PLANT BREEDING 



365 



This is true because the size of the plant, the number and 

 size of its flowers and fruits, and many of its other character- 

 istics depend both upon the qualities that it inherits from its 

 parents and upon the conditions under which it grows. 

 Thus a wheat plant that under favorable conditions would 

 bear large heads may bear small ones in a bad season, or if 

 it grows in poor soil or in a dry place ; and a plant whose heads 

 would ordinarily be small may under unusually favorable 



FIG. 206. Breeding plots at the Wisconsin Experiment Station. These 

 plots are so small th'at it is possible to give attention to individual plants. 



conditions bear fairly large ones. Now, an ordinary variety 

 of wheat is a mixture of many races; some of which inherit a 

 tendency to produce large, some a tendency to produce me- 

 dium, and some a tendency to produce small, heads. So, 

 when we select a number of plants with large heads, it is quite 

 likely that some or even most of them belong to really large- 

 headed races ; but some may belong to small- or medium- 

 headed races and only happen, because of specially favorable 

 circumstances, to bear large heads. The grains from the 

 plants of the large-headed races will produce plants whose 



