180 OENOTHERA LAMARCKIANA MUT. VELUTINA. 



of one laeta of the first type, since I happened to have fertilized 

 only that one in 1914. Its seeds contained 96 per cent of germs. 

 I cultivated 15 specimens of laeta from these seeds, and found, for 

 self-fertilized seeds of each of them, percentages between 91—97, 

 with a mean of 95. In this instance, therefore, the high percentage 

 seems to be constant. 



The main result of this inquiry is that 0. Lamarckiana mut. 

 velutina has lost the property of the parent species of producing 

 about one-half of empty grains, that this property is recessive to 

 the normal production of almost only good grains, and that a split- 

 ting is observed in the first generation, which seems to follow the 

 type of amphiclinous hybrids, as in the case of 0. Lamarckiana x 

 0. nanella. A further study is required to elucidate these points, 

 especially the behavior of the seeds as a mark of the generation 

 which produces them. 



Summary 



1. 0. Lamarckiana mut. velutina = 0. blandina arose from my 

 family of 0. Lamarckiana mut. lata x semilata among seeds of the 

 third generation saved in 1904, in 3 specimens. Of one of these I 

 cultivated a second generation and of one of the others 4 successive 

 generations, embracing together over 3000 plants. 



2. All these plants were exactly alike with the exception of 4 

 mutants which constituted a new type, 0. spiralis. The mutation 

 coefficient was 0.1 per cent, or about the same as for 0. rubrinervis 

 and 0. nanella, and much smaller than that for 0. Lamarckiana. 



3. For the appearance of the original mutation only one sexual 

 cell needs to be mutated, since in combining with a normal gamete 

 it may give rise to 0. blandina, as is shown by the splitting of both 

 the reciprocal crosses of this form with 0. Lamarckiana. The split- 

 ting goes into nearly equal groups of specimens like 0. blandina 

 and of laeta. 



4. 0. Lamarckiana mut. velutina resembles the hybrids of the 

 type of velutina so much as to be considered one of them. Among 

 them it is the most like 0. (Lamarckiana x 0. biennis Chicago) 

 velutina, without the marks of the second parental species, however. 

 It is slender, with long internodes in the spike, and with flowers 

 as large as those of 0. Lamarckiana. 



5. 0. Lamarckiana mut. velutina is distinguished from its parent 

 species in a very striking character. It hast lost the property of 

 producing about one-half of empty grains; almost all of its seeds 



