. Elements of plant anatomy;. Botany -- Anatomy. 56 ELEMENTS OF PLANT ANATOMY. tissue. There are a few exceptions to these rules ; for example, the thorns of the genus Rubus are trichomes, while the hairs of the stinging nettle, the gland-hairs of the rose and even the Scales of some plants are really outgrowths. According to their function they may be classed : first, as secretory hairs or glands, seconr" those which protect from too low a temperature, third, those which prevent too great evaporation. The first class includes those trichomes or outgrowths which secrete fluid or half-flui
. Elements of plant anatomy;. Botany -- Anatomy. 56 ELEMENTS OF PLANT ANATOMY. tissue. There are a few exceptions to these rules ; for example, the thorns of the genus Rubus are trichomes, while the hairs of the stinging nettle, the gland-hairs of the rose and even the Scales of some plants are really outgrowths. According to their function they may be classed : first, as secretory hairs or glands, seconr" those which protect from too low a temperature, third, those which prevent too great evaporation. The first class includes those trichomes or outgrowths which secrete fluid or half-fluid substances of peculiar character which are generally discharged on the surface of the organ. The second, includes many short- lived hairs which die and drop off on the maturity of the organ which they pro- tect. Such are the hairs of the plane tree (Platanus) buds, supposed to fall in such quantities as to produce throat and lung diseases. Many others might be cited as to this category. The third class comprises those hairs which grow so thickly over .the surface and become so matted together that the German botanists have given this covering the name Filz, or felt. In this sense the tevm. felt may be defined as a hair covering whose threads are so closely matted together as to leave only capillary interstices. Lastly it is believed that this felt covering has another function, namely to convey water in a liquid form to the stomata ; there are also several other arrangements of hairs supposed to promote this process, such as little tufts in the angles of the leaf-veins, Hair from under epidermis of leaf of Phlomis Jlusseliana, partly diagrammatic, a a simple belonQ^inP" pores. X Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gregory, Emily L. Boston, London, Ginn & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotanya, bookyear1895
