360 OENOTHERA RUBRINERVIS, A HALF MUTANT. 



The strain of 0. Lamar ckiana was derived from a rosette found 

 in the original station near Hilversum in 1905, and the pallescens 

 had been a mutant from this same strain 1 ). Although the cultures 

 were small, they prove the existence of mass mutation. I sowed 

 the seeds of a specimen of deserens from the first culture in 1914, 

 cultivated 25 flowering plants, and found these uniform with the 

 type of their parent. 



Summing up the results of all the tables, we may conclude that 

 all specimens of 0. rubrinervis, derived from various sources, and 

 the mutants as well as their offspring, show mass mutation into 

 0. deserens, besides a considerable number of empty seeds. Taking 

 into consideration the unavoidable losses in the numerical estima- 

 tions, we may further conclude that 0. rubrinervis produces about 

 one-fourth empty seeds, and among the living offspring about one- 

 third 0. deserens, which are constant in their progeny and have no 

 empty grains, or a'most none. This points to a relation of 1 : 2 : 1 

 for the whole harvest. The phenomenon is thus shown to be parallel 

 to the splitting of the hybrid mutant of 0. gigas nanella and to the 

 mass mutability of 0. grandiflora and of 0. Lamarckiana itself. 



Crosses between 0. rubrinervis and 0. deserens. — If this explanation 

 is true, it may be confirmed by means of crossing 0. rubrinervis 

 with its mass mutant. The sexual cells of the first are about one- 

 half deserens without a lethal factor, and the rest velutina provided 

 with such a factor; those of 0. deserens, however, aie uniformly 

 so. We must expect, therefore, a splitting into almost equal parts 

 of deserensxdeserens=0. deserens, and of velutinaxdeserens=0. 

 rubrinervis. I made both the reciprocal crosses in 1915, cultivated 

 58 and 50 specimens of their offspring in 1916, and counted them 

 at the beginning of the flowering period in July, finding as follows: 



O. rubrinervis xO. deserens 

 O. deserens xO. rubrinervis 



Percentage 



of 

 rubrinervis 



Percentage 



of 



deserens 



48 

 78 



52 

 22 



The two types of hybrids resembled their parents exactly, and the 

 figures point to numerical equality of the two groups, although the 



J ) New dimorphic mutants of the Oenotheras. Bot. Gaz. 62 : 262. 1916. Opera 

 VII, p. 83. 



