376 



The Jonrnal of Heredity 



extreme degree of fruitfuhiess found 

 in Pe-fsai under ordinary circum- 

 stances. 



When the fertihty of the flowers 

 treated with pollen from the same 

 plant (b, c, d) is compared with that of 

 those treated with pollen from different 

 plants (e), it is evident that the inten- 

 sity of self-sterility, that is, the grade 

 of infertility caused by selfing, is 

 somewhat higher than 50 per cent. 



Flowers bagged but not pollinated 

 artificially (a), failed to fruit to a re- 

 markable extent, giving only about five 

 per cent of normal pods. This leads 

 to the conclusion that the flowers of the 

 Pc-tsai are so constructed that auto- 

 matic self-pollination is almost impos- 

 sible, because the selfed flowers in 

 which pollination had been performed 

 artificially (b), exhibited much higher 

 fertility. 



In addition, it should be mentioned 



that in the group in which the flowers 

 were treated with pollen from the same 

 plant, the individual variations in the 

 grade of self-sterility exhibited a very 

 wide range, all the way from complete 

 fertility to complete sterility being 

 observed. This suggests the possibility 

 of strains occurring in which the per- 

 centage of self -sterility is inherently 

 higher or lower than in others. Again, 

 the fact was observed that in some in- 

 dividual plants pollination within a 

 flower and that between different flow- 

 ers on the same inflorescence was ap- 

 parently less effective than that between 

 different inflorescences on the same 

 plant (Fig. 20), and so it is not irn- 

 probable that strains exist which show 

 important differences in regard to the 

 extent of self-sterility. To clear up 

 these points, however, it would be 

 necessary to accumulate more data by 

 further experiments. 



Table I. Effects of Artificial Pollination in Pe-tsai Cabbage. 



Source of Pollen Used 







Actual Number 



E-S 



Uh 



Percentasre 



o c< 





Flowers bagged (a) | 12 



Pollen from same flower (b) | 32 



Pollen from dififerent flowers in the 



same inflorescence (c) 32 



Pollen from dififerent inflorescences 



of same plant (d) 27 



Pollen from the same plant (b-|-c-|-d) 2>Z 



Pollen from a dififerent plant (e) .... 2 



167 



482 



331 

 1,236 



25 



"3 



117 



358 



24 



II 



71 



103 



75 



249 



o 



148 



224 



266 



139 



629 



I 



4.8 

 30.3 



234 



35-3 

 29.0 

 96.0 



6.6 



16.8 



21.4 



22.7 



20.1 



0.0 



88.0 

 530 



55-2 



42.0 



50.9 

 4.0 



