IMPROVING SMALL FRUITS 55 



view of complex plant hybridizations, and to 

 the plant experimenter in giving clews that 

 may prove advantageous in his work in the 

 field. 



Let us recall, as the text of our first illustra- 

 tion, the simplest case of plant crossing. 



When, let us say, a thorny and a thornless 

 blackberry are crossed, the offspring are all 

 thorny. But in the next generation a certain 

 proportion of the offspring are thornless. A 

 corresponding case is that of the ordinary 

 blackberry crossed with the white blackberry. 

 All the offspring of the first generation are 

 black, but whiteness reappears among their 

 descendants. 



Let us recall, further, that the process of 

 crossing consists essentially in bringing the 

 nucleus of the pollen cell in combination with 

 the nucleus of an egg cell. 



Also let us bear in mind a computation that 

 we were able to make with the aid of the physi- 

 cist, by which we were made aware that the 

 germ cell itself is a highly complex structure 

 with diversified component parts, each of which 

 may be thought of as having as much individu- 

 ality as any member of a developed organism. 



We saw that, even if we considered the indi- 

 vidual parts or members of a germ cell to 



