280 BOTANICAL GAZETTE [APRIL 
shade plants was greater than that of the sun plants."* The figures 
of table X bear out this relationship, not only with regard to the 
plants as a whole, but also with regard to the individual organs. 
The complete data are given in that table. 
As might be expected, the greatest difference in water content 
was found in the leaves, whereas the water content of the roots 
was about equal in the two groups. In the stems, in spite of the 
fact that the higher fresh weight corresponds with the higher dry 
weight, the shade plants, nevertheless, contained the greater pet- 
centage of water. 
General discussion 
_ Various views have been held as to the relation between tran- 
spiration and the production of plant substance, or the influence 
of these processes upon each other. As early as 1850, LAWES” 
expressed the belief that although the whole subject was as yet 4 
problem, a certain relationship existed between evaporation and 
rapidity of growth, in that the comparative rate of evaporation of 
water to some extent indicated the comparative activity of the 
processes of the plants. He was too cautious an investigator, how- 
ever, to conclude more than that his experiments indicated some 
definite relationship between the passage of water through the 
plant and the production of dry matter. A somewhat similar idea 
was expressed by FITrBoGEN."’ HELLRIEGEL" in discussing this 
subject pointed out that, although the curves of growth and of 
transpiration follow the same general course, they are never parallel 
or coincident. He considered the dry substance produced merely 
as a convenient empirical basis from which to reckon the water- 
utilization of plants. As a result of his experiments, which how- 
3 This fact should be taken into consideration in the curing of shade-grow? 
tobacco. 
4 Lawes, J. B., Experimental investigation into the amount of water given off 
by plants during their growth; especially in relation to the fixation and source of their 
various constituents. Jour. Hort. Soc. London 5:38-63. 1850. 
's FirTBOGEN, J., Altes und Neues aus dem Leben der Gerstenpflanze- Landw. 
Vers.-Stationen 13:81-136. 1871. 
6 HELLRIEGEL, H., of. cit. pp. 622-623. 1883. 
