Araceae

• See list of 5 genera in 1a
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  1a. Plants thalloid, not differentiated into stems and leaves, 0.5–15 mm long, floating on or near the surface of water [Figs. 61,62]
  • See list of 2 genera in 2a
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    2a. Thalli without roots, lacking veins; flowers without a spathe; thallus buds produced from a single, terminal pouch or cavity at base of parent thallus
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      Wolffia

      3a. Thalli ovoid to globose or boat-shaped (i.e., flattened above and rounded below), without air spaces [Figs. 61,62]; flower produced from cavity along median line of 
upper thallus surface
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      Wolffiella

      3b. Thalli flat, elongate, narrowly sabre-shaped, with air spaces [Fig. 63]; flower produced from a cavity at the side of the median line of upper thallus surface
  • See list of 3 genera in 2b
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    2b. Thalli with roots, with 1 or more veins; flowers with a small, membranous spathe; thallus buds from 2 lateral pouches at parent thallus base
    • See list of 2 genera in 4a
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      4a. Each thallus with 2–21 roots, the lower surface red-purple, the upper surface with (3–) 5–16 (–21) veins
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        Spirodela

        5a. Thalli with (5–) 7–16 (–21) veins, 1–1.5 times as long as wide; roots numbering 7–21 per thallus, only 1 or 2 perforating the small, membranous scale at thallus base
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        Landoltia

        5b. Thalli with (3–) 5–7 veins, 1.5–2 times as long as wide; roots numbering 2–7 (–12), all perforating the small, membranous scale at thallus base
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      Lemna

      4b. Each thallus with a single root, the lower surface green (purple in L. turionifera), 
the upper surface with 1–3 (–5) nerves
• See list of 5 genera in 1b
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  1b. Plants not thalloid, differentiated into stems and leaves, much larger, terrestrial or emergent aquatics
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    Arisaema

    6a. Leaves compound, with 3–13 (–21) leaflets; flowers concealing only the basal portion 
of the axis of the spadix
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    6b. Leaves simple; flowers concealing most or all of the axis of the spadix
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      Orontium

      7a. Spathe absent; adaxial surface of leaf blades dark blue-green with a conspicuous velvety sheen created by a waxy epidermal layer
    • See list of 3 genera in 7b
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      7b. Spathe present; leaf blades otherwise
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        Calla

        8a. Spathe adaxially white, open, nearly flat, not concealing the spadix; fruit a cluster of distinct, red berries; plants from a long, creeping rhizome
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        8b. Spathe green, or green to brown and marked with purple, convolute, concealing the basal portion of the spadix; fruit a cluster of green to brown berries or mature carpels submerged in the fleshy spadix; plants from erect rhizomes or fibrous roots
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          Symplocarpus

          9a. Mature leaf blades rounded or cordate at the base, lacking a prominent 
vein that extends into the short, basal lobes (when present); spadix subglobose; flowers with 4 tepals; fruit of mature carpels submerged in the fleshy spadix; plants malodorous
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          Peltandra

          9b. Leaf blades sagittate to hastate, with pronounced basal lobes and a conspicuous vein extending into each lobe; spadix elongate; flowers without perianth; fruit a green to brown berry; plants not malodorous

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 Show photos of:   Each photo represents one genus in this family.