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Crustose lichens form a crust that strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure is composed of a cortex layer, an algal layer, and a medulla. The upper cortex layer is differentiated and is usually pigmented. The algal layer lies beneath the cortex. The medulla fastens the lichen to the substrate and is made up of fungal hyphae. The surface of crustose lichens is characterized by branching cracks that periodically close in response to climatic variations such as alternate wetting and drying regimes. ==Subtypes== * Powdery – considered as the simplest subtype due to the absence of an organized thallus. :The thallus appears powdery.〔 :E.g. Genera ''Lepraria'', ''Vezdaea'' * Endolithic – grows inside the rock, usually in interstitial spaces between mineral grains. The :upper cortex is usually developed.〔 :E.g. Genus ''Lecidea'' * Epilithic – grows on top of the rock without penetrating the rock substrate.〔 :E.g. ''Acarospora fuscata'' * Epiphloeodal – grows only on the surface of plants.〔 :E.g. ''Lecania naegelii'' * Endophloeodic – grows underneath the cuticle of leaves or stems.〔 :E.g. ''Amandinea punctata'' * Squamulose – has a scale-like appearance resulting from partial separation from substrate. :It is an intermediate form between crustose and foliose.〔 :E.g. Genus ''Psora, Catapyrenium, Coriscium'' * Peltate – similar to squamulose, but thallus remains attached near the central area.〔 :E.g. ''Peltula euploca'' * Bullate – has an extremely inflated appearance.〔 :E.g. Genus ''Mobergia'' * Effigurate - has radially arranged marginal lobes that are prolonged.〔 :E.g. Genera ''Acarospora, Pleopsidium'' * Lobate – characterized by a thallus that radially arranged with lobes that are partially raised.〔 :E.g. Genera ''Caloplaca, Lecanora'' * Suffruticose – clusters of coralloid cushions.〔 :E.g. ''Peltula clavata'' Lepraria incana G34.JPG|''Lepraria incana'', a powdery lichen Brown Tile and Gold Cobblestone Lichens (5037667763).jpg|''Lecidea atrobrunnea'', an endolithic lichen Acarospora K. Brodzińskiego.JPG|''Acarospora fuscata'', an epilithic lichen Amandinea punctata 2 - Lindsey.jpg|''Amandinea punctata'', an endophloedic lichen Psora decipiens 300406a.jpg|''Psora decipiens'', a squamulose lichen Peltula euploca Jymm.jpg|''Peltula euploca'', a peltate lichen Gold Cobblestone Lichen (4752151307).jpg|''Acarospora socialis'', an effigurate lichen Lecanora.dispersa2.-.lindsey.jpg|''Lecanora dispersa'', a lobate lichen 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「crustose lichen」の詳細全文を読む スポンサード リンク
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