General physiology; an outline of the science of life (1899) (14802782213)

Identifier: generalphysiolo00verw (find matches)
Title: General physiology; an outline of the science of life
Year: 1899 (1890s)
Authors: Verworn, Max, 1863-1921 Lee, Frederic S. (Frederic Schiller), 1859-1939, ed. and tr
Subjects: Physiology
Publisher: London, Macmillan and co., limited New York, The Macmillan company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons



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y adapted to life in long drought, and they manage ex-tremely frugally and economically with the little water that comesto hand at long intervals of time. One is astonished in the driestdesert to come upon green plants that contain abundant juices,plants (Mescmbryantheiimm crystallinum) beset over and over withcells, which harbour such quantities of clear water that the latter 280 GENERAL PHYSIOLOGY appear like small crystal droplets (Fig. 127). These desert-plantshave a remarkable power of retaining water, either by storing up intheir cell-sap soluble substances that possess great attraction forwater, or by being covered over their whole surface with a fine layerof wax, so that with the stomata closed scarcely a trace of water canpass by evaporation out of the plant-body. Moreover, they possessusually much-branched roots extending very far and superficially inthe soil, and these greedily suck up every trace of water thatmoistens the earth. The desert-animals also, such as the snails,
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Fig. 127.—Mesembryanthemum crystallinvm, a desert-plant from Southern Africa. The whole stemand the under side of the leaves are beset with clear crystal-like water-cells. which are confined to their dry home because of their slight powersof locomotion, protect themselves by limiting their excretion ofwater to a minimum. The snails close the opening of their shellswith a thick, double cover, so that scarcely a trace of water can belost from the body by evaporation. Hence, in all these cases thedryness of the environment does not extend to the living sub-stance of the organisms. On the contrary, here, as everywhere,the living substance is liquid, and in fact all desert-organismshave an actual, not a latent, life, although their life is depressed to aminimum. They show directly how the intensity of life increases THE GENERAL CONDITIONS OF LIFE 281 and decreases with the rise and fall of the water-contents. If aslight shower of rain comes, activity immediately begins, theplants grow an