Amphiachyris

(de Candolle) Nuttall

Trans. Amer. Philos. Soc., n. s. 7: 313. 1840.

Common names: Broomweed
Etymology: Greek amphi -, around, and achyron, chaff or husks, alluding to ring of pappus elements
Basionym: Brachyris sect. Amphiachyris de Candolle Mém. Soc. Phys. Genève 7: 266. 1836
Treatment appears in FNA Volume 20. Treatment on page 87. Mentioned on page 9, 88, 89, 95.

Annuals, 20–100 (–200) cm (glabrous, with strong terpenoid smell when crushed; taprooted). Stems erect, usually branched distally (bases usually lignescent). Leaves cauline; alternate; sessile; blades (1-nerved or 3-nerved) linear to lanceolate, margins entire, faces gland-dotted. Heads radiate, in paniculiform or corymbiform arrays. Involucres narrowly campanulate to turbinate, 2–4 mm diam. Phyllaries 12–15 in 1–2 (–3) series, 1-nerved (nerves without green margins) ovate, unequal, proximal 2/3 indurate, margins hyaline, faces whitish resinous. Receptacles flat to slightly convex, smooth (glabrous or hairy with multicellular, 1-seriate hairs), epaleate. Ray-florets 7–12, pistillate, fertile; corollas yellow, sometimes drying orange-tinged. Disc-florets 10–21, functionally staminate; corollas yellow, tubes shorter than cylindric throats, lobes 5, erect, deltate; style-branch appendages fused (pappi of 5–8 white, basally connate, linear, spatulate-tipped scales in 1 series, ± equaling corollas). Cypselae (ray, purplish black) obovoid-turbinate, plump, 4–9-ribbed (apices attenuate to slightly clavate), faces densely long or short-setulose (hairs appressed, white), mostly occurring in lines between ribs; pappi coroniform. x = 4, 5.

Distribution

c United States

Discussion

Species 2 (2 in the flora).

Amphiachyris was recently treated within a more inclusive Gutierrezia (G. M. Diggs et al. 1999); apparently, it is more closely related to monotypic Thurovia than to Gutierrezia (Y. Suh and B. B. Simpson 1990). Amphiachyris is distinguished from Gutierrezia by a combination of glandular hairs only on the abaxial leaf faces, functionally staminate disc florets, disc pappi of basally connate, narrowly spatulate scales ± equaling corollas, and abaxial nerves of the phyllaries without green borders.

Key

1 Plants 20–40(–60) cm; heads in open paniculiform arrays; cypselae 4–6-ribbed, long-setulose; leaf blades 0.2–1(–2) mm wide; receptacles with hooked, swollen-based hairs Amphiachyris amoena
1 Plants 30–100(–200) cm; heads in crowded corymbiform arrays; cypselae 7–9-ribbed, short-setulose; leaf blades 0.5–6 mm wide; receptacles glabrous Amphiachyris dracunculoides
... more about "Amphiachyris"
not tailed +, rounded +  and obtuse +
distinct +
subequal +
scarious +
usually triangular +  and linear +
usually deltate +  and lanceolate +
corymbiform +  and paniculiform +
indeterminate +  and determinate +
Guy L. Nesom +
(de Candolle) Nuttall +
decurrent +
Brachyris sect. Amphiachyris +
compound +  and simple +
linear;lanceolate +
rugulose +  and muricate +
barbellulate +  and barbellate +
Broomweed +
not 2-lipped +  and actinomorphic +
yellow +  and orange-tinged +
obovoid-turbinate +
fertile +  and bisexual +
c United States +
Greek amphi -, around, and achyron, chaff or husks, alluding to ring of pappus elements +
resinous +
whitish;gland-dotted +
short-setulose +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
indeterminate +
heterogamous +  and homogamous +
each +  and sessile +
0.2 cm2 mm <br />0.002 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
narrowly campanulate;turbinate +
deltate +
2-carpellate +
coroniform +
Trans. Amer. Philos. Soc., n. s. +
bearing subulate enations +, hairy +  and bristly +
flat;slightly convex +
lane1979a +
exalbuminous +
appendaged +  and truncate +
papillate +  and smooth +
Compositae +
Amphiachyris +
Asteraceae tribe Astereae +
cylindric +
100 cm1,000 mm <br />1 m <br /> (200 cm2,000 mm <br />2 m <br />) +
20 cm200 mm <br />0.2 m <br /> (100 cm1,000 mm <br />1 m <br />) +
tree +, shrub +  and subshrub +