138 PLANTS OF YELLOWSTONE NATIONAL PARK 
except near the tip. The heads are 10- to 30-flowered and the in¬ 
volucres consist of 8 to 24 principal bracts. 
Orepis scopulorum is very similar, but has scattered bristles near 
the base of the stem. 
Crepis rumdmata has been reported in the park, but is so nearly 
similar to Crepis glomca as to be scarcely distinguishable. 
Crepis subacaulis has also been reported in the park. 
Hawkweed ( Hieracium ).—The plants of this genus differ from 
those of the genus Crepis primarily in not having the bracts of the 
involucre thickened at the base or along the midrib and in having 
the pappus not pure white, but often quite brown or yellowish. 
White hawkweed (Hieracium albiflorum) differs from the other 
species of the genus in having white flowers. The stems are 2 to 3 
feet high and quite leafy near the base but nearly naked higher up. 
The lower parts of the stems and the leaves are thickly covered 
with yellowish, bristly hairs. The lower leaves are oblong, 4 to 6 
inches long and about an inch or more wide, entire or somewhat 
toothed and narrowed at the base into a winged petiole. The upper 
leaves are narrower, varying to linear. 
Hieracium gracile grows in clusters and is pale green in color. 
The slender stems are 8 to 16 inches high and each usually bears 
several heads of pale yellow flowers. The involucres are blackish- 
hairy at the base. The leaves are nearly all in basal clusters. They 
are more or less spatula-shaped, entire or nearly so, and petioled. 
Hieracium scouleri .-—Rather pale in color but strikingly hairy with 
long, crisp hairs. The stems are 1 to 2 feet high and very leafy. 
The leaves are lance-shaped, all sessile except the lowermost, and 
2 to 6 inches long. There are rather few heads and the bracts of 
the involucre are narrowly lance-shaped and in 2 or 3 series, the 
outer ones successively shorter and all covered with long, bristly 
hairs. 
Hieracium cynoglossoides is similar but the leaves are nearly 
smooth. 
Larkspur lettuce (Lactuca pulchella) .—A smooth, more or less 
waxy perennial, usually 1 or 2 feet high, with numerous linear or 
lance-shaped leaves that vary from entire to toothed or pinnately 
lobed. The upper leaves are sessile and partly clasping while the 
lower ones often have winged petioles. The heads are medium-sized 
and the flowers are blue or violet, all with strap-shaped corollas. 
Prickly sowthistle (Sonchus asper ).—A coarse, smooth, rather 
stout herb 1 to 5 feet high with prickly-toothed leaves, the upper 
sessile and clasping. The flowers are all strap-shaped and yellow. 
The plant is not native here but has been naturalized from Europe. 
Troximon .—Herbs with basal leaves and solitary heads of yellow 
or orange flowers resembling those of the common dandelion. The 
