702 COMPOSITAE 
8. C. nutans, L. (Fig. 1, pl. 199.) Musx Tnistir. Biennial. Leaves 
lance-shaped, broad and often eared at base, extending down the stem. 
Lobed and very prickly; the stem also armed with strong prickles. Heads 
solitary, drooping. Occasional in our area, introduced from Europe. 
July-Oct. 
9. C. crispus, L  Curtep Tuistre. Biennial. Plant somewhat 
woolly; stem densely prickly, 2 to 4 ft. high. Leaves with triangular 
lobes, margins prickly. Heads crowded on very short stems. Introduced. 
July-Sept. 
52. ONOPORDON, L. 
A stout thistle similar to Carduus, but the receptacle is honeyecombed 
and not bristly. The hairs of the aigrette or pappus are not plumose. 
O. acanthium, L. (Fig. 4, pl. 198.) Scorcu Tuistir. Stout, 2 to 
4 ft. high, the stem winged, the wings armed with stout prickles Leaves 
white-woolly, oblong, lobed, armed with very strong prickles. Heads soli- 
tary, the involucre broad at base, constricted above, flowers spreading, 
light purple. Fields, most of our area. July-Sept. 
53. CENTAUREA, L. 
Herbs with alternate leaves which are entire or more or less cut. Heads 
usually solitary, terminal, with tubular flowers. Involucre globose, of 
overlapping bracts, Receptacle flat, bristly. Marginal flowers usually 
much larger than the central, sterile or fertile. Aigrette of several scales 
or bristles or absent. 
Leaves linear . Pures ren cpt ee. (OWT 
Leaves lance- shaped, spatula- shaped or oblong. 
Leaves not deeply lobed. 
Marginal flower much larger than etal 3 UN as Gee 
Marginal flowers not mia than central << "= - C. mera 
Leaves deeply lobed . . . Aire rey ke Be oh calcitrapa 
l.. ©. Cyanus,) i Fig. 4, pl. 199.) — hang: An introduced 
plant from Europe where it is found in grain fields; here cultured in 
gardens from which it has escaped. Plant 1 to 23 ft. high, somewhat 
woolly, leaves alternate, linear. Heads solitary at end of branches. Invo- 
lucre globular, the scales fringed on the margin. Flowers blue varying 
to purplish, the marginal ones large thin lobes, assuming a star-like form, 
Waste places and grain fields. July-Sept. 
2. C.nigra, L. (Fig. 3, pl. 199.) KNapweep. Perennial roots. 
Stem stiff, branched, 1 to 2 ft. high. Leaves lance- or spatula-shaped, the 
margins entire or the lower leaves slightly lobed. Heads about 1 in. 
broad; scales of the involucre with a black hairy fringe. Marginal and 
central flowers of the same size, purple. Naturalized, in waste places. 
July-Sept. 
3. C, Jacea, L. (Fig. 2, pl. 199.) Rayrep Knapweep. Like the last, 
but margins of leaves are toothed and outer flowers are large and showy. 
Naturalized to some extent. June-Sept. 
4. C, calcitrapa, L. Srar Tuistie, Leaves deeply (pinnately) lobed 
often with somewhat prickly spines at margins. Heads immediately sup- 
ported by leaves which assume somewhat the form of a sub-involucre. 
