Orchids of New Guinea

Dendrobium macrolobum

Dendrobium macrolobum J.J.Sm., Bull. Jard. Bot. Buitenzorg, sér. 2, 2 (1911) 8

Type: :Kock, de VI (holo BO).

Synonyms:

Cadetia macroloba (J.J.Sm.) Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 424.
Cadetia angustecalcarata Gilli, Ann. Naturhist. Mus. Wien 84, B (1980 publ. 1983) 17, fig. 3.
- Type: Gilli 467 (holo W).
Cadetia hispidula Dockrill, J. Orchidol. 2 (1961) 92 (non Rich.

Roots to more than 25 cm long, 1-1.5 mm diameter. Rhizome short. Pseudobulbs crowded, cylindrical, smoothly 4-ribbed, (1-)1.4-4.5 cm long, 3-5 mm diameter (often c. 2 mm diameter in dried material). Leaf linear to oblong, index 2.5-10, 2-4.8 cm by 4-8 mm, base cuneate, apex obtuse, minutely bilobulate, mucronate, mucro longer than the lobules. Inflorescences terminal from the leaf axil and subterminal just below the abaxial side of the leaf; solitary or up to 4 in succession from the same position, at the base with a 4-7 mm long tubular sheath and a 2-9 mm long spathe. Peduncle 5-8 mm long. Ovary and pedicel 1.9-2.8 cm long, 3-winged, glabrous. Flower c. 1.5 cm across. Median sepal patent, narrowly elliptic to lanceolate, 7.2-10.4 by 2.5-2.9 mm, obtuse, 3-nerved. Lateral sepals patent, obliquely narrowly elliptic to obliquely narrowly lanceolate, 7.2-12.0 by 2.7-3.9 mm, obtuse, 3-nerved; mentum narrowly cylindrical, more or less incurved, 3.8-7 mm long, entirely closed, apex rounded. Petals porrect, apical half reflexed, obliquely lanceolate, 6.8-10.7 by 2.1-2.5 mm, entire, acuminate, 3-nerved. Lip spathulate, 3-lobed, subglabrous to shortly pubescent on basal part of midlobe; hypochile 6.2-10 mm long, of which the narrow claw is adnate to the column foot, 5-7 mm wide across the flattened lateral lobes; lateral lobes erect, obliquely semi-elliptic, 1.9-3 by 1.3-1.9 mm, entire or with irregular margins, apex rounded; midlobe subflabellate to broadly obovate-spathulate, clawed, 7.1-12 by 5-9.6 mm, fleshy, margin more or less irregular, apex broadly rounded, sometimes apiculate; callus narrowly oblong, often hardly developed, papillose to pubescent, on basal third of midlobe, entire. Column 1.8-3.0 mm long, glabrous, wings (obtusely) triangular, entire, margins glabrous to shortly pubescent, clinandrium entire, with a narrowly triangular median tooth; foot 3.8-7 mm long, glabrous. Anther cucullate, 0.8 by 0.9 mm, base emarginate; apex truncate, papillose-pubescent; pollinia 0.7 mm long. Fruit obliquely obovoid, c. 15-18 by 7 mm, 3-winged.

Colours:

Flower pure white; claw of midlobe sometimes yellowish green.

Habitat:

Epiphyte in upper montane forest, e.g. on trunks of Nothofagus. Also terrestrial on banks covered with wet moss and lithophytic on moss-covered limestone boulders. Altitude 2000 to 3250 m.

Distribution:

New Guinea (endemic).

Distribution New Guinea:

Papua (Puncak Jaya and Jaya Wijaya Regencies); Papua New Guinea (Enga, Southern Highlands, Simbu, and Central Provinces).

Map: Dendrobium macrolobum J.J.Sm., distribution map.

Cultivation:

As for other cool growing Cadetia species, see Dendrobium chionanthum Schltr..

Flowering time in the wild:

January, February, September, October, December.

Literature:

Royen, P. van. 1979. Alp. Fl. New Guinea 2: 294, fig. 102.

Notes:

Dendrobium macrolobum J.J.Sm. may be recognized by the large, clawed midlobe, which is broadly rounded in front, in combination with the lanceolate, acuminate petals. This species appears to be somewhat variable in the size of the mentum and that of the midlobe; also in some collections the callus is distinctly pubescent, whereas in others, including the type, it is almost glabrous. It is closely related to Cadetia lacorum.