1032 FLORA. 



spatulate, sessile, or somewhat clasping, not decurrent, spinulose-margined, entire, 

 lobed or pinnatifid into triangular-lanceolate lobes, the lower sometimes 2 dm. 

 long and 5 cm. wide, narrowed into margined petioles, all pubescent or gla- 

 brate above, and densely white-tomentose beneath; heads long-peduncled; outer 

 bracts of the involucre not coriaceous, lanceolate or ovate-lanceolate, tipped with 

 weak short bristles; flowers purple. In dry woods and thickets, Va. to Ky., Ohio, 

 Fla. and Tex. April-Sept. 



6. Carduus Pitcher! (Torr.) Porter. PITCHER'S THISTLE. (I. F. f. 4062.) 

 Biennial, persistently white-tomentose throughout; stem stout, leafy up to the 

 heads, usually branched, 3-6 dm. high. Leaves sessile, partly clasping, or slightly 

 decurrent, with sparingly prickly segments 4-6 mm. wide, with revolute margins; 

 basal leaves often 3 dm. long; heads solitary or several and racemose-spicate at 

 the ends of the branches, about 4 cm. broad ; outer bracts of the involucre ovate- 

 lanceolate, sparingly pubescent and tomentose-ciliate, glutinous on the back, tipped 

 with short spreading bristles, the inner narrowly lanceolate, acuminate or some- 

 times tipped with weak prickles; flowers cream color. . Shores of Lakes Michigan, 

 Huron and Superior. June-Aug. 



7. Carduus undulatus Nutt. WAVY-LEAVED THISTLE. (I. F. f. 4063.) 

 Biennial, persistently and densely white-tomentose throughout, or the upper sur- 

 faces of the leaves at length green and glabrous; stem stout, leafy, usually 

 branched, 3-10 dm. high. Leaves lanceolate or oblong- lanceolate in outline, 

 acute, sessile or decurrent, or the lowest petioled, undulate, lobed or pinnatifid; 

 heads about 5 cm. broad, and nearly as high, solitary at the ends of the branches ; 

 outer bracts of the involucre ovate or ovate-lanceolate, firm, glutinous on the back, 

 tipped with short spreading prickles, the inner ones lanceolate, acuminate. On 

 plains and prairies, Lake Huron to the N. W. Terr, and Br. Col., south to Kans., 

 N. Mex. and Ore. June-Sept. 



Carduus undulatus megac^phalus (A. Gray) Porter. Heads larger than in the 

 type, 5-7 dm. broad. Minn, to Idaho and Ariz. 



8. Carduus Plattensis Rydb. PRAIRIE THISTLE. (I. F. f. 4064.) 

 Perennial or biennial, the root thick and deep. Stem stout, simple, or little 

 branched, 4-7 dm. tall, densely white-felted. Leaves deeply pinnatifid. white- 

 tomentose beneath, green, loosely tomentose, or glabrate above, the lower 12-17 

 cm. long, the lobes lanceolate to oblong, acute, prickly tipped and margined ; 

 heads few, about 5 cm. high and broad; outer bracts of the involucre lanceolate to 

 ovate-lanceolate, firm, dark, tipped with short weak spreading prickles, the inner 

 linear-lanceolate, unarmed, tipped with scarious reflexed erose appendages; pap- 

 pus of outer flowers merely barbellate. Sand hills, Neb. and S. Dak. May-July. 



9. Carduus ochrocentrus (A. Gray) Greene. YELLOW-SPINED THISTLE. 

 (I. F. f. 4065.) Similar to Carduus undulatus, but commonly taller and more 

 leafy, often 2 m. high, equally white-tomentose. Leaves oblong-lanceolate in out- 

 line, usually very deeply pinnatifid into triangular-lanceolate, serrate or entire 

 segments, armed with numerous long yellow prickles; lower leaves often 15-20 

 cm. long; heads about 5 cm. broad. 4-5 cm. high, solitary at the ends of the 

 branches; outer bracts of the involucre lanceolate, tipped with stout yellow prickles 

 of nearly or quite their own length, the inner narrowly lanceolate, long-acumi- 

 nate; flowers purple (rarely white ?). On plains, Neb. to Tex., Nev. and Ariz. 

 May-Sept. 



10. Carduus Nebraskensis Britton. NEBRASKA THISTLE. (I. F. f. 4066.) 

 Stem densely white-woolly, apparently over 3 dm. high. Leaves linear-oblong to 

 lanceolate, white-woolly beneath, green and sparingly loosely woolly above, irregu- 

 larly slightly toothed or entire, the upper 7-15 cm. long, 5-25 mm. wide, the 

 margins prickly; heads solitary, or few, short- peduncled, about 4 cm. high; outer 

 bracts of the involucre lanceolate, prickle-tipped, the inner narrower, with reflexed 

 acute scarious appendages; pappus-bristles of inner flowers plumose, of the outer 

 barbellate. Scott's Bluff, western Neb. and Wyo. July-Aug. 



11. Carduus odoratus (Muhl.) Porter. PASTURE THISTLE. FRAGRANT 

 THISTLE. (I. F. f. 4067.) Biennial, more or less villous-pubescent; stem stout, 

 simple or branched, leafy, 3-10 dm. high. Roots thick, branched, solid; stem- 

 leaves sessile and clasping, oblong or oblong-lanceolate in outline, acute, 7-17 cm, 



