OENOTHERA GIGAS NANELLA, A MENDELIAN MUTANT. 35 



Summary. 



1. Oenothera gigas produces dwarfs (about 1-2 per cent) and 

 mutant hybrids of normal stature, which after self-fertilization give 

 15-18 per cent, theoretically 25 per cent, of dwarfs. 



2. These mutant hybrids split up, after self-fertilization, accord- 

 ing to the law of Mendel, yielding about 18 per cent dwarfs, 25 per 

 cent normal specimens of tall stature, and 57 per cent hybrids of 

 the same type. The latter gave about 21 per cent of dwarfs among 

 their progeny. 



3. The mutant hybrids, fertilized by 0. gigas nanella, yield 

 30-43 per cent, theoretically 50 per cent, of dwarfs. 



4. In artificial crosses with 0. gigas the dwarfs follow the law 

 of Mendel. 



5. The production of dwarfs from 0. gigas by means of mutation, 

 therefore, is to be considered as requiring the copulation of two 

 gametes, both of which are potentially mutated into dwarfs. The 

 mutant hybrids must then be the result of the fertilization of a 

 mutated gamete by a normal one. They are correspondingly less 

 rare than the dwarfs themselves. 



6. In combination with the fact that the dwarfs of 0. Lamarcki- 

 ana do not follow the law of Mendel, either in their origin by muta- 

 tion or in artificial crosses with the parent species, these conclusions 

 reveal a new differential character between 0. gigas and its parent 

 species. 



Amsterdam. 



(The Botanical Gazette, Vol. LX, November 1915, p. 337.) 



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