Rhamnus cathartica L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Functionally dioecious shrub or small tree to 6 m, some of the branches usually ending in short thorns; lvs mostly opposite or subopposite, or some of them alternate, broadly elliptic, oblong, or elliptic-obovate, 3–6 cm, at least half as wide, the lateral veins (2)3(4) on each side, strongly upcurved; petiole a third to two-thirds as long as the blade; fls appearing with the lvs, 4-merous; sep 2–3 mm; pet erect, lanceolate, 1–1.3 mm in staminate fls, 0.6 mm in the pistillate; style 4- fid half its length; fr black, 5–6 mm thick, commonly with 4 stones; 2n=24. Native of Eurasia, escaped from cult. at many places in our range.