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. 



i. Sclerolepis uniflora (Walt.) Porter. 

 Sclerolepis. Fig. 4151. 



Aethulia uniflora Walt. Fl. Car. 195. 1788. 

 Sparganophorus verticillatus Michx. Fl. Bor. Am. 2 : 98. 



1803. 



Sclerolepis verticillata Cass. Diet. 48: 155. 1827. 

 Sclerolepis uniflora Porter, Mem. Torr. Club 5: 311. 



1894. 



Perennial; stem simple, decumbent at the base, 

 erect or ascending, glabrous or slightly pubescent, 

 i-2 long, leafy. Leaves sessile, verticillate in 

 4's-6's, linear, i-nerved, 4" '-12" long, i"-i" 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. PI. 



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 S-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 I 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, i. 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 s's), or the uppermost alternate, 

 t Involucral bracts imbricated in 2 or more series, the outer shorter. 



i. 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. _ 

 Leaves oblong or lanceolate, coarsely toothed, J^' ij4' wide. 

 Bracts of the involucre obtuse, not scarious, or but slightly so. 

 Leaves linear, crowded, usually entire, obtuse. 

 Leaves lanceolate, oval, or oblong, usually dentate. 

 Leaves linear-lanceolate, acute, dentate. 

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

 Leaves lanceolate, sparingly dentate, long-acuminate. 



Leaves rounded, obtuse or truncate at the base. 

 Plant glabrous ; leaves lanceolate, long-acuminate. 

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



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



Leaves broadly ovate, crenate-dentate, mostly truncate at the base, obtusish. 14. E. rotundifolium. 



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. 17. E.resinosum. 



ft Involucral bracts in I or 2 series, all equal or nearly so. 



6. E. leucolepis. 



7. E. album. 



8. E. hyssopifolium. 



g. E. Torreyanum. 



10. E. semis erratum. 



11. E. altissimum. 



1 2. E. sessilifolium. 



13. E. verbenae 'folium. 



