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The families of flowering plants

L. Watson and M.J. Dallwitz

Araceae Juss.

Including Calladeae (Calladiaceae) Salisb., Callaceae Reichenbach, Cryptocorynaceae J.G. Agardh, Dracontiaceae P.A. Salisbury, Orontiaceae Bartl., Pistiaceae Dum., Pistiaceae C.A Agardh (p.p.); excluding Lemnaceae.

Habit and leaf form. Shrubs, or herbs, or ‘arborescent’; laticiferous, or with coloured juice, or non-laticiferous, without coloured juice. ‘Normal’ plants. Perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves; often cormous, or rhizomatous, or tuberous. Self supporting, or epiphytic, or climbing (some very large); when climbing stem twiners, or root climbers, or scrambling. Hydrophytic, or helophytic, or mesophytic; when hydrophytic rooted, or free floating (Pistia). Leaves when hydrophytic, submerged, or emergent. Heterophyllous (often entire/lobed compound), or not heterophyllous. Leaves small to very large; alternate; spiral, or distichous; petiolate (appearing conventionally ‘petiolate’ when the sheath shed), or sessile (Pistia only); sheathing (the sheath membranous, sometimes deciduous). Leaf sheaths with free margins. Leaves ‘normally orientated’ (Acorus being excluded); simple, or compound. Lamina pinnately veined, or palmately veined, or parallel-veined; cross-venulate, or without cross-venules; often cordate, or hastate, or sagittate. Leaves ligulate, or eligulate. Axillary scales present, or absent. Leaf development not ‘graminaceous’; leaves often becoming compound by necrosis.

General anatomy. Plants with laticifers (articulated, branched or not), or without laticifers (e.g. some Pothoideae, Pistia). Plants without silica bodies.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present (usually randomly orientated); paracytic, or tetracytic, or cyclocytic, or anomocytic (etc.). Guard-cells not ‘grass type’. The mesophyll without etherial oil cells; containing mucilage cells (with raphides), or not containing mucilage cells; containing crystals. The crystals raphides and druses. Foliar vessels absent. Minor leaf veins without phloem transfer cells (5 genera).

Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.

Root anatomy. Roots with velamen (rarely), or without velamen. Root xylem with vessels; vessel end-walls scalariform.

Reproductive type, pollination. Plants hermaphrodite, or monoecious (then the males above), or andromonoecious, or gynomonoecious, or gynodioecious, or polygamomonoecious. Pollination anemophilous (rarely), or entomophilous; mechanism conspicuously specialized (involving protogyny, combined with the trapping of insects in the spathe, and their subsequent release), or unspecialized.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes (very rarely shortly pedicellate — Pedicellarum). The ultimate inflorescence units seemingly racemose. Inflorescences scapiflorous (usually, more or less), or not scapiflorous; consisting of specialised spikes (‘spadices’) with spirals or rarely whorls of flowers, variously pedunculate, sometimes tipped by a naked ‘appendix’; usually conspicuously, often spectacularly spatheate, or espatheate (in that there may be no true spathe in Gymnostachys, Orontium). Flowers ebracteate; ebracteolate; small (numerous); (these or the spadix) often fragrant, or malodorous; regular to very irregular; when irregular, asymmetric; 1–3 merous; cyclic. Perigone tube present (Spathiphyllum), or absent (usually).

Perianth of ‘tepals’, or absent; 0, or 4, or 6, or 8 (rarely 12); free (usually), or joined; when present, 2 whorled (3+3 or 2+2); isomerous; when present, sepaloid; similar in the two whorls (small, inconspicuous, often thick).

Androecium 1 (e.g. Cryptocoryne), or 4, or 6, or 8(–12). Androecial members free of the perianth; free of one another, or coherent; 1 whorled, or 2 whorled (commonly 3+3 or 2+2). Androecium exclusively of fertile stamens. Stamens 1–4, or 6, or 8–12; reduced in number relative to the adjacent perianth to isomerous with the perianth to triplostemonous; filantherous. Anthers basifixed; non-versatile; dehiscing via pores, or dehiscing via short slits, or dehiscing via longitudinal slits, or dehiscing transversely; extrorse; bisporangiate, or tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Anther epidermis persistent. Microsporogenesis successive. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall of the ‘monocot’ type. Tapetum amoeboid. Pollen shed in aggregates (occasionally), or shed as single grains; when in aggregates, in tetrads (e.g. Caladium, Xanthosma). Pollen grains aperturate, or nonaperturate; 1 aperturate, or 2–9 aperturate (?); when aperturate, sulcate, or sulculate, or foraminate; 2-celled (10 genera), or 3-celled (7 genera).

