CARDUACEAE 



1241 



b. Ray-flowers with yellow ligules : stems over 1 m. tall. 3. S. laciniatum. 



B. Leaf-blades entire, toothed or pedately parted, or if pinnately parted not 



borne on rough-pubescent stems. 

 Stems scape-like, leafless or nearly so. 



Involucres less than 2 cm. broad : ligules of the ray-flowers less than 2 



cm. long. 

 Blades of the basal leaves variously parted or pinnatifid. 



Petioles of the basal leaves shorter than the midrib ; blades 



conspicuously veined. 

 Petioles of the basal leaves longer than the midrib ; blades not 



conspicuously veined. 

 Leaf-blades pedately parted or lobed : achenes cuneate-obo- 



vate, 5-6 mm. broad. 

 Leaf-blades pinnately parted or lobed : achenes'suborbicular, 



about 1cm. broad. 6. S. ovatifolium. 



Blades of the basal leaves merely toothed. 



Achenes about 10 mm. broad : leaf-blades thin, much narrower 



than the length of the midrib. 

 Achenes 5-7 mm. broad : leaf-blades thick, often broader than 



the length of the midrib. 



Involucres over 2 cm. broad : ligules of the ray-flowers over 2 cm. long. 

 Leaf-blades merely toothed. 



Outer bracts of the involucre broader than long : leaf-blades nar- 

 rowed at the base. 



Outer bracts of the' involucre longer than broad : leaf-blades cor- 

 date. 



Leaf-blades pinnatifid or pinnately parted. 

 Stems typically leafy. 



Upper cauline leaves with manifestly petioledlblades. 

 Upper cauline leaves with sessile or essentially sessile blades. 

 Leaves whorled. 

 Leaves alternate or opposite. 



Bracts of the involucre ciliate, otherwise glabrous or nearly so. 

 Stems smooth and glabrous or essentially so. 



Leaf-blades smooth and glabrous, except the margins. 

 Leaves regularly disposed along the stem. 

 Leaves mainly crowded at the base of the stem. 

 Leaf-blades very rough-pubescent. 



Leaf-blades clasping by the cordate bases. 

 Leaf-blades narrowed at the base. 

 Leaf-blades entire. 

 Leaf -blades coarsely toothed. 



Blades of the upper cauline leaves lanceolate or 

 ovate-lanceolate, gradually or abruptly nar- 

 rowed at the base. 



Blades of the upper cauline leaves ovate, some- 

 times broadly so, half-clasping by the broad 

 base. 

 Stems rough-pubescent. 



Leaves predominatingly opposite. 

 Leaves predominatingly alternate. 

 Bracts of the involucre with pubescent surfaces as well as ciliate 



margins. 



Leaves all alternate. 

 Leaves predominatingly opposite. 



Stem and petioles pubescent, but not shaggy. 



Stems sparingly rough-pubescent: blades of the upper 



cauline leaves narrowed at the base. 

 Stems closely rough-pubescent : blades of the upper cau- 

 line leaves cordate and clasping. 

 Involucre about 2 cm. broad at maturity : achenes 

 narrowly winged, except at the top, the teeth ' 

 about 3 mm. long. 23. S. intcgrifolium. 



Involucre about 3 cm. broad at maturity : achenes 



broadly winged, the teeth less than 1 mm. long. 24. S. asperrimum. 

 Stem and petioles shaggy-hirsute or hispid. 



Bracts of the involucre merely ciliate, the inner ob- 

 tuse. 25. S. gracile. 

 Bracts of the involucre shaggy-hispid , the inner acute. 26. S. Mohrii. 



1. Silphium peifoli^tum L. Stems 1-2.5 m. tall, branching, smooth and glabrous. 

 Leaf-blades, ovate, ovate-lanceolate or lanceolate, 2-6 dm. long, or shorter above, connate- 

 perfoliate, dentate-serrate with mucronate-tipped teeth : heads showy : involucres 1-2 cm. 

 high, broader than high ; bracts ovate-lanceolate to ovate or oval, or the inner broadly 

 spatulate : ray-flowers mostly 15-25 ; ligules bright yellow, 2.5-3 cm. long : achenes obo- 

 vate, emarginate, 11-13 mm." long. 



On prairies or in moist soil, Ontario to Minnesota, Georgia, Louisiana and Nebraska. Also natu- 

 ralized eastward. Summer. CUP-PLANT. 



2. Silphium albiflonim A. Gray. Stems 3-10 dm. tall, simple or sparingly branched 

 above, zigzag, very rough with rigid prickle-like hairs. Leaf -blades ovate in outline, 1-1.5 

 dm. long, sometimes about as broad as long, very scabrous, the dilated bases of the petioles 

 entire : involucres hemispheric, 1.5-2 cm. high : involucres rather foliaceous ; bracts with 



4. S. venosum. 



5. S. compositum. 



6. S. ovatifolium. 



7. S. reniforme. 



8. S. rumidfolium. 



9. S. terebinthinaceum. 



10. S. pinnatifidum. 



11. S. brachiatum. 



12. S. trtfoliatum. 



13. S. glabrum. 



14. /S. confertifolium. 



15. S. speciosum. 



16. S. Elliottii. 



17. S. dentatum. 



18. S. Simpsonii. 



19. S. Asteriscut. 



20. S. angustum. 



21. S, Gatcsti. 



22. S. scaberrimum. 



