CLIMATE AXD PLANT GROWTH. 



11 



21.3 



PE/IS 



UVHEAT 



B/?OM£ 



' loafer requirem en t per unit o / dry 



nnatter of aerial parts' 

 Water req uirem en t of a eria/ and 



subterranean parts combined 

 — — Proportion of roots to tops , percenf 



FiG. 3. — Water requiremont of aerial and subterranean parts of peas, wheat, and brome 

 grass, compared with the ratio of roots to aerial portion. 



