274 CONTRIBUTIONS FROM THE NATIONAL HERBAEIUM. 



Leaves lance-linear, many of them in whorls of 3, the larger ones 7-12 mm. 

 wide, the lateral nerves not very conspicuous 10. E. torreyanum. 



Leaves lanceolate or narrowly lanceolate, opposite, the larger ones mostly 

 12-20 mm. wide, the lateral nerves very conspicuous. 



11. E. altissimum. 

 Leaves obtuse to truncate at the base, the blades broadest at or near the base. 

 Leaves glabrous beneath, often 5 times as long as broad, very long-tapering 



at the apex; bracts obtuse 3. E. sessilifolium. 



Leaves pubescent beneath, the blades less than 3 times as long as broad, the 

 larger ones never very long-tapering at the apex, usually obtuse or acute; 

 bracts acute or acutish. 

 Leaves mostly 2.5-3 times as long as broad, ovate, ovate-oblong, or lance- 

 oblong, ^^dth few coarse iiTegular teeth; leaves of the inflorescence 



alternate 5. E. verbenaefolium. 



Leaves less than twice as long as broad, broadly ovate or rounded-ovate, 

 with numerous close even teeth, or the lower leaves sometimes irregu- 

 larly lobed; leaves of the inflorescence all or nearly all opposite. 

 Leaves broadly ovate, acute or acutish, the larger ones 6-9 cm. long, 



usually rounded at the base 6. E. pubescens- 



Leaves rounded-ovate, usually obtuse, the larger ones mostly 3-5 cm. 

 long but sometimes longer, usually truncate at the base. 



7. E. rotundifolium. 



1. Eupatorium purpureum L. Joe Pye weed. 

 Low wet ground or in moist woods or ravines; frequent. Aug. -Sept. Eastern N . 



Amer. {E. trifoliatum L.) 



A somewhat variable species. In shaded woodlands the plants have thinner, 

 sparsely pubescent leaves. The common form, of exposed situations, has thicker, 

 more pubescent leaves, but does not differ essentially from the woodland form. It is 

 E. purpureum maculatum (L.) Darl. {E. maculatum L.). 



2. Eupatorium perfoliatum L. Boneset. 

 Low wet ground ; common. Aug. -Sept. Eastern U. S. 



The leaves are usually opposite, but sometimes in whorls of 3. 



3. Eupatorium sessilifolium L. Upland boneset. 

 Wooded hillsides; common. Aug.-Sept. Eastern U. S. 



In specimens collected near Takoma Park by Steele the leaves are very shortly 

 petiolate, and obtuse, rather than rounded, at the base. 



Ward reported a hybrid between this species and E. pubescens. This form, which 

 is represented by several specimens, has pubescent leaves intermediate in shape 

 between those of the two species. In the key it is likely to fall under E. verbenae- 

 folium, from which it is distinguished by the thinner, closely and evenly serrate 

 leaves. 



4. Eupatorium album L. 



Dry fields; common, especially on the Coastal Plain. July-Sept. Eastern U. S., 

 northward to Long I si. 



5. Eupatorium verbenaefolium Michx. 



Low ground, often in sphagnimi bogs, or in dryish fields; Coastal Plain. Aug.-Sept. 

 Eastern U. S. (E. teucrifolium Willd.) 



6. Eupatorium pubescens Muhl. 



Woods; chiefly along the upper Potomac, but also on the Coastal Plain. Aug.-Sept. 

 Eastern U. S. 



Closely related to E. rotundifolium; some specimens can be placed almost equally 

 well in either species. The lowest leaves are often deeply lobed in both species. 



