. Elements of botany. Plants. SOME TYPES OF FLOWERLESS PLANTS. 223 which result in the division of the protoplasmic contents of a cell into two independent portions, each of which is at length surrounded by a complete cell wall of its oAvn. In Fig. 193 the division of the protoplasm and formation of a partition of cellulose in a kind of pondscum are shown, but the nucleus and its changes are not represented. Another kind of reproduction, namely by conjugation, is found in Spirogyra. This process in its simplest form is found in such unicellular plants as the desmids, Fig. 194. Two cells (appar
. Elements of botany. Plants. SOME TYPES OF FLOWERLESS PLANTS. 223 which result in the division of the protoplasmic contents of a cell into two independent portions, each of which is at length surrounded by a complete cell wall of its oAvn. In Fig. 193 the division of the protoplasm and formation of a partition of cellulose in a kind of pondscum are shown, but the nucleus and its changes are not represented. Another kind of reproduction, namely by conjugation, is found in Spirogyra. This process in its simplest form is found in such unicellular plants as the desmids, Fig. 194. Two cells (apparently precisely alike) come in con- tact, undergo a thinning-down or ab- sorptive process in the cell walls at the point of contact, and finally blend their protoplasmic cell-contents, as shown in the fig-ure, to form a mass known as a spore, or more accurately a zygospore, from which a new individual soon. Fig. 193.— Process of Cell-3rulti- plication in a Species of Pond- scum. (Considerably magnified.) A, portion of a filament partly separated at a and completely so at 6 ; B, separation nearly com- pleted, a new partition of cellu- lose formed at a; C, another portion, more magnified, show- ing mucous covering d, general cell wall c, and a delicate mem- brane a, which covers the cell- contents Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917; Bergen, Joseph Y. (Joseph Young), 1851-1917. Bergen's Botany: key and flora, Pacific coast ed. Boston : Ginn
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
