. A text-book of botany for secondary schools. Botany. ALGiE 115. rounds. In each cell thus connected with another a single large gamete is formed, and one of them passes through the connecting tube to the other. The gametes are similar, and their fusion results in a heavy-walled oospore (Fig. 104, D), which endures through the winter and germinates during the following season. Plasmolysis.—Spirogyra is a very favorable form for demonstrating plasmolysis, which means the shrinkage of protoplasm from loss of water. The cytoplasm of an active cell is full of water, which often col- lects in drop
. A text-book of botany for secondary schools. Botany. ALGiE 115. rounds. In each cell thus connected with another a single large gamete is formed, and one of them passes through the connecting tube to the other. The gametes are similar, and their fusion results in a heavy-walled oospore (Fig. 104, D), which endures through the winter and germinates during the following season. Plasmolysis.—Spirogyra is a very favorable form for demonstrating plasmolysis, which means the shrinkage of protoplasm from loss of water. The cytoplasm of an active cell is full of water, which often col- lects in droplets of vary- ing size, called vacuoles. There is always a layer of cytoplasm in close con- tact with the cell-wall, but the interior of the cell may be one large vacuole traversed by strands of cytoplasm, as in Spirogyra. The turgor of the cell (§ 64) keeps the elastic wall distended; but if the cell be put in a solution of sugar, water will be withdrawn. The vacuoles thus beginning to lose their water, the cytoplasm shrinks; and if the loss continues, the vacuoles are obliterated, and the layer of cytoplasm in contact with the wall separates from it, all the cytoplasm of the cell contracting into a compact mass (Fig. 106). The name plasmolysis really means the " loosen- ing" of the "plasma" (protoplasm) from the wall. Any- thing that withdraws water from a cell plasmolyzes it, and the filamentous Algffi are favorable forms for experiments to show this. 70. Conclusions.—The green Algae are so named because the green of the chloroplasts is neither modified nor obscured Fig. 106.—Plasmolysis: A. a cell of Spirogyra before plasmolysis; B, the same cell after plasmolysis with a ten per cent solution of 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, 1851-19
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
