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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 Leaves usually conspicuously variegated; [waif, se. FL]
               8 Leaves not variegated; [widespread native and non-natives]
                 9 Sepals absent; latex watery; leaf margins obscurely gland-toothed; [subtropical hardwood hammocks of far southern FL]; [subfamily Euphorbioideae]
                 9 Sepals present; latex absent or watery; leaf margins entire; [various habitats and collectively widespread].
                   10 Latex colorless to whitish, watery; capsules ovoid or ellipsoidal; [FL peninsula and s. TX]; [subfamily Crotonoideae]
                   10 Latex absent; capsules subglobose; [collectively widespread in our region].
                     11 Leaves palmately veined at base; inflorescence bracts not subtended by glands; [s. TX and southwards]; [subfamily Acalyphoideae]
                     11 Leaves pinnately veined; inflorescence bracts with 2 subtending glands; [widespread from NC to FL west to AR and e. TX]; [subfamily Euphorbioideae]
    3 Leaves crenate, serrate, and/or palmately lobed.
                       12 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                       12 Plants either glabrous or hairy with simple or stellate trichomes.
                          13 Leaves palmately lobed, margins entire, crenate, or serrate (Mallotus often with at least a few obscurely lobed leaves).
                            14 Petals absent; inflorescence a panicle; leaf lobe margins crenate to serrate; [subfamily Acalyphoideae].
                              15 Plants pubescent, often with a mix of unlobed to obscurely 3-lobed leaves, the lobes not extending deeply and the blades not star-shaped; [waif, FL panhandle]
                              15 Plants glabrous, the leaves conspicuously 7-12 palmately lobed, appearing almost star-shaped; [widespread non-native]
                            14 Petals present; inflorescence a cyme or dichasium; leaf lobe margins entire or serrate; [subfamily Crotonoideae].
                                16 Shrub or tree; inflorescence a fascicle or cyme; capsule ellipsoidal
                                16 Tree; inflorescence a dichasium; capsule subglobose
                          13 Leaves unlobed, margins serrate or crenate (obscurely crenate in Hippomane and Adelia).
                                  17 Leaves 8-20× as long as wide (lanceolate to linear); petiole with 0 or 2 glands at summit.
                                    18 Petiole with 2 glands at summit; [exotic, on ballast in Pensacola, FL]
                                    18 Petiole lacking 2 glands at summit; [native, widespread in our area]
                                  17 Leaves 1-3× as long as wide (elliptic, ovate, or obovate); petiole with 0 or 1 gland at summit.
                                       19 Lower leaf surface densely stellate-pubescent; leaf strongly toothed; [TX]; [subfamily Acalyphoideae]
                                       19 Lower leaf surface glabrous; leaf entire, obscurely crenate, or serrulate.
                                         20 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]
                                         20 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.
                                           21 Leaves palmately deeply divided into 3-many lobes.
                                             22 Plants with a prominent, round woody shallow subterranean caudex to 13.5 cm in diameter; [subfamily Crotonoideae]
                                             22 Plants lacking a prominent subterranean caudex.
                                               23 Leaves peltate; plant glabrous; stamens 100-1000; [subfamily Acalyphoideae]
                                               23 Leaves cordate to truncate or rounded at base; plant glabrous, stellate, or with conspicuous stinging trichomes; stamens 8-15; [subfamily Crotonoideae].
                                                 24 Plant with stinging trichomes; stamens connate
                                                 24 Plant lacking stinging trichomes; stamens separate.
                                                    25 Latex clear; pubescence stellate
                                                    25 Latex white; pubescence absent or of non-stellate hairs
                                           21 Leaves generally not lobed, entire or serrate (rarely pinnately lobed in Euphorbia).
                                                      26 Plants hairy with stellate hairs and/or scales; [subfamily Crotonoideae]
                                                      26 Plants glabrous or hairy with simple or 2-branched hairs.
                                                        27 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                                                        27 Plants glabrous or hairy with simple hairs.
                                                          28 Flowers enclosed in a cyathium; plant (fresh) with copious white latex; [subfamily Euphorbioideae]
                                                          28 Flowers not enclosed in a cyathium; plant (fresh) with or without white latex.
                                                            29 Capsules bearing numerous horned appendages; [uncommon non-native, wc. FL]
                                                            29 Capsules variously shaped, but lacking conspicuous horned appendages; [widespread native and non-natives]
                                                              30 Flowers in terminal spikes; stout perennial with several to many stems arising from a subterranean crown; [subfamily Euphorbioideae]
                                                              30 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]
                                                                 31 Leaves opposite; carpels 2
                                                                 31 Leaves alternate; carpels 3 (sometimes fewer by abortion).
                                                                   32 Pistillate flowers subtended by a conspicuous leafy bract
                                                                   32 Pistillate flowers lacking a leafy bract.
                                                                     33 Plant with stinging trichomes; styles undivided; [upland habitats]