Orchids of New Guinea

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Dendrobium lactiflorum

Dendrobium lactiflorum (Schltr.) J.J.Sm., Bot. Jahrb. Syst. 66 (1934) 187

Type: Ledermann 8403; 11146; 11365 (syn B, lost).

Synonyms:

Cadetia imitans Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 428; 21 (1923) t. 146
- Type: Schlechter 19680 (holo B, lost).
Dendrobium subretusum J.J.Sm., Bull. Jard. Bot. Buitenzorg, sér. 2, 8 (1912) 17 (nom. nov.).
Cadetia lactiflora Schltr., Bot. Jahrb. Syst. 58 (1922) 92.
- Type: Ledermann 8403; 11146; 11365 (syn B, lost).
Dendrobium lactiflorum (Schltr.) J.J.Sm., Bot. Jahrb. Syst. 66 (1934) 187.

Roots to more than 14 cm long, 1-1.5 mm diameter. Rhizome very short. Pseudobulbs crowded, cylindrical, weakly 4-ribbed, 8-30 mm long, 2.5-3.5 mm diameter. Leaf linear-oblong to oblong, index 3-6, 1.1-2.5 cm by 3-4.5 mm, base cuneate to subpetiolate, apex obtuse, apiculate. Inflorescences terminal from the leaf axil and subterminal just below the abaxial side of the leaf; solitary, rarely 2 asynchronous from the same position, at the base with a 3 mm long tubular sheath. Peduncle 3-5.8 mm long. Ovary and pedicel 10-15 mm long, 3-winged, glabrous. Flower c. 1.3 cm across. Median sepal reflexed, narrowly triangular to lanceolate, 5.9-7.9 by c. 2.4 mm, subacute, 3-5-nerved. Lateral sepals patent, lanceolate-oblong, slightly oblique, 6.6-7.5 by c. 2.7 mm, subacute, 3-4-nerved; mentum cylindrical, straight, 5.5-6.4 mm long, of equal width throughout or slightly narrowed to the apex, apical closed part c. 4 mm. Petals porrect, lanceolate, 5.4-7.1 by 1.4-1.7 mm, entire, obtuse to subacute, 3-nerved. Lip subspathulate, weakly 3-lobed, papillose on the callus otherwise glabrous; hypochile 7.5-8.6 mm long, of which c. 0.5 mm fused with the column foot, 1.4-2 mm wide across the flattened lateral lobes; lateral lobes very small, narrowly triangular, 0.7-0.9 mm long, entire, subacute; midlobe ovate, 3.4-4.6 by c. 1.9 mm, entire, obtuse, more or less apiculate; callus oblong, papillose, extending from the apex of the hypochile to halfway the midlobe, entire. Column 1.3-1.6 mm long, wings rectangular, obscurely bidentate; clinandrium entire, with a narrowly triangular median tooth; foot 5.7-7.1 mm long. Anther cucullate, c. 0.7 by 0.8 mm, base emarginate; apex truncate, pubescent-papillose; pollinia c. 0.8 mm long. Fruit ellipsoid, c. 8 by 4 mm, 3-winged.

Colours:

Flower pure white. Anther sometimes green.

Habitat:

Epiphyte on tree trunks in montane forest. Altitude 1100 to 2000 m.

Distribution:

New Guinea (endemic).

Distribution New Guinea:

Papua (Sorong Regency, perhaps also in Yapen Waropen); Papua New Guinea (Sandaun, Morobe, Central and Milne Bay Provinces).

Map: Dendrobium lactiflorum (Schltr.) J.J.Sm., distribution map.

Cultivation:

Intermediate to cool growing epiphyte, requires light shade and excellent drainage, but should never be allowed to dry out.

Flowering time in the wild:

January, February, April, June, July.

Notes:

Dendrobium lactiflorum (Schltr.) J.J.Sm. is very similar to Dendrobium chamaephytum Schltr.. The latter has a much shorter mentum as well as a thick fleshy midlobe. In the present species the midlobe, apart from the central callus, is not fleshy. Dendrobium cyclopense J.J.Sm. differs in the usually curved mentum that is swollen at the apex.