COMPOSITAE 203 



nnoommon on dry hills, especially in the southwestern part. Jnly-Sep- 

 tember. 



2. C. palmata Nutt. Glabrous perennial, l°-3° high : leaves 3- 

 lobed to below the middle, wedge-shaped at base, sessile : pappus none 

 or of two small teeth. — Frequent on prairies and in dry woods throughout 

 the southern part. May-July. 



3. C. grandiflora Hogg. Glabrous perennial, l°-3° high : leaf divi- 

 sions oblong or linear, entire : pappus of two small teeth : achene with 

 two prominent calluses on the inner side. — Adventized around Sheffield 

 and near Courtney, Atherton and Glendale. May-July. 



4. C. tinctoria Nutt. Glabrous annual, l°-3° high : leaf divisions 

 linear, entire : pappus of a small border or none. — Locally adventized at 

 Sheffield, Independence and Courtney. June-August. 



30. BIDENS L. 

 Involucral bracts in two series, the outer usually large and foliaceoua, 

 the inner erect. Ray flowers neutral. Disk flowers perfect. Our species 

 are annuals. 



Eays large and conspicuous. 



Leaves pinnately divided. 1 . B. involucraia. 



Leaves lanceolate, serrate. 2. B. cernua. 

 Eays very small or none. 

 Leaves not pinnately divided. 



Stems purple. 3. B. connala. 



Stems straw-colored. i. B. acuta. 

 Leaves pinnately divided. 

 Aohenes oval or obovate. 



Outer involucral bracts 12-14. 5. B. vulgata. 



Outer involucral bracts 8-11. 6. B. frondosa. 



Aohenes long-linear. 7. B. bipinnata. 



1. B. iuvolucrata (Nutt.) Britten. Tickseed Sunflower. l°-3° 

 high, somewhat pubescent : leaf-divisions linear-lanceolate, serrate : outer 

 involucral scales exceeding the inner : achene with two short (1" long) 

 teeth. — Very abundant and conspicuous in low grounds. July-October. 



2. B. cemua L. Bur- marigold. 6'-30'' high, nearly glabrous: 

 leaves somewhat connate-perfoliate : heads soon nodding : aohenes with 

 usually four downwardly barbed awns. — Common along the Missouri 

 Eiver. June-November. 



3. B. connata Muhl. Beqqak's-TICKS. 6'-6° high, glabrous : leaves 

 oblong- lanceolate, serrate, more or less petioled : petioles slightly united 

 at base : flowers orange : outer involucral bracts somewhat exceeding the 

 inner : aohenes bearing 2-4 downwardly barbed awns. — Eather common 

 in moist places. June-November. 



4. B. acuta (Wiegand) Britton. Beggae's-ticks. Eesembles the 

 last : flowers greenish-yellow : outer involucral bracts leaf-like, 2-4 times 

 the length of the inner. — Common in moist places. June-November. 

 B. comosa (Gray) Wiegand, probably also occurs. 



