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FNA | Family List | FNA Vol. 20 | Asteraceae | Gutierrezia

3. Gutierrezia texana (de Candolle) Torrey & A. Gray, Fl. N. Amer. 2: 194. 1842.

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.

1 Involucres (2–)3.5–4.5 mm diam.; disc florets 10–48; cypselae moderately to densely strigoso-sericeous, hairs usually in dense lines and at least partially obscuring faces; pappi of distinct scales 0.2–0.5 mm, rarely more reduced   3a Gutierrezia texana var. glutinosa
+ Involucres 2–3 mm diam.; disc florets 7–13; cypselae sparsely and evenly strigose, hairs not obscuring cypsela faces; pappi of continuous or scaly crowns less than 0.1 mm 3b. Gutierrezia texana var. texana   (1)


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