326 FLOBA OF PHILADELFHIA. 



15. SERICOCAEPUS Nees. White-topped Aster. 



Leaves entire, linear, spatulate or obovate, rigid. 1. S. linifolius. 



Leaves dentate, oblong or obovate, thin. 2. S. asteroicles. 



1. Sericocarpus linifolius (L.) B. S. p. M. p. 946. Dry, usually sandy 



soil. Summer and fall. 

 Philadelphia— Germantown (Me.). Bucks— Bristol, Doylestown, A. S. 

 Martin (Fr.). Montgomery— WiWow Grove (VP.). Delaware— IJpiier 

 Darby, below Llanerch (B. Sm.), Concord (W. Tr.). C/;es<e/-— North of 

 ., Coatesville (St.). Lancaster — Pleasant Grove (Ca.). 

 New Jersey — Frequent. 

 Netv Castle — Frequent. 



2. Sericocarpus asteroides (L.) B. S. P. M. p. 946. Dry ground. Sum- 



mer and fall. 



16. ASTER L. 



A. Basal and lower leaves, or some of them, cordate and slender-petioled. 

 1. None of the stem-leaves cordate-clasping. 

 *Eays white, violet or rose. 



fRays white or rarely rose, usually two-toothed; plants not 

 glandular. 

 Involucre ovoid, canipanulate or turbinate, its bracts mostly obtuse or 

 rounded ; basal leaves few and small, or commonly none. 

 Leaves membranous or thin, smooth or nearly so. 



Heads 18-2.5 mm. broad; leaves of the branches small, obtuse or 



acute. 1. A. divaricatus. 



Heads 25 mm. broad or more ; leaves of the branches large, long, 

 lanceolate, acuminate. 2. A. tcnebrosiis. 



Leaves thick, firm, rough, at least when dry. 3. A. Claytoni. 



Involucre cylindric, its bracts tapering to an obtuse apex ; basal leaves large, 

 tufted. 4. A. Schreberi. 



jf Rays violet, usually 3-toothed ; plants glandular. 



5. A. macrophyllus. 

 **Rays blue or purple; plants not glandular. 



Heads 4-6 mm. high, numerous; bracts obtuse or obtusish. 



Leaves rough ; petioles not wing-margined ; bracts appressed. 



6. A. cordifolius. 

 Leaves smooth or nearly so ; petioles, or some of them, wing-margiued. 



7. A. Lowrieanus. 

 Heads 6-10 mm. high, numerous; bracts -acute or acuminate. 



8. A. sagittifolius. 



2. Stem-leaves, or some of them, cordate-clasping ; plant rough when 

 dry. 9. A. widulatus. 



B. No cordate and petioled leaves ; those of the stem, or some of them, with 

 more or less auricled clasping base. 



1. Stem rough or hirsute-pubescent. 



*Leaves entire, oblong, linear or lanceolate. 



Heads 2.5-5 cm. broad ; leaves sessile, strongly cordate-clasping. 

 Stem rough, leaves oblong to lanceolate ; involucre hemispheric. 

 Leaves thick, firm, very rough, oblong to oval. 10. A. yate)is. 



Leaves thin, roughish, oblong-lanceolate. 11. A. pJilogifolius. 



Stem hirsute ; leaves lanceolate ; involucre hemispheric. 



12. A. Novae- Angliae. 

 Heads 1-2.5 cm. broad ; leaves but slightly clasping. 



13. A. amethystinus. 

 **Leaves, at least the lower, serrate. 14. A. puniceus. 



2. Stem glabrous, or only sparingly jiubescent above. 



*Leaves sharply serrate. 

 Leaves tapering to the Isase. 



Leaves lanceolate to oblong-lanceolate, sessile. 14. A. puniceus. 



