Cal 5-lobed to about the middle, each lobe with a smaller tooth on each side near the base, the whole strongly accrescent, becoming compressed, firm, strongly reticulate-veiny, and shortly prickly-hispid with curved or hooked hairs; cor small, blue, ±campanulate, with well developed fornices; anthers included; nutlets obliquely compressed, narrowly ovate, rough, attached to an elevated gynobase, the small scar situated just within the margin above the middle; annual weeds with weak, climbing-scrambling, retrorsely prickly-hispid stems and opposite to partly alternate or partly whorled lvs that are subentire and often remote; fls on short, stout, recurved pedicels in or near the axils of lvs or bracts, and in the forks of the branches. Monospecific.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.