Homalomena pineodora (Araceae)
Dwarf creeping evergreen strongly aromatic (terpenoids - reminiscent of Pinus) when cut or crushed herb to 25 cm tall; cut surfaces producing copious watery, later sticky, aromatic sap. Stem rhizomatous, creeping, c. 8-10 mm diam., rooting along its length over the entire surface, oldest parts of stems clothed with papery to fibrous leaf base remains, roots penetrating this fibrous layer, roots also penetrating the leaf bases in the lower active portion; distal active shoot erect to semi-procumbent; active part of shoots densely clothed with spiro-distichous leaves; shoots pleionanthic. Leaves clustered towards shoot tips; petiole partially clasping the rhizome and then expanding into a persistent petiolar sheath, petiole 8.5–9 cm long, non-sheathing portion c. 2.5 mm diam., weakly D-shaped in cross-section and dorsally shallowly grooved, the groove extending to the insertion of the lamina; sheath extending to c. ¾ petiole length, margins hyaline, long-persistent; lamina leathery, elliptic to weakly oblongo-elliptic, 9–12 x 4–5 cm, base cuneate to ovate, apex acute with a prominent 3.5–4 mm long tubule, margins minutely hyaline (margins c. 0.5 mm wide) and tending to crispulate at the petiole insertion, abaxial surface pale green with up to 5 (mostly 3–4) weakly prominent and slightly darker primary lateral veins on each side of the mid-vein; interprimaries much less prominent and not at all darker than the abaxial lamina; adaxial lamina surface slightly lustrous dark green, primary lateral veins slightly impressed, interprimary veins hardly discernible. Inflorescences nodding, two together, maturing sequentially, each subtended by a two-keeled prophyll. Peduncle c. 5 cm long, 2.5 mm diam., weakly D-shaped in cross-section and expanding distally at the insertion of the spathe. Spathe unconstricted, ovate-ellipsoid, inflated and gaping at anthesis, c. 3 x 1.8 cm (rolled) (5.5 cm wide when flattened) ovato-triangular, apex acuminate; spathe exterior glossy bright green, the upper half deeper green, the lower half somewhat yellow-white, at anthesis spathe margins recurved, hyaline and slightly brownish along the edge; spathe interior glossy greenish white. Spadix 20 x 8 mm, stipitate, stipe c. 1 mm. Pistillate flower zone 6 x 6 mm with a zone of very slender-stalked globose-claviform 0.1 x 0.2 mm glossy white staminodes basally. Ovaries compressed-globo-cylindrical, 0.2 x 0.4 mm, stigma sessile, circular and slightly umbonate, overhanging the ovary, 0.7 x 0.4 mm, ovaries pale green, stigma translucent greenish white. Male flower zone ovoid, 10 x 7 mm, fertile to the apex, flowers comprised of two stamens, rarely one stamen aborted, 0.4 x 0.5 mm, connective barely prominent, male flowers pale cream. Infructescence and seeds not observed.
The rhizomatous stems, pleionanthic shoots and inflorescences nodding at anthesis immediately distinguish Homalomena pineodora from any Homalomena hitherto described from Peninsular Malaysia and adjacent peninsular Thailand. Rhizomatous creeping stems are a feature of two species described from Sumatera (H. elegantula A.Hay & Herscovitch, H. hastata M.Hotta,) and one from Java (H. bellula Schott). Among characters that distinguish these species from H. pineodora are hapaxanthic shoots (all), inflorescences erect at anthesis (all), hastate leaves (H. hastata), apically geniculate petioles (H. elegantula) and smaller (1 cm long) spathes (H. elegantula). An as yet undescribed Homalomena from Ba Vi, north Vietnam, has rhizomatous creeping stems, pleionanthic shoots and nodding inflorescences but differs from H. pineodora by the longer petioles with the petiolar sheath c. 1/4 the length of the petiole, broader ovato-cordate leaf laminae, a longer, narrower spadix and a markedly different smell produced by the crushed tissue (the Ba Vi Homalomena has a smell resembling Juniperus — H. pineodora smells of Pinus). The odours produced by the damaged tissue of H. elegantula, H. hastata and H. bellula are not recorded.
Peninsular Malaysia (NW Perak), known only from the type collection.
Riverside, growing in clumps on an inundated site under forest canopy.