. A textbook of botany for colleges and universities ... Botany. THE MATERIAL INCOME OF PLANTS 301 among the ])articles and scjiaratcs them more or less \\'idely. But there comes a limit to the swelling, and no more water enters. If it is removed, the body regains its form and the particles, presumably, their identical position. In solution there is no limit to separation, except by the amount of water present; and when it is removed, the particles rearrange themselves in forms which may be similar to those of the original body, but are obviously not identical with them. Yet swelling may becom
. A textbook of botany for colleges and universities ... Botany. THE MATERIAL INCOME OF PLANTS 301 among the ])articles and scjiaratcs them more or less \\'idely. But there comes a limit to the swelling, and no more water enters. If it is removed, the body regains its form and the particles, presumably, their identical position. In solution there is no limit to separation, except by the amount of water present; and when it is removed, the particles rearrange themselves in forms which may be similar to those of the original body, but are obviously not identical with them. Yet swelling may become excessive, as when starch grains are put into hot water or alkalies, and after certain limits are passed the swollen grain will not regain its normal form. By such transitions imbibition merges almost insensibly into solution. Relations of inner and outer water. — For further understanding it is useful to attempt to picture the relations of the water to the other com- ponents of a young cell immersed in natural water. The outside water has particles of many sorts scattered through it; for no matter how pure, in nature all water is really a dilute solution of various substances. The water of the cell wall has so many par- ticles of cell-wall stuff scattered through it that nearly half the volume is cellulose; but it is con- tinuous with the water outside. The water of the cytoplasm and of its inclusions is freer of these substances, it is more nearly pure, because the cytoplasmic particles form only about one fifth of the whole mass. This water, too, is con- tinuous with the water of the cell wall, and with that of the solution outside. The water of the vacuole is still less encumbered with other particles, only one or two per cent, perhaps, but these are of diverse kinds, for the cell sap is a solution of many things. The water here is likewise continuous with that outside through the cytoplasm and wall (fig. 620). Continuity of water.—The picture sketched above may
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
