CLIMATOLOGY 15 



ture as in the range of profitable peach growing. 

 Looking at this question, we find that this fruit suc- 

 ceeds over a great range, and that the limits of suc- 

 cessful commercial culture run pretty close to the 

 actual bounds of physiological safety on both the 

 northern and the southern edge. Perhaps it will be 

 instructive to make a comparison with the apple, a 

 fruit which has been much more carefully studied. 

 We may say, then, that the commercial culture of 

 the peach runs not quite so far north as the suc- 

 cessful culture of the Baldwin apple and as far south 

 as the successful culture of any kind of apple. Now 

 Dr. J. K. Shaw has shown that the best development 

 of the Baldwin apple lies along that line which re- 

 ceives an average temperature of fifty-six degrees 

 during the growing season, March to September. 

 The most southern apple zone, that in which such 

 distinctively southern varieties as Yates and Shock- 

 ley succeed, is characterized by a longer growing 

 season and by an average summer temperature of 

 sixty-six to sixty-seven degrees. So we may say 

 that these two thermal zones mark the real bounda- 

 ries of practical peach growing. 



Our comparison with the apple ought to be car- 

 ried one step further in order to bring out an impor- 

 tant difference. In the studies already referred to, 

 Dr. Shaw has shown that for each variety of apple 

 there is an optimum summer temperature, and that 

 most varieties come to their best development only 

 when grown pretty closely under these conditions. 

 Thus the luscious Grimes is at its best when it has 

 an average summer temperature of sixty-two de- 

 grees, the Yellow Newtown pippin requires an aver- 

 age of sixty degrees, while Northern Spy gets along 

 with only fifty-five to fifty-six degrees. 



The various varieties of peaches, however, are 



