208 SYSTEMATIC POMOLOGY 



several others ; but these large group names 

 correspond very closely to botanical species 

 names. The species names even go further 

 than the common names, as is usually the 

 case, and subdivide groups which in popu- 

 lar language have only a single name. Thus 

 there are several separate species of walnuts, 

 several of hickory nuts, and two or three at 

 least among the chestnuts. Yet in certain 

 species groups the varieties are now growing 

 so numerous that some further classification 

 would be very appropriate, as, for example, 

 among chestnuts and pecans. 



The citrus fruits form a large group, com- 

 prising several species, many of which are of 

 great economic importance. In the regions 

 where they are grown the description and dis- 

 crimination of the varieties of citrus fruits 

 and their intelligent classification are quite 

 as important as the description and classifica- 

 tion of apples, for instance. Indeed, the 

 orange is to Florida and Southern California 

 what the apple is to Maine and Ontario. 

 There are very few American books on the 

 citrus fruits in which the student may consult 

 descriptions of varieties. The only descrip- 

 tive form which has ever come to the writer's 



