Tetragonotheca
Sp. Pl. 2: 903. 1753.
Gen. Pl. ed. 5, 384. 1754.
| Taxon | Illustrator ⠉ | |
|---|---|---|
 | Tetragonotheca helianthoides Tridax procumbens Galinsoga quadriradiata | Yevonn Wilson-Ramsey Yevonn Wilson-Ramsey Yevonn Wilson-Ramsey |
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, glanddotted. 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 lanceovate, 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-angled 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).
Selected References
Lower Taxa
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 |