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''Usnea'' is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs.〔Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, ISBN 978-0-300-19500-2〕 The genus is in the Parmeliaceae family. It grows all over the world. Members of the genus are commonly called tree's dandruff, woman's long hair, or tree moss,, old man's beard, or beard lichen.〔 It resembles ''Evernia'', which is also called tree moss. Like other lichens it is a symbiosis of a fungus and an alga. The fungus belongs to the division Ascomycota, while the alga is a member of the division Chlorophyta. Members of the genus are similar to those of the genus ''Alectoria''.〔 A distinguishing test is that the branches of ''Usnea'' are somewhat elastic, but the branches of ''Alectoeria'' snap cleanly off.〔 ==Morphology and reproduction== As a fruticose lichen, ''Usnea'' appears as a shrub-like growth on host trees. Unlike other similar-looking fruticose lichens, species in this genus have an elastic chord or axis running through the middle of the thallus that can be revealed by gently pulling a filament apart from either end. It reproduces via vegetative means through fragmentation, asexual means through soredia, or sexual means through ascogonium and spermatogonium. The growth rate of lichens in nature is slow, but the growth rate has been sped up in laboratory conditions where ''Usnea'' is being cultured. ''Usnea'' looks very similar to the plant Spanish moss, so much so that the latter's Latin name is derived from it (''Tillandsia usneoides'', the 'Usnea-like Tillandsia'). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Usnea」の詳細全文を読む スポンサード リンク
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