Igt5] DE VRIES—OENOTHERA BIENNIS 187 
tana X biennis, which, moreover, flowered at the same time on other 
plots of my garden. A number of these plants have been self- 
pollinated. Thus we see that the pollen of O. biennis nanella gives 
in these cases exactly the same forms as that of pure O. biennis, 
at least so far as the first generation is concerned. 
The specimen of O. biennis semigigas of the cultures of Stomps 
had only matured seed in the capsules which had been pollinated 
by pure O. biennis, without being castrated. From these seeds 
two types arose, neither of which was a semigigas. .All in all, 
there were 19 plants, belonging to two forms, besides a mutant. 
This last was a dwarf, which, however, has not flowered. Of the 
remainder, ten individuals were pure biennis during their whole 
life and in all their marks. They had the normal number of 
chromosomes, namely 14, and gave a normal harvest of seeds. 
The others, 8 in number, were different from these in almost all 
respects, though but slightly. The color of their foliage was 
a whitish green, the leaves more flat, and with white veins. The 
spikes were more elongated, the flower buds more slender, the 
flowers small and erect, the fruits thin and cylindrical and rela- 
tively poor in seeds. These plants had 15 chromosomes, like 
the O. Lamarckiana lata studied recently by Gates and Miss 
Tuomas.” But they had none of the characters of a /ata, showing 
thereby that the number of chromosomes, even if differing from 
the type, does not necessarily run parallel with the external 
features. 
Further studies will have to show why one-half of the progeny 
of this cross came true to the characters of the pollen parent, while 
the other half constituted a new and uniform type, differing from 
all the mutations and hybrids hitherto studied in my experiment 
garden; and especially why the characters of the mother of the 
cross should be wholly absent in its progeny. 
The first result of this state of affairs has been that the char- 
acters which the semigigas mutants might show in early youth 
remained unknown, and that it has not been possible to point 
them out before the time of flowering. In July, all the spikes 
37 Gates, R. R., and Taomas, N., A cytological study of Oenothera mut. lata and 
O. mut. semilaa in relation to mutation. Quar. Jour. Micr. Sci. 59:523- 1914. 
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