230 LUTHER BURBANK 



DEVELOPMENT THROUGH HYBRIDIZATION 



As the experiments in the development of the 

 blackberries continued, I quickly passed from the 

 stage of selection to that of crossbreeding and 

 hybridization. 



The plants utilized in these experiments in- 

 cluded not only all types of native blackberries 

 proper, and numerous foreign species, but plants 

 of the allied race of dewberries. 



The dewberry, to be sure, is closely related to 

 the blackberry; it is, indeed, a blackberry that 

 has assumed a trailing habit. Or possibly the 

 case would be stated more truly if we say that the 

 bush of the blackberry is a dewberry that has 

 risen from the ground and assumed the habit of 

 upright growing. 



There is, nevertheless, a sufficient divergence 

 to make the dewberry seem to casual inspection 

 a plant of distinct type. And, at the time when 

 my experiments were begun, there were prob- 

 ably few plant developers who would have sup- 

 posed it possible to hybridize even the dewberry 

 with the ordinary blackberry. 



Successive crosses were effected, nevertheless, 

 at an early stage of the work, and in the course 

 of my experiments the interblendings were so 

 numerous and intricate that seedlings were 



