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Key to Acanthaceae

Acanthaceae

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1 Plant a tree, with opposite leathery leaves; [of FL, s. MS, s. LA southward]
1 Plant an herb or vine, with various leaf arrangements.
  2 Leaves in a basal rosette (sometimes with smaller leaves on a scape).
    3 Leaves glabrate, to 22 cm long and 8 cm wide; corolla 0.8-1.3 cm long; capsule 8-10 mm long; stamens 2; [of moist to wet swamps]; [subfamily Nelsonioideae]
    3 Leaves pubescent, to 10 cm long and 3 cm wide; corolla 1.8-4 cm long; capsule 9-18 mm long; stamens 4; [of dry upland pinelands].
      4 Leaves 2-10 cm long, 1-3 cm wide; corolla 3-4 cm long; calyx lobes 15-30 mm long; capsule 12-18 mm long
      4 Leaves 1.5-2.5 cm long, 0.7-0.8 cm wide; corolla ca. 2 cm long; calyx lobes 6-9 mm long; capsule ca. 10 mm long
  2 Leaves cauline.
        5 Fertile stamens 2; corolla distinctly 2-lipped or zygomorphic (except salverform in Pseuderanthemum and with 4 nearly equal lobes in Yeatesia).
          6 Corolla distinctly 2-lipped or 4-lobed.
             7 Leaves speckled or mottled with pink or white
             7 Leaves not speckled with pink or white.
               8 Flowers with 2 staminodes present; corolla tubular; anther sacs parallel, equal; [uncommon non-native, s. AL and FL]
               8 Flowers lacking staminodes; corolla not tubular; anther sacs unequal; [widespread native and non-natives]
                 9 Texas only; {additional characters}
                   10 Stout shrubs to 3 m tall; corolla bright red to orange, 30-55 mm long
                   10 Suffrutescent herbs to 0.5 m tall; corolla white to light purple, 5.0-9.5 mm long
                 9 yyyy; [widespread, including TX].
                     11 Bracts and bractlets inconspicuous, 2-5 mm long, linear or triangular; stem subterete or obscurely 4-angled
                     11 Bracts and/or bractlets subtending the flowers conspicuous, 5-15 mm long, obovate; stem terete or 6-angled.
                       12 Stem six-angled in cross-section; corolla conspicuously 2-lipped
        5 Fertile stamens 4; corolla not distinctly 2-lipped, the corolla lobes of nearly equal size (except distinctly 2-lipped in Hygrophila).
                          13 Corolla distinctly 2-lipped (bilabitate, with a distinct upper and lower lip).
                            14 Outer sepals aristulate or with spinose margins (except B. repens, which has a reddish corolla and grows trailing)
                          13 Corolla not distinctly 2-lipped, the corolla lobes of nearly equal size.
                              15 Plant an herbaceous vine; leaves cordate-hastate at the base; flowers yellow to orange, usually with a dark purple “eye”
                              15 Plant an herb; leaves cuneate to rounded at the base; flowers white to various shades of blue or pink.

Key C7: rooted aquatics with simple, cauline, opposite or whorled leaves

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1 Leaves whorled, most nodes with 3 or more leaves.
  2 Leaves strongly toothed to pectinate
  2 Leaves entire or finely toothed.
    3 Leaves tipped by a callus (visible at 10× magnification); leaf margins entire; flowers many, grouped in a terminal involucrate head; [Eudicots]
    3 Leaves not callus-tipped; leaf margins finely toothed or at least with conical protrusions remaining from the disintegration of better-developed deciduous teeth; flowers solitary on elongate, flexuous stalks; [Monocots]
1 Leaves opposite, no nodes with 3 or more leaves.
      4 Cauline leaves in 2-many nodes.
        5 Leaves in 2-3 pairs, appearing verticillate; plants of marine waters; [of FL, MS, LA and southward]
        5 Leaves along stem at 2-many nodes; plants of fresh to brackish waters; [collectively widespread].
             7 Leaf margins (or at least leaf sheaths) serrate or minutely spiny; fruits sessile, entire; leaves 5-15× as long as wide
             7 Leaf margins (including sheaths) entire; fruit stalked, dentate on one side; leaves >20× as long as wide
               8 Leaves 1-12 cm long; flowers borne in axillary or terminal spikes or clusters
               8 Leaves 0.5-3 (-5) cm long; flowers solitary, axillary.
                 9 Carpels 4-5, separate; fruit an aggregate of follicles; leaves succulent
                 9 Carpels 2-5, fused; fruit capsular (variously dehiscent); leaves thin in texture or somewhat succulent (e.g. Bacopa in PLANTAGINACEAE).
                   10 Leaves dimorphic, the terminal leaves usually spatulate (strongly expanded towards the apex); corolla absent; stamen 1
                   10 Leaves monomorphic, obovate, oblanceolate, or parallel-margined; corolla present (absent in Didiplis in LYTHRACEAE); stamens 2-6.
                     11 Flower radially symmetrical, 3-4-merous; petals absent or separate
                       12 Stems lacking ridges running down from leaf bases
                       12 Stems with ridges running down from leaf bases
                     11 Flower bilaterally symmetrical, 4-5-merous; petals present, fused at least basally, forming a tube.