iQis] DE VRIES— OENOTHERA BIENNIS 187 



ianaX biennis, which, moreover, flowered at the same time on other 

 plots of my garden. A number of these plants have been self- 

 poUinated. Thus we see that the pollen of 0. biennis nanella gives 

 in these cases exactly the same forms as that of pure 0. biennis, 

 at least so far as the first generation is concerned. 



The specimen of 0. biennis semigigas of the cultures of Stomps 

 had only matured seed in the capsules which had been pollinated 

 by pure 0. 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 shghtly. 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 0. Lamarckiana lata studied recently by Gates and Miss 

 Thomas .3' But they had none of the characters of a lata, 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 halve 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 t)rpe, 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 



" Gates, R. R., and Thomas, N., A cytological study of Oenothera mut. lata and 

 0. mut. semilata in relation to mutation. Quar. Jour. Micr. Sci. SQ^S^S- ^9M- 



