DICOTYLEDONOUS PLANTS 238 
X. CENTAUREA, L. 
Herbs. Leaves entire or cut, often spiny-toothed. Heads 
single; involucre ovoid or globose (Fig. 22); bracts closely 
overlapping, entire, dry and membranaceous. Corollas all 
tubular, oblique or 2-lipped, inflated above; the outer ones 
usually larger and neutral, the inner flowers perfect; lobes 5, — 
slender. Akenes flattened. Pappus hairs short, slender, rough. 
1. C. Cyanus, L. BAcHELOR’s Button. Stem erect, slender, 
grooved, 1-2 ft. high, somewhat branched. Leaves acute, sessile, 
narrow, entire or few-lobed. Peduncles covered with cottony wool. 
Heads 3-1 in. in diameter, cobwebby. Ray-like flowers few, large, 
bright blue or pink; those of the disk smaller. Cultivated from 
Europe and escaped from gardens. 
XI. CIRSIUM, Tourn. 
Biennial or perennial; stem erect, simple or branched. 
Leaves alternate, prickly, often forming wings on the stem. 
Heads discoid, terminal and solitary or corymbed, many-flow- 
ered; bracts overlapping in many series, the outer shorter, 
usually spine-pointed; receptacle bristly. Corollas purplish 
or nearly white, the tube slender, deeply 5-cleft. Akenes 
oblong, 4-angled, smooth or ribbed. _Pappus of numerous 
simple or plumose bristles.* 
1. C. altissimum, Spreng. Tatu Tuistie. Perennial or bien- 
nial; stem stout, very leafy, downy or woolly, branched 4-10 ft. 
high ; leaves rough-downy above, hoary beneath, fringed with fine 
prickles, not forming wings on the stem, the lower petioled and 
often pinnately cut, the upper sessile and entire. Heads ovoid, 1 in. 
in diameter ; bracts viscid, webby when young, all except the inner 
ones tipped with weak and spreading bristles. Flowers light purple. 
Common in fields, woods, and waste places.* 
2. C. horridulum, Michx. Yrttow TuisTie. Biennial or peren- 
nial ; stem erect, stout, woolly when young, becoming smooth, often 
purple, branched 1-3 ft. high. Leaves pinnately cut, with very 
spiny teeth, mostly sessile and clasping, smooth and green on both 
sides. Heads large, surrounded by a whorl of linear-oblong, comb- 
like leaves ; involucral bracts linear, ciliate, not spine-tipped. Flowers 
purple or yellowish. On sandy soil E. and S.* 
