CARDUACEAE 1307 



6. Carduus H611eri Small. Stem 0. 6-1 m. tall, simple or sparingly branched above, 

 somewhat floccose : leaves relatively few and distant ; blades membranous, narrowly oblong 

 or lanceolate in outline, 1-1.5 dm. long, arachnoid above, lanuginose beneath, sinuate- 

 pinnatifid, the teeth or segments spine-tipped : heads few, relatively small : involucres 

 about 2 cm. high, thinly pubescent, the outer bracts lanceolate, 3-3.5 mm. broad, each 

 tipped with a rather weak somewhat spreading spine. 



On plains or prairies, Texas. Spring. 



7. Carduus austrinus Small. Stems 4-11 dm. tall, simple or sparingly branched 

 above, rather closely floccose : leaves quite numerous ; blades thickish, narrowly oblong to 

 narrowly lanceolate in outline, arachnoid above, rather felty beneath, 1-2-pinnatifid, the 

 segments spine-tipped : heads solitary or few, relatively small : involucres about 15 mm. 

 high, sparingly pubescent, the outer bracts about 2 mm. broad, each tipped with a spread- 

 ing or recurved weak spine. 



In bottom lands, Texas. Spring. 



8. Carduus revolutus Small. Stem 0.5-2 m. tall, simple or sparingly branched 

 above, rigid, more or less floccose : leaves conspicuously narrow and often relatively elon- 

 gated ; blades leathery, 1-3 'dm. long or shorter above, glabrous or essentially so and dark 

 green above, closely white-woolly or tomentose beneath, pinnatifid, the teeth or segments 

 sometimes remote, each tipped with a rigid spine, entire or spiny-toothed : heads solitary 

 or few, relatively small : involucres 20-25 mm. high, somewhat woolly, the outer bracts 

 2-2.5 mm. broad, each tipped with a weak spreading or recurved spine : achenes 4 mm. 

 long. 



In low pine lands, South Carolina, Georgia and Florida. Summer and fall. 



9. Carduus flaccidus Small. Stem 7-16 dm. tall, sparingly floccose, almost simple 

 or sparingly branched above, slender : leaves few, remote, the basal and lower cauline, 1- 

 3 dm. long ; blades thin, narrowly oblanceolate or linear-spatulate in outline, 1-2-pinnat- 

 ifid, the segments and their teeth spine-tipped, those of the upper cauline leaves nearly 

 similar to those of the lower, but usually less deeply pinnatifid, all glabrous or essentially 

 so above, thinly gray tomentose-woolly beneath : heads relatively small : involucres about 

 1.5 cm. high, sparingly webby, the outer bracts 1.5-2 mm. broad : achenes 3.5-4 mm. long. 



In woods and on dry banks, Georgia to Arkansas and Texas. Spring. 



10. Carduus Nuttallii A. Gray. Stem 1-4 m. tall, early glabrate, winged by the 

 decurrent leaf-bases, more or less branched : leaves numerous, evenly and closely distrib- 

 uted along the stem ; blades various, those of the basal and lower cauline leaves 1.5-3.5 

 dm. long, broadly oblong or oblong-spatulate in outline, 2-pinnatifid, the segments and 

 teeth rigidly spine-tipped, those of the upper cauline leaves gradually reduced in size, 

 commonly pinnatifid, the segments often rather distant : heads relatively small : involucres 

 1.5-2 cm. high, sparingly pubescent, the outer bracts about 2 mm. broad, each terminating 

 in a spine about 1 mm. long : achenes about 4 mm. long. 



In dry soil, coastal plain, South Carolina to Florida and Mississippi. Spring and summer. 



11. Carduus altissimus L. Stem 1-3 m. tall, more or less pubescent, usually much 

 branched : leaves numerous, the basal and lower cauline 1.5-3 dm. long ; blades oblong or 

 elliptic, or broadest below or above the middle, finely or coarsely toothed, the teeth spine- 

 tipped, the upper cauline leaves smaller, mainly oblong-lanceolate, toothed like the lower 

 ones, or those on the branches pinnatifid, all sparingly pubescent above, densely white- 

 tomentose beneath : heads showy : involucres about 3 cm. high ; the outer bracts 3-4 mm. 

 broad, each terminating in a spreading or reflexed spine : achenes 4.5-5 mm. long. 



In fields and thickets, Massachusetts to South Dakota, Florida and Texas. Summer and fall. 



12. Carduus discolor (Muhl.) Nutt. Similar to C. altissimus in habit, but rarely 

 over 2 m. tall : leaf-blades mainly oblong-lanceolate or ovate-lanceolate, 1-2 dm. long, or 

 those of the basal and lower cauline leaves longer and those of the branches smaller, all 

 quite finely pinnatifid, densely white-tomentose beneath : heads showy : involucres 2.5-3 

 cm. high, the outer bracts 3-3.5 mm. broad, each with a subulate spreading or reflexed 

 tip 4-5 mm. long : achenes 3-4 mm. long. 



In fields and on hillsides, Quebec to South Dakota and Georgia. Summer and fall. 



13. Carduus lanceolatus L. Stem 1-1.5 mm. tall, rigid, more or less branched, 

 winged by the decurrent leaf-bases, pubescent : leaves numerous, often rather crowded ; 

 blades 1-2-pinnatifid, the segments and teeth rigidly spine-tipped, those of the basal and 

 lower cauline leaves 1-3.5 dm. long, those of the upper cauline smaller, lanceolate in out- 

 line, all strigose above, grayish woolly beneath : heads showy : involucre 2.5-3 cm. high, 



