PLANT BREEDING 



267 



any noteworthy success, however, the plant breeder must have 

 an ideal type clearly in mind and breed toward it. No progress 

 will be made if the ideals are constantly changing and the 

 plants selected for one feature one year, and another feature 

 the 'next. By keeping the desired form constantly in view, 

 taking advantage of all favorable variation and always select- 

 ing the best, a steady advance may be made for a series of 

 years. Now and then a sport may develop which will suddenly 

 carry the work forward with a bound, but usually the small 

 variations must be depended upon. There is a point, however, 



Photograph from Bergen and Caldwell's "Practical Botany" 



FIG. 194. A prize ear of corn that sold for two hundred fifty dollars 



beyond which each plant refuses to go. It would probably 

 be impossible to produce tomatoes as large as pumpkins, 

 though the size might be greatly increased by selection and, 

 in fact, has been. Nor is it likely that a blue-flowered form 

 could be developed from one with red flowers, though the color 

 in the blue flowers might be varied greatly by such means. 

 The average amount of sugar in sugar beets has been raised 

 from 8 per cent to 18 per cent within a very short time, 

 while single specimens have been found with much higher 

 sugar content. In plant breeding it is usual to pay more 

 attention to the average advance than to single cases, since 



