PLANT LIFE. 31 



and this accounts for the excess absorbed by the roots. 

 During the course of a season, a field of wheat or corn 

 will evaporate from its leaves a great many tons of 

 water, equal to many inches of rainfall. 



Roots Absorb Soil Water. To obtain the neces- 

 sary supply of water and mineral matter the root sys- 

 tem must be rather widely spreading and have a large 

 absorbing surface. If the finer rootlets are carefully 

 removed from the soil and the excess of soil washed 

 off, they will be found to have a short distance back 

 from their tips, bands of fine whitish hairs, one-eighth 

 of an inch, to many times that in length. These so- 

 callec} root hairs penetrate between, and wind around, 

 the soil particles, lying in the film of water which sur- 

 rounds them and absorb the water. Practically all 

 the absorption of water is accomplished by these hairs. 



ROOTS OF YELLOW SOY BEAN GROWN ON LAND INOCULATED WITH 

 TUBERCLE-FORMING BACTERIA. 



