Xanthocephalum
Ges. Naturf. Freunde Berlin Mag. Neusten Entdeck. Gesammten Naturk. 1: 140. 1807.
| Taxon | Illustrator ⠉ | |
|---|---|---|
 | Xanthocephalum gymnospermoides Rayjacksonia phyllocephala Grindelia arizonica | Barbara Alongi Barbara Alongi Yevonn Wilson-Ramsey |
Annuals [perennials], 2–200 cm (taprooted [rhizomatous]). Stems erect to decumbent-ascending or prostrate, simple or branched, glandular and/or resinous. Leaves mostly cauline [basal and cauline]; alternate; sessile (sometimes decurrent); blades 1-nerved, oblanceolate, margins entire or spinulose-toothed (apices acute to obtuse), faces glabrous, gland-dotted [sometimes stipitate-glandular]. Heads radiate [discoid], borne singly or in corymbiform arrays. Involucres campanulate [hemispheric], 2.3–4 [–7] × 5–7 [–8] mm. Phyllaries [20–] 30–40 in 2–4 series, appressed or tips spreading, 1-nerved (nerves thin; flat or outer proximally convex), ovatelanceolate, unequal, white-indurate proximally, green distally, margins of inner scarious, faces glabrous or glandular, often viscid. Receptacles shallowly convex, shallowly pitted to smooth (except for raised points of cypsela attachment), epaleate. Ray-florets [14–] 15–47 [–62, sometimes 0], pistillate, fertile; corollas yellow to orange-yellow. Disc-florets [20–] 40–200 [–280], bisexual, fertile; corollas abruptly ampliate, tubes equaling or slightly longer [shorter] than funnelform throats, lobes 5, erect, triangular-lanceolate; style-branch appendages deltate. Cypselae (brownish) irregularly ovoid to oblong, compressed with rounded edges to nearly cylindric or 4–6-sided, turgid (thick-walled), without prominent ribs, faces glabrous or sparsely strigillose; pappi 0 or persistent, usually minutely crowns of awnlike scales or lacerate crowns, rarely also with short, flat bristles, usually shorter in ray. x = 6.
Distribution
sw United States, Mexico
Discussion
Species 6 (1 in the flora).
The circumscription of Xanthocephalum was clarified by M. A. Lane (1982, 1983) with the transfer to Gutierrezia of some taxa traditionally included within it. The genus is distinguished from Gutierrezia by its glabrous, pitted receptacles, abruptly ampliate disc corollas, deltate style appendages, glabrous cypselae with coroniform pappi of basally fused scales or essentially lacking, and base chromosome number of x = 6.