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TEXTBOOK OF BOTANY 



by breeding. are the size, shape, color, taste, and keeping 

 quality of fruits and other edible parts, and the size, color, 

 and odor of flowers. 



All these qualities and many others that might be named 

 are of a more or less general nature ; a single variety of apple 

 or of potato or of rose might conceivably be bred which would 

 combine in itself all the desirable general qualities, excepting 

 perhaps that of a long bearing season. In addition, how- 

 ever, there are local and special conditions to be met, which 



FIG. 204. Breeding for disease-resistance. A crop of healthy plants 

 grown from the seed of those shown in Figure 203. This seed was sown 

 in a field in which other varieties had been a complete failure because of 

 yellows. The selected variety gave 95 per cent of a normal yield. After 

 Jones and Oilman. 



make it necessary to develop many different varieties of the 

 same species. Most important, perhaps, of the local condi- 

 tions are those of climate. Varieties that are adapted to a 

 locality where the growing season is long and where rain is 

 abundant are not likely to thrive where the summers are short 

 and there is little rain. In the great grain-raising 'Countries 

 much work has been and is being done to produce different 

 varieties of wheat, oats, barley, and rye that will grow well 

 and yield good crops under different conditions of climate. 

 The whole world is benefited whenever a variety is obtained 



