Heads discoid, 4-flowered. Involucre of 4 scales. Receptacle small. Flowers, achenes, etc., as in Eupatorium.—Twining perennials, climbing bushes, with opposite commonly heart-shaped and petioled leaves, and corymbose-panicled flesh-colored flowers. (Named for Prof. Mikan, of Prague.)
1. M. scándens, L. Nearly smooth, twining; leaves somewhat triangular-heart-shaped or halberd-form, pointed, toothed at the base.—Copses along streams, E. New Eng. to Ky., and southward. July–Sept.
5. EUPATÒRIUM, Tourn. Thoroughwort.
Heads discoid, 3–many-flowered; flowers perfect. Involucre cylindrical or bell-shaped, of more than 4 scales. Receptacle flat or conical, naked. Corolla 5-toothed. Achenes 5-angled; pappus a single row of slender capillary barely roughish bristles.—Erect perennial herbs, often sprinkled with bitter resinous dots, with generally corymbose heads of white, bluish, or purple blossoms, appearing near the close of summer. (Dedicated to Eupator Mithridates, who is said to have used a species of the genus in medicine.)
§ 1. EUPATORIUM proper. Receptacle flat.
[*] Heads cylindrical, 5–15-flowered; the purplish scales numerous, closely imbricated in several rows, of unequal length, slightly striate; stout herbs, with ample mostly whorled leaves, and flesh-colored flowers.
1. E. purpùreum, L. (Joe-Pye Weed. Trumpet-Weed.) Stems tall and stout, simple; leaves 3–6 in a whorl, oblong-ovate or lanceolate, pointed, very veiny, roughish, toothed; corymbs very dense and compound.—Varies greatly in size (2–12° high), etc., and with spotted or unspotted, often dotted stems, etc.,—including several nominal species.—Low grounds; common.
Var. amœ̀num, Gray. Low; leaves fewer, ovate or oblong; heads few, 3–5-flowered.—Mountains of Va. and N. Y.
[*][*] Heads 3–20-flowered; involucre 8–15 more or less imbricated and unequal scales, the outer ones shorter; flowers white.
[+] Leaves all alternate, mostly dissected; heads panicled, very small, 3–5-flowered.