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..
Low annual herbs, with rather stiff forking stems, opposite subulate leaves connate at the base, no stipules and minute green clustered apetalous flowers. Calyx not bracted, deeply 5-lobed (rarely 4-lobed), the lobes awnless, the cup-like tube (hypanthium) hardened. Stamens 1-10, inserted on the calyx-tube. Ovary ovoid; styles 2, distinct; ovule solitary, pendulous, amphitropous. Utricle I-seeded, enclosed by the calyx. [Greek, referring to the hard calyx-tube.]
About 10 species, of wide geographic distribution in the Old World, the following naturalized from Europe as a weed. Type species: Scleranthus annuus L.
Scleranthus annuus L. Sp. Pl. 406. 1753.
Much branched from long and rather tough roots, the branches prostrate or spreading, 3-5' long, roughish-puberulent or glabrous. Leaves subulate, 2"-12" long, ciliate, light green, often recurved, their bases membranous at the junction; tube of the calyx 10-angled, rather longer than the lobes, usually glabrous, the lobes somewhat angled on the back and their margins incurved.
In fields and waste places or on dry rocks, Quebec and Ontario to Pennsylvania and Florida, mostly near the coast. Naturalized from Europe. Very common in parts of the Eastern and Middle States. Gravel-chickweed. Parsley-piert. March-Oct.