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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; [alien 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 alien 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; [alien, 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.
............ ............ ............ ..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 with copious white latex; [subfamily Euphorbioideae]
............ ............ ............ ............ ..26 Flowers not enclosed in a cyathium; plant 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, oblancolate, 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]