342 



BOTANICAL GAZETTE 



[novembek 



Tried in the same way, they gave the percentages of dwarfs shown 



in table III. 



TABLE III 



B. Dwarfs of O. gigas 



Generation 



Number of 

 seed-bearer 



Total of seedlings 



Dwarfs 



Percentage of 

 dwarfs 



6th generation . 



132 

 i6s 

 iSS 

 161 



159 

 76 



151 

 130 

 124 



o 



o 

 o 

 o 



19 



0.0 

 0.0 



0.6 



0.0 



iS-7 

 0.0 

 0.0 

 0.0 



ISO 



All in all, 19 specimens were studied. Among them three gave 

 a percentage of 15-15. 7-17.8, but the others gave only 1-2 per 

 cent or no dwarfs at all. The dwarfs produced by this latter group 

 were evidently due to ordinary mutabihty, but the figures for the 

 former group differed too widely from these to be looked at in the 

 same way. I consider them to be due to Mendeh'an segregation, 

 and assume that the fact that they fall short of the expected 25 per 

 cent is due to the difiiculties of cultivation and to a less viabiHty 

 of the dwarfs as compared with the normal specimens.'' I chose 

 no. 3 of the first group (17.8 per cent dwarfs) for continuing the 

 experiment. 



If the segregation in this second generation followed the law 

 of Mendel, then among the plants of normal stature one-third 

 must be constant in their progeny and the remainder must split 

 up according to the same law. I succeeded in having a dozen of 

 plants flower and ripen their seeds as annuals, fertiUzed them purely, 

 and sowed the harvest in the spring of 1914. The result is given 

 in table IV. 



Three of the individuals yielded no more dwarfs than in ordinary 

 mutation, and the seven others showed figures which approach 

 the Mendehan law as nearly as might be expected. If we combine 

 these figures with the 17.8 per cent of dwarfs of the former genera- 

 tion, we find for this about 18 per cent dwarfs, 57 per cent hybrids 



' See Gates, op. at., p. 89. 



