750 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
None of the bracts dilated at the apex, all with long- 
attenuate tips, conspicuously arachnoid, in 
Many seriesS........ 2222-22-22 2 eee ee ee eee 3. CO. pallidum. 
At least some of the bracts dilated at the apex, not 
conspicuously arachnoid, often nearly gla- 
brous, in few series. 
Inner bracts conspicuously elongated, with 
narrow, mostly coriaceous tips; heads 
small, 2 cm. broad, mostly clustered at 
the ends of the branches................ 4. C. inornatum. 
Inner bracts not conspicuously elongated, with 
broad green tips; heads large, 3cm. broad, 
mostly solitary..............2.22+2..... 5. O gilense. 
None of the bracts pectinate-ciliate; flowers variously 
colored. 
Bracts not with a dorsal glandular ridge. 
Bracts squarrose, at least the lower reflexed; largest 
heads 6 to 7 cm. in diameter................ 6. O. neomexicanum, 
Bracts not squarrose, all erect or appressed; heads 
all less than 5 cm. in diameter. 
Style produced at the tip only 4 to 6 times its 
diameter above the conspicuous node; 
corollas bright carmine; leaves tomen- 
tose on both sides..................--. 7. O. arizonicum, 
Style produced many times its diameter be- 
yond the inconspicuous node; corollas 
purplish or whitish; leaves glabrate, at 
least above. 
Inner bracts much elongated, the tips not 
dilated; heads small, 2 em. in di- 
ameter or less.... 2. ......0222..004 8. C. pulchellum. 
Inner bracts but little elongated, some- 
what dilated at the tips; heads large 
or small. 
Flowers purplish; heads small, about 
2 cm. in diameter, solitary; in- 
ner bracts with purple tips..... 9. C. wheeleri. 
Flowers whitish; heads larger, mostly 
3 to4cm. broad, clustered at the 
ends of the branches; bracts not 
with purple tips............2.- 10. OC. coloradense. 
Bracts with a dorsal glandular ridge. 
Bracts scabrous-ciliate, purplish.................. 1l. OC. grahami. 
Bracts not scabrous-ciliate, usually not at all pur- 
plish. 
Plants glabrate. 
Stems winged below; leaves thin, usually 
merely dentate with weak spines; 
heads broadly campanulate........ 12. OC. wrightii. 
Stems not winged ; leaves thick, pinnatifid, 
with stout spines; heads narrowly 
campanulate...................... 13. OC. calcareum. 
