Embryological Studies of Two Members of the Podostemaceae

Abstract

1. This paper deals with some aspects of the morphology and gametogenesis of Lawia zeylanica and Griffithella hookeriana, members of the Podostemaceae. Some of the structural details of the two plants are described. 2. Microsporogenesis was investigated in Griffithella. The anthers are quadrilocular, inclosing paired pollen grains. At the shedding stage there is a lenticular generative cell and a large tube cell in each pollen grain. 3. Development of the female gametophyte was studied in both Lawia and Griffithella. The ovules are anatropous and bitegmic. The archesporial cell functions directly as the megaspore mother cell. The embryo-sac development corresponds to a reduced Allium type, in which there is reduction at the chalazal end, and consequently a complete elimination of the lower polar nucleus. 4. The mature embryo sac of L. zeylanica is usually four- or rarely five-nucleate, but the chalazal nucleus may soon degenerate and disappear, so that only four nuclei are seen in the older stages. Sometimes the chalazal nucleus may divide to give a six-nucleate embryo sac. 5. In G. hookeriana the mature embryo sac is four-nucleate because of early degeneration of the chalazal nucleus. A polar cell is formed during the development of the embryo sac. This may be an unusual feature among angiosperms. 6. A prominent multinucleate pseudo embryo sac is seen in both the species, resulting from the disintegration of the axial row of cells.