Elementary botany . Fig. 13. Spirogyra from salt solution into water. Fig. in $% salt solution. 31. Turgescence.—Were it not for the resistance which thecell wall offers to the pressure from within, the delicate proto- ABSORPTION, DIFFUSION, OSMOSF. *5 plasmic membrane would stretch to such an extent that it wouldbe ruptured, and the protoplasm therefore would be killed. Ifwe examine the cells at the ends of thethreads of spirogyra we shall see in mostcases that the cell wall at the free end isarched is broughtabout by the press-. Fig. i4. Before treatment with saltso
Elementary botany . Fig. 13. Spirogyra from salt solution into water. Fig. in $% salt solution. 31. Turgescence.—Were it not for the resistance which thecell wall offers to the pressure from within, the delicate proto- ABSORPTION, DIFFUSION, OSMOSF. *5 plasmic membrane would stretch to such an extent that it wouldbe ruptured, and the protoplasm therefore would be killed. Ifwe examine the cells at the ends of thethreads of spirogyra we shall see in mostcases that the cell wall at the free end isarched is broughtabout by the press-. Fig. i4. Before treatment with saltsolution. ure from within Fig. 15. After treatment with salt solution. Fig. 16. From salt solution placed in water. Figs. 14-16.—Osmosis in threads of mucor. upon the proto-plasmic m e m -brane which itself presses againstthe cell wall, and causes it toarch outward. This is beauti-fully shown in the case of threadswhich are recently broken. The cell wall is therefore elastic;it yields to a certain extent to the pressure from within, but apoint is soon reached beyond which it will not stretch, and anequilibrium then exists between the pressure from within on theprotoplasmic membrane, and the pressure from without by theelastic cell wall. This state of equilibrium in a cell is turges-cence, or such a cell is said to be turgescent, or turgid. 32. Experiment with beet in salt and sugar solutions.—We may now test the effect of a five per cent salt solution on aportion of the tissues of a beet or carrot. Let us cut severalslices of equal size and about
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