A contribution to the morphology and cytology of Monochoria hastaefolia Presl.

Abstract

The paper gives an account of the morphology, cytology and embryology of Monochoria hastœfolia. 1. Monochoria hastœfolia is a marshy plant. It has a subterranean root-stock and bears hastate leaves. The flowers show trimerous symmetry. Of the six stamens, one is larger and the anther is differently coloured. The pollen grains produced in this anther show no morphological or size-difference when compared to those produced in the other anthers. All are equally viable. 2. Anthesis of flowers takes place generally before 8 a.m. On cloudy and humid days it is delayed. Bagging of inflorescences shows that self-pollination is the rule. Seed formation takes place under natural conditions and it takes about 15 days for the seeds to develop after syngamy. The germination of the seed is of the "Palm-type". 3. The development of the microspore appears to be of the successive type. During heterotypic prophase the nucleolus becomes adpressed against the nuclear wall and assumes a lens-shaped structure. At this stage a distinct connection of the nucleolus with the spireme is first noted. At pachynema a small spherical body is seen to lie at the side of the nucleolus to which the spireme is connected. This has been referred to as the nucleolar body. At diakinesis a pair of bivalents are also seen to lie attached to the nucleolus. The haploid number of chromosome is 14. Cytokinesis takes place by cell plate formation. 4. The pollen grains have an elongated appearance when dry. The exine shows the presence of fine granulations all over the surface and has two furrows situated diametrically opposite to each other. The pollen grains are bi-nucleate at the time they are shed. The generative nucleus lies within a cytoplasmic sheath, the ends of which are drawn out. 5. The pollen grains germinate on the stigma within ten minutes after pollination. The pollen tubes pass through the stylar canals and the division of the generative nucleus takes place inside the pollen tube. The metaphase spindle is well organised. Furrows or cell plates have not been observed and it appears that the sperm-nuclei become separated by the disappearance of the spindle fibres.