182 GENERAL BOTANY 



of characters of the wild and the cultivated parents. Burbank 

 was then able by careful selection to perpetuate a new race 

 of white edible blackberries. He had caused a reshuffling of 

 parental characters, which resulted in a new combination of 

 characters. 



In a similar manner Burbank set out to secure a large and pro- 

 lific daisy for commercial purposes. To secure the size, luster, and 

 hardiness which he desired he selected and crossed three kinds of 

 daisies, each of which possessed one of the characters which he 

 wished to combine in a new daisy. He therefore crossed a French 

 daisy, for its beautiful pearly white luster, with a large English 



a b c d 



FIG. 95. Hybridization in plums 



a, a stoneless wild plum which was crossed with an edible French prune ; b-e, 

 offspring of the cross. Adapted from a photograph by Burbank 



daisy and with the common prolific American daisy. Luster, large 

 size, and abundant flower production were the characters which 

 Burbank sought to combine in a single new race of daisies. By 

 careful selection from the offspring of repeated crossings he 

 finally secured a new daisy, the Shasta, in which all of these 

 three desired characters were combined in one plant. 



In considering these results of crossing, it should be stated that 

 Burbank did not create or secure any new characters in his daisies. 

 The union of the gametes in his repeated crosses resulted in the 

 mingling of the characters of the three daisy parents in the 

 zygotes in various combination, and in some zygotes the com- 

 binations which Burbank sought chanced to come together. 

 When the zygotes grew into plants, they manifested in their 

 external appearance the luster of the French daisy, combined 

 with the size of the English daisy and the abundant flowering 



