COMPOSITE 19& 



Rocks on banks of etreama near Easton. July, Aug. Resembles var. Bjdtam- 

 tte, but ii destitute of ray-flowers. Beck's Bot. 



51. ARNICA, Linn. 



Nauie supposed to be a corruption of Plarmica. 



Heads many-flowered, radiate, the rajs pistillate ; thosa 

 ■f the disk tubular, perfect. Involucre canpaiiulate ; 

 scales in 2 rows, equal, lanceolate. RECEPTACLE flat, lim- 

 briilatc. AcheniA spiqdie-shaped. Pap jrnglfl 



row, consisting of rather rigid and strong! j r icu- 



late bristles. — Perennial herbs, chiefly natioes of alpine re- 

 gions, ivith simple stems, opposite leaves and yellow flowers in sin- 

 gle or corymbed large heads. 



A. nudicaults, Nutt. Leopard' s-hane. 



Hirsute ; leives sessile ; the radical leaves clustered elliptic-ovate, nerved, entire 

 or slightly tootbed; stem leaves 1 to 2 pairs, lance-ovate ; heads terminal, on loosely 

 corymbose peduncles. 



Meadows. Chester county. Dirling'on ; rare. July, Aug. Stem 1 to 2 feel 

 high, with a few peduncle-like branches at the summit, somewhat viscid. Head* 

 large; rays numerous, deep-yellow, 2 to 3-toothed at the apex; disk greenish-yci- 

 lew. 



Tribe V. CYNAREJE. Tns Thistle Tribe. 



Heals ovoid, discoid, rarely radiate, homogcontus (rarely dioecious), or lieterogm- 

 Kous, with the marginal flowers in a single series; style in the perfect Jljwsrs o/L*n 

 thickened mar the summit. 



52. CEXTAUREA, Linn. 



Named from the Centaur, Chiron. 



Heads many-flowered j the flowers all tubular, tbe mar- 

 ginal mostly falsely radiate and larger, sterile. I.WOLUCRa 

 imbricated, tbe scales margined or appendaged. Recep- 

 tacle bristly. Achenia compressed. Pappus of filiform 

 rough bristles in several series, sometimes none. — Herbs, with 

 alternate leaves, and mostly showy flowers in single heads. 



1. C. JACEA, L. Brown Knap-weed. 



Stem erect, branched; leave! linear-lanceolat; ; lower broader and toothed, pett- 

 oled; involucre globular, scales scarious and torn, the outer pinnatifid; heads rtwlv 

 ate ; pappus very short or none. 



Waste places. July, Aug. Per. Stem about 2 feet high, branching. Head) 

 with numerous purple flowers. Involucre pale brown, shining. Introduced from 

 Europe. Beck's Bot. This is probably only a variety of the next. 



2. C. nigra, L. Black Knap-weed. 



Stem erect, branched; leaves scabrous, lower angular-lyrate, petioled; upper la» 

 •eclate ; involucre globular, scales appendaged, and with a stiff black fringe ; r«e/j 

 wanting ; pappus very short. 



