely variable, ranging from a pronounced tap root to a marked develop- ment of laterals, dependent upon soil characters and water relations." No such marked changes as these were discovered, although since the variation in the branching habit is a matter of degree rather than kind, it would be difficult to express the differences in exact terms if indeed these differences had been noticeable. However, the roots of several species showed a marked increase in their output of branches upon leaving the compact soil and entering earthworm burrows. In practically all cases the root tips under such conditions were alive and at least well covered with root hairs, while in the more compacted soils of dry slopes especially, the root tips were often dead and decayed. The cause of these differences is yet to be determined. The differences may be due to the mechanical resistance offered by the soils, or to changed conditions of aeration, or perhaps to both factors acting together. These findings of great root depths, correlated with deep soil moisture, bear out Cannon's suggestion of the probability that the longest or the most deeply penetrating roots are found, not in deserts, but where there is considerable rainfall, and where the penetration of rain is considerable and the water table relatively deep. It may be noted here, by way of comparison, that Andro- pogon scoparius at Manhattan, Kansas, penetrates the soil to 2<)2 JOHN ERNST WEAVER 6 or 8 feet,9 while Ten Eyck has shown that at the same station Andropogon furcatus reaches depths of 4.5-6.5 feet.10 Likewise, Shantz11 in his extensive studies on the Great Plains, has shown that the Prairie grass formation (characterized by the deep- rooted Andropogon scoparius, A. halli, Psoralea tenuiflora, Redfieldia flexuosa and others) is limited in its western extension by insufficient (deep) water supply, and is replaced by the shal- low-rooted short grass formation. The roots studied are remarkable for their individuality. The roots of each species, because of peculiarities of form, of branch- ing habit, of position in the soil, of texture, color, odor or taste, can easily be distinguished, and these distinguishing characters have often proved useful in ecological work. A knowledge of the distribution and extent of root-systems helps us to more coreectly interpret the present structure of vegetation as well as to analyze the causes which have led up to and are constantly active in modifying these conditions. In concluding, I wish to acknowledge my deep indebtedness to my onetime student, Mr. Walter L. C. Muenscher, whose keen interest in the work made him my almost constant com- panion in the course of this study. 9 Georgeson, C. C. and Payne, J. E., Bui. 75 Kans. Agric. Col., 1897. 10 Ten Eyck, A. M., Bui. 127 Kans. Agric. Col., 1904. 11 Shantz, H. L., Natural Vegetation as an Indicator of the Capabilities of Land for Crop Production in The Great Plains Area. Bui. 201 Bureau of Plant Industry, 1911. BOOKS AND CURRENT LITERATURE Western Wild Flowers. — Many persons are attracted by the wild flowers which they encounter in their excursions, but do not desire in the least to take up the study of botany. They are, indeed, re- pelled by the manuals which lock up a knowledge of the floras of their several regions, and are unwilling to attempt to master the keys pro- vided to open it to them. For the convenience of these flower-lovers many guides of a less technical character have been provided, especially in recent years, in which the study of nature has received so great an impulse. They vary in value as in scope, and botanists should be glad to find one they can recommend to those who inquire for something they can understand. Such a book is Miss Armstrong's Western Wild Flowers, whose botanical correctness is guaranteed by the collabora- tion of Professor Thornber.1 The numerous illustrations, in black and white and in color, will be of great assistance to those for whom the book is designed. Its field includes the seven western states from Washington and Idaho to Utah and Arizona, so that the large number of plants described are of necessity but a small part of the flora of that vast and varied region. But the purpose seems to have been to include plants which, by the beauty or unusual structure of their flowers, as well as by their occurrence in places readily visited, are most likely to attract the attention of those who will use the book, and at the same time to present representatives of the various families found in the region covered. Most books of this kind omit all the difficult genera, but in this one only the grasses and the sedges are unincluded. On the whole the selection is judicious, although one is surprised at the absence of some species and at the inclusion of others; but this would certainly be the case whoever made the choice. — S. B. Parish. 1 Armstrong, Margaret, Field Book of Western Wild Flowers. In collabora- tion with J. J. Thornber, A.M. Figs. 500, pis. in color 48. New York, G. P. Putnam's Sons, 1915 ($2.00). 293 THE PLANT WORLD, VOL. IS, Xo. 10, 19l5 NOTES AND COMMENT The recent mention in these pages of the papers on plant distribu- tion which were read at the San Francisco meeting of the American Association has caused one of our correspondents to send us the titles of papers on the same subject which were read in two symposiums held twenty-five and fifteen years ago respectively. The first of these was at the Indianapolis meeting of the American Association in 1890, the second at the New York meeting in 1900. The titles of these con- tributions are worthy of republication at the present time, as they afford an index of the major interests in American plant geography during a period of ten years or more. Papers read at the Indianapolis Meeting: Sereno Watson. The relation of the Mexican flora to that of the United States. John M. Coulter. Geographical distribution of North American Umbelliferae. Lucien M. Underwood. The distribution of Hepaticae of North America. Byron D. Halsted. The migration of weeds. W. J. Beal. Geographical distribution of the grasses of North America. John M. Coulter. Geographical distribution of North American Cornaceae. N. L. Britton. On the general geographical distribution of North American plants. Papers read at the New York Meeting: B. L. Robinson. Distribution of the Spermatophytes in New England. J. K. Small. Distribution of the Spermatophyta in the southeastern United States. Thomas H. Kearney. Notes on the Lower Austral element in the flora of the southern Appalachian region. H. C. Cowles. Physiographic ecology of northern Michigan. Roscoe Pound. Vegetative elements of the sandhill region. P. A. Rydberg. Composition of the Rocky Mountain flora. C. V. Piper. Flora of the Columbian lavas. G. V. Nash. Distribution of the grasses of North America. W. L. Bray. Relationship between the North and South American floras. J. N. Rose. Floral zones of Mexico. N. L. Britton. Origin of the flora of North America. The majority of the participants in these symposiums are best known through their work in systematic botany, a circumstance which calls 294 NOTES AND COMMENT 295 attention to the fact that during the past decade there have been very- few contributions to plant geography from the systematic botanists of this country. This may be due to the absorbing task which has busied all taxonomic workers in the description of fresh material from little-known regions, or in altering the names of plants from well- known regions, or it may be due to the inherent difficulty of arriving at fresh generalizations in phytogeographic work. Such recent papers as those of Dr. N. L. Britton on the vegetation of Mona Island and of Dr. P. A. Rydberg on the alpine flora of the Rocky Mountains show that phytogeography still makes a strong appeal to the systematist whenever he contemplates the larger features of his work. It is to the systematist that we must look for our soundest work in floristic plant geography, and it is greatly to be hoped that he will not neglect this opportunity for the widening of his work. Miss Josephine E. Tilden, of the University of Minnesota, announces that she is now prepared to distribute 6000 cards of her Index Algarum Universalis. This Index furnishes a complete bibliography of litera- ture on algae, under the four headings: authors, genera and species, geographical areas, and general subjects. It is Miss Tilden's aim to bring the Index up to date during 1916, and thereafter to keep it abreast of the current literature. We wish to remind our readers of the two prizes of $50 and $15 which are offered by this journal for the best papers on the water relations of plants. All papers submitted in competition should be in the hands of the Editor by December 1, 1915. Fuller information regarding the contest may be found in the April issue. AN INVESTIGATION OF THE CAUSES OF AUTONOMIC MOVEMENTS IN SUCCULENT PLANTS EDITH BELLAMY SHREVE Tucson, Arizona I. The stucty of autonomic movements in plants has attracted the attention of many notable workers throughout several decades, but as yet very few have been able to attain an ap- proach to the goal of ultimate causation. Various kinds of move- ments have received attention and their causes have been ascribed to such things as changes in geotropic irritability, differential growth, changes in the turgidity of special organs, caused in turn by changes in permeability of protoplasm, to temperature, to light, etc. ; but the causes of the changes in geotropic irritability (whatever the term may mean), of differential growth, of per- meability changes, or the mechanism by which light and tem- perature act, have not been found. There have come to the attention of the writer no papers dealing with autonomic move- ments in succulents and it seemed probable that a study of move- ments in this class of plants might bring to light new facts which would in the end aid in the discovery of the ultimate physico- chemical causes for at least one class of movements. In the following report new facts regarding movements do appear and their causes are traced to a physical source but this source is, alas, still far from the ultimate cause. This paper will, however, be followed at an early date by another which will contain the results of a further research into the mechanism of the physical source mentioned above. In the present paper the usual terms "irritability," "internal stimulus," "response" have been avoided because in the opinion of the writer they mere- 297 THE PLANT WORLD, VOL. 18, NO. 11, 1915 298 EDITH BELLAMY SHREVE ly mask the true condition of the state of knowledge of cause and effect. The investigations set forth in the following pages were car- ried on at the Desert Laboratory at Tucson, Arizona. The writer wishes to express, here her gratitude to Dr. D. T. Mac- Dougal not only for the use of the facilities of the laboratory but also for helpful suggestions concerning the work. Autonomic movements of an etiolated joint of a platyopuntia were described by MacDougal in 1910, * and in 19122 he observed an attenuated plantlet of Opuntia versicolor, that within a period of three days showed movement in a vertical direction through an arc of 180° and in a horizontal direction through an arc of 2 to 10°. During the last few years the writer has at various times observed that joints or limbs of Opuntia versicolor, O.fusi- caulis, 0. Toumeyi, and Carnegiea gigantea have changed their positions from time to time. The work presented here was undertaken with a view to finding the exact nature of these movements and the cause of them. Opuntia versicolor was chosen as the subject of the main part of the investigation on account of the convenience of procuring large numbers of individuals. This is a much-branched, semi-arborescent cactus, made up of joints 1 to 4 cm. in diameter and 5 to 30 cm. in length. The younger plants, 1 to 10 years old, have joints in all respects like those of the same age on older plants. The plants used as material for the observations and experi- ments retain the same designation by number or by letter throughout the paper. They fall into three classes: (1) Nos. 1, 2, and 14, which were raised from seed in a green-house and were 4 years old when used; their joints were more attenuated than is usual with plants grown in the open but they were plump and turgid. (2) Nos. 3 to 34 inclusive, excepting 14, which were taken from the ground three months to a year before they were used and were planted in pots. (3) Nos. A to G which were growing in the open and left undisturbed. 1 MacDougal, D. T., and Cannon, W. A., The conditions of parasitism in plants. Carnegie Inst. Wash., 1910. 2 From unpublished notes kindly furnished the writer by Dr. MacDougal. AUTONOMIC MOVEMENTS IN SUCCULENTS 299 Casual observations made it seem probable that the various positions assumed by the joints were related to the degree of turgidity of the tissues. Hence measurements were made on plants in wet and in dry soil. In potted plants the soil water- content could, of course, be controlled. The measurements on plants growing in the open were made at various times of the year when the interval between rains was known. The first set of observations was made on both potted plants and on plants growing out of doors. The differences in posi- TABLE 1 The relation of movements of joints of 0 punt i a to the water-content of the soil. Plant No. 2 Oct. 2 to 17 Oct. 17 to 22 A B c -19.1 -3.5 -8.3 + 14.6 +3.4 +7.5 No water given between the dates. Pot open. Watered every two days after Oct. 17 Plant No. 3 May 27 to Aug 7 Aug. 7 to 11 A B -5.2 -1.0 +5.4 +0.6 No water given between dates. Pot sealed. Watered on Aug. 7 Plants Nos. 7 and S Oct. 22 to Jan. 21 Jan. 21 to Mar. 20 no. 7A NO. 8 -20.8 + 20.3 -24.0 +23.7 No water given between dates. Pots sealed. Watered frequently after Jan. 21. Plants A and C Al A2 A3 Cl Oct. 22 to Dec. 2 Dec. 2 to Mar. 20 — 5.5 +5.5 -4.5 +4.7 -2.5 +3.7 -13.0 + 11.0 No rain between dates Many showers after Jan. 21 noo EDITH BELLAMY SHREVE tion which took place during the intervals between measurements are given, in centimeters, in table 1, the plus sign being used to denote an upward movement and the minus, a downward one. The general appearance of the plants under the several con- ditions is indicated by the diagrams in figure 1. These show only the extreme positions assumed in wet and in dry soil. The downward movement took place gradual^, occupying weeks or months, while the upward movement was rapid after rain or irrigation and occupied only a few days. A Oct. 2 Oct. 17 Oct22 Oct.22 Dcc.2 Mar 20 ^3 Oct.22 Jan.21 Mar.20 Oct 22 Dec 2 Mar. 20 Fig. 1. Diagrams to illustrate the relations of movements of Opuntia versi- color to the water-content of the soil. For details see table 1. The second set of observations was made by means of measure- ments and by securing series of photographs. Negatives were made of five adult plants, growing in the open, at successive seasonal periods of wet, dry, and wet soil, the camera being accurately placed in the same position each time. All five of the plants showed similar behavior. In figure 2 appear views of the smallest plant of the series. Both of the above sets of observations show that when the positions are noted at the same time each day, they change with the amount of water in the soil, a low position being assumed ■„ • CD o — _= ^ bC -ta r ~~ u_ . _ O _r: "3 ' ■— ' - CO fl s-l «4-l CD u O O — -4-3 A bfl — 13 +3 -4-" -4>a rl 08 — O o o co »— i / M C5 CD ^H +3 o •ta C3 © _C3 ' ~* . CD - CO Sh ej _C ■n ~ 'S g 0 Sh X Sh CD Q ^ s fl a & ~ r o CO •—i — CD >> C -fa CD co «4-H > & O • —t ~ CD o CO t*-H CO o O t4-t o co o a -*a o CD a CO a3 CD c^ -f3 -f3 CD rH co CD S CD +3 CD CD Sh 03 Sh CD -4-3 -fa ri 03 c3 — I Oi 7-H £ o ?r T3 a CM O o • ~* ■ pj Sh Sh CO CD CD ^> _2 a Si - -fa >i C3 O Sh '■C c T3 3 a. a — ^ £ 73 j— i o O Ph +a Sh CD CO CO X! a -fa CN CO H CD Sh CD ':'( M CD Sh CD -fa a CD > O 0 a pq .301 302 EDITH BELLAMY SHREVE during progressive desiccation and a higher one after subse- quent rain or irrigation. When the plants are in dry soil their tissues are shrunken and have distinct ridges and furrows around the tubercles. After rain or irrigation, as well as before any desiccation has occurred, the joints are plump and have many signs of being more turgid than when in the desiccated condition. A test of the water- content of joints one year old gave 18 grams of water per gram of dry weight for joints in the high position and 10 grams for the low one. These values were obtained by heating severed joints to constant weight at 100°C. Ten separate determinations were made and the results averaged. The individual varia- tions were sometimes as great as 20%. It is evident that the movements thus far considered are due to changes in turgidity. Measurements were also made on Carnegiea gigantea, and on Opuntia fusicaulis, which show that they have similar movements. Frequently joints continue the growth of their vascular tissue while they are in the low positions and when the rains come they are too stiff to return to their former erect positions. Thus the curious final forms of the cacti are determined by the amount of drought the plants experience during the last stages of the secondary thickening of the joints and not by any peculiarity of the growing points. When soil conditions remain fairly constant no observable change of position takes place, provided the measurements are made at the same time each day. However, when measurements are made at 2 to 12 hour intervals another phenomenon appears which may be said to be superposed upon the nearly constant position in soil of unchanging water-content, as well as upon the general downward or upward motion in soil of decreasing or increasing water-content. This new movement takes place within each 24 hours and may be described briefly, as consist- ing of a downward movement at night and an upward one during the day. Certain exceptions to this general rule occur and will be considered. The character and amount of this motion, together with a general description of the accompanying environmental conditions, will be seen from the following experiments. AUTONOMIC MOVEMENTS IN SUCCULENTS 303 Preliminary experiments, which will not be recorded here, gave some evidence that the short period movements are con- trolled by temperature, light, the water-content of soil and of tissues, both at the time of the experiment and previously, and possibly also by the evaporative power of the air. Conse- quently, movements have been measured under various environ- mental conditions and a record kept of these conditions. In TABLE 2 Experiment 1. Movements of three branches of Plant No. 4 A B C Mar. 8 7.30 a.m. to 7.30 p.m.. . +4.0 -0.4 + 2.4 -1.1 +0.6 +4.3 -3.7 . +4 5 7.30 p.m. to Mar. 9 7.30 a. m 7.30 a.m. to 7.00 p.m TABLE 3 Experiment 2. Movements of Plant No. Mar. 11 9 a.m. to 10 a.m.. 10 a.m. to 11 a.m.. 11 a.m. to 12 noon 12 noon to 4 p.m. 4 p.m. to 7 p.m. 7 p.m. to Mar. 12 7 a.m.. 7 a.m. to 10 a.m.. 10 a.m. to 12 noon 12 noon to 4 p.m. +0.1 +0.1 +0.6 +0.7 0.0 -0.9 +0.5 +0.9 +2.9 experiments 1-6, the normal range of day and night temperatures and light have been used with a variation in the water-content of soil and tissues. In experiment 7, the light and temperature changes are still the normal ones but the plants are exposed to different wind velocities and hence to different evaporative intensities. Experiment 8 covers various conditions of light and temperature changes with the water-content of soil and tis- sues remaining as nearly constant as possible. 304 EDITH BELLAMY SHREVE TABLE 4 Experiment 3. Movements of Plant No. 1, branches A, B and C TIME A B c Mar. 10 7 a.m. to 12 noon + 0.6 + 0.2 -0.5 -1.5 + 0.4 +0.3 +0.3 0.0 0.0 + 0.3 -1.2 0.0 0.0 0.0 0.0 0.0 -0.8 + 0.3 + 0.2 -0.5 -1.3 +0.4 +0.5 CO 0.0 0.0 + 0.2 -1.2 0.0 0.0 0.0 , -0.6 -0.7 + 1.4 +0.4 — 0 8 12 noon to 4 p.m 4 p.m. to 7 p.m.. . 