Twin Hybrids (Laeta and Velutina) and Their Anatomical Distinctions

Abstract

1. The stigma of Oenothera Lamarckiana is much higher than the anthers. The anthers open both on rainy and sunny days, whereas some of the other forms open their anthers only on sunny days. 2. The European species, O. biennis, differs from the American species. Its anthers and stigma are of the same height, instead of being of different height as in O. Lamarckiana. Its petals, pubescence, and most of its cells are the smallest of any of the forms described, while those of O. Lamarckiana tend to be the largest. 3. The twin hybrids laeta and velutina show themselves by their foliage, flowers, the greater density and character of the pubescence in velutina, as well as the arrangement and form of the cells, to be distinct, and, in so far as has yet been investigated, constant forms. 4. On rainy days the anthers of the twin hybrids do not open, but only on sunny days, and then only part of them, whereas in all the other forms they open on both rainy and sunny days. This non-opening of the anther cells may prob...