Texas snakeweed

Hemiachyris texana de Candolle in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 314. 1836; Xanthocephalum texanum (de Candolle) Shinners

Annuals, 10–80(–100) cm. Stems glabrous. Leaves: proximal usually absent at flowering; cauline blades 1- or 3-nerved, linear , 1.5–4 mm wide, reduced distally. Heads in loose arrays. Involucres campanulate to obconic, 2–4.5 mm diam.. Phyllary apices flat. Ray florets 5–23; corollas yellow, 3–6 mm. Disc florets 7–48 (bisexual and fertile or functionally staminate). Cypselae 1.3–1.8 mm, faces without oil cavities, loosely strigose (hairs appressed, apices acute, microscopically 2-pronged); pappi of 1 series of spreading-erect, oblong to ovate or obovate scales 0.1–0.5 mm (bases sometimes connate, usually shorter in rays, sometimes 0 in var. texana).

Varieties 2 (2 in the flora): s, sc United States, Mexico.

Although the two varieties of Gutierrezia texana are similar, the geographic demarcation between them appears to be sharp, and a detailed investigation of their biologic interaction would be interesting.