7 p.m. to Mar. 1 1 7 a.m — 1 1 7 a.m. to 8 a.m +0.3 0 0 8 a.m. to 9 a.m 9 a.m. to 11 a.m +0.6 + 0.5 0 0 11 a.m. to 2 p.m 2 p.m. to 4 p.m.. . 4 p.m. to 7 p.m.. + 0.3 — 2 4 7 p.m. to Mar. 12 7 a.m 7 a.m. to 10 a.m. . . -0 5 10 a.m. to 11 a.m 11 a.m. to 12 noon 12 noon to 4 p.m + 0.3 +0.2 0 0 4 p.m. to 7 p.m 0 0 7 p.m. to Mar. 13 7 a.m —2 1 TABLE 5 Experiment 4. Movements of Plants No. 11 and No. 12 PLANT NO. n PLANT NO. 12 Mar. 9 7 a.m. to 7 p.m. + 1.0 Mar. 11 7 p.m. to 7 p.m. to Mar. 12 7 a.m. -0.2 Mar. 10 7 a.m. -0.8 7 a.m. to 10 a.m. + 0.2 7 a.m. to 12 m +0.3 10 a.m. to 12 noon +0.5 12 noon to 4 p.m. +0.2 12 noon to 4 p.m. +0.3 4 p.m. to 7 p.m. 0.0 4 p.m. to 7 p.m. 0.0 7 p.m. to 7 p.m. to Mar. 11 7 a.m. -0.7 Mar. 13 7 a.m. -0.8 7 a.m. to 8 a.m. +0.2 7 a.m. to 10 a.m. +0.5 8 a.m. to 9 a.m. 0.0 10 a.m. to 12 noon +0.4 9 a.m. to 11 a.m. +0.2 12 noon to 11 a.m. to 2 p.m. 0.0 Alar. 14 7 a.m. -0.4 2 p.m. to 4 p.m. + 0.3 4 p.m. to 7 p.m. -0.2 AUTONOMIC MOVEMENTS IN SUCCULENTS 305 Thermograph records were taken, and have been presented in the accompanying figures. An arbitrary and very crude method for indicating changing light conditions has been adopted. A convenient distance was chosen as the height to represent the light conditions in the open when the sky is clear and the sun- light falls directly on the plants; one-half of this amount repre- sents complete cloudiness or the shade within the laboratory. No attempt was made to indicate anything beyond the grossest changes in light intensity, such as are caused by partial or inter- -/ Fig. 3. Movements of Opuntia versicolor under three conditions of water relations. See tables 2-5. Plants Nos. 4, 11, and 12 (solid line) are of normal turgidity throughout the experiment. Soil continuously wet. Plant No. 1 (broken line) is of normal turgidity at the start of the experiment. Soil is dry- ing out. Plant No. 8 (dotted line) is recovering from a previous short desicca- tion period. Soil continuously wet. mittent cloudiness. A clear day is represented by a straight line from sunrise to sunset regardless of the fact that the intensity changes from hour to hour. Experiment 1. March 8-9, 1914. Object: The measurement of day and of night movements of a plant under green-house conditions. Water-content of soil high. 306 EDITH BELLAMY SHREVE Material: Plant No. 4, an individual with two branches grown in the open and three in the green-house. The measurements were made on the branches which grew in the green-house. The soil has been kept continuously moist for over a month. Results: The data are recorded in table 2 and given in graphic form in figure 3. Experiment 2. March 12-13, 1914. Object: The measurement of movements at intervals during the day, with a single measurement for the night, under green-house conditions and with the plant recovering from drought in wet soil. Material: Plant No. 8, an unbranched small individual which made its growth in the open. The previous history of this plant is shown in figure 1. At the time of the experiment it was in position 3. The soil had been kept continuously wet since the watering on January 21 . At 7 p.m. on March 12 a small amount of water was given in order to prevent even a slight drying lut during the night. A small "w" on the graphs always indicates the time at which water was added. Results: Data are given in table 3 and figure 3. Experiment 3. March 10-12, 1914. Object: The measurement of changes in position at frequent intervals, under green-house conditions and in soil which is gradually drying out. Material: Plant No. 3, a three year old, which had spent its entire life in the green-house. It was 50 cm. high and bore three branches. All three branches were in positions intermediate between 1 and 2 in figure. 1. Results: The data are given in table 4 and figure 3. Experiment 4. March 9-11, 1914. Object: The measurement of changes in position at frequent intervals under green-house conditions and in wet soil, using plants which have never suffered from drought. Material: Plants No. 11 and 12. Both were small individuals about 15 cm. high and were in erect positions. They had made their entire growth in the green-house. Results: Data appear in table 5 and figure 3. Experiment 5. Object: The duplication of experiments 1-4. Material: Plants Nos. 1, 2, 4, and 5. Method: Experiments 1-4 were repeated under as nearly identical conditions as could be obtained on different days. Results: The data were in all respects similar to those in the previous experi- ments; so that the graphs of these experiments would, if slightly smoothed, represent the graphs for the movements in experiment 5. Experiment 6. Object: The measurement of movements for day and night under extremely desiccated conditions of soil and plant, and later of movements of the same plants after irrigation. Material: Plants Nos. 3, 4, 7, and 8. All had received no water for two months and the branches were in the lowest possible positions. Results: Measurements extending over two weeks showed no movement either during the day or at night for plants under conditions of extreme desiccation. Measurements during two days and nights immediately after irrigation showed a AUTONOMIC MOVEMENTS IN SUCCULENTS 307 continuous rise for both day and night, but a faster rate for the day than for the night. Plant No. 4 was kept in constant darkness after irrigation and continued to rise during the two days and nights. Its rate was slower than that of the others, but the rates varied so much from plant to plant and from branch to branch that it was impossible to tell what the rate of No. 4 might have been if it had not been kept in darkness. Experiment 7. TABLE 6 Movements under different conditions of evaporating power of the air PLANTS NOTES No. 1 No. 2 No. 8 No. 15 No. 16 Sept. 4 10 a.m. +4.0 + 3.1 +0.8 +0.5 + 0.7 In greenhouse. Sun 2 p.m. +3.5 +2.0 +0.3 +0.1 +0.2 bright. Evaporat- ing power of air low. Sept. 5 10 a.m. -3.2 -1.7 -0.4 +0.3 +0.4 In the open. Sun bright, wind veloc- ity very high. 2 p.m. 0.0 0.0 -0.5 0.0 +0.1 Evaporation extremely high. Sept. 6 10 a.m. -1.0 -0.2 0.0 +0.4 +0.5 In the open. Sun 2 p.m. -0.5 -0.3 0.0 +0.4 +0.3 bright. Wind ve- 3 p.m. 0.0 -0.3 -0.2 +0.1 0.0 locity medium. 4 p.m. Evaporating 6 p.m. -1.5 0.0 0.0 -0.2 0.0 power of the air high. Experiment 7. Object: Measurement of movements under conditions of the high evaporation existing in the open in the sun, with the tissues of the plant turgid and the soil water content high. Material: Plants Nos. 1, 2, 8, 15, and 16. Plants 1 and 2 had spent their entire life in the green-house, the others in the open. Method: All plants were measured at four-hour intervals, on the first day in the green-house, on the second day in the open, under the influence of bright sun and a high wind. On the third day the plants were again placed in the open, but on this day the velocity of the wind was not so high. The plants were placed in the green-house at night. Results: The movements are shown in table 6. Two of the three plants which had grown in the open, Nos. 15, and 16, moved upward both in the green-house 308 EDITH BELLAMY SHREVE and in the open. The two plants which were grown in the green-house moved upward under green-house conditions but downward when placed under the conditions of higher evaporation in the open. Plant No. 8, which had grown in the open, behaved in the same manner as the green-house grown plants. Experiments 1-7 show that young turgid joints which have not recently suffered from drought, when placed under conditions of average evaporative intensity and subjected to the normal day to night changes in light intensity and air temperature, show short periodic movements, consisting of a rise during the Fig. 4. Movements of Opuntia. March 2-4, low temperature with an alter- nation of diffuse light and darkness. March 5-7, high temperature with an alter- nation of diffuse light and darkness. March 8-10, normal clay to night changes in temperature and light. Two lowest graphs indicate temperature and light conditions. See experiment 8. daylight and a drop during darkness hours. The rise is greatest in the forenoon, frequently ceasing, or even being replaced by a drop, after four o'clock. In other words, during the time of greatest evaporative intensity of the day the plant is erecting itself and during the time of lowest evaporation it is drooping. This characteristic movement is influenced by the amount of water in the soil and may be stopped or reversed b}^ allowing the plant to become desiccated and subsequently irrigating. A very high evaporative intensity may also give a downward move- ment during the day to a joint which has grown in the green- house and sometimes to a very young joint which has made its AUTONOMIC MOVEMENTS IN SUCCULENTS 309 growth in the open. The next experiment records the influ- ence of other combinations of environmental factors upon the movement. Experiment 8. Object: An investigation of the influence of light and temperature upon the day and night movements, by means of their measurement under conditions of (1) constant high temperature with an alternation, at twelve hour intervals, of diffuse light and darkness; (2) constant high temperature with an alternation of sunlight and darkness; (3) constant low temperature with an alternation of diffuse light and darkness; (4) constant low temperature and constant darkness; (5) constant darkness with an alternation every twelve hours, of high and low temperatures. For the high temperatures 90° to 100° F. were selected and for the low ones 55° to 60° F., the idea being that these represented the average maximum and minimum to which plants are normally subjected. Thus any metabolic changes which might influence the movements would still appear.3 Material: Plants Nos. 1, 2, 4, and 7. Nos. 1 and 2 were green-house raised plants; Nos. 4 and 7 were from the open. Method: The constant high temperatures were obtained by placing the potted plants within glass cages (about 15 cubic feet capacity) which were fitted with electric heaters and automatic controls. The temperature between the top and bottom of the cages varied from 1° to 1.5° F., while at a given level the variation was no greater than 0.2° F. The thermograph was placed at the mean level of the aerial parts of the plants. For the constant low temperature, a vault beneath the laboratory was used. No means was at hand for obtaining a constant low temperature in sun-light. Unless statements are made to the contrary, the plants used were at nearly maximum turgidity and were in wet soil. Results: The movements are recorded in the form of graphs in figures 4-6. Light and temperature changes are indicated in the same manner as in previous experiments. When the behavior of the plants is examined from the graphs the following facts appear. The characteristic upward and downward movements for day and night cease entirety under conditions of (1) constant high temperature with an alternation every twelve hours of darkness and diffuse light; (2) constant high temperature with an alternation of darkness and sunlight ; (3) nearly constant low temperature with an alternation of dark- 3 It was thought when these conditions were planned that acidity changes within the plant could be predicted from the work of H. M. Richards (Acidity and gas interchange in cacti. Carnegie Inst. Pub. 209), and G. Krause (Die Wasserverteilung in der Pflanze. Abhand. d. Natrfor. Ges. Halle, 16, 143). But later, when acidity determination were made on the material under these con- ditions, the results showed that further work must be done on acidity relations before such predictions can be made with any degree of accuracy. 310 EDITH BELLAMY SHREVE ness and diffuse light; (4) constant low temperature and con- stant darkness. In the case of the continued darkness with an alternation of high and low temperatures, the first twenty-four hours shows the characteristic movements but the second period of low tem- perature fails to show the downward movement and after this, one plant continues a general downward movement, while the other moves upward during exposure to high temperature and downward under the influence of low temperature. PllT-t SO. 7 Kar. 1! Fig. 5. Movements of Opuntia. March 8, normal day to night changes in temperature and light. March 9-11, high temperature with an alternation of diffuse light and darkness. March 12-13, high temperature with an alternation of normal day to night changes in light. Two lowest graphs indicate tempera- ture and light conditions. See experiment 8. All of the plants resumed their characteristic movements when they were again placed under normal conditions, but not until one period of low temperature and darkness had been experienced. Thus it appears that an interruption of the normal day to night changes in temperature and light intensity breaks the sequence of day to night movements. It is evident that both light intensity and temperature influence the movements, but a given light intensity or temperature or any combination of the two will not produce a given movement unless they have AUTONOMIC MOVEMENTS IN SUCCULENTS 311 been preceded by the proper combination of light and tempera- ture. The duration of these conditions is also of importance. For example, an upward movement takes place under conditions of strong light intensity and high temperature, provided the plant has been subjected to a low temperature and darkness for a period immediately preceding. Further, a downward move- ment at low temperature and with weak light intensity takes Plan". So. 4 Plait No. 4 : 6 p.m. 6 Mar. £2. 6 p.m. 6 a. I •' p.m. 6 a.m. 6 p.m. Apr. 1. Fig. 6. Movements of Opuntia. March 20-24, constant darkness with an alternation of low and high temperatures at twelve hour intervals, followed by one day of normal conditions. April 1-4, constant darkness and constant low temperature. Two lowest graphs indicate temperature and light conditions. See experiment 8. place only when these conditions follow high temperature and strong light. These periods need not be as long as twelve hours, as may be seen from the graph on March 11 and 12, when the heating unit failed to work and is so recorded by the thermograph trace. The facts brought out in the last paragraph show that the influence of temperature and light intensity on the movements cannot be a direct one. The temperature and light must exert an influence on some other processes which in turn influence 312 EDITH BELLAMY SHREYE the movements. Quite possibly the movements are either caused by, or controlled by metabolic changes which in their turn are controlled by light and temperature. It is also possible that there are still other intermediate factors. One that forces itself upon the attention is the turgor changes in the tissues. At first it seems absurd that these plant movements could be due to such changes, since the time of lowest turgor would have to come at night, a time when all plants so far as known from previous work, have their greatest turgor. However, it must be noted that all of the changes in environment which have been considered have unavoidably included changes in the evaporative intensity of the air, and therefore in the amount of water lost by trans- piration. Always though, the downward movement occurred when the plant was "logically" losing the least amount of water and an upward one when transpiration was greatest; so that it seems impossible that the plant could have the greatest turgor when the joints are moving upward. ( To be continued) A USEFUL DRAWING CAMERA RICHARD M. HOLM AX University of California, Berkeley, Cal. While studying recently in the Botanical Institute in Leipzig, I had occasion to follow closely the course of the geotropic reac- tion and subsequent autotropic flattening of primary and sec- ondary roots. To record such reactions by means of occasional free hand drawings is highly unsatisfactory because of the una- voidable inaccuracy of such drawings. The method employed by Simon (Untersuchung iiber den autotropischen Ausgleich geotropischen und mechanischen Kriim- mungen der Wurzeln, Jahrb. der wiss, Bot., Bd. 51, S. 81) leaves much to be desired. He placed the zinc boxes with glass side walls, which contained the seedlings, on their sides on the stage of a dissecting microscope and by means of a camera lucida traced the magnified images on paper. In this method the object is subjected, during the time necessary for drawing, to a stimulus acting at right angles to the direction in which it acts during the intervals between drawings. If these intervals are short the curvature of the root may be materially changed and a curva- ture toward the side of the box will make its appearance, par- ticularly if the experiment extend over considerable time. This lateral curvature will occasion inconvenience and probable in- accuracy in drawing the root and may bring it into contact with the side wall of the box. An arrangement by which the roots could be drawn without changing their position relative to gravity would be more satisfactory. Professor Pfeffer suggested to me that a makeshift drawing apparatus, consisting of a camera, once part of a now obsolete photo-micrographic apparatus, the ground glass of which had been replaced by a piece of clear glass and which had been em- ployed by an earlier student in the laboratory, might serve my 313 THE Pi.AXT WOULD, VOL. 18, NO. II, 1915 314 RICHARD M. HOLMAN purpose. A photographic lens of rather short focal length had been employed in this drawing camera and the image had been traced on a piece of almost transparent parchment paper held against the glass plate by means of two pieces of wood wedged into the ground glass frame. I found it very difficult to trace accurately the image because the drawing surface was perpendicular. On that account I de- signed the attachment which is illustrated in the accompanying figures to bring the image into a horizontal plane. It was con- structed by a photographic mechanician in Leipzig and was so made that it could be substituted for the ground glass frame of r \v Fig. 1 . Section through the drawing camera. One-sixth natural size. Expla- nation in the text. the camera by sliding it into the grooves which held the frame in place. The attachment consisted of a wooden box having approximately the form of a right triangular prism, two sides of which were open. One of these open sides was held against the back of the photographic camera. Into the other open side, which was horizontal when the box was in position, a glass plate (g) was fitted. On the inner surface of the hypotenuse side of the box a mirror (m) was fastened which reflected the pencil of light coming from the camera lens upward through the glass plate. A very satisfactory contrivance which I had constructed for stretching the parchment paper over the surface of the glass and A USEFUL DRAWING CAMERA 315 keeping it free from wrinkles was attached to the reflecting box. This consisted of three parts. The roll (w) was made of wood and provided with a slit like a kodak film roll. It was attached by brackets just above the glass plate. The roll (r) consisted of a brass rod provided with a small crank at one end and cov- ered for a length equal to the width of the glass plate with a piece of soft thick walled rubber tubing. This roll was so fas- tened to the frame that the tubing was compressed against the glass plate near its upper edge. The strip (s) of springy brass plate was bent into a flat curve and fastened by two screws at the left of the glass plate and near its lower edge. Over the strip several short pieces of soft rubber tubing were drawn. A Fig. 2. Reflecting box as seen from above, showing arrangement for holding the parchment paper. Explanation in the text. metal tongue attached to the frame at the right made it possible to hold the brass strip against the glass plate. In use the parchment paper cut in strips of proper width and wound on the roll (w) was passed between the roll (r) and the glass plate. The end of the paper was then fastened at the lower end of the plate by means of the strip (s). A few backward turns of the roll (r) stretched the paper smoothly over the glass. The whole apparatus rested upon wooden strips mounted on a laboratory stand the height of which could be adjusted by a crank. By sliding the camera along the strips it was possible to focus the image without changing the distance between the lens and the drawing surface. Thus a constant magnification could be maintained throughout a series. 