Mutations in Nature. 307 



they had arisen a short or a long time back cannot be 

 determined now. That they were able to maintain them- 

 selves, whilst the other species were not, is probably due 

 to the fact that during the seedling and rosette stages 

 they are not in any way inferior to the ordinary Even- 

 ing Primrose. 



And, lastly, the question arises whether the mutation 

 period which I observed, began in the field at Hilversum 

 or before.^ The rapid multiplication of the plant in the 

 field since it was first sown in 1870 would appear, ac- 

 cording to horticultural experience, to be a sufficient cause 

 of mutation. Within about 8 generations (1870-1886) 

 the plants had increased from one or two to many hun- 

 dreds which had scattered their seeds far and wide. 



Perhaps the mutation period was much older, if not 

 in the case of all the new forms at least in that of those 

 which appeared oftenest (for example 0. lata and O. 

 nanella). But as I did not witness the beginning of this 

 process it does not seem to me to matter much when and 

 where it happened. 



. The point is that the cultures in the garden disclose 

 to us what happens, but ordinarily escapes observation, 

 in nature. 



^ Later experiments have shown the mutation period to be much 

 older. Cf. Ueber die Dauer der Miitationspcriode bet Oenothera 

 Lamarckiana, Ber. d. d. bot. Ges., 1905, Bd. XXIII, p. 382. (Note 

 of 1908.) 



