FLOWERING PLANTS AND FERNS OF ARIZONA 239 



Key to the species 



1. Plants annual or biennial, without a woody caudex (2). 



2. Involucres all sessile and solitary in the forks of the stems and along the 

 branches (3). 

 3. Plant without tomentose or lanate pubescence; involucres turbinate-cam- 

 panulate; perianth lobes oblong or ovate (4). 

 4. Stems and leaves puberulent or short-pilose with subappressed hairs; 

 involucres cleft to about the middle, glabrous or nearly so; peri- 

 anth yellow, hispidulous and often glandular; stem leaves foliaceous 

 but smaller than the basal ones, subtended by small triangular 

 bracts 1. E. divaricatum. 



4. Stems and leaves silky pubescent ; involucres clef t nearly to the base, seri- 



ceous; perianth pink, glabrous or nearly so; stem leaves all greatly 



reduced, bractlike 2. E. puberulum. 



3. Plant with tomentose or lanate pubescence, at least on the basal leaves; 



involucres narrowly turbinate or cylindric, short-toothed, strongly 



ribbed; outer lobes of the perianth wedge-shaped or fan-shaped, 



truncate or very obtuse, constricted near the base (5). 



o. Stems not more than 30 cm. long and usually much shorter, diffusely 



many-branched; involucres not more than 1.5 mm. long, loosely 



and rather sparsely lanate-tomentose; herbage lanate-tomentose; 



cauline leaves greatly reduced, bractlike (6). 



6. Plant intricately branched, the branches more or less incurved at 



maturity : perianth usually pale yellow 3. E. xidularium. 



6. Plant more open, the branches spreading or ascending at a rather 



wide angle; perianth white or pink 4. E. dexsum. 



5. Stems seldom less than 30 cm. long, the branches few, ascending; 



involucres 2 to 3 mm. long, glabrous except on the margins; perianth 

 white or pink (7) . 



7. Plant scapose, the scapes glabrous; cauline leaves reduced to bracts, 



the basal leaves with orbicular, subcordate blades; involucres not 

 very numerous, 2.5 to 3 mm. long, cylindric-turbinate, their 



margins glabrous or very nearly so 5. E.vimixeum. 



7. Plant not scapose, the stems leafy above the base, white-tomentose; 

 lower cauline leaves large, with blades oblong-obovate or 

 oblanceolate, cuneate or attenuate at base; involucres very 

 numerous, about 2 mm. long, short-turbinate, their margins 



white-lanate 6. E. polycladon. 



2. Involucres all or some of them peduncled, except sometimes in E. hookeri (8). 



8. Plants not scapose, the stems leafy (except rarely in E. angulosum) , the 



lower stem leaves like the basal ones but smaller (9) . 



9. Stem leaves subtended by small triangular bracts; peduncles seldom 



more than 2 cm. long; involucre and perianth glandular-puberulent 



externally; plant more or less white-floccose; stems sharply angled; 



involucre hemispheric, many-flowered; perianth white or pink. 



7. E. ANGULOSUM. 



9. Stem leaves not subtended by bracts; peduncles often at least 3 cm. 

 long; involucre and perianth not glandular (10). 

 10. Involucres parted or divided, glabrous; perianth yellow, hispidulous 

 externally, with narrow, attenuate lobes; stems and leaves 

 glabrous; leaf blades oblanceolate to linear; peduncles filiform. 



8. E. SALSUGINOSUM. 



10. Involucres deeply cleft but not parted or divided, pubescent; 

 perianth usually white or pink, sometimes yellowish, glabrous 

 externally, with broad outer lobes, the inner ones much narrower 

 and longer; steins and leaves more or less pubescent (11). 

 11. Leaf blades villous, those of the lower stem leaves oblong-lanceo- 

 late to broadly ovate, flat; outer lobes of the perianth nearly 



orbicular, cordate, not saccate at base 9. E. abertiaxum. 



11. Leaf blades conspicuously white-lanate beneath, all linear- 

 lanceolate or linear-oblanceolate, more or less revolute; outer 

 lobes of the perianth ovate, bisaccate at base. 



10. E. PHARXACEOIDES. 



!S6744°— 42 10 