Gynoecium (1–)3(–8) carpelled. The pistil 1 celled, or (1–)3(–8) celled. Gynoecium monomerous, or syncarpous; of one carpel, or synstylovarious to eu-syncarpous (?); superior. Carpel non-stylate; apically stigmatic; (when monomerous,) 1–5 ovuled (?). Placentation apical, or marginal, or basal (?). Ovary when syncarpous, (1–)3(–8) locular. The ‘odd’ carpel when trilocular, posterior. Gynoecium shortly non-stylate, or stylate. Styles 1; apical. Stigmas wet type, or dry type; non-papillate; Group II type. Placentation when syncarpous/unilocular, parietal, or basal, or apical; when plurilocular, axile. Ovules in the single cavity when unilocular, 1–15(–50) (?); 1–15(–100) per locule (?); pendulous, or horizontal, or ascending; orthotropous, or hemianatropous (rarely), or anatropous; bitegmic; tenuinucellate (e.g. Pistia), or crassinucellate (weakly), or pseudocrassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; initially 3; proliferating (to a limited extent, e.g. Lysichiton), or not proliferating (usually); ephemeral (usually), or persistent. Synergids pear-shaped. Hypostase present, or absent. Endosperm formation helobial (though ostensibly cellular, and long described as such). Endosperm haustoria present; chalazal. Embryogeny caryophyllad (usually), or onagrad (e.g. Pistia).

Fruit fleshy (usually), or non-fleshy; an aggregate, or not an aggregate. The fruiting carpel when monomerous, indehiscent; drupaceous, or baccate, or nucular. Fruit indehiscent (usually), or dehiscent; a capsule to capsular-indehiscent (occasionally), or a berry, or a drupe, or a nut (occasionally). Capsules when present, splitting irregularly. Gynoecia of adjoining flowers combining to form a multiple fruit (usually), or not forming a multiple fruit. The multiple fruits coalescing (sometimes), or not coalescing. Dispersal unit the fruit, or the inflorescence (the spadix sometimes forming a syncarp). Seeds endospermic, or non-endospermic. Endosperm when present, oily (and starchy). Perisperm absent. Seeds with starch. Cotyledons 1. Embryo chlorophyllous (6/6), or achlorophyllous (Arisaema amurense); straight (linear). Testa without phytomelan; membranous, leathery or crustaceous, but not black?.

Seedling. Hypocotyl internode present (commonly, short to fairly long, sometimes developing into a storage organ, e.g. Arisaema), or absent (e.g. Pistia). Seedling collar not conspicuous. Cotyledon hyperphyll compact; assimilatory, or non-assimilatory (functioning entirely as a haustorium, or as a storage cum assimilatory organ, or combining all these functions). Coleoptile absent. Seedling when the seed non-endospermic, non-macropodous. Seedling cataphylls present or absent. First leaf dorsiventral. Primary root ephemeral (and sometimes absent alogether).

Physiology, phytochemistry. C3. C3 physiology recorded directly in Colocasia, Pistia, Pothos. Anatomy non-C4 type (Alocasia, Colocasia, Peltandra, Pistia, Pothos). Accumulated starch other than exclusively ‘pteridophyte type’. Cyanogenic, or not cyanogenic. Cynogenic constituents tyrosine-derived. Alkaloids present (commonly), or absent. Saponins/sapogenins present (in some genera), or absent (?). Proanthocyanidins present (commonly, sometimes very abundantly), or absent; when present, cyanidin. Flavonols present, or absent; when present, kaempferol, or quercetin, or kaempferol and quercetin. Ellagic acid absent. Sieve-tube plastids P-type; type II.

