This relative of onobrychis may be globally extinct. It was known only from "islands of the Ohio River" near New Albany (Ind.), especially Rock Island at the Falls (Baskin et al. 1986). Short (1842) wrote about this species and Solidago shortii: "They occupy almost exclusively a tract of rocky waste which is submerged for half the year, during which time it is swept over by a furious current, under which no plant could maintain a footing but by sticking its roots deep into the fissures in the rocks." Rock Island was largely destroyed during the early 20th Century, in connection with lock-and-dam construction. However, further searching is still warranted along nearby banks of the river and tributaries draining native grassland, e.g., up the Salt River to the Cedar Grove area in BULL and along the Blue Rv. in Ind. It differs from other broadleaved species of Orbexilum (macrophyllum and onobrychis) as follows (W): plants eglandular (versus glandular, at least on upper leaflet surfaces); leaflets 3.7-5.5 cm long (versus 4-12 cm); stipules subfoliaceous, 1.0-1.3 mm long (versus lanceolate to linear, up to 10 mm). Its fruits remain unknown. O. macrophyllum (Rowlee) Rudb. is known only from colls. in 1897 and 1899 from Polk Co., N.Car., on "wooded slopes of mountain on Blue Ridge escarpment, precise habitat not known (probably nutrient-rich dry woodlands)" (W). It differs from onobrychis in its the broader subcordate shape of its leaflets, more glandulasr leaves and calices, and larger petals (W); fruits also remain unknown.