Hale, Mason E., Jr. Formerly, Smithsonian Institution, Washington, DC.
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An order of ascolichens (class Lecanoromycetes, division Ascomycota) characterized by an unusual apothecium. Members of the order Teloschistales (formerly Caliciales) are ascolichens, that is, lichens [symbiotic associations of fungi (mycobionts) and photosynthetic partners (photobionts, including algae and cyanobacteria)] in which the fungus component is an ascomycete (a sac fungi, that is, any fungus of the division Ascomycota). These type of lichens are distinguished by an unusual apothecium (a spore-bearing structure in which the fruiting surface or hymenium is exposed during spore maturation). The hymenial layer originates normally; however, by the time that the spores are mature, the asci and paraphyses have partially disintegrated into a mass of spores and hymenial tissues known as a mazaedium. Most taxonomists assign five families to the order Teloschistales: Caliciaceae, Letrouitiaceae, Megalosporaceae, Physciaceae, and Teloschistaceae (see illustration); two other families, Microcaliciaceae and Ropalosporaceae, may also belong to the order. Together, there are approximately 2000 known species. In the family Caliciaceae, the disk is borne on a short stalk measuring 1–8 mm (0.04–0.32 in.) in height; this peculiar structure is also observed in members of the nonlichenized Roesleriaceae. These two families are so close that some species in either one may or may not lichenize symbiotic algae. The primary thallus of members of the Caliciaceae is a powdery grayish or lemon-yellow crust on soil or rotten wood. There are possibly 30 or more genera separated by spore septation and color. Members of the family Physciaceae, with about 20 genera, are more typically crustose, with sessile apothecia and a more fully developed thallus. See also: Fungi; Lichens; Mutualism
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