1308 CAKDUACEAE 



the outer bracts 2-2.5 ram. broad, all terminating in spines: achenes 3.5-4 mm. long. 

 In waste grounds, fields and pastures, Newfoundland to Minnesota, Florida and Kansas. Native 

 of Europe and Asia. Summer and fall. 



14. Carduus pinetorum Small. Stem 4-9 dm. tall, mainly simple, thinly pubes- 

 cent, especially at the nodes : leaves few on the stem ; blades glabrous or nearly so above, 

 thinly woolly beneath, those of the basal and lower cauline 1-2 dm. long, spatulate-oblong 

 or narrowly oblong in outline, 1-2-pinnatifid, the segments and teeth spine-tipped, those 

 of the upper cauline leaves smaller and narrower than those of the lower, the terminal 

 spines of the segments directed forward : involucre 3-3.5 cm. high, the inner bracts much 

 surpassing the subtending leafy spine-armed involucre : achenes 5-5.5 mm. long. 



In pine lands, between the everglades and Biscayne Bay, Florida. Spring to fall. 



15. CarduuB spinosissimus Walt. Stem 3-11 dm. tall, woolly at least when young, 

 simple or sparingly branched : leaves thinly pubescent on both sides, but rather green ; 

 blades various, those of the basal and lower cauline spatulate or oblong-spatulate in out- 

 line, 1-4 dm. long, 2-pinnatifid, the segments and teeth rigidly spine-tipped, those of the 

 upper cauline smaller, oblong to lanceolate in outline, often 1-pinnatifid, the spines ter- 

 minating the segments spreading : involucres 3.5-5 cm. high, the inner bracts surpassed 

 by the spine-armed leafy bracts of the involucre : disk yellow : achenes 5-5.5 mm. long. 



In dry or moist sandy soil, Maine to Florida and Texas. Spring to fall. The form with purple 

 corollas is C. spinoinssimus EUidttii (T. & G.) Porter. 



145. CENTAUREA L. 



Annual or perennial caulescent herbs. Leaves alternate : blades entire, toothed or 

 pinnatifid. Heads sometimes homogamous. Involucres globose to ovoid : bracts in several 

 series, appressed, irregularly toothed or fimbrillate. Receptacle flat, densely bristly. 

 Flowers various, either all perfect and fruit-producing, or the marginal ones larger and 

 neutral. Corollas with slender tubes and regular or oblique limbs, violet, purple, white or 

 rarely yellow. Anthers sagittate at the base. Stigmas obtuse. Achenes flattened or ob- 

 tusely 4-angled, smooth, obliquely or laterally attached. Pappus of several series of bristles 

 or scales, or rarely obsolete. Our species are annuals. The plants flower from spring to fall. 

 STAB THISTLE. 



Bracts of the involucre, at least the intermediate ones armed with spines. 



Stems woolly : pappus present and double. 1. C. solstitialis. 



Stems more or less pubescent, not woolly : pappus obsolete. 2. C. Calcitrapa. 



Bracts of the involucre with pectinate-fimbrillate appendages. 3. C. Americana. 



1. Centaurea solstitialis L. Stems 3-6 dm. tall, more or less woolly, often widely 

 branched : leaf-blades various, those of the basal leaves 1-2 dm. long, lyrate-pinnatifid, 

 those of the stem-leaves shorter, oblong-lanceolate or linear, entire or somewhat toothed, 

 decurrent on the stem as narrow wings : heads sessile : involucres subglobose, 5-10 mm. in 

 diameter ; bracts various, the outer with palmate prickles, the inner ones with scarious tips, 

 the intermediate ones with long spreading spines each of which often have 1 or 2 spinules 

 at their base : corollas yellow : pappus double. 



In waste places and on roadsides, adventive in the southern United States. Native of Europe. 



2. Centaurea Calcitrapa L. Stems 3-4 dm. tall, much branched, more or less 

 pubescent, but not woolly : leaf-blades various, those of the basal and lower cauline 1-2 

 dm. long, 1-2-pinnatifid, the segments or teeth spinulose, the upper cauline leaves smaller 

 and less divided : heads sessile : involucres ovoid, 8-10 mm. high : outer bracts terminating 

 in short spreading spines, the intermediate in long spines pinnate at the base, the inner 

 erose at the apex : corollas purple, none of them radiant : pappus obsolete. 



In waste places, Massachusetts to North Carolina. Also on the Pacific coast. Native of Europe. 



3. Centaurea Americana Nutt. Stems 5-18 dm. tall, striate-ridged or channeled, 

 often simple, glabrous or nearly so : leaf-blades oblanceolate, oblong or linear-lanceolate, 

 2-8 cm. long, acuminate or mucronate, entire or remotely denticulate, sessile : heads 

 showy : involucres hemispheric, 1.5-2.5 cm. high ; bracts numerous, pectinate-fringed : 

 neutral -flowers forming a conspicuous ray by their narrowly linear lobes, these 1.5-2.5 cm. 

 long : perfect flowers forming a disk 2.5-8 cm. broad : corollas pink or deep rose-colored : 

 achenes 5-6 mm. long, hairy : pappus of unequal bristles surpassing the achene in length. 



On plains and prairies, Missouri to Louisiana, Texas, Arizona and Mexico. 



146. CNICUS L. 



Annual caulescent pubescent herbs. Leaves alternate: blades sinuate-toothed or 

 pinnatifid, with spiny teeth or segments. Heads homogamous, solitary and sessile at the 



