Orchids of New Guinea

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Dendrobium centrosepalum

Dendrobium centrosepalum Schuit., Juswara & Droissart, PhytoKeys 61 (2016) 52, fig. 2 B, 3 e-h.

Type: Droissart & Juswara 1736 (holo BO, spirit material).

Epiphytic herb. Rhizome creeping, c. 3 cm long, growing downwards; roots 0.05 cm diam. Pseudobulbs close together, erect, oblongoid-fusiform, 1.3–1.5 by 0.4 cm; main internodes 3; irregularly 5-ribbed; 1-leaved at apex, sometimes with a reduced additional leaf. Leaves deciduous, erect, narrowly elliptic, 3.3 by 1.1 cm; sheath very short; margin smooth, slightly erose at apex; apex obtuse, minutely 3-dentate. Inflorescence arising laterally from the upper internode of the leafless pseudobulb, erect, c. 1.2 cm long, c. 7-flowered; peduncle 0.52 cm long, the basal part covered by a few short scales; rachis straight, 0.7 cm long. Floral bracts triangular, patent, 0.48 by 0.28 cm, glabrous; apex acuminate; 3-nerved. Pedicel and ovary narrowly clavate, curved, c. 0.84 cm long, with 5 rounded ribs, minutely papillose. Flower 1.05 cm long. Sepals glabrous, but abaxially finely papillose on the slightly raised midnerve; apex distinctly sharply apiculate. Median sepal ovate-oblong, 0.35 by 0.19 cm; 3-nerved; mucro 0.04 cm long. Lateral sepals obliquely narrowly ovate-oblong, much elongated in basal part, in total 1.08 by 0.28 cm; 4-nerved; mucro 0.09 cm long; mentum narrowly conical-cylindrical, 0.57 cm long, with rounded apex, the closed apical part 0.48 cm long. Petals elliptic, 0.29 by 0.17 cm; apex emarginate, very shortly mucronate; 3-nerved. Lip when flattened subspathulate, 0.85 by 0.23 cm, at 0.5 cm above the base with a V-shaped transverse ridge; margins of the basal part adnate to the column-foot for 0.21 cm; apical part broadly elliptic, finely papillose along apical margin, with rounded, minutely apiculate apex. Column rectangular, 0.19 cm long; wings truncate; foot 0.57 cm long; stigma semi-orbicular, 0.08 cm wide; rostellum swollen, transversely oblongoid; anther cucullate-rectangular, 0.09 by 0.1 cm, minutely papillose, at the base retuse, with truncate and minutely erose apex; pollinia 0.07 cm long.
(after Schuiteman, Juswara & Droissart 2016)

Colours:

Pseudobulbs green tinged purplish. Leaves glaucous green. Sepals bright purple with greenish mucro. Petals, lip and ovary bright purple.

Habitat:

Epiphyte on a thick, vertical, moss-and-lichen-covered trunk of a tree in submontane forest.Altitude 1114 m. elevation

Distribution:

Malesia (Indonesia, New Guinea), endemic

Distribution New Guinea:

Indonesia (West Papua Province, Kaimana Regency), see map

Cultivation:

Intermediate growing epiphyte.

Flowering time in the wild:

October.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Genus Dendrobium
Section Calyptrochilus
Species Dendrobium centrosepalum

Notes:

Dendrobium centrosepalum is similar to D. dichaeoides Schltr. and D. limpidum Schuit. & de Vogel in the small, bright purple flowers in short and dense inflorescences, but differs in the oblongoid-fusiform short pseudobulbs (versus elongate, leafy stems) and the sharply apiculate sepals (versus not sharply apiculate).

D. centrosepalum is vegetatively similar to D. aurantiroseum P.Royen ex T.M.Reeve from New Guinea in the unifoliate pseudobulbs on a creeping rhizome, but is from much lower elevations (1114 m versus 2100–3350 m) and has purple flowers (versus pink flowers) that are about twice as small and has apiculate sepals (versus not apiculate), and the cross-ridge on the lip is situated above the middle (versus below the middle).