This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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..
Erect or decumbent herbs, with opposite mostly dentate leaves. Flowers axillary, solitary, peduncled, pink, violet, or yellow, usually showy. Calyx prismatic, 5-angled, 5-toothed, the upper tooth usually the largest. Corolla irregular, its tube cylindric with a pair of ridges on the lower side within, its limb 2-lipped; upper lip erect or reflexed, 2-lobed; lower lip spreading, 3-lobed, the lobes rounded. Stamens 4, didynamous, inserted on the corolla-tube; anther-sacs divergent, or sometimes confluent at the summit. Style filiform; stigma 2-lamel-late. Capsule oblong or linear, loculicidally dehiscent, many-seeded, enclosed by the calyx. [Diminutive of mimus, a mimic actor.]
About 40 species, natives of America. Besides the following, some 30 others occur in the western United States and British Columbia. Type species: Mimulus ringens L. Corolla violet, or rarely white; eastern species.
Leaves sessile, clasping; peduncles longer than the calyx.
1. M. ringens.
Leaves petioled; peduncles shorter than the calyx. Corolla yellow; western; two species adventive in the East. Plants glabrous or glabrate.
2. M. alatus.
Erect; branches spreading; leaves ovate; flowers 1' long.
3. M. Langsdorffii.
Diffuse; leaves nearly orbicular; flowers about 6 long.
4. M. Geyeri.
Plant villous and viscid, diffuse, musk-scented.
5. M. moschatus.
Mimulus ringens L. Sp. Pl. 634. 1753.
Glabrous, perennial by rootstocks; stem erect, 4-sided or somewhat 4-winged, usually much branched, 1°-3° high. Leaves oblong, lanceolate, or oblong-lanceolate, pinnately veined, acuminate or acute at apex, serrate, auriculate-clasping at the base, or the lower merely sessile, 2'-4' long, 1/2'-l' wide; peduncles slender, 1'-2' long in fruit, 2-4 times as long as the calyx; calyx-teeth lanceolate-subulate; corolla violet, rarely white, about 1' long, the throat narrow, exceeding the calyx; base of lower lip puberulent within; fruiting calyx oblong, 6"-8" long; seeds oblong, minute, reticulated.
In swamps and along streams, Nova Scotia to Virginia, Tennessee, Manitoba, Nebraska and Texas. Ascends to 3000 ft. in Virginia. June-Sept.
Similar to the preceding species, glabrous; stem sharply 4-angled, the angles more or less winged. Leaves ovate, ovate-lanceolate, or oblong, acute or acuminate at the apex, dentate-serrate, narrowed at the base, petioled, 2'-5' long, 9"-18" wide; petioles 1/4-1' long, narrowly margined; peduncles stout, shorter than the calyx; corolla violet, 1' long; calyx-teeth short, broad, abruptly mucronulate; seeds smooth.
In swamps, Ontario to Connecticut, Illinois, Kansas, Georgia and Texas. June-Sept.