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 novae-angliae House, Rhodora 6: 226. 1904.
In spring densely villous at the base except on petioles of earliest leaves; blades at petaliferous flowering narrowly ovate-triangular, cordate, about 1 3/4' long, and 3/4' wide, glabrous above, more or less pubescent beneath, crenate-serrate at the base, distantly so toward the apex; the blades in summer becoming about 2' wide, the breadth equalling the length; flowers large, violet-purple, on scapes 3'-4' high, mostly above the leaves; the three lower petals densely villous, upper pair often with scattered hairs; sepals oblong, obtuse, glabrous; cleistogamous flowers sagittate, on ascending peduncles, their capsules nearly globose, mottled with purple, 3"-4" long, subtended by spreading naked auricles; seeds nearly 1" long.
Nearly glabrous; leaves that unfold at vernal flowering narrowly cordate-ovate, and commonly attenuate toward the apex, becoming about 2' wide in summer, the margins noticeably crenate-serrate; petioles slender; corolla violet with the white base conspicuous, spurred petal more or less villous; cleistogamous flowers small, ovoid, on ascending peduncles that lengthen as the capsules ripen; these ellipsoid, 2 1/2"-4" long, usually reddish brown, sometimes green, either glabrous or clothed with minute dense pubescence; sepals half the length of the capsule, with small appressed auricles; seeds normally buff, not quite 1" long.
Viola nephrophylla Greene, Pittonia 3: 144. 1896. Viola vagula Greene, Pittonia 4: 67. 1899.
Nearly or quite glabrous; earliest leaves orbicular or slightly reniform, later leaves broadly ovate, cordate, obtuse or bluntly pointed, crenate-serrate, 1 1/4'-2 1/2 wide; flowers large, violet, on peduncles exceeding the leaves; spurred petal villous, the lateral densely bearded, and the two upper often with scattered hairs; sepals ovate to lanceolate, obtuse and often rounded; cleistogamous flowers ovoid, on erect peduncles at length 1 3/4'-4' high; capsules green, glabrous, short-ellipsoid; seeds olive-brown, nearly 1" long.
Cold mossy bogs and borders of streams and lakes, eastern Quebec to British Columbia, south to northwestern Connecticut, Wisconsin, New Mexico and Washington. May-June.