280 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves mostly lanceolate or oblong and 1-4 cm. wide; plants somewhat 



glaucous. Rays blue- violet 12. A. laevis. 



Leaves mostly linear or nearly so and less than 1 cm. wide; plants not glau- 

 cous. 

 Bracts appressed, the tips acutish, the green portion very short; rays 



violet 13. A. conciunus. 



Bracts with spreading, usually very obtuse tips, the green portion extend- 

 ing nearly to the base in the outer bracts; rays blue- violet to white. 



14. A. novi-belgii. 

 Stem leaves with acute or obtuse bases, never clasping or broadened at the base. 



Leaves silky-hairy, entire. Rays purple- violet 15. A. concolor. 



Leaves never silky-hairy, entire or toothed. 

 Leaves very thick and rough, the basal ones with winged petioles; heads in 

 corymbs; disk of the head (from base of involucre to top of pappus) 11-14 



mm. long. Rays pale violet 16. A. radula. 



Leaves usually thin, never rough, without definite petioles; heads not in 

 corymbs; disk 10 mm. long or usually shorter. 

 Heads solitary at the ends of slender branches, these bearing very numerous 

 small linear bractlike leaves. 

 Bracts with rigid tips, the outer bracts very acute; leaves of the flowering 

 branchlets appressed or ascending; rays white or nearly so. 



22. A. ericoides. 

 Bracts with soft thin tips, the outer bracts obtuse; leaves of the flowering 



branchlets spreading; rays pale purple or blue 19. A. dumosus. 



Heads in broad or narrow racemes or panicles, often clustered, never solitary 

 at the ends of long and densely leafy branches. 

 Heads large, the disk 7-9 mm. long; panicles broad, not one-sided. Leaves 

 mostly lanceolate and toothed; rays white or purplish. 



20. A. pauiculatus. 

 Heads small, the disk less than 6 mm. long; panicles or racemes long and 

 narrow, often one-sided. 

 Heads in narrow panicles, these not one-sided. Leaves linear-lanceo- 

 late, sharply toothed; rays white or purplish 21. A. tradescanti. 



Heads in narrow one-sided racemes or panicles. 



Leaves mostly lanceolate and conspicuously toothed; rays white or 



bluish 17. A. lateriflorus. 



Leaves linear or lance-linear, entire or nearly so; rays white. 



18. A. vimineus. 



1. Aster divaricatus L. White wood aster. 

 Moist woods or thickets; chiefly in the region of Rock Creek and the upper Potomac; 



frequent. Au^s^.-Oct. Eastern N. Amer. 



2. Aster schreberi Nees. 



In ravines or moist woods or thickets, chiefly in the region of Rock Creek and the 

 upper Potomac. July-Oct. Eastern N. Amer. (.4. corymbosus and A. macrophyllus 

 of Ward's Flora.) 



3. Aster sliortii Hook. 



Wooded banks and islands of the upper Potomac; rare. Sept.-Oct. Pa. to Wis. 

 and southward. 



4. Aster cordifolius L. Blue wood aster. 

 Low woods and thickets; along the Potomac from Georgetown westward; common. 



Sept.-Oct. Eastern N. Amer. 



