COMPOSITE. 



471 



2. Greater C. 



3. Corn C. 



4. Jersey C. 



enlarged outer florets, the most prominent character of the genus, are 

 seldom deficient, and that chiefly in a common variety of our own black 

 Centaurea. In that case the fringed involucral bracts as readily indi- 

 cate the genus. 



Involucres not prickly, or with very small prickly points 

 to the bracts. 

 Involucral bracts with a broad, black, or brown fringed 

 border or appendage. 

 Leaves mostly entire or toothed. Appendages almost 



concealing the bracts themselves 1. Blade C. 



Leaves deeply pinnatifid. Involucral bracts showing 

 their green centres with a black fringed border 

 Involucral bracts ending in, or bordered by, minute 

 teeth or prickles. 

 Outer florets bright blue. An erect cornfield annual 

 Florets purple. A spreading Jersey perennial . . 

 Involucral bracts ending in a long, stout prickle. 



Florets purple 5. Starthistle C. 



Florets yellow 6. Yellow C. 



The C. montana, from central and southern Europe, and a few others, 

 are occasionally cultivated in our gardens. 



1. Black Centaurea. Centaurea nigra, Linn. (Fig. 564.) 

 (Eng. Bot. t. 278 ; C. nigrescens, Brit. Fl. Knajptveed or Hardheads.) 



A perennial, with erect stems, hard 

 and branched, 1 to 2 feet high. Leaves 

 from linear to lanceolate or oblong ; the 

 upper ones entire or nearly so, clasping 

 the stem at their base ; the lower with 

 a few coarse teeth or short lobes ; all 

 green, and rather rough with a few mi- 

 nute hairs, or slightly cottony under- 

 neath when young. Involucres globular, 

 on terminal peduncles ; the bracts closely 

 imbricate, so as only to show their ap- 

 pendages, which are brown or black, 

 and deeply fringed, except on the inner- 

 most bracts, where they are shining and 

 usually jagged. Florets purple, either 

 all equal or the outer row much larger 

 and neuter as in the rest of the genus. 

 Achenes slightly hairy, often apparently 

 without any pappus, but really crowned 

 by a ring of very minute scaly bristles, occasionally intermixed with 

 a few longer, very deciduous ones. 



Fig. 564. 



