On the Perianth Aestivation in the Portulacaceae and the basellaceae

1. The perianth aestivation of five species of Portulacaceae and of one of Basellaceae is described. 2. The aestivation at four of the five edges is throughout eutopic. The fifth edge, that between the third and the fifth tepal is very different in this respect and has been called therefore the critical edge. 3. In some species the aestivation at the critical edge shows a strong preponderance of eutopy; in others we meet with a chance distribution, in still others there is a certain preponderance of metatopy. 4. This fact is paralleled with the analogous fact that in some Dicotyledonous corollas the edge between the third and the fifth petal has a certain tendency to metatopy lacking at the other edges.