LUTHER BURBANK 



no sign of any spicules on either stems or leaves. 



More than fifteen thousand seedlings were 

 raised from the fruit of the best of these thorn- 

 less plants, and out of that large number not a 

 single specimen showed any tendency to develop 

 thorns, every one being as smooth as the branch 

 of an apple tree. 



Thus by inbreeding and selection from fruit 

 produced by a partially thornless wild dewberry, 

 I quickly developed a race of thornless berries 

 that could be depended on to breed absolutely 

 true as to thornlessness. 



If we interpret the facts of this development, 

 in the light of later experience, we may infer that 

 the condition of bearing thorns is prepotent or 

 dominant over the condition of thornlessness in 

 the blackberry. Thornlessness is, then, a reces- 

 sive trait which will be submerged in a cross be- 

 tween a thorny bush and a thornless one, but 

 which will reappear after the manner of recessive 

 traits, in a succeeding generation, provided two 

 individuals of mixed heritage are interbred. 



The fact that only a small percentage of my 

 first seedlings grown from the seeds Mr. Fairchild 

 sent were thornless, suggests that the flowers of 

 the bush on which they grew had been chiefly 

 fertilized with pollen from thorn-bearing bushes. 

 The fruit from such a pollenization would pro- 



[12] 



