Oncidium

Oncidium sphacelatum

The genus Oncidium from the orchid family (Orchidaceae) contains numerous, native to the Neotropical species. Depending on the concept about 260 to 800 species can be distinguished. The plants usually grow as epiphytes, that is, as Aufsitzer on other plants, usually trees.

Description

The Oncidium species grow sympodial: on a rhizome are rung each with limited growth. The shoot axis is thickened into pseudobulbs. These are green, oval and often laterally compressed. Below the pseudobulbs are low leaves, the uppermost leaves are formed leaf-like. At the top of the pseudobulbs are one to two, rarely three leaves. They are lanceolate to linear shaped and folded in the bud along the midrib. Young plants do not have pseudobulbs and leaves unifaziale, only later did the thickened stem axis and bifacial leaves developed. The flower stem is usually branched and many flowered and can be very long. It rises laterally below the pseudobulb. The resupinierten flowers are usually yellow or brown. The petals are not fused together. The lip is three-lobed and is approximately perpendicular to the column. There is a distinct callus at the base of the lip. The column itself is short, at the top there are two lateral appendages. The stamen contains two ridged pollinia.

Dissemination

Distribution of the genus Oncidium are the American tropics from Mexico to the West Indies to Bolivia and Paraguay. The greatest species diversity is found in upland forests.

Systematics and botanical history

Oncidium was described in 1800 by Olof Peter Swartz first time. Type species of Oncidium variegatum was. The name Oncidium refers to a bead-shaped elevation of the lip base ( Greek onkos = bead, callus ).

In the following years many species have been described under the name of Oncidium, of sometimes quite different appearance. In particular, the type species and a small group of close relatives proved to be not typical of the rest of the genus. According to the rules of nomenclature, the name Oncidium should have stayed in the type species, which would have meant the renaming of hundreds of plant names. To avoid this, a new type species had to be set ( Oncidium altissimum ), the original type species was renamed Tolumnia.

Other former Oncidium species are found in the genera Caucaea, Rossioglossum, Cyrtochilum, Cyrtochiloides, Otoglossum, Psychopsis, Trichocentrum and Zelenkoa. There still remain hundreds of species in the genus Oncidium, which has long been not monophyletic by these spin-offs. Other changes in the genre boundaries are to be expected. Meanwhile, the genus Odontoglossum was revised and integrated into the genus Oncidium.

Culture

Some species are cultivated because of their flowers. There are numerous hybrids have been achieved also with closely related genera. Most species require a cool to temperate, bright stand high humidity, good supply of fresh air and a rest period must be observed.

Documents

The information in this article come mainly from:

  • Mark W. Chase: Oncidium. In: Flora of North America Editorial Committee ( eds.): Flora of North America North of Mexico. 26, Oxford University Press, New York and Oxford 1993 , p 648 ( eFloras.org, accessed on 19.10.2008 ).
  • Manfred Wolff, Olaf Greeting: Orchids Atlas. Ulmer, Stuttgart 2007, ISBN 978-3800138708, pp. 258-259.

Furthermore, quoting:

Postgraduate

  • Willibald Koniger: Oncidium. A monograph. 5 vols, 2004
  • Orchids
  • Orchidaceae
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