66 BULLETIN- 700^ U. S. DEPAETMEXT OF AGEICULTURE. 



tliem; consequently, their individual effect on the activities of the 

 plant can not be definitely declared in all instances. 



Oak-bra^h /Jsper?-/yr sSprace -/yr 



— — — — Leaf /ncre/rre/yf' 



/Ii^era^e. c/a/Vy eyajooraf/on 



— - /^yerczye c/a/A/ p/Ty^/o/oy/ccz./ 



I'ls/Tipera.funs Gff/'c/'er7cy 



Fig. 36. — Average daily increment in leaf expansion of wheat throughout season compared 

 with evaporation and temperature in type stations. 



EFFECT OF TEMPERATURE AND EVAPORATIOX ON WATER REQUIREMENTS OF PLANTS. 



Since the rate of growth and production of dry matter by plants 

 appear to be controlled chiefly bj^ evaporation- and temperature, so 



