Belling: A Study of Semi-Sterility 



71 



THIRD GENERATION FROM FERTILE PARENT 



This photograph represents pods from six plants of the Lyon and Velvet third generation 

 (F3), grown from seed of a wholly fertile F2 plant, which was in turn grown from the 

 seed of a semi-sterile Fl plant (all of the Fl generation being semi-sterile, of course). 

 The above pods may fairly be taken to stand for the produce of half of all the plants of 

 the third generation: they all have normal pollen and ovules, because they were produced 

 by a F2 plant which was fertile. In each generation, fertile plants give rise to fertile plants; 

 semi-sterile plants give rise to plants which are half fertile and half semi-sterile. (Fig. 9). 



Velvet by Yokohama cross. It will be 

 remembered that half of the plants of 

 this generation were normal, and half 

 were semi-sterile. 



Fig. 8 (right) shows selected pods of 

 four fraternal plants of the same cross 

 and generation as the plants whose pods 

 are shown in Fig. 8 (left). These four 

 plants, however, had semi-sterile pollen. 



THE THIRD GENERATION. 



In the third generation (F3) all the 

 descendants of fertile plants have good 

 pollen and ovules; but the progeny of 

 the semi-sterile plants again separates 

 into equal numbers of fertile and semi- 

 sterile plants. In the F3 generation 

 of the Lyon by Velvet cross, which was 

 thoroughly investigated, the progeny 

 of 14 fertile plants amounted to 264 

 plants, all with good pollen and ovules; 



SECOND FILIAL GENERATION. 



In the second generation (F2) half 

 the plants have perfect pollen-grains, 

 and the other half have a mixture of 

 equal numbers of ftdl and empty grains 

 in all their flowers. The plants with 

 perfect pollen have also perfect ovules; 

 the plants with semi-sterile pollen have 

 also half their ovtiles sterile. In the 

 F2 generation of the \"elvet- Yokohama 

 cross, which was thoroughly investi- 

 gated, there were 180 fertile plants and 

 195 semi-sterile plants. Counts of the 

 ntimbers of seeds in the pods of the 

 second-generation plants of Velvet by 

 Lyon and Lyon by Velvet confirm 

 this ratio of 1 :1. 



Fig. 8 (left) shows typical five-seeded 

 pods of four fertile plants with normal 

 pollen from the second generation of the 



