46 



COBN CBOPS 



with a series of air spaces in the leaf so that there is free 

 movement of air into and out from the leaf. Also, the 

 vascular bundles, which deliver the water from the roots 

 into the leaf^ are spread out in the leaf into a fine net- 

 work so that every part is quickly supplied with water as 

 it evaporates. 



The quantity of water evaporated from day to day 

 depends directly on the conditions of climate and on the 

 amount of leaf area exposed. An average corn plant has 

 about 8 square feet of leaf surface, while a full stand of 

 corn has a total leaf area equal to twice the area of land 

 on which the corn is growing ; in other words an acre of 

 land would have about two acres of leaf surface. The 

 daily water loss per plant varies from 3 to 10 pounds, 

 depending on the humidity of the air and on the wind, 

 just as does any other object or a free water surface. The 

 following data, taken at the Nebraska Experiment Station, 

 illustrate the above statements : — 



TABLE X 



Daily Variation in Water Loss from Plants and Free 



Water ^ 



» Nebr. Agr. Exp. Sta., 24th Ann. Rpt., p. 102. 1911. 



