564 PLANT BREEDING 
ners, the hybrid type is maintained generation after generation. 
Blackberries, which are propagated vegetatively, have been im- 
proved by hybridization. By crossing the cultivated Black- 
berry, which has a large black fruit, with a small wild Blackberry, 
having a whitish or cream colored fruit, a Blackberry having a 
fruit large in size and light in color has been obtained. Many 
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Fic. 487. — Results of inbreeding and crossing on the size of ears in Corr. 
Outer ears, result of inbreeding one generation; middle ear, result in the firs 
generation of crossing these inbred generations. After East. 
of the best Plums and other fruit trees are hybrids, and the 
hybrid characters are retained by propagating the trees by graft- 
ing and budding. Hybrids are also common among Roses, Car- 
nations, and other ornamental plants. 
Crossing and Vigor of Offspring. — Crossing usually results 
in increased vigor, while self-fertilization commonly results in 
