288 LUTHER BURBANK 



as I am able to experiment to better advantage 

 with most plants, I am somewhat handicapped 

 in the attempt to deal with a few of the more 

 tender ones. 



This is notably true of the orange and its 

 allies of the citrus family. 



These fruits very naturally interested me from 

 the outset, not only because of their economic im- 

 portance, but because the five familiar species of 

 the family, namely the orange, lemon, lime, grape 

 fruit, and citron present inviting diversities of 

 form and habit, and yet are so closely allied that 

 they cross very readily, and thus give the plant 

 experimenter precisely the opportunity that he 

 is always seeking. 



It is probable that all these citrus fruits sprang 

 from one original species growing somewhere in 

 the region of northern India, though a primitive 

 form was described by Dr. Livingstone in central 

 Africa, but probably not a native there. 



But although the habitat of these plants has 

 always been restricted to subtropical climates, 

 yet they have become so diversified as to form 

 fairly good species, and the different traits of the 

 various members of the clan are fairly fixed. 

 Not that any of them may be raised advan- 

 tageously from seed, for here they show the same 

 diversity that is shown by the other cultivated 



