CLIMATE AND PLANT GROWTH. 



53 



EFFECT OF TEMPERATURE AS INDICATED BY WATER REQUIREMENT PER UNIT OF 



LEAF AREA. 



The water requirements per unit of area of the chief food manufac- 

 turing agents of plants— the leavesi — may be used as an index of the 



13 

 /2 

 // 

 10 



9 

 8 





1 







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SJ^ 



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,-"^ 







^,-" 





39 



c:/^^ 



6es 



60 









660 







ss ~" -- — .__ 



SZ 











































, 63 



OaA-br-ush 



Aspen 



Sprace-f/r 



Days for appearance of heads 



Temperature above 40° 



A vera^ e c/ai/y mean fe/rjper^fure 



Pig. 29. — Relation of temperature to time of first appearance of heads of brome grass. 



efficiency of the leaves as users of water. The leaf length is used in- 

 stead of actual leaf area in the data given below, since, as has been 

 previously shown, it is proportional to the actual area. 



