726 EXPERIMENT STATION RECORD. 



above this, while Acer dasycarpum, A. platanoidcs, Deutzia scatra, Lonicen 

 tatarica, Syringa vulgaris, and Vihurnum veitchi showed a similar curve 

 growth rate, except that the zones containing nodes showed less growth thai 

 those nearest them. Shaded stems showed not only a somewhat greater rat 

 of growth, but a longer period of growth for the nodes individually in som< 

 eases observed. 



Relative transpiration in rain-forest and desert plants, F. Shreve (Ahs. m 

 Science, n. ser., 39 (1914), No. 99S, p. 260).— The author defines relative trans 

 piration as the ratio of the absolute transpiration of a unit area of leaf sur 

 face to the concurrent evaporation from a unit area of water. This is believe< 

 to give an index of the physiological control of transpiration and of the actio] 

 of light upon it. The relative transpiration of a number of plants has beel 

 studied in Jamaica, representing rain-forest plants, and in Arizona, represent 

 ing desert conditions. 



A comparison of the rates of the relative transpiration in rain-forest an( 

 desert plants shows them to be of the same order of magnitude in the tw( 

 groups. Since the annual evaporation total in Arizona is ten times that ii 

 Jamaica, it is said to show that the absolute transpiration per unit in plant 

 of the desert is approximately ten times as great as it is in the rain-forest. 



Relation of transpiration of white pine seedlings to evaporation froi 

 atmometers, G. P. Burns (A'bs. in Science, n. ser., 39 {191J^), No. 998, pp. 259 

 260). — The author has imported on an attempt made to express the data recorde« 

 by meteorological instruments in terms of plant physiology and thus give then 

 a botanical significance. Experiments were conducted in a state forest nui 

 sery with white pine seedlings, comparisons being made with black and whit 

 atmometers under half shade, no shade, and full shade. Comparing the wate 

 loss under the different conditions gave coefficients of transpiration by whicl 

 the author claims it is possible to calculate the water loss from white pin< 

 seedlings from the evaporation from the atmometers. 



Plants grown under the three conditions studied showed great variation ii 

 structure, in the amount of ash, and in their chemical composition. Th< 

 amount of water transpired by the no-shade plants was many times that trans 

 pired by plants in half and full shade, but the percentage of ash figured on 

 dry matter basis was less in those plants than in either of the other two sets 

 experimented upon. Half shade was found to reduce the transpiration an< 

 evaporation, but the graphs showed that the response of the plants and th( 

 atmometers was not identical. 



Transpiration of Silphium laciniatum, L. A. Giddings (Ahs. in Science, 

 ser., 39 (1914), No. 998, pp. 258, 259). — Experiments carried on in the hiborator; 

 and field with S. laciniatum are reported. In both cases special attention wai 

 given to the effect of increased wind velocity on the rate of transpiration. Ii 

 the laboratory transpiration was found to increase with wind velocity up t< 

 a certain limit, after which it did not increase in r"f>portion as the wind veloci 

 ties were increased. As a rule in the field experiments transpiration wai 

 found to be greatest before evaporation had reached the maximum. 



The effect of certain surface films and dusts on the rate of transpiration 

 B. M. DuGGAE and J. S. Cooley (Ann. Missouri Bot. Gard., 1 (191^), No. 1, pp 

 1-22, pi. 1; ahs. in Science, n. ser., 89 (1914), No. 998, p. £.5.9).— Attention 

 called to the commonly observed fact that leaves of plants sprayed repeatedly 

 with Bordeaux mixture may remain green and healthy at the close of the sea 

 son several weeks after unsprayed leaves free from fungus disease hav< 

 ripened. There seems to have been no data offered explaining the reason foi 

 this extended vegetative period. 



