International Aroid Society
  Generic Diagnosis of Amorphophallus Blume

by Wilbert Hettersheid and S. Ittenbach

The information here in is adapted from W. Hetterscheid and S. Ittenbach, 1996, "Everything You Always Wanted to Know About Amorphophallus, but Were Afraid to Stick Your Nose Into!!!!!", Aroideana 19: 7-131.

Habit Peduncle Anthers
Leaves Spathe Infructescence
Petiole Spadix Seed
Lamina Female Flowers  
Inflorescence Male Flowers  

Habit: Small to massive terrestrial plants, herbaceous; stem subterraneous, tuberous, rarely a chain of tubers or rhizomatous; tuber globose, subglobose, depressed-globose, saucer-shaped or vertically elongate and then unbranched or branched, representing one module and being renewed each season; chains consisting of tubers not being renewed every season; rhizomes long, terete, creeping, horizontal, consisting of several modules; offset-development absent, seasonal or gradual; offsets globose, spindle-shaped, shortly elongate or rhizomatous.

Leaves: Leaf usually solitary, rarely paired, emerging from the top of the tuber or rhizome, lasting one growing-season or rarely long-lasting.

Petiole: Petiole terete, rarely angulate, smooth, shallowly grooved or partly rugulose, rarely entirely verrucate or hairy, unicolorous or variously blotched.

Lamina: Lamina decompound and divided in three main branches; main branches equally long or the anterior main branch shorter than the posterior main branches (subpedate); rhachises unbranched, overtopped or once or more pseudodichotomously branched; secondary rhachises simple or variously branched; rhachises naked, narrowly or broadly winged and often carrying supernumerary leaflets on the proximal parts; sometimes bulbils develop on the leaves, either epiphyllar, intercalary or half-epiphyllar; distal leaflets obovate, elliptic, elongate-elliptic, elongate, oblong, lanceolate or linear, sessile or rarely petiolulate, base often asymmetric and decurrent on one side, apex acute, acuminate or rarely caudate, margin entire rarely erose, often undulate, upper side green or dark green, rarely with reddish margin or variegation.

Inflorescence: Inflorescence epigeal, rarely partly buried, solitary or simultaneous with or directly preceeding leaf development, rarely emerging after leaf development.

Peduncle: Peduncle short or long, often sculptured and patterned as petiole, when short often elongating in fruit.

Spathe: Spathe elongate-triangular, triangular or ovate to broadly ovate, variously shaped, often cymbiform or campanulate, more rarely funnel-shaped, outside variously colored but often shades of brownish-purple or whitish-green, inside mostly paler than outside but base within often dark maroon; base convolute, rarely open or connate, not or clearly separated from the limb by a constriction, oval, rounded, urceolate or funnel-shaped in longitudinal section, inside smooth or clothed with ridges or warts, the latter small or large, short or hairlike, sometimes forming ridges; limb rimshaped or broadly or elongate triangular, erect, spreading, oblique, or fornicate, margin entire or rarely lobed, flat, undulate or rarely plicate, apex acute, rarely acuminate or rarely caudate.

Spadix: Spadix sessile or shortly stipitate, shorter than, equalling or longer than spathe; female zone cylindric, fusiform, conic or obconic, contiguous with male zone or separated by a sterile zone, flowers congested or rarely distant, sometimes surrounded by staminodes; sterile zone consisting of staminodes, rarely mixed with pistillodes, rarely partly or entirely naked; male zone cylindric, fusiform, conic or obconic, flowers congested, rarely distant, often variously fused in the upper part of the zone, sometimes fused into vertical rows or helically or verticillate, sometimes mixed with staminodes; appendix rarely absent, contiguous with male zone or separated by a constriction or a short stipe, erect, rarely horizontal, arching, nodding or pendulous, outline conic, fusiform, triangular, myosuroid, ovate, subglobose or globose, sometimes with large longitudinal folds or deep cracks, surface smooth, rugulose, or with distinct, variously shaped staminodes, often only at the base, often warming up during female anthesis and spreading strong scents, sometimes emitting droplets of a clear fluid, apex acute or obtuse, wall thin or massive, inside a narrow canal or a large cavity.

Female Flowers: Female flowers consisting of one pistil; ovary sessile or shortly stipitate, globose, subglobose, depressed or ovate, rounded or angulate in cross-section, 1-, 2-, 3-, or 4-locular, one ovule per locule, basifixed, or rarely axillary circa halfway up the ovary; style present or absent, cylindric or rarely slightly conic or obconic, clearly separated from the ovary or less so, equalling or shorter or longer than ovary, sometimes with apical projections extending beyond the stigma; stigma indistinct or large, terminal or rarely subterminal, globose, hemispheric, concave or flattened, entire or variously lobed, surface spongy, papillate, scabrate or echinate, during anthesis covered with a sticky fluid.

Male Flowers: Male flowers consisting of (1-) 3 to 6 (-8) stamens; stamens depressed or elongate; filaments present or nearly absent, massive or rarely thin, separate or partly or entirely fused within one flower.

Anthers: Anthers short or elongate, rarely subglobose or globose, truncate, rarely rounded, connective indistinct or massive, sometimes with one or more projections, pores apical, rarely lateral or subterminal, rounded, reniform or elongate; staminodes of sterile zone shield-like, globose or hairlike, those on the appendix shield-like, hairlike, rounded or conic warts, echinae, sulci or papillae.

Pollen: Pollen globose or elliptic, exine rarely absent, psilate, striate, foveolate, etc.

Infructescence: Infructescence usually long-peduncled, rarely short-peduncled; fruiting part globose or elongate; berries globose or elongate, red, orange-red, white, white-and-yellow, blue.

Seed: Seeds globose, subglobose, ovate, elliptic, usually with a distinct raphe.

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