Viola sororia Willd.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Glabrous to often evidently spreading-hairy, acaulescent; rhizome short, stout, oblique or horizontal, sometimes branching to form colonies; lvs all merely crenate-serrate, cordate at base, the blade typically held at an angle to the strongly ascending petiole, ovate to orbicular or reniform, acute to often obtuse or rounded above, the summer-lvs to 13 cm wide; fls seldom elevated much above the lvs, 2–3 cm wide, relatively broad and open, appearing flat-faced; pet relatively wide, deep violet to lavender or white, the 2 lateral ones densely bearded with relatively long hairs (many of them ca 1 mm or more) that are only slightly or not at all expanded upwards; spurred pet glabrous or sometimes bearded, nearly or fully as long as the lateral ones; cleistogamous fls stout, on horizontal to erect peduncles; fr thickly ellipsoid, evidently surpassing the sep; seeds dark brown; 2n=54. Moist or wet places, sometimes in disturbed sites and somewhat weedy; Nf. and Que. to B.C., s. to Fla., Tex., and Calif. Apr.–June. (V. affinis, a form with the spurred pet bearded; V. papilionacea, a subglabrous form; V. priceana, the Confederate violet, with pale gray-blue fls and a conspicuous violet eye; V. novae-angliae, a form transitional to no. 3 [Viola sagittata Aiton]; V. floridana; V. langloisii; V. latiuscula; V. missouriensis; V. pratincola; V. septentrionalis)