THEORIES OF DEVELOPMENT 



stonelessness, in combination with other desirable 

 qualities from divergent strains, reappearing only 

 in the subsequent generations. 



Altogether similar was the history of the thorn- 

 less blackberry, which finally developed into 

 a wonderfully vigorous plant with stems as 

 smooth as pussy-willows, and bearing an abun- 

 dance of luscious fruit, is the product of many 

 generations of cross-breeding through which the 

 quality of thornlessness that was inherent in a 

 little otherwise worthless trailing dewberry from 

 Virginia was combined with the good qualities of 

 sundry varieties of cultivated blackberries that 

 grew on thorn-laden bushes. 



The development of the white blackberry, from 

 a small variety of brownish- white color to a splen- 

 did berry of snowy whiteness, came about in the 

 same way; and to this day, if you were to cross 

 an ordinary blackberry with the Burbank white 

 variety, you must expect that the progeny will 

 bear black berries, and only in the succeeding 

 generation will plants appear that bear the white 

 fruit of one of their grandparents. 



SELECTIVE LINE BKEEDING 



(5) The accentuation of characters by line 

 breeding plays a no less significant part in Mr. 

 Burbank 's scheme of plant development. Whether 

 the plant with which you deal be pure breed of 

 a hybrid, it will seldom happen that a quality 

 that you are attempting to develop is manifested 



[33] 



