e-Flora of Thailand

Volume 11 > Part 2 > Year 2012 > Page 166 > Araceae > Amorphophallus

35. Amorphophallus operculatus Hett. & Sizemore

Aroideana 26: 113. 2003.


Accepted Name : This is currently accepted.


Description : Tuber elongate, thin, vertically rhizomatous, branching, 3–46 by 0.5–4 cm. Leaf solitary; petiole 10–65 cm by 4–15 mm, smooth, uniformly olive-green to dark rich reddish, sometimes with a few small, dark spots near the base; leaf blade moderately or highly dissected, 20–70 cm, rachises winged throughout; leaflets elongate ovate to ovate-lanceolate, 2–14 by 1–5 cm, apex acute-acuminate, fleshy, adaxially rich dark emerald green, margin reddish, abaxially dark greyish green, often flushed dark purple-violet, rachises on the abaxial surface rich dark reddish purple. Inflorescence: peduncle 33–50 cm by 6–8 mm, smooth, dull reddish mauve with or without a few darker, irregular indistinct spots at the base; spathe broadly triangular-elliptic, 8–12 by 6–11 cm, margins concave, base and limb hardly separated, base convolute, ca half the length of the spathe, not opening to the base during staminate anthesis, apex acute, exterior whitish changing to pale dirty greyish whitish near the base, veins pale pinkish, upper half suffused with a pale pinkish purplish hue, interior dirty whitish, apex with a pinkish purplish hue, base within densely clothed with mostly globose verrucae, those on the dorsal side and close to the spadix base elongate and/or slightly rugate, the entire inner surface of the base covered with a wet film; spadix sessile, longer than spathe, 10–14.5 cm long; pistillate flower zone cylindrical, 8–10 by 8–11 mm, flowers congested; ovaries subglobose, 2 by 1.8–2 mm, pale green; style elongate conical, 0.8–1.1 by 0.8 mm at the base, 0.5 mm at the apex, pale purple or pale green flushed pale purple; stigma depressed, ca 1–1.2 by 0.5 mm high, with a shallow irregular central depression, surface verruculate, off-white; staminate flower zone elongate, slightly conical, 3.5–4.8 cm by 8–14 mm, base constricted, apex slightly or more distinctly laterally compressed, flowers congested; staminate flowers 4–5-androus, the lower flowers with only 1–2 stamens; stamens 1–1.2 by 0.8–1 mm; anthers 0.5–0.7 mm long, truncate, pores apical, slightly elongate, those of the more isolated lower anthers lunate to entirely ring-like around the upper rim of the anther, the anther then seemingly operculate; appendix elongate conical, 5–8.2 cm by 9–15 mm at the base, thin-walled, terete or slightly laterally compressed, more distinctly near the base, apex acute, surface slightly and shallowly rugose, off-white. Fruiting peduncle as flowering peduncle, no elongation. Infructescence globose, 3 by 3 cm; fruit lageniform, sometimes slightly asymmetrical, 10–13 by 4–6 mm, apex knob-like and separated slightly from the main body of the berry by an indistinct constriction, ripening white.


Thailand : PENINSULAR: Chumphon (type: Sizemore s.n. cult. Sub. Hetterscheid H.AM. 994-T, holotype -L).


Distribution : Endemic.


Ecology : Not recorded.


Notes: Amorphophallus operculatus belongs to a small group of exclusively Thai species characterized by elongate, branching tubers, very dark velvety green leaves with thin purplish red margins and whitish spathes with concave margins. The other members of this group are A. saururus, A. pygmaeus, A. sizemoreae and A. vogelianus. From all these species, A. operculatus differs in the very long, thin tuber which, in the other species, is short and thick, and the operculate nature of the lower flowers, which is also not found in any of the other three species.


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