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Key to Eichhornia

Pontederiaceae

Eichhornia

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  2 Plants rooted; stems elongate, with leaves spaced and alternate; petioles not inflated
  2 Plants floating (or stranded by dropping water levels); stems short, with leaves in a rosette with very short internodes; petioles inflated
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Key to Pontederiaceae

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© Scott Ward
(c) Sorrie, Bruce A. - CC-BY
1 Inflorescence with > 30 flowers; fruit 1-seeded, indehiscent, a utricle; seeds smooth; leaves lanceolate to ovate, 1.5-10× as long as wide, the base cordate, truncate, or cuneate
1 Inflorescence with < 30 flowers; fruit 10-200-seeded, a capsule; seeds longitudinally winged; leaves either reniform or ovate, 0.5-1.5× as long as wide, the base cordate or rounded, or narrowly linear, 20-50× as long as wide, the base attenuate.
(c) Ward, Scott G
(c) Bradley, Keith
  2 Leaves membranous; petioles never expanded into air-filled floats; perianth lobes linear to oblanceolate, 0.4-2.0 cm long; stamens 3
  2 Leaves coriaceous; petioles either expanded into air-filled floats or not; perianth lobes ovate, 1.3-3.7 cm long; stamens 6.
(c) Obbard, Darren - CC-BY
    3 Herbs procumbent-emergent, stems elongate; sessile leaves late deciduous, rarely persistent in mature plants, petiolate leaves distichously-alternate, evenly distributed along the stem; perianth funnelform (the corolla limb expanding gradually from the widening corolla tube); style glabrous
    3 Herbs erect emergent or free-floating, stems inconspicuous; sessile leaves early deciduous, petiolate leaves spirally-alternate, congested at the apex of the stem; perianth salverform (the corolla limb spreading abruptly at a nearly right angle to the straight corolla tube); style glandular-pubescent.
(c) Costa, Macelo - CC-BY
      4 Erect emergents, never with inflated petioles; herbs never producing stolons; ligule truncate; inflorescences erect at post-anthesis, emerging from an inflated leaf-sheath, basal bract flat; flowers ca. 2-3 cm in diameter, perianth tightly enclosing the developing fruit; seeds subglobose to broadly oblong
(c) Smith, Jake - CC-BY-NC, permission granted to NCBG
      4 Free-floating aquatics, with inflated petioles; herbs stoloniferous; ligule flabellate, petioles generally inflated; inflorescences deflexed post-anthesis and in fruit, emerging from a non-inflated leaf-sheath, basal bract tubular; flowers ca. 4-6 cm in diameter, perianth loosely enclosing the developing fruit; seeds oblong
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Key C6: rooted aquatics with simple, cauline, alternate leaves

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1 Leaves broad, < 4× as long as wide.
  2 Floating leaves peltate
  2 Floating or emersed leaves cuneate to rounded at base.
    3 Floating leaves diamond-shaped, prominently serrate
    3 Floating or emersed leaves elliptic or suborbicular.
      4 Leaves emersed, lanceolate to narrowly elliptic; flowers 5-merous; [Eudicots]
      4 Leaves emersed or floating, suborbicular or elliptic (if emersed, then suborbicular; flowers 3-merous; [Monocots].
1 Leaves narrow, > 4× as long as wide.
          6 Leaves 0.3-1.4 cm long, very numerous and tightly spaced
          6 Leaves 2-35 cm long, fewer and scattered along the stem.
             7 Leaf divided into a sheath and blade, with a ligule 0.5-8 mm long at the juncture; inflorescence a spike, raceme, or panicle of spikelets
             7 Leaf not divided into a sheath and blade, but if basally sheathing lacking a ligule (though sometimes with 1-2 conspicuous stipules); inflorescence various, but not as above.
               8 Leaves terete, to 35 cm long, 0.3-2 mm wide; plants of marine habitats, growing submersed in salt water; [FL and the Gulf Coast of AL, MS, and LA]
               8 Leaves flat or terete, to 200 cm long; plants of fresh or brackish waters (if of marine waters, Zostera, the leaves obviously flat, 1.5-6 mm wide); [collectively widespread].
                 9 Leaves filiform, terete or nearly so; stipules present, adnate to the leaf base and forming a sheath around the stem > 10 mm long.
                   10 Stipule free at its tip, the sheathing portion not appearing inflated; flowers > 2, in an interrupted spike
                   10 Stipule adnate its entire length to the leaf base, appearing inflated; flowers usually 2, on a flexous, elongate peduncle
                 9 Leaves flat; stipules absent, or if present, either free or adnate to the leaf base and forming a sheath for < 10 mm.
                     11 Leaves with a midvein; perianth parts 0 or 4, variously colored (not yellow).
                       12 Plants pubescent (at least on the upper stem); leaves pinnately veined; [Eudicots]
                       12 Plants nearly or entirely glabrous; leaves with parallel venation; [Monocots].
                          13 Inflorescences of flowers solitary or in 2-4 flowered racemes, axillary; spathe lacking; perianth conspicuous with 3 pink to purple petals
                            14 Inflorescence a cylindrical, interrupted spike, lacking a spathe; leaves either parallel-margined or variously with a narrow blade differentiated from a petiole; [fresh to brackish waters]
                            14 Inflorescence either a flattened spike sheathed by a spathe-like bract, or solitary; leaves parallel-margined, to 20 dm long; [saline (marine) to brackish waters].
                              15 Leaves with a notched or tricuspidate apex; flowers solitary; [e. NC southward]
                              15 Leaves with a rounded apex; flowers in a flattened spike sheathed by a spathe-like bract; [e. NC northward]