GENUS 3. THISTLE FAMILY. 355 
3. SCLEROLEPIS Cass. Bull. Soc. Philom. 1816: 198. 1816. 
: Slender aquatic herbs, with linear entire verticillate leaves, and solitary (rarely 2-4) dis- 
coid peduncled terminal heads of small purplish flowers. Involucre broadly campanulate or 
hemispheric. Bracts imbricated in about 2 series. Receptacle conic, naked. Corolla regular, 
its tube short, its limb campanulate, 5-lobed. Anthers obtuse at the base. Style-branches 
slender, obtuse. Pappus of 5 broad cartilaginous obtuse scales. Achenes 5-angled. [Greek, 
hard scale, referring to the pappus.] 
A monotypic genus of eastern North America. 
1. Sclerolepis uniflora (Walt.) Porter. 
Sclerolepis. Fig. 4151. 
Aethulia uniflora Walt. Fl. Car. 195. 1788. 
Spar ganophoras verticillatus Michx. Fl. Bor. Am, 2: 98. 
1803. 
Sclerolepis verticillata Cass. Dict. 48: 155. 1827. 
Saar uniflora Porter, Mem. Torr. Club 5: 311. 
1894. 
Perennial ; stem simple, decumbent at the base, 
erect or ascending, glabrous or slightly pubescent, 
1°-2° long, leafy. Leaves sessile, verticillate in 
4’s-6’s, linear, I-nerved, 4-12” long, 3-1” wide, or 
the submerged ones filiform; head about 5” broad; 
bracts of the involucre linear-oblong, acutish, usually 
puberulent. 
In shallow ponds and streams, New Hampshire to 
Florida. July-Sept. 
4. EUPATORIUM [Tourn.] L. Sp. Pl. 
836. 1753. 
Erect, mostly branching, perennial herbs, with opposite or verticillate, or sometimes alter- 
nate, 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 imbri- 
cated 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 t 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 cannd- 
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. 
f 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, %4’-114’ 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-oblong, rounded or narrowed at the base, usually obtuse. 13. E. verbenaefolium. 
Leaves broadly ovate, crenate-dentate, mostly truncate at the base, obtusish. 14. E. rotundifolium. 
Leaves ovate, dentate, acute. 15. E. pubescens, 
pb. Leaves clasping or connate-perfoliate at the base. 
Leaves connate-perfoliate ; involucral bracts acute. 16. E. perfoliatum,. 
Leaves merely clasping ; involucral bracts obtuse. 17. E.resinosum. 
tt Involucral bracts in 1 or 2 series, all equal or nearly so. 
