COMPOSITAE. 245 



Bracts in 1-2 series; 

 rays usually narrow 



and numerous. 401. ERIGERON, 266. 



Bracts in 2-5 series; 

 rays broader, less 

 numerous. 402. ASTER, 268. 



Ray flowers yellow. 



Pappus double, the outer row 



very short. 403. CHRYSOPSIS, 271. 



Pappus in one row. 

 Heads in panicles. 



Panicle thyrsoid ; re- 

 ceptacle alveolate. 404. SOLIDAGO, 272. 

 Panicle flat-topped; re- 

 ceptacle fimbrillate. 405. EUTHAMIA, 272. 

 Heads solitary or in co- 

 rymbs. 

 Leaves all or mostly 



opposite. 406. ARNICA, 272. 



Leaves alternate. 



Heads large, 1.5 

 cm. or more 



broad. 407. HOOREBEKIA, 273. 



Heads 1 cm. or less 



broad. 

 Involucre cam- 



panulate. 408. SENECIO, 274. 

 Involucre hemi- 

 spheric or 

 broader. 

 Bracts of in- 

 volucre 8- 



10, broad. 409. CROCIDIUM, 275. 

 Bracts of in- 

 vol ucre 

 numerous, 



narrow. 401. ERIGERON, 266. 

 Pappus not of capillary bristles. 

 Receptacle chaffy. 



Pappus of scales or awns. 

 Scales of the pappus 12-20, 



thin, fringed. 410. PTILONELLA, 276. 



Scales of the pappus awn- 

 like, not chaffy. 

 Awns 2 or 4, retrorsely 



barbed. 411. BIDENS, 276. 



Awns 2, subulate. 412. COREOPSIS, 276. 



Pappus crown-like or of short 



chaffy teeth or awns. 



Rays pistillate and fertile. 413. WYETHIA, 277. 

 Rays neutral. 



Akenes flat and thin. 414. HELIANTHELLA, 277. 

 Akenes prismatic. 415. HELIANTHUS, 277. 



Receptacle not chaffy. 



Involucral bracts in several 



rows. 416. GRINDELIA, 278. 



Involucral bracts in 1 row. 



