This annual is widely scattered on wet shorelines across midwestern and northeastern states, but rare to absent in the Ohio Valley. A coll. from LAWR was made by M. Medley (for WKY), and verified by G.C. Tucker. Earlier records were probably all based on colls. that should now be named C. bipartitus Torr. (= C. rivularis Kunth.). These taxa were combined in Robinson & Fernald (1908).