Viola tricolor L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Glabrous or hairy annual or short-lived perennial to 3 dm, often branched from the base; lvs all crenate, the lowest ones orbicular or cordate, the upper oblong to elliptic and basally cuneate; stipules foliaceous, laciniate to lyrate-pinnatifid, the middle lobe oblanceolate, distinctly toothed; internodes usually shorter than the lvs; fls 1.5–2.5 cm wide, the sep two-thirds as long as the pet; pet variously colored, the upper usually darker than the lower; style as in no. 27 [Viola rafinesquii Greene]; cleistogamous fls wanting; frs ellipsoid or oblong-ellipsoid, 6–10 mm; seeds dark brown; 2n=26. Native of Europe, extensively cult. and casually escaped in our range.