7. Tragia L. (noseburn, tragia)

(Miller and Webster, 1967)

Plants perennial herbs, monoecious, usually with a woody vertical rootstock, with clear sap, variously pubescent with shorter, unbranched, nonglandular hairs and at least some longer, needlelike, stinging hairs. Stems solitary or few to several, prostrate to ascending, sometimes twining, branched or unbranched. Leaves alternate, short- to long-petiolate, the petiole attached at the base of the nonpeltate blade. Leaf blades linear to lanceolate-triangular, ovate-triangular, or heart-shaped, rounded, truncate, or cordate at the base, rounded or more commonly angled or tapered to a usually sharply pointed tip, the margins toothed, usually pinnately veined (sometimes appearing somewhat 3- or 5-veined in T. cordata). Stipules scalelike or somewhat leaflike, 1–8 mm long, green or tan to brown, usually persistent, narrowly lanceolate to narrowly ovate-triangular, the margins usually with sparse to moderate spreading hairs. Inflorescences lateral and opposite the leaves (also terminal elsewhere), slender racemes with 1(2) pistillate flower(s) at the base and usually several to many nodes with solitary staminate flowers toward the tip, the nodes usually not crowded at flowering, each flower with a short, slender bract (this not folded longitudinally but sometimes slightly concave). Flowers lacking a corolla and nectar disc. Staminate flowers with the stalk jointed toward the base (the portion below the joint persistent, the upper portion shed with the flower), with 2 or 3 small stamens (more elsewhere) often having somewhat thickened filaments (these usually fused at the base). Pistillate flowers with the ovary having usually 3 locules and 1 ovule per locule, the 3 styles fused toward the base, not further lobed or branched. Fruits 3-lobed (rarely 1 of the carpels aborting and the capsule then with 2 larger lobes and 1 much smaller lobe), more or less explosively dehiscent, the seed usually dispersed with the associated portion of fruit wall. Seeds nearly spherical, the caruncle absent, the surface smooth (appearing roughened elsewhere), yellowish brown to dark brown, sometimes mottled with light yellow. About 150 species, North America to South America, Caribbean Islands, Africa, Asia, Australia.

Steyermark (1963) included only two species for Missouri, T. cordata and T. urticifolia Michx. The plants that he placed into the latter species are here treated as T. betonicifolia and T. ramosa, following Miller and Webster (1967). True T. urticifolia is similar to T. betonicifolia in its overall appearance but differs in its usually more conspicuously hairy stems and in having the persistent basal portion of the staminate flower stalks relatively long, longer than the subtending bract. It occurs from North Carolina and apparently Kentucky to Florida west to Arkansas and Texas.

The morphologically complex, multicellular stinging hairs of Tragia species are sometimes relatively sparse, and the burning reaction may be delayed for a few minutes after initial exposure. The burning sensation is caused by injection of a mixture of mostly complex proteins into the skin, although the specific compound(s) responsible remain undetermined (Burrows and Tyrl, 2001).