Genus Tridactyle

Tridactyle minutifolia Stévart & Haijere, Phytotaxa 212: 143 (2015).
Description:
Epiphytic herb with unbranched erect stem, 20–40 cm long and 2 mm in diameter, internodes 2–4 mm long, brownish to black spots. Roots up to 0.5 mm in diameter, glabrous. Leaves distichous; blade linear, 5–7 × 0.2–0.4 cm, glabrous, dull, green; apex unequally bilobate. Inflorescences up to 8 per shoot, opposite to the leaf, semi-pendulous, 3.5–5.5 cm long, 7–10 flowered. Floral bracts broadly triangular, apex acute, 1.5–2 × 1–1.5 mm. Flowers arranged in two rows, 2–4 mm spaced out, white-yellowish to orange. Pedicel and ovary 3–4 × 1 mm, papillose. Sepals ovate, acute to acuminate, 3–5 × 1–2 mm, adaxially 3-veined, the tips recurved, margins entire, glabrous. Petals linear, acute, 3–5 × 1 mm, margins entire or slightly dentate, glabrous. Labellum auriculate at the base, auricules ronded, 0.5–1 mm diameter; labellum trilobate to about half way, 5 × 1.3 mm, glabrous; mid-lobe 2.5–4 mm long, triangular; side lobes longer, spreading, almost threadlike. Spur mostly absent, or if present, 7–8 mm long, cylindrical, straight, apex acute. Flower scent not observed.
Habitat:
Epiphytic herb found in high canopy and dense rainforest with many Burseraceae, sometimes exploited. It was found as an epiphyte on Bikinia letestui (Pellegrin 1942: 120) Wieringa in Wieringa & van der Maesen (1999: 222) between 25 and 40 m in the canopy. The altitude range of the species was estimated to be between 350 and 490 m (for specimens with spur) and around 570 m (for specimens without spur).
Phenology:
Flowering in February, May and between October and December.
Cultivation:
As given for the genus.
Notes:
The length of the rachis and the shape of the side lobes of the labellum place the species in the section D of Tridactyle, according to Summerhayes (1948), which include species with long inflorescences (more than 4 cm) and entire side lobes of the labellum. It is also very close to Tridactyle stevartiana, a species occurring in Rwanda, based on the shape and length of the leaves but differs from it in the inflorescences and the margins of the side lobes. Indeed, Tridactyle stevartiana has inflorescences of 1 cm or less, while Tridactyle minutifolia has inflorescences of 3 to 6 cm, and the margins of the side lobes of Tridactyle stevartiana are denticulate while the one of Tridactyle minutifolia are entire. According to unpublished molecular data produced by the second author, using plastid matK, trnL-trnF and ITS, Tridactyle minutifolia is close to Tridactyle tridactylites, but it is well separated. In specimens Stévart 3054, Biteau 155 and GB 416 from Monts de Cristal and adjacent area, spur is lacking, but specimens from Monts Doudou (collected from the living plant Arends 634) have a long spur.
Distribution:
Endemic to Gabon and Equatorial Guinea. The distribution range of Tridactyle minutifolia is comprised in the Atlantic Sector of the Lower Guinea Domain (Senterre 2005), which is the coastal part of the Lower Guinea Domain of the Guineo-Congolian Region (White 1979).
References:
A new species of Tridactyle (Vandeae, Epidendroideae, Orchidaceae) from Gabon and Equatorial Guinea Phytotaxa 212 (2): 141–148.2015: 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 21.03.2017
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