Bulbophyllum section Polymeres (Blume) J.J.Verm. & P.O'Byrne, Gard. Bull. Singapore 60 (2008) 126
Minute to medium-sized epiphytes. Rhizomes long- to short-creeping, straggling, shortly ascending, patent to stiffly or limply pendulous; rhizome bracts thin, approx. glabrous to minutely colliculate, sometimes minutely papillose, caducous (with the veins slightly more persistent). Roots either sprouting mainly below the pseudobulbs or from nodes along the length of the rhizome, in species with patent to pendulous rhizomes mainly near to the base of the rhizomes, growing backwards towards the substratum over or alongside the rhizome, glabrous or slightly and minutely hirsute locally. Pseudobulbs rather small to conspicuous compared to the size of the plant, 1-leafed, with shoots sprouting at its basal node and free or fused to the pseudobulb over a part or most of the length of the latter, or shoots sprouting above its basal node, perforating the pseudobulb over the distance between its basal node and the spot of emergence. Leaves persistent, thick, veins inconspicuous. Inflorescences sprouting at nodes along the length of the rhizome, or at the basal node of the pseudobulb only, in many species with patent to pendulous rhizomes always emerging from the same node, e.g. at or slightly below the basal node of the pseudobulb, or the first node of the shoot; single to densely fasciculate, 1-flowered. Peduncle shorter than the pseudobulbs to longer than the leaves, peduncle bracts 1— 4, scattered but the upper below half-way the peduncle. Flowers per sympodium 1 open at a time; floral bracts tubular; pedicel with the basal node well above the attachment of the floral bract, approx. as long as or distinctly longer than the ovary. Sepals free (the tips of the laterals also adherent or entwined in Bulbophyllum maxillare) or (partly) adnate, the laterals not or hardly longer than the median (distinctly longer in Bulbophyllum maxillare, Bulbophyllum nasica); 2— 58 mm long, elliptic, (ob-)ovate to triangular, obtuse to long-acuminate, margins entire, sometimes slightly erose, glabrous to papillose or ciliate (or minutely paleate); (rather) thin, 3— (4— 9)-veined, surface glabrous or finely papillose to hirsute adaxially. Petals 1— 14.5 mm long, (transversely) elliptic to (ob-)ovate, deltoid to (inverted) triangular, sometimes rhombiform or wedge-shaped, truncate to caudate, margins entire to erose, sometimes approx. fimbriate, glabrous to ciliate; thin, 1-veined (3-veined in Bulbophyllum caputgnomonis), adaxial surface glabrous to papillose to hirsute. Lip mobile on a thin ligament, with or without slight auricles near the ligament, undivided, 1— 14 mm long, orbicular, elliptic, oblong, (ob-)ovate to triangular, or with a short an wide basal part and a long and narrow top part, margins entire to slightly erose, glabrous to papillose or ciliolate; adaxially without ridges, or with a median ridge (a median knob in Bulbophyllum tricaudatum, Bulbophyllum tumoriferum) and/or with two (distinctly converging) ridges in approx. flexural position, sometimes with additional ridges, surface approx. glabrous to partly or entirely finely papillose or hirsute; abaxial surface often with a distinct, finely to coarsely papillose or hirsute patch in the middle part (often combined with an approx. glabrous adaxial side). Column with rostellum front (somewhat) receding in between the stelidia, stigma slit-like to wide, rounded, without keels inside, often proximally protruding or with a tooth (two lateral teeth in Bulbophyllum entomonopsis), column foot widening and often thickening towards its top, free part long or short, usually with two lateral teeth at the tip. Stelidia shorter to distinctly longer than 1/2 of the length of the column; sometimes short but not vestigial, approx. deltoid, to long-subulate, sometimes with a small or large tooth along the upper margin, without tooth along the lower, at most a slight, rounded widening present. Anther abaxially with a (low) rounded crest, front concave or not, front margin not drawn out. Pollinia usually 4, with the inner more or less than half as long as the outer, sometimes 2; without appendages.
New Guinea: 115 taxa. Altogether 163 provisionally accepted taxa (220 names): India (Andaman Islands), Thailand, Sumatra Java, east to West Pacific.
Morphologically, section Polymeres grades into section Brachypus and section Papulipetalum. Uniting all three would leave a group without a distinguishing character (the latter two do not have a widened and winged column foot typical for section Polymeres), keeping all three apart yields sectional boundaries which seem, and indeed may be, partly arbitrary, separating a few species groups which otherwise are rather similar. Here, the three are kept separate, Here, the three are kept separate, with the note that further investigation is needed. This should include the value of characters now ignored, such as rostellum shape.
Section Polymeres includes a wide range of different growth forms (states: rhizome creeping to straggling/ascending to pendulous), and pseudobulb morphologies (states: young shoots arising from the basal node, not fused to the pseudobulb/ditto, fused to the pseudobulb/young shoots arising above the basal node). The series below are based on these characters. Possibly, they are artificial; see note below series a. The couples: series b and c, and series c and d each include species which show marked similarity apart from the distinguishing characters. Each series includes a suite of species with the same general flower morphology including that of the lip: outline elliptic, ovate or oblong, adaxial surface without ridges, glabrous, abaxial surface papillose or hirsute, particularly in the middle part (e.g. Bulbophyllum betchei F. Muell.). Each series also includes species with a widely deviating lip morphology, but deviating differently per series.
Within section Polymeres, Vermeulen & O'Byrne (2008: 126) distinguish 3 groups among their newly described Sulawesi species, while admitting that the division has no value elsewhere. Indeed it has not, it is too detailed and leaves many extralimital species unplaceable: all 3 groups are included in series b below.
a (Section Vesicisepalum)
Sepals (partly) adnate.
Includes a small series of species probably of various phylogenetic affinity within section Polymeres. Bulbophyllum ustusfortiter, previously in section Vesicisepalum, is included in section Brachypus.
b (Sections Polymeres, Micromonanthe, Megaloglossum, Elassoglossum)
Rhizomes creeping or straggling, roots spreading. Pseudobulbs distant to clustered. New shoots arising from the basal node of the pseudobulb. Sepals free.
c (Sections Leptopus, Rhizocaulon)
Rhizomes shortly ascending, patent to stiffly or limply pendulous. Roots growing backwards towards the substratum over or alongside the rhizome. New shoots arising from the basal node of the pseudobulb. Sepals free.
d (Sections Fruticicola, Epibulbon)
Rhizomes shortly ascending, patent to stiffly pendulous. Roots growing backwards towards the substratum over or alongside the rhizome. New shoots sprouting above the basal node of the pseudobulb, perforating the pseudobulb over the distance between its basal node and the spot of emergence. Sepals free.
The perforated part of the pseudobulb varies in length but is little variable within the species. In some the new shoots arise just above the base of the pseudobulb, in others close to the tip.
The following taxa in this program belong to this Section:
Bulbophyllum ischnopus var. rhodoneuron