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 herbs, with simple entire clasping or perfoliate leaves, and compound umbels of yellow or greenish-yellow flowers. Involucre none in our species. Involucels of 5 ovate mucronate bracts. Calyx-teeth obsolete. Petals broad, the apex inflexed or infolded. Stylopodium conic. Styles short. Fruit oblong or oval, somewhat compressed laterally. Carpels angled, with slender equal ribs; oil-tubes none in our species. Seed-face concave. [Greek, ox-ribbed, referring to the leaves.]
About 65 species of wide geographic distribution Besides the following another occurs in the Rocky Mountains and northwestern America. Type species: Bupleurum rigidum L.
Bupleurum rotundifolium L. Sp. Pl. 236. 1753.
Annual, erect, rather stiff, branching, glabrous, pale, 1°-2° high. Leaves broadly ovate, or oval, mostly obtuse, mucronate, 1' - 1 1/2' long, perfoliate, or the lowest narrowed into a petiole; umbels terminal, 3-6-rayed, the rays seldom over 4" long; bracts of the involucels about as long as the rays, yellowish; fruit glabrous, about 1 1/2" long.
Bupleurum Odontites L., also European, with narrowly linear leaves, is recorded as found in Massachusetts.