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..
Slender, finely pubescent and resinous, 2°-3° high, branched at the summit, the inflorescence comparatively small, 3'-4' broad. Leaves opposite, closely sessile, clasping, or slightly connate-perfoliate at the base, linear-lanceolate, long-acuminate, sharply serrate, 3'-6' long, 3"-6" wide, roughish above, canescent beneath; heads 10-15-flowered; involucre campanulate, about 2" high, its bracts oblong, obtuse, in 2 or 3 series, the outer shorter; flowers white.
In wet pine-barrens of New Jersey. Aug.-Sept.
E. urticaefolium Reichard, Syst. 3: 719.
Glabrous or villous and somewhat viscid, much branched, 1°-4° high. Leaves opposite, ovate, thin, acuminate at apex, rounded, truncate or cordate at the base, or abruptly narrowed into the slender petiole, coarsely and usually sharply dentate-serrate, sometimes crenate, 3'-6' long, 1'-3' wide, 3-nerved and veiny; petioles 1/2'-21/2' long; inflorescence rather loose, ample; heads 10-30-flowered; receptacle flat; . involucre narrowly campanulate, about 2" high, its bracts linear, acute or acuminate, in 1 or 2 series, equal or nearly so; flowers bright white.
Eupatorium aromaticum L. Sp. PI. 839. 1753.
Puberulent or glabrate, slender, branched at the summit, 1°-2° high. Leaves opposite, peti-oled, firm, obtuse or acutish at the apex, rounded, cordate or sometimes narrowed at the base, crenate-dentate, 1 1/2'-3' long, 9"-i8" wide, 3-nerved and veiny; petioles 2"-8" long; inflorescence usually compact; heads 10-25-flow-ered; receptacle flat; involucre campanulate, 1 1/2"-2" high, its bracts linear, generally obtuse, in 1 or 2 series; flowers white.
In dry soil, Massachusetts to Florida, Pennsylvania, West Virginia, Tennessee and Mississippi. Blooms rather later than the preceding species where the two grow together, near New York. Called also poolroot, poolwort, and wild hoar-hound. Aug.-Oct.
Fig. 4171. E. Incarnatum Walt. Fl. Car. 200. 1788
Minutely pubescent, 2°-4° high, sometimes reclining, often diffusely branched. Leaves opposite, deltoid-ovate, 3/4'-21/4' long, long-pointed, rather coarsely blunt-serrate or crenate-serrate, truncate or cordate at the base, the petioles slender, often as long as the blades; heads about 20-flowered; involucres campanulate, about 2" high, its bracts few, narrowly linear, slightly ribbed when dry, acute; corolla pink or pale purple.
In woods and sandy soil, Virginia to Missouri, Florida and Mexico. Aug.-Oct.