AFRICAN

ORCHIDS

Rangaeris (Schltr.) Summerh., Bull. Misc. Inform. Kew 1936: 227 (1936).
Heterotypic Synonyms:
Barombiella Szlach., Ann. Bot. Fenn. 40: 69 (2003).
Description:
Epiphytic or lithophytic herbs; stem short or long, branched or unbranched, covered in persistent leaf bases. Roots arising at the stem base, or along the stem opposite the leaves, usually stout. Leaves distichous, usually conduplicate, linear to oblong, unequally 2-lobed at the apex, coriaceous. Inflorescences arched or pendent, few- to many-flowered. Flowers usually white, turning apricot-coloured as they age. Sepals and petals free, subsimilar, spreading or recurved. Lip entire or 3-lobed, ecallose; spur pendent, slender with a narrow mouth. Column short or long, glabrous or puberulent, without a foot; rostellum bifid; anther cucullate, truncate at apex; pollinia 2, pyriform; stipites 2, linear or oblanceolate; viscidium oblong or cordate, relatively large.
Distribution:
Trop. & S. Africa
Notes:
The genus Rangaeris was created by V. S. Summerhayes in 1936 to accommodate a small group of plants that were closely related to Aerangis but did not fit in with the genus in several ways. The main botanical differences are that Rangaeris has a bifid rostellum and a viscidium with two stipites instead of just one stipes as in Aerangis. The name is a near anagram of Aerangis.
The genus does not, however, seem to reflect a natural grouping: there are six members, as there were about 10 years ago, but they are not the same six species. In 1986, Rangaeris brachyceras, which Summerhayes had put in a separate section, was transferred to a new genus and became Cribbia brachyceras, while in 1989, Barombia schliebenii became Rangaeris schliebenii. Apart from the bifid rostellum, it is difficult to pick out just what distinguishes Rangaeris.
Most species have long, slender spurs; all but one have white flowers that turn apricot with age (a characteristic they share with Cyrtorchis and Jumellea, but not with Aerangis). Four of the six species have linear or strap-shaped leaves folded in the middle, but one has fleshy, bilaterally flattened leaves, and the other has flat, broadly oblong leaves. Five species have an entire or obscurely trilobed lip, while one has a distinctly trilobed lip. Still, whatever they are called, they are attractive plants and any that can be obtained are worth growing. Although two of the six species are not known to be in cultivation, they are mentioned here as they sound attractive and might yet become available.
Species:

Rangaeris amaniensis (Kraenzl.) Summerh. S. Ethiopia to Zimbabwe.
Rangaeris longicaudata (Rolfe) Summerh. Ivory Coast to Gabon
Rangaeris muscicola (Rchb.f.) Summerh. Trop. & S. Africa.
Rangaeris schliebenii (Mansf.) P.J.Cribb Tanzania.
Rangaeris trilobata Summerh. S. Nigeria to WC. Trop. Africa.

Bibliography and References:
Arends JC, Van der Laan FM. 1983 Cytotaxonomy of the monopodial orchids of the African and Malagasy regions. Genetica. 62. 81-94.
Arends JC, Van der Laan FM. 1986 Cytotaxonomy of the Vandeae. Lindleyana. 1. 33-41.
Carlsward BS, Stern WL, Bytebier B. 2006 Comparative vegetative anatomy and systematics of the angraecoids (Vandeae, Orchidaceae) with an emphasis on the leafless habit. Bot. J. Linn. Soc. 151. 165-218.
Gasson P, Cribb PJ. 1986 the leaf anatomy of Ossiculum aurantiacum Cribb & van der Laan (Orchidaceae: Vandoideae). Kew Bull. 41. 827-32.
La Croix I. 1994 The Angraecoid orchids: 5. Rangaeris, Listrostachys, Summerhayesia and Plectrelminthus. Orchid Rev. 102. (1197): 129-132 (1994)
Leroux A. 1983 Rangaeris rhipsalisocia (Reichb. f.) (Afrique Centrale). Orchidophile 14. (57): 396 (1983)
Pottinger M. 1982 African orchids. Plectrelminthus to Ypsilopus. Orchid Rev. 90. (1070): 384-385 (1982)
Senghas K. 1972 Rangaeris rhipsalisocia (Die angraekoiden Orchideen Afrikas und Madagaskars: 8 Rangaeris B). Orchidee 22. (2): 59-61 (1972)
Stewart J. 1978 Looking ahead - Rangaeris rhipsalisocia (Rchb. f.) Summerh. Orchid Rev. 86. (1016): 60 - 62 (1978)
World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; http://www.kew.org/wcsp/ accessed 17.03.2017