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A crustose lichen, Caloplaca marina. Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. Crustose adheres very closely to the substrates at all points. Crustose is found on rocks and tree bark. [1]
Crustose lichens are lichens that form a crust which strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. [1] The basic structure of crustose lichens consists of a cortex layer, an algal layer, and a medulla.
In lichens that include both green algal and cyanobacterial symbionts, the cyanobacteria may be held on the upper or lower surface in small pustules called cephalodia. Beneath the upper cortex is an algal layer composed of algal cells embedded in rather densely interwoven fungal hyphae.
The photobiont layer lies just below the upper cortex. [25] Many crustose lichens have a ring of unlichenised fungal hyphae at their edges. This fringe, known as a prothallus, may be black, white or the same colour as the rest of the thallus. [26] The term "crustose" derives from the Latin crustosus, meaning "crusted". [27]
A layer of dead hyphae with indistinct lumina found near the cortex and below the algal layer. [172] See related: epinecral layer. hypophloeodic Also hypophloeodal. Refers to crustose lichens whose thalli are almost immersed in tree bark; characteristic of several species in the Thelenellaceae. [250] The term was first used by Friedrich ...
Buellia frigida is a species of saxicolous (rock-dwelling), crustose lichen in the family Caliciaceae.It was first described from samples collected from the British National Antarctic Expedition of 1901–1904.
In crustose and foliose lichens, algae in the photobiontic layer are diffuse among the fungal filaments, decreasing in gradation into the layer below. In fruticose lichens, the photobiontic layer is sharply distinct from the layer below. [35] The layer beneath the symbiont layer is called the medulla. The medulla is less densely packed with ...
The medulla is the internal layer of fungal hyphae below the cortex and the algal layer; three types occur in the Verrucariaceae. The prosoplectenchymatous type has loosely interlaced hyphae with elongated cells, the paraplectenchymatous type comprises tightly arranged and rounded cells, and the mixed-type medulla has both rounded and elongated ...