Sep 5 (in our spp.), distinct, imbricate, the upper median one about twice as wide as the 2 lower and 4 times as wide as the lateral ones; cor tubular or campanulate to salverform, in our spp. virtually regular or with the 2 upper lobes connate half-length; stamens (2-)4, inserted below the middle of the cor-tube; pollen-sacs parallel; stigmas 2 and distinct or one and bilobed; fr globose, septicidal and/or loculicidal; small perennial herbs of wet shores or shallow water, with sessile, opposite, entire or toothed lvs and small, white or blue fls borne singly or in pairs in the lf-axils. 100, warm reg.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.