Introduction to structural and systematic botany, and vegetable physiology, : being a 5th and revedof the Botanical text-book, illustrated with over thirteen hundred woodcuts . roduction essentially depends upon the mingling of the materialsof two distinct cells (as the pollen-cell and the embryonal vesicle,579) ; and these cells in the lowest forms of vegetation representindividual plants. The simplest mode of such reproduction in thelowest plants, and that longest known, is what has been termed 655. Conjugation. This is the mode in which two vast tribes ofmicroscopic one-celled aquatic plant
Introduction to structural and systematic botany, and vegetable physiology, : being a 5th and revedof the Botanical text-book, illustrated with over thirteen hundred woodcuts . roduction essentially depends upon the mingling of the materialsof two distinct cells (as the pollen-cell and the embryonal vesicle,579) ; and these cells in the lowest forms of vegetation representindividual plants. The simplest mode of such reproduction in thelowest plants, and that longest known, is what has been termed 655. Conjugation. This is the mode in which two vast tribes ofmicroscopic one-celled aquatic plants, the Desmidiaceaa and Diato- maceoe, are reproduced. They multi-ply rapidly, and apparently withoutJimit, by successive division into twoequal parts, which separate, each be-coming like the original. But at lengthtwo of these individuals, being en-dowed with the power of movement,come into contact; the firm or oftensilicious cell-wall ruptures or givesway in a definite manner at the placeof junction, and the whole contents ofthe two conjugating cells or individu-als are commingled into one mass ofprotoplasm, &c.; this soon has a coat of cellulose formed around it,. FIG. 631. Magnified individual of Closterium aeutum, after Ilalfs. 632. Two individualsmore magnified, in conjugation ; their cells opening one into the other, and the contents min-gled ; in 633, condensing ; in 634, collected and formed into a spore. CRYPTOGAMOUS OR FLOWERLESS PLANTS. 333 and is new a spore, which when it grows begins a new series of in-dividuals developed by successive division. 656. In Algae consisting of a Single Row of Cells one tribe presents the same mode of reproduction, and the various species of Zygnemaor Spirogyra, found in almost every pool of freshwater at different times in spring and summer,afford the readiest illustrations of conjugation,which low powers of the microscope suffice toexhibit. These green threads when magnifiedare seen to consist of single rows of cylindricalcells join
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Keywords: ., bookauthorgra, bookcentury1800, bookdecade1860, booksubjectbotany
