Microsporogenesis and the Development of Male Gametophyte in Swertia bimaculata

Microsporogenesis and the development of male gametophyte in Swertia bimaculata were studied by the method of paraffin section for the first time in the present paper. The main results can be concluded as follows: Anthers are tetrasporangiate, the development of anther walls conforms to the basic type and comprises of epidermis, endothecium, two middle layers and tapetum at mature stage. The tapetum has dual origin and belongs to the Glandular type. The degenerating tapetum nuclei in the middle of anther locules are from the tapetum cells, which undergo mitosis, then intrude into the anther locules and degenerate in situ at the early stage. Two middle layers are ephemeral; endothecium and epidermis persists and develops to become fibrous-thickening. The cytokinesis of the microspore mother cell in meiosis is of the simultaneous type. Most of the microspore tetrads are tetrahedral and there are still a few other types, such as isobilateral, dilateral. Pollen grain is mainly 2-celled type when shed, occasionally 3-celled type, and it has three apertures.