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Key to Euphorbiaceae

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1 Plant a twining vine (herbaceous or woody at base) to 5 m long; stem with stinging hairs; [subfamily Acalyphoideae]
1 Plant not twining; instead a tree, shrub, or herb (or weakly twining in some Tragia, but then less than 1 m long); stem either armed with stinging hairs, or not armed.
  2 Shrub or tree (woody).
    3 Leaves entire.
      4 Hairs of vegetative parts of the plant (especially the leaf undersurface) present and either 2-branched, stellate, or modified into lepidote scales (use 10× or more magnification); [subfamily Crotonoideae].
      4 Hairs of vegetative parts of the plant (especially the leaf undersurface) absent or unbranched (simple) (use 10× or more magnification).
        5 Flowers enclosed in a cyathium; plant with copious white latex; [subfamily Euphorbioideae]
        5 Flowers not enclosed in a cyathium; plant either with or without white latex (the sap clear to whitish or absent).
          6 Leaf blades 1-1.5× as long as wide; [exotic trees].
             7 Petioles 9-19 cm long; [subfamily Crotonoideae]
             7 Petioles 2-6 cm long; [subfamily Acalyphoideae]
          6 Leaf blades 1.5-5× as long as wide; native or exotic shrubs or, rarely, small trees.
               8 Sepals absent; latex watery; leaf margins obscurely gland-toothed; [subtropical hardwood hammocks of far southern FL]; [subfamily Euphorbioideae]
               8 Sepals present; latex absent or watery; leaf margins entire; [various habitats and collectively widespread].
                 9 Latex colorless to whitish, watery; capsules ovoid or ellipsoidal; [FL peninsula and s. TX]; [subfamily Crotonoideae]
                 9 Latex absent; capsules subglobose; [collectively widespread in our region].
                   10 Leaves palmately veined at base; inflorescence bracts not subtended by glands; [s. TX and southwards]; [subfamily Acalyphoideae]
                   10 Leaves pinnately veined; inflorescence bracts with 2 subtending glands; [widespread from NC to FL west to AR and e. TX]; [subfamily Euphorbioideae]
                     11 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                     11 Plants either glabrous or hairy with simple or stellate trichomes.
                          13 Petals present; inflorescence a cyme or dichasium; leaf lobe margins entire or serrate; [subfamily Crotonoideae].
                       12 Leaves unlobed, margins crenate (obscurely crenate in Hippomane and Adelia) or serrate.
                              15 Leaves 8-20× as long as wide (lanceolate to linear); petiole with 0 or 2 glands at summit.
                                16 Petiole lacking 2 glands at summit; [native, widespread in our area]
                              15 Leaves 1-3× as long as wide (elliptic, ovate, or obovate); petiole with 0 or 1 gland at summit.
                                  17 Lower leaf surface densely stellate-pubescent; leaf strongly toothed; [TX]; [subfamily Acalyphoideae]
                                    18 Leaf blades obovate, 2-3× as long as wide, with a rounded apex; petiole < 0.2 cm long; fruit a capsule, 1.0-1.3 cm in diameter; [TX]; [subfamily Acalyphoideae]
                                    18 Leaf blades ovate, 1-2× as long as wide, with an acute apex; petiole 1-6 cm long; fruit a drupe, 1.5-2.5 cm in diameter; [FL]; [subfamily Euphorbioideae]
  2 Herb.
                                         20 Plants with a prominent, round woody shallow subterranean caudex to 13.5 cm in diameter; [subfamily Crotonoideae]
                                           21 Leaves cordate to truncate or rounded at base; plant glabrous, stellate, or with conspicuous stinging trichomes; stamens 8-15; [subfamily Crotonoideae].
                                                    25 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                                                        27 Flowers in terminal spikes; stout perennial with several to many stems arising from a subterranean crown; [subfamily Euphorbioideae]
                                                        27 Flowers strictly axillary or both axillary and terminal, in small clusters, racemes, or spikes; finer perennial or annual, not typically with > 1 stem arising from a subterranean crown; [subfamily Acalyphoideae]
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