•Genus 97.] 



THISTLE FAMILY. 



7. Carduus Plattensis Rydberg. 

 Prairie Thistle. (Fig. 4064.) 



Carduus Plallensis Rydberg, Contr. Nat. Herb. 



3: 167. pt. 2. 1895. 



Perennial or biennial, the root thick and deep. 

 Stem stout, simple, or little branched, iK°-2>^° 

 tall, densely white-felted. Leaves deeply pin- 

 natifid, white-tomentose beneath, green, loosely 

 tomentose, or glabrate above, the lower $'-"]' 

 long, the lobes lanceolate to oblong, acute, 

 prickly tipped and margined; upper leaves small- 

 er and less divided; lieads few, about 2' high and 

 broad; outer bracts of the involucre lanceolate 

 to ovate-lanceolate, firm, dark, tipped with a 

 short weak spreading prickle, the inner linear- 

 lanceolate, unarmed, tipped with a scarious re- 

 flexed erose appendage; corolla yellow, its lobes 

 linear; pappus of outer flowers merely barbel- 

 late. 



Sand hills, Nebraska and South Dakota. May- 

 July. 



8. Carduus ochrocentrus (A. Gray) Greene. Yellow-spined Thistle. 



(Fig. 4065.) 



A. Gray, Mem. Am. 

 Gray, Proc. Am. Acad. 



9. Carduus Nebraskensis Britton. 

 Nebraska Thistle. (Fig. 4066.) 



Ci'rsiu m och rocen tru m 



Acad. I: no. 1849. 

 Cniciis ochrocentrus A. 



19:57. 1883. 

 Carduusochrocentrus Greene, Proc. Phu. Acad. 



1892: 336. 1893. 



Similar to Carduus undulatus, but com- 

 monly taller and more leafy, often 6° high, 

 equally white-tomentose. Leaves oblong- 

 lanceolate in outline, usually very deeply 

 pinnatifid into triangular-lanceolate, serrate 

 or entire segments, armed with numerous 

 long yellow prickles; lower leaves often 6'-S' 

 long; heads about 2' broad, i/^'-2' high, 

 solitary at the ends of the branches; outer 

 bracts of the involucre lanceolate; tipped 

 with stout }-ellow prickles of nearly or quite 

 their own length, the inner narrowly lanceo- 

 late, long-acuminate; flowers purple (rarely 

 white?). 



On plains, Nebraska to Texas, Nevada and 

 Arizona. May-Sept. 



stem densely white- woolly, apparently over 1° 

 high. Leaves linear-oblong to lanceolate, white- 

 woolly beneath, green and sparingly loosely woolly 

 above, irregularly slightly toothed or entire, the 

 upper 3'-6' long, '+ '-i' wide, the margins prickl}'; 

 heads solitary, or few, short- peduncled, about i j4' 

 high; outer bracts of the involucre lanceolate, 

 prickle-tipped, the inner narrower with a reflexed 

 acute scarious appendage; pappus bristles of inner 

 flowers plumose, of the outer barbellate. 



Scott's Bluff, western Nebraska (P. A. Rydberg, No. 

 110. 1891). 



