ROOT SYSTEMS IN ARID SOILS 91 
Nebraska to a depth of fifty feet. Hilgard further 
declares that in California fibrous-rooted plants, 
such as wheat and barley, may descend in sandy 
soils from four to seven feet. Orchard trees in the 
a a 
5 3 
a 2 
“ Humid U 
GR 
= 
Fic. 26. Difference in root systems under humid and arid conditions. 
arid West, grown properly, are similarly observed 
to send their roots down to great depths. In fact, 
it has become a custom in many arid regions where 
the soils are easily penetrable to say that the root 
system of a tree corresponds in extent and branching 
to the part of the tree above ground. 
