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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]
    3 Leaves crenate, serrate, and/or palmately lobed.
                     11 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                     11 Plants either glabrous or hairy with simple or stellate trichomes.
                       12 Leaves palmately lobed, margins entire or serrate.
                          13 Petals absent; inflorescence a panicle; leaf lobe margins serrate; [subfamily Acalyphoideae]
                          13 Petals present; inflorescence a cyme or dichasium; leaf lobe margins entire or serrate; [subfamily Crotonoideae].
                            14 Shrub or tree; inflorescence a fascicle or cyme; capsule ellipsoidal
                            14 Tree; inflorescence a dichasium; capsule subglobose
                       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 with 2 glands at summit; [exotic, on ballast in Pensacola, FL]
                                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]
                                  17 Lower leaf surface glabrous; leaf entire, obscurely crenate, or serrulate.
                                    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.
                                       19 Leaves palmately deeply divided into 3-many lobes.
image of plant
Show caption*© Alexis López Hernández, some rights reserved (CC BY), uploaded by Alexis López Hernández
                                         20 Plants with a prominent, round woody shallow subterranean caudex to 13.5 cm in diameter; [subfamily Crotonoideae]
                                         20 Plants lacking a prominent subterranean caudex.
                                           21 Leaves peltate; plant glabrous; stamens 100-1000; [subfamily Acalyphoideae]
                                           21 Leaves cordate to truncate or rounded at base; plant glabrous, stellate, or with conspicuous stinging trichomes; stamens 8-15; [subfamily Crotonoideae].
                                             22 Plant with stinging trichomes; stamens connate
                                             22 Plant lacking stinging trichomes; stamens separate.
                                               23 Latex clear; pubescence stellate
                                               23 Latex white; pubescence absent or of non-stellate hairs
                                       19 Leaves generally not lobed, entire or serrate (rarely pinnately lobed in Euphorbia).
                                                 24 Plants hairy with stellate hairs and/or scales; [subfamily Crotonoideae]
                                                 24 Plants glabrous or hairy with simple or 2-branched hairs.
                                                    25 Plants hairy with 2-branched hairs (malpighiaceous trichomes); [subfamily Acalyphoideae]
                                                    25 Plants glabrous or hairy with simple hairs.
                                                      26 Flowers enclosed in a cyathium; plant (fresh) with copious white latex; [subfamily Euphorbioideae]
                                                      26 Flowers not enclosed in a cyathium; plant (fresh) with or without white latex.
                                                        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]
                                                          28 Leaves opposite; carpels 2
                                                          28 Leaves alternate; carpels 3 (sometimes fewer by abortion).
                                                            29 Pistillate flowers subtended by a conspicuous leafy bract
                                                            29 Pistillate flowers lacking a leafy bract.
                                                              30 Plant lacking stinging trichomes; styles deeply multifid; [wetland habitats]
                                                              30 Plant with stinging trichomes; styles undivided; [upland habitats]

Key to Stillingia

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1 Staminate flowers 1 at each node of the inflorescence; caruncle of the seed minute; [s. and c. TX, barely in our area]
1 Staminate flowers in 3-15-flowered cymules at each node of the inflorescence; caruncle of the seed either minute, or white, broadly crescent-shaped, and > 1 mm wide; [collectively fairly widespread in our area].
  2 Stems woody, solitary at base, from a taproot; (aerial) stems freely sympodially branched in the upper half to third of the plant, the whole plant appearing candelabra-like with age; the aerial branch system perennially developing by extension growth; leaves linear to lanceolate or narrowly elliptic, widest at middle or towards the base, clustered toward the branch tips; caruncle of the seed (typically) minute, exposing an inverted U-shaped hilar scar; [of pineland ponds and other aquatic habitats where the soil is inundated for at least four months of the year]
  2 Stems herbaceous, several from the crown of a woody rhizome; aerial stems not or little (sympodially) branched; aerial branches persisting for only a single growing season; leaves linear, elliptic, oblanceolate, or narrowly obovate, widest near the midpoint or towards the apex, stems appearing evenly leafy; caruncle of the seed white, broadly crescent-shaped, > 1 mm wide, largely concealing the hilar scar; [mostly of dry habitats, or mesic to wet pinelands that are only sporadically inundated].
    3 Leaf teeth with prominently blackened tips; leaf blades of mid to upper stem 3-6 (-10) mm wide; [rocky calcareous soils in OK and TX]
    3 Leaf teeth with tips not strongly contrasted in color from that of the mature leaf blade; leaf blades of mid to upper stem 2-30 mm wide; [widespread in our area].
      4 Leaf blades > 9 mm wide at widest point, L/W ratio (1.3-) 2.5-5.7 (-8.1), frequently broadest towards the tip; median bract subtending the pistillate cymule typically elliptic and the apex not clearly differentiated in shape; [widespread in our region, from se. VA to s. FL, westwards to OK, and TX]
      4 Leaf blades < 9 mm wide at widest point (typically 3.4-6.2 mm wide), L/W ratio (7-) 8.2-15.6 (-22), typically broadest near the middle; median bract subtending the pistillate cymule with a caudate-acuminate apex; [endemic in c. & s. FL]