316 RICHARD M. HOLMAN The range of magnifications was \ X to 2\ X but a conical extension made of sheet brass, which could be substituted for the lens board, so increased the distance of the lens from the surface on which the image was projected that magnifications of from 2\ X to 4 X could be secured when it was used. The tracings obtained with this apparatus made it possible to follow the root curvature very satisfactorily. A piece of wire thrust into the cork on which a seedling was mounted and lying in the same plane as the geotropic curvature was traced each time the root was drawn. The tracing of the wire and of an India ink mark on the root base permitted the drawings of the curving root to be brought into perfect correspondence when they were superimposed. The position of the root relative to gravity was recorded by tracing the image of a plumb line on the first drawing of each series. This camera has proven its usefulness in my own work, in the investigations of two other students at the Leipzig Institute on twining movements and orientation of leaves and in many of the exercises performed by students there, preliminary to the tak- ing up of special problems. Many other uses for such a camera as well as improvements in design, particularly with reference to greater stability of the drawing surface, will suggest themselves to those interested. BOOKS AND CURRENT LITERATURE Xerophily. — The inquiry as to what plants shall be designated xerophytes was made about a year ago by Kamerling1 and has been more recently raised by Miss Delf.2 The latter author has made a very careful answer to the question, showing that xerophytes have been de- fined in turn on habital, anatomical, and physiological evidence. Kamerling attenuated to establish a purely physiological criterion for xerophily, based upon transpiration behavior. He' measured the tran- spiration from severed shoots not supplied with water, a method which possesses the lowest grade of experimental value and could be useful only in the differentiation of an Impatiens and an Opuntia. Miss Delf repudiates the methods of Kamerling, and she furthermore re- jects any attempt to give a purely physiological definition to xerophily. In such rejection she would doubtless include the suggestion of Bakke3 that xerophily be defined in terms of the transpiring power of leaves, as measured by hygrometric paper. "It is clear," states Miss Delf, "that xerophily cannot be adequately defined in terms of habitat, of anatomy, or of physiology alone. It is rather a natural conception in- volving the total reaction of plant to environment." We have used the term "xerophyte" for 93 years and are now attempting to sort out the particular plants which belong in this category. Kamerling re- jected the anatomical claims of Casuarina and Sarothamnus scoparius as xerophytes, and also the claims of mosses and lichens, in spite of their ability to withstand desiccation being greater than that of any flowering plants. Miss Delf's work has led to the removal of the halophytes from their former place among xerophytes. In this time-honored category are still to be found the desert succulents and the desert sclerophylls and microphylls. Enough is already known of the be- havior of the last-named classes of plants to make it highly irrational to class them together from any standpoint except that of a com- 1 Kamerling, Z., Welche Pflanzen sollen wir Xorophyten nennen? Flora, 106: 433-454, 1914. 2 Delf, E. Marion, The Meaning of Xerophily. Jour. Ecol., 3: 110-121, 1915. 3 Bakke, A. L., Studies on the Transpiring Power of Plants as Indicated by the Method of Standardized Hygrometric Paper. Jour. Ecol., 2: 145-173, 1914. See review in this journal, 18: 222-224, August, 1915. 317 318 BOOKS AND CURRENT LITERATURE munity of habitat. The question that should be asked is not "which plants shall we call xerophytes," but "what do we know about the physiological behavior and habital requirements of the plants of arid habitats and of other plants which resemble them." The reviewer ven- tures to predict that as we come to know more about the comparative physiological and ecological behavior of plants — depending less upon inferences based on anatomy — we will have use for the term xerophyte only in extremely general discussions of vegetation. — Forrest Shreve. Plant Life. — A particularly attractive volume for the amateur in natural science has been produced by Mr. Charles A. Hall in his Plant Life.1 A phylogenetic order of treatment embraces the entire range of cryptogamic and phanerogamic plants; and some of the best- known facts of physiology, paleontology and general biology are intro- duced at appropriate places in the scheme. The treatment is charac- terized throughout by an enthusiasm which is calculated to hold the attention, but the author shows no desire to go very deeply into mat- ters of cause and effect, as is evident in the discussion of insectivor- ous plants, transpiration, respiration, and some other subjects. The book is calculated to serve a very useful purpose, but at no time in its perusal will the reader suffer from the mental exertion of following technical details. The illustrations are very numerous, the photo- graphs being excellent and the colored plates the best that have ap- peared in any recent popular botanical work. — Forrest Shreve. 1 Hall, Charles A., Plant Life. Pp. 380, figs. 80, plates 74 (50 in color). Lon- don, A. and C. Black, 1915 ($6.00). NOTES AND COMMENT . At the suggestion of one of our subscribers, and with the encourage- ment of several other persons, The Plant World announces the offering of two prizes for the best papers embodying original work in soil physics. The first prize will be S50 and the second $25, with the reservation of the right to withhold both prizes if no worthy papers are submitted, or to combine the prizes for the rewarding of a paper of exceptional merit. The conditions governing the awrard will be similar to those employed in connection with the prizes for papers on the water relations of plants, which were offered in April, 1915. The names of the judges who will appraise the submitted papers wrill be announced in a later issue. The contesting contributions should be in the hands of the Editor of The Plant World by December 1, 1916, and the announcement of the award will be made not later than March 1, 1917. The early announcement of this contest is made in the hope that an entire year will afford time for a vigorous competition. In the second Supplement to the Monthly Weather Review (Sep- tember, 1915) Professor J. Warren Smith, of Columbus, has published an extensive series of meteorological data and phenological observations made at Wauseon, in Northwestern Ohio, between 1873 and 1912 by Mr. Thomas Mikesell. The full records of daily minimum, mean and maximum temperatures and of daily precipitation have been published. The phenological data comprise observations on 16 kinds of wild and garden fruits, on 20 crop plants, on 48 trees, shrubs and vines, and on 114 herbaceous plants. Professor Smith has already published a paper on the effect of weather on the yield of corn (Monthly Weather Review, February, 1914), based upon Mr. Mikesell's records, but he has done nothing more in the present paper than to present all of the data in a concise form. A record of such vouchsafed accuracy, of such long duration, and covering nearly 200 species of plants, is of great value as a source of material for investigating the relation of climatic factors to plant activity. Another paper of phenological interest is published in the second Supplement of the Weather Review by Mr. George N. Lamb, of the 319 320 NOTES AND COMMENT Forest Service. He has constructed a calendar of the leafing, flower- ing and seeding of some 72 trees of the eastern United States. These results are presented in a diagrammatic form, and in such a manner as to show the dates of a given activity in the northern and southern portions of the range of a tree, without, however, showing the dura- tion of any of the activities. The sources of information and the con- ventions of the chart are fully discussed and a bibliography of tree phenology for the eastern United States is appended. The heavily forested portions of equatorial Africa form a rela- tively small percentage of the whole area of that continent. It is the contention of Captain C. H. Stigand, writing in the Geographical Journal (June, 1915), that the primitive agricultural methods of the natives are responsible for a great reduction in the area of forest. The fertility of newly cleared land and the rapid loss of this fertility under cultivation are responsible for continuous encroachments on the forest. The abandoned fields are occupied by grass and bush and are apparently unable to revert to forest so long as the forest front con- tinues to be attacked. Several lines of evidence are adduced by Cap- tain Stigand to show that extensive arsas of forest have disappeared, probably during the last 600 years, in British East Africa, in Uganda, and in the northern portion of the Congo. At the Philadelphia meeting of the American Association a group of men interested in ecology met informally to consider the advisability of organizing an American Ecological Society. The principal incen- tives toward the formation of such a society are the desire of animal and plant ecologists to have greater contact and the urgent need of summer field meetings. A committee was appointed to prepare a scheme of organization and to call a meeting of all ecologists inter- ested in the proposed society, to be held in Columbus during convoca- tion week in December of the present year. Those who are interested in the society but do not expect to attend the Columbus meeting- should communicate with the Secretary of the organization commit- tee. Dr. H. C. Cowles, University of Chicago, Chicago, Illinios. EFFECT OF VANILLIN AS A SOIL CONSTITUENT J. J. SKINNER Department of Agriculture, \\ ashing ton ^ D. C. INTRODUCTION The effect of vanillin on plants in solution cultures, in pot cultures, and in field plots has been the subject of an investiga- tion by the laboratory of Soil Fertility Investigations which was made necessary by the discovery of vanillin in soils.1 Vanillin has the characteristics of an aldehyde, and exists in the seeds, roots, stem, leaves and grain of many plants.2 It is harmful to wheat seedlings in water cultures, even in such low concentrations as a few parts per million, and the plants are killed in solutions of 500 parts per million in a few days.3 The toxic effect is less marked upon the tops of the wheat plants than upon their roots. Vanillin is also harmful in nutrient culture solutions composed of calcium acid phosphate, sodium nitrate, and potassium sulphate. It is an oxidizable substance and is less harmful in solutions of some of these nutrient salts than in others, especially those high in nitrate.4 Sodium nitrate and calcium carbonate,5 which themselves induce oxidation, ameliorate the harmf ulness of vanillin. The isolation of vanillin from soils and its harmfulness to plants in aqueous solutions has made a study of its effect in soils and under field conditions essential. The results of such experi- ments with cowpeas, garden peas, and string beans will now be 1 Shorey, E.C., Jour. Agr. Res., 1: 357, 1914. 2 See especially Sullivan, M. X., Jour. Ind. Eng. Chem., 6: 909, 1914. 3 Schreiner, Reed, and Skinner, Bull. 47, Bureau of Soils, U. S. Dept. Agr., 1908. 4 Schreiner and Skinner, Bull. 77, Bureau of Soils, U. S. Dept. Agr., 1911. 6 Schreiner and Reed, Am. Chem. Soc, 30: 85, 1908. 321 THE PLANT WORLD, VOL. 18, NO. 12, 1915 322 J. J. SKINNER given, together with the action of vanillin on clover in soil in pots and with wheat plants grown in several soils of different characters. EFFECT OF VANILLIN ON SOILS IN POTS An experiment to determine the effect of vanillin on clover was made by growing clover in Chester loam soil in large pots. Or- dinary clay flower pots holding 6 pounds of soil were used. One pot was untreated; the other had a total of 300 parts per million of the vanillin added to it. When the soil was potted, 100 parts per million of the vanillin were added and clover then sown, 0.5 gram of seed per pot. The clover was sown April 12, and came up well. On April 28, 50 parts per million of vanillin were added in solution through a funnel passing into the soil nearly to the bottom of the pot, thus avoiding direct contact with the tops or roots of the clover. In May 15, on June 1 and again on June 10, 50 parts per million were added, making the total application 300 parts per million. The experiment was discontinued June 21, 1912. The effect of vanillin was noticeable from the first. The harmful effect is shown by comparing the untreated pot and the vanillin-treated pot shown in figure 1 . The vanillin-treated plants were normal in appearance but stunted in growth. The green weight taken at the termination of the experiment was 8 grams from the untreated pot and only 3.8 grams from the vanillin- treated pot, a decrease of 53%. The soil used in this experiment was a soil of moderate pro- ductiveness, and vanillin applied to it at different periods of the growth of the plants was distinctly harmful. Other experiments were made to test the effect of different amounts of vanillin in several soils, each having different properties and being of differ- ent geological origin. In the following experiments wheat was used as the test crop and the total application of vanillin was made before the soil was potted and seeds planted. In this experiment the effect of vanillin in several soils was studied by growing wheat in pots. The soils used were infertile Florida sand, an infertile sample of Susquehanna sandy loam, VANILLIN AS A SOIL CONSTITUENT 323 and a good sample of Hagerstown loam. The paraffined wire pot method6 was used, six wheat plants were grown in each pot, and two pots were used for each treatment. The plants grew from May 5 to May 24. Photographs of the growing plants were taken, which show the action of vanillin in each soil. At the end of the experiment the green weight was determined. The Florida sand used in this experiment had grown citrus fruits in the field and was unproductive. A laboratory exami- nation showed the soil to be acid. Vanillin was isolated from ■nSCAw Fig. 1. Effect of vanillin on clover. (No. 1, Soil untreated. 2, Soil plus vanillin.) this soil in the investigations referred to above. The Susque- hanna sandy loam was taken from an infertile area in Maryland. The natural growth on this soil was poor, and its response to fertilizer and cultural treatments was only moderate. Its oxi- dizing power and life activities were found to be very weak. The Hagerstown loam is a fertile soil. The soil was taken from a productive field of the Pennsylvania Agricultural Experiment Station. The soil is neutral in reaction, has strong oxidizing power, and grows thrifty plants in pots. 6 Cir. 18, Bureau of Soils. 324 J. J. SKINNER Vanillin was used in amounts of 100 to 500 parts per million- It was applied to the soil by dissolving in water and mixing the solution in the soil before potting. The results of the experiment on the effect of vanillin in the Florida sand, Susquehanna sandy loam, and Hagerstown loam are given in table 1. The actual green weight of the plants grown in the two pots are given for each treatment and the relative weight with the growth in the untreated soil taken as 100. TABLE 1 Effect of vanillin on wheat plants in pots grown in Florida sand, Susquehanna sandy loam, and in Hagerstown loam TREATMENT FLORIDA yellow sand (infertile sand) susquehanna sandy loam (unproductive soil) hagerstown loam (productive soil) Green weight Relative weight Green weight Relative weight Green weight • Relative weight Soil untreated grams 1.40 1.32 1.32 1.35 1.20 1.18 100 94 94 98 86 84 grams 1.80 1.85 1.70 1.33 1.30 1.02 100 103 94 74 72 57 grams 1.9S 1.87 2.02 2.05 1.96 1.95 100 Soil + 100 p. p.m. vanillin Soil + 200 p. p.m. vanillin Soil + 300 p. p.m. vanillin Soil + 400 p. p.m. vanillin Soil + 500 p. p.m. vanillin 94 102 103 99 99 The vanillin was quite harmful in amounts of 400 and 500 parts per million in the Florida sand and was only moderately harmful in amounts of 100 to 300 parts per million. With the Susquehanna sandy loam the vanillin reduced growth consid- erably when applied at the rate of 300, 400, and 500 parts per million. It was slightly harmful with 100 and 200 parts per million. Vanillin had no harmful effect in the Hagerstown loam —two of the treatments were slightly above the check and three slightly below. The growth in the untreated soil of the Hagers- town loam was better than in the Susquehanna sandy loam and considerably better than in the Florida sand. It is seen from this experiment that vanillin is harmful in two of the soils and has no effect in the third. Vanillin is easily oxi- dized and changed under favorable conditions, and if this took VANILLIN AS A SOIL CONSTITUENT 325 place the action on plant growth would not be noticeable. In as much as the Florida sand was found to contain vanillin when sent in from the field it was to be expected that vanillin would persist in this soil, that added vanillin would not be changed and would remain as such to have its effect on plants grown in the soil. The Susquehanna sandy loam is also a soil having small oxidizing power and low life activity, and added quantities of vanillin apparently remained as such and had their effect on plant growth. The Hagerstown loam is a soil of entirely differ- ent characteristics, being highly productive, which indicates good life activities and good oxidizing power. Vanillin when added does not have harmful effects on plants grown in the soil, as it probably does not remain in this soil as such, but is changed or destroyed by the oxidation which is going on in soils of this character. In order to study further the action of vanillin in soils and its bearing on soil fertility, the effect of vanillin under field condi- tions was tested in plots. Three leguminous crops — cowpeas, string beans, and garden peas — were grown to maturity in this experiment, with the following results : EFFECT OF VANILLIN ON COWPEAS, STRING BEANS. AND GARDEN PEAS GROWN IN THE FIELD The effect of vanillin in soils under field conditions was tested on plots at the experiment farm of the Agricultural Department at Arlington, Virginia. Three crops were grown, namely, cow- peas, string beans, and garden peas. These experiments were made during the summer of 1913. The treated plot was adjoined on each side by an untreated plot growing the same crop. Each plot was 8| feet square, or one-fourth of a square rod. The soil on which these experiments were made is a silty clay loam, low in organic matter. The ground is level and has surface drain- age. The soil throughout these plots and their controls is uni- form, so the results secured should not be considered as unduly influenced by irregularities due to non-uniformity of the soil in different plots. The soil is of an acid nature. The land was plowed early in May and prepared for seeding. Fig. 2. Effect of vanillin on cowpeas in the field. F- Fig. 3. Effect of vanillin on garden peas in the field. Fig. 4. Effect of vanillin on string beans in the field. 