Orchids of New Guinea

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Dendrobium angustitepalum

Dendrobium angustitepalum (W.K.Harris & M.A.Clem. ) Schuit. & de Vogel Malesian Orchid J. 4: 104. 2009

Type: Australian National Botanic Gardens cult. (M.A. Clements 9631, ex National Capital Botanical Gardens, Port Moresby) (holo CANB; iso BRI)

Synonyms:

Diplocaulobium angustitepalum W. K. Harris & MA. Clem., Orchadian 13 (2002) 566, fig.

Epiphytic, erect to creeping herb, c. 10-15 cm tall. Rhizome short, covered with scarious sheaths. Pseudobulbs when young covered in scarious sheaths, close together on young plants but more distant on old rhizomes, somewhat dorso-ventrally flattened, of two types: sterile pseudobulbs short, fusiform, 2.5-6.5 by 0.6-1.4 cm, in apical part c. 0.2-0.4 cm diameter; flowering pseudobulb much longer, 8.5-35 cm long, in lower 2-4 cm slightly swollen to 0.5 cm diameter, in apical part c. 0.15-0.2 cm diameter. Leaf one per pseudobulb, erect, rather stiff, channeled, linear, on sterile pseudobulbs 4-10 by 0.4-0.5 cm, on fertile pseudobulbs 13.5 by 0.3-0.7 cm, minutely bilobed at the apex. Inflorescences terminal, 1(-2) per pseudobulb, 1-flowered. Spathe lanceolate, 1.2-1.5 cm long. Flower nodding, perianth segments not widely spreading. Pedicel and ovary 1.5-3 cm long, erect to sub-erect, ovary not developed at anthesis. Median sepal narrowly linear, 1.9-2.2 by 0.1-0.15 cm at the base, tapering gradually to about 0.03 cm at the acuminate apex. Mentum shallow, c. 0.12 cm deep. Lateral sepals narrow linear, 1.9-2.2 by 0.1-0.15 cm at the base, tapering gradually to about 0.03 cm at the acuminate apex. Petals narrowly linear, 1.5-1.8 by c. 0.05-0.07 cm at the base, tapering gradually to c. 0.05 cm at the acuminate apex. Labellum porrect, linear, 0.45-1.1 byc. 0.01-0.13 cm in the proximal quarter, narrowing to c. 0.07 cm distally; margin inrolled distally. Column 0.2 cm long, porrect from the ovary, with a 0.2 cm long column foot, slightly curved, with prominent fine stelidia. Stigma deeply concave, hollow, c. 0.1 cm diam. Anther ovate, c. 0.1 by 0.15 cm. Pollinia obovoid, c. 0.05 cm long. Fruit not seen.
(after Harris & Clemens, 2002)

Colours:

Rhizome sheaths pale straw-coloured. Pseudobulbs when young covered in pale straw-coloured sheaths. Spathe light orange-yellow. Flower uniformly yellowish orange, not turning pink when ageing. Pollinia light yellow.

Habitat:

Lowland primary forest, with closed to rather open canopy. Altitude 150-800m.

Distribution:

New Guinea (endemic).

Distribution New Guinea:

Papua New Guinea (West and East New Britain Prov.); see map

Cultivation:

Warm growing epiphyte.

Flowering time in the wild:

In cultivation in Hortus botanicus Leiden February-October.

Classification:

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

Notes:

Dendrobium angustitepalum (W.K.Harris & M.A.Clem. ) Schuit. & de Vogel, like Dendrobium nitidissimum Rchb.f. (the type species of the section Diplocaulolobium), is an easily recognisable species because the plants produce two entirely different types of pseudobulbs: relatively short pseudobulbs, and much longer and very slender pseudobulbs only slightly swollen at the base. It differs in the tall pseudobulbs, which have equally large leaves as the short pseudobulbs (versus leaves on the flowering pseudobulbs much shorter than those on the sterile pseudobulbs), and the yellow flowers of which the lip lacks a farinose callus (versus flowers mainly white and lip with a farinose callus).

Dendrobium angustitepalum (W.K.Harris & M.A.Clem. ) Schuit. & de Vogel has yellow flowers and a very small lip and lacks the dome-shaped farinose callus and its position in subsection Diplocaulobium is questionable.