Distylodon sonkeanus Droissart, Stévart & P.J.Cribb, PhytoKeys 36: 28 (2014).
Dwarf epiphytic herb. Stem short, up to 8 mm long, 2–2.5 mm in diameter, leafy, unbranched. Roots more than 120 mm long, 1–1.8 mm in diameter, numerous, distributed at the base of the plant, unbranched. Leaves few (up to 5), 25–37 × 6–11 mm, obliquely narrowly elliptic, slightly coriaceous, with entire margins, with an indistinct and irregular reticulate venation; leaf apex obliquely subacute, unequally bilobed, with distance between the two lobes less than 1 mm. Inflorescences up to 41 mm long, 2- to 5-flowered, almost horizontal to pendant, unbranched, emerging at the base of the stem, with peduncle 13 mm long; floral internode about 6–7 mm, one flower per node; rachis terete. Bracts up to 1.2 mm long, tubular. Flowers 17–25 × 6–8 mm, not opening widely, green, the larger one situated at the apex of the inflorescence. Ovary and pedicel not twisted, 5–7 mm long. Dorsal sepal 4–7 × 1.6–1.9 mm, linear lanceolate, acute, slightly to markedly reflexed, with entire margins. Lateral sepals 5.5–9 × 1.8–2.0 mm, obliquely linear-lanceolate, acute, slightly to markedly reflexed, with entire margins. Petals 3.0–4.8 × 1.1–1.3 mm, linear lanceolate, acuminate, slightly curved forward, with entire margins. Lip 4.5–6.0 × 2.0–3.5 mm, slightly to markedly trilobed in the basal half; side lobe obliquely triangular, subacute to acute, 0.8–1.8 mm long; mid lobe much longer, 3–4 mm long, linear-subulate, acuminate, fleshy, somewhat curved forward; spur 13.5–18.0 mm long, 0.8–1.1 mm in diameter, cylindrical, straight, slightly inflated in the apical part in larger flowers, apex rounded. Column 1–1.2 × 1.0 mm, almost cylindrical with truncate apex. Rostellum 0.3 mm long, consists of two erect, subulate teeth or fangs. Anthercap 1.0 × 1.0 mm, deltoid. Pollinia two, spherical. Viscidia two, with two stipites 0.7–0.8 mm long, independent of each other, flattened, bifurcate.
The species epithet ‘sonkeanum’ refers to the Professor Bonaventure Sonké of the University of Yaoundé I, who is an internationally recognized taxonomist, specialized in the Rubiaceae’s family. He has collected extensively in the Bipindi-Akom II area, and adjacent Ngovayang massif and Campo-Ma’an National Park. He was one of the first to highlight the high biodiversity of this area and he greatly facilitated our work in Cameroon.
Distylodon sonkeanum is endemic to the coastal part of the Lower Guinea Domain (White 1979) of the Guineo-Congolian Region. It is known from a single locality in South Region of Cameroon. The only population known so far was found in the lowland evergreen forest at 100 m elevation, growing epiphytically on a fallen branch.
As given for the genus.
WCSP (2017). 'World Checklist of Selected Plant Families. 15.03.2017; http://apps.kew.org/wcsp/
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