OENOTHERA RUBRINERVIS, A HALF MUTANT. 



367 



The laeta have hardly any empty grains, but the figures for 

 velutina fall short of this, even as in other instances. In the last 

 place, 1 counted the germs in the hybrids of the crosses with La- 

 marckiana, self-fertilizing three specimens of each of the types: 



The lucida have almost no empty grains; the figures for hybr. 

 rubrinervis are the same as those for the mutant of that name, but 

 those for the Lamarckiana type give an unexpected result. In two 

 cases they are the same as for the species, but in the third the empty 

 grains have almost wholly disappeared. This latter specimen has 

 lost all the external marks of 0. deserens and 0. rubrinervis, but 

 kept the absence of the lethal factors. Its progeny splits into La- 

 marckiana, lucida, and rubrinervis, and the first of these forms 

 repeats the splitting in the following generation. (See 0. scindens) 



0. Lamarckiana nanellax rubrinervis. — As in so many other cases, 

 the crosses with dwarfs can give a verification of those with the 

 species itself. In Gruppemveise Artbildung (p. 215) I have described 

 the pedigrees of two reciprocal crosses, both of which produced as 

 a second hybrid the subrobusta. This was seen to split off, after self- 

 fertilization, brittle plants and dwarfs. In 1915 I sowed some seeds 

 of the subrobusta plants of 1907 mentioned in those tables, in order 

 to compare their progeny with my newer cultures. I found for two 

 specimens of 0. (nanellay rubrinervis) subrobusta 38 and 45 per cent 

 of dwarfs among 82 and 60 plants, and for two parents 0. {rubrinervis 

 xnanella) subrobusta 20 and 13 per cent of dwarfs among 60 and 46 

 individuals. The number of brittle plants, however, was very small, 

 being two specimens for the first and one for the reciprocal group. 

 It is possible that the germs of this type are weaker, and that some 

 of them had died during the 7 years of their preservation. I self- 

 fertilized one brittle specimen in each of the two main groups and 

 had in 1916 two lots of 45 and 60 flowering plants, all of which were 

 brittle and like their parents. They contained 9 and 8 per cent of 



