No. 572] SHORTER ARTICLES AND DISCUSSION 497 



descending from the same motherplant. Of these mutants the 

 nandla and snni-gigas are especially valuable because similar 

 forms have been produced by 0. Lamarckiana. It will be seen that 

 the biennis-dwarfs seem to be somewhat rarer than the dwarfs of 

 Lamarckiana. Whilst for the latt r the mu tat ion coefticient is about 

 1 per cent., our O.bu nnis neinclla appeared as the only dwarf among 

 920 individuals. The above cited 0. biennis cruciata naneUa 

 was the only dwarfed individual in a culture of 500. And the 

 dwarf which I got in 1911 was the only one among about 600 

 plants. In this connection I wish to recall the conclusion 

 reached by do Vries that in O. Lamarckiana the pangen for tall 

 stature must be assumed to be present in the labile condition on 

 both sides, in (). biennis, however, only in the male sexual type, 

 whilst in the female sexual type active alta-pangens have to be 

 supposed. The way from biennis to biennis nanella might there- 

 fore possibly be somewhat longer than the one from Lamnn Liana 

 to Lamarckiana nanella. The biennis semi-gigas which appeared 

 in the last summer corresponded in all points exactly with the 

 mutant of 1911. Moreover a count of the chromosomes, as shown 

 by nuclear plate-stages in the meristematic tissue of young buds, 

 determined them to be 21 in number. Even as the specimen of 

 this type, that appeared in 1911, and as the semi-gigas mutants 

 produced by O. Lamarckiana, the plant of last year proved to be 

 almost absolutely sterile. 



In his second above-mentioned paper Davis says about the O. 

 biennis of our dunes: "No species of (Enothcra is perhaps so free 

 from suspicion as to its gametic purity. If Stomps can obtain 

 mutations from tested material of the Dutch biennis grown in 

 pure lines he will have the basis of a strong argument, ..." 

 Fortunately the experiment asked for by Davis, has been made 

 in the same year as his criticism. The butch biennis L.. culti- 

 vated in pure line, has produced a dwarf, a semi-gigas and some 

 snlfim ^/-individuals, proving its mutability beyond all doubt. I 

 therefore trust that the conclusions arrived at in my first paper, 

 concerning this mutability and its consequences, may now be ac- 

 cepted as thoroughly valid. 



Theo. J. Stomps 



