THE RELATION OF CLIMATE TO POMOLOGY 237 



same average phenological constant date of a seasonal event 

 and the same average climatic and biological conditions." 



In other words, if 1 degree of latitude is assumed to be 

 equal to about 70 miles and 1 degree of longitude equal to 

 50 miles, then, other things being equal, there are 4 days 

 variation for eveiy 70 miles north or south and for every 

 250 miles east or west from a given point, and for every 

 400 feet altitude. Or if any given isophane is followed, 

 there would be no variation in time of occurrence of the nat- 

 ural phenomena. Variations from these rules will occur, 

 depending on such modifying influences as are mentioned 

 in rule 2. 



A fuller appreciation of this subject means that spray cal- 

 endars must be made up for conditions of similar climatic 

 conditions; a study of insect and disease control must con- 

 sider the local conditions; and so for many agricultural prac- 

 tices and researches. 



207. Species adaptation. — It is not a settled question 

 as to liow far a species native to one set of climatic condi- 

 tions can become adapted to an entirely different climate. 

 That is, can a plant from a warm region gradually become 

 acclimated to a cold one and hence secure hardier strains 

 or races of tender plants? Can a plant which requires a 

 moist growing season gradually become adapted to xero- 

 phytic conditions or vice versa? These questions are of great 

 importance in the science of pomology and much difference 

 of opinion is recorded in literature. It is now usually ac- 

 cepted, however, that a plant is not gradually changed to 

 suit its enviroimient but that it is necessaiy to secure indi- 

 viduals which possess the character desired and from this 

 stock so breed a new strain as to combine other desirable 

 qualities. At least this would seem to be the shortest and 

 surest method of securing better fruits for extreme condi- 

 tions of soil and climate. 



