Orchids of New Guinea

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Dendrobium mulderi

Dendrobium mulderi Schuit. & de Vogel, Malesian Orchid J. 4 (2009) 106, fig. 6-8

Type: Hoogland 9635 (holo CANB; iso BM, BRI, CANB [spirit], K, L, LAE; AMES, BO, NY, US)

Rhizome very short. Pseudobulbs crowded, terete, 1.5–7.5 by 0.15–0.25 cm, 1-leaved. Leaf linear-oblong to linear, 0.15–0.35 by 0.25–0.7 cm; base cuneate to subpetiolate; apex obtuse, minutely bilobulate, mucronate, mucro longer than the lobules. Inflorescences adaxial and abaxial, solitary. Main basal bract tubular, 0.2–0.4 cm long. Peduncle 0.2–0.5 cm long. Median sepal ovate-elliptic, 0.46–0.52 by 0.19–0.26 cm; apex obtuse to subacute, reflexed; 3-nerved. Lateral sepals broadly obliquely ovate-elliptic, 0.53–0.59 by 0.25–0.37 cm; apex obtuse to subacute, patent; 3-nerved. Mentum very short for the section, open in front, 0.1 cm long; apex obtuse. Petals reflexed, linear, 0.35–0.38 by 0.04–0.06 cm; base slightly and gradually narrowing from the base; margins entire; apex obtuse to acute; 1-nerved,. Lip 3-lobed, spathulate, 0.36–0.44 cm long, glabrous, but callus often papillose; hypochile 0.16–0.26 cm long, inserted at the apex of the column foot, 0.31–0.38 cm wide across the flattened lateral lobes, bilobulate, the lateral lobes sometimes connected by a flat horizontal lamella (not in the type), longitudinally folded between the lobules, the basal lobule short, erose to dentiform, more or less acute, the apical lobule oblong, 0.08–0.13 by 0.04–0.06 cm, entire, with subacute to acute apex; epichile fleshy, broadly obcordate, 0.18 by 0.25–0.38 cm, margins entire (as in the type) or erose at the apex; apex with a large acute mucro in the sinus as long as the depth of the sinus (but see note below); callus at base of epichile orbicular to transversely rectangular in outline, glabrous or more frequently papillose (as in the type). Column 0.18–0.22 cm long; in front below the stigma glabrous or pubescent (as in the type); wings short bidentate, glabrous or papillose; clinandrium entire, margin in the middle with a low tooth; column-foot c. 0.1 cm long. Anther cucullate, 0.07 by 0.05–0.08 cm; base emarginate; apex truncate, papillose; pollinia 0.06 cm long. Ovary and pedicel 1.1 cm long, 3-winged, glabrous. Fruit elliptic in outline, 3-angular in cross-section, c. 1 by 0.5 cm; 3-winged; pedicel of the fruit curved like an inverted U, causing the fruit to point downwards.
(after Schuiteman & de Vogel, 2009)

Colours:

Flower white (almost all records); a living specimen, Schuiteman, Mulder & Vogel 8, flowers white with epichile callus grass-green, yellowish green in older flowers; anther green with brownish margins.

Habitat:

Montane forest and tree-fern grasslands. Epiphyte on tree trunks and tree-ferns (type), also on mossy rocks and steep road banks. Altitude 1830–2800m.

Distribution:

Malesia (New Guinea)

Distribution New Guinea:

Papua New Guinea: Southern Highlands, Western Highlands, Chimbu, Eastern Highlands, Morobe and East New Britain Provinces; see map

Cultivation:

Cool growing epiphyte.

Flowering time in the wild:

All year round.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Genus Dendrobium
Section Cadetia
Subsection Sarcocadetia
Species Subsection Sarcocadetia

Notes:

Dendrobium mulderi is probably closely related to D. quinquelobum (Schltr.) J.J.Sm., which also has bilobulate lateral lobes. In that species the apical lobules of the lateral lobes are not diverging but porrect and parallel when flattened, extending to more than halfway the epichile; the mentum is tubular at the apex, and the mentum and the column-foot are much longer.

A collection from New Britain deviates by its very short obtuse apical mucro.

Dendrobium mulderi is variable in the presence or absence of papillae on the callus, presence or absence of a transverse lamella connecting the lateral lobes, and presence or absence of pubescence on the column. These features appear to be uncorrelated.