COMPOSITAE (COMPOSITE FAMILY) 517 
over with silvery white cotton wool. Leaves oblong lance- 
shaped, thick, irregularly lobed and toothed, decurrent on the 
stems, the margins and the broad basal wings edged with sharp, 
yellow-tipped spines. Heads terminal, solitary, large, broader 
than their height; florets purple; the outer bracts of the invo- 
lucre narrowly oblong, with slightly roughened edges, and tipped 
with spreading yellow spines. Achenes faintly ribbed, the pappus 
brownish and bristly. (Fig. 357.) 
Means of control the same as for the Common Thistle. 
PURPLE STAR-THISTLE 
Centatirea Calettrapa, L. 
Other English names: Caltrops, Maize Thorn. 
Introduced. Annual. Propagates by seeds. 
Time of bloom: June to September. 
Seed-time: August to November. 
Range: Atlantic States from Massachusetts to North Carolina; 
also on the Pacific Coast. 
Habitat: Pastures, roadsides, waste places. 
A bushy, deep green, leafy plant, one to two feet tall. ‘Leaves 
only slightly hairy, the lower ones pinnately divided into lance- 
shaped, irregularly toothed lobes, the petioles often narrowly 
winged but not decurrent; the upper ones undivided, sessile, 
slightly clasping, the teeth on all slightly spinulose but not prickly. 
Heads about an inch broad, sessile or on very short peduncles, 
terminal, or in the forks, or scattered along the branches; in- 
volucre ovoid, and all but its innermost row of bracts tipped with 
stout, sharp, light yellow, spreading spines, a half-inch to an inch 
long, each fierce pricker subtended by one to four pairs of harmless 
little spines at its broadened base. Florets all tubular, the corollas 
reddish purple, the outer row sterile, the rest perfect and fertile. 
Achenes brown, flattened, obscurely four-sided, smooth, and with- 
out a pappus. 
Means of control 
Cutting to the surface ofthe ground when in first bloom, re- 
peating the operation if the plants recover and put forth new buds. 
