i9i6] DeVRIES—DIMORFHIC MUTANTS 263 



specimen of 0. Lamarckiana mut. semigigas described by Stomps,' 

 and a narrow leaved specimen, exactly resembling the type described 

 and figured by Gager' for a derivative of 0. biennis. The speci- 

 men of pallescens was discovered by chance, since almost none but 

 mutants and a number of doubtful specimens had been planted 

 out; it occurred among the latter and was distinguished as a new 

 type only at the time of flowering. Thereupon, another part of 

 the same sample of seeds was sown in 191 1 and yielded two more 

 specimens of pallescens, among about 250 flowering individuals. 



The self-fertiKzed seeds of these three mutants gave rise to a 

 mixed progeny, the smaller half of which resembled the parent, 

 whereas the remainder presented the type of 0. Lamarckiana, 

 dupUcating this in all of its special marks and during all the stages 

 of their development. In the following description I will, there- 

 fore, indicate them simply as Lamarckiana, without discussing the 

 question whether some internal characters might perhaps be differ- 

 ent. But externally there is no difference; moreover, the progeny 

 of this derivative Lamarckiana behaves exactly Hke that of normal 

 ones. This splitting into these two types has repeated itself in 

 . the following generations and in all of the cases investigated. 



Moreover, the pallescens seems to be mutable to a higher degree 

 than 0. Lamarckiana itself; for, although my cultures have been 

 necessarily small, the number of mutants is very striking, reaching 

 20 among about 500 specimens, or 4 per cent. From the first three 

 mutants I have derived three pedigree families, which I will now 



briefly describe. 



Pedigree of mut. pallescens no. i 



1910 Mutant Mutant 



igii, 1913 . . . . Second generation 42 per cent pallescens Lamarckiana i mutant rubrinervis 



igi3 Third generation 23-43 per cent pallescens Lamarckiana Lamarckiana rubrinervis 



1914 Fourth generation 24 per cent pallescens Lamarckiana Lamarckiana 



1915 Fifth generation 38 per cent pallescens Lamarckiana 



' Stomps, Theo. J., Die Entstehung von Oenothera gigas DeVries. Ber. Deutsch. 

 Bot. Gesells. 30:^06. 1912. 



» Gager, Stuart C, Cryptomeric inheritance in Onagra. Contrib. Brooklyn 

 Bot. Garden no. 3, Bull. Torr. Bot. Club 38: 461-471- figs- 2- iQ"- 



