izo 



The intake of water by this plant during the 

 period covered by the above history, is given in the table 

 below. It is obvious that the actual intake of water 

 by the plant will depend on the intensity of transpira- 

 tion which depends, in turn, on the evaporating power 

 of the air. cause of this, and in order to obtain 

 data which are comparable from day to day it is necessary 



to compute the water-intake relative to the loss of wa- 



p 

 ter from a poroiis cup atmometer~ over the same period* 



Dhis ratio is given in the last column of the table and 



corresponds to the similarly comparable transpiration 



ratio called by Livingston the "relative transpiration'. 



1. Livingston and Hawkins,- Gar. Inst, of './ash., 

 Pub. 204, pp. 5-48 (1915); Free,- Studies in Soil 

 Physics, pp. 18-20 (1912). 



2. On the porous cup atmometer and its use see: 

 Livingston,- Plant World 18: 21-30, 51-74, 95-111, 143- 

 149 (1915 . 



