Embryological Studies of Two Members of the Podostemaceae

Abstract

Some of the structural details of Lawia zaylanica and Griffithella hookeriana are described. In Griffithella the anthers are quad-rilocular, inclosing paired pollen grains. At the shedding stage there is a lenticular generative cell and a large tube cell in each pollen grain. In both Lawia and Griffithella the ovules are anat-ropous 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. The mature embryo sac of L. zeylanica is usually 4- or rarely 5-nucleate, by the chalazal nucleus may soon degenerate and disappear, so that only 4 nuclei are seen in the older stages. Sometimes the chalazal nucleus may divide to give a 6-nucleate embryo sac. In G. hookeriana the mature embryo sac is 4-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. A prominent multinucleate pseudo embryo sac is seen in both the species, resulting from the disintegration of the axial row of cells.