Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep 5, subequal, oblong or spatulate; cor campanulate, equaling or shorter than the cal, induplicate-valvate in bud, deeply lobed; stamens surpassed by the cor; ovary deeply divided into 2 essentially separate carpels, the 2 styles arising between them at the base; each carpel with 2 ovules; stigmas capitate; fr thin-walled, indehiscent or irregularly dehiscent, subtended by the persistent cal; creeping herbs with reniform to rotund lvs and small, axillary, greenish-white fls solitary on pedicels usually shorter than the lvs. 15+, warm reg.