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Usnea is a genus of fruticose lichens in the large family Parmeliaceae. The genus, which currently contains roughly 130 species, was established by Michel Adanson in 1763. Species in the genus grow like leafless mini- shrubs or tassels anchored on bark or twigs.
Its undifferentiated thallus is an irregular mix of fungal hyphae and scattered photobiont cells, lacking a cortex or any definable layers. [6] [47] Morphologically, it is the simplest growth form. [48] The cell walls of leprose lichens contain chemical compounds which make them hydrophobic, and thus largely water repellent. However, the lack ...
A more precise definition has been suggested by Aptroot and Lücking, who propose that the term applies to ascomata and pseudostromata that are more than 1/2 to 3/4 above the level of the thallus. [179] esorediate Also esorediose. Lacking soredia. [180] eucortex Plural eucortices or eucortexes. A cortex made of well-differentiated tissue. [181]
The Parmeliaceae is a large and diverse family of Lecanoromycetes.With over 2700 species [2] in 71 genera, it is the largest family of lichen-forming fungi.The most speciose genera in the family are the well-known groups: Xanthoparmelia (822 species), Usnea (355 species), Parmotrema (255 species), and Hypotrachyna (262 species).
This diversity within a single thallus creates a spectrum of microenvironments, which may contribute to the diversification of fungal life strategies. For example, certain lichen-associated fungi specialise in colonising epinecral layers or epicortices , structures lacking living host cells.
Parmelia species have a foliose (leafy) thallus with a substrate attachment ranging from loose to tight. The lobes comprising the thallus are rounded, more or less straight, and may be contiguous or overlapping (imbricate). The texture of the upper thallus ranges from smooth to foveolate (covered with puts and depressions).
Usnea sphacelata is a species of saxicolous (rock-dwelling), fruticose lichen in the large family Parmeliaceae. It is found in both polar regions of Earth , as well as in southern and northern South America and in New Zealand.
Crust-like or having a hard surface layer, e.g. in a sporocarp; in lichens, a thallus firmly fixed to the substratum by the whole of their lower surface, generally lacking a distinct lower cortex. [84] cyphella . pl. cyphellae. A break in the lower cortex of a lichen thallus which appears as a cup-like structure or marking. Characteristic of ...