This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Viola primulifolia L. Sp. Pl. 934. 1753.
Often quite glabrous, but usually somewhat pubescent, especially toward the base of the petioles; blades oblong to ovate, obscurely crenate-serrate, base slightly cordate, rounded or tapering, petioles often broadly winged above; scapes 2'-10' high, often longer than the leaves; flowers similar to those of V. lanceolata; sepals lanceolate, acuminate; the three lower petals purple-veined, the lateral ones slightly bearded or beardless; capsules green, ellipsoid, 3"-5" long, those from the numerous late cleistogamous flowers on rather short, erect peduncles; seeds reddish brown, \" long.
Viola lanceolata L. Sp. Pl. 934. 1753.
Glabrous, usually profusely stoloniferous in late summer, the stolons rooting at the nodes and bearing apetalous flowers; rootstock slender; scapes 2'-4' high; mature leaves lanceolate or elliptical, the blade 2 1/2'-6' long, 5"-10" wide, gradually tapering into the margined, often reddish petiole, obscurely crenulate; sepals lanceolate, acuminate, 2"-3" long; petals 3"-4" long, usually all beardless, the three lower striped with purplish veins; capsules green, ellipsoid, 3"-6" long, those of the cleistogamous flowers on erect peduncles, usually shorter than the leaves; seeds dark brown.
V. rotundifolia Michx. Fl. Bor. Am. 2: 150. 1803.
Rootstock long and stout, jagged with the persistent bases of former leaves; stolons short, usually without roots or leaves, bearing 1-4 cleistogamous flowers; leaves oval or orbicular, obtuse, cordate with short and narrow sinus, repand-crenulate, at vernal flowering sparsely hirtellous, about 1' wide; in midsummer mostly glabrate, 2'-4' wide, prostrate; scapes 2'-4' high; flowers bright yellow, the three lower petals with brown lines, the lateral bearded; style club-shaped, abruptly capitate, beakless; capsule ovoid, 3"-4" long, those from the cleistogamous flowers on deflexed peduncles and closely dotted with purple; seeds nearly white.