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..
Annual or perennial, erect or diffuse herbs, mostly with broad leaves and large flowers. Calyx ovoid, oblong or tubular, 5-toothed, obscurely nerved. Petals 5, entire or emarginate, long-clawed. Stamens 10. Ovary 1-celled or incompletely 2-4-celled; styles 2. Capsule ovoid or oblong, dehiscent by 4 short apical teeth or valves. [Latin, soap; its juices abound in saponin, and have cleansing qualities.]
About 35 species, natives of Europe, Asia and northern Africa the following typical.
Saponaria officinalis L. Sp. Pl. 408. 1753-
Perennial, glabrous, erect, stout, sparingly branched, leafy, 1°-2° high. Leaves ovate or oval, 2'-3' long, about I' wide, strongly 3-5-ribbed, acute, narrowed at the base into a broad short petiole; flowers pink or whitish, about 1' broad, in dense terminal corymbs, with numerous small lanceolate bracts or floral leaves; calyx tubular, 8"-10" long, faintly nerved, 5-toothed; petals obcordate with a scale at the base of the blade; pod narrowly oblong, shorter than the calyx.
Roadsides and waste places, common in most districts and escaped from gardens, spreading by underground stolons. Naturalized from Europe. Flowers sometimes double. Summer. Called also Fuller's-herb. Boston-, chimney-, hedge- or old-maid's pink. Sheepweed. Soap-root. Soapwort-gentian. World's-wonder. Sweet-betty. Wild sweet-william. Lady-by-the-gate. Wood's-phlox. Mock-gilliflower.