326 VANILLIN AS A SOIL CONSTITUENT 327 Four applications of vanillin wore made. The first on May 20, one day before the planting of seed. The other three appli- cations were made periodically during the growth of the crops — May 28, June 5, and June 24. The vanillin was applied by dis- solving in water and sprinkling the solution uniformly on the surface of the ground before planting, after which the soil was raked thoroughly. The remaining applications were made after planting by sprinkling the solution between the rows of plants, the soil being subsequently cultivated. The total application was at the rate of 284 pounds per acre, in four equal parts. TABLE 2 Yield of cowpeas, garden peas and string beans as affected by vanillin in the field (yield per plot) COWPEAS . GARDEN PEAS STRING BEANS TREATMENT Vines Pods Vines Peas Vines Beans ( Sreen ( !ured Check a pounds 28.0 23.0 pounds 10.0 8.5 pounds 6.6 5.6 pounds 1.72 1.50 pounds 1.66 1.48 pints 4.50 4.00 pou nds 3.55 2.94 pounds 1.90 1.66 pints 4.75 Check b 4.J5 Average check Vanillin 25.5 17.0 9.3 5.7 6.1 4.0 1.61 1.12 1.57 1.14 4.25 3.00 3.24 2.71 1.78 0.55 4.45 1.50 Difference 8.5 3.6 2.1 0.49 0.43 1.25 0.53 1.23 2.95 The crops germinated uniformly. The effect of the vanillin was noticeable from the beginning and throughout the experi- ment. The growth was stunted, though the plants grew slowly to maturity, and were harvested. The three crops were sown on their respective plots May 21. The cowpeas were harvested September 27, the garden peas had matured by June 30, and were harvested on that date, and the string beans were harvested July 22. The yields of the various plots are given in table 2. An examination of the table shows that vanillin checked growth and materially lessened the yield, with each of the crops. In the case of the cowpeas there was a reduction of 33% of green vines and 39% of cured hay. The garden peas were reduced 30% in 328 J. J. SKINNER vines and 20% in marketable peas. The string beans were re- duced 17% in vines and 69% in beans. It was noticeable that the cowpeas growing on the vanillin-treated plot had a pale yel- low color, and were weaker than on the check plot. Fig. 5. Yield of cowpeas, garden peas,, and string beans on check plot and vanillin-treated plot. (1) Cowpea vines, (2) pods on check plot; (3) cowpea vines, (4) pods on vanil- lin plot; (5) garden pea vines, (6) pods on check plot; (7) garden pea vines, (8) pods on vanillin plot; (9) string bean vines, (10) beans on check plot; (11) string bean vines, (12) pods on vanillin plot. The crops were photographed in the early stages of their growth, and are shown in figures 2, 3 and 4. In each figure the first four rows are growing on the plot to which vanillin was added and the last four rows are the check plot. Figure 2 shows VANILLIN AS A ROIL CONSTITUENT 329 the effect of the vanillin on cowpeas, figure 3 on garden peas, and figure 4 on string beans. The photographs show that even at this early stage of growth each of the crops is retarded by vanillin. When the crops were harvested the vines and pods from each plot were piled separately, and photographed together with the yield from one of its check plots. It is also shown here in the case of each crop that the vanillin treated plots yielded much less than the untreated soil. These photographs are shown in figure 5. PRESENCE OF VANILLIN AND ITS EFFECT IN THE SOIL SIX MONTHS AFTER APPLICATION The question of the length of time the vanillin would persist in the Arlington soil and have an influence on its crop-producing power has also been investigated by a chemical study in the laboratory and by pot tests. Samples of soil for these purposes were obtained from the plots the last of November, six months after the substance was applied, and after it had matured a crop. The soils were examined for vanillin by the method already de- scribed by Shorey.7 The method, in brief, consists of making an alkaline extract of the soil. The extract is acidified and fil- tered and then shaken out with ether. The aldehyde is re- moved from the ether by sodium bisulphide solution, acidified, and the liberated aldehyde again taken up in ether. The ether extract obtained by this process will contain aldehydes if present in the soil. Vanillin was found to be present in each of the soils from the plots to which the substance had been applied six months previously. Pot tests were made in the soil from these plots, in order to determine if the vanillin still had an effect on growth. In these experiments, which were conducted by growing wheat, cowpeas, garden peas, and beans in small paraffined wire pots, it was found that each of the vanillin-treated pots produced poorer wheat than soil from the check plots. Wheat was reduced in growth 26% in the soil from the vanillin plot which grew cowpeas 7 Jour. Agr. Research, 1: 357, 1914. 330 J. J. SKINNER in the field, 25% in the treated soil which grew garden peas in the field, and 29% in the treated soil which grew string beans in the field. Cowpeas growing in pots in the soil which grew cowpeas in the field made 29% less growth in the soil treated with vanillin than in the soil from the check plot. Garden peas in the soil from the vanillin-garden pea field plot also made 29% less growth than in soil from the check plot, and string means made 6% less growth in the soil from the vanillin-string bean plot than in soil from its check plot. The vanillin was still harmful to the respective crops six months after its application, and after it had produced the same crop in the field. These experiments show that vanillin persists in this heavy silty clay loam soil and affects its fertility for a considerable length of time. AN INVESTIGATION OF THE CAUSES OF AUTONOMIC MOVEMENTS IN SUCCULENT PLANTS EDITH BELLAMY SHREVE Tucson, Arizona (Concluded) II. Livingston and Brown4 found that in the climate of southern Arizona (the habitat of the plants used in this research) "green plants when subjected to relatively great diurnal evaporation intensity, at least frequently, exhibit a marked fall in foliar mois- ture content by day and a corresponding rise by night." They found this true for several species of thin-leaved plants and for one succulent, Trianthema portulacastrum., but failed to find it in two species of thick leaved xerophytes (Covillea glutinosa and Prosopis velutina). However, the present author5 found it for Parkinsonia microphylla, which is a very thick leaved perennial. Lloyd6 found the same result with leaves of Fou- quieria splendens and working with cut shoots of the same species on burettes, he obtained a difference between water in- take, as measured by the burette, and transpiration loss, as meas- ured by loss of weight, which was negative for the day and posi- tive for the night. In order to test the matter for this cactus experiments 9 and 10 were carried out. 4 Livingston, B. E. and Brown, W. H., Relation of the daily march of trans- piration to variations in the water content of foliage leaves. Bot. Gaz. 53: 309-330, 1912. 6 Shreve, E. B., The daily march of transpiration in a desert perennial. Car- negie Inst. Wash. Pub. No. 194, 1914. 6 Lloyd, F. E., The relation of transpiration and stomatal movements to the water content of leaves of Fouquieria splendens. The Plant World 15: 1-14, 1912. 331 332 EDITH BELLAMY SHREVE Experiment 9. Object: (1) An investigation of the changes in turgidity between day and night, as measured by the difference between water-intake at the roots and water- loss by transpiration for the same period. (2) A comparison of the changes in turgidity with the movements of the joints. TABLE 7 Experiment 9. Correlation of movements of Opuntia and water-content of the tissues WATER-CONTENT Gain Loss Up Down E* Plant No. 13 June 28, 6 p.m. June 29, 6 a.m. June 29, 6 p.m. June 30, 6 a.m. June 30, 6 p.m. grams grams CC. CC. cm. cm. grams 0.26 0.02 0.00 0.24 0.0 0.5 0.77 0.11 0.11 0.00 0.00 0.1 0.0 0.18 0.38 0.04 0.00 0.34 0.0 1.1 0.67 0.11 0.34 0.23 0.00 1.0 0.0 1.36 □ Plant No. 14 June 28, 6 p.m. June 29, 6 a.m. June 29, 6 p.m. June 30, 6 a.m. June 30, 6 p.m. July 1, 6 a.m.. . July 5, 7 p.m.. July 6, 7 a.m.. . July 6, 6 p.m.. July 7, 7 a.m.. . July 7, 6 p.m.. July 11,6 a.m. 0.55 0.42 0.00 0.13 0.0 5.8 0.77 0.14 0.14 0.00 0.00 0.0 0.0 1.08 0.33 0.27 0.00 0.06 0.0 2.8 0.67 0.07 0.20 0.13 0.00 5.2 0.0 1.36 0.21 0.07 0.00 0.14 0.0 0.6 0.46 0.14 0.02 0.00 0.12 0.0 0.7 0.46 0.96 0.51 0.00 0.45 CO 19.9 4.50 0.62 0.87 0.25 0.00 6.9 0.0 1.14 0.81 0.33 0.00 0.48 0.0 7.8 4.95 0.94 2.04 1.10 0.00 21.8 0.0 1.77 □ ■ ■ □ ■ □ * T = total transpiration for the period indicated. A = total absorption for the period indicated.. E = water loss per hour from standard atmometer. Material: Plants Nos. 13 and 14. No. 13 had been growing in the open until a month before the time of the experiment, when it was cut off just above the roots and placed with its lower end in a bottle of water. As soon as a large fibrous root system had developed in the water the plant was considered ready for use. No. 14 was a two year old individual which had been raised from seed in the green-house. It was removed from the bed with a large fleshy root intact and placed with its roots in a second bottle of water. Many of the small roots were AUTONOMIC MOVEMENTS IN SUCCULENTS 333 broken at the time of removal from the soil but measurements were not begun until an abundant supply of fibrous roots had been formed. Method: Nos. 13 and 14 were sealed in separate bottles in the following way. Each bottle was completely filled with water. A rubber stopper containing three holes, one for the plant stem, one for a burette and one for a thermometer, was cut into two pieces and then forced into place around the woody part of the stem until the system was air-tight. The water in the burette rose above the general level and was adjusted to a convenient height. The burette was of nar- row diameter, being graduated to 0.01 cc. with a possibility of readings being; estimated to 0.001 cc. Fig. 7. Correlation of movements of joints and changes in turgidity of the plant. Solid line, movements. Broken line, water-content changes. June 28 to July 1, evaporation of average intensity. July 1-3, evaporation of unusually high intensity. Two lowest graphs indicate temperature and light conditions. See experiment 9. At the beginning and end of each period the entire bottle with the plant was weighed for the determination of the loss from transpiration. Atmometers of the Livingston type were used, for the measurement of evaporation. In order to determine the amount of water taken up by the roots, the height of the liquid in the burette was read at each period and the difference between the read- ings, after it was corrected for contraction and expansion of volume due to tem- perature changes, represented the amount of water absorbed by the roots. The correction for expansion and contraction was found by means of two control bottles of the same capacity as the ones containing the plants. These bottles were filled with water and fitted up in all respects like the ones holding the plants. By means of twenty readings extending over several days the amount of change in volume per degree, for the temperatures used, was found from meas- urements of the changes in height of the water in the burettes and of the corre- i \% 334 EDITH BELLAMY SHREVE sponding temperature changes. The twenty readings showed a maximum differ- ence of 4% in the value of the change of volume per degree. A correction fac- tor of 0.157 cc. per degree was found by averaging twenty readings. At each read- ing for the water-intake of the plant, the temperature of the water was read and thus the total amount of temperature change for the period found. The change in volume per degree, as determined above, was then multiplied by the number of degrees of change the water had undergone and this correction subtracted from the total change in level. The tables contain the corrected amount of water absorbed. The difference between absorption and transpiration gives the gain or loss in water-content of the plant. These changes in water-content have been plotted and appear in figure 7. A convenient point on the paper was selected to repre- sent the original water-content and, using this as a starting point for plotting the losses or gains, each new loss or gain was measured from the point immediately preceding it. Measurements of the positions were made, as formerly, with a meter- stick. Results: From table 7, it is seen that under average evaporative intensity and with the normal day to night changes in light intensity and air temperature the plants lose more water at night than they take up at the roots, and in the day they take up more than they lose by transpiration. This means nothing else than that the turgidityof the plant increases during the day and decreases during the night. Simultaneous measurements of the position of joints show that in- creased turgidity is accompanied by a rise and decreased turgidity by a drop of the joint. The measurements taken on July 5-6, under increased evaporative conditions show, as in experiment 7, that the movements for day and night have been reversed and, what is more important, the results of these days show that the turgidity changes still parallel the movements. Thus the evidence is that the short period movements are the direct result of turgidity changes. In order to gain further proof of this fact the same kind of measurements were taken in the next experiment by different methods. Experiment 10. Object: The simultaneous measurement of water-content changes and the movement of joints. Material: Plants Nos. 30, 31, 32, and 34. They varied in age from about three to eight years. All were transplanted from the open about eight weeks before the beginning of the experiment. They became well established in their new environment, as was shown by the considerable growth they made. During the experiment their pots were kept saturated with water. Method: The movements were measured by means of automatic pen tracings on a drum. Figure 9 shows the details of the arrangement. The apparatus has been described in a slightly different form by MacDougal7 and has recently been used by him for the growth measurements of Platyopuntias, with the lever arm resting directly upon the joints. In order to adopt the apparatus to the measure- ment of the movements it was necessary to make the lever which touches the joints longer than the pen lever, in order to reduce the magnitude of the movement 7 MacDougal, D. T., Practical text-book of plant physiology. (Longmans Green and Co.), p. 291. AUTONOMIC MOVEMENTS IN SUCCULENTS 335 enough to get the whole tracing on the drum. These tracings have been reduced and appear in figure 8. The measurement of water-intake and out-go was made by a method devised by Briggs and Shantz8 for the determination of the wilting point of succulent plants. Briefly, the method consists in balancing the plant upon a knife edge which is fastened at the juncture of pot and plant. The system is balanced in a horizontal position by means of a movable screw; and then immediately returned to a vertical position, where it remains until the close of the period considered. At this time its point of equilibrium is again tested in the horizontal position. The pot is sealed so that it can lose no water except to the plant. As the plant loses water through transpiration, water moves from the soil and replaces that lost by the plant and the pot side of the system becomes lighter and rises. This process is repeated as often as the system is restored to equilibrium by means Plant No. 30. Jun. 20. Jun. 2a. Fig. 8. Correlation of movements of joints and turgidity changes in the plant. Solid line, movements. Broken line, water-content changes. Two low- est graphs indicate temperature and light conditions. See experiment 10. of the movable screw. If the plant does not obtain enough water to replace the loss from transpiration the aerial side of the system will rise. The authors state that by determining the loss in weight from the entire system on a pair of bal- ances and comparing this with the weight which, when placed at the center of pot or aerial part of the plant, will restore equilibrium, absorption and trans- piration can be separated. This is true provided the conducting system is able to pass up the water as fast as the roots take it in. The calculation is not quite so simple as might be supposed from the author's statement. Furthermore, the accuracy of the results is limited by the fact that an estimation of the center of transpiration loss must be made, and this involves two sources of error, the first being that it must be assumed that all of the upper part of the plant transpires at the same rate, and the second that there is difficulty 8 Briggs, L. J. and Shantz, H. L., The wilting coefficient for different plants and its indirect determination. Dept. Agr. Bur. Plant Ind. Bull. No. 230, pp. 47-51. 336 EDITH BELLAMY SHREVE in determining the volumetric center of the aerial parts. It is possible to find a probable maximum error by supposing the center of transpiration which is se- lected, to be wrong a given proportion of the length of the plant, first in one direc- tion and then in the other. An example will best illustrate the method of calculation. From table 8 it is found that Plant No. 30, the centers of whose pot and aerial parts are 5.5 cm. and 15 cm. from the knife edge, showed the following readings on the night of June 22-23. At S.51 p.m. the system was balanced by means of the screw and then weighed as a whole on balances. At 8.29 a.m. the next morning the plant Fig. 9. Apparatus used for the determination of transpiration and absorp- tion in experiment 10. At the left may be seen the device for automatically recording the movements of joints. was taken from the dark room and again placed in a horizontal position, resting upon its knife edge. The plant rose so that no point of equilibrium could be found, showing that the plant had lost more water than it had gained from the soil during the night. When 3.5 grams were placed on the pointer at a distance of 5.5 cm. from the knife edge the system was restored to equilibrium. The bal- ances showed that the system had lost 5.5 grams during the period. If the equa- tion a = a represents the condition of equilibrium at 8.51 p.m. and .r the amount AUTONOMIC MOVEMENTS IN SUCCULENTS 337 TABLE 8 Experiment 10. Correlation of movements of Opuntia and water-content of tissues T = total transpiration for the period indicated. A = total transpiration for the period indicated. E = water loss per hour from standard atmometer. MAXIMUM ERROR FOR A WATER-CO NT i: NT Gain Loss Plant No. June 20, June 21, June 21, June 21, June 21, June 22, June 22, June 22, June 23, June 23, June 23, 8 p.m. 8 a.m. 12 m.. 4 p.m. 9 p.m. 8 a.m. 12 m.., 7 p.m. 7 a.m. 12 m.. 4 p.m. grams grams 3.6 1.2 0.9 0.8 5.5 0.9 1.2 1.5 0.8 3.3 2.0 0.5 1.0 3.1 1.8 2.3 1.5 0.9 rams +0.1 -0.05 ±0.2 ±0.1 ±0.1 + 0.4 -0.7 ±0.2 +0.4 -0.2 +0.3 -0.03 ±0.04 grams 0.0 0.8 0.0 0.2 0.0 0.9 1.1 0.0 0.1 grams 0.3 0.0 0.4 0.0 2.4 0.0 0.0 0.0 0.0 Plant No. SI June 20, 8 p.m. June 21, 8 a.m. June 21, 12 m. . June 21, 4 p.m. June 21, 7 p.m. 5.1 0.5 0.7 0.4 3.2 2.4 2.7 0.0 /+0.3 1-1.1 f+0.7 I — 1-1 ±0.4 ±0.02 0.0 1.9 2.0 0.0 1.9 0.0 0.0 0.4 Plant No. June 23, 8 p.m. June 24, 8 a.m. June 24, 12 m. . . June 24, 4 p.m.. June 24, 7 p.m.. June 24, 11 p.m. 3.4 5.3 3.4 5.4 0.5 8.0 3.8 1.8 4A 0.5 +0.2 -0.4 +0.8 -0.2 ±0.2 +0.8 -0.2 ±0.06 4.6 0.0 0.0 0.0 0.0 0.0 1.5 1.6 1.0 0.0 THE PLANT WORLD, VOL. IS, NO. 12, 19l5 338 EDITH BELLAMY SHREVE TABLE 8— Continued TIME MAXIMUM ERROR FOR A WATER-CONTENT Gain LOS3 Plant No. 32 — Continued June 25, 5 a.m. June 25, 9 a.m. June 25, 5 p.m.. June 25, 11 p.m. June 26, 5 a.m.. June 26, 7 a.m.. grams 4.5 3.2 10.2 3.6 7.3 2.5 grams 2.0 6.1 9.6 2.8 4.9 2.5 grains f+0,8 i-0.5 (+0.5 ^-0.3 ±0.1 ±0.1 ±0.3 grams 0.0 2.9 0.0 0.0 0.0 0.0 grams 2.5 0.0 0.6 0.8 2.4 0.0 riant No. 34 June 20, June 21, June 21, June 21, June 21, June 22, June 22, June 22, June 23, June 23, June 23, 8 p.m. 8 a.m. 12 m.. 4 p.m. 9 p.m. 8 a.m. 12 m.. 7 p.m. 7 a.m. 12 m.. 4 p.m. 3.6 1.2 0.9 0.8 5.5 0.9 1.2 3.3 2.0 0.5 1.0 3.1 1.8 2.3 (+0,1 1-0.05 ± 0.2 ±0.1 ±0.1 f+0.4 1-0.7 ±0.2 f+0.4 \-0. 