166 DRY-FARMING 
in various arid districts have shown that one and 
a half to three times more water evaporates from 
the plant than directly from well-tilled soil. To the 
present very little has been learned concerning the 
most effective methods of checking or controlling 
this continual loss of water. Transpiration, or the 
evaporation of water from the plants themselves, 
and the means of controlling this loss, are subjects of 
the deepest importance to the dry-farmer. 
Absorption 
To understand the methods for reducing trans- 
piration, as proposed in this chapter, it is necessary 
to review briefly the manner in which plants take 
water from the soil. The roots are the organs of 
water absorption. Practically no water is taken into 
the plants by the stems or leaves, even under condi- 
tions of heavy rainfall. Such small quantities as 
may enter the plant through the stems and leaves are 
of very little value in furthering the life and growth 
of the plant. The roots alone are of real conse- 
quence in water absorption. All parts of the roots do 
not possess equal power of taking up soil-water. In 
the process of water absorption the younger roots 
are most active and effective. Even of the young 
roots, however, only certain parts are actively en- 
gaged in water absorption. At the very tips of the 
young growing roots are numerous fine hairs, shown 
