Erect, mostly branching, perennial herbs, with opposite or verticillate, or sometimes alternate, often punctate leaves, and in our species cymose-paniculate discoid heads of white, blue or purple flowers. Involucre oblong, ovoid, campanulate, or hemispheric, the bracts imbricated in 2-several series. Receptacle flat, convex, or conic, naked. Corolla regular, its tube slender, its limb 5-lobed or 5-toothed. Anthers obtuse and entire at the base, appendiculate at the apex. Style-branches elongated, flattened, or thickened above, stigmatic at the base. Achenes 5-angled, truncate. Pappus of numerous capillary usually scabrous bristles arranged in 1 row. [Named for Mithridates Eupator, i. e., of a noble father.]

Over 500 species, mostly of warm or tropical regions. Besides the following, some 35 others occur in the southern and western parts of North America. Type species: Eupatorium canna~ binum L.

* Leaves alternate, pinnatifid into filiform segments.

1. E. capillifolium.

** Leaves petioled, verticillate in 3's-6's,or the upper opposite; involucral bracts in several series. Leaves thick, rugose, pubescent; inflorescence depressed. Leaves ovate, acute.

2. E. maculatum.

Leaves lanceolate to ovate-lanceolate, acuminate.

3. E. Bruneri.

Leaves thin, nearly glabrous; inflorescence pyramidal.

4. E. purpureum.

*** Leaves opposite (rarely in 3's), or the uppermost alternate.

† Involucral bracts imbricated in 2 or more series, the outer shorter. 1. Leaves, at least the lower, slender-petioled.

5. E. serotinum.

2. Leaves all sessile, short-petioled or connate-perfoliate. a. Leaves not clasping nor connate-perfoliate. § Leaves narrowed at the base. Bracts of the involucre acute or cuspidate, scarious-tipped, white. Leaves linear-lanceolate, sparingly toothed, 2"-6" wide.

6. E. leucolepis.

Leaves oblong or lanceolate, coarsely toothed, 1/2 '-1 1/2' wide.

7. E. album.

Bracts of the involucre obtuse, not scarious, or but slightly so. Leaves linear, crowded, usually entire, obtuse.

8. E. hyssopifolium.

Leaves lanceolate, oval, or oblong, usually dentate. Leaves linear-lanceolate, acute, dentate.

9. E. Torreyanum.

Leaves oblong to oval, sharply dentate, obtusish or acute.

10. E. semiserratum.

Leaves lanceolate, sparingly dentate, long-acuminate.

11. E. altissimum.

§§ Leaves rounded, obtuse or truncate at the base. Plant glabrous; leaves lanceolate, long-acuminate.

12. E. sessilifolium.

Plants pubescent; leaves ovate or oblong, acute or obtuse.

Leaves ovate-oblone. rounded or narrowed at the base, usually obtuse.

13. E.verbenaefolium.

Leaves broadly ovate, crenate-dentate, mostly truncate at the base, obtusish.

14. E.rotundifohum.

Leaves ovate, dentate, acute.

15. E. pubescens.

b. Leaves clasping or connate-perfoliate at the base. Leaves connate-perfoliate; involucral bracts acute.

16. E. perfoliatum.

Leaves merely clasping; involucral bracts obtuse.

†† Involucral bracts in 1 or 2 series, all equal or nearly so.

17. E. resinosum.

Receptacle flat.

Flowers white; leaves ovate.

Leaves thin. 2'-s' long, sharply dentate, acuminate.

18. E.urticaefolium.

Leaves firm, 1'-2' long, obtusely dentate, acute or obtusish.

19. E. aromaticum.

Flowers pink to purple; leaves deltoid-ovate.

20. E. incarnatum.

Receptacle conic; flowers blue or violet; leaves petioled.

21. E. coelestinum.