2 Condensation of water vapor on pots \ / 1 0.0 0.8 0.0 0.2 0.0 0.9 1.1 1.5 0.8 1.5 0.9 f+0.3 -0.03 = 0.4 0.0 0.1 0.3 0.0 0.4 0.0 2.4 0.0 0.0 0.0 0.0 in grams transferred from pot to aerial part of the plant during the night than at 8.29 a.m. the condition of equilibrium will be represented by the equation a - x (5.5) = a + x (15) + 3.5 (5.5) - 5.5 (15) x = 3.1 That is, transpiration was 2.5 grams greater than absorbtion. In the above cal- culation the weight is in every case multiplied by its distance from the knife edge. The maximum error for this plant was calculated by considering the estimated center to be 5 cm. wrong first to the right and then to the left. Thus a total error is calculated which allows for an error in the center of the transpiring parts amounting to one-third of the length of the plant. A few minor changes were made in the form of the apparatus as described by Briggs and Shantz. The apparatus used in the present work is shown in figure 9. AUTONOMIC MOVEMENTS IN SUCCULENTS 339 The devise for fastening the knife edge to the pot, which is shown in the illustra- tion, was found to be much more satisfactory than the cement sealing recommend- ed by the authors. The glass pots used by these same authors were not suitable for the present work. Consequently, the plants were allowed to become estab- lished in galvanized iron cylinders in the bottoms of which holes were punched for drainage. At the time of the experiment the bottoms of the cylinders were sealed with galvanized iron caps held in place and made airtight by plastocene. The sealing for the tops of the pots was made with heavy cardboard cut to fit and made airtight by a thick layer of plastocene. A rubber stopper was fastened with wire around the woody base of the plant so that the plastocene might not come in contact with the plant surface. All plastocene was completely covered with tin-foil, in order to avoid errors from dust, knocks etc. Results: The same facts appear as in former experiments (1) Under normal conditions, the plant loses more water at night than it absorbs, and in the day time it absorbs more than it loses. This means that its turgidity is less at night than in the day time. (2) In all cases lessened turgidity is accompanied by a down- ward movement of joints and increased turgidity by an upward movement. The agreement of the results from this experiment with those obtained in experiment 9, where the actual amount of water absorbed by the roots was meas- ured directly, shows the correctness of the assumption made above, namely, the conducting tissue must be able to pass up water as fast as it is absorbed by the roots. Consequently the amounts under the heading A in table 7 are a true approximation of the water absorbed by the plant. Although it is aside from the subject considered in this paper' it seems worth noting that this last experiment shows that when wilting point determinations of cacti are made by the Briggs and Shantz method, care must be taken that readings are made at the corresponding hour each day, since any reading taken for an interval in which the night occupied the greatest part of the period might show an apparent wilting point when the plant was still obtaining its normal amount of water from the soil. Such changes in turgidity as the last experiments have shown to exist, would probably cause both longitudinal and radial expansion and contraction of joints. Some joints are for a time in a vertical position and at that time show no upward and downward movement. Joints in a vertical position were chosen as subjects on which to detect contraction and expansion. Meas- urements of length with a meter stick and of diameters with a vernier caliper gave no evidence of such changes ; but the auto- matic method of magnification used in the next experiment showed them clearly. 340 EDITH BELLAMY SHREVE $ / Fig. 10. A device for automatically measuring radial expansion and con- traction of joints. See experiment 11. Experiment 11. • Object: The discovery of any longitudinal and radial contraction which may take place from day to night, under normal conditions. Material: Plants Nos. 18 and 19. They were both potted plants having verti- cal joints. No. 18 had a joint which was grown in the green-house and No. 19 had made its entire growth in the open. Method: The apparatus which was used is shown in figure 10, where it is in the position to measure radial expansion and contraction. The part of the joint immediately opposite the point of contact of the lever which moves the recording pen, was imbedded in a plaster of paris jacket, so that it might be held AUTONOMIC MOVEMENTS IN SUCCULENTS 341 in place firmly. For the measurement of the longitudinal changes the end of the curved lever was bent up until it rested in the same horizontal plane with the pen and its end then placed on the tip of the joint. Results: The records from the tracings have been transferred to coordinate paper and appear in figure 11. The recording pen magnified the changes about three times and the actual maximum difference is size between day and night was about 0.15 cm. in both the radial and longitudinal directions. All of the records show an expansion for the day and a contraction for the night. The changes on cloudy days were less than on bright days. B Pen trace. 100" 80° Apr. 27 Apr. 28 Apr. 29 Apr. 20 Apr. 21 Apr. 22 Apr. 23 Apr. 24 Apr. 25 Fig. 11 A. A copy of an automatic pen trace (topmost curve) showing radial contraction and expansion of a joint. See experiment 11. Fig. 11 B. A copy of an automatic pen trace (topmost curve) showing longi- tudinal expansion and contraction of a joint. Two lowest graphs indicate temperature and light conditions. See experiment 11. Direct determinations of the water-content were attempted by heating joints to constant weight at 100°C. and calculating the original water-content per gram of dry weight. The individ- ual variations of the joints were so great that any day to night changes were masked. However, the results of experiments 10 and 11 show that a difference in water-content does exist and there is no need of further proof that turgor is greatest in the day time when normal conditions exist. Thus the shorter period movements, as well as the longer ones, have been shown to be due to turgor changes. 342 EDITH BELLAMY SHREVE AVhat factors cause the day to night turgor changes, i.e., why the difference between absorption and transpiration is positive in the day and negative at night is of course another question. The author is now at work upon these more fundamental causes and will report upon the progress of the work at an early date. That the phenomena which have been studied in Opuntia versicolor are practically universal for Opuntia seems probable from measurements which have been made on other species. The seasonal movement has been observed in the following: Opuntia fusicaulis, 0. fulgida, 0. mamillaia, 0. tetracantha, 0. arbuscula, 0. leptocaulis, 0. bigelovii, all of the cylindrical form, and in 0. leavis, 0. blakeana, 0. linguiformis, 0. fusicaulis, and 0. monacantha, of the flat-jointed type. The day to night move- ment has been measured on 0. lepticaulis, 0. fusicaulis, and 0. monacantha and found to be the same as for 0. versicolor. SUMMARY (1) Twelve species of Opuntia and also Carnegiea gigantea, have been found to show seasonal movements of stems and branches, which consist of a drop during desiccation and a rise during recovery. These movements have been correlated with turgidity changes. (2) The form of the adult cactus plant and the position of its branches is determined by the water relations existing during the period of growth and secondary thickening of its various parts and not by any peculiarities residing in its growing point or in its mode of initiating branches. (3) Opuntia versicolor, 0. fusicaulis, and 0. leptocaulis were measured for the investigation of a short period movement which is shown to consist of an upward movement during the day and a downward one at night, when normal conditions of tem- perature, light intensity, soil-water content, and evaporative power of the air, exist. (4) A detailed study of Opuntia versicolor showed that this short period movement is influenced by temperature, light in- tensity, evaporative power of the air, and the water-content of AUTONOMIC MOVEMENTS IN SUCCULENTS 343 both soil and plant tissues. The influence of these factors is indirect and acts through other intermediate processes. (5) The day-to-night movements have been shown to be caused directly by turgidity changes. (6) Opunlia versicolor is less turgid at night than in the day time as is shown by the fact that the plant absorbs more water through its roots in the day time than it loses by transpiration, and at night loses more than it absorbs. This is the opposite of the behavior shown by all non-succulents which have been studied. BOOKS AND CURRENT LITERATURE Chemistky of Colloids. — The want of a text book of colloids in English has been long felt and much discussed. Recently Dr. W. W. Taylor of Edinburgh University has been moved to supply it and his volume, issued early in this year, is at hand.1 The work is most credi- table. In aim and content it stands between the admirable but brief treatment of Hatschek2 and the larger detailed treatises of Freundlich,3 Oswald4 and Zsigmondy.6 For the colloid specialist these latter works will remain indispensible. The greatest usefulness of Dr. Ta}dor's volume will be in the hands of those workers in chemistry, biology and adjoining fields who are finding more and more necessary some knowl- edge of colloids and their behavior. For the needs of these readers the book is a model of selection and condensation and the well chosen references to original literature furnish ample guides when more de- tailed information is necessary. The book is in four parts. First are 163 pages devoted to the gen- eral properties, behavior and relations of colloidal systems. Following are 56 pages on the preparation of typical colloids, especially the metallic sols. The directions are detailed and practical and will be most helpful to those inexperienced in the difficult art of preparing stable colloidal solutions. The third part, of 42 pages, discusses adsorp- tion and surface phenomena in general, excluding, however, any spe- cific treatment of catalysis at surfaces. The fourth and last part (56 pages) is devoted to applications of colloid chemistry and includes chapters on casein, soaps and other semi-colloids; on the phenomena and theories of dyeing; on tanning, the colloids of the soil and the purification of waste waters and sewage; and on the applications of colloid chemistry to biology. 1 Taylor, W. W., The Chemistry of Colloids. Pp.328. New York, Longman Green and Company, 1915. 2 An Introduction to the Physics and Chemistry of Colloids. Pp. 87. Phila- delphia, 1913. ? Kapillarchemie. Pp. 565. Leipzig, 1909. 4 Grundniss der Kolloidchemie, 2nd edition. Pp. 329. Dresden, 1911. 8 Kolloidchemie. Pp.281. Leipzig, 1912. 344 BOOKS AND CURRENT LITERATURE 345 Two sections of this fourth part are of especial interest to readers of these columns: the paragraph on soil colloids and the discussion of applications to biology. The former is very short (3 pages) and can- not be commended. There are assumed without argument the con- ception of humus as a definite colloidal substance and the idea of the usual existence of colloidal (gel) silica in the soil, from both of which assumptions the reviewer vigorously dissents. Under the applications of colloid chemistry to biology Dr. Taylor discusses the equilibrium between blood and oxygen; enzymes and the colloidal " inorganic fer- ments" of Bredig; the phenomena of bacterial agglutination; and the relations of toxins and antitoxins. To the biologist the treatment of all of these subjects (except, perhaps, the oxygenation of the blood) will seem sketchy and without proper perspective. Dr. Taylor's touch is here far less sure than in his treatment of the subject matter of colloid chemistry proper. One gathers that he has been interested rather in finding biological illustrations of colloid principles than in securing from colloid chemistry aid in the solution of biologic prob- lems. One misses, also, any treatment of the swelling and shrinking of organic gels — of imbibition and the water relations of living matter and the associated non-living tissues. It would be too much to expect the detailed discussion of these matters in a volume of the restricted size and scope of Dr. Taylor's, but it is to be hoped that the examina- tion and presentation of this important and disputed subject will be undertaken soon by some biological colloid chemist or some "colloidal" biologist. In the reviewer's opinion Dr. Taylor's book is to be recommended to biologists not because of what it says of biology but because of what it says of colloid chemistry. Nevertheless it is to be recommended and that most insistently. If it accomplishes nothing else its perusal may induce biologists to refrain from ascribing to convenient "colloidal" actions all phenomena which they fail to understand. — E. E. Free. NOTES AND COMMENT The Editor of Science includes in botany forty of the doctorates con- ferred by American Universities in 1915 (Science 42: 555, 1915), but the following list is intended to comprise the titles which may be con- sidered appropriate for review in botanical journals, of which there are forty-five as against a corrected estimate of thirty-eight in 1914. Some of the titles are comprehensive and indicate subjects which pertain to more than one of the main divisions of botany, but about twenty- three appear to be of a physiological character, seven morphological and embryological, six pathological, five ecological, two taxonomic, and two genetical. The relative interest in the various phases of botany is well illustrated by these figures. It is notable that all of the five doctorates from Washington University are in the botanical list, indicative of the activity of the Missouri Botanical Garden in pro- moting research in the institution with which it is allied. If the experi- ence of previous years is to be taken as an index many of these theses will not reach publication for several months, and may be held for a few years before being put into print. An effort will be made to col- lect information concerning their publication. CORNELL UNIVERSITY Elmer Eugene Barker. Heredity Studies in the Morning Glory {Ipomea purpurea) . Harry Phillip Brown. Growth Studies in Forest Trees. Leonard Amby Maynard. The Fixation of Nitrogen by Sweet Clover. George Adin Osner. Leaf Smut of Timothy. James Kemp Plummer. The Effect of Oxygen and Carbon Dioxide on Nitri- fication and Ammonification in Soils. William Jacob Robbins. Digestion of Starch by Penicillium (Camembertii) . Joseph Rosenbaum. The Phytophthora Disease of Ginseng. Constantine Demetry Shcrbakoff. Fusaria of Potatoes. James Kennith Wilson. Physiological Studies of Bacillus radicola of Soy Bean (Sojus max Piper) and of Factors influencing Nodule Production. UNIVERSITY OF CHICAGO Banna Caroline Aase. Vascular Anatomy of the "Megasporophyll" in Conifers. 34G NOTES AND COMMENT 347 Joseph Stuart Caldwell. A Study of the Effects of Certain Antagonistic Solutions upon the growth of Zea Mays. Hermann Bacher Deutsch. Effect of Light upon the Germination of the Spores of the True Ferns. James Frederick Groves. Life Duration of Seeds. Andrew Henderson Hutchinson. Fertilization in Abies balsamea. Eva Ormenta Schley. Physical and Chemical Changes Involved in Geo-pre- sentation and Geo-reaction. James Palm Stober. A Comparative Study of Winter and Summer Leaves of Various Herbs. v WASHINGTON UNIVERSITY Alva Raymond Davis. Enzyme Action in the Marine Algae. William Harrison Emig. The Occurrence in Nature of Certain Fungi Patho- genic for Man and the Higher Animals. Joseph Charles Gilman. Cabbage Yellows and the Relation of Temperature to Its Occurrence. Melvin Clarence Merrill. The Electrolytic Determination of Exosmosis from the Roots of Plants Subjected to the Action of Various Agents. Lee Oras Overholts. Comparative Studies in the Polyporaceae. UNIVERSITY OF ILLINOIS Demetrius Ion Andronescu. The Physiology of the Pollen of Zea Mays with Special Regard to Vitality. William Leonidas Burlison. Availability of Mineral Phosphates for Plant Nutrition. Fred Weaver Muncie. The Effect of Large Applications of Commercial Ferti- lizers upon Carnations. George Leo Peltier. Parasitic Rhizoctonias in America. THE JOHNS HOPKINS UNIVERSITY Grace Adelaide Dunn. A Study of the Development of Halosaccion ramenl- aceum. Forman Taylor McLean. A Preliminary Study of Climatic Conditions in Maryland as Related to the Growth of Soy Bean Seedlings. John Wesley Shive. A Study of Physiological Balance in Nutrient Media Resulting in a Simplified Culture Solution for Plants. UNIVERSITY OF PENNSYLVANIA John Young Pennypacker. Observations on the Beach Plum. A Study in Plant Variation. David Walter Steckbeck. Comparative Histology and Irritability of Sensi- tive Plants. Heber Wilkinson Youngken. The Comparative Morphology, Taxonomy and Distribution of the Myricaceae of the Eastern United States. 