io6 PROBLEMS OF GENETICS 



laeta and velutina breed true to their respective types, and do not 

 reproduce the parent-types among their offspring resulting from 

 self-fertilisation. This statement must be qualified in two 

 respects. When muricata d 1 is fertilised by brevistylis the forms 

 laeta and velutina are produced, but each of them subsequently 

 throws the short-styled form as a recessive (de Vries, 1907, 

 p. 406). It may be remembered that de Vries's previous publi- 

 cations had already shown that the short style of brevistylis, 

 one of the Lamarckiana " mutants," behaves as a recessive 

 habitually {Mutationstheorie, II, p. 178, etc.). 



Also when nanella, the dwarf " mutant" of Lamarckiana is 

 used as male on muricata as female, laeta and velutina are pro- 

 duced, but one only of these, namely, velutina, subsequently 

 throws dwarfs on self -fertilisation. The dwarfs thus thrown are 

 said to form about 50 per cent, of the families in which they 

 occur (de Vries, 1908, p. 668). The fact that the two forms, 

 laeta and velutina, are produced by many matings in which 

 Lamarckiana and its mutant rubrinervis are used as males is 

 confirmed abundantly by Honing, who has carried out extensive 

 researches on the subject. After carefully reading his paper, 

 I have failed to understand the main purport of the argument 

 respecting the "double nature" of Lamarckiana which he founds 

 on these results, but I gather that in some way laeta is shown to 

 partake especially of the nature of Lamarckiana, while velutina 

 is a form of rubrinervis. The paper contains many records which 

 will be of value in subsequent analysis of these forms. 



Before considering the possible meaning of these facts we 

 must have in our minds the next and most novel of the recent 

 extensions of knowledge as to the genetic properties of the 

 Oenotheras. In the previous statement we have been concerned 

 with the results of using either Lamarckiana itself or one of its 

 "mutants" rubrinervis, brevistylis, or nanella as male, on one of 

 the species biennis or muricata. The new experiments relate 

 to crosses between the two species biennis and muricata 

 themselves. 



De Vries found : 



1. That the reciprocal hybrids from these two species differed, 



