Cnidoscolus

Herbs [shrubs or trees], perennial, monoecious; hairs unbranched, always some stinging; latex white. Leaves [persistent or deciduous], alternate, simple; stipules present, deciduous [persistent]; petiole present, glands present at apex; blade palmately lobed [unlobed], margins entire or dentate, laminar glands absent; venation palmate (pinnate in lobes) [pinnate]. Inflorescences bisexual (pistillate flowers central, staminate lateral), terminal, dichasial cymes; glands subtending each bract 0. Pedicels present. Staminate flowers: sepals 5, white, petaloid, imbricate, connate 1/2 length; petals 0; nectary intrastaminal, annular; stamens [8–]10[–25] in 2[–6] whorls, outer whorl distinct [connate proximally], inner whorl connate proximally; staminodes absent or present at apex of staminal column; pistillode absent. Pistillate flowers: sepals 5, white, petaloid, distinct [connate proximally]; petals 0; nectary annular; staminodes often present; pistil 3-carpellate; styles 3, connate basally, [1–]2–3 times 2-fid. Fruits capsules. Seeds ovoid; caruncle present. x = 9.

Distribution

s United States, Mexico, West Indies, Central America, South America.

Discussion

Species ca. 50 (3 in the flora).

The characteristic stinging hairs of Cnidoscolus immediately distinguish it from Manihot, which appears to be its closest relative, as shown by morphological (G. L. Webster 1994) and DNA sequence data (K. Wurdack et al. 2005). Although the chemistry of the stinging hairs has been little studied, those of C. texanus have been shown to contain serotonin, but not histamine and acetylcholine as in the stinging hairs of some true nettles in Urticaceae (S. E. Lookadoo and A. J. Pollard 1991). The roots of Cnidoscolus, like those of Manihot, are rich in edible starch; the seeds also are edible. The leaves of two tropical species, C. aconitifolius (Miller) I. M. Johnston and C. chayamansa McVaugh, are eaten as a vegetable.

Selected References

None.

Lower Taxa

Cnidoscolus angustidens, Cnidoscolus stimulosus, Cnidoscolus texanus

Key

1	Leaf blades moderately lobed, lobes 1/3–1/2 blade length, lobe apices and marginal teeth acuminate, aristate; staminate flower calyx tubes 4–6 mm; stamens subequal, filaments all connate most of length.	Cnidoscolus angustidens
1	Leaf blades deeply lobed, lobes (1/2–)3/5–9/10 blade length, lobe apices and marginal teeth acute to obtuse, not aristate; staminate flower calyx tubes 8–17 mm; stamens of outer whorl shorter than inner whorl, filaments of outer whorl distinct or connate basally, of inner whorl connate most of length.	> 2
2	Staminate flower calyx tubes 8–11 mm, distally straight or constricted, without stinging hairs, lobes 7–10 mm; capsules 10–12 mm; seeds 8–9 mm.	Cnidoscolus stimulosus
2	Staminate flower calyx tubes 12–17 mm, distally flaring, with stinging hairs, lobes 10–17 mm; capsules 15–20 mm; seeds 14–18 mm.	Cnidoscolus texanus