LAMARCKIANA SEMIGIGAS. 569 



such individuals have not occurred. Those with 14 chromosomes 

 would give pure or almost pure Lamarckiana, provided their maternal 

 gamete belonged to the laeta type. Such is probably the case at 

 least in a sufficient number of germs, as we have previously seen 

 in the crosses of the pollen of semigigas. 



In the culture of the progeny of semigigasxvelutina, three plants 

 were found with 14 chromosomes and the external marks of 0. 

 Lamarckiana, corresponding to the expectation derived from this 

 discussion. The rosettes were very stout and easily recognized, 

 almost all the others being much weaker. In the flowering condition 

 the stems were as high and as stout as in the species itself, but the 

 flowers showed some influence of the characters of their grandparent 

 0. biennis, as was to be expected. The flower buds were somewhat 

 more cylindrical and the petals smaller than in the pure Lamarckiana. 

 For the same reason the spikes were more compact and the bracts 

 smaller, but the differences were very small and did not essentially 

 lessen the resemblance to ordinary Lamarckiana. 



Moreover, there were two plants with the same stature and ex- 

 ternal marks, which, however, had 15 and 20 chromosomes. In these 

 cases the doubling of the chromosomes was not followed by the 

 visible mutations which otherwise always seem to accompany it, 

 proving once more that this combination is not a necessary one. 

 Another plant with 20 chromosomes had very long, almost linear 

 leaves, constituting a type of its own of very doubtful interpreta- 

 tion. The linear form of the leaves, however, although not at all 

 rare among the progeny of semigigas, does almost always obscure 

 the other marks. 



Summary 



1. The progeny of Oenothera (lata x Lamarckiana) semigigasx 

 velutina constitutes a motley assembly of forms, many of which 

 are already recognizable among the young seedlings. On the con- 

 trary, the hybrids, produced by means of the pollen of semigigas, 

 did not show any noticeable variability. 



2 In the first named cross the mutants belong to different groups, 

 corresponding to the older mutant races derived from Lamarckiana. 

 There are seven main types, of which six are those of the dimorphic 

 (heterogamous and splitting) mutants lata, scintillans, cana, palles- 

 cens, liquida, and spathulata, while one constitutes a new type (0. 

 mut. pulla). With the exception of lata and cana, these groups 

 occurred with the same frequency. 



