454 COMPOSITiE. Cehtaurea. 



§ 2. Scales of the ovoid- glohose involucre appendiculate ; the appendages cili- 

 ale-Jimbriate, or those of the innermost somewhat lacerate-scarious and round- 

 ish : ray-fiowers often none : pappus wanting or nearly so ! {corolla pur- 

 plish or rarely white). — Jacea, Cass. 



2. C. nigra (Linn.) : stem erect, branching ; radical leaves petioled ; the 

 cauline sessile, lanceolate, entire, denticulate, or sparingly angulate-incised 

 towards the base, scabrous ; flowers all equal and perfect ; pappus much 

 shorter than the achenium. — Fl. Dan. t. 906 ; Engl. hot. t. 278; Hook.! fi. 

 Bor.-Am. 1. p. 301 ; DC! prodr. 6. p. 571; Bigel.! fl. Bost. ed. 3. 

 p. 339. 



Newfoundland! (perhaps indigenous.) Naturalized in the eastern parts 

 of Massachusetts! July-A.ug. — H Flowers purple. Scales of the involu- 

 cre black, with a stiff pectinate fringe. 



§ 3. Scales of the ovoid or subglobose involucre surrounded by a memhrancT- 

 ceous serrate and ciliate margin : rays larger than the disk : pappus 

 double, often short: heads not bracteate. — Ctanus, Cass. 



3. C. Cy anus {Liinn.) : floccose-tomentose ; stem erect, branching ; leaves 

 linear, sessile, entire ; the lower broader, tapering into a kind of petiole, and 

 toothed or pinnatifid at the base ; pappus shorter than the achenium. 

 DC. jnodr. 6. p. 578 ; Darlingt. fl. Cest. p. 435. 



Old fields and roadsides, having escaped from gardens; sparingly natural- 

 ized in the Northern and Middle States. July-Aug. — (t) Flowers blue 

 (varying to purplish or white), or those of the disk violet. — Blue Bottle. 



§ 4. Scales of the ovoid involucre coriaceous, imbricated ; the middle ones 

 ovate, and produced into a long spine, which is naked above but sparingly 

 pectinate- spinulose at its base ; the inner oblong and toith a simple spine ; 

 the outermost spineless : rays 3-5-cleft, shorter than the disk : pappus 

 double ; the exterior rigid in several series ; the inner short, regular, con- 

 nivent {corolla yellow). — Mesocentron, DC. 



4. C. Melitensis (Linn.): stem erect, branched; radical leaves pinnately 

 parted, tapering into a petiole ; the cauline decurrent, broadly linear, toothed ; 

 heads solitary, ovate-globose, somewhat tomentose ; innermost scales of the 

 involucre acuminate-spinescent. DC. ! jnodr. b. p. 593 ; Hook. SfArn.! 

 hot. Beechey, suppl. p. 360. C. Partibilcensis, DC. I. c, fide Hook. 

 Sc Am. 



California, Douglas ! Probably introduced (as also into South America) 

 with grain from Europe. 



§ 5. Involucre ovoid ; the middle scales produced into a spine, which is pin- 

 nately spinulose at the base ; the innermost scarious at the apex : rays 

 equalling or exceeding the disk: pappus short or none {corolla purple).— 

 Calcitrapa, Cass. 



5. C. Calcitrapa (Linn.) : stem diffusely much branched, hairy ; leaves 

 sessile, pinnately lobed ; the lobes linear, acute, toothed ; heads sessile among 

 the uppermost mostly entire leaves ; spines of the involucre strong, spread- 

 ing, grooved above, with 2 or 3 small spinulae on each side at the base ; the 



