. The classification of flowering plants. Plants. IV] ANGIOSPERMS 147 and appears to contain longitudinal series of pollen-sacs. This occurs in many Leguminosae of the Mimosa section (fig. 68, L) and others, and recalls the segmentation by sterile tissue in the sporangium of Isoetes. Each of the spore-mother-cells divides to form four special mother-cells, in each of which a microspore is produced. In most Monocotyledons the process is one of successive cell-divi- sion. The first division of the spore-mother-cell is followed by the formation of a wall separating the daughter-cells, and the nex
. The classification of flowering plants. Plants. IV] ANGIOSPERMS 147 and appears to contain longitudinal series of pollen-sacs. This occurs in many Leguminosae of the Mimosa section (fig. 68, L) and others, and recalls the segmentation by sterile tissue in the sporangium of Isoetes. Each of the spore-mother-cells divides to form four special mother-cells, in each of which a microspore is produced. In most Monocotyledons the process is one of successive cell-divi- sion. The first division of the spore-mother-cell is followed by the formation of a wall separating the daughter-cells, and the next division follows at right angles to the first, and so that the four special mother-cells lie in one plane (bilateral development) (fig. 68, B). In the submerged marine Monocotyledon, Zostera, the. Fig. 68. A—D. Najas jiexilis. After Campbell. A. Rudiment of male flower; s, spathe; p, perianth; sp, sporogenous cells. B. Division of pollen- mother-cell. C. Germination of pollen-grain; a, autheridial cell; t, tube-cell. D. Germination of pollen-grain shewing two male-cells, $ . E. Same process in Sparganium simplex; p, prothallial cell. After Campbell. F. Transverse section through a young anther shewing division of periblem cell to form archesporial cell (a, shaded) and wall-cell (iv). G, later stage shewing division of archesporial cell (dark-lined) in two corners of a half- section. H. Longitudinal section at still later stage shewing row of sporogenous cells (dark-lined) and tapetal layer (t). A—H all much enlarged. I. Transverse section through young half-anther of Wallflower; m, pollen- mother-cells which are now dividing; t, tapetal layer; x 75. J. A similar section from a dehisced anther, the wall between the two pollen-sacs has broken down; /, fibrous layer ; x 22. K. Three pollen-mother-cells from I shewing three stages of division, x 225. I, J, K, after Scott. L. Anther of Parkia auriculata (Mimoseae) with 11 pollen-groups in longitudinal series in each anther-seg
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1904
