312 CAEDUACEAE. 



about i as long as the body, the inner bracts 28-30 mm. long; corollas 37-40 

 mm. long. — Not very common, in thickets and fields, 



5. C. discolor (Muhl.) Spreng. Similar to C. alUssimum in habit, but seldom 

 over 20 dm. tall: leaf-blades mainly oblong-lanceolate to ovate-lanceolate, 

 densely white-tomentose beneath: outer bracts of the involucre with tips about 

 as long as the body, the inner bracts 25-28 mm. long; corollas 33-35 mm. long. 



— Rather common, in thickets and on roadsides. 



6. C. lanceolatum (L.) Hill. Stems 8-15 dm. tall, pubescent: leaves crowded; 

 blades lanceolate, 1-2-pinnatifid, grayish-woolly beneath: outer bracts of the 

 involucre gradually narrowed into slender tips, the inner bracts very narrowly 

 linear and attenuate: corollas 32-35 mm. long. — Common, in fields and on 

 roadsides. Nat. of Eu. — Common-thistle. 



7. C. horridulum Michx. Stems 3-11 dm. tall, woolly: leaf-segments with 

 spreading spines: inner bracts of the involucre 40-45 mm. long: corollas 40-48 

 mm. long, yellow : anthers mostly shorter than the filaments. — M. S. Occa- 

 sional, in low grounds, swamps and pastures. — Limestones, schists. — Yellow- 

 thistle. 



51. CAE.DUUS [Tourn.] L. Herbs resembling Cirsium in habit, usually 

 annual or biennial, the stems spiny-winged by the decurrent leaves. Heads 

 often nodding. Involucre ovoid to globose, many-flowered, its bracts narrow, 

 in many series, often partly reflexed. Filaments papillose-pubescent. Pappus 

 of many naked or merely roughened bristles. — Plumeless-thistle. 



1. C. nutans L. Biennial, pubescent: leaf -blades mostly 1-2 dm. long, pin- 

 natifid or bipinnatifid, copiously spiny-margined, scarcely paler beneath than 

 above, or sometimes pale-pubescent: head solitary, nodding: involucre hemi- 

 spheric, 2-2.5 cm. long; bracts narrow, mostly lanceolate, the outer minutely 

 spine- tipped and reflexed, the inner with softer lax tips and erect: corollas 

 purple or white, 16-20 mm. long: achenes about 3 mm. long, truncate, curved, 



— S. Eare, in fields. Nat. of Eu. — Spr. and sum. — Musk-thistle. 



52. ONOPOEDON [Vaill.] L. Annual or biennial, caulescent, coarse 

 herbs, with winged stems and branches. Leaves alternate: blades sinuate or 

 pinnatifid, spinescent, conspicuously decurrent. Heads large, erect. Invo- 

 lucre ovoid, globular, or depressed: bracts numerous, narrow, mostly spine- 

 tipped. Eeceptacle honeycombed, not bristly. Corollas mostly purple: throat 

 shorter than the slender tube : lobes narrow. Achenes short, slightly broadened 

 upward. Pappus longer than the achene, the bristles not plumose. 



1, O, Acanthium L. Plants 1.5 m. tall or less, lanate: stem-wings spiny like 

 the leaf -margins : leaf-blades mostly 1-2.5 cm. long, lanate on both sides: 

 involucres 3-4 cm. wide ; bracts firm, the inner 2-3 cm. long, the outer shorter, 

 reflexed : achenes narrowly obovoid, 4.5-5 mm. long, wrinkled. — M. Rare, 

 in fields and wate places. Nat. of Eu. — Sum. — Scotch-thistle. Cotton- 

 thistle. 



53. CENTAUEEA L. Annual (ours), or perennial, herbs. Leaves alter- 

 nate: blades entire, toothed, or pinnatifid. Heads relatively small. Invo- 

 lucre with irregularly toothed or fimbrillate outer bracts, the intermediate 

 ones, at least, often armed with spines. Anthers sagittate at the base, with 

 appendages at least i as long as the sacs. Achenes flattened or 4-angled. 

 Pappus of scales or bristles in several series, or obsolete. — Sum. — Star- 

 thistle. 



