22 ECOLOGY, PLANT GEOGRAPHY [Bot. Absts., Vol. IV, 



give less satisfactory results, the color concentrating in patches. Cells containing much 

 albumen become wholly opaque. Starch grains color pinkish, cell membranes are usually 

 colorless. Alcoholic material appears to give better results for starch coloration. In general, 

 the method of staining, while presenting much value for study of certain structures, starch 

 grains, etc., possesses little power of differentiation for many structures and must be used 

 with caution. — The starch grains of Hedera Helix appear to be a new form of this substance; 

 they stain brownish yellow with iodine and do not show concentric layers. The author dis- 

 cusses at length the protoplasmic granules stained by this method and concludes that they 

 may perhaps be mitochondria, without postulating anything about their identity with animal 

 structures; the term microsome could also be used. He thinks it more probable that these 

 granules are similar in nature to leucoplasts, i.e., miniature leucoplasts; since both divide 

 by constriction, and both produce starch. This conclusion is based upon a series of trans- 

 ition stages between granules and starch grains. Dangeard's ideas about vacuoles seem un- 

 worthy of recognition. — A bibliography of forty -two titles is given. — Edward B. Chamberlain. 



ECOLOGY AND PLANT GEOGRAPHY 



Henry C. Cowles, Editor 

 Geo. D. Fuller, Assistant Editor 



GENERAL, FACTORS, MEASUREMENTS 



17S. Bates, C. G. A new evaporimeter for use in forest studies. Monthly Weather Rev. 

 47: 283-294. Fig. 1-0. 1919. — The author discusses the factors which influence evaporation 

 or transpiration from plants and the conditions which must be met before water losses from 

 plants can be determined through instrumental methods. The "evaporation stress" or ten- 

 dency to evaporate is produced by a different combination of factors in each body in which 

 evaporation may occur in leaves. The vaporizing process takes place on the surface of the 

 moist cell walls not directly exposed to moving air, so that the effect of wind is greatly min- 

 imized in leaf evaporation, the rate of diffusion being controlled by vapor pressures in the 

 inter-cellular spaces. Evaporation from leaves is more directly controlled by radiant energy 

 than from a body which does not absorb so readily, and may obtain considerable heat from 

 air. Efforts were made to devise an instrument having the same relation to wind and radiant 

 energy as do leaves of plants, with the idea of an "inner cell" for the vaporizing process, 

 rather than a full exposed moist surface. A practical metallic instrument was devised, in 

 which the essential feature is a moist layer of linen between two metal plates; the upper plate 

 protects the wick from rain, being coated with lamp black and transmitting absorbed heat 

 to the wick; the lower plate is thick and contains a number of small perforations simulating 

 the stomata of leaves. Vapor formed in the moist linen escapes through these perforations. 

 The linen is kept moist by a stem wick from a distilled water supply, and evaporation losses 

 are obtained by weighings. Evaporation from this instrument follows the transpiration from 

 small coniferous trees used in the experiment much more closely than do other types of evap- 

 orimeters. The objectionable feature of this instrument lies in its exposing a horizontal 

 surface to evaporation. This may be an advantage if plant activity becomes less as the 

 season advances, the instrument at the same time exposing its absorbing surface less squarely 

 to the sun's rays. — E. N. Munns. 



179. Blair, Thomas Arthur. Influence of snow cover on the temperature distribution 

 in Utah, January, 1919. Monthly Weather Rev. 47: 165-166. 1919.— Portions of Utah nor- 

 mally covered with snow were bare in the early winter of 1919 and other portions usually bare 

 were covered with snow. Temperature records show that with snow negative departures of 

 both mean maximums and mean minimums were from 4° to 22°, while without snow the de- 

 partures were positive and ranged from 2° to 13°. — E. N. Munns. 



