Xerorchis

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Xerorchis
Systematics
Monocots
Order : Asparagales (Asparagales)
Family : Orchids (orchidaceae)
Subfamily : Epidendroideae
Tribe : Xerorchideae
Genre : Xerorchis
Scientific name
Xerorchis
Schltr.

Xerorchis is a genus from the family of the orchid (Orchidaceae). Itcolonizes tropical South Americawith two species .

description

The terrestrially growing plants reach heights of 45 to 55 cm. The rhizome is very short, ascending and wiry. The roots are elongated, thin, flexible and hairy, they have no velamen radicum . The shoot is slender, angular, stiff, simple or branched, initially covered with a few lower leaves , which gradually turn indistinguishably into deciduous leaves. The leaves are arranged in two rows, the stem axis is zigzag-shaped in the upper, leafy area. The leaves are linear, lanceolate or narrow-oval with a pointed tip. In the upward direction, the sheets are smaller in the terminal inflorescence are bracts equal foliage leaves.

The inflorescence contains a few or many flowers , these are rather small, light green, yellow-green or cream-colored, they do not open wide. The ovary is slightly club-shaped with a slender flower stalk. The petals are not fused together. The sepals are lanceolate or tongue-shaped, they end pointed, they are hairless on the inside, a little hairy on the outside. The lateral sepals are slightly crooked. The petals resemble the sepals. The lip has a wedge-shaped base, in the middle there are several indistinct ridges, the front lip has entire margins or slightly three-lobed, often with a wavy edge. The column is slender, semicircular in cross section, hairy on the underside, with two appendages below the scar . The scar is bean-shaped. The stamen is bean-shaped to hood-shaped, blunt at the front and a button-like elevation at the top. It contains eight pollinia in two chambers, these are inverted egg-shaped to pear-shaped, laterally compressed, four each connected. The pollinia hang on a round adhesive disc (Viscidium). The separating tissue between the stamen and the stigma (rostellum) is short and wide, it ends with two teeth.

distribution

Distribution of the genus Xerorchis

The two species of the genus Xerorchis are common in tropical South America. They occur from sea level to 700 meters above sea level. They grow in the shade of moist forests and take root in the humus layer.

Systematics and botanical history

The genus Xerorchis was established by Rudolf Schlechter in 1912. The name is made up of the Greek words ξηρός xeros , "dry", and ὄρχις orchis , "testicles" (here: "orchid"). Only the species Xerorchis amazonica was worse known, he writes to explain the genus name: "The whole plant gives the impression of a xerophyte ". The second species, Xerorchis trichorhiza , was described by Friedrich Wilhelm Ludwig Kraenzlin as an epidendrum in 1928 and placed in the genus Xerorchis by Leslie A. Garay in 1956 .

Schlechter suspected a relationship between the genus Xerorchis and Elleanthus . In 1981 Robert Dressler also classified them in this relationship, but later stated that a reliable assignment of Xerorchis was not possible. In 1995 Dariusz Szlachetko set up his own subtribe Xerorchidinae, which only contained the genus Xerorchis ; he arranged them in a tribe Elleantheae, so again in the family of Elleanthus . Mark W. Chase published a classification of orchids in 2003, in which Xerorchis is in the tribe Nervilieae . Phillip Cribb established his own tribe, Xerorchideae, with the only genus Xerorchis in 2005 to emphasize the isolated position of the genus. A molecular genetic investigation showed that Xerorchis could actually be related to the Nervilieae; Diceratostele and Didymoplexis were identified as the closest related genera .

The types are:

See also

literature

  • Leslie A. Garay: 225 (1). Orchidaceae (Cypripedioideae, Orchidoideae and Neottioideae) . In: Gunnar Harling, Benkt Sparre (ed.): Flora of Ecuador . tape 9 , 1978, ISSN  0347-8742 .
  • Alec M. Pridgeon, Phillip Cribb, Mark W. Chase (Eds.): Genera Orchidacearum. Epidendroideae (Part one) . tape 4 . Oxford University Press, New York and Oxford 2005, ISBN 0-19-850712-7 .

Individual evidence

  1. ↑ a b Leslie Garay: Xerorchis . In: Orchidaceae (Cypripedioideae, Orchidoideae and Neottioideae) . Pp. 138-141.
  2. ↑ a b c d Philipp Cribb: Xerorchis . In: Genera Orchidacearum . Vol. 4, pp. 624-626.
  3. ^ Rudolf Schlechter: Orchidaceae novae et criticae. Decas XXXV . In: Repertorium Specierum Novarum Regni Vegetabilis . tape 11 , 1912, pp. 44-45 ( botanicus.org ).
  4. ↑ a b c d Rafaël Govaerts (ed.): Xerorchis. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved July 22, 2018.
  5. ↑ Erik Paul Rothacker: The primitive Epidendroideae (Orchidaceae): phylogeny, character evolution and the systematics of Triphora (Triphoreae). (pdf) Ohio State University, 2007, accessed December 19, 2009 .

Web links

Commons : Xerorchis  - album with pictures, videos and audio files