Xanthocephalum

Willdenow

Ges. Naturf. Freunde Berlin Mag. Neusten Entdeck. Gesammten Naturk. 1: 140. 1807.

Etymology: Greek xanthos, yellow, and kephale, head
Treatment appears in FNA Volume 20. Treatment on page 436. Mentioned on page 9, 89, 437, 438.

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.

... more about "Xanthocephalum"
not tailed +, rounded +  and obtuse +
distinct +
subequal +
scarious +
usually triangular +  and linear +
usually deltate +  and lanceolate +
indeterminate +  and determinate +
Guy L. Nesom +
Willdenow +
decurrent +
oblanceolate +
rugulose +  and muricate +
barbellulate +  and barbellate +
not 2-lipped +  and actinomorphic +
yellow +  and orange-yellow +
ampliate +
lacerate +
beaked +, 2-ribbed +  and 5-ribbed +
compressed +, irregularly ovoid +  and oblong +
fertile +  and bisexual +
fertile +  and bisexual +
sw United States +  and Mexico +
rounded +
Greek xanthos, yellow, and kephale, head +
gland-dotted +
strigillose +, glabrous +  and glandular +
turgid;cylindric +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
in corymbiform arrays +  and singly +
indeterminate +
heterogamous +  and homogamous +
each +  and sessile +
0.4 cm4 mm <br />0.004 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
0.23 cm2.3 mm <br />0.0023 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
campanulate +
0.5 cm5 mm <br />0.005 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
triangular-lanceolate +
dentate to pinnatifid +  and entire +
spinulose-toothed +  and entire +
2-carpellate +
persistent +
Ges. Naturf. Freunde Berlin Mag. Neusten Entdeck. Gesammten Naturk. +
bearing subulate enations +, hairy +  and bristly +
pitted to smooth +  and pitted +
lane1983a +, nesom1989d +  and solbrig1961b +
prominent +
strigillose +  and glabrous +
turgid +  and cylindric +
awnlike +
exalbuminous +
branched +  and simple +
resinous +
erect +  and decumbent-ascending or prostrate +
appendaged +  and truncate +
papillate +  and smooth +
Compositae +
Xanthocephalum +
Asteraceae tribe Astereae +
ovatelanceolate +
unequal +
white-indurate +
slightly longer +
2 cm20 mm <br />0.02 m <br /> (200 cm2,000 mm <br />2 m <br />) +
tree +, shrub +  and subshrub +