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partial veil
In mycology, a partial veil (also called an inner veil, to differentiate it from the "outer" veil, or velum〔) is a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics. Its role is to isolate and protect the developing spore-producing surface, represented by gills or tubes, found on the lower surface of the cap. A partial veil, in contrast to a universal veil, extends from the stem surface to the cap edge. The partial veil later disintegrates, once the fruiting body has matured and the spores are ready for dispersal. It might then give rise to a stem ring, or fragments attached to the stem or cap edge. In some mushrooms, both a partial veil and a universal veil may be present.〔
==Structure==
In the immature fruit bodies of some basidiomycete fungi, the partial veil extends from the stem surface to the cap margin and shields the gills during development, and later breaks to expose the mature gills. The presence, absence, or structure of the partial veil is an aid to identification of mushrooms.〔Arora (1986), p. 16.〕 Some fruit bodies may have both a universal and partial veil, others may have only one or the other, while many lack both types of veils. The partial veil may be membranous or cobwebby, and may have multiple layers. Various adjectives are commonly used to describe the texture of partial veils, such as: ''membranous'', like a membrane; ''cottony'', where the veil tissue is made of separate fibers that may be easily separated like a cotton ball; ''fibrillose'', composed of thin strands and ''glutinous'', with a slimy consistency. Some mushrooms have partial veils which are ''evanescent'', which are so thin and delicate that they disappear after they rupture, or leave merely a faint trace on the stem known as an ''annular zone''〔 or ''ring zone''.〔 Others may leave a persistent annulus (ring). Occasionally, the partial veil adheres to the edge of the cap as shreds of tissue, forming an ''appendiculate'' margin.
The cobweb-like, fragile partial veil of some mushrooms, especially those in the genus ''Cortinarius'', are known as ''cortinas''. The fibrous threads of the cortina often catch the brown spores as they drop, making them visible as fine brown streaks along the stem. Some species of ''Agaricus'', such as ''Agaricus arvensis'', have a partial veil that resembles a cogwheel.〔 Mycologists Alexander H. Smith and Harry D. Thiers, in their 1964 monograph on the bolete genus ''Suillus'', proposed the term "false veil" to account for those species of ''Suillus'' that have a "conspicuous cottony roll" of tissue that originates from the cap margin (especially in young specimens) and never becomes integrated with the stem tissue.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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