348 NOTES AND COMMENT UNIVERSITY OF CALIFORNIA Richards Morris Holman. The Orientation of Terrestrial Roots with Par- ticular Reference to the Medium in Which They Are Grown. Harry Stanley Yates. The Comparative Histology of Certain California Boletaceae. COLUMBIA UNIVERSITY Arthur Percival Tanberg. Experiments on the Amylase of Aspergillus Orygal. Arthur Waldorf Spjttell Thomas. The Influence of Certain Acids and Salts upon the Activity of Malt Amylase. UNIVERSITY OF NEBRASKA Richard Hans Boerker. Ecological Investigations with Certain Forest Trees. Clarence Jerome Elmore. The Diatoms (Bacillarioideae) of Nebraska. YALE UNIVERSITY Isaac Faust Harris. Chemical and Physiological Studies of the Castor Bean and Soy Bean. Henry Daggett Hooker, Jr. Thermotropism and Hydrotropism. BROWN UNIVERSITY Benjamin Samuel Levine. The Removal of Natural Impurities of Cotton Cloth by Action of Bacteria. CATHOLIC UNIVERSITY Daniel Da Cruz. A Contribution to the Life History of Liliutn tennifolium, HARVARD UNIVERSITY Guilford Bevil Reed. Studies in Plant Oxidases. INDIANA UNIVERSITY Fermen Layton Pickett. Arisaema triphyllum. A Biological Study. UNIVERSITY OF MICHIGAN Adrian John Pieters. The Relation between Vegetative Vigor and Repro- duction in Some Saprolegniaceae. UNIVERSITY OF WISCONSIN Howard Edward Pulling. The Movement of Water in Aerated Soils. D T. MacDougal. NOTES AND COMMENT 349 Miss Lucy E. Cox, of Graystoke Place Training College, London, has written a brief but excellent Experimental Plant Physiology for Beginners (Longmans Green and Company, 1915). The book is de- voted solely to the description and discussion of some 69 experiments, all of which are simple, to the point, and capable of being performed with inexpensive equipment. The experiments are chiefly along the familiar lines but are not without touches of originality, especially with regard to the simplification of apparatus. It is unfortunate that a book for beginners should allude to "the breathing of plants." The usual elementary course in plant physiology is so largely concerned with the mere externals of plant activity that it is well worth while not to get them involved in analogies with the externals of animal functions. Prof. Edward A. White, of Cornell University, has contributed to the Rural Text-Book Series a volume on the Principles of Floricul- ture (Macmillans, 1915). Every phase of commercial floriculture is treated, from the construction and heating of greenhouses to the ship- ment and sale of plants and cut flowers. The proper handling and propagation of plants, the preparation of soil, the proper control of temperatures, and the elimination of disease are among the numerous topics which are treated in a thorough and scientific manner. VOLUME 18 NUMBER 1 JANUARY, 1915 CONTAINING The Relative Transpiration of White Pine Seedlings George P. Burns 1 An Improved Non-Absorbing Porous Cup Atmometer JohnW. Stave 7 A Manometer Method of Determining the Capillary Pull of Soils W. A. Cannon 11 Books and Current Literature 14 Notes and Comment 20 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as seoond-class matter March 9, 1912, at the poet office at Baltimore, Maryland, under the Act of July 16, 1894 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John Jameb Thornber University of Arizona Edgar Nelgon Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates : without covers with covers First 100 Additional 100 First 100 Additional 100 $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. Demonstration Osmoscope This instrument, designed by Prof. Ganong, is so constructed as to exhibit osmotic absorption in visible progress before the eyes of an on-looking class. It is particularly characterized by its rapidity of operation, convenience of manipulation and con- stant readiness for immediate use. The illustration is one-sixth size of the original. Complete, $4.25. One of the new pieces of apparatus described in our new Ganong Apparatus Catalog which will be sent free on request Bausch & Ipmb Optical (o. NEW YORK WAS HINGTON CH1CAC O SAN FRANCISCO LONDON IiOCHESTEn.N.Y. TRANKFOPIT THE POROUS CUP ATMOMETER Is the most simple and efficient instrument ever devised for the measurement of evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all kinds of botanical, agricultural, and horti- cultural operations which require an estimation of the differences in these factors as affecting plant growth in different situations. Its installation requires only the use of a jar, corks and tubing as described in the first article referred to below. The atmometer may also be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata. When immersed in the soil and fed with water by tubing, the atmometer cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the height of the supplying reservoir above the soil. This type of atmometer cup was devised by Dr. Burton E. Livingston, Professor of Plant Physiology in Johns Hopkins University, and its adjustment, operation and scope of usefulness have been treated in the following articles in THE PLANT WORLD: Vol. 10, No. 12, p. 269; Vol. 13, No. 4, p. 79; Vol. 11, No. 1, p. 1; Vol. 13, No. 5, p. Ill; Vol. 11, No. 5, p. 106; Vol. 13, No. 9, p. 220. We are able to supply the atmometer cups in the NATURAL state for use in soil or for cultures, COATED AT THE BASE for use in measurement of evaporation; or COATED AND STAND- ARDIZED for careful climatological and ecological work in which it is desirable to know the value of the readings obtained in terms of the adopted standards which have already been widely used. Our prices for these types are: NATURAL CUPS apiece $ .50. .per 10 $4.00 COATED AT BASE " .60 . . " 5.00 COATED and STANDARDIZED. " 1.00.. " 7.00 SOIL CUPS (seconds) when in stock. " .35.. " 3.00 Cups which have been used will be restandardized at 25 cents each; Reground and standardized at 40 cents. Eastern orders are supplied from Baltimore; western from Tucson. THE PLANT WORLD, Tucson, Arizona The Issue of The Plant World for September, 191 1 (Vol. 14, No. 9) has been exhausted for some time. Owing to the continued demand for complete sets of the magazine this issue Has Been Reprinted and may now be had at the regular price of back numbers, 30 cents each, post paid. THE PLANT WORLD TUCSON, ARIZONA THE F. RONSTADT CO. TUCSON - - ARIZONA AGENTS FOR PLANET JR. GARDEN TOOLS, IMPLEMENTS, PUMPS ENGINES AND WINDMILLS CACTUS CANDY Delicious, fresh from the farm. Per pound 50c. by parcel post. WRIGHTSTON FARMS WRIGHTSTOWN, ARIZONA KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA STUDIES IN SOIL PHYSICS By E. E. FREE Scientist, Bureau of Soils, U. S. Department of Agriculture This series o. papers, which appeared in The Plant World during 1911, has been revised by the author and is now offered in durable pamphlet form Single copies $ .75 Five copies $3.00 This book is the most recent, informing, and suggestive treatment of a field of study which is of vital importance to botany, agriculture, and forestry. PLACE IT IN THE HANDS OF YOUR STUDENTS THE PLANT WORLD TUCSON, ARIZONA EFFICIENCY The Principle3 of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A- TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City * Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA CONTAINING Atmometry and the Porous Cup. Atmometer I. Burton Edward Livingston 21 Natural Reforestation in the Mountains of Northern Idaho Harry B. Humphrey and John Ernst Weaver 31 Books and Current Literature 48 Notes and Comment SO PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. baltimore, md. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July lfi, 1804 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transead Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers WITH covers First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. Demonstration Osmoscope This instrument, designed by Prof. Ganong, is so constructed as to exhibit csmotic absorption in visible progress before the eyes of an on-looking class. It is particularly characterized by its rapidity of operation, convenience of manipulation and con- stant readiness for immediate use. The illustration is one-sixth size of the original. Complete, $4.25. One of the new pieces of apparatus described in our new Ganong Apparatus Catalog which will be sent free on request Bausch & Ipmb Optical (o. NEW YORK WAS HINGTON CHICAGO SAN FRANCISCO london ROCHESTER.. NY. rRANKrottT THE POROUS CUP ATMOMETER Is the most simple and efficient instrument ever devised for the measurement of evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all kinds of botanical, agricultural, and horti- cultural operations which require an estimation of the differences in these factors as affecting plant growth in different situations. Its installation requires only the use of a jar, corks and tubing as described in the first article referred to below. The atmometer may also be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata. When immersed in the soil and fed with water by tubing, the atmometer cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the height of the supplying reservoir above the soil. This type of atmometer cup was devised by Dr. Burton E. Livingston, Professor of Plant Physiology in Johns Hopkins University, and its adjustment, operation and scope of usefulness have been treated in the following articles in THE PLANT WORLD: . Vol. 10, No. 12, p. 269; Vol. 13, No. 4, p. 79; Vol. 11, No. 1, p. 1; Vol. 13, No. 5, p. Ill; Vol. 11, No. 5, p. 106; Vol. 13, No. 9, p. 220. We are able to supply the atmometer cups in the NATURAL state for use in soil or for cultures, COATED AT THE BASE for use in measurement of evaporation; or COATED AND STAND- ARDIZED for careful climatological and ecological work in which it is desirable to know the value of the readings obtained in terms of the adopted standards which have already been widely used. Our prices for these types are: NATURAL CUPS apiece $ .50. .per 10 $4.00 COATED AT BASE " .60 . . " 5.00 COATED and STANDARDIZED. " 1.00. . " 7.00 SOIL CUPS (seconds) when in stock. " .35.. " 3.00 Cups which have been used will be restandardized at 25 cents each; Reground and standardized at 40 cents. Eastern orders are supplied from Baltimore; western from Tucson. THE PLANT WORLD, Tucson, Arizona The Issue of The Plant World for September, 1911 (Vol. 14, No. 9) ' as been exhausted for some time. Owing to the continued demand for complete sets of the magazine this issue Has Been Reprinted and may now be had at the regular price of back numbers, 30 cents each, post paid. THE PLANT WORLD TUCSON, ARIZONA THE F. RONSTADT CO. TUCSON - - ARIZONA AGENTS FOR PLANET JR. GARDEN TOOLS, IMPLEMENTS, PUMPS ENGINES AND WINDMILLS CACTUS CANDY Delicious, fresh from the farm. Per pound 50c. by parcel post. WRIGHTSTON FARMS WRIGHTSTOWN, ARIZONA KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA STUDIES IN SOIL PHYSICS By E. E. FREE Scientist, Bureau of Soils, U. S. Department of Agriculture This series o. papers, which appeared in The Plant World during 1911, has been revised by the author and is now offered in durable pamphlet form Single copies $ .75 Five copies $3.00 This book is the most recent, informing, and suggestive treatment of a field of study which is of vital importance t<~> botany, agriculture, and forestry. PLACE IT IN THE HANDS OF YOUR STUDENTS THE PLANT WORLD TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and teohnlcal publications and a large number of books and catalogues. All are handled on a definite schidule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A. TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Theik Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, ?old a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA VOLUME 18 * NUMBER 3 MARCH, 1915 CONTAINING Atmometry and the Porous Cup Atmometer. II. Burton Edward Livingston 51 Observations in the Colorado Desert S. B. Parish 75 Books and Current Literature 89 Notes and Comment 93 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1804 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers with covers First 100 Additional 100 First 100 Additional 100 Four pages 12.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. ^cs Demonstration Osmoscope This instrument, designed by Prof. Ganong, is so constructed as to exhibit osmotic absorption in visible progress before the eyes of an on-looking class. It is particularly characterized by its rapidity of operation, convenience of manipulation and con- stant readiness for immediate use. The illustration is one-sixth size of the original. Complete, $4.25. One of the new pieces of apparatus described in our new Ganong Apparatus Catalog which will be sent free on request THE POROUS CUP ATMOMETER Is the most simple and efficient instrument ever devised for the measurement of, evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all kinds of botanical, agricultural, and horti- cultural operations which require an estimation of the differences in these factors as affecting plant growth in different situations. Its installation requires only the use of a jar, corks and tubing as described in the first article referred to below. The atmometer may also be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata. When immersed in the soil and fed with water by tubing, the atmometer cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the height of the supplying reservoir above the soil. This type of atmometer cup was devised by Dr. Burton E. Livingston, Professor of Plant Physiology in Johns Hopkins University, and its adjustment, operation and scope of usefulness have been treated in the following articles in THE PLANT WORLD: Vol. 10, No. 12, p. 269; Vol. 13, No. 4, p. 79; Vol. 11, No. 1, p. 1; Vol. 13, No. 5, p. Ill; Vol. 11, No. 5, p. 106; Vol. 13, No. 9, p. 220. We are able to supply the atmometer cups in the NATURAL state for use in soil or for cultures, COATED AT THE BASE for use in measurement of evaporation; or COATED AND STAND- ARDIZED for careful climatological and ecological work in which it is desirable to know the value of the readings obtained in terms of the adopted standards which have already been widely used. Our prices for these types are: NATURAL CUPS apiece $ .50. .per 10 $4.00 COATED AT BASE " .60 . . " 5.00 COATED and STANDARDIZED. " 1.00.. " 7.00 SOIL CUPS (seconds) when in stock. " .35.. " 3.00 Cups which have been used will be restandardized at 25 cents each; Reground and standardized at 40 cents. Eastern orders are supplied from Baltimore; western from Tucson. THE PLANT WORLD, Tucson, Arizona The Issue of The Plant World for September, 1911 (Vol. 14, Xo. 9) has been exhausted for some time. Owing to the continued demand for complete sets of the magazine this issue Has Been Reprinted and may now be had at the regular price of back numbers, 30 cents each, post paid. THE PLANT WORLD TUCSON, ARIZONA THE F. RONSTADT CO. TUCSON - - ARIZONA AGENTS FOR PLANET JR. GARDEN TOOLS, IMPLEMENTS, PUMPS ENGINES AND WINDMILLS CACTUS CANDY Delicious, fresh from the farm. Per pound 50c. by parcel post. WRIGHTSTON FARMS WRIGHTSTOWN, ARIZONA KODAK FINISHING We Guarcuitee to 'get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA STUDIES IN SOIL PHYSICS By E. E. FREE Scientist, Bureau of Soils, U. S. Department of Agriculture This series o. papers, which appeared in The Plant World during 1911, has been revised by the author and is now offered in durable pamphlet form Single copies $ .75 Five copies $3.00 This book is the most recent, informing, and suggestive treatment of a field of study which is of vital importance to botany, agriculture, and forestry. PLACE IT IN THE HANDS OF YOUR STUDENTS THE PLANT WORLD TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definitt schtdule maintaining tho highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A, TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM 1 Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA r A Magazine of General Botany VOLUME 18 NUMBER 4 APRIL, 1915 CONTAINING Atmometry and the Porous Cup Atmometer. III. Burton Edward Livingston 95 The Flora of the Williams Division of the Tusayan National Forest, Virginia A. D. Read 112 Books and Current Literature 124 Notes and Comment 128 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1894 The Plant World A Monthly Magazine of General Botany Established 180." Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers WITH covers First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 Sixteen pages 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; S3. 00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. GANONG ANOXYSCOPE Demonstrates the Necessity of Oxygen to Plant Growth THE PLANT in the left-hand U-tube receives oxygen, the tube- opening being immersed in water. The oxygen in the right-hand U-tube is absorbed by pyrogallic acid, preventing the growth of the contained plant. Price, $4.25 Our catalog of Ganong Botanical Apparatus completely describes 26 different pieces of apparatus. Shall we send^ you a copy ? Bausch & [pmb OPucal ©• NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london IK)CHESTEH. NY. rRANKFORT THE POROUS CUP ATMOMETER Is the most simple and efficient instrument ever devised lor the measurement of evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all kinds of botanical, agricultural, and horti- cultural operations which require an estimation of the differences in these factors as affecting plant growth in different situations. Its installation requires only the use of a jar, corks and tubing as described in the first article referred to below. The atmometer may also be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata. When immersed in the soil and fed with water by tubing, the atmometer cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the height of the supplying reservoir above the soil. This type of atmometer cup was devised by Dr. Burton E. Livingston, Professor of Plant Physiology in Johns Hopkins University, and its adjustment, operation and scope of usefulness have been treated in the following articles in THE PLANT WORLD: Vol. 10, No. 12, p. 269; Vol. 13, No. 4, p. 79; Vol. 11, No. 1, p. 1; Vol. 13, No. 5, p. Ill; Vol. 11, No. 5, p. 106; Vol. 13, No. 9, p. 220. We are able to supply the atmometer cups in the NATURAL state for use in soil or for cultures, COATED AT THE BASE for use in measurement of evaporation; or COATED AND STAND- ARDIZED for careful climatological and ecological work in which it is desirable to know the value of the readings obtained in terms of the adopted standards which have already been widely used. Our prices for these types are: NATURAL CUPS apiece $ .50. .per 10 $4.00 COATED AT BASE " .60 . . " 5.00 COATED and STANDARDIZED. " 1.00. . " 7.00 SOIL CUPS (seconds) when in stock. " .35.. " 3.00 Cups which have been used will be restandardized at 25 cents each; Reground and standardized at 40 cents. Eastern orders are supplied from Baltimore; western from Tucson. THE PLANT WORLD Tucson, Arizona BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Reeky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - • - $3.00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - 1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121. pp. - 1.25 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map ----------.30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - - - - - - - - - - - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA THE F. RONSTADT CO. TUCSON - - ARIZONA AGENTS FOR PLANET JR. GARDEN TOOLS, IMPLEMENTS, PUMPS ENGINES AND WINDMILLS A YOSEMITE FLORA BY HARVEY MONROE HALL and CARLOTTA CASE HALL A descriptive account of the Ferns and Flowering plants, including the Trees, of the Yosemite National Park, with easy keys for their identification; covering most of the species of the Sierra Nevada Mountains. 282 pages. Illustrated with 11 plates and 170 figures in the text. Pocket size. Attractively bound in semi-flexible leather. Postpaid, $2.00. PAUL ELDER & COMPANY, Publishers 239 GRANT AVENUE - - - SAN FRANCISCO KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 F'our Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species §4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. AH are handled on a definite schtdule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road. Baltimore, Md., U. S. A. TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA The Plant World A Magazine of General Botany VOLUME 18 NUMBER 5 MAY, 19 15 A CONTAINING J Notes on the Relations Between the Floras of Subantarctic America and New Zealand. 