Flora of the Palouse Regio?i 177 



Receptacle flat, or convex. 



Akenes very flat, winged when young. 



318. HELIANTHELLA. 

 Akenes neither very flat nor winged. 



319. HELIANTHUS. 

 Receptacle elongated, becoming columnar. 



315. RUDBECKIA. 

 Ray-akenes neither obcompressed nor laterally compressed. 



Heads few-flowered: rays short and broad. 323. blEPHARIpappus. 



Heads many-flowered: rays elongated. 317. wyethia. 



Tribe 6. HELENIOIDEAE. 



Ray-flowers none: corollas all tubular. 326. chaenactis. 



Rav-flowers present. 



Ray-flowers sterile. 328. oaillardia. 



Ray-flowers fertile. 



Iuvolucral-bracts erect, subulate-linear. 325. R1GIOPAPPUS. 



Involucral-bracts erect, oval or lanceolate. 324. eriophyllum. 

 Involucral-bracts spreading or reflexed at maturity. 



327. HELENIUM. 



Tribe 7. AXTHEMIDEAE. 



Ray-flowers none: corollas all tubular. 



Receptacle high-conical. 332. Matricaria. 



Receptacle flat to hemispherical. ^^. Artemisia. 



Ray-flowers present. 



Receptacle naked. 331. CHRYSANTHEMUM. 



Receptacle chaffy. 



Involucre narrow: rays short. 329. ACHILLEA. 



Involucre broad: rays conspicuous. 330. anthemis. 



Tribe 8. SENECIONIDEAE. 



Leaves all alternate. 335. senecio. 



Leaves all or some of them opposite. 334. arnica. 



Tribe 9. CYXAROIDEAE. 



Flowers at the margin of the head mostly sterile. 337. centaurea. 

 Flowers of the head all alike. 336. cirsium. 



293. MICROSERIS. 



Stemless or short-stemmed herbs, with milky juice: leaves 

 mostly radical, often pinnatifid: flowers yellow, the heads ter- 

 minal, on scapes or long peduncles, mostly nodding before flower- 

 ing: receptacle without chaff or bristles: pappus chaffy or plumose 

 or none: corollas in all the flowers of the head ligulate: akenes 

 8-12-ribbed. 



Pappus of 15-20 soft arid plumose bristles. M. nutans. 



Pappus of 5 flat long-awned scales. M. linearieolia. 



