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 incognita Brainerd, Rhodora 7: 84. 1905.
Rootstock slender, in older plants enlarging upward; peduncles, petioles and lower surface of leaves pubescent with soft white hairs, especially when young, the upper leaf-surface glabrous; blades at petaliferous flowering orbicular or reniform, 3/4'-1 1/2' wide, the apex abruptly short-pointed; aestival leaves with large, rugose blades, broadly ovate, cordate usually with open sinus, mostly acute, 2 1/2'-3' wide; scapes hardly taller than the leaves; petals white, the lateral bearded, the upper pair obovate, flowering early; seeds narrowly obovoid, obtuse at base, smooth, brown, 1" long; plant in summer producing numerous filiform runners.
Mountains and low moist woodlands, Newfoundland to Dakota, south to the mountains of eastern Tennessee. Var. Forbesii Brainerd is nearly or quite glabrous, except often for minute scattered hairs on the upper leaf-surface. April-May.
V. amoena Le Conte, Ann. Lyc. N. Y. 2: 144. 1826.
Viola blanda var. palustriformis A. Gray, Bot. Gaz.
11: 255. 1886.
Petioles and scapes glabrous, usually tinged with red, the scapes much exceeding the leaves; blades ovate, cordate with narrow sinus, commonly acute, often somewhat acuminate, rarely over 2 1/2' wide when mature, glabrous except for minute scattered hairs on the upper surface; lateral petals beardless, the upper pair often long, narrow, and strongly reflexed, sometimes twisted; cleistogamous capsules ovoid, dark purple; seeds dark brown, minutely rugose, acute at base, 3/4" long; plant freely producing in summer slender leafy runners.
Cool ravines and moist shady slopes in humus, western Quebec and western New England to Minnesota, south in the mountains to northern Georgia. In petaliferous flower 10-14 days later than either of the two preceding species. April-May.
V. rotundifolia var. pallens Banks; DC. Prodr.
1: 295. 1824. Viola blanda recent authors. Not Willd. Viola pallens Brainerd, Rhodora 7: 247. 1905.
Petioles and scapes in summer often dotted with red and more or less hirsutu-lous; blades glabrous on both sides, broadly ovate or orbicular, cordate, 1/2'-2 1/2' wide, crenate-serrate, obtuse or rounded at apex; flowers faintly fragrant, lateral petals usually bearing a small tuft of hairs, upper petals broadly obovate; capsules green, ellipsoid-cylindric; seeds \" long, almost black; stolons slender, often bearing small leaves and cleistogamous flowers.
Springy land and along cold brooks, Labrador to Alberta, south to the mountains of South Carolina and Tennessee, and in the Rocky Mountains to Colorado. American sweet violet. Long mistaken for V. blanda Willd., and figured for that species in the first edition of this work. April-May.