. Elements of botany. Botany; Botany. 36 ELEMENTS OP BOTANY. The rise of liquid in the tube is evidently due to water making its way through the thin membrane which lines the egg-shell, although this mem- brane contains no pores visible even under the microscope. 63. Experiment 16. Osmose in a Begonia Leaf. — Place a little powdered sugar on the upper surface of a thick begonia leaf under a small bell glass. Watch for several days to see whether mois- ture from the inside of the leaf affects the sugar. The upper surface of this leaf contains no pores, even of microscopic size. 64. Inequality o
. Elements of botany. Botany; Botany. 36 ELEMENTS OP BOTANY. The rise of liquid in the tube is evidently due to water making its way through the thin membrane which lines the egg-shell, although this mem- brane contains no pores visible even under the microscope. 63. Experiment 16. Osmose in a Begonia Leaf. — Place a little powdered sugar on the upper surface of a thick begonia leaf under a small bell glass. Watch for several days to see whether mois- ture from the inside of the leaf affects the sugar. The upper surface of this leaf contains no pores, even of microscopic size. 64. Inequality of Os^notic Exchange. — The nature of the two liquids separated by any given membrane determines in which direc- tion the greater flow shall take place. If one of the liquids is pure water and the other is water containing solid substances dissolved in it, the greater flow of liquid will be away from the pure water into the solu- tion, and the stronger or denser the latter, the more unequal will be the flow. This principle is well illustrated by the egg-osmose experiment. Another important principle is that substances which readily crystallize, like salt or sugar, pass rapidly through membranes, while jelly-like substances, like white of egg, can hardly pass through them at all. 55. Osmose in Root-Hairs. — It is very easy to understand, from the principles just stated, that the soil-water (which is like ordinary spring or well water), separated by the delicate walls of the root-hairs and a thin lining of jelly-like liv- ing matter from the more or less sugary or mucilaginous sap inside them, will pass rapidly into the plant, while very little of the sap will come out. Probably most of the selective action, which causes the flow of liquid through the root-hairs to be almost wholly inward, is due mainly to the living layer of proteid material known as protoplasm (Chapter XIII), which. Fig. 21. — Egg on Beaker of Water, to show Please note that these images are ext
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