THE RELATION OF CLIMATE TO POMOLOGY 219 



189. Relation of weather to the fruit crops. — The weather 

 may specifically affect the fruit crop for any given season 

 in two general ways: (1) it may govern largely the poten- 

 tial possibilities of the trees to form fruit-buds; and (2) it 

 may partially or entirely destroy the buds, blossoms, or 

 crop in the process of development. These effects of weather 

 on the fruit-crop may be subdivided as follows: (a) the 

 nature of the growing season may be favorable or unfavor- 

 able to a set of fruit-buds for the ensuing se<ason; (b) the 

 winter may be favorable to or may destroy the fruit-buds 

 previously formed; (c) the spring weather may be responsi- 

 ble for the partial or entire loss of the fruit crop due to frosts 

 at blooming time or shortly thereafter; (d) special agencies 

 such as hail or wind may partially or entirely destroy the 

 maturing crop; (e) rainy weather or heavy winds may prevent 

 pollination of the blossoms in whole or in part; (f) low tem- 

 peratures may check pollen-tube growth; (g) the quality of a 

 crop and the size of the individual fruits, as well as their early 

 or late maturity, is often governed largely by the weather. 



190. Temperature is the most important climatic element 

 affecting veg(>tation and the total effect of the warmth of 

 the air nuist be observed in studjdng it. There is a minimum 

 and maxumim temperature, below or above which the plant 

 does not function, and there is for each kind an optimum tem- 

 perature at which it grows or functions best. The minimum 

 for most higher plants is around 40° to 43° F. and the maxi- 

 mum is from 85° to 114° F., while the optima range from 

 75° to 85° F., depending in all cases on the species in ques- 

 tion. Since the various phases of the plants ' functions may 

 have different optima and since it is also difficult to define 

 closely these terms, the above temperatures should be con- 

 sidered as applying particularly to the more manifest growth 

 activities. The student of pomology is interested in both 

 the temperatures of the growing season and those of winter, 



