244 COMPOSITE. Pyrrocoma. 



series, more or less subtended with foliaceoiis bracts, shorter than the disk. 

 Rays very narrow, rigid, exserted, but inconspicuous. Achenia fully a third 

 of an inch long, about the length of the rigid expanding pappus ; the bristles 

 of which are barbellate-scabrous (more so tlian the preceding), some of them 

 very obscurely thickened towards the apex. — The exterior covering of the 

 fruit, or calyx-tube, as in the whole genus, is readily separable from the 

 proper ovary. 



§2. Heads smaller and fewer-flowered : the involucre scarcely bracteate ; the 

 rays manifest, and usually fertile. — Homopappus, Nutt. (excl. spec.) 



* Heads hemispherical: involucre imbrv:oted in 2 series, shoiier than the disk: achenia 

 sparsely hirsute. 



3. P. racemosa: stem glabrous, bearing several (3-7) racemose heads at 

 the summit; the peduncles and the ovate-oblong scales of the involucre 

 pubescent; leaves glabrous, lanceolate, slightly spinulose-serrate ; the upper 

 acute, oblong-lanceolate, partly clasping ; the lower tapering to the base, 

 somewhat petioled ; corolla of the disk shorter than the pappus. — Homopap- 

 pus (Myrianthus) racemosus, Nutt. ! in trans. Avier. phil. sac. I. c. p. 332. 



Plains of the Wahlamet, Nultcdl ! — Plant 12-18 inches high. Entirely a 

 Pyrrocoma; but the heads reduced in size (less than an inch in diameter); 

 the involucre of fewer scales, and not subtended by leafy bracts ; the rays 

 (15-20) rather conspicuous and fertile ; and the achenia hairy. 



* * Heads ohoroid, sessile and often clustered : involucre as long as the disk; the scales 

 lincar-ohlong , with ^hoH distinct herhaccous lips, imbricated in several series : achenia 

 gkibrous. (Intennediate between Pyrrocoma and Aplopappus.) 



4. P. paniculata : glabrous ; stem branched at the summit ; the heads 

 sessile and somewhat clustered along the branches, about the length of the 

 bracteal leaf; scales of the involucre oblong, obtuse, mucronate ; rays 10-12, 

 slender; young achenia slightly hairy towards the summit ; leaves oblong- 

 lanceolate, mucronate, obscurely and remotely serrulate; the cauline partly 

 clasping. — Homopappus paniculatus, Nutt.! I. e. 



Plains of the Oregon near Walla-wallah, in wet jdaces, NuttalL! — Plant 

 a foot high; the leaves (entirely like a genuine Pyrrocoma) and involucres, 

 as also in the following species, often slightly covered with a resinous exuda- 

 tion. Heads numerous, more than half an inch long; the rays fertile. 



5. P.arguta: glabrous; heads axillary and terminal, clustered, sessile; 

 scales of the involucre lanceolate, acute; rays 10-12 ; leaves spatulate-lan- 

 ceolate, somewhat acuminate, sharply serrate, the cauline partly clasping. 

 Nutt. — Homopappus argutus, Nutt.! I. c. 



Plains of the Oregon, with the y)receding, Nuttall! — Very similar to the 

 following, according to Nuttall: it appears to us mOre closely to resemble the 

 preceding species. The rays in the specimens which we have examined are 

 entirely neutral. 



6. P. glomerata : glabrous ; stem simple or branched ; the heads (short) 

 clustered and disposed in an interrupted spike; scales of the involucre oblong, 

 obtuse; rays 8-10; leaves oblong-lanceolate, the lower spatulate-lanceolate, 

 very acute, mostly entire ; the cauline partly clasping. 



Plains of the Oregon, with the preceding, Nuttall! — Heads nearly as 

 broad (half an inch) as long. Rays fertile. 



