276 COMPOSITAE. 



Crocidium multicaule Hook. Woolly when young but soon glabratc; 

 stems numerous, tufted, 5-25 cm. high; radical leaves in a basal tuft, obovate 

 or spatulate, few-toothed, sessile or short-petioled ; cauline leaves small, 

 linear; heads slender-peduncled, small but showy; involucral bracts oblong- 

 ovate. Foothills of the Blue Mountains, Homer. 



410. PTILONELLA.' 



Annuals; heads rather few-flowered; ray-flowers 3-6, short 

 and broad, pistillate; disk-flowers 7-12, perfect, some of the 

 central sterile; involucral-bracts 6-10, nearly in one row; recep- 

 tacle convex, chaffy; pappus of 10 or 12 linear hyaline scales, 

 each with a stout awn-like midrib, rarely wanting; ray-akenes 

 neither obcompressed nor laterally compressed. 



Ptilonella scabra (Hook.) Nutt. Erect, branched above, 10-20 cm. high, 

 scabrous-puberulent below, sometimes glabrous above; leaves numerous, 

 attenuate, linear, somewhat involute, 1-2 cm. long; heads few, somewhat 

 corymbed, terminating leafy branches; involucre 5-6 mm. high; ray and disk 

 flowers white; anthers purple. In thin soil, locally abundant. 



411. BIDENS. BEGGAR TICKS. 



Annual or perennial herbs; leaves opposite; heads small or 

 medium, yellow or sometimes white; ray-flowers 3-10, sterile or 

 none, in which case the flowers are all perfect and tubular; 

 receptacle chaffy; pappus of 2-4 rigid backwardly-barbed awns; 

 ray and disk-akenes obcompressed. 



Rays none; leaves pinnately 3-5-divided. B. vulgata. 



Rays conspicuous; leaves lanceolate, serrate. B. cernua. 



Bidens vulgata Greene. Annual, the stems erect, usually branched above, 

 glabrous, 30-90 cm. high; leaves pinnately 3-5-foliolate, petioled; leaflets 

 lanceolate, acute, serrate, abruptly narrowed at the base; heads 15-25 cm. 

 broad, stout-peduncled; involucre broadly campanulate, the outer 10-16 

 bracts foliaceous, linear, unequal, much exceeding the brownish scarious- 

 margined inner ones; ray flowers none; akenes flat, obovate, 7-9 mm. long, 

 somewhat pubescent, ciliate on the margins; awns 2, half as long as the akene, 

 retrorsely barbed. Common along Snake River. 



Bidens cernua L. Annual, glabrous or minutely hispid; stems erect, simple 

 or with few short branches, 30-60 cm. high; leaves linear-lanceolate to lanceo- 

 late, coarsely and unequally serrate, acuminate, sessile and somewhat cuneate 

 at base, 6-12 cm. long; heads short-peduncled, 12-15 mm. broad; outer in- 

 volucral bracts foliaceous, much longer than the membranous inner ones; 

 rays 6-12, bright yellow, or sometimes absent; akenes elongate, wedge-shaped, 

 4-angled and bearing 4 backwardly barbed awns half as long as the body. A 

 very variable species growing in wet places, blooming in autumn. 



412. COREOPSIS. 



Annual or perennial herbs usually with opposite leaves; heads 

 many-flowered, radiate; involucre of 2 rows of about 8 bracts 

 each, the outer spreading and foliaceous, the inner appressed and 



