COMPOSITAE. 243 



Pappus of capillary bristles. 

 Involucral bracts in one 



row. 375. PETASITES, 252. 



Involucral bracts in several 



rows. 376. GNAPHALIUM, 252. 



Pappus a short crown or none. 

 Heads large, 1.5-2 cm. in 



diameter. 374. CENTAUREA, 251. 



Heads small, 5 mm. or less 



in diameter. 



Lower leaves opposite. 377. IVA, 253. 

 Lower leaves alternate. 

 Leaves entire or 



nearly so, ovate. 378. ADENOCAULON, 253. 

 Leaves incised, or 

 if entire, lanceo- 

 late or linear. 379. ARTEMISIA, 253. 

 Staminate and pistillate flowers in 



different heads. 



Pappus capillary; fertile invo- 

 lucre not bur-like. 



Leaves prickly; heads large. 387. CIRSIUM, 259. 

 Leaves not prickly; heads 



small. 



Pappus of staminate 

 flowers either club- 

 shaped or barbed at the 



apex. 380. ANTENNARIA, 254. 



Pappus of all the flowers 

 alike and neither club- 

 shaped nor barbed. 381. ANAPHALIS, 256. 

 Pappus none; fertile involucre 



bur-like. 



Bracts of staminate heads sep- 

 arate; bur large, with many 



scales. 382. XANTHIUM, 256. 



Bracts of staminate heads 

 united; bur small, with 

 1-4 scales. 

 Spines in 1 row; pistillate 



flowers 1 in a head. 383. AMBROSIA, 257. 



Spines in several rows; 

 pistillate flowers 1-4 in 



each head. 384. GAERTNERIA, 258. 



Flowers of the heads all perfect and alike. 

 Pappus of separate capillary bristles. 



Flowers whitish. 385. COLEOSANTHUS, 258. 



Flowers yellow or brownish. 



Involucral bracts in 3-4 rows. 

 Heads 2-3 mm. in dia- 

 meter. 386. CHRYSOTHAMNUS, 259. 

 Heads 20-30 mm. in di- 

 ameter. 407. HOOREBEKIA, 273. 

 Involucral bracts in 1 row or 



nearly so. 



Involucre campanulate. 408. SENECIO, 274. 

 Involucre hemispheric to 



rotate. 401. ERIGERON, 266. 



