205 
stout persistent naked rigids awnsor horns; the others shorter, thicker, 
often tuberculate-rugose, the truncate apex bearing a pair of very 
short divaricate horns or hardly any). 
1. D. parviflorus Gray. Leaves 1 to 2-ternately divided into filiform lobes, or the 
uppermost nearly simple: heads more or less pedunculate and paniculate, terminat- 
ing slender branches, in flower 2 mm. long, yellowish: longest achenes 8 mm. and 
their horns often 6 mm. long. (Heterospermum dicranocarpum Gray.)—Western 
Texas, near the Pecos. 
42. SILPHIUM L. (RosIN-WEED.) 
Coarse and tall rough perennial herbs, with resinous juice, large 
corymbose-panicled yellow and many-flowered radiate heads, nu- 
merous pistillate and fertile, perfect but sterile disk-flowers, involucral 
bracts imbricated in several rows (thickish, broad, with loose leaf-like 
summits, except the innermost, which resemble the linear chaff of the 
flat receptacle), broad and flat achenes surrounded by a wing notched 
at top, without pappus, or with 2 teeth confluent with the winged 
margin. 
* Stem from quadrangular to terete; leaves all or some of them opposite, entire or serrate: 
achenes with abroad wing. 
+ All but lower leaves sessile : stems 6 to 12 dm. high, very leafy to the top: achenes with 
a deep narrow notch. 
1. S. integrifolium Michx. Stem smooth or scabrous, sometimes rough-hispidu- 
lous: leaves entire or denticulate, lanceolate-ovate or ovate-lanceolate; all the upper 
ones closely sessile by a broad and roundish or subcordate partly clasping base, and 
tapering from below the middle to an acute apex, scabrous above, from nearly gla- 
brous and smooth to cinereous-pubescent beneath, 7.5 to 12.5 cm, long: heads some- 
what corymbose, nearly all short-peduncled: involucre over 12 mm. high: achenes 
broadly obovate, the body 8 mm, long, the scarious wing 2mm. or so wide (at least 
toward the summit.)—Prairies of Texas, at least as far west as Gillespie County. 
2. S. asperrimum Hook. Commonly taller: stem rough-hispid: leaves of the pre- 
ceding but more scabrous: heads generally larger: achenes with broader wings, the 
triangular apical portions 4 to 6 mm. high.—Plains of Texas. 
3. S. scaberrimum Ell. Stem and commonly both sides of the leaves hispid: 
leaves in remoter pairs, oblong or ovate, all but the uppermost rather coarsely ser- 
rate and with narrowed or even short petiole-like base (the larger 10 to 15 cm. long): 
heads fewer, more pedunculate: rays 2.5 cm, Jong: achenes (including broad wing) 
nearly orbicular in outline, 12 mm, in diameter.—Extending from Louisiana into 
Texas as far west as Gillespie County. 
++ Leaves rather few on the slender stem, the lower slender-petioled, often alternate : 
achenes with a comparatively shallow notch. 
4, S. gracile Gray. Hispidulous: stem3to7.5 dm. high, rather naked, terminated 
by solitary or few mostly long-pedunculate heads: leaves membranaceous, ovate- 
oblong or oblong-lanceolate, acute at both ends, denticulate; radical and lower 
cauline ample (12.5 to 22.5 cm. long); upper cauline from 1 to 5 em.long: achenes 
orbicular or very broadly oval.—Prairies of central Texas. Sometimes the leaves 
are all alternate. 
* * Stem terete, with alternate deeply pinnatifid or bipinnatifid coriaceous leaves : achenes 
with a narrow wing. 
5. S. laciniatum L. (COMPASS-PLANT.) Rough-bristly throughout: stem stout, 
9 to 36 dm. high, leafy: leaves pinnately parted, petioled, but dilated and clasping 
