Herbs, perennial, of diverse habit including climbers, floating aquatics, helophytes, pachycaul shrubs, and geophytes. Underground stems absent, or present and then rhizomatous or tuberous; aerial stems variously produced or not, often evergreen; bulbils for vegetative reproduction sometimes produced, e.g., on leaf or on special shoots. Leaves alternate or apparently basal, usually petiolate with sheathing bases, often subtended by prophylls and/or cataphylls; leaf blade various, e.g., linear, simple (base often cordate to sagittate), sometimes peltate or variously compound (e.g., pinnate, radiate, pedate, or decompound), or still more complex and "dracontioid" (elaborate forms of sagittate, hastate, or trisect leaves in which anterior and posterior divisions are highly dissected and subdivided). Inflorescences (sometimes precocious) subtended by membranous prophylls and/or cataphylls, consisting of a spadix subtended by a spathe. Spathe commonly with tubelike base (margins fused or not) persistent or with deciduous blade. Spadix bearing bisexual or unisexual flowers, in latter case plants paradioecious or monoecious (spadix female proximally and male distally), very rarely with morphologically bisexual but functionally unisexual flowers. Bisexual flowers: tepals 0, 4, or 6; stamens 4-6(-22), filaments free, anthers with 2 thecae; ovary usually 3-loculed or more loculed or 1-loculed (pseudomonomerous). Unisexual flowers almost always naked [rare exceptions (only 3 genera, these all from Africa, including cultivated Zamioculcas with tepalate flowers)]: male represented by 1-6 (usually 2-4) free stamens or 2-12 (rarely up to 32) stamens connate into a synandrium overtopped by a common synconnective, anthers often subsessile, usually dehiscing apically by pores or slits (straight or horseshoe-shaped); female flowers consisting of a single ovary (sometimes associated with a sterile staminode), commonly 1-loculed (sometimes with 3 or 4 locules), ovules 1 to many per locule, placentation parietal, axile, basal, or apical. Pollen grains aperturate or inaperturate, exine of various ornamentation. Most genera (Aroideae s.l.) with inaperturate pollen grains without sporopollenin. Sterile (neuter) flowers derived from male or female flowers sometimes present at apex or base of female and/or male zones of spadix. Spadix sometimes with a sterile, terminal appendix. Fruit usually a head of 1- to several-seeded indehiscent separate berries, or dehiscent via shedding stylar plate (Monstereae excluding Amydrium) or syncarpous and apically dehiscent (Cryptocoryne) or syncarpous and indehiscent (Syngonium, cultivated), commonly red, green, white, or yellow, rarely blue.
Herbs, perennial, wetland or terrestrial, occasionally emergent or floating, [often epiphytic or climbing], usually with milky or watery latex, rarely colored. Rhizomes, corms, or stolons present; rhizomes vertical or horizontal, creeping at or near surface, sometimes branched; corms underground, starchy; stolons at or near surface. Stems absent [sometimes aboveground or aerial]. Cataphylls usually present. Leaves rarely solitary, alternate or clustered; petiole rarely absent, with sheathing base; blade simple or compound [occasionally perforate], elliptic to obovate or spatulate, occasionally sagittate-cordate, larger than 1.5 cm; venation parallel or pinnate- or palmate-netted. Inflorescences spadices, each with 3--900 usually tightly grouped, sessile flowers, subtended by spathe; spathe rarely absent, persistent (sometimes only proximally) or deciduous, variously colored; spadix cylindric or ovoid, various parts occasionally naked or with sterile flowers. Flowers bisexual or unisexual, staminate and pistillate usually on same plants or functionally on different plants, staminate flowers distal to pistillate when unisexual; perianth absent or present; stamens 2--12, distinct or connate in synandria; ovaryies 1, 1--3(--many)-locular, sessile or embedded in spadix; styles 1; stigmas hemispheric, capitate, or discoid [sometimes strongly lobed]. Fruits berries, distinct or connate at maturity. Seeds 1--40(--many) per berry.
Perianth present in the bisexual flowers or absent from the unisexual flowers
Stamens hypogynous, 2-4-8, opposite the perianth-segments; anthers opening by pores or slits, free or united
Ovary superior or immersed, 1-many-locular; style various or absent
Ovules parietal, axile, basal or apical
Herbs with watery, bitter or milky juice, with a tuberous or elongated rhizome, rarely woody and climbing
Leaves solitary or few, sometimes appearing after the flowers, mostly radical, when cauline then alternate and distichous or spirally arranged, entire or variously divided, often hastate or sagittate, with a membranous sheath at the base
Flowers small, arranged on a spadix enclosed in a spathe, bisexual or monoecious, the males in the upper part, females below, rarely dioecious
Fruit a berry, or coriaceous and rupturing, 1-many-seeded
Seeds mostly with copious endosperm
Seeds minute to large, variable in shape, with or without endosperm
Herbs, perennial, terrestrial, epiphytic or aquatic, often with milky, viscid or acrid sap; stems lianescent, tuberous, rhizomatous or reduced
Leaves alternate, 1–many, petiolate, usually some reduced to scale leaves (cataphylls) before or among normal leaves or inflorescences; petiole typically with distinct basal sheath, often pulvinate at or near apex; lamina usually broad, membranous to coriaceous, very variable in size and shape, simple or variously lobed, sometimes perforated; main venation pinnate, palmate, pedate or rarely parallel, finer venation reticulate or striate
Inflorescence pedunculate, consisting of fleshy ± cylindric spadix (spike) subtended by bract-like spathe; spathe usually spreading above and convolute below, rarely with margins connate near base, often variously coloured; spadix either uniform with bisexual flowers or monoecious with pistillate flowers at base, staminate flowers above, sterile flowers of varying shape often present at base, middle or apex, apical portion sometimes forming a sterile appendix
Flowers numerous, minute, sessile, bractless, naked or perigoniate, bisexual or unisexual; perigon (perianth) cup-like or composed of 4–9 free or ± connate tepals
Stamens opposite tepals, free or connate into synandria; anthers sessile or with elongated filaments, opening by lateral or apical slits or pores; connective often very thick
Ovary normally superior, 1–many-locular; locules each with 1–many ovules; placentas parietal, axile, basal or apical; stigma sessile or borne on short, conical, rarely attenuate style
Bown, D. 1988. Aroids: Plants of the Arum Family. Portland. Grayum, M. H. 1990. Evolution and phylogeny of the Araceae. Ann. Missouri Bot. Gard. 77: 628--697. Lampe, K. F. and M. A. McCann. 1985. AMA Handbook of Poisonous and Injurious Plants. Chicago. Mayo, S. J., J. Bogner, and P. C. Boyce. 1997. The Genera of Araceae. 1 vol. + laser disc. [London.] Mulligan, G. A. and D. B. Munro. 1990. Poisonous Plants of Canada. Ottawa, Canada. Perkins, K. D. and W. W. Payne. 1978. Guide to the Poisonous and Irritant Plants of Florida. Gainesville, Florida. Plowman, T. 1969. Folk uses of New World aroids. Econ. Bot. 23: 97--122. Thompson, S. A. 1995. Systematics and Biology of the Araceae and Acoraceae of Temperate North America. Ph.D. dissertation. University of Illinois. Add Urbana-Champaign. Wilson, K. A. 1960. The genera of the Arales in the southeastern United States. J. Arnold Arbor. 41: 47--72.