TRICHOME (from Gk. rpixwpa, trichoma, growth of hair, from rpixoiv, trichoun, to fur nish with hair, from 014, Avis, hair). A hair like outgrowth from the epidermis of plants, usually arising from a single cell. These struc tures are known variously as hairs, glands, bris tles, bladders, scales, prickles, warts. etc.. and may be one or many celled. The long hairs on the seeds of cotton are simple and unicel lular. The filaments on the stamens of the spider lily (Tradescantia) are multicellular and Simple. Branched unicellular hairs may be found on the common shepherd's purse (Capsella) and branched multicellular hairs on mullein. Hairs with flattened expansions at -the top are called scales. Glandular hairs are widely distributed among plants, being usually unbranched and with a knob at the apex, which secretes such sub stances as resins, gums, ethereal oils, mucilage, and sugar. 'When the substance is secreted in a
liquid form it moistens the surface, but when volatile it is recognized as an odor. Root-hairs are one-celled outgrowths from the epidermis of the root, having very delicate walls. Their office is to absorb nutritive materials for the plants. Nany plants and organs which bear hairs during early stages of development become smooth as they grow older. Environment also affects the hairiness of a structure. A plant growing in a very dry situation may be hairy, while another individual of the same species growing in a wet situation may be much less hairy or even entire ly smooth. Systematists have made large use of the trichome in describing plants, and have de veloped a large number of descriptive terms.