. Elementary botany. Botany. ABSORPTION, DIFFUSION, OSMOSE. *5 plasmic membrane would stretch to such an extent that it would be ruptured, and the protoplasm therefore would be killed. If we examine the cells at the ends of the threads of spirogyra we will see in most cases that the cell wall at the free end is arched outward. T his is brought about by the press-. Fig. 16. From salt solution placed in water. Figs. 14-16.—Osmosis in threads of mucor. Fig. 14. Before treatment with salt solution. lire from within upon the proto- After j^Lent with plasmic m e m - salt solution- brane which itself
. Elementary botany. Botany. ABSORPTION, DIFFUSION, OSMOSE. *5 plasmic membrane would stretch to such an extent that it would be ruptured, and the protoplasm therefore would be killed. If we examine the cells at the ends of the threads of spirogyra we will see in most cases that the cell wall at the free end is arched outward. T his is brought about by the press-. Fig. 16. From salt solution placed in water. Figs. 14-16.—Osmosis in threads of mucor. Fig. 14. Before treatment with salt solution. lire from within upon the proto- After j^Lent with plasmic m e m - salt solution- brane which itself presses against the cell wall, and causes it to arch outward. This is beauti- fully shown in the case of threads which are recently broken. The cell wall is therefore elastic; it yields to a certain extent to the pressure from within, but a point is soon reached beyond which it will not stretch, and an equilibrium then exists between the pressure from within on the protoplasmic membrane, and the pressure from without by the elastic cell wall. This state of equilibrium in a cell is turges- cence, or such a cell is said to be turgescent, or iurgid. 32. Experiment with beet in salt and sugar solutions.— We may now test the effect of a five per cent salt solution on a portion of the tissues of a beet or carrot. Let us cut several slices of equal size and about $mm in thickness. Immerse a few slices in water, a few in a five per cent salt solution and a few in a strong sugar solution. It should be first noted that all the slices are quite rigid when an attempt is made to bend them between the fingers. In the course of one or two hours or less,. 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 Atkinson, George Francis, 1854-1918. New York, H. Holt and company
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