151. Gundlachia A. Gray, Proc. Amer. Acad. Arts. 16: 100. 1880.
Goldenshrub [For John Gundlach, 1810–1896, naturalist and traveler]
Lowell E. Urbatsch, Roland P. Roberts, Kurt M. Neubig
Shrubs, [8–]10–100[–200] cm. Stems erect to ascending, abundantly branched [simple], glabrous or papillate-scabrous [scabrous, sparsely hairy, often gland-dotted] , usually resinous. Leaves cauline (evenly spaced [clustered at branch tips]); sessile [short-petiolate]; blades (midveins obscure [prominent]) filiform [linear, elliptic, or obovate] (flat to involute-terete), margins entire [minutely toothed] (apices obtuse to acute, sometimes apiculate), faces sparsely hairy [glabrous, papillate, scabrous], often gland-dotted [sometimes in deep pits], resinous. Heads discoid [radiate], usually clustered at branch tips, clusters few [numerous and sometimes hidden by surrounding leaves], in cymiform or racemiform [paniculiform to corymbiform] arrays. Involucres turbinate [cylindric to nearly hemispheric], (4–6 ×) 2–3[–8] mm. Phyllaries 8–30 in [2–]3–4[–5] series (mostly tan), 1-nerved (midveins evident and expanded apically, less evident to obscure proximally); mostly keeled, except innermost [convex to flat], [ovate] narrowly ovate to lanceolate or obovate [linear-lanceolate], unequal, chartaceous proximally or throughout, outer sometimes herbaceous or herbaceous-tipped, margins scarious (entire, lacerate to fimbriate), (apices acute to rounded [acuminate]) faces glabrous or sometime pustulate, usually resinous. Receptacles flat to convex, pitted, epaleate (pit borders short-scaly [short-awned]). Ray florets 0[–12, pistillate, fertile; corollas pale yellow to white]. Disc florets 3–7[–50], bisexual, fertile; corollas pale yellow [yellow to white], tubes often longer than narrowly campanulate [tubular, distally dilated] throats, lobes 5, spreading to recurved [laxly erect], narrowly lanceolate to triangular (unequal); style-branch (linear lanceolate to ovate, 0.9–2.5 mm) appendages linear to subulate. Cypselae (tan [to coppery bronze]) turbinate [cylindric, elliptic, or obovoid], mostly 5–8 nerved, faces sparsely to densely hairy; pappi persistent, of 40–50 whitish or tan, barbellate, apically attenuate bristles in 1 series. x = 9.
Species 6 (1 in the flora): Texas, n Mexico, Bahamas, West Indies, South America (n Venezuela).
Gundlachia grows in arid habitats in rocky to sandy soils.
Phylogenetic analyses (L. E. Urbatsch et al. 2003) demonstrated the polyphyly of genus Xylothamia G. L. Nesom, Y. Suh, D. R. Morgan & B. B. Simpson and showed that some species assigned there are more closely related to Gundlachia.