Tridactyle Schltr., Orchideen: 602 (1914).
The flowers of Tridactyle species are amongst the least showy of the African epiphytic orchids. Usually ochre brown, yellow, or green, rarely white, they are also small and mostly in few-flowered inflorescences. The sepals and petals are usually similar to each other, and the lip is the most conspicuous part of the flower. A few species have an entire lip with a pair of auricles on either side of the spur opening at the base, but typically the lip is 3-lobed as well as auriculate. Sometimes the lobes themselves, or just the lateral lobes, are further divided or fringed. The generic name is based on the overall lip structure—from the Greek words tri-, three, and daktylos, finger.
The plants of nearly all the species have long, woody stems covered in the remains of old leaf bases, often branched and growing in untidy clumps. A few are neat plants with upright stems, at least when young. Often they have distinctive roots, some thin, others quite thick, and either smooth or verrucose.
Some species are widespread throughout Africa, while others are very localized in their distribution. About 40 species are currently recognized and others will undoubtedly be described in due course. Yet other names may be reduced to synonymy as the full extent of variation within each species becomes known.
All these species grow easily in cultivation whether they are mounted on a piece of bark or placed upright in a basket or pot of free-draining compost. Mature plants are often hard to establish, and it is best to start with seedlings or young plants. Providing the best conditions for their healthy growth depends on trying to emulate the environment in their native habitats. Some knowledge of the altitude and climatic conditions where the plants occur is particularly helpful.
For convenience, and as an aid to identification, the species currently recognized are arranged here in 3 groups according to the length of the inflorescence and the number of flowers it bears.
Tridactyle Group 1.
Inflorescences very short, up to 1 cm long, bearing few flowers, lip entire or with short entire lateral lobes.
Tridactyle Group 2.
Inflorescences short to medium sized, 1—4 cm long, bearing 3—8 flowers, sometimes more.
Tridactyle Group 3.
Inflorescences long, usually over 4 cm long and up to 20 cm long, bearing 6 or more flowers.
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. Sarcanthinae - Acampe 1. Angraecinae - Angraecum 10, Aeranthes 1, Cryptopus 1. Aerangidinae - Aerangis 9, Ancistrorhynchus 5, Angraecopsis 2, Chamaeangis 3, Cyrtorchis 5, Diaphananthe 6, Microcoelia 2, Mystacidium 1, Plectrelminthus 1, Rangaeris 1, Tridactyle 2+ Also other reports from literature. Two groups in Algraecum. Orchidaceae.
Arends JC, Van der Laan FM. 1986 Cytotaxonomy of the Vandeae. Lindleyana. 1. 33-41. Aerangis, Ancistrorhynchus, Angraecopsis, Angraecum, Calyptrochilum, Cyrtorchis, Diaphananthe, Eurychone, Jumellea, Microcoelia, Ossiculum, Podangis, Rangaeris, Sphyrarhynchus, Summerhayesia, Tridactyle. Cytotaxonomy, Orchidaceae.
Bellone R. 1998 Les Diaphananthe et Tridactyle d'Afrique centrale. Orchidees Cult. Protect. no. 36. 13-21 (1998)
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. Leaf, root. LM of root & leaf, SEM of root. Phylogenies. Aerangis, Aeranthes, Angraecopsis, Beclardia, Bolusiella, Bonniera, Calyptrochilum, Campylocentrum, Chamaeangis, Cribbia, Cryptopus, Cyrtorchis, Dendrophylax, Diaphananthe, Eggelingia, Eurychone, Jumellea, Lemurella, Lemurorchis, Listrostachys, Microcoelia, Microterangis, Mystacidium, Neobathiea, Oeonia, Oeoniella, Ossiculum, Plectrelminthus, Podangis, Rangaeris, Rhipidoglossum, Sobennikoffia, Solenangis, Sphyrarhynchus, Summerhayesia, Tridactyle, Ypsilopus, Acampe, Amesiella, Chiloschista, Microtatorchis, Neofinetia, Phalaenopsis, Taeniophyllum, Trichoglottis, Vanda, Neobenthamia, Polystachya. 160 spp. studied. Growth form Morphology.
