62 



BULLETIlSr 700, U. S. DEPARTMENT OF AGRICULTURE. 



temperature index and the evaporation rate were also expressed as 

 average daily rates in order to make these climatic factors com- 

 parable to the plant measurements. The data were recorded prac- 





Z./o 





<?.5- 



/.90 ^ -^ 





-^OO 



\ ^,^y^ ^z^^^^<^^^ 











/5./ 

 .72 



- ^ ^ — , / \ 24..0 



^^ 



27. 



/oe 





/->N ^ 







07^ 





-G/?OIA///VG SEASON- 



-^— Phys/o/o^/ca/ Tern perafure 

 efr/c/ency 



l/l/heat • -■ 



Srame-grass 



fvaporat/on 



Fig. 34. — Belation between increments of leaf expansion, evaporation rate, and tempera- 

 ture, aspen-fir type. 



tically simultaneously at about 10-day intervals in each association. 

 The first measurements here recorded ar^ for June 22—10 days after 

 establishing the potometers. 



Table 18. — Effect of evaporation and temperature on leaf expansion of wheat 

 and hrome grass in type stations at about 10-day intervals, beginning June 

 22, through groiving season. 



Association. 



Brome 



grass. 



Wheat. 



Pliysio- 

 logical tem- 

 perature 

 efficiency. 



Evapora- 

 tion 

 summation. 



Oak-brusli 



Mm. 







Mm. 

 4.7 

 1.5 

 1.9 

 2.1 

 .2 

 .0 



5.5 

 2.5 

 3.1 

 1.2 



.7 

 1.6 



1.90 

 .30 

 2.40 

 2.80 

 2.10 

 .85 



19.4 

 40.6 

 36.9 

 36.2 



27.7 

 28.0 



13.1 

 21.0 

 27.7 

 19.6 

 15.6 

 10.6 



5.8 

 9.8 

 12.5 

 10.8 

 7.4 

 5.7 



cc. 

 59.6 

 66 8 





Aspen-fir 



.50 

 2.10 



2.50 

 •41 



.72 



56.7 

 45.4 

 37.4 

 50.9 



40.0 

 21 





Spruce-fir 



.64 

 1.48 

 1.90 

 2.10 



2.00 

 1.10 

 1.90 

 2.30 

 6.50 

 6.10 



42.1 

 24.5 

 24.0 

 27,0 



50.0 

 83.1 

 59.6 

 38.8 

 30.0 

 49.0 





