This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
A glabrous diffusely branchel annual herb, with opposite linear-subulate leaves, their bases connected by a stipular membrane, and small white flowers in terminal bracted cymes. Calyx deeply 4-parted (rarely 5-parted), the segments subulate, scarious-margined below. Corolla rotate-campanulate, bearded in the throat, shorter than the calyx, 4-lobed (rarely 5-lobed), the lobes imbricated in the bud. Stamens 4 (rarely 5), inserted on the corolla, included; filaments short; anthers ovoid-globose. Ovules numerous in each cavity of the ovary, on oblong placentae; style short; stigma capitate or obscurely 2-lobed. Capsule globose-ovoid, slightly compressed, didymous, loculicidally 2-valved, the carpels at length septicidal. Seeds minute, smooth. [Greek, many-stemmed.]
A monotype, abundant in the warmer parts of America.
Polypremum procumbens L. Sp. Pl. III. 1753.
Stems tufted, somewhat rigid, 4-angled, spreading on the ground, ascending or erect, usually much branched, 2-12' long. Leaves narrowly linear, 1/2'-1 1/2' long, 1/2"-1" wide, acute, sessile, minutely rough-toothed on the margins, often with smaller ones fascicled in their axils; flowers solitary, sessile in the forks of the cymes and along their branches, leafy-bracted, the bracts similar to the upper leaves; corolla 1" or less long; capsule crusta-ceous, about 1" in diameter, slightly 2-lobed, the lobes obtuse.
In dry sandy soil, New Jersey and Pennsylvania to Florida, Kentucky, Missouri, Texas and Mexico. Also in the West Indies. Occurs in cultivated fields as a weed. Probably adventive in its northern range. May-Sept.