256 American Midland Naturalist Monograph No. 7 



3. Leaves decurrent; stem glandular-pubescent; bracts acute; 



sandy soil in woods and fields, rare. July-Sept 



G. macounii Greene 



2. Stems 5-25 cm tall, diffusely branched near the base; bracts 

 brownish; achenes scabrous; dried mud, and along ditches, 



local; known from Cook and Lake counties. June-Aug 



G. uliginosum L. 



1. Heads in a narrow spike-like panicle; pappus-bristles united at 

 base, falling away in a ring; leaves glabrate above; fields and 



open woods, local. May-July. Early Cudweed 



G. purpureum L. 



Tribe 6. Inuleae 



24. Inula L. — Elecampane 



/. heleniurn L. Roadsides, fields, and open woods, occasional; in- 

 trod. from Eur. July-Aug. 



Tribe 7. Heliantheae 



25. Polymnia L. — Leaf cup 



L Leaves pinnately lobed; rays white, 2-5 mm long; achenes 3-5 



mm long, angular; woods, common. June-Nov 



P. canadensis L. 



1. Leaves palmately lobed; rays yellow, 1.5-2 cm long; achenes 6-8 

 mm long, black, flattened; woods and thickets, rare; known 

 from Alexander, Hardin, Jackson, Pope, Pulaski, and Union 

 counties. July-Sept. Bear's-foot P. uvedalia L. 



26. Silphium L. 



l.Stem 1-3 m tall, leafless or nearly so; leaves large, cordate, den- 

 tate, long-petioled ; prairie soil, common. July-Sept. Prairie- 

 dock S. terebinthinaceurn Jacq. 



1. Stem leafy throughout. 



2. Leaves pinnately parted, large, alternate; prairie soil, common. 



July-Aug. Compass-plant [S. gummiferum Ell.] 



S. laciniatmn L. 



2. Leaves toothed or entire, chiefly opposite. 



3. Leaves merely sessile, 7-10 cm long; stem nearly terete or 

 obtusely angled; prairie soil, often along railroads, com- 

 mon. July-Aug. Rosinweed [S. integrifolium var. deamii 

 Peri-y]. Occasional plants with some of the leaves whorled 

 have been mistaken for S. trifoliatum L., which is not 



known to occur in 111 .S*. integrifolium Michx. 



3. Leaves connate-clasping, perfoliate, 20-60 cm long; stem 

 sharply 4-angled; alluvial soil, common. July-Aug. Cup- 

 plant S. perjoliatum L. 



27. Parthenium L. 

 L Leaves simple, toothed; prairie soil, common. July-Sept. American 

 Feverfew P- integrifolium L. 



