Genus 99.] 



THISTLE ^FAMILY. 



491 



1. Onopordon Acanthium L, 



Thistle. Scotch Thistle. (Fi; 



Cotton 

 4075- ) 



Onopordon Acanthium L. Sp. PI. 827. 1753. 



Biennial, white-tomentose all over; stem usu- 

 ally much branched, leafy, 3-9 high. -Leaves 

 oblong, lobed and dentate, acute, very spiny, 

 the lower often I2 / long; heads \%.'-2' broad, 

 about \Y 2 ' high, solitary at the ends of the 

 branches; outer bracts of the involucre ovate or 

 oblong, minutely serrulate, tipped with long 

 stout spreading spines; flowers pale purple; 

 achenes slightly corrugated; pappus-bristles 

 brownish, longer than the achene. 



In waste places, Nova Scotia and Ontario to New 

 Jersey and Michigan. Naturalized from Europe. 

 Native also of Asia. Called also Argentine, Asses', 

 Oat or Down Thistle, Queen Mary's or Silver 

 Thistle. July-Sept. 



100. CENTAUREA L. Sp. PI. 909. 1753. 

 Perennial or annual herbs, with alternate entire dentate incised or pinnatifid leaves, and 

 large or middle-sized heads, of tubular purple violet white or rarely yellow flowers. Involu- 

 cre ovoid or globose, its bracts imbricted in many series, appressed, fimbrillate, or dentate. 

 Receptacle flat, densely bristly. Marginal flowers usually neutral and larger than the central 

 ones, which are perfect and fertile, or flowers all perfect and fertile in some species. Corolla- 

 tube slender, the limb regular or oblique, 5-clef t or 5-lobed, the segments sometimes appearing 

 like rays. Anthers sagittate at the base. Style-branches short, somewhat connate, obtuse. 

 Achenes oblong or obovoid, compressed or obtusely 4-angled, usually smooth and shining, 

 obliquely or laterally attached to the receptacle, surmounted by a disk with an elevated mar- 

 gin. Pappus of several series of bristles or scales, rarely none. [Greek, of the Centaurs, 

 who were said to use it in healing.] 



About 350 species, mostly natives of the Old World. Besides the following, 2 others, intro- 

 duced species, occur on the Pacific Coast, and are rarely found in ballast about the eastern seaports. 

 Bracts of the involucre lacerate or fimbriate, not spiny. 



Heads 1%' broad or less; achenes laterally attached; introduced species. 

 Annual; pappus about the length of the achene. 

 Perennials; pappus obsolete, or short. 



Flowers all perfect; marginal ones scarcely enlarged. 

 Marginal flowers neutral, with palmately cleft corollas. 

 Heads 2' -4' broad; achenes obliquely attached; native western species. 

 Bracts of the involucre tipped with stout, nearly simple spines. 



i. Centaurea Cyanus L,. Blue-bottle. Corn Blue-bottle. 



(Fig. 4076.) 



Centaurea Cyanus L. Sp. PI. 911. 1753- 



Annual, woolly or tomentose, at least when 

 young; stem leafy, slender, branched, i-2% 

 ^L high, the branches ascending. Leaves linear or 

 1 linear-lanceolate, mucronate,3 / -6 / loug, the basal 

 and lower ones mostly dentate or pinnatifid, the 

 upper, or sometimes all of them, entire; heads 

 i'-i^' broad, on long naked peduncles; invo- 

 lucre campanulate, its bracts greenish-yellow or 

 with darker tips and margins, appressed, fimbri- 

 ate with scarious teeth; flowers blue or purplish, 

 varying to white, the marginal ones neutral with 

 large radiant corolla-limbs; achenes slightly 

 compressed, or 4-angled; pappus-bristles une- 

 qual, nearly as long as the achene. 



In waste places, escaped from gardens, and in bal- 

 last, Quebec to western New York and Virginia. 

 Other names are Witches'-bells or Thimbles, Corn- 

 Centaury, Corn-bottle or -binks, Brushes, Hurt- 

 sickle, Blue Bcnnets, Blaver, Blue Poppy. July-Sept. 



1. C. Cyanus. 



2. C. nigra. 



3. C. Jacea. 



4. C. Americana. 



5. C. Calcitrapa. 



Corn-flower. 



