. Lessons in botany. Botany. 3o BOTANY. pressure from within, but a point is soon reached beyond which it will not stretch, and an equilibrium then tends to be established between the pressure from within on the protoplas- mic membrane, and the pressure from without by the elastic cell wall. This state of a cell is turgescence, or such a cell is said to be turgescenl, or turgid. Demonstration 12. 60. Experiment to show diffusion through an animal membrane.—For this experiment use a thistle tube, across the larger end of which should be stretched and tied tightly a piece of bladder mem- brane.
. Lessons in botany. Botany. 3o BOTANY. pressure from within, but a point is soon reached beyond which it will not stretch, and an equilibrium then tends to be established between the pressure from within on the protoplas- mic membrane, and the pressure from without by the elastic cell wall. This state of a cell is turgescence, or such a cell is said to be turgescenl, or turgid. Demonstration 12. 60. Experiment to show diffusion through an animal membrane.—For this experiment use a thistle tube, across the larger end of which should be stretched and tied tightly a piece of bladder mem- brane. A strong sugar solution (three parts sugar to one part water) is now placed in the tube so that the bulb is filled and the liquid extends part way in the neck of the tube. This is immersed in water within a wide-mouth bottle, the neck of the tube being supported in a perforated cork in such a way that the sugar solution in the tube is on a level with the water in the bottle or jar. In a short while the liquid begins to rise in the thistle tube, in the course of several hours having risen several centimeters. The diffusion current is thus stronger through the membrane in the direction of the sugar solution, so that this gain? more water than it loses. 61. How diffusion takes place.—We have here two liquids separated by an animal membrane, water on the one hand which diffuses readily through the membrane, while on the other is a solution of sugar which dif- fuses through the animal membrane with difficulty. The water, therefore, not contain- ing any solvent, according to a general law which has been found to obtain in such cases, diffuses more readily through the membrane into the sugar solution, which thus increases in volume, and also becomes more dilute. The bladder membrane is what is sometimes called a diffusion mem- brane, since the diffusion currents travel through it. In this ex- periment then the bulk of the sugar solution is increased, and the. Fig. Please note
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