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Compositaceae 429 
KK. Plants with black hairs among the white ones. E. 
C. scorpulorum Cov. 
II. Involucre bracts with stiff bristles on the back. E. 
C. barbigera Leib. 
NABALUS (Prenanthes) RATTLESNAKE-ROOT 
Perennial. Leaves mostly petioled, dentate (ours), upper often narrower. Heads 
many, 5—15-flowered (ours), in spike-like terminal panicles, involucre cylindric, usually 
narrow; chief bracts 8—10 (ours) in 1|—2 series, often with a few smaller ones outside; 
receptacle naked. Corolla purplish (ours). Akenes oblong or narrowly columnar, trun- 
cate or tapering, terete or 4—5-angled, mostly 10-ribbed. Pappus of bristles; bristles 
capillary, rigid, simple, white to reddish-brown, many. (The Latinized Indian name for 
the Rattlesnake-root.) W.C. (N. alatus.) 
N. hastatus Hel. 
HIERACIUM HAWKWEED 
Perennial. Leaves sometimes all basal. Heads solitary or corymbose or paniculate, 
5—40-flowered (ours) ; chief involucre-bracts narrow, equal or in several series of dif- 
ferent lengths, often with a few very much smaller ones outside; receptacle naked or short- 
fringed. Corolla white or yellow. Akenes oblong or columnar, glabrous, sbooth except 
for ridges, often 10-ridged or -ribbed, terete or 4—5-angled.. Pappus of capillary bris- 
tles, scabrous, white to brown, usually fragile. (Gk. hierax—a hawk; it was supposed 
to better the vision of birds of prey.) 
A. Flowers white; involucre not distinctly imbricated. W. C. E. 
H. albiflorum Hook. (White Hawkweed) 
AA. Flowers yellow. 
B. Involucre of 2 or 3 series of bracts, the outer series are successively shorter. 
C. Lower part of stem pilose; leaves usually nearly entire and narrowly lanceolate. 
E. (A. columbianum.) H. umbellatum L. 
CC. Lower part of stem glabrous; leaves usually acutely dentate and widely lanceo- 
late or ovate-oblong. W. E. 
H. canadense Michx. 
BB. Involucre of | series of bracts with only a few much smaller bracts outside. 
D. Involucre hoary with stellate hairs. U. 
H, howellii Gray 
DD.  Involucre without stellate hairs. 
E. Involucre 10—16 mm. high, with or without black hairs. 
F. Involucre without black hairs. 
G. Involucre with merely a few or no long hairs. 
-H. Stem ashy-hairy; heads |5—-40-flowered; stem leafy. 
I. Involucre more or less glandular, bracts not scarious-margined; 
i plant with long white hairs. W.C. E. (H. griseum.) 
H. scouleri griseum Nels. 
II. Involucre not glandular, bracts widely scarious-margined; plant 
without long white hairs. W. 
H. cinereum How. 
; HH. Heads 10—15-flowered; stem not leafy, glabrous or nearly so. 
(8 H. bolanderi Gray 
GG. Involucre densely long-hairy. 

