Varietäten, Descendenz, Hybriden. 197 



a perfectly formal interpretation, but from mathemathical stand- 

 point, it is the only hypothesis possible that can satisfy the facts. 



M. J. Sirks (Bunnik). 

 The correction says: 

 "In my paper which appeared in the Am. Nat. IL. p. 129, the 

 "last seven lines on page seventy-nine should read as follows: 



"Self-sterile plants crossed with self-sterile plants gave only 

 "seifsterile offspring. Certain self-fertile plants, however, gave only 

 "self-fertile offspring either when self-pollinated or when crossed 

 "with self-sterile plants. Other self-fertile plants gave ratios of 3 self- 

 "fertile to 1 seifsterile offspring when self-pollinated and ratios of 

 "1:1 when crossed with pollen from self-sterile etc." 



E. M. East. 



Frost, H. B., The inheritance of doubleness in Matthiota 

 and Petunia. I. The hypotheses. (American Naturalist. IL. 

 p. 623-636. 1915.) 



The paper gives an exposure of the present hypotheses about 

 the inheritance of doubleness in Matthiola and Petunia. 



The case of doubleness in Matthiola would be explained by 

 accepting the single-making S-factor would cause a sterility of 

 pollen-grains or a lethal factor would be linked with it. Further, 

 if there is also a slight tendency to selective elimination of S-car- 

 rying eggs, we have a simple and direct explanation of the excess 

 of doubles over the expected 50 per cent. Or, if the S-carrying eggs 

 are more offen fertilized, the excess of doubles is explained. Once 

 more, selective elimination of Single (Ss) embryos might produce 

 the same result. In Petunia the deviation from the 1 : 1 ratio is 

 probably due to selective elimination; here doubleness is dominant. 

 The author thinks these forms to be hybrids, due not to the cros- 

 sing of widely different forms, but to mutation within the race. It 

 seems worth while, according to the writer, to ask whether in a 

 case like that of Oenothera , hybridization is the cause of mutation 

 or mutation one great cause of hybridity; apparently both views 

 may be in part correct. M. J. Sirks (Bunnik). 



Gates, R. R., On the modification ofcharacters by cros- 

 sing. (American Naturalis?. IL. p. 562 — 569. 1915.) 



The paper brings some evidence in favour of the possibility of 

 character-modification by crossing between some species of Oeno- 

 theva, i. c. O. rubricalyx and O. grandiflora. The foliage characters 

 in F2 form an absolutely continuous so that it is impossible to apply 

 to them usefully the unit-character conception. It is therefore diffi- 

 cult to obtain critical evidence from the foliage. The sharp pigmen- 

 tation character (R) of rubricalyx, however, gives in its inheritance 

 the possibility of obtaining crucial evidence. From the writers ex- 

 periments (Fo and Fg-generations of above mentioned crossing) we 

 must conclude that plants which are intermediate in pigmentation 

 breed true, at least in all cases tested, and that the degree of pig- 

 mentation in the parent is adhered to in the offspring whether the 

 parent is an under-pigmented R or an over-pigmented r. The pig- 

 mentation is much intensified when crossed back with rubricalyx, 

 and greatly diluted when crossed with grandiflora. 



It is not easy to furnish a complete explanation for this diluting 



