CROP IMPROVEMENT 21 



merit, the cross-fertilization is usually easily accomplished, and, on the 

 other hand, the varieties produced by crossing are not necessarily of supe- 

 rior merit. Crossing of plants for the most part results in new com- 

 binations of parental characters. By crossing a yellow pear tomato and a 

 large red one, one could produce a red pear tomato and a large yellow one. 

 If a variety of wheat with bearded heads and white grains is crossed with a 

 variety with smooth heads and red grains, there could be produced a bearded 

 wheat with red grains and a smooth wheat with white grains. By selection 

 and propagation the characters become fixed and give new varieties. 



RESULTS OT CROSSING WHEAT 



NOTE THE VARIATION IN THE SECOND GENERATION HYBRIDS. 1 



Choice of Varieties. In attempting to improve a crop one should 

 first endeavor to secure a first-class variety. Because of the great dif- 

 ference in varieties, if the poorer yielding ones were chosen and an 

 attempt were made to improve them in productiveness, it is not likely 

 that they could be made better than varieties already in existence. 



Variety testing is a rather simple matter, but some precautions must 

 be observed if the results are to be dependable. The main considerations 

 are as follows: 



1. The varieties should be tested on as uniform soil as possible of 

 the kind on which the field crops are to be grown. 



1 Courtesy of Pennsylvania Agricultural Experiment Station. 



