1917] DeVRIES— OENOTHERA 23 



It is necessary, of course, to study the progeny of the laeta 

 plants with a high and of those with a low percentage figure. 

 Until now, however, I have had only an opportunity to study the 

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

 fertilized only that one in 19 14. 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 O. 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 O. LamarckianaX 

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

 family of 0. Lamarckiana mut. lataXsemilata 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 suc- 

 cessive generations, embracing together over 3000 plants. 



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

 4 mutants which constituted a new type, O. spiralis. The muta- 

 tion coefficient was 0.1 per cent, or about the same as for O. 

 rubrinervis and O. 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 



into nearly equal groups of specimens like 



and 



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

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



