I.—Studies in Floral Morphology. II. The Staminal Zygomorphy of Couroupita guianensis, Aubl.

Abstract

In a former memoir published in these Transactions (20) the developmental study of floral characters has been reopened. It has there been shown that by this study, which for long has received little attention, the investigator, aided by modern technical methods, may gain a fuller understanding of the value of the characters by which his judgment in systematic matters is guided. The subject then dealt with was the initiation of staminal zygomorphy in certain dicotyledonous plants. It was there shown that in the history of a stamen from its initiation as a primordium until its anther is dehisced and its pollen shed there are three more or less distinct consecutive phases. In the first, or phase of initiation, the stamen-primordium is defined. From this primordium an undifferentiated multicellular body arises by rapid cell-division. In the second phase this body undergoes differentiation into the component parts of a stamen ; an anther and frequently a filament and connective are defined, and their cellular construction is completed. In the third and final phase the stamen is extended and functionates forthwith as a disseminator of pollen-grains. In this phase the extensible and elastic walls of the cells of the filament are distended by internal hydraulic pressure, and the anther-walls are dried and finally rupture by inequalities in their rate of shrinkage and by the agency of fibrous devices. These steps form the prelude to the actual functionating of the stamen, and since the final enlargement of the stamen-filament is due to water-pressure, this phase is known as the phase of extension.