Tridax procumbens L.

• Title

  Tridax procumbens L.

• Authors

  Nathaniel Lord Britton, Frances W. Horne

• Scientific Name

  Tridax procumbens L.

• Description

  Flora Borinqueña Tridax procumbens Tridax Thistle Family Family Carduaceae Tridax procumbens Linnaeus, Species Plantarum 900. 1753. This low, weed-like plant had not been recorded as found in Porto Rico, until observed by us growing plentifully in hillside pastures and waste grounds in the vicinity of Vega Baja in 1922; we therefore believe that it is a relatively recent introduction from some other part of tropical America; the nearest place previously known for it is St.Croix, where it also appears to have been introduced. Its range extends from Cuba and the Bahamas to southern Florida, and widely through continental tropical America, from northern Mexico to Bolivia; it also inhabits Grenada and Trinidad in the southern Lesser Antilles. The limits of its natural distribution, prior to human intervention cannot be ascertained. No popular names have been recorded. Tridax (Greek, referring to the 3-lobed ray-flowers) is a Linnaean genus of about 12 species of perennial herbs, natives of tropical America, the one here illustrated, which Linnaeus knew from Vera Cruz, typical. Their leaves are opposite, and toothed, or incised; their flower-heads are long-stalked, with ovoid or hemispheric involucres, composed of nearly equal bracts in a few series; the disk-flowers are small, subtended by chaff, perfect and fertile; the usually large and 3-lobed rays of the marginal flowers are pistillate. The little fruits (achenes) are silky-hairy, bearing many aristate, plumose scales (pappus). Tridax procumbens (procumbent) is hirsute, branched near the base, slender, the branches spreading or ascending, from 20 to 50 centimeters long. The broad, pointed, short-stalked leaves are from 2 to 6 centimeters long, the base more or less wedge-shaped, the margins sharply toothed. The solitary flower-heads are borne at the ends of the branches, on a stalk from 10 to 30 centimeters long; the nearly bell-shaped involucre is about 6 millimeters high, its bracts rough-hairy, the outer ones narrower than the inner; the nearly white, 3-lobed rays are from 3 to 7 millimeters long, the achenes about 2 millimeters long,