348 PLANT AND ANIMAL BREEDING 



small, and really a light yellow rather than white. It was, without 

 a doubt, a member of the blackberry family. He hybridized this 

 by crossing it with the Lawton blackberry which was black, large, 

 juicy, and of pleasing flavor. He found that black was dominant 

 over the light yellow. In the F 2 generation the light color again 

 appeared, and by selecting for several generations only the plants 

 for breeding that combined the lack of color with the desirable 

 flavor and size, he obtained a large tasty berry that is now known 

 as a white blackberry. 



Some varieties of plants have been improved in many different 

 ways. Luther Burbank studied various kinds of plums obtainable 

 here and in other countries. He crossed American, Japanese, and 

 European kinds. Then he selected the best for further experi- 

 mentation. As a result, he obtained different species: (1) of 

 many varieties in the coloring of skin and the texture of flesh ; 

 (2) of a wide variety of shapes; (3) of a wide variety of new 

 flavors and aromas ; (4) of sizes that are increased to three inches 

 in length and two and one half in diameter; (5) that produced 

 either early or late species. (Some ripen a month before the 

 earliest of the old varieties ; others ripen as late as December.) 

 (6) that are not affected by the frost or cold weather. Some 

 plums have been developed that can be shipped long distances 

 without spoiling. A species has been produced that can remain 

 on the tree a month or two in hot weather without decaying, 

 unlike the old varieties which had to be picked as soon as they 

 were ripe. Some trees bearing these new varieties will begin 

 to bear abundantly the third year if cuttings from young trees are 

 grafted upon trees of ordinary size. 



Some of these new plums grow in climates and under conditions 

 where the plum has hitherto been a failure. The Beach plum is a 

 wild species growing along the coast. It is a low, spreading shrub 

 with a small bitter fruit. It is very prolific and is resistant to cold 

 and frost. This was crossed with an American plum. The result- 



