246 Varietäten, Descendenz, Hybriden. 



In one the capsules are two-celled and selection of individuals 

 having an occasional three-celled capsule does not increase the ten- 

 dency; in the other the tendency to have a greater number of cells 

 than two in the capsule is always transmitted. 



N. quadrivalvis Pursh and normal N. bigelovii Watson are alike 

 in all specilic characters except the number of cells in the capsule, 

 and since they give fertile hybrids when crossed it is thought that 

 N. bigelovii gave rise to N. quadrivalvis. 



It is proposed that the section Polidiclia in the genus Nicotiana 

 be dropped, and N. quadrivalvis Pursh be called N. bigelovii var. 

 quadrivalvis. Jongmans. 



East, E. M., Inheritance of flower size in crosses between 

 species of 7V^/co^/«wa. (Bot. Gazette. LV. p. 177— 188. Fl. 6— 10. 1913.) 



The writer gives following conclusions at the end of his paper: 



The inheritance of size complexes is so intricate that it is neces- 

 sary to simplify an experiment upon them in every possible man- 

 ner. The material used in this investigation, Nicotiana forgetiana 

 Hort. Sand, and N. alata grandißora Comes, lacks three of the 

 complicating features that usually ensnarl such work. They are 

 almost always naturally self-fertilized , and through numerous gene- 

 rations of selffertilization have become automatically as homozygous 

 in their characters as may be expected in plants that reproduce sexu- 

 ally. Their fecundity is so great that practically any quantity of F2 

 individuals can be produced from a Single F^ plant. A plant cha- 

 racter was investigated upon which the effect of environment is so 

 small as to be negligible, namely corolla size. 



These seif- fertile species, which are perfectly fertile inter se, 

 gave self-sterile progeny. This fact did not aflfect the production of 

 an F2 generation, as the F^ plants from homozygous parents are 

 alike in gametic Constitution and these were perfectly fertile inter se. 



N. forgetiana with a mean corolla length of 25.6 mm. crossed 

 with N. alata grandißora with a mean corolla length of 78.8 mm. 

 resulted in an intermediate F^ generation with a mean variability 

 of 44.3 mm. 



The variability of the F^ generation was very small, being 

 about the same as that of the remarkably constant parental species. 

 The F2 generation, on the contrary, was very variable and both 

 grandparental types were reproduced. 



It is shown that the F^ generation is what would be expected 

 if the difference in corolla length shown by these two species were 

 represented by the segregation and recombination of four cumula- 

 tive but independent pairs of unit factors, dominance being absent. 



The coincidence of theory and result is as great in this case as 

 it is in qualitative characters of like complexity. If the Mendelian 

 notation is useful to describe complex qualitative inheritance, it is 

 similarly useful in describing the inheritance of quantitative cha- 

 racters. 



Length of style and of filament are perfectly correlated with 

 corolla length. 



Breadth of corolla shows an average correlation with length of 

 corolla equal to 61 per cent 



The frequency distribution of corolla length for the Fg genera- 

 tion is positively skew. It is pointed out that the ränge of fluctua- 

 tions of corolla length in the two pure species is twice as great in 



