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The thallus of a crustose lichen is usually only discernible because of the discolouration of the substrate. Some crustose lichens have thalli consisting of scattered or loosely grouped granules. Crustose lichens differ from the leprose lichen by having an upper cortex and algal cells that are located directly beneath the cortex. The thallus of ...
Lichen growth forms are used to group lichens by "vegetative" thallus types, and forms of "non-vegetative" reproductive parts. Some lichen thalli have the aspect of leaves (foliose lichens); others cover the substrate like a crust (crustose lichens) (illustration, right), others such as the genus Ramalina adopt shrubby forms (fruticose lichens ...
Usnea filipendula – one of about 20,000 described species of lichen. The following outline provides an overview of and topical guide to lichens.. Lichen – composite organism made up of multiple species – a fungal partner, one or more photosynthetic partners, which can be either green algae or cyanobacteria, and, in at least 52 genera of lichens, a yeast. [1]
Leprose lichens consist of crusts without a layered structure. [4] Crustose lichens have learned to adapt to their environment, with the shells helping with adaptation to dry and drought resistant climates. Crustose lichens have been found in deserts, ice free parts of Antarctica, and in the Alpine and Arctic regions. [5]
But these leafy parts lack a lower cortex, which distinguishes crustose and squamulose lichens from foliose lichens. [44] Conversely, foliose lichens may appear flattened against the substrate like a crustose lichen, but most of the leaf-like lobes can be lifted up from the substrate because it is separated from it by a tightly packed lower cortex.
[23] [24] Crustose lichens lack a lower cortex, though most have an upper cortex. 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]
Following standard practice in botanical nomenclature, [6] the name Roccellaceae is derived from the type genus Roccella, with the suffix -aceae denoting its rank as a family. . The genus name Roccella probably originates from the Italian word roccella, a common name for lichens, itself derived from the Latin rocca (meaning ' rock ') with the diminutive suffix-e
Lepraria is a genus of leprose (powdery) crustose lichens that grows on its substrate like patches of granular, caked up, mealy dust grains. [2] [3] Members of the genus are commonly called dust lichens. [3]: 305 [4] [5] The main vegetative body is made of patches of soredia (little balls of algae wrapped in fungus). [3]