Dog-tooth or blunt-toothed noseburn Dog-tooth or blunt-toothed noseburn

Tragia nepetifolia Cavanilles var. amblyodonta Müller Arg. in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 15(2): 934. 1866 (as nepetaefolia)

Subshrubs, 1.2–5 dm. Stems erect to trailing, gray-green, apex often flexuous. Leaves: petiole 4–20(–30) mm; blade usually triangular to subhastate, sometimes ovate, 1–4.5 × 0.8–3 cm, base cordate, hastate, or truncate, margins crenate to serrate, apex acute to obtuse. Inflorescences terminal or axillary, glands absent, staminate flowers 5–16 per raceme; staminate bracts 0.9–2 mm. Pedicels: staminate 0.7–1.2 mm, persistent base 0.2–0.8 mm; pistillate 1.5–4 mm in fruit. Staminate flowers: sepals 3–4, green, 0.9–1.2 mm; stamens 3–4, filaments 0.2–0.7 mm. Pistillate flowers: sepals lanceolate, 1–2.5 mm; styles connate to 1/3 length, short-exserted; stigmas undulate to subpapillate. Capsules 7–8 mm wide. Seeds brown with tan mottling, 2.5–3.5 mm. 2n = 110.

Flowering spring–fall; fruiting summer–late fall. Dry, rocky, exposed slopes in xerophytic scrub; 10–1400 m; Ariz., N.Mex., Tex.; Mexico (Chihuahua, Coahuila, Durango, Nuevo León, Tamaulipas).

Tragia amblyodonta is easily distinguished from other members of Tragia by the combination of usually triangular to subhastate leaf blades, gray-green coloration, and painfully stinging hairs. Both stomata diameter and pollen grain size of T. amblyodonta are larger than in any other North American species of Tragia (K. I. Miller and G. L. Webster 1967).