§ 1. Flowers large, purple, in a long raceme; calyx-limb deeply parted; petals entire; stamens and style successively deflexed; stigma of 4 long lobes.
1. E. angustifòlium, L. (Great Willow-herb. Fire-weed.) Stem simple, tall (4–7°); leaves scattered, ample, lanceolate, nearly entire.—Low grounds, especially in newly cleared lands; N. Eng. to N. C., west to Minn. and E. Kan., and far north and westward. (Eu., Asia.)
§ 2. Flowers mostly small and corymbed or panicled; calyx-limb 5-cleft; petals mostly deeply notched; stamens and style erect.
[*] Stigma 4-parted; stem terete.
E. hirsùrum, L. Densely soft-hairy, stout, branching (3–5° high); leaves mostly opposite, lance-oblong, serrulate, sessile; flowers in the upper axils or in a leafy short raceme; petals 6´´ long, rose-purple.—Waste grounds, Mass. to N. Y. and Ont. (Nat. from Eu.)
[*][*] Stigma clavate; stem terete, without decurrent lines (or with traces in n. 2); leaves numerous, the lower opposite, subentire, with revolute margins.
2. E. lineàre, Muhl. Usually much branched above and minutely hoary-pubescent, 1–2° high; leaves linear-lanceolate, tapering to a short but distinct petiole, acutish; flowers numerous, pale; capsules hoary, on pedicels as long as the leaves. (E. palustre, var. lineare, Gray, mainly.)—Bogs, N. Eng. to Penn., Iowa, and northward.
3. E. stríctum, Muhl. Erect, 1–2½° high, densely beset with soft spreading somewhat glandular white hairs; leaves broader, more obtuse and with evident veins, very short-petioled or sessile; pubescence of the capsule soft and spreading. (E. molle, Torr.)—Bogs, Mass. to Minn., south to Va. and Ill.
[*][*][*] Stigma clavate; stem somewhat quadrangular with 2–4 ridges or hairy lines decurrent from some of the leaves.
[+] Tall and mostly branching, many-flowered; leaves rather large, toothed, not revolute, the lower opposite; seeds papillose.