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..
Characters of the family, as given above. [Greek, five, from the symmetrical flower.] Three known species, natives of eastern North America, Japan and China, the following typical.
Penthorum sedoides L. Sp. Pl. 432. 1753.
Glabrous, erect, stem usually branched and angled above, terete below, 6'-2° high. Leaves lanceolate or narrowly elliptic, acuminate at each end, finely serrate, 2-4' long, 6"-12" wide; cymes 2-3-forked, the branches 1'-3' long; flowers short-pedicelled, about 2" broad; sepals triangular-ovate, acute, shorter than the flattish capsule; petals linear or linear-spatulate, often or generally wanting.