. A text-book of botany for secondary schools. Botany. ALG^ 103. Fig. 95.—Pleurococcus: A, the adult plant, with its nucleus ; B-E, various stages of division in pro- ducing new cells; F, colonies of cells that have remained in contact. two daughter cells have not yet rounded off or separated; so that they appear as two halves of the parent cell. Even before they sepa- rate they may di- vide again, and thus a group of cells may be formed. Pleuro- coccus, therefore, is another illustra- tion of an extreme- ly simple plant, in that it consists of one cell and repro- duces by cell-divi- sion. It
. A text-book of botany for secondary schools. Botany. ALG^ 103. Fig. 95.—Pleurococcus: A, the adult plant, with its nucleus ; B-E, various stages of division in pro- ducing new cells; F, colonies of cells that have remained in contact. two daughter cells have not yet rounded off or separated; so that they appear as two halves of the parent cell. Even before they sepa- rate they may di- vide again, and thus a group of cells may be formed. Pleuro- coccus, therefore, is another illustra- tion of an extreme- ly simple plant, in that it consists of one cell and repro- duces by cell-divi- sion. It would be hard to imagine a simpler plant, and the plant kingdom can be thought of as beginning with individ- uals consisting of one green cell and reproducing by divi- sion. This one cell, however, absorbs material, makes food, assimilates it, conducts respiration, etc.; in fact, does all the work of living carried on by plants with roots, stems, and leaves, although they may contain millions of cells. 64. The plant cell.—Pleurococcus may be used to illus- trate the conspicuous features of a living plant cell. Bound- ing the cell there is a thin, elastic cell-wall, composed of a substance called cellulose. The cell-wall, therefore, con- stitutes a delicate sac, which contains the living substance known as •protoplasm. It is the protoplasm that has formed the wall about itself, in the same sense that a snail deposits the shell about its body. The protoplasm is organized into various structures which are called organs of the cell. One of the most conspicuous protoplasmic organ-s is the nucleus, a comparatively compact and usually spherical body, and generally centrally placed within the cell (Fig. 95, A),. 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 Coulter, John Merle, 1851-1928. New York, D. Applet
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