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Chorioactis
''Chorioactis'' is a genus of fungus that contains the single species ''Chorioactis geaster''.〔Although ''geaster'' means "earth star", this fungus is not related to the species ''Geaster'' or any of the Geastraceae.〕 The mushroom is commonly known as the devil's cigar or the Texas star in the United States, while in Japan it is called .
This extremely rare mushroom is notable for its unusual appearance and disjunct distribution: it is found only in select locales in Texas and Japan. The fruit body, which grows on the stumps or dead roots of cedar elms (in Texas) or dead oaks (in Japan), somewhat resembles a dark brown or black cigar before it splits open radially into a starlike arrangement of four to seven leathery rays. The interior surface of the fruit body bears the spore-bearing tissue known as the hymenium, and is colored white to brown, depending on its age. The fruit body opening can be accompanied by a distinct hissing sound and the release of a smoky cloud of spores.
Fruit bodies were first collected in Austin, Texas, and the species was named ''Urnula geaster'' in 1893; later it was found in Kyushu in 1937, but the mushroom was not reported again in Japan until 1973. Although the new genus ''Chorioactis'' was proposed to accommodate the unique species a few years after its original discovery, it was not until 1968 that it was accepted as a valid genus. Its classification has also been a source of confusion. Historically, ''Chorioactis'' was placed in the fungus family Sarcosomataceae, despite inconsistencies in the microscopic structure of the ascus, the saclike structure in which spores are formed. Phylogenetic analyses of the past decade have clarified the fungus's classification: ''Chorioactis'', along with three other genera, make up the family Chorioactidaceae, a grouping of related fungi formally acknowledged in 2008. In 2009, Japanese researchers reported discovering a form of the fungus missing the sexual stage of its life cycle; this asexual state was named ''Kumanasamuha geaster''.
==History==
The fungus was first collected in Austin, Texas, in 1893 by botanist Lucien Marcus Underwood, who sent the specimens to mycologist Charles Horton Peck for identification. Peck described the species as ''Urnula geaster'' in that year's ''Annual Report of the New York State botanist'', although he expressed doubt about its generic placement in ''Urnula''.〔 In 1902, student mycologist Elsie Kupfer questioned the proposed classification of various species in the genera ''Urnula'' and ''Geopyxis'', as suggested in an 1896 publication on the Discomycetes by German mycologist Heinrich Rehm. She considered Rehm's transfer of the species to the genus ''Geopyxis'' illogical: "Even externally the fungus does not closely answer Rehm's own description of the genus ''Geopyxis'' under which he places it; the texture of the apothecium is described as fleshy, the stem, as short and sometimes thin; while in this plant, the leathery character of the cup and the length and thickness of the stem are its noticeable features." Working with Underwood's guidance, Kupfer compared the microscopic structure of the hymenium (the fertile, spore-bearing tissue) of the Texan species with a number of similar ones—''Geopyxis carbonaria'', ''Urnula craterium'', and ''Urnula terrestris'' (now known as ''Podophacidium xanthomelum''). She concluded that the Texan species was so dissimilar as to warrant its own genus, which she named ''Chorioactis''.〔 Although this taxonomical change was opposed in later studies of the fungus by Frederick De Forest Heald and Frederick Adolf Wolf (1910)〔 and Fred Jay Seaver (1928, 1942),〔〔 ''Chorioactis'' was established as a valid genus in 1968 by Finn-Egil Eckblad in his comprehensive monograph about the Discomycetes.〔〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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