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FNA | Family List | FNA Vol. 12 | Euphorbiaceae

2. Cnidoscolus stimulosus (Michaux) Engelmann & A. Gray, Boston J. Nat. Hist. 5: 234. 1845.
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Tread softly, finger rot Tread softly, finger rot

Jatropha stimulosa Michaux, Fl. Bor.-Amer. 2: 216. 1803; Bivonea stimulosa (Michaux) Rafinesque; Cnidoscolus urens (Linnaeus) Arthur var. stimulosus (Michaux) Govaerts

Plants 10–120 cm. Leaves: stipules 2–3.5 mm, margins entire; petiole 3–8 cm; blade ovate to round in outline, 5–17 × 4–12 cm, deeply lobed, lobes (1/2–)3/4–9/10 blade length, base broadly cordate to truncate, margins usually dentate, rarely entire, teeth and lobe apices acute to obtuse, not aristate. Staminate flowers: calyx salverform, tube 8–11 mm, distally straight or constricted, stinging hairs absent, lobes 7–10 mm; stamens of outer whorl shorter than inner, filaments of outer whorl distinct, of inner whorl connate most of length; staminodes 0. Pistillate flowers: sepals 10–15 mm; stigmas 12–24. Capsules 10–12 mm. Seeds brown, sometimes mottled, 8–9 mm. 2n = 36.

Flowering Mar–Aug. Sandhills, dry sandy woods, sandy old fields; 0–600 m; Ala., Fla., Ga., Ky., La., Miss., N.C., S.C., Va.

In Kentucky, Cnidoscolus stimulosus is occasionally naturalized along railroads. Although closely related to C. urens (Linnaeus) Arthur of Mexico, Central America, and South America, C. stimulosus differs in habit, leaf pubescence, and seed shape, and the two are treated here as distinct species.


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