Oenothera Nanella. 369 



O. nanella has arisen from other new species in about 

 the same proportions; from leptocarpa in 1896 in a pro- 

 portion of 0.4 %, from O. scintillans in various experi- 

 ments from 1896-1899 also in a proportion of OA fo 

 (There were 29 nanellas amongst 7872 seecUings). 



The progeny of nanella mutants come true to seed. 

 I have observed over 400 examples of this species which 

 have arisen directly from other forms. Together they 

 obviously constitute a species which can at once be rec- 

 ognized by many characters, although every one of them 

 was different from its parents and ancestors. 



I have already in § 3, p. 238, given the most im- 

 portant facts relating to the constancy of this form. It 

 only remains to amplify the brief account of the experi- 

 ments given above. 



I have made four series of experiments on the con- 

 stancy of 0. nanella. I began the first of them in 1889 

 with the twelve mutants from the laevifolia-isimily men- 

 tioned above (273). As I was not familiar with parch- 

 ment bags at that time I was not able to guard my plants 

 against the visits of insects although I always grew them 

 on a bed which was isolated as much as possible. But 

 even so, the dwarf type proved heritable in a very high 

 degree. I harvested the first seeds in 1890 as the plants 

 did not flower till the second year. I raised 20 plants, 

 of which 18 were dwarfs; they flowered the same sum- 

 mer and set plenty of seed. This seed (about 6 ccm.) 

 I sowed on a bed of about 4 square meters. The culture 

 consisted almost entirely of dwarfs. After this the plants 

 flowered regularly in the first summer so that I obtained 

 the fourth generation in 1893 and the fifth in 1894. The 

 third consisted of 400 plants which were practically all 

 dwarfs; I fertilized some of these with their own pollen 



