320 



ESSENTIALS OF BOTANY 



A favorite blackberry, the Wilson Early, is a hybrid be- 

 tween two common wild species, the high blackberry ^ and 



the dewberry .2 Among 

 the descendants of hy- 

 brids between an almost 

 uneatable species ^ from 

 Siberia and an eatable 

 species * from California 

 is a new constant spe- 

 cies (not a variety), the 

 Primus blackberry. 



Hybrid plums in the 

 greatest variety have 

 been produced by plant 

 breeders, especially by 

 the well-known Cali- 

 fornian experimenter, 

 Luther Burbank. The 

 amount of variation in 

 the offspring of a single 

 hybrid is well shown by 

 Fig. 223. One fruit of 

 great value, the Climax 

 plum, was bred by this 

 experimenter as a hybrid 

 between a bitter, tomato- 

 shaped Chinese plum 

 and a Japanese plum. 

 400. Results of Hybridizing Citrous Fruits.— Most valua- 

 ble and interesting work in hybridizing plants of the Orange 

 family has been done by the United States Department of 



1 Rubus allegheniensis. ^ R. villosus. ^ R. cratmgi/oUus. ' S. vitifolius. 



Fig. 224. 



A, the tangelo, a hybrid between the tan- 

 gerine and the grape-fruit ; B, the grape- 

 fruit (one parent of ^) . 



