32 



OENOTHERA GIGAS NANELLA, A MENDELIAN MUTANT. 



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 mutability, 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 Mendelian segregation, 

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

 cent is due to the difficulties of cultivation and to a less viability 

 of the dwarfs as compared with the normal specimens 1 ). 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 ac- 

 cording to the same law. 1 succeeded in having a dozen of plants 

 flower and ripen their seeds as annuals, fertilized them purely, and 

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

 table IV. 



Table IV. 



C. Dwarfs among the offspring of 0. gigas (A, no. 3). 



Three of the individuals yielded no more dwarfs than in ordinary 

 mutation, and the seven others showed figures which approach 

 the Mendelian 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 



i) See Gates, op. cit., p. 89. 



