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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 ...
The thallus is different from those of either the fungus or alga growing separately. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations. In many species the fungus penetrates the algal cell wall, forming penetration pegs or haustoria similar to those produced by pathogenic fungi.
Letharia vulpina, a species of fruticose lichen. A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure.It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteria and one, two or more mycobionts. [1]
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).
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]
The definition finally adopted was that lichen could be considered as the association between a fungus and a photosynthetic symbiont resulting in a thallus of specific structure. [ 26 ] Such a simple a priori definition soon brought criticism from various lichenologists and there soon emerged reviews and suggestions for amendments.
A lichen thallus or structure that is cracked, split, spongy, or otherwise decayed or in a state of disintegration. [43] cartilaginous Also cartilagineus. A term used to describe the texture of certain parts of a lichen. Cartilaginous structures have a texture similar to animal cartilage – firm but somewhat pliable, not brittle or soft. [86 ...