OENOTHERA QIGAS NANELLA, A MENDELIAN MUTANT. 



29 



combination in fertilization of two sexual cells, both of which had 

 mutated into nanella. The production of dwarfs from 0. gigas 

 would then follow the same process which is to be assumed for the 

 origin of 0. gigas itself from 0. Lamar cki ana ; and the copulation 

 of two similarly mutated cells would then more easily be accessible 

 to experimental investigation. 



In order to verify the exactness of this conception I have fol- 

 lowed up the progeny of such a presumed mutant hybrid, and on 

 the other hand have made crosses between 0. gigas and 0. gigas 

 nanella. In both cases the truth of the assumption was easily ascer- 

 tained. 



Mutations of single gametes may be discovered by different 

 means in other instances also, the production of potential nanella 

 gametes by 0. Lamarckiana being the most likely to be betrayed 

 in this way 1 ). I have observed such cases in crosses between 0. La- 

 marckiana and 0. rubrinervis. From these ordinarily two types 

 arise in the first generation, one of which resembles the mother 

 and the other the father. In my book on Gruppenweise Artbildung 

 I have called them "Lamarckiana" and "subrobusta." Both types 

 are usually constant after self-fertilization. But, from time to 

 time, individuals appear which in their progeny produce an un- 

 expected number of dwarfs. The following cases may be adfluced. 



The rubrinervis strain for these experiments had arisen as a 

 mutant from 0. Lamarckiana in 1895, and its second generation was 

 cultivated in 1905. No dwarfs were produced in the first generation 

 after the crosses, and in the second only from single individuals, the 

 remainder giving either no dwarfs at all or only about 1 per cent, 

 by ordinary mutation. 



Table 1. 

 Exceptional production of dwarfs by single plants of Oenothera 



subrobusta 



i) Besides the production of gametes for gigas by O. Lamarckiana, 

 as shown by the occurrence of specimens of semigigas in self-fertilized 

 strains of the parent species, or by the production of the Hero-type in 

 crosses of O. Lamarckiana with allied species. 



