| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 90 === Acer buergerianum Miq. var. formosanum (Hay.) Sasaki is an endemic species to Taiwan. The small trees are half-deciduous and monoecious. Unisexual flowers are produced from March to May; samara are dispersed from August to October in the year.
Inflorescence primordia are emerged from the apical meristem in mid-October. Anther primordia are composed of the protoderm and the central cell mass in late October. The protoderm will differentiate into the epidermis later. The layer beneath the protoderm divides periclinally to form the 'outer primary parietal layer' and 'inner primary parietal layer'. The inner primary parietal layer develops into sporogenous cells which give raise to the pollen mother cells later. The outer primary parietal layer then divides periclinally several times to form the anther wall layers, while the central cell mass develops and differentiates into the connective tissue. As pollen mother cells are formed, the wall layer is consisting of, from inner to outer, a tapetum of uninucleate cells, two middle layers, an endothecium, and the epidermis. Tetrahedral tetrads of microspores are mostly formed by simultaneous cytokinesis. Mature pollen grains are 25-27.5µm × 22-25µm in size and 3-tricolporate. Anther dehiscence is longitudinal. Pollen grains are shed at two-celled stage with a generative cell of lens-form.
Two opposite carpels fuse one another to form a biloculate ovary with two ovules in each cell. Ovule primordia are formed on the enrolled carpel margins in late November. The megaspore mother cell is located at the 3rd or 4th layer of cells in the nucellus. It divides transversally to form a linear megaspore triad or tetrad, and the one at chalazal end develops into the embryo sac mother cell. The embryo sac is monosporic and indentical to the 8-nucleate Polygonum type. The egg cell and two synergids are located at the micropylar pole of the embryo sac. Two polar nuclei fuse before fertilization. Three antipodal cells are at the chalazal pole and emerald. The endosperm consists of free nuclei during development. The embryogeny is identified to the Onagrad type. Each seed contains 2 folded cotyledons.
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