Viola arvensis Murray
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Pubescent to glabrate annual to 30 cm, often branched from the base, the stem relatively robust, with short, reflexed hairs on the angles; lvs variable, the lowest orbicular to ovate, the upper oblong to elliptic or narrowly elliptic, all crenate; stipules foliaceous, laciniate into 5–9 slender segments and usually 1 lf-like segment often nearly as large as the main blade; fls 1–1.5 cm long, scarcely 1 cm wide; pet shorter than or barely equaling the broadly lanceolate sep, all pale yellow ("ivory") or occasionally with purplish tips; spur short; style as in no. 27 [Viola rafinesquii Greene]; cleistogamous fls wanting; frs globose to ellipsoid, 5–10 mm; seeds brown; 2n=34. Native of Europe, now established as a weed in or near fields or along roadsides throughout our range and s. and w. Apr.–Sept.
European field pansy