Sporogenesis, Gametogenesis, and embryogeny of Wahlenbergia bicolor N. Lothian

Abstract

In Wahlenbergia bicolor, the anther wall is composed of four layers: epidermis, endothecium, middle layer, and tapetum. Wall formation and microsporogenesis are described, and the pollen grains are shed at the two-celled condition.

The ovules are tenuinucellate, with a hypodermal archesporial cell which develops directly as the megaspore mother cell. Megasporogenesis is normal, and a monosporic eight-nucleate embryo sac of the most common Polygonum type develops from the chalazal megaspore. The antipodals degenerate before fertilization.

The development of the embryo is of the solanad type. A suspected case of polyembryony was observed. The endosperm is cellular from its inception, and so conforms to the Codonopsis type. A micropylar and a chalazal haustoriurn, both consisting of two uninucleate cells, are formed from the endosperm.

Comparative studies were made with a known but as yet undescribed coastal species of Wahlenbergia, and no differences were found.