Epiphytic climber, stems of indeterminate length, branching, c.5mm in diam. on flowering part, rooting along internodes, well clad in hairs to 2mm long, mostly acute, some gland-tipped, bark pale, glossy, brittle. Leaves opposite, strongly anisophyllous, reduced leaves soon caducous, c.14 × 7mm, ovate narrowed to a petiolar part, hairy as developed leaves; blade of largest leaves 80–110 × 40–50mm, ovate, apex acute, base cuneate, shortly decurrent, margins serrate or doubly serrate, lateral veins 7–8, looping near margin and merging with it, upper surface well clad in acute hairs to 1.2–2mm long, lower surface densely pubescent, hairs acute, to 1.5mm long over veins, mostly shorter on blade, finer than those on upper surface; petiole 33–50mm long, densely clad in acute spreading hairs to 2mm long. Inflorescence a crowded cyme, flowers c.19, peduncle 320–415mm long, pubescent, hairs acute, to c.0.2mm long together with scattered ones to 2mm, spreading. Bracts (lowermost pair) c.12 × 3.3mm, elliptic, acute hairs to 1.2mm long on margins and dorsal surface, to 0.8mm on ventral surface, minute globular glands on both surfaces. Pedicels 4–6mm long, clad in short acute upward-pointing hairs together with scattered hairs to 1mm. Calyx tube c.2.3–3.2mm long, lobes 5, subequal, 4–5.2 × 2–2.2mm, longer than tube, narrowly deltoid, acute, tipped with short blunt gland, minute globular glands both inside and out, outside well clad in acute hairs c.0.1–0.5mm long together with scattered hairs c.1mm long, on margins c.0.2mm long. Corolla c.30mm long, tube c.24mm, funnel-shaped, arcuate, mouth more or less round, posticous lobes c.7 × 6.2mm, subrotund, anticous lobe c.7.5 × 5.3mm, broadly elliptic, corolla ‘reddish magenta, inside yellowish with purplish streaks’, lobes fringed with gland-tipped hairs c.0.3mm long together with shorter acute ones, outside pubescent to base, hairs gland-tipped, to 0.8mm long mainly on posticous side, acute hairs elsewhere, inside lobes minute acute hairs less than 0.1mm long, small patch of globose papillae between points of insertion of anticous filaments, raised into 2 or 4 small flaps, elsewhere glabrous, annulus wanting. Stamens 4, anticous filaments c.14mm long, inserted 12mm above base of tube, anthers 3mm long, not exceeding length of posticous lobes; posticous filaments c.12mm long, inserted 13mm above base of tube, anthers 2.5mm long, in mouth; staminode c.0.8mm long. Disc 1×1.6mm, glabrous. Ovary 13×1.2mm, glabrous. Style 2.5mm long, clad in minute globose glands. Stigmatic lobes (W phase) 1.2 × 1.2mm, backs clad in minute globose glands. Capsules: only shreds seen, longest 150mm. Seeds not seen. (Hilliard & Burtt, 2002a)

Agalmyla obiana is known only from the type collection made on Obi Island, lying south of Halmahera, and seldom visited. It was collected in ‘rather dense primary forest 40m high, with rather little undergrowth’.

It is distinguished from A. stellifera by its leaves, hairy on both surfaces, densely so on lower surface, and calyx lobes roughly twice as long as broad and hairy all over the backs (not roughly as long as broad, hairs on the backs confined to a median deltoid patch).