129 Atmometry and the Porous Cup Atmometer. IV. 143 150 153 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA »f 1 1 1 — il A.tn( Inlirlfi 1 SQ1 The Plant World A Monthly Magazine of General Botany- Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding . Loma Linda, California John James Thornber University of Arizona Edgar Nelgon Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: WITHOUT COVERS WITH COVERS First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 $4.68 6.32 $1.72 Eight pages 2.20 2.00 6.80 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. METABOLISM THE GANONG WATER CULTURE SUPPORT is correct in principle and simple in operation. The plants are securely supported both above and below the seeds by the two aluminum disks whose perforations are closed with paraffin, proper openings being made to accommodate the seedlings. A double screw keeps the disks parallel and serves to regulate the distance between them. An opaque sleeve keeps light from the tumbler containing the culture solution. Professor Ganong grew ten corn plants in this Support to a height of four feet, the mass of healthy roots filling the tumbler as a mold. Price, complete, $1.10 Our catalog of Ganong Botanical Apparatus describes in detail 26 different pieces of apparatus. Every teacher should have a copy. Bausch £5" Ipmb Optical (o. NCW YORK WASHINGTON CHICAGO SAN FRANCISCO london &OCH ESTER., NY. ™ANKFORT THE ATMOMETER Is well known as a simple and efficient instrument for the measurement of evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all laboratory and field work that requires an estimation of the differences in these factors as affecting plant activities in different situations. The Atmometer cup may be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata; for making Pfeffer osmometer cells; and for ordi- nary pressure filters. When imbedded in the soil and fed with water by tubing, the cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the nature of the soil and by the height of the cup above the supplying reservoir. The Atmometer was devised by Dr. B. E. Livingston, Professor of Plant Physiology in The Johns Hopkins University, and its adjustment, operation, and scope of usefulness have been treated in the following articles in The Plant World: Vol. 10, No. 12, p. 269 Vol. 13, No. 5, p. Ill Vol. 18, No. 2, p. 21 Vol. 11, No. 1, p. 1 Vol. 13, No. 9, p. 220 Vol. 18, No. 3, p. 51 Vol. 11, No. 5, p. 106 Vol. 14, No. 4, p. 96 Vol. 18, No. 4, p. 95 Vol. 13, No. 4, p. 79 Vol. 18, No. 1, p. 7 Vol. 18, No. 5, p. 143 The Plant World now supplies the following types of Atmometer Cups: NATURAL CUPS. In the well-known cylindrical form, with smoothly ground surface. For general purposes. Apiece $.50 per ten $4.00 COATED CUPS. Glazed at base, with permanent numbering. Apiece $.60 per ten $5.00 STANDARDIZED CUPS. Numbered, shellacked at base and calibrated to Livingston cylindrical standard. Apiece $1.00 per ten $7.00 STANDARDIZED CUPS. Numbered, glazed at base and calibrated. Apiece $1.15 per ten $8.00 INSOLUBLE CUPS. Of same form as the preceding, but made of specially resistent material. Numbered and standardized. Especially valuable as per- manent standards for those intending to do their own standardizing. Apiece $2.00 per ten $18.00 SOIL CUPS. Used cups unsuitable for atmometers but still just as good for auto-irrigators. When in stock. Apiece $.35 per ten $3.00 Cups which have been used will be restandardized for 25 cents each; reground and standardized for 40 cents. THE PLANT WORLD .'. TUCSON, ARIZONA BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - - - - -$3.00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - 1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1.25 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper, 25 pp., illustrated, map -"- - - - - - - - -.30 An Improved Non- Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA THE F. RONSTADT CO. TUCSON - - ARIZONA AGENTS FOR PLANET JR. GARDEN TOOLS, IMPLEMENTS, PUMPS ENGINES AND WINDMILLS A YOSEMITE FLORA BY HARVEY MONROE HALL and CARLOTTA CASE HALL A descriptive account of the Ferns and Flowering plants, including the Trees, of the Yosemite National Park, with easy keys for their identification; covering most of the species of the Sierra Nevada Mountains. 282 pages. Illustrated with 11 plates and 170 figures in the text. Pocket size. Attractively bound in semi-flexible leather. Postpaid, $2.00. PAUL ELDER & COMPANY, Publishers 239 GRANT AVENUE - - - SAN FRANCISCO KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4-00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA $10.00 EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and teohnlcal publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of mechanloal workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A- TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Theie Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM 1 Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA A Magazine of General Botany VOLUME 18 NUMBER 6 JUNE, 19 15 CONTAINING \^ Some Remarks on the Desert Vegetation of America. Ove Paulsen 155 The Antizymotic Action of a Harmful Soil Constituent: Salicylic Aldehyde and Mannite. J. J. Skinner 162 Books and Current Literature. 168 Notes and Comment 176 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 10, 1894 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spai.dino Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers with covers First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 80.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. FOR FIELD EXCURSIONS A PORTABLE MICROSCOPE is required that is really portable and sacrifices none of the efficiency of the bulkier instruments. Microscope APS has all the adjustments of our laboratory instruments, with all their accuracy and convenience of manipulation — and the cost is practically the same. APS 6 in carrying case weighs 9 lbs., 3 oz. The'carrying case is less than one-half the size of a regular microscope case. The folding base is the only collap- sible feature and there is no inclination joint. APS has the lever side fine adjustment (two heads) which is simple in design and responds instantly. It ceases to operate when the objective touches the specimen. Microscope APS 6 Equipped with screw substage having iris diaphragm with protective locking device, Abbe condenser, 1.20 N.A., in iris mount; 5 X and 10 X eyepieces; 16 mm and 4 mm objectives on dust-proof nosepiece; com- plete in carrying case - - - $45.00 Bausch & Jpttib Optical (p. NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london &0CHESTEn,N.Y ™ankfort THE ATMOMETER Is well known as a simple and efficient instrument for the measurement of evaporation. Its readings are a measure of the combined effect of humidity, temperature, and wind, and as such are of great value in all laboratory and field work that requires an estimation of the differences in these factors as affecting plant activities in different situations. The Atmometer cup may be used to maintain high humidities in experimental work; to provide a constantly moist surface for germinating spores or growing algae, fungi and protonemata; for making Pfeffer osmometer cells; and for ordi- nary pressure filters. When imbedded in the soil and fed with water by tubing, the cup is capable of maintaining constant degrees of soil moisture, either in the open or in pots and greenhouses, the degree of moistness being determined by the nature of the soil and by the height of the cup above the supplying reservoir. The Atmometer was devised by Dr. B. E. Livingston, Professor of Plant Physiology in The Johns Hopkins University, and its adjustment, operation, and scope of usefulness have been treated in the following articles in The Plant World: Vol. 10, No. 12, p. 269 Vol. 13, No. 5, p. Ill Vol. 18, No. 2, p. 21 Vol. 11, No. l,p. 1 Vol. 13, No. 9, p. 220 Vol. 18, No. 3, p. 51 Vol. 11, No. 5, p. 106 Vol. 14, No. 4, p. 96 Vol. 18, No. 4, p. 95 Vol. 13, No. 4, p. 79 Vol. 18, No. 1, p. 7 Vol. 18, No. 5, p. 143 The Plant World now supplies the following types of Atmometer Cups: NATURAL CUPS. In the well-known cylindrical form, with smoothly ground surface. For general purposes. Apiece $.50 per ten $4.00 COATED CUPS. Glazed at base, with permanent numbering. Apiece $.60 per ten $5.00 STANDARDIZED CUPS. Numbered, shellacked at base and calibrated to Livingston cylindrical standard. Apiece $1.00 per ten $7.00 STANDARDIZED CUPS. Numbered, glazed at base and calibrated. Apiece $1.15 per ten $8.00 INSOLUBLE CUPS. Of same form as the preceding, but made of specially resistent material. Numbered and standardized. Especially valuable as per- manent standards for those intending to do their own standardizing. Apiece $2.00 per ten $18.00 SOIL CUPS. Used cups unsuitable for atmometers but still just as good for auto-irrigators. When in stock. Apiece $.35 per ten $3.00 Cups which have been used will be restandardized for 25 cents each; reground and standardized for 40 cents. THE PLANT WORLD .\ TUCSON, ARIZONA KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definite schidule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A. THE AUTO-IRRIGATOR A BOON TO EVERY GROWER OF POTTED PLANTS T iHE Auto-Irrigator is a simple device for placing water in the soil of pots in quantities as needed. Is abolishes the watering nuisance, and maintains a practically constant soil moisture, at any amount from saturation nearly to dryness, according to the adjustment of the instru- ment. It requires attention only two or three times a month, and its use results in a great improvement of plant growth as compared with sporadic surface watering. The essential feature of the Auto-Irrigator is a porous clay cup such as is used in the Atmometer. Its installation requires the use of a stopper, tubing, and a vessel to contain the water supply. The degree of soil moisture maintained is determined by the height of the reservoir in relation to the pot. The length of time during which the apparatus may go without attention depends chiefly on the size of the reservoir. It may be used in pairs or in groups, and operates equally well in pots, in benches, or in outdoor beds. Full instructions for installing and oper- ating will be furnished on request or with orders. For further information regarding the use of the Auto-Irrigator see: Plant World, Vol. 11, pp. 39-40, February. 1908. Plant World, Vol. 13, pp. 220-227, September, 1910. New Cups for Auto-Irrigator: $.50 each, $4.00 per 10. Seconds (cups which have already seen use as atmometers): $.35 each, $3.00 per 10. THE PLANT WORLD Tucson, Arizona NON-ABSORBING ATMOMETER MOUNTINGS /7ti\ B B Don't Let Rain Enter Your Atmometers and Spoil Your Results The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for •transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona Living Plants and their Properties By J. G. Arthur and D. T. MacDougal A series of lectures on nutrition, irritability, and other fundamental subjects in plant physiology. This is not a text-book, but is excellent matter for side reading and should be in every educational institution and library. 234 Pages, Illustrated Price, $1.25 Bibliography of Evaporation By Grace J. Livingston A complete bibliography of evaporation, embracing the literature of all lan- guages from 1670 to 1908, with the titles arranged in chronological order. The full and discriminating annotations accompanying each title form the most val- uable feature of this work, especially to those who are interested in the bear- ings of evaporation on agriculture, forestry, and plant and animal ecology. 121 Pages Price, $1.25 THE PLANT WORLD, TUCSON, ARIZONA The Vaporimeter Is an instrument for the measurement of evaporation, devised by Dr. E. N. Transeau, of the Eastern Illinois State Normal School. The essential feature of the device is a slender, elongated cup. glazed over the lower half. Its in- stallation is extremely simple, as no stopper and tubing are necessary, and its successful performance recommends it for all classes of field and laboratory use. For illustration and full description see Botanical Gazette, Vol. 49, pp. 459-460, June, 1910. Price, each $1.20 Per ten, $10.00 The Non-Soluble Atmometer A new type of atmometer manufactured for us in Germany from carefully purified materials, so as to contain practically no soluble matter of any kind. The cup is somewhat smaller than the other types of atmometer which we handle, and is glazed at the base for convenience in manipulation. This in- strument is recommended for long series of readings in which re-standardization is impractical, as well as for short series in which a high degree of accuracy is required. Price, each $2.00 Per ten, $16.00 THE PLANT WORLD, TUCSON, ARIZONA STUDIES IN SOIL PHYSICS By E. E. FREE Scientist. Bureau of Soils, U. S. Department of Agriculture This series o. papers, which appeared in The Plant World during 1911, has been revised by the author and is now oTered in durable pamphlet form Single copies $ .75 Five copies S3.00 This book is the most recent, informing, and suggestive treatment of a field of study which is of vital importance rn botany, agriculture, and forestry. PLACE IT IN THE HANDS OF YOUR STUDENTS THE PLANT WORLD TUCSON, ARIZONA Automatic Transpiration Apparatus The apparatus devised by Dr. E. N. Transeau for the graphic recording of transpiration rate has been placed in our hands for sale. This apparatus was described and illustrated in Botanical Gazette, Vol. 52. pp. 54-60. Full particulars and prices on application. THE PLANT WORLD, TUCSON, ARIZONA Special Clearance Sale of Back Numbers Five back numbers of The Plant World, of our own choosing, will be sent post free for 60 cents. Our regular price would be SI. 50. The issues available for this offer are generously illustrated, and especially rich in articles on plant geography, ecological botany, and travels, not to mention a wide range of other subjects. Any preference of the purchaser for particular numbers, or for a particular class of articles, will be honored as far as possible. THE PLANT WORLD, TUCSON, ARIZONA BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in co!or - - - - - - - - - $3.00 Living Plants and thiir Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - - -■ - - 1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1.25 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colo-ado River, by D. T. MacDougal. Paper 25 pp., illustrated, map - - - - - - - - - -.30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - - - - - - - - - - - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid seiious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World .'. ,\ Tucson, Arizona A YOSEMITE FLORA BY HARVEY MONROE HALL and CARLOTTA CASE HALL A descriptive account of the Ferns and Flowering plants, including the Trees, of the Yosemite National Park, with easy keys for their identification; covering most of the species of the Sierra Nevada Mountains. 282 pages. Illustrated with 11 plates and 170 figures in the text. Pocket size. Attractively bound in semi-flexible leather. Postpaid, $2.00. PAUL ELDER & COMPANY, Publishers 239 GRANT AVENUE - - - SAN FRANCISCO TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM 1 Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA Th Plant World A Magazine of General Botany VOLUME 18 NUMBER 7 JULY, 1915 CONTAINING Vegetation of the Brazos Canyon, New Mexico. Paul C. Standley.. .... 179 Further Observations on the Origin of the Galapagos Islands 192 .... 201 .... 204 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 10, 1H'J4 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory . Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelgon Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers WITH COVERS First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. The Demonstration Root-Pressure Manometer designed by Professor Ganong for demonstrating exudation or bleed- ing pressure, is correct in principle and gives striking results. It is Correct in Principle BECAUSE, unlike the stout mer- curial manometer tube generally used, the total volume of this Manometer falls well within the exudation capacity of all ordinary plants. In consequence, it Gives Striking Results BECAUSE the true pressure is indicated. The index tube is long- enough to indicate an atmosphere of pressure. A meter rule is carried in a clamp for reading the height of the mercury column. Finally, the instrument is Simple and Convenient BECAUSE, once filled, it can always be kept ready for immedi- ate use. The price includes all connections and 10 cc of mercurv $4.75 Bausch & Ipmb OPtical ©• NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london &oCHESTEn,N.Y. rRANKFORT Leading American Manufacturers of Microscopes, Projection Apparatus (Balopticonsi. Photo- graphic Lenses, Engineering Instruments, Binoculars and other high grade Optical Products. NON-ABSORBING ATMOMETER MOUNTINGS (ft\ B Don't Let Rain Enter Your Atmometers and Spoil Your Results The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and teohnlcal publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road, Baltimore, Md., U. S. A. BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - - - --$3. 00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - - - - - -1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1..25 Atmometry and the Porous Cup Atmometer, by B. E. Livingston. Paper, 64 pp., illustrated - - - - - - - - - - .75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper, 25 pp., illustrated, map - - _ ______ 30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - - - - - - - ' - - - - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - ' - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid serious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World .'. .". Tucson, Arizona Automatic Transpiration Apparatus The apparatus devised by Dr. E. X. Transeau for the graphic recording of transpiration rate has been placed in our hands for sale. This apparatus was described and illustrated in Botanical Gazette. Vol. 52, pp. 54-60. Full particulars and prices on application. THE PLANT WORLD, TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co, Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA A. « A Magazine of General Botany VOLUME 18 NUMBER 8 AUGUST, 1915 CONTAINING The Dunes of Lake Michigan. Theo. J. Stomps 205 Notes on the Dissemination of Virginia Creeper Seeds by English Sparrows. Bartle T. Harvey 217 Books and Current Literature 220 Notes and Comment 225 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON. ARIZONA - * Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 1 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelgon Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: WITHOUT COVERS WITH COVERS First 100 Additional 100 First 100 Additional 100 Four pages 52.