1 66 



MAIZF. 



CHAP. 

 V. 



Fro. 73. — Segregation of characters 

 in the F„ seed generation. If the sepa- 

 rate grains are planted and selfed they 

 produce the nine types shown in the 

 three following figures. 



flinty. In the following (i.e. 

 the second or F 2 ) generation of 

 either the direct or the recip- 

 rocal cross, however, some 

 grain is wrinkled and some, 

 on the same ear, is round and 

 flinty. 



If, as a matter of further ex- 

 periment, we cross a pure white 

 flint breed (Fig. 72A) with a 

 pure-bred black wrinkled breed 

 (Fig. 72B), the result is still 

 more interesting and instruc- 

 tive. In the first seed gene- 

 ration all the grains are black 

 flints (Fig. 72c). But in the 

 second seed generation four 

 kinds of grain occur on the 

 same ear (Fig. 73); two of 

 them are like those of the two 

 grandparents (i.e. the original 

 parents used in the cross), and 

 two (a black flint and a white 

 wrinkled) different from either 

 grandparent. It is evident, 

 therefore, that the characters 

 we have been studying in this 

 case, i.e. blackness and wrin- 

 kledness, whiteness and flint- 

 ness, may be segregated or 

 separated from each other by 

 crossing, and either trans- 

 mitted independently (or 

 re-united) as separate and in- 

 dependent units ; they are, 

 therefore, called unit-charac- 

 ters. The individual character 

 of any species of animal or 

 plant is made up of many 

 separate unit-characters, and 



