Tetragonotheca

Linnaeus

Sp. Pl. 2: 903. 1753.

Gen. Pl. ed. 5, 384. 1754.

Etymology: Greek tetra, four, gonio, angle, and theca, container, alluding to quadrangular involucres
Treatment appears in FNA Volume 21. Treatment on page 178. Mentioned on page 176.
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Perennials, mostly 30–120 cm. Stems erect. Leaves basal and/or cauline; mostly opposite; petiolate, subpetiolate, or sessile (bases sometimes connate-perfoliate); blades lanceolate, ovate, rhombic, or rounded-deltate, sometimes pinnatifid, ultimate margins usually toothed, faces glabrate, sparsely hispidulous, or puberulent, gland-dotted. Heads radiate, borne singly or in loose, corymbiform arrays. Involucres obpyramidal to hemispheric, 12–25+ mm diam. Phyllaries persistent, 10–25+ in ± 2 series (outer 4 broadly lanceolate, foliaceous, the inner ovate to lanceolate, smaller, more scarious, each subtending a ray floret). Receptacles conic, paleate (paleae persistent, lanceolate to lance-ovate, flat or weakly conduplicate, apices acute). Ray florets 6–21+, pistillate, fertile; corollas yellow (often with reddish nerves). Disc florets 25–150+, bisexual, fertile; corollas yellow, tubes (basally dilated) much shorter than ampliate, cylindric throats, lobes 5, deltate. Cypselae ± ovoid or plumply 4- or 5-angled, finely 32–40-ribbed, sparsely strigose or glabrous; pappi 0, or of 1–10+ subulate to acerose scales (to 0.5 mm), or of 16–30, ± spatulate scales (0.5–2 mm). x = 17.

Distribution

s United States, n Mexico.

Discussion

Species 4 (4 in the flora).

Key

1 Pappi of 16–30, ± obovate to spatulate scales 0.5–2 mm > 2
1 Pappi 0, or of 1–10+ subulate to acerose scales to 0.5 mm > 3
2 Leaves mostly cauline (distal connate-perfoliate); ray florets 12–13, laminae 8–18 mm Tetragonotheca ludoviciana
2 Leaves mostly basal (cauline much smaller, none connate-perfoliate); ray florets 16–21+, laminae 20–30+ mm Tetragonotheca repanda
3 Stems sparsely tomentulose or glabrous (nodes usually auriculate-appendaged); ray laminae 10–18 mm; cypselae ± quadrate, 2.5–4 mm Tetragonotheca texana
3 Stems patently to retrorsely ± villous; ray laminae 20–40+ mm; cypselae ± ovoid, 4–6 mm Tetragonotheca helianthoides
... more about "Tetragonotheca"
John L. Strother +
Linnaeus +
s United States +  and n Mexico. +
Greek tetra, four, gonio, angle, and theca, container, alluding to quadrangular involucres +
Sp. Pl. +  and Gen. Pl. ed. +
1753 +  and 1754 +
turner1980a +
Compositae +
Tetragonotheca +
Asteraceae (tribe Heliantheae) subtribe Galinsoginae +