704 General and Applied Biology 



FIRST YEAR 



OETASSELEO 



OETASSELEO 



INBRED PLANT ^ INBRED PLANT 



A B 

 S/^ ■ 



■, INBRED PLANT " ^ INBRED PLANT 

 C D 



^ 



I 



I 



SECOND YEAR 



"\^ 



Fig. 348. — Diagram of the method of crossing inbred corn plants and the 

 resulting single-cross to produce double-cross hybrid seed. The four plants, A, B, 

 C, D, are inbred for several generations. Then strain A is crossed with strain B 

 {A furnishes pollen and B is detasseled). Strains C and D are crossed similarly. 

 Then the product of these two single-cross lines are crossed to produce the double- 

 cross seed used in commercial plantings. (From Richey, F. D.: The What and 

 How of Hybrid Corn, Farmers' Bulletin No. 1744, U. S. Department of Agri- 

 culture.) 



