340 BOTANICAL GAZETTE [NOVEMBER 
The rubrinervis strain for these experiments had arisen as a 
mutant from O. 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 I 
EXCEPTIONAL PRODUCTION OF DWARFS BY SINGLE PLANTS OF Oenothera subrobusta 
Number of | Percentage 
Cross Cross t Gen. 2 Gen. individuals | of nanella 
Lamarckiana Xrubrinervis. . . . 1905 IQI3 1914 140 9 
rubrinervis x Lamarckiana.....} 1905 1907 1913 7° IL 
rubrinervis X Lamarckiana. ... . 1907 1913 1914 70 16 
If we compare these figures with the results of the crosses 
between O. rubrinervis and O. nanella itself, as described in my 
Gruppenweise Artbildung (p. 215), we find a complete analogy, 
since these crosses give no dwarfs in the first generation, and in the 
second about 10-14 per cent from the self-fertilized specimens of 
O. subrobusta. It is evident, therefore, that the exceptionally high 
yield of dwarfs in these crosses of O. Lamarckiana and O. rubrinervis 
must be the product of latent mutations which occurred in some of 
the sexual cells of one of the parents. And since O. Lamarckiana 
is known to produce ordinarily 1-2 per cent dwarfs, while O. 
rubrinervis does not show signs of such a mutability, we may con- 
fidently assume that our figures indicate latent mutations of sexual 
cells of O. Lamarckiana. 
BARTLET?’ recently described a similar instance of an unexpect- 
edly high mutability, and proposed for it the same explanation, on 
the assumption of a latent mutation of a sexual cell in a previous 
generation. This case is of the greatest interest since it relates to 
a pure species and not to the discovery of mutated gametes by 
means of crosses as in the experiments just described. ‘The mutat- 
ing species was O. Reynoldsii Bartlett, one of the forms of the old 
O. biennis. It produced in 1913 three marked types, one repeating 
the parental form, and the two others being dwarfs and called 
6 Barttett, H. H., Mutation en masse. Amer, Nat. IgI5s. 
