Some aspects of the life history of Callistemon citrinus (Curt.) Skeels

Abstract

Pollen development is irregular in native populations but regular in the cultivated plants investigated. Development of the anther wall is of the Basic type and the tetrasporangiate anthers shed their pollen at the two-celled stage through longitudinal slits. The single vascular bundle of each stamen gives off two traces in the connective.

The ovules are anatropous, crassinucellar, and bitegmic. The swollen distal ends of both integuments form the micropyle. The single archesporial cell cuts off a parietal cell, and during megasporogenesis a one- to three-layered parietal tissue is formed which collapses during the development of the embryo sac. Occasionally the megaspore mother cell degenerates but in these instances the growth of the ovule is unimpaired. The female gametophyte follows the Polygonum type of development, and when mature is eight-nucleate and includes three ephemeral antipodal cells. Some abnormalities pertaining to the number and arrangement of nuclei in the embryo sac have been observed and hardly 4% of the ovules form fertile seeds. The seed coat is formed from both the integuments. A hypostase is differentiated in the seed.