MUTATIONS, VARIATIONS, AND RE;i.ATIONSHIPS OP THE OENOTHERAS. 89 



RECAPITULATION. 



The principal features of the foregoing paper may be stated in the following 

 brief generalizations : 



(i) The probabihty of the origination of new elementary strains of plants 

 arising by saltations or sporting is one which has received the support of many 

 authors, from inferential conclusions based upon the examination of living 

 material. It has also been found by more than one worker that characters 

 acquired in a saltatory manner are not swamped by intercrossings. If such 

 characters behave as units they may well survive, whether dominant or reces- 

 sive with respect to the corresponding character of the parental stock, the prob- 

 abilities for survival being somewhat greater with recessive characters. 



(2) Frequency of mutation is put forward as a better expression than 

 periodicity of mutation for the proportion of salts occurring in the course of 

 generations. 



(3) An evening- primrose inseparable from 0. lamarckiana occurred around 

 Haarlem, Holland, as early as 1756, and near Liverpool, England, in 1806. 

 It has been noted in this and other districts at various times, and has been 

 under more or less continuous observation since 1892. Apparently estab- 

 lished and growing with it are 0. rubrinervis and 0. lata, two of its mutants. 

 0. hrevistylis, another mutant which is recessive when crossed with O. la- 

 marckiana, has been in existence in competition with the parental form in 

 Holland for twenty years. 



(4) The coefficient of mutability of Oenothera lamarckiana has not been 

 increased in the cultures in America, although a form which has hitherto 

 escaped observation was secured. Seeds of this parental form, from various 

 sources outside of Amsterdam, furnished a smaller proportion of mutants than 

 the material furnished by Professor De Vries. 



(5) 0. ohlonga has been found to constitute as much as 54 per cent of the 

 atypic derivatives of 0. lamarckiana. 0. lata, from material grown in England, 

 was found capable of self-fertilization and gave rise to a progeny containing 

 the same elements as when fertilized by the parental form. 



(6) Fixed hybrids constituting species were secured in combinations of 

 0. lamarckiana and 0. cruciata. 



(7) The greater variability of phylogenetically new characters as compared 

 with older ones, which was supported by statistical evidence brought forward 

 in a previous paper, is confirmed by the evidence presented by further studies. 



(8) The forms which would appear to promise most of importance in a 

 pedigree-culture would be species with a low degree of variability, having 

 nearly related forms with a high degree of variability. 



(9) The hypanthium of Oenothera, which seems to be a recent development, 

 is more variable than any other feature of the bud. 



