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AGRICULTURAL TEXT-BOOK. 



Boussingault gives the following list of temperatures favorable 

 to the particular plants, in the success of which man is more 

 especially interested. Some of them require a mean annual 

 temperature, others only a mean summer temperature, as below : 



Thus we can grow melons, which only require a short period 

 of summer for growth and maturation ; but cannot grow pine 

 apples, which require at least two years before they bear fruit ; 

 although the former only needs one degree of mean temperature 

 less than the latter. 



131. The number of days that elapse between the commence 

 ment of vegetation and the period of ripeness is by so much the 

 greater as the mean temperature is lower. Thus, wheat, with a 

 mean temperature of 59 F., requires 137 days to mature; 

 with a temperature of 56 , 160 days; with a temperature of 

 76 , 92 days. In other words, the lower the mean tempera - 

 ture of the climate, the longer the crop must be in the ground 

 before harvesting. And thus Indian corn may ripen in a shel 

 tered valley, but be annually cut off by frost on a mountain side 

 a few miles distant. 



Experiments, however, prove that many grains, brought from a climate 

 with a markedly lower mean summer temperature, to one higher, only 

 acquire the power of ripening early by degrees of successive annual crops, 



