68 



The Journal of Heredity 



TIIREK FIRST-GENERATION HYBRIDS 



From left to right the pods represent the results of crosses of Lyon by Velvet, Velvet by Yokohama, 

 and Velvet by China, respectively. It is easilyseen that these pods contain only half the normal 

 number of seeds — that is, they are semi-sterile, in spite of the fact that all the pollen grains 

 of their parents are normally sound and their ovules have normally perfect embryo-sacs. 

 In the hybrids shown above, the semi-sterility is found, by microscopical examination, to 

 result in one-half of their pollen grains being empty and collapsed, and one-half of their 

 ovules being destitute of embryo-sacs. (Fig. 6). 



The aj^^reemcnt is as near as is to be 

 expected with only 18 ovaries. 



The sterile ovules do not grow in 

 size, and the place where they are can 

 usually be seen as a constriction from 

 the outside of the pod. On opening 

 the ripe pod, the aborted ovules are 

 seen as blackish specks, less than one 

 millimeter across. It is rare to find pods 

 containing as many as five or six seeds 

 in the hybrid (Fl) plants, though this 

 is a usual nimibcr in the jjarents. The 

 seeds in the hybrid pods are as well 

 formed, and germinate as readily as 

 those of the parent plants. 



Fig. 6 shows three selected pods of 

 the L>-on by Velvet, the Velvet b\' 

 Yokohama, and the Velvet by Chinji, 



first-generation hybrids. Only about 

 one or two per cent of the pods of 

 these hybrids have no aborted ovniles; 

 some pods have several aborted ovules, 

 some have few, but the commonest 

 numbers arc two or three. I have 

 usually chosen pods for illustration in 

 whicli aborted ovules alternate with 

 seeds, but it is as common to find two 

 aborted ovules or two seeds contiguous. 



Fig. 7 (left) depicts pods of the Velvet, 

 Yokohama, and their first-generation 

 hybrid. Three a1)orted ovules can be 

 seen in the hy])rid pod. 



Fig. 7 (right) illustrates ])ods of the 

 Velvet, China, and their first-generation 

 hybrid. The positions of two aborted 

 ox'ules are visible in the hybrid pod. 



