52 



BULLETIN 700, U. S. DEPARTMENT OF AGRICULTURE. 



The difference in the time for the plants to reach approximately 

 the same stage of maturity in the type stations may account, in part 

 at least, for the difference in the character and composition of the 

 vegetation in the respective types as well as for failures to establish 

 exotic and indigenous species adapted to types of higher effective tem- 

 peratures. In the spruce-fir type only those species which can com- 



16 

 IS 

 14 

 /3 



II 

 10 

 9 

 8 

 7 

 6 

 S 



71 



52 



9/5 



64-7 



785 



69.2 



5Z.O 



Oak-Brush Type 



As pen -Fir Spruce -Fir 



------- Days For Appearance Of Heads 



--- Temperature. Above 40 /\ 

 ---- Averac/e Dally Mean Temperature 



PIG. 28. Relation of temperature to time of first appearance of heads of wheat. 



plete their development to maturity in minimum time, provided, of 

 course, that their perpetuation is dependent wholly or primarily on 

 seed, are conspicuously in evidence and of economic importance. 

 This tendency toward early maturity is evident, for example, in the 

 case of mountain brome grass, less clays beirg required in all type 

 stations for its flower production than for that of peas and wheat. 



