368 OENOTHERA RUBRINERVIS, A HALF MUTANT. 



dwarfs, the stems of which were likewise brittle at the time of 

 flowering 1 ). 



Other races of 0. nanella or other conditions may produce in the 

 corresponding crosses brittle hybrids instead of subrobusta. I made 

 the cross 0. rubrinervisxnanella in 1905 with a dwarf mutant race 

 of 1895 and the reciprocal one with the progeny of a dwarf which 

 had arisen in 1911 from Lamarckiana, using in both cases the same 

 family of rubrinervis as in all previous crosses. The first named 

 cross gave 35 per cent Lamar ckiana, 3 per cent lucida, and 62 per 

 cent brittle rubrinervis among 68 specimens in 1913. The second 

 cross yielded the same three types, but the percentage figures devi- 

 ated widely. I had only 6 per cent Lamarckiana and 2 per cent 

 lucida, but 92 per cent brittle rubrinervis among 140 plants, most 

 of which flowered in August. The main result, however, is clear, 

 namely, that the crosses between 0. rubrinervis and 0. nanella give 

 three types of viable hybrids, one of which carries the visible marks 

 of 0. rubrinervis, but may be either brittle or tough. 



I have made only one cross between 0. deserens and a dwarf, 

 taking this latter from the first of the two last mentioned families. 

 I crossed them in 1915 and had in 1916 a culture of 60 plants, among 

 which 3 per cent were lucida and 97 per cent brittle rubrinervis. 

 Other types failed, as was to be expected. The seeds of the two 

 lucida plants contained 89 and 95 per cent of good germs. 



Summing up the results of the crosses between 0. rubrinervis 

 and 0. nanella, we see that they yield exactly the same hybrid types 

 as those with 0. Lamarckiana and in corresponding percentages. 



Crosses of 0. rubrinervis with heterogamic mutants. — Crosses with 

 the pollen of these forms must simply confirm those with 0. Lamarcki- 

 ana, since their pollen carries mainly the same hereditary qualities 

 as that of the parent species. I fertilized in 1913 two plants of my 

 main race of 0. rubrinervis with 0. cana, two with the pollen of the 

 LamarckianaAike offspring of self-fertilized scintillans, and added 

 the reciprocal cross of the latter combination. In the following 

 table I shall call these offspring scintillans- Lamar ckiana. 



About one-half of each group flowered in August. No brittle spe- 

 cimens occurred. The types were exactly the same as those derived 

 from the cross between 0. rubrinervis and 0. Lamarckiana. 



If the heterogamic types are used as female parents, the splitting 



x ) By means of this the gap left in the second pedigree of p. 215 of my book is 

 filled up, and both pedigrees are completed by the production of dwarfsfrom 

 the rubrinervis specimens. 



