634 FUNDAMENTALS OF FRUIT PRODUCTION 



the immediate factor responsible for limitation of the industry is a 

 parasite. 



Wind.— Wind is often considered important in determining whether 

 fruits can or cannot be grown successfully in certain sections. It is to 

 be doubted if wind alone is of great significance over any wide areas. On 

 the other hand, extreme heat or dryness accompanied by winds may 

 cause much damage and practically prevent the culture of certain fruits 

 in large areas where they frequently occur. Actually in such cases it is 

 the combination of high temperature or low humidity — or both — with the 

 wind that is the real factor. 



Native Range of Parent Species. — The native range of the parent 

 species without doubt furnishes some indication of the probable geo- 

 graphic range of the forms that are brought under cultivation; neverthe- 

 less it is doubtful if it is an index with most fruits of the extent to which 

 they may be grown for commercial production. For instance, the com- 

 mon European plum {Prunus domestica) is native to central and south- 

 eastern Europe. Its cultivation extends to practically all of Europe 

 and to much of temperate North America and it is grown to a limited 

 extent in many other parts of the world. Though the native home 

 of the peach is supposed to be China, it reaches its greatest commercial 

 importance in Europe, North America and southern Africa. The 

 Evergreen blackberry (Ruhus laciniatus) apparently is not cultivated in 

 southwestern Europe where it is found wild, but is of considerable impor- 

 tance in the Pacific Northwest 6,000 miles from its native home. On 

 the other hand the culture of the North American phim {Prunus ameri- 

 cana) is restricted to an area considerably less than the native range of 

 the parent species and the litchi (Nephelhmi litchi) is not grown com- 

 mercially outside China. 



Length of Time in Cultivation. — The length of time a species has been 

 under cultivation naturally has some influence on the amount of territory 

 over which it extents. Fruits of recent introduction, such as the pecan, 

 the blueberry and the loganberry have not had time to become dissemin- 

 ated widely and tried thoroughly in many sections. On the other hand, 

 though the Chinese jujube probably has been in cultivation as long as 

 the peach, its present geographic range is very small as compared with 

 that of its sister fruit coming from the same general region. Some 

 species, such as the fox grape ( Vitis labrusca) , are cultivated over a very 

 wide range of territory though they have been in cultivation only a few 

 decades. 



Uses and Quality of Product. — The variety of uses that the fruit and 

 the plant producing it serves has been doubtless an important factor in 

 making the cocoanut palm one of the most widely distributed fruits in 

 cultivation. For many tropical peoples it is the one most important 

 plant and there has thus been every encouragement to disseminate it 



