CARDUACEAE. 399 



Innermost innocuous bracts not conspicuously elongated ; their tips 

 usually crisp or twisted, sometimes erose or laciniate. 



IV. SCARIOSI. 



Innermost innocuous bracts conspicuously elongated and more or less 

 reddish, straight, neither dilated, crisp, twisted, nor erose. 



V. PULCHELLI. 



Bracts squarrose or the lower reflexed. IX. NEO-MEXICANI. 



Bracts with glandular dorsal ridge. 

 Flowers perfect. 



Leaves tomentose on both sides. VI. UNDULATI. 



Leaves glabrate above. VII. ALTISSIMI. 



Flowers dioecious. VIII. ARVENSES. 



I. VlRIDIFLORI. 



One species. i. C. Parry i. 



II. ERIOCEPHALI. 

 Anthers glabrous. 



Lobes at least of the larger leaves elliptic or ovate, obtuse ; spines of the 



bracts stout. 2. C. Osterhoutii. 



Lobes of the leaves triangular or lanceolate, acute ; spines of the bracts slender, 



yellow. 



Stem tomentose or glabrous. 

 Involucres densely arachnoid. 



Outer bracts with longer spines, almost equalling the inner ; flowers red. 



3. C. Hookerianus. 

 Outer bracts much shorter than the inner ; flowers whitish. 



4. C. araneosus. 

 Involucres sparingly arachnoid. 5. C. oreophihis. 



Stem arachnoid hairy. 6. C. scopulorum. 



Anthers pubescent. 7. C. hesperins. 



III. CARLINOIDES. 



Bracts all linear-lanceolate, not very unlike in length, with long stout flat spines. 



8. C. griseus. 

 Bracts with short weak spines ; the outer ovate or ovate-lanceolate ; the inner 



with broad dilated tips. 

 Flowers ochroleucous ; bracts not at all glandular ridged. 



Heads campanulate ; tips of the bract fimbriate. g. C. Centaureae. 



Heads hemispherical ; tips of the bracts erose. 10. C. erosus. 



Flowers red ; bracts with a more or less distinct glandular ridge. 



ii. C. perplexans. 



IV. SCARIOSI. 



Plants acaulescent or nearly so. 



Bracts all with short spines. 12. C. acaulescens. 



Bracts, at least the middle ones, with long spines equalling the disk. 



13. C. americanus. 

 Plants distinctly caulescent. 



Tips of the inner bracts usually more or less dilated ; at least the terminal 



head 3-4 cm. wide. 



Bracts thin and flat, greenish or brownish. 14. C. foliosns. 



Bracts thick and firm, yellowish, only the tips brownish, more or less rounded 



or carinate on the back, ovate. 



Divisions of the leaves broad, ovate. 15. C. coloradensis. 



Divisions of the leaves narrow, linear-lanceolate. 16. C. scariosits. 

 Tips of the inner bracts usually not at all dilated ; heads 2-2.5 cm. in diameter. 

 Bracts narrowly lanceolate, usually arachnoid-hairy, gradually tapering to 



long, flat spines. 5. C. oreophihis. 



Bracts broadly lanceolate, scarcely arachnoid with a very short spine. 



17. C. spathulatus. 



