1914] HASSELBRING—EFFECT OF SHADING 281 
ever are open to criticism, he concluded that transpiration had no 
effect on the production of plant substance.” 
A somewhat unusual standpoint was taken by SorAvER,™ who 
regarded transpiration not merely as a mechanical process, but as 
a physiological function in the sense that it depends upon other 
physiological processes of the plant. According to him, outer 
factors do not influence transpiration directly, but only through 
their action on other functions of the plant. 
A relation not less intimate, but in its nature the converse of 
that conceived by SoravER, is that which Kon” believed to exist 
between transpiration and assimilation. He described the influence 
of transpiration upon assimilation essentially as follows: A rapidly 
transpiring plant receives, by means of the transpiration stream, a 
greater abundance of mineral nutrients, and is thereby enabled to 
produce more organic matter than a plant with lower transpiration. 
It should be said that Kout’s assumption was based purely on 
anatomical observations and not on comparative quantitative 
determinations. Increased transpiration does not necessarily bring 
about a greater abundance of mineral matter in plants.” A close 
correlation between transpiration and growth has recently been 
observed also by Lrvincston™ in wheat seedlings during the early 
Stages of their development. 
Although in general the conclusion derived from the work of 
_ these authors is that transpiration and assimilation are correlated 
or at most that transpiration has no influence on production, 
€xperiments leading to an opposite conclusion are not wanting. 
As early as 1869 SCHLOESSING” found that a tobacco plant 
8towing under a shaded bell jar produced more dry leaf substance 
* HELLRIEGEL, H., op. cit. pp. 461-5or. 
UER, P., Der Einfluss der Luftfeuchtigkeit. Bot. Zeit. 36:1-13, 17-25 
18 Sora 
1878; also Studien iiber Verdunstung. Forschungen Gebiete Agrikultur-Physik 
3*351-490. 1880. 
® Kout, F. G., Die Transpiration der Pflanzen. pp. 90-116. 1886. 
eae HASSELBRING, H., The relation between the transpiration stream and the 
. Ption of salts. Bor. Gaz. 57:72, 73- 1914. A complete account of this work 
Will appear later. 
. 
. 
Gston, B. E., Relation of transpiration to growth in wheat. Bor. Gaz. 
1905. 
22 Scutorssinc, Tu., Végétation comparée du tabac sous gloche et 4 l’air libre. 
Ann. Sci. Nat. Bot. V. 10:360-369. 1869. 
* Livin 
40°178-195, 
