Bulbophyllum gymnothema J.J.Verm., Schuit. & de Vogel, sp. nov.

(Fig. 13)

TYPE: Papua New Guinea, Chimbu Province, Mount Wilhelm, between Kombugomambuno moraine and Keglsugl, 2900 m alt., 9 July 1980, Goetghebeur & Coppejans 3782 (holotype L! 0738050; isotypes L! (spirit material), GENT (herbarium and spirit material)).

DIAGNOSIS. Within series C, it shares the partly bare rhizome (not entirely covered by scales) with Bulbophyllum nudicaule and B. tricaudatum J.J. Verm. It differs from the first by the narrower sepals (median sepal ratio length/width 3.7–3.8, versus 1.5–2.1) as well as by the almost glabrous lip with only slightly and minutely papillose margins towards its base (versus coarsely papillose except near apex). It differs from the second by the ovate-oblong lip (versus lip divided into an obovate-oblong, wide basal part and a linear, narrow apical part).

Medium-sized epiphyte with patent, branched rhizomes. Rhizome ca. 3.0 mm diam., sections between pseudobulbs ca. 2.5 cm long, arising from the basal node of the pseudobulb; rhizome scales thin, leaving parts of the rhizome bare, rather persistent. Pseudobulbs distinct, cylindrical, 2.4–3.0 × 0.3–0.4 cm. Leaf: petiole 2.0—5.0 mm long; blade elliptic to ovate, 4.4–5.2 × 0.6–1.0 mm, ratio length/width 4.9–7.4; acute. Inflorescences single or few together from nodes along the rhizome, 2.9—3.3 cm long, 1-flowered. Peduncle 9–11 mm long, scales 3. Floral bracts 5.0– 5.5 mm long. Flowers: pedicel plus ovary 9.0–10.0 mm long, basal node 3.0– 3.5 mm above the floral bract attachment. Median sepal free, recurved, elliptic, ca. 11.2 × 3 mm, ratio length/width 3.7–3.8; acuminate, margins entire, distally ciliolate, surface glabrous; 5-veined. Lateral sepals as the median but ovate, ca. 11.5 × 3.5 mm, ratio length/width 3.2–3.3, upper margin glabrous. Petals porrect, elliptic-ovate, ca. 5.0 × 2.5 mm, ratio length/width ca. 2; acuteacuminate, margins entire, upper papillose, lower ciliolate, surface glabrous; 1-veined. Lip recurved in the basal half, ovate-oblong, ca. 6.2 × 2.2 mm, ratio length/width 2.8—2.9 (without spreading); rounded, margins entire, slightly and minutely papillose proximally, surface glabrous; very thick; adaxially concave close to the base and with two short, narrow ridges which start near the margins and then converge, leaving a wide gap in between, surface elsewhere convex, abaxially convex with a deep median furrow. Column including stelidia ca. 2.5 mm long, stigma elliptic, with a protruding callus just below it, foot distally widened, triangular, with small, patent, obtuse lateral lobes near the apex. Stelidia slightly sigmoid, triangular-subulate, ca. 1.7 mm long, acute.

COLOURS: unknown.

ETYMOLOGY: gymnos (Greek) = naked, thema (Greek) = stem, referring to the rhizome which is not entirely covered by bracts.

HABITAT AND ECOLOGY: not recorded. Elevation 2900 m.