This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 Excerpt: ...meantime withdraw themselves from the wall, and form a free, rounded protoplasmic body--the ovum (see Fig. 69, A)--in the upper part of which the nucleus is placed. The oogonium now opens, either by the formation of a round hole in the membrane, or by the transverse splitting of the cell-wall near the top, in which ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 Excerpt: ...meantime withdraw themselves from the wall, and form a free, rounded protoplasmic body--the ovum (see Fig. 69, A)--in the upper part of which the nucleus is placed. The oogonium now opens, either by the formation of a round hole in the membrane, or by the transverse splitting of the cell-wall near the top, in which case the upper part of the membrane acts as a lid (Figs. 66 and 69, A). The gap is at first closed by a new membrane formed from the adjacent protoplasm of the oogonium, but this soon disappears again, leaving a free passage to the ovum. Before describing the mode of fertilisation, we will consider the peculiar distribution of the sexes already mentioned, as differing from the ordinary monoecious and dioecious conditions. It is this form which our figures illustrate. The peculiarity consists in the production of dwarf male plants quite different from the ordinary form of the species. By repeated transverse divisions in parts of the filament a chain of small cells is produced much shorter than the ordinary vegetative cells of the plant. Each of these short cells becomes the mothercell of a single zoospore of the usual structure, but of a size intermediate between a normal vegetative zoospore and a spermatozoid (Fig. 68, an). These small spores (called androspores) are most commonly produced from the same filaments which bear the oogonia; more rarely they occur on distinct filaments. Each androspore swims about for a time, and then comes to rest, attaching itself to the female plant either near or actually upon the oogonium Fig. 68.--Androspore (on) of (Edogonium ciliatum escaping. At? is an oogonium. Magnified 350. (After Pringsheim.) (Figs. 66 and 69, A). The androspore surrounds itself with a cell-wall and germinates. The plant which it produces...
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