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Geosiris is a genus in the flowering plant family Iridaceae, first described in 1894. It was thought for many years to contain only one species, Geosiris aphylla, endemic to Madagascar. But then in 2010, a second species was described, Geosiris albiflora, from Mayotte Island in the Indian Ocean northwest of Madagascar.<ref>Kew World Checklist of Selected Plant Families</ref><ref>Goldblatt & J.C.Manning, Bothalia 40: 170 (2010).</ref> In 2017, a third species was found in Queensland, Australia, Geosiris australiensis.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Geosiris aphylla is sometimes called the "earth-iris." It is a small myco-heterotroph lacking chlorophyll and obtaining its nutrients from fungi in the soil. The genus name is derived from the Greek words geos, meaning "earth", and iris, referring to the Iris family of plants.<ref name=Goldblatt2008>Template:Cite book</ref>
Its rhizomes are slender and scaly, and stems are simple or branched. The leaves are alternate, but having no use, are reduced and scale-like. The flowers are light purple.
In 1939, F. P. Jonker<ref>F. P. Jonker, 1939, "Les Géosiridacées, une nouvelle famille de Madagascar" Recueil Trav. Bot. Néerl. 36:473-179</ref> assigned Geosiris to its own family Geosiridaceae in Orchidales, and this was adopted in the Cronquist system,<ref>Arthur Cronquist, An Integrated Systems of Classification of Flowering Plants (Columbia University Press, 1981) p.1236</ref> with a note that the family was closely related to Iridaceae or Burmanniaceae. The Angiosperm Phylogeny Group has since subsumed the family into Iridaceae; it is currently placed in the monotypic subfamily Geosiridoideae.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>