Section Oxysepala

Bulbophyllum section Oxysepala (Wight) Benth. & Hook.f. (1883) 504 [as 'Oxysepalum']

Small to medium sized epiphytes. Rhizomes erect to stiffly or limply pendulous; thin, glabrous to papillose, caducous but veins thick, persistent as fibres. Roots mainly sprouting near the base of the rhizome, spreading (in species with a limply pendulous rhizome sometimes attaching to substrate if present), or growing over or alongside the rhizome towards the substrate, approx. glabrous. Pseudobulbs (rather) small compared to the size of the plant (long and distinct in Bulbophyllum floribundum), 1-leafed, with shoots sprouting from its basal node, not fused to the pseudobulb. Leaves persistent, thick, veins inconspicuous. Inflorescences sprouting from nodes along the length of the rhizome, at a (short) distance above the subtending rhizome bract attachment, densely fasciculate, fascicles often branching (several flowers simultaneously from a single rhizome node); 1-flowered. Peduncle short, not or barely protruding from the subtending rhizome bract, peduncle bracts 2, (sub-)basal. Flowers per sympodium branch 1 open at a time; floral bracts tubular; pedicel with the basal node level with the attachment of the floral bract, shorter to little longer than the ovary. Sepals free, the laterals not or hardly longer than the median; 3— 40 mm long, (rather) narrowly triangular, acute to caudate, glabrous, thin to rather thick, top thickened or not; (1— )3-veined. Petals 0.6— 2.5 mm long, elliptic to (ob-)ovate, retuse to acute, margins entire or distally slightly erose; thin, 1-veined, surface glabrous or distally somewhat papillose. Lip mobile on a thin ligament, undivided and without auricles, 1— 2.5 mm long, approx. (ob-)ovate to oblong, glabrous; adaxially without ridges, or with two converging flexural ridges, or with a transverse ridge near the base and a (weak) median ridge running from this towards the top. Column with rostellum front level with the stelidia tips or receding (protruding beyond stelidia tips in Bulbophyllum filicaule J.J. Sm.), stigma large, without keels inside, proximally not or slightly protruding, column foot tapering towards its top, free part virtually absent or present but short; with or without a slight swelling just short of the ligament. Stelidia approx. half the length of the column or shorter, deltoid to triangular, with or without a tooth along the upper margin, without a tooth along the lower. Anther abaxially with a low or high, rounded crest, front not concave, front margin not drawn out. Pollinia 2, or 4 and with the inner less than half as long as the outer; without appendages.

New Guinea: 21 taxa. Altogether 29 provisionally accepted taxa (45 names): Myanmar and Indochina to Pacific. Range extension largely determined by Bulbophyllum clandestinum Lindl., Australia excepted.

Section Sphaeracron includes species with a more limply pendulous rhizome, thickened sepal tips and often with a transverse ridge near the base of the lip, on the adaxial side. The synonymy is based on overall similarity between this and section Oxysepala, and the presence of intermediate species (e.g. Woods 331 [E], unidentified, generally similar to section Oxysepala but with a transverse ridge on the lip as in section Sphaeracron; and Bulbophyllum hollandianum J.J. Sm., with thickened sepal tips but a lip as in section Oxysepala).
Bulbophyllum floribundum was thought to be related to Bulbophyllum versteegii (Section Brachypus) by J.J. Smith. Apart from the conspicuous pseudobulbs, the general habit and flower morphology are similar to section Oxysepala. Lack of material prevented checking the distinguishing character (the position of the pedicel node), the species has provisionally been included here.

The following taxa in this program belong to this Section:
Bulbophyllum citrinilabre
Bulbophyllum clandestinum
Bulbophyllum filicaule
Bulbophyllum flavum
Bulbophyllum floribundum
Bulbophyllum hollandianum
Bulbophyllum kauloense
Bulbophyllum korimense
Bulbophyllum pachyacris
Bulbophyllum piliferum
Bulbophyllum pseudofilicaule
Bulbophyllum pungens
Bulbophyllum pungens var. pachyphyllum
Bulbophyllum rhopalophorum
Bulbophyllum riparium
Bulbophyllum semiteres
Bulbophyllum sphaeracron
Bulbophyllum subtrilobatum
Bulbophyllum subulifolium
Bulbophyllum tenue
Bulbophyllum theioglossum
Bulbophyllum trichaete
Bulbophyllum triclavigerum