463 COMPOSITE, (composite family.) 



72, CEXTAUREA, L. Star Thistle. Centaurea. Sliaul-ed- 



Darddr. 



Heads heterogamous, the marginal flowerets sterile, rarely homo- 

 gamous. Inv^olucre imbricated, scales in several rows, leathery or 

 membranous, spiny or unarmed, entire, ragged, or fringed. Receptacle 

 bristly. Anthers caudate at base ; filaments papillose. Akeues general- 

 ly smooth ; hilum lateral ; pappus persistent (rarely 0), of two forms, 

 the outer consisting of several rows of bristles or pales, the inner of 

 one row of connivent pales — Perennial, biennial, or annual herbs. 



I. Scales of involucre obtuse, or ending in a tender cusp, with a trans- 

 lucent, eroded or fringed, but not ciliate margin. Floioerets rayed. Peren- 

 nials. 



1 C. pergamacea. 



n. Scales of involucre ending in a pectinate-ciliate, mucronate a2)pen- 

 dage which is not decurrent. Flowers not radiate. Perennials. 



3 C. Cassia. 



III. Scales of involucre with a scarious, pectinate-fringed, decurrent 

 margin. Flowers blue or 'oiolet, .03 to .035 broad. 



* Annuals. Akenes bald or pappose. 



3 C. Cyanus, 4 depressa, 5 cyanoides. 



* ^Perennials. Akenes pappose. 



6 C. axillaris. 



IV. Scales of involucre white-ciliate, ending in a weaTc prickle. Heads 

 ohlong, less than .01 lojig. Annuals. 



7 C. Ammocyanus, 8 laxa. 



V. Stems and branches rigid. Heads oblong -cylijidrical, .008 to .015 

 hng., .003 to .005 broad; scales of involucre loith a narrow, membranous, 

 pectinate fringed margin, more or less decurrent, and ending in a point or 

 short prickle, shorter or someichat sti^onger and longer than the lateral 

 fringes. Biennials or perennials. 



9 C. virgata, 10 leptocephala, 11 aggregata, 13 dumulosa 

 13 Damascena. 



VI. Heads from .015 to .05 in diameter. Scales of involucre scarious 

 or leathery indurated, fringed above, rarely entire, usually ending in a 

 long, stout, prickly spine. Perennials. 



* Plants with stems, usually tall. Leaves not decurrent. 



14 C. Antiochia, 15 speciosa, 16 eryngioides, 17 carduiformis, 

 18 thrincisefolia, 19 Urvillei. 



* * Plants with tall stems. Stem-leaves more or less decurrent. 



t Flowerets purple. 



20 C. arifolia, 31 Cataonica, 33 spicata, 33 Haussknechtii, 



34 Doddsii, 35 foliosa. 



1 1 Flowerets yellow. 



26 C. onopordifolia. 