Geography, cytology. Sub-tropical, tropical, temperate (relatively few). Widespread.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Ariflorae; Arales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales.

Species 2000. Genera 106; Aglaodorum, Aglaonema, Alloschemone, Alocasia, Ambrosina, Amorphophallus, Amydrium, Anadendrum, Anaphyllopsis, Anaphyllum, Anchomanes, Anthurium, Anubias, Aridarum, Ariopsis, Arisaema, Arisarum, Arophyton, Arum, Asterostigma, Biarum, Bognera, Bucephalandra, Caladium, Calla, Callopsis, Carlephyton, Cercestis, Chlorospatha, Colletogyne, Colocasia, Cryptocoryne, Culcasia, Cyrtosperma, Dieffenbachia, Dracontioides, Dracontium, Dracunculus, Eminium, Epipremnum, Filarum, Furtodoa, Gearum, Gonatanthus, Gonatopus, Gorgonidium, Gymnostachys, Hapaline, Helicodiceros, Heteroaridarum, Heteropsis, Holochlamys, Homalomena, Hottarum, Jasarum, Lagenandra, Lasia, Lasimorpha, Lysichiton, Mangonia, Monstera, Montrichardia, Nephthytis, Orontium, Pedicellarum, Peltandra, Philodendron, Phymatarum, Pinellia, Piptospatha, Pistia, Podolasia, Pothoidium, Pothos, Protarum, Pseudodracontium, Pseudohydrosme, Pycnospatha, Remusatia, Raphidophora, Rhodospatha, Sauromatum, Scaphispatha, Schismatoglottis, Scindapsus, Spathantheum, Spathicarpa, Spathiphyllum, Stenospermation, Steudnera, Stylochaeton, Symplocarpus, Synandrospadix, Syngonium, Taccarum, Theriophonum, Typhonium, Typhonodorum, Ulearum, Urospatha, Urospathella, Xanthosoma, Zamiculcas, Zantedeschia, Zomicarpa, Zomicarpella.

General remarks. See the description of Lemnaceae for a comment on the inappropriateness of incuding them here.

Economic uses, etc. The family furnishes numerous horticultural ornamentals, especially for indoors, and a few are grown for food — e.g. Colocasia for taro, Monstera for its ‘fruits’ (‘Mexican breadfruit’).


Look through the naked bramble and black thorn
And see the arum show its vivid green
Glossy and rich and some ink spotted like the morn
Ing sky with clouds — in sweetest neuks I’ve been
And seen the arum sprout its happy green
(John Clare c.1845, ‘Look Through the Naked Bramble and Black Thorn’ — Arum maculatum)

O Cuckoo-pint! toll me the purple clapper
That hangs in your clear green bell!
(Jean Ingelow, ‘Seven Time One’ - Arum maculatum)

Illustrations. • Le Maout and Decaisne: Arum maculatum. • Arum maculatum (J.E. Sowerby, 1861). • Le Maout and Decaisne: Colocasia, Calla, Tornelia (= Monstera). • Le Maout and Decaisne: Ambrosina, Cyrtosperma, Gymnostachys, Symplocarpus. • Amorphophallus abyssinicus, as Hydrosme grata: Thonner. • Le Maout and Decaisne: Pistia, Orontium, Richardia (= Zantedeschia). • Cryptocoryne griffithii: Bot. Mag. 126 (1900). • Gymnostachys anceps: Schott, Genera Aroidearum (1858). • Homalomena wallisii (as Homalonema): Bot. Mag. 107 (1881). • Homalomena rubescens: Schott, Genera Aroidearum (1858). • Philodendron crassinervum: Bot. Reg. 1958, 1837. • Pinellia integrifolia: Hook. Ic. Pl. 19 (1889). • Pothos scandens: Bot. Reg. 1337, 1830. • Protarum sechellarum: Hook. Ic. Pl. 28 (1902). • Pseudodracontium lacourii: Bot. Mag. 109 (1883). • Raphidophora decursiva: Bot. Mag. 119 (1893). • Schismatoglottis asperata (as S. crispata): Bot. Mag. 107 (1881). • Symplocarpus foetidus: Schott, Genera Aroidearum (1858).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.