IQO BOTANICAL GAZETTE [march 



same group, although it grew among them and did not show any 

 higher degree of vigor. 



The fact that sulfurea mutants were observed in the progeny 

 of every one of the 7 parents of my culture directly proves this 

 line of mutability to be hereditary in the whole family derived from 

 the 1905 rosette from Wyk aan Zee. In combination with the 

 sporadic occurrence of the pale-colored variety in our sand dunes, 

 we may further infer that this mutability is hereditary in the whole 

 stock of our country, and probably also in the whole species, since 

 sulfurea plants have been found from the time of Tournefort 

 in France and other European countries. 



From the mutants constant races may be derived. I sowed 

 the self -pollinated seeds of the four mutants of Stomps, and culti- 

 vated 205, 225, 271, and 358 seedlings, altogether 1059 plants, all 

 of which have flowered and produced only pale-yellow petals, 

 making a very striking impression of constancy.^^ When crossed 

 with the pure species, the sulfurea strains give uniform hybrids 

 which are patroclinous. .Those of 0. biennis X. sulfurea have the pale 

 flowers, those of 0. biennis sulfurea'Xbiennis show the same bright 

 yellow as the parent species.^' 



On experimental germination of seeds 



Of the seeds of Oenothera Lamarckiana ordinarily only about 

 one-third produce seedlings, and this proportion is highly variable, 

 depending mainly on the conditions of cultivation of the parent 

 plant. Among the remaining seeds some contain a normal embryo, 

 others a more or less completely decayed one, while still others 

 are empty. The last have been thoroughly studied by Renner, 

 who found that they have been fertilized as well as the normal 

 seeds and those with decayed embryos. Between these normal and 

 externally normal seeds are seen the numerous rudimentary ovules 

 which have not been fertilized, and have not essentially increased 

 their size after the fertilization of the others. These rudimentary 

 seeds have been described by Geerts, as referred to above. 



3' Self-pollinated seeds of this second generation of 0. biennis stdfurea are available 

 for exchange in return for other races of mutating primroses. 

 3' Gruppenweise Artbildung. p. 298. 



