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..
Perennial herbs, with odd-pinnate, stipulate leaves, and small, perfect and imperfect flowers in dense heads. Calyx-tube 4-angled, constricted at the throat, 4-lobed. Petals 4. Perfect flowers with several or numerous declined stamens, the filaments capillary. Pistils 2; style terminal; stigmas brush-like. Achene enclosed in the thickened, 4-angled calyx-tube. Seed suspended. [Greek, goblet or beaker.]
About four species, natives of the Old World, the following typical.
Poterium Sanguisorba L. Sp. Pl. 994. 1753. Sanguisorba minor Scop. Fl. Carn. Ed. 2, 1: no.
Glabrous or pubescent, erect, slender, perennial, branched, 10'-20' high. Stipules usually small, laciniate; leaflets 7-19, ovate or broadly oval, deeply incised, short-stalked or sessile, 6"-10" long; flowers greenish, in dense peduncled globose-ovoid heads, 3"-6" long, the lower ones perfect or staminate, the upper pistillate; stamens 12 or more, drooping; stigmas purple; calyx-lobes ovate, acute or acutish; fruit 1"-2" long.
In dry or rocky soil and in ballast, southern Ontario, Maine, New York and Pennsylvania to Maryland. Naturalized or adventive from Europe and native also of Asia. Summer. Garden-burnet. Blood-wort. Bibernel. Pimpernelle. Toper's-plant.