Abstract: The formation of microspores and megaspores, the development of male and female gametophytes, the embryogenesis and the development of endosperm were studied in Mosla chinensis Bueh.-Ham. ex Maxim. (Lamiaceae). The development of anther wall was of the dicotyledonous type, of anthers the 4-sporangiate, and that of the tapetum was of the glandular type, of 2 ～ 4 cell nuclei. The primary sporogenous cells fimctioned directly as microspore mother cells and were arranged in a single row in a microsporangium. The cytokinesis in meiosis of the microspore mother cells was of the simultaneous type. Tetrads were tetrahedral, but sometimes isobilateral. Mature pollen grains contained two cells. Ovules were anatropous, unitegmic and tenuinucellate. The tetrad of megaspores was hnear shaped, with the first or rarely the second cell from the chalazal end being functional. The development of embryo sacs belongs to the polygonum type. The micropylar region of the mature embryo sacs was nearly ovate and slightly shorter than the narrowed chalazal region. The embryogenesis was of the onagrad type. The endosperm was cellular. The micropylar haustorimn was unicellular with 3-nuclei and the chalazal haustorium was unicellular and 2-nucleated. Seeds were exalbuminous and seedcoat is developed from the integument. The ovary wall developed into pericarp. The embryological characters of Mosla chinensis were mostly consistent with those of Perila ocimoides Linn. However, the cells of the endothecium were elongated and not fiberized at the 2- celled pollen stage in the former, whereas radially elongated and fiberized at this stage in the latter. Furthermore the micropylar haustorium, though unicellular in both, was 3-nucleated in the former and 4-nucleated in the latter. Unfortunately, there is no information of the function and arrangement of the primary sporogenous cells in Perilla, available for comparison. The embryological data so far available infer that the genus Mosla is closely related to Perilla.

Key words: Mosla chinensis, Formation of microspores and megaspores, Development of gametophytes, Embryogenesis, Endosperm formation