Elementary biology; an introduction to Elementary biology; an introduction to the science of life elementarybiolog00grue Year: 1924 348 ELEMENTARY BIOLOGY new cells ; these die as they are moved toward the surface by the newer cells beneath, becoming a layer of dead scales. The skin protects the animals not only against mechanical injury but also against the loss of water and against the absorption of water, for the skin is practically waterproof, being Fig. 163. Mullein in pasture These plants are closely covered with fine, branching hairs, giving the leaf a flannellj texture. We can well
Elementary biology; an introduction to Elementary biology; an introduction to the science of life elementarybiolog00grue Year: 1924 348 ELEMENTARY BIOLOGY new cells ; these die as they are moved toward the surface by the newer cells beneath, becoming a layer of dead scales. The skin protects the animals not only against mechanical injury but also against the loss of water and against the absorption of water, for the skin is practically waterproof, being Fig. 163. Mullein in pasture These plants are closely covered with fine, branching hairs, giving the leaf a flannellj texture. We can well imagine that a cow would not care to eat anything that felt like flannel in the mouth, and so we can understand that the hairy growth may actually protect the plants against grazing animals. (From photograph by Dr. H. A. Kelly) more or less oily (see p. 206). It also protects, to a certain degree, against too rapid changes of temperature. In this function many skins are supplemented by layers of fat on the inside and by hairs or fur on the outside. 399. Hairs and other outgrowths. On the leaves and stems of plants the cells of the epidermis enlarge at right angles to the surface. This mode of growth results in the formation of hairs (see Figs. 162, 163).
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