Cryptocoryne cordata var. siamensis
Deciduous herb to 1.3 m tall. Subterranean stem a subglobose, stoloniferous tuber, up to 4 cm across and 2 cm high, white, with stolons to 10 × 1 cm. Pseudostem ca 20 cm long, green, mottled grey and pink. Leaf solitary, exceptionally bifoliate; cataphylls to 20 cm long, purple; petiole to 1 m long, similar in colour to the pseudostem; leaf blade radiate; leaflets 7–11, ovate, 10–20 × 4–6 cm, margins entire, apex acute, ending in an acumen 1 cm long, base cuneate and sessile, leaflets plain green, with impressed veins above, underside paler. Inflorescence held below the foliage; peduncle 5–20 cm long, green and pink mottled; spathe tube cylindrical, 4–6 × 1–1.2 cm, green with thin white stripes, spathe mouth margins recurved; spathe limb lanceolate, 5–8 × 3–4 cm, green, flushed red-brown, ending in a long brown tail to 25 cm long; spadix appendix well exserted from the tube, 5–6 cm long × 3–4 mm wide, pale green, stout, cylindrical, ending in a rounded and rugose apex curving forward; sessile, pistillate inflorescences with green bristles above the fertile part; fertile zone staminate or pistillate, cylindrical, 1.5–2 cm long; staminate flowers loosely arranged; pistillate flowers densely arranged; ovaries bottle-shaped, green; stigma sessile, penicillate, white. Infructescence on an erect peduncle, globose, 3–5 cm; fruits red-orange when ripe, 8–10 × 5–7 mm, top rounded, up to 3 seeds per berry. Seeds globose, 3–4 mm diam.
Chromosome number: 2n = 102.
Peninsular Thailand. A recent report from northwest Peninsular Malaysia (Kedah) may belong to var. siamensis.
Small or large streams with more quickly running water in lowland forests where it usually occurs submerged. It can sometimes grow in sandy-bottomed streams in rubber plantations.