CARDUACEAE 1241 
b. Ray-flowers with yellow ligules: stems over 1m. 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. 
MIU less than 2 em. broad : ligules of the ray-flowers less than 2 
em. long. 
Blades of the basal leaves variously parted or pinnatifid. 
Petioles of the basal leaves shorter than the midrib; blades 
_ conspicuously veined. 4. S. venosum. 
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. 5. S. compositum. 
Leaf-blades pinnately parted or lobed: achenes'suborbicular, 
about 1 em. 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. 6. S. ovatifolium. 
Achenes 5-7 mm. broad: leaf-blades thick, often broader than 
the length of the midrib. 7. S. reniforme. 
Involucres over 2 em. broad: ligulesof 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. 8. S. rumicifolium. 
Outer bracts of the'involucre longer than broad: leaf-blades cor- 
9. S. terebinthinaceum, 
date. 
Leaf-blades pinnatifid or pinnately parted. 10. S. pinnatifidum. 
Stems typically leafy. 
Upper cauline leaves with manifestly petioledtblades. 11. S. brachiatum. 
Upper cauline leaves with sessile or essentially sessile blades. 
Leaves whorled. 
Leaves alternate or DOE 
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. 18. 
Leaves mainly crowded at the base of the stem. $ 
Leaf-blades very rough-pubescent. 
12. S. trifoliatum. 
glabrum. 
. confertifolium. 
— 
is 
mn 
Leaf-blades clasping by the cordate bases. 15. S. speciosum. 
Leaf-blades narrowed at the base. a 
Leaf-blades entire. 16. S. Elliottii. 
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 : 2: 
base. 18. S. Simpsonii. 
Stems rough-pubescent. : . 
Leaves predominatingly opposite. 19. S. Asteriscus. 
Leayes predominatingly alternate. a 20. S. angustum. 
Bracts of the involucre with pubescent surfaces as well as ciliate 
margins. 
Leaves all alternate. : 21. S, Gatesi: 
Leaves predominatingly opposite. 
|. Stem and petioles pubescent, but not shaggy. 
Stems sparingly rough-pubescent: blades of the upper 
AGO leaves narrowed at the base. 
Stems closely rough-pubescent : blades of the upper cau- 
line leaves cordate and clasping. ; 
Involuere about 2 em. broad at maturity: achenes 
narrowly winged, except at the top, the teeth 
about 3 mm. long. 
Involuere about 3 cm. broad at maturity: achenes 
broadly winged, the teeth less than 1 mm. long. 
Stem and petioles shaggy-hirsute or hispid. iat 
Bracts of the involucre merely ciliate, the inner ob- 
17. S. dentatum. 
22. S. scaberrimum. 
23. S. integrifolium. 
24. S. asperrimum. 
25. S. gracile. 
26. S. Mohrii. 
Basset the involucre shaggy-hispid, the inner acute. 
l. Silphium perfoliàtum 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- 
oon dentate-serrate with mucronate-tipped teeth : heads showy : involucres 1-2 cm. 
igh, 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- 
Talized eastward. Summer.  CUP-PLANT. 
2. Silphium albifldrum 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 
m. 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 
