A REVIEW OF ALOCASIA (ARACEAE: COLOCASIEAE) FOR THAILAND
pubescent abaxially (not in Thailand), juvenile lamina peltate, at maturity usually sagittate, less often ± hastate or cordate, peltate in some species, margin entire, sinuate or slightly to deeply pinnatifid (the last two states not in Thailand), posterior divisions ovate or triangular; basal ribs well-developed, waxy glands present in axils of primary lateral veins and midrib, primary lateral veins pinnate, forming submarginal collective vein,1–2 closely adjacent marginal veins also present, secondary and tertiary lateral veins arising from the primaries at a wide angle, then arching strongly towards leaf margin, sometimes forming interprimary collective veins (‘colocasioid venation’), higher order venation reticulate. Inflorescences 2–many in each floral sympodium, appearing with the leaves in seasonally dormant species. Peduncle usually shorter than petiole, erect, occasionally declinate at fruiting. Spathe strongly constricted between tube and limb, tube with convolute margins, shorter than blade, ovoid or oblong, persistent and then splitting irregularly in fruit; limb oblong, usually boat-shaped, rarely fornicate, at anthesis at first erect, then reflexing and later usually deciduous. Spadix sessile, or sometimes shortly stipitate, rarely obliquely adnate to lower spathe, mostly shorter than spathe, female flower zone short, conoid-cylindric, separated from male flower zone by a narrower zone of sterile flowers; male flower zone usually cylindric, appendix conoid to cylindrical. Flowers unisexual, perigone absent. Male flowers 3–12(–36)-merous, stamens connate into an obpyramidal, subhexagonal, truncate, rarely linear synandrium, thecae oblong to linear-oblong, lateral, dehiscing by apical pore. Sterile male flowers synandrodia, shallow, obpyramidal, compressed, truncate; female flower with ovary ovoid or oblong, 1-locular or partially 3–4-locular at apex, ovules 6–10, orthotropous, hemiorthotropous, hemianatropous or anatropous, funicle short, placenta basal, stylar region short, stigma depressed-capitate, ± distinctly 3–4-lobed. Fruiting spathe ellipsoid, very rarely the whole spathe persistent (not in Thailand), fruit revealed by the lower spathe splitting longitudinally-basicopically. Fruit an ellipsoid or obconic-ellipsoid or subglobose berry, 1–5-seeded, stigma remnants persistent, generally ripening red. Seed subglobose to ellipsoid, testa thickish, smooth or scabrous, embryo broadly conoid, shortly cylindric or elongate, endosperm copious.
In excess of 100 species distributed from the subtropical eastern Himalayas throughout subtropical and tropical Asia into the tropical western pacific and eastern Australia. Many species are yet to be formally described. Nine species in Thailand, one (A. hypoleuca) endemic. Habitat in primary and secondary forests, early regrowth and open swamps, sometimes lithophytic, rarely rheophytic; primarily in everwet conditions, but some species tolerant of quite strong seasonality; predominantly in the lowlands, extending from sea level to lower and mid-montane zones. Two (A. macrorrhizos (L.) G.Don and A. cucullata (Lour.) G.Don) are found only in association with human disturbance and almost certainly ancient cultigens.
KEY TO THE SPECIES
Plants massive, pachycaul. At least 1m tall.
Sinus between posterior leaves peltate
Plant with short stolons at the base of the main stems, these stolons with tuberules at the tips.
Spathes greenish white
Plant lacking stolons. Spathes deep yellow
Sinus between posterior leaves naked