The transformation of the plant ovule into an ovary

Abstract

In plants there is a rather wide capacity for the development of organs of various kinds from primordia normally destined to produce quite different structures. For example, leaves may replace petals, stamens or carpels; petals may occur in the place of stamens or carpels. The transformation of stamens into carpels is a well-known phenomenon.

Furthermore, the continued development of a growing point the activity of which is usually terminated by the formation of some highly specialized organ, such as the flower or fruit, is quite familiar to those concerned with problems of variation.

Among these morphological abnormalities the continued meristematic activity of the axis which is normally terminated by the formation of the ovary is of very rare occurrence. It is, however, regularly found, although in a small and variable percentage of the cases, in one of the passion flowers, Passiflora gracilis. Here prolification of the fruit consists in the formation of series of carpels, which may or may not be ovuliferous, within the normal fruit. The mass of accessory carpels thus formed may be so large as to rupture the fruit wall.

While the occurrence of prolification may be regarded as a heritable characteristic in P. gracilis the abnormality is of relatively rare occurrence. Physico-chemical factors must, therefore, determine the occurrence of prolification in certain fruits and its absence from others. 1

If the formation of the basal prolification be due to the presence of special formative substances, one might occasionally expect to find the formation of carpellary tissue from other primordia. The only primordia normally developed subsequent to the carpels themselves are the ovules, which are borne on the carpellary margins.

To test this point, and to secure materials for other investigations, a series of dissections was begun in 1908. Those which were made from 1908 to 1915 are summarized in the accompanying table.