This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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..
Creeping or ascending, branched small leafy annual glabrous herbs, with opposite obovate oval or orbicular sessile entire leaves, and minute white or purplish short-peduncled flowers, solitary in some of the axils. Calyx 4-5-lobed or 4-5-parted. Corolla very irregular, the tube short, the upper lip shorter than the lower, or wanting, the lower 3-lobed, spreading or ascending, the middle lobe the largest. Stamens 2, anterior; filaments short, somewhat dilated or appendaged at the base; anthers small, their sacs distinct, parallel, or slightly divergent. Style short; stigma 2-lobed. Capsules globose, 2-celled by a membranous partition or becoming 1-celled. Seeds several or numerous, minute. [Greek, small flower.]
About 16 species, natives of America. Besides the following, another occurs in the southern United States. Type species: Micranthemum orbiculatum Michx.
Prantl, Nat. Pfl. Fam. 4: Abt. 3b. 77. 1891.
Somewhat fleshy; stem filiform, creeping, the branches ascending, i'-2i' high. Leaves obovate to oval, obtuse, \"-2\" long; flowers about 1/2" long, borne on peduncles of about the same length; calyx campanulate in flower, obovoid in fruit, 4-lobed, usually split along one side; peduncles recurved in fruit; upper lip of the corolla nearly obsolete; middle lobe of the lower lip longer than the lateral ones; appendages at the bases of the stamens nearly as long as the filaments; capsule obovoid-globose, 1/2" in diameter, as long as the calyx.
In tidal mud. New Jersey to Florida. Aug.- Oct. This species is the type of the genus Hemianthus Nutt., which has been regarded as distinct from Micranthemum by other authors, a view which may be maintained.