10 



much as 22° C. (nearlj^ 40° F. ) at certain times of the day. 

 Such conditions occur, though slightly less accentuated, during 

 the entire summer in this locality. It is evident without further 

 discussion that such differences in the temperature conditions 

 of the two poles of the j^lant must exert a more or less im- 

 portant influence on the transport of fluids and solutions from 

 one part of the j^lant to another. Eeferring to the in-evious 

 discussion concerning the comjiarative transpiration and ab- 

 sorj^tion during the day it is to be seen that the heightened 

 temjDerature of the shoot must operate in a simple jDhysical 

 way to greatly augment the amount of water thrown off while 

 the roots must take in water at the same time to meet the loss 

 at a temijerature as much as 40° F. lower. 





Fio. G. — Tracings of thermographic curves of the air, and of the soil at 

 a depth of 30 centimeters (1 foot), September 29-November 3, 1902. A 

 further drop in temperature is shown which carries the soil below the 

 freezing point temporarily on the 22d, and finally for the season on the 

 29th. Centigrade scale. The temperature of tlie air is shown by the 

 uppermost of each pair of tracings. 



During the movement of the water from the roots to the 

 leaves of grasses and other low growing plants, a total distance 



