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.
