Prosthechea

Prosthechea is a genus of flowering plants in the orchid family (Orchidaceae). The name is derived from the Greek word prostheke (appendix), referring to the appendage on the back of the column. Appendage orchid is a common name for this genus. Prosthechea is abbreviated Psh. in the horticultural trade.

Morphology
The roots of all Prosthechea species possess a velamen (a thick sponge-like covering) differentiated into epivelamen and endovelamen. Flavonoid crystals were observed in both the roots and leaves. The erect stems form flattened or thickened pseudobulbs. There are 1 to 3 terminal, sessile leaves. The leathery blade is ovate to lanceolate. (Euchile leaves are softer and thinner than other Prosthechea leaves.)

The flowers form an apical, paniculate raceme with a spathe at the base of the inflorescence. There is a great variety in the flowers of this genus. They may be attached to the stem by a peduncle or they may be sessile. They can flower on the raceme at the same time or successively. They can be resupinate or non-resupinate (as in Prosthechea cochleata). Prosthechea flowers are unique among the Laeliinae in producing fluorescent flavenoid crystals when preserved in ethanol with 5% sodium hydroxide.

The sepals are almost equal in length, while the petals can be much slender. The lip is pressed closely (adnate to proximal) to half of the column and shows a callus (a stiff protuberance). The column is 3- to 5-toothed at its top.

There are four, almost equal pollinia with an inverted egg shape. There are four stalks (or caudicles) in two pairs. The beak is entire, curved into a half circle and covered with viscous glycoside crystals.

The fruits consist of ellipse-shaped to egg-shaped, 1-locular, 3-winged capsules.

Taxonomy
The genus Prosthechea has only recently (1997; published in 1998) been reestablished by W. E. Higgins as a distinct genus (see references). Two species were later transferred to Euchile (E. citrina and E. mariae) by Withner in 1998. The status of Euchile species as sister to Prosthechea excluding Euchile was confirmed by Higgins in his doctoral dissertation in 2000. Previously, the species had been included in different genera : Anacheilium, Encyclia, Epidendrum, Euchile, Hormidium and Pollardia. The status as genus was confirmed by recent data, based on molecular evidence (nuclear (nrITS) and plastid (matK and trnL-F) DNA sequence data) (W. E. Higgins et al. 2003).

Distribution
This is a neotropical epiphytic genus, widespread across much of Latin America from Mexico to Paraguay, as well as in Florida and the West Indies.

Species
, Plants of the World Online accepts the following species:

Natural Hybrids

 * Prosthechea × chixoyensis E.Mó & Cetzal
 * Prosthechea × intermedia (Campacci) J.M.H.Shaw