68 PLANT BREEDING. 



varieties suited to California conditions. He grafts scions of the new 

 seedlings on standard apples, sometimes over 500 new kinds on one 

 large tree, that all may be tried under similar conditions. Prof. S. B. 

 Green, of the University of Minnesota, is breeding apples. He says: 



We know little about which varieties to use for superior crosses. The matter 

 is of such immense importance that we should uiake very many hybrids between 

 very many varieties. 



BREEDING BLACK WALNUTS. 



The black walnut serves well to illustrate the breeding of those 

 forest and ornamental trees which are propagated by seeds. Walnut 

 trees are grown for large logs of valuable lumber. Therefore the 

 planter needs varieties which will make rapid growth and will mature 

 early into trees of large size, straight, and of good form. In selecting 

 seeds to plant, growers usually get nuts wherever they are secured 

 with greatest ease. This leads to taking most of the seeds from heavy 

 seed-bearing trees rather than from those trees Avhich make a rapid 

 and large growth of lumber. In case of this tree the nuts have some 

 value, but in many species the seeds are of no use except to use in 

 propagating, and if the tree bears many seeds it must do so at the 

 expense of the production of wood. 



It miijht seem that the breeding of walnut and other trees is imprac- 

 ticable because of the long time required to get results. But the 

 time is not so long as might be supposed, as will be brought out by 

 the following suggested plan of securing superior varieties of walnuts. 



Since the pollen-bearing organs and the ovaries are in separate 

 flowers, the flowers are often cross-pollinated from other trees, and 

 there is considerable variation and opportunity for selection among 

 trees from nuts of the same mother tree. Likewise, there is great 

 variation between the plants groM^n from the nuts from several trees 

 growing native in one neighborhood, and doubtless still greater 

 among plants from mother trees found native in widely separated 

 portions of the coxintry. 



The writer, over twenty years ago, in central Iowa, planted some 

 acres to black walnut, and, the method of planting proving very good 

 and the distance apart about right, the suggestions here are in part 

 based upon that experience. The nuts were from various large and 

 small native trees along a neighboring stream, They were gathered 

 when sufliciently ripe to be easily shaken to the earth, and were at 

 once placed in trenches (3 inches deep and 2 feet wide, running down 

 a slight incline in the shade of a grove. Moist straw or leaves were 

 placed over the nuts, from which the hulls had not been removed. 

 The nuts were thus kept moist all winter, that they might be cracked by 

 freezing. In the spring the fall-plowed land was marked off each way 

 with a corn marker, making cross marks nearly 4 feet apart each way. 

 The nuts were planted in each hill of every third row, thus placing 