Cribb PJ. 1979 New or little known orchids from East Africa. Kew Bull. 34. (2): 321 - 340 (1979)
Dare M. 1999 A new Tridactyle (Orchidaceae) from the Flora Zambesiaca region. Excelsa no.19. 84-87 (1999)
Delepierre G. 2007 Note sur des Orchidaceae du Rwanda. Taxonomania no 20. 15. Fr Correction to earlier article.
Gasson P, Cribb PJ. 1986 the leaf anatomy of Ossiculum aurantiacum Cribb & van der Laan (Orchidaceae: Vandoideae). Kew Bull. 41. 827-32.
Geerinck D. 1990 Notes taxonomiques sur des Orchidacees d'Afrique centrale: 10. Bull. Jard. Bot. Nation. Belg. 60. (1-2): 181-190 (1990)
Hennessy EF. 1994 Plate 2098. Tridactyle gentilii; Ghana, Nigeria, Cameroun, Zaire, Zambia, Uganda, South Africa; Orchidaceae. Flow. Pl. Afr. 53. 90-93 (1994)
La Croix I. 1998 Plant portraits: 354. Tridactyle truncatiloba. Orchidaceae. Curtis's Bot. Mag. 15. (4): 249-254 (1998)
Linder HP. 1989 Notes on southern African angraecoid orchids. Kew Bull. 44. (2): 317-319 (1989)
Olatunji OA, Nengim RO. 1980 Occurrernce and distribution of tracheoidal elements in the Orchidaceae. Bot. J. Linn. Soc. 80. 357-70. Aerangis, Ancistrorhynchus, Angraecum, Ansellia, Bulbophyllum, Calyptrochilum, Chamaeangis, Cystorchis, Diaphananthe, Elophia, Eurychone, Genyorchis, Graphorchis, Habenaria, Hetaeria, Liparis, Listrostachys, Oeceoclades, Plectrelminthus, Podangis, Polystachya, Rangaeris, Solenangis, Tridactyle. Root stem, pseudobulb, leaf. 88 spp. examined; 43 spp. contained tracheoids (all epiphytic supp.). Tracheoids with annular, spiral, reticulate or pitted thickenings. Orchidaceae
Pottinger M. 1982 African orchids. Plectrelminthus to Ypsilopus. Orchid Rev. 90. (1070): 384-385 (1982)
Sanford WW, Adanlawo I. 1973 Velamen and exodermis characters of West African epiphytic orchids in relation to taxonomic grouping and habitat tolerance. Bot.J.Linn. Soc. 66. 307-21. Polystachya, Liparis, Ancistrochilus, Bulbophyllum, Genyorchis, Ansellia, Graphorkis, Podangis, Calyptrochilum, Angraecum, Microcoelia, Encheiridion, Chauliodon, Diaphananthe, Chameangis, Aerangis, Rangaeris, Cyrtorchis, Tridactyle. Roots, Tissues_exod, Orchidaceae
Stévart, T. & Cribb, P.J. (2004). Five new taxa of Tridactyle (Orchidaceae) from West Central Africa. Kew Bulletin 59 (2): 195-205.
Szlachetko DL. 1994 Orchidaceae Lisowskianae: 3. Disa and Tridactyle. Fragm. Flor. Geobot. 39. (2): 543-548 (1994)
Teuscher H. 1977 Collector's item : Angraecopsis, Bolusiella and Tridactyle. Amer. Orchid Soc. Bull. 46. (12): 1109 - 1114 (1977)
Williamson G. 1982 Notes on orchids from South Central Africa. J. S. Afr. Bot. 48. (1): 11-20 (1982)
Wright I. 1985 Tridactyle bicaudata: emblem of the Eastern Province Orchid Society. S. Afr. Orchid J., 16. (1): 6-7 (1985)