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can npt be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. The Bausch & Lomb Auxograph For Demonstrating and Recording Plant Growth is a practical instrument for educational use which possesses the following advantages: Prominence of Record Ease and Simplicity of Adjustment Comparative Accuracy Durability Ready Portability Principle and Operation Perfectly Apparent PRICE, complete, $25.00 Ask for Catalog Bausch & [pmb Optical (o. NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london ftOCHESTEIl. NY. ™ANKFORT Leading American Makers of Microscopes, Projection Apparatus (Balopticons), Photographic Lenses, Binoculars and other High Grade Optical Products NON-ABSORBING ATMOMETER MOUNTINGS B B Don't Let Rain Enter Your Atmometers and Spoil Your Results The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specif}^ the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 York Road. Baltimore. Md.. U. S. A- BOTANICAL BOOKS* AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color ' - $3.00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - -1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1.25 Atmometry and the Porous Cup Atmometer, by B. E. Livingston. Paper, 64 pp., illustrated - - - - -.75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map - - - - .30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid serious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World ucson. Ariz ona THE BELLANI PLATE THE PLANT WORLD The Bellani Plate is a new type of Atmome- ter presenting a flat horizontal evaporating sur- face 7.5 cm. in diameter, attached to a glazed hemispherical funnel. These instruments are calibrated to a standard plate of the same type. As compared with a free water surface this Plate presents all the advantages of a fixed and un- changing evaporating surface which is not liable to accidental disturbance. Each $2.00 Per Ten $18.00 TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA A Magazine of General Botany VOLUME 18 NUMBER 9 SEPTEMBER, 1915 CONTAINING A Study of the Root- Systems of Prairie Plants of Southeastern Washing- ton. I. John Ernst Weaver 227 A Relative Score Method of Recording Comparisons of Plant Condition and other Unmeasured Characters. E. E. Free 249 Books and Current Literature 257 Notes and Comment 259 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Grebnmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1894 The Plant World A Monthly Magazine of General Botany Establishedl897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur HarrIs Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: WITHOUT COVERS WITH COVERS First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 Sixteen pages 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. POTOMETER for demonstrating the effect on transpiration of varying external conditions The rate of transpiration is indicated by a bubble in the graduated tube, the bubble moving forward as the plant absorbs water. Opening the stop-cock sends the bubble back to its starting point, again ready for use. For comparative records, one takes the distance traversed by the bubble in a given time, or the time it requires to travel a given distance. This instrument, like all of those designed by Professor Ganong, is cor- rect in principle and simple in operation. Our Catalog of Ganong Botanical Apparatus contains much authoritative information. It describes at length 26 different pieces of appa- ratus for use in Plant Physiology. It is free on request. Bausch £5 Ipmb Optical (5. HCW YORK WASHINGTON CHICAGO SAN FRANCISCO london F10CHESTEH,N.Y. ™ankfort Leading American Makers of Microscopes, Projection Apparatus (Balopticons), Photographic Lenses, Binoculars and other High Grade Optical Products NON-ABSORBING ATMOMETER MOUNTINGS B Don't Let Rain Enter Your Atmometers and Spoil Your Results The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guarantee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of meohanloal workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 3419-2431 Greenmount Ave., Baltimore. Md., U. S. A BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - - - - -$3.00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - 1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1.25 Atmometry and the Porous Cup Atmometer, by B. E Livingston. Paper, 64 pp., illustrated _ _ _ _ 75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - .75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map - - - - - - - - - -.30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. - - - - - - - .20 Hybridization of "Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid seiious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World ucson, Ariz ona THE BELLANI PLATE THE PLANT WORLD The Bellani Plate is a new type of Atmome- ter presenting a flat horizontal evaporating sur- face 7.5 cm. in diameter, attached to a glazed hemispherical funnel. These instruments are calibrated to a standard plate of the same type. As compared with a free water surface this Plate presents all the advantages of a fixed and un- changing evaporating surface which is not liable to accidental disturbance. Each $2.00 Per Ten $18.00 TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL — »^— ^— llll «^— H— — | | Ml I.I —^M^— GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA i A Magazine of General Botany VOLUME18 i£ NUMBER 10 OCTOBER, 1915 CONTAINING Acid Accumulation and Destruction in Large Succulents. Esmond R. Long 261 A Study of the Root-Systems of Prairie Plants of Southeastern Washing- ton. II. John Ernst Weaver 273 Books and Current Literature 293 Notes and Comment 294 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmotjnt Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1894 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembl? MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peircb Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory Volnet Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers with covers First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. Transpirograph FOR Demonstration and Research To record the rate of trans- piration the plant is placed on a balanced scale-pan. As it loses water it is raised, touch- ing a release which closes an electric circuit. An electro- magnet then releases a 1-gram ball weight (200 of which are carried in a tube) which drops into the scale-pan. The bal- ance is restored and the pro- cess repeated. Each 1-gram loss is recorded on a drum driven by clock- work. It is possible to read directly from the record the number of minutes required for the plant to lose one gram of water. The apparatus pro- vides for a continuous record of seven days duration, one adjustment per day being re- quired. Write for Catalog of Botanical Apparatus Bausch £5 Ipmb OPtical ©• NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london £OCHESTEIl,N.Y. ™ankfor.t Leading American Makers of Microscopes, Projection Apparatus (Balopticons), Photographic Lenses, Binoculars and other High Grade Optical Products NON-ABSORBING ATMOMETER MOUNTINGS B Don't Let Rain Enter Your Atmometers and Spoil Your Results jm The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guarantee to get the best possible results your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA from Bargain Lots of Cacti No. 1 Four Species Including Mamillaria, Echinocereus, Platopuntia, andCylin- dropuntia. $1.00 No. 2 Four Species of Opuntia Not duplicating the above; and including two Platopuntias and two Cylindropuntias. $1.00 No. 3 Four Species Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. $2.50 No. 4 Twelve Species Being a combination of the above three lots. $4.00 No. 5 Twelve Species of Opuntia Comprising Lot 2 and eight other species, including Opuntia Bigelovii. $4.00 No. 6 Twenty Species A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA $10.00 EFFICIENCY The Principles of Scientific Shop Management are Applied by us Printing Business to the We manufacture this Journal. In addition we produce 25 other scientific and teohnlcal publications and a large number of books and catalogues. All are bandied on a definite schedule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 Greenmount Ave., Baltimore, Md. , U. S. A. BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - - - --$3.00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - - - - - - 1 . 25 Bibliography of Evaporation, by Grace J.Livingston. Paper, 121pp. - 1.25 Atmometry and the Porous Cup Atmometer, by B. E Livingston. Paper, 64 pp., illustrated - - - - - - - - - -.75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map - - -.- - - - - - -.30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. ----------- - - .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can ba made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid serious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World Tucson, Arizona THE BELLANI PLATE The Bellani Plate is a new type of Atmome- ter presenting a flat horizontal evaporating sur- face 7.5 cm. in diameter, attached to a glazed hemispherical funnel. These instruments are calibrated to a standard plate of the same type. As compared with a free water surface this Plate presents all the advantages of a fixed and un- changing evaporating surface which is not liable to accidental disturbance. Each $2.00 Per Ten $18.00 THE PLANT WORLD TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA A Magazine of General Botany VOLUME 18 NUMBER 11 NOVEMBER, 1915 CONTAINING An Investigation of the Causes of Autonomic Movements in Succulent Plants. I. Edith Bellamy Shreve 297 A Useful Drawing Camera. Richard M. Holman 313 Books and Current Literature 317 Notes and Comment 319 PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Ave. BALTIMORE, MD. EDITORIAL OFFICE TUCSON. ARIZONA Entered as seoond-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1894 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shkeve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Llotd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peirce Stanford University Charles Louis Pollard Staten Island Association Herbert Maule Richards Columbia University Forrest Shreve Desert Laboratory . Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers with covers First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant Wokld, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2413-21 York Road, Baltimore, Md., or to The Plant Would, Tucson, Arizona. Grand Prix Awarded Bausch & Lomb Microscopes The International Jury of Award, Panama-Pacific Exposition, has conferred the Grand Prix upon Bausch & Lomb Micro- scope. This award stamps these instruments as the best- superior in design and construction — optically and mechani- cally. Model F 4, illustrated, is a favorite instrument in the bio- logical laboratory. The long curved arm leaves the stage entirely free for manipulation of the specimen. The stage is 4 x 4 inches, completely covered with vulcanized rubber, except at the point of attachment. The fine adjustment is of our lever type, which is simple and durable. It ceases to operate when the objective touches the specimen. Equipped with 16 and 4 mm objectives on dustproof, revolving nosepiece; 5X and 10X eyepieces, all in polished case with lock and key. $33.00 Write for Literature Bausch £5 [omb Optical (p. NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london ROCHESTER, N.Y ™ANKFO*T Leading American Makers of Microscopes, Projection Apparatus (Balopticons), Photographic Lenses, Binoculars and other High Grade Optical Products NON-ABSORBING ATMOMETER MOUNTINGS rfr\ D B B Don't Let Rain Enter Your Atmometers and Spoil Your Results The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guara?itcc to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.8© Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- 1 issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definit* schtdult maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 Greenmount Ave., Baltimore, Md.. U. S. A. BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - _ _'. -$3 00 Lning Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - - - _ ---125 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1 .25 Atmometry and the Porous Cup Atmometer, by B. E. Livingston. Paper, 64 pp., illustrated --------- 1 75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map - - - - - _ _ _ _ -.30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper 4pp. -----------.. .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. -. - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid serious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World Tucson, Arizona THE BELLANI PLATE THE PLANT WORLD The Bellani Plate is a new type of Atmome- ter presenting a flat horizontal evaporating sur- face 7.5 cm. in diameter, attached to a glazed hemispherical funnel. These instruments are calibrated to a standard plate of the same type. As compared with a free water surface this Plate presents all the advantages of a fixed and un- changing evaporating surface which is not liable to accidental disturbance. Each $2.00 Per Ten $18.00 TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, eold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA f y^ A Magazine of General Botany ,""J ! VOLUME 18 NUMBER 12 DECEMBER, 1915 CONTAINING Effect of Vanillin as a Soil Constituent. J. J. Skinner 321 An Investigation of the Causes of Autonomic Movements in Succulent Plants. II. Edith Bellamy Shreve 331 Books and Current Literature 344 Notes and Comment 346" PUBLISHED MONTHLY OFFICE OF PUBLICATION 2419-21 Greenmount Avb. BALTIMORE, MD. EDITORIAL OFFICE TUCSON, ARIZONA V Entered as second-class matter March 9, 1912, at the post office at Baltimore, Maryland, under the Act of July 16, 1804 The Plant World A Monthly Magazine of General Botany Established 1897 Edited by Forrest Shreve Published by The Plant World Association COMPOSED OF THE FOLLOWING MEMBERS: Joseph Charles Arthur Purdue University Otis William Caldwell University of Chicago William Austin Cannon Desert Laboratory Charles Stuart Gager Brooklyn Botanic Garden J. Arthur Harris Station for Experimental Evolution Burton Edward Livingston Johns Hopkins University Francis Ernest Lloyd McGill University Daniel Trembly MacDougal Carnegie Institution of Washington James Bertram Overton University of Wisconsin George James Peircb Stanford University Charles Louis Pollard Staten Island Association Herbert Maulb Richards Columbia University Forrest Shreve Desert Laboratory Volney Morgan Spalding Loma Linda, California John James Thornber University of Arizona Edgar Nelson Transeau Eastern Illinois Normal School All manuscripts submitted for publication should be type-written and in good order. Galley proof is submitted to the author, who should return it as early as possible to the Editor. Reprints should be ordered on a blank for that purpose which accompanies the galley proofs. Reprints will be supplied at the following rates: without covers WITH COVERS First 100 Additional 100 First 100 Additional 100 Four pages $2.68 4.32 4.80 $0.72 1.20 2.00 $4.68 6.32 6.80 $1.72 Eight pages 2.20 3.00 Express or postage is extra. Advertising rates will be furnished on application. Address all correspondence regarding contributions and reprints, and all books for review to The Editor, The Plant World, Tucson, Arizona. The subscription price is $2.50 per annum in the United States, its overseas dependencies, and Canada and Mexico; $3.00 to other countries. Single copies are 30 cents each. Volumes 1 to 7 inclusive can not be supplied; Volumes 10 and 11 can be supplied incomplete; Volumes 8 and 9, and Volumes 12 to 17 are $2.50 each. Missing numbers lost in the mails will be replaced gratis only when notice is received within one month of date of issue. Make all remittances payable to The Plant World. Address all correspond- ence regarding subscriptions, discontinuances, changes of address, back num- bers and early volumes to: The Waverly Press, Williams & Wilkins Co., 2419-21 York Road, Baltimore, Md., or to The Plant World, Tucson, Arizona. LARGE DISSECTING STAND A New Design which meets every requirement by reason of its large size and wide range of usefulness. Accommodates Interchangeably a Binocular Micro- scope Body, Monocular Erecting Body, using medium high-power objectives, or a Simple Lens in jointed arm — all focused by rack and pinion. Stage, 8x7 inches (205x180 mm.), is provided with glass and metal plates 4j inches (119 mm.) in diameter, and with adjustable back-ground stops beneath. The construction is unusually rigid and durable. CIRCULAR ON REQUEST Bausch £5 Ipmb OPtica^ ®- NEW YORK WASHINGTON CHICAGO SAN FRANCISCO london ftOCHESTEft, NY. ™ANKro,vr Leading American Makers of Microscopes, Projection Lanterns (Balopticons), Photographic Lenses, Engineering Instru- ments, Stereo Prism Binoculars and other High Grade Optical Products NON-ABSORBING ATMOMETER MOUNTINGS Don't Let Rain Enter Your Atmometers and Spoil Your Results B The mounting which is illustrated here oper- ates so as to allow the loss of water by the Atmometer cup in the usual manner, and also to prevent, almost completely, the ab- sorption of rain by the cup and the conse- quent backing of water into the reservoir. These mountings are made according to the specifications of J. W. Shive and are de- scribed in detail in The Plant World 18, pp. 7-10, Jan. 1915. The entire mounting is self-contained and not readily put out of adjustment. It is furnished complete, with quart reservoir, mercury, and caps. Each instrument is packed in a neat wooden box, ready for transportation to the field. In ordering please specify the type of At- mometer cup that will be used with it. Each $5.00 Per Ten $45.00 THE PLANT WORLD, Tucson, Arizona KODAK FINISHING We Guara?itee to get the best possible results from your exposures. Mail orders attended to promptly. Catalogue and Price List Free The Smith Sporting Goods Company TUCSON, ARIZONA Bargain Lots of Cacti No. 1 Four Species $1.00 Including Mamillaria, Echinocereus, Platopuntia, and Cylin- dropuntia. No. 2 Four Species of Opuntia $1.00 Not duplicating the above; and including two Platopuntias and two Cylindropuntias. No. 3 Four Species $2.50 Contains no Opuntias and no duplicates with Lots 1 and 2. Includes Cereus giganteus. No. 4 Twelve Species $4.00 Being a combination of the above three lots. No. 5 Twelve Species of Opuntia $4.00 Comprising Lot 2 and eight other species, including Opuntia Bigelovii. No. 6 Twenty Species $10.00 A fine diversified lot and a great bargain. Includes Cereus giganteus, Echinocactus Wislizeni and Echinocereus rigid- issimus. THE PLANT WORLD, TUCSON, ARIZONA EFFICIENCY The Principles of Scientific Shop Management are Applied by us to the Printing Business We manufacture this Journal. In addition we produce 25 other scientific and technical publications and a large number of books and catalogues. All are handled on a definite schedule maintaining the highest standard of mechanical workmanship. WAVERLY PRESS WILLIAMS & WILKINS COMPANY 2419-2421 Greenmount Ave, Baltimore, Md., U. S. A. BOTANICAL BOOKS AND SEPARATES OF JOURNAL ARTICLES Rocky Mountain Flowers, by F. E. and E. S. Clements. Cloth, 400 pp., profusely illustrated in color - - - - - - - - ' - $3 . 00 Living Plants and their Properties, by J. C. Arthur and D. T. MacDougal. Cloth, 234 pp., illustrated - - - - 1.25 Bibliography of Evaporation, by Grace J. Livingston. Paper, 121 pp. - 1.25 Atmometry and the Porous Cup Atmometer, by B. E Livingston. Paper, 64 pp., illustrated - - - - - - - - - - .75 Studies in Soil Physics, by E. E. Free. Paper, 42 pp. - - - - . 75 The Deserts of Egypt, by D. T. MacDougal. Paper, 27 pp., illustrated - .40 The Desert Basins of the Colorado River, by D. T. MacDougal. Paper 25 pp., illustrated, map --_ ______ .30 An Improved Non-Absorbing Porous Cup Atmometer, by J. W. Shive. Paper, 4 pp. ---------__ _ _ .20 Hybridization of Wild Plants, by D. T. MacDougal. Paper, 16 pp. - - .30 THE PLANT WORLD TUCSON, ARIZONA Pans for Retaining Power of Soils The results of different workers can be made comparable by the use of uniform pans and a uniform method for the determination of the maximum water-retaining power of soils. The pans here shown are of heavy copper sheet, with perforated bottom and with wall 1 cm. high. They are 11.5 cm. in diameter and hold approximately 100 cc. of soil, an amount small enough for easy handling and large enough to avoid serious errors in weighing. A circle of thin filter paper should be placed in the bottom. See Hilgard's "Soils," p. 209. Each $1.25; Per Ten $10.00 The Plant World Tucson. Arizona THE BELLANI PLATE THE PLANT WORLD The Bellani Plate is a new type of Atmome- ter presenting a flat horizontal evaporating sur- face 7.5 cm. in diameter, attached to a glazed hemispherical funnel. These instruments are calibrated to a standard plate of the same type. As compared with a free water surface this Plate presents all the advantages of a fixed and un- changing evaporating surface which is not liable to accidental disturbance. Each $2.00 Per Ten $18.00 TUCSON, ARIZONA TUCSON IS THE METROPOLIS OF ARIZONA! Finest Climate on Earth Elevation 2369 feet Ideal Tourist Resort No Fogs, No Fleas No Sunstrokes, No Cyclones "The Sunshine City" Railway and Commercial Center Seat of Arizona University Center Rich Mining District Rich Agricultural Lands Splendid Business Opportunities Why Not Invest? YOUR FRIENDS Would be Interested in the Growth of this Enterprising and Progressive City Send Their Names and Addresses to The Tucson Chamber of Commerce A FREE ILLUSTRATED BOOKLET WILL BE MAILED TO THEM Albert Steinfeld & Co. Tucson, Arizona WHOLESALE AND RETAIL GENERAL MERCHANDISE Pumping Machinery for Reclaiming Desert Lands OPPORTUNITY INSURANCE Many a man has lost good business opportunities by not being prepared financially to grasp them. In an eastern city a skilled machinist, 50 years old, who had always earned a good salary, sold a valuable invention for a small amount because he had not saved any money and had not capital to float it. He said that if he had had even a small amount of capital he could have made a fortune out of the de- vice. Now, past middle life, he must keep on working, when he might have retired in comfort. Insure YOUR opportunities by means of a savings bank account. In this kind of insurance you are PAID dividends instead of having to PAY premiums. At this bank your dividends come in the form of FOUR per cent semi-annually compounded interest. SOUTHERN ARIZONA BANK & TRUST CO. TUCSON, ARIZONA fifif ■v/ --r ?r\s ;VM- >£ % I ik -i W jk V^k& ?"^ »m M )W< n ^f . n. ~4> i