270 COMPOSIT.E. (composite family.) 



2. p. Uved^lia, L. Roughish-hair/j, stout {A-\0° high); leaA'es broadly 

 ovate, angled and toothed, nearly sessile ; the lower palmately lobed, abruptly 

 narrowed into a winged petiole ; outer involucral scales very large ; rai/s 10-15, 

 linear-ohlonr) , much longer than the inner scales of the involucre, yellow; achenes 

 strongly striate. — Rich soil, W. New York aud N. J. to Mo., and southward. 



37. SILPHIUM, L. Rosin-weed. 



Heads many-flowered, radiate ; rays numerous, pistillate and fertile, their 

 broad flat ovaries imbricated in 2 or 3 rows ; disk-flowers apparently perfect, 

 but with entire style and sterile. Scales of the broad and flattish involucre 

 imbricated in several rows, thickish, broad and with loose leaf -like summits, 

 except the innermost, Avhich resemble the linear chaff of the flat receptacle. 

 Achenes broad and flat, dorsally compressed, surrounded by a wing notched 

 at the top, without pappus, or with 2 teeth confluent with the winged margin, 

 the achene and its subtending chaff usually falling together; those of the disk 

 sterile and stalk-like. — Coarse and tall rough perennial herbs, Avith copious 

 resinous juice, and large corymbose-panicled yellow-flowered heads. {2,i\(piov, 

 the ancient name of some resinous plant, transferred by Linnceus to this 

 American genus.) 



* Stem terete, alternate-leaved (root very large and thick). 



1. S. laciniatum, L. (Kosin-weed. Compass-Plant.) Rough-bristbj 

 throughout, stem stout (.3-12° high), leafy; leaves pinnately parted, petioled 

 but dilated aud clasping at the base ; their divisions lanceolate or linear, acute, 

 cut-lobed or pinnat(fid, rarely entire ; heads few (1 -2' broad), sessile or short- 

 peduncled along the naked summit ; scales ovate, tapering info long and spread- 

 ing rigid points; achenes broadly winged and deeply notched, 6'' long. — 

 Prairies, Mich, to Dak., and southward. July. — Lower and root-leaves ver- 

 tical, 12-30' long, ovate in outline; on the wide open prairies disposed to 

 present their edges north and south ; hence called Compass-Plant. 



2. S. terebinthinaceum, L. (Prairie Dock.) Stein smooth, slender 

 (4-10° high), panicled at the summit and bearing several or many, large 

 head?-, leafless except toward the base ; leaves ovate and ovate-oblong, some- 

 Avhat heart-shaped, serrate-toothed, thick, rough, especially beneath (1 -2° long, 

 on slender petioles) ; scales roundish, obtuse, smooth ; achenes narrowly winged, 

 slightly notched and 2-toothed. — Var. piNNATfriDUM, Gray, has the leaves 

 deeply cut or pinnatifid, but varies into the ordinary form. — Prairies and oak- 

 openings, Ohio and Mich, to Minn., and southward. July - Sept. 



* * Stem terete or slightly A-angled, leafy ; leaves undivided {not large), some 



opposite. 



3. S. trifoliatum, L. Stem smooth, often glaucous, rather slender (4 - 7° 

 high), branched above ; stem-leaves lanceolate, pointed , entire or scarcely serrate, 

 rough, short-petioled, in whorls of 3 or 4, the uppermost opposite; heads loosely 

 panicled ; achenes rather broadly Avinged, and sharply 2-toothed at the top. — 

 Dry plains and banks, Penn. to Ohio, and southward. Aug. 



4. S. Asteriscus, L. Stem hispid {2-4° high) ; leaves opposite, or the 

 hirer rarely in whorls of 3, the upper alternate, oblong or oval-lanceolate, coarsely 

 toothed, rarely entire, rough-hairy, the lower short-petioled ; heads nearly soli- 



