PLANT BREEDING AND EVOLUTION 



181 



from our knowledge of the nature of the fertilizing process. If 

 pollen from a white flower is placed on the stigma of a red one, 

 the germ cells which unite to form the zygote are going to 

 transfer to the zygote cell, and to the embryo which grows from 

 it, the white and the red characters of the two parents. Exactly 

 the same thing may happen 

 with reference to any of the 

 different characters of two 

 parents which are crossed. 

 The offspring are certain, 

 therefore, to inherit the double 

 set of characters received from 

 the parents. Experiment has 

 shown that the parental char- 

 acters may be variously com- 

 bined in the different offspring 

 of a given cross. We are 

 familiar with all of these phe- 

 nomena in the human race, 

 where the children in a family 

 inherit in different ways and 

 in different degrees the char- 

 acters of their parents. 



If, therefore, a sufficiently 

 large number of crosses are 

 made and the offspring are 

 carefully observed, almost 

 any combination of parental 

 characters may be obtained 

 by the experienced plant breeder. Two instances selected from 

 the work of Burbank will suffice to illustrate the truth of this 

 statement. Burbank selected a wild blackberry, with white or 

 cream-colored fruit, which was too small to be valuable for 

 eating. He crossed this white blackberry with a large edible 

 blackberry, the Lawton, in an endeavor to secure a white edible 

 blackberry. Among the hundreds of hybrids which resulted 

 from extensive crossing a few showed the desired combination 



FIG. 94. A hybrid wheat and the parents 



Parents at the right and left ; hybrid in the 

 center. The size and awn characters of the 

 hybrid are intermediate ; the grains and 

 covering bracts resemble the parent at the 

 left. Photograph by the Minnesota Agri- 

 cultural Experiment Station. From Bergen 

 and Cald well's " Practical Botany " 



