HYBRIDIZATION AND SELECTION. 



47 



It must also be remembered that nearly all crops which are propa- 

 gated vegetatively belong to the class of crops which naturally 

 cross-fertilize; so that when we make a cross between two of them 

 we are really crossing things that are themselves many times hybrid. 

 For instance, a Baldwin apple tree is heterozygote for a good many 

 of its characters. For this reason it produces many kinds of pollen 

 and ovules, and when we use the Baldwin in a cross we get numerous 

 different varieties in the first generation, while if the two varieties 

 used in the cross were completely homozygote for all their char- 

 acters all the first-generation hybrids would be alike. 



SELF-FERTILIZED SPECIES. 



The principles involved in the hybridization and subsequent 

 selection to type of close-fertilized species, like wheat and oats, have 

 already been stated in more or less detail, but some additional points 

 need to be brought out. In utilizing hybridization in close-fer- 

 tilized crops the first problem is to select suitable forms for hybridi- 

 zation. Sometimes these forms are already at hand and well known. 

 The real object to be accomplished by hybridization in this case 

 is to make use of the law of recombination, by w^hich we can bring 

 together in one variety certain valuable characteristics which are 

 found scattered among two or more varieties which we may have at 

 hand or can secure. Take, for instance, the problem which pre- 

 sented itself, while the writer was agriculturist at the Washington 

 Agricultural Experiment Station, in connection with wheat growing 

 in eastern Washington. When the writer first went to Pullman, 

 where the experiment station is located, the farmers had been grow- 

 ing wheat in that section for twenty-five or thirty years. They 

 had tested many hundreds of varieties, but found very few of them 

 adapted to local conditions. Only three varieties had at that time 

 come into general use, and these three were each more or less re- 

 stricted to definite areas of different rainfall. For instance, where 

 the rainfall was 10 or 12 inches almost the only variety grown at 

 that time was Bluestem (not the hairy chaffed Bluestem of the 

 middle Northwestern States). This was grown for two reasons. 

 In the first place, it was one of the very few varieties found that 

 would grow tall enough to cut with so little rainfall. In the second 

 place, it produced a very superior quality of flour, and millers paid 

 about 3 cents a bushel more for it than for other varieties. But 

 this tall-growing variety could not be grown where the rainfall was 

 20 inches or more, because it would fall down if the season was at all 

 unfavorable. Where the rainfall was about 18 inches a variety of 

 club wheat known as ''Red Chaff" was very widely grown, while 

 81599°— Bui. 1G5— 11— 4 



