86 POLLEN AND POLLINATION IN THE EUPOMATIACEAE. By A. T. Hotchkiss, Department of Biology, University of Louisville. (Plate ii; twenty-six Text-figures.) [Read 28th May, 1958.] Synopsis. The formation of the microspores in Eupomatia laurina is described and illustrated. Standard descriptions and illustrations of the pollen grains of both E. laurina and E. bennettii are given. Pollination in E. bennettii is similar to that in E. laurina. Comparisons are made with other ranalian plants. Introduction. More information is needed as a basis for understanding the structure and relationships of the woody ranalian plants. As a beginning of a series of papers on the Eupomatiaceae, the geographical distribution of the family has been described (Hotchkiss, 1955). It is hoped that the present paper will be followed by additional information on this interesting family as studies are completed on various anatomical and morphological details. Materials were collected in New South Wales and Queensland as indicated in the text. MlCROSPOROGENESIS. The long, narrow, sunken sporangia are closely filled with microspore mother cells within cell walls which vary from an angular, isodiametric to a rather elongate form which persists through the tetrad stage (Text-figs. 1-22). During meiosis the cell wall thickens and becomes gelatinous in appearance. In Eupomatia laurina, meiosis in the microspore mother cells is normal and ten bivalents can be seen at metaphase I. These usually separate in a synchronous anaphase (Text-figs. 1-2). Infrequently, at anaphase I, however, there appears to be early separation of one bivalent, as shown in Text-figures 3-5; there also may be a tardy separation of one or more bivalents (Text-figs. 6-8). After division I, a cleavage furrow begins to form as in Magnolia (Parr, 1918) but stops with the formation of an internal ridge filled with wall material at the beginning of division II (Text-figs. 9-10). At the end of the second division, the first furrow continues its growth and at the same time additional furrows appear. Then, simultaneously, all the furrows divide the mother cell into four compartments containing the microspores (Text-figs. 11-16). At interkinesis there is a conspicuous spindle fibre apparatus remaining between the two dyad cells (Text-figs. 9-10). At the completion of meiosis II, spindle fibres are conspicuous between the nuclei of the tetrad and remain so until the cytoplasmic connections between the microspores are finally cut off by the advancing furrows (Text-figs. 11-16). From the more isodiametric young tetrads with 4-6 spindles there develop the commoner tetrahedral, isobilateral, rhombic and decussate tetrads enclosed in nearly spherical mother cell walls; from the linear, young tetrads with spindle connections between only the closely adjacent nuclei, there develop the rarer linear and T-shaped tetrads enclosed in elongate mother cell walls (Text-figs. 17-22). Pollen. The pollen grains of Eupomatia laurina have been figured by Hamilton (1897), figured and described by Erdtman (1952). The pollen grains of both species of Proceedings of the Linnean Society of New South Wales, 1958, Vol. lxxxiii, Part 2.
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