202 BREEDING CROP PLANTS 



Kempton were made with widely different varieties, the results 

 are probably somewhat more striking than if more closely re- 

 lated forms had been used. 



FI Varietal Crosses. The utilization of hybrids as a means 

 of obtaining more vigorous types was urged by Beal (1876-1882). 

 Since then there has been frequent mention of the vigor of 

 FI crosses, and Morrow and Gardner (1893, 1894) outlined a 

 plan for the production of crossed corn seed. Renewed interest 

 in this subject was aroused as a result of the publications of East 



FIG. 46. Minn. No. 13 high protein strain No. 4. Short, erect strain with 

 light green leaves. Produces good ears. Tassels are plentifully supplied with 

 pollen. 



(19086) and Shull (1908, 1909) on the effects of inbreeding and 

 cross-breeding, and of Collins (1909, 1910) on the value of first 

 generation hybrids in corn. Many experiments in which first 

 generation crosses have been compared with their parents have 

 been made. In Table XL IX only those varietal crosses are used 

 in which the FI has been compared with both parents. 



A careful study of this table shows that first generation crosses, 

 on the average, yield more than the average of their parents. 

 In many cases the cross exceeds the higher yielding parent. No 



