Orchids of New Guinea

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Dendrobium hydrophilum

Dendrobium hydrophilum J.J.Sm., Bull. Dép. Agric. Indes Néerl. 19 (1908) 17; Nova Guinea 8, 1 (1909) 56, t. 21, fig. 65.

Type: Bogor cult. (Exp. Lorentz, Djibdja 21) s.n. (Noord River) (holo BO).

Synonyms:

Diplocaulobium hydrophilum (J.J.Sm.) Kraenzl., in Engl.

Pseudobulbs crowded, 1-leaved, at the base oblong-ovoid, in upper part very slender and angular, 14-20.5 cm long, of which the swollen basal part c. 1.4 by 0.6-0.7 cm, 0.13-0.15 cm wide in upper part. Leaves erect, linear, 11-12.5 by 0.5 cm, apex bilobed, coriaceous, concave, on either side of the midvein convex, below weakly keeled. Inflorescences arising in succession from the apex of the pseudobulb, 1-flowered, spathe narrow, laterally flattened, 1.6-1.8 cm long, acute; peduncle 0.5 cm long. Floral bract minute. Pedicel 1.2 cm long; ovary 0.25 cm long, 6-grooved. Flower resupinated, c. 3 cm across. Dorsal sepal at the base oblong-triangular, narrowing to the linear upper part, 1.55 cm (1.45-2.6, Smith 1916) by 3 mm, concave, apex acute. Lateral sepals at the base strongly obliquely falcate-triangular, narrowing to the linear upper part, 1.5 cm by 5.5 mm, concave, apex narrowly obtuse; mentum c. 0.5 cm long. Petals subfalcate, linear-filiform, a little widened to the base, 1.5 cm by 1 mm, apex acute. Lip 3-lobed above the middle, 0.9 by 0.6 cm, with 2 straight parallel basal keels extending to the middle of the midlobe, the keels in basal half glabrous, in upper part slightly pubescent; lateral lobes erect, large, free part c. 0.2 cm long, falcate-triangular, apex obtuse; midlobe broadly rhombic, 0.45 by 0.5 cm, undulate, along basal margins crenate, apex conduplicate, keeled below, obtuse. Column 0.25 cm long, clinandrium denticulate, 3-lobulate, the lateral lobules triangular, acuminate, the median acuminate, stigma oblong; column-foot at an acute angle to the ovary, broadly linear, c. 0.5 cm long, strongly incurved, concave, with a longitudinal crest, apex obtuse; anther cucullate, rounded-quadrangular, in front truncate and papillose. Pollinia oblong.
(after Smith, 1909).

Colours:

Sepals and petals inside white or lilac, outside pale yellow, lip white, on the lateral lobes with dark purple stripes, the keels in upper part of the lip with purple spots.

Habitat:

Epiphyte on trees in Metroxylon swamps at low altitudes, also in savannah, rainforest and hill forest. Altitude 0 to 400 m.

Distribution:

Moluccas, Bismarck Archipelago, New Guinea.

Distribution New Guinea:

Papua (Merauke and Jayapura Regencies); Papua New Guinea (Gulf, Madang, Central, Milne Bay, and East New Britain Provinces).

Cultivation:

Warm growing epiphyte.

Flowering time in the wild:

August to March.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Genus Dendrobium
Section Diplocaulobium
Subsection Diplocaulobium
Species Dendrobium hydrophilum

Literature:

O'Byrne, P. 1994. Lowland Orchids of Papua New Guinea: 208, fig.
Smith, J.J. 1916. Nova Guinea 12, 4: 291.

Notes:

According to O'Byrne (1994) Dendrobium hydrophilum J.J.Sm. is the most common lowland species of section Diplocaulobium in Papua New Guinea.

Dendrobium hydrophilum J.J.Sm. should be compared with Dendrobium pentanema Schltr., when they are conspecific the name Dendrobium pentanema Schltr. has priority.

The position of Dendrobium hydrophilum J.J.Sm. in subsection Diplocaulobium is questionable.