The Mutations in the Laniarctziana-Fcunily. 235 



way in which their small unripe fruits are crcjwded to- 

 gether. 



In tlie fourth generation of my Lamarckiana-i2i\w\\\ 

 (grown in 1895 and consisting of 14,000 plants) there 

 were 176 O. oblonga; in the fifth generation (grown in 

 1896 and consisting of 8000) there were 135. That is, 

 in the one case 1.3, in the other 1.7 %. In the sixth gen- 

 eration this proportion was maintained (29 in 1800 = 

 1.6%). In the last two the number has been mucli 

 smaller because the counting had to be discontinued too 

 early. 



In 1896 I got seeds from biennial plants of the fourth 

 generation, and from annual ones of the fifth by arti- 

 ficial self-fertilization in paper-bags. There were seven 

 of the biennial seed-parents : each of them produced be- 

 tween two and three hundred seeds wdiich were sown 

 in separate lots. Altogether 1683 plants were raised from 

 them. They were all oblonga with the exception of one 

 which had the characters of albida. There were no ex- 

 amples of Lamarckiana among them. 



Ten of the annual plants of the fifth generation set 

 seed which was, however, scanty and germinated badl}-. 

 Only 64 plants were raised ; of these one was O. nibri- 

 nervis, the rest oblonga. There were no Laniarckianas. 



I have tested the constancy of other examples oi ob- 

 longa wdiich have arisen in other families with the same 

 result. 



Oenothera oblonga is, therefore, perfectly constant 

 directly it arises, but it has the power of, itself, giving 

 rise to new forms. 



V. 0. nanclla (O. Lamarckiana nanclla). Dwarf 

 Oenothera. We are not now concerned with the ques- 

 tion whether a particular form is to be described as a spe- 



