AFRICAN

ORCHIDS

Genus Peristylus Blume, Bijdr. Fl. Ned. Ind.: 404 (1825), nom. cons.
Heterotypic Synonyms:
Glossula Lindl., Bot. Reg. 10: t. 862 (1824).
Glossaspis Spreng., Syst. Veg. 3: 694 (1826).
Coeloglossum Lindl., Edwards's Bot. Reg. 20: t. 1701 (1834), nom. illeg.
Digomphotis Raf., Fl. Tellur. 2: 37 (1837).
Choeradoplectron Schauer, Nov. Actorum Acad. Caes. Leop.-Carol. Nat. Cur. 19(Suppl. 1): 436 (1843).
Lindblomia Fr., Bot. Not. 1843: 134 (1843).
Type species:
Peristylus grandis
Description:
Small to medium-sized terrestrial plants with small oblong to ellipsoid tubers. Leaves several, in a basal rosette, clustered in the middle of the stem or spirally arranged along stem, ovate to lanceolate or oblanceolate, sheathing at the base, thin-textured. Inflorescence terminal, sparsely to densely flowered; bracts lanceolate, as long as or shorter than the flowers. Flowers resupinate, small, spirally arranged, green or yellowish green, perianth persistent in fruit. Dorsal sepal and petals entire, free, connivent or slightly spreading, lateral sepals oblique. Labellum connate at base with margins of column, distally three -lobed or entire, larger than the sepals and petals, often clawed at the base, spurred at the base, ecallose or with a fleshy callus in front of the mouth of the spur; spur scrotiform to cylindric, shorter than to longer than the labellum, usually shorter than the ovary. Column short, conical, erect; anther bilocular, with adjacent loculi; lateral appendages sessile; pollinia two, shortly clavate, sectile; viscidia two, ovate to oblong; rostellum small, trilobed but with lateral lobe short and mid-lobe smaller than anther loculi; stigmatic arms two, remote, sessile, convex or depressed centrally, adnate to base of lip and lateral appendages. Ovary almost lacking a pedicel.
Etymology:
The genus Peristylus was first formally described in 1825 by Carl Ludwig Blume and the description was published in Bijdragen tot de flora van Nederlandsch Indië. The genus Peristylus is derived from the Greek words peri meaning 'around', and stylos 'column', referring to the arms on each side of the column.
Habitat:
Some Peristylis species grow in habitats with full sunlight. Other Peristylus species grow under the shade of trees in montane temperate forest, subtropical montane forest, or tropical wet evergreen forests and in a moist substrate especially on the banks of streams. The flowering period of Peristylus varies according to species, with some flowering between September and February and others from April to August.
Notes:
The distinction of Peristylus from Habenaria has been debated at some length (e.g. Seidenfaden 1977; Kores 1989). Vegetatively they are indistinguishable, but current views support the retention of the former as a distinct genus on the basis of column structure. In particular the stigma lobe of Habenaria are stalked (termed stigmatophores) and free from the lip base. In Peristylis they are reduced to pulvinate swellings at the base of the column, which is adnate to the base of the lip. Most Habenaria species have larger flowers, but the range of flower size overlaps that of Peristylis.
Distribution:
Mascarenes,Réunion, Trop. & Subtrop. Asia to Mongolia and Pacific
Species:

Peristylus citrinus (Thouars) Lindl. Mascarenes. 
Peristylus commersonianus Lindl.  Réunion. 


World Checklist of Monocotyledons. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; http://www.kew.org/wcsp/monocots/ accessed 21/09/2019
References:
Pridgeon, A.M., Cribb, P.J., Chase, M.C. & Rasmussen, F.N. (2001). Orchidoideae (Part 1). Genera Orchidacearum 2: 1-416. Oxford University Press, New York, Oxford.