Dendrobium pachythrix T.M.Reeve & P.Woods, Notes Roy. Bot. Gard. Edinburgh 46 (1989, publ. 1990) 215, fig. 15, pl. 10c.
Type: Daniels in herb Reeve 552 (holo LAE; iso E, K).
Small erect to suberect epiphyte, 1-3 cm high. Roots c. 0.5 mm diameter. Rhizome up to 3 mm long. Pseudobulbs 0.4-1.2 by 0.2-0.4 cm, globose to fusiform, apex (1-)2-leaved. Leaves 0.5-1.2 by 0.15-0.4 cm, erect to spreading, ovate to lanceolate, apex mucronate; sheaths smooth, membranous, with age becoming fibrous. Inflorescences terminal, arising mainly from leafy stems, 2-3-flowered, subsessile; bracts suborbicular, apiculate to acuminate. Flowers 1.1-1.7 cm long, long lasting. Median sepal 4-7 by 1.5-2.2 mm, oblong-ovate to oblong-elliptic, subacute to acute, outer side covered with thick hairs which are shorter towards the apex. Lateral sepals 11-16 by 2.5-3.5 mm, oblique, oblong-elliptic, acute to apiculate, outer side of free part covered with thick hairs (shorter ones papillose), hairs longest along the mid-vein; basal fused part 3-6 mm long, narrowly cylindrical; mentum total length 6.5-9.5 mm, tip obtuse or shortly bilobed. Petals 4-6.5 by 0.07-1 mm, linear to oblanceolate, acute. Lip 10-14 by 1.5-2 mm, subtrilobate, linear-oblanceolate, adnate to column foot at base, upper margins incurved, apex narrowly triangular, unbent or slightly deflexed. Column 1.5-2 mm long; foot 6.5-9.5 mm long; anther c. 1.5 mm broad; pollinia c. 0.8 mm long. Ovary 5-ribbed, covered with short thick hairs which are simple to 2-3-armed, hairs shorter and sparser on pedicel; pedicel and ovary 9-16 mm long. Fruit not observed.
(after Reeve & Woods, 1989).
Colours: Pseudobulbs reddish. Leaves green to purplish green on top, purplish underneath. Flowers red with orange lip tipped pale red.
Habitat: Epiphyte in montane forest or terrestrial (on road cutting). Altitude 1500 to 1700 m.
Flowering time in the wild: March, July.
Distribution: New Guinea.
Distribution in New Guinea: Papua New Guinea (Enga Province, Western Highlands Province).
Map: PACHTMAP.JPG [Dendrobium pachythrix T.M.Reeve & P.Woods, distribution map, redrawn from T.M. Reeve & P.J.B. Woods, Notes Roy. Bot. Gard. Edinburgh 46 (1989) 287, map 10.]
Notes: This species is most closely allied to Dendrobium subacaule which it resembles in habit and flower colour. It is distinguished by the 5-ribbed ovary (not sharply 3-winged) and the indumentum of short thick hairs on the ovary and the outside of the sepals. The thick hairs, from which the Greek epithet pachythrix is derived, are simple to 2-3-armed in the type and are up to 1.5 mm long. The smallest of them are found towards the apices of the sepals and lower down on the pedicel and could be classified as papillae.
There are only two other members of section Pedilonum with an indumentum on the ovary, Dendrobium masarangense subsp. theionanthum var. chlorinum and the variable Dendrobium cuthbertsonii, but neither has hairy sepals.
(after Reeve & Woods, 1989).
Cultivation: Probably as for Dendrobium subacaule.