Genus 97.] 



THISTLE FAMILY 



7. Carduus Plattensis Rydberg. 

 Prairie Thistle. (Fig. 4064.) 



Carduus Plattensis Rydberg, Contr. Nat. Herb. 



3: 167. pi. 2. 1895. 



Perennial or biennial, tbe root thick and deep. 

 Stem stout, simple, or little branched, i%-2y 2 

 tall, densely white-felted. Leaves deeply pin- 

 natifid, white- tome ntose beneath, green, loosely 

 tomentose, or glabrate above, the lower 5 / -7 / 

 long, the lobes lanceolate to oblong, acute, 

 prickly tipped and margined; upper leaves small- 

 er and less divided; heads few, about 1' 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.) 



Cirsium ochrocentrum A. Gray, Mem. Am. 



Acad. 1: no. 1849. 

 Cnicus ochrocentrus A. Gray, Proc. Am. Acad. 



19: 57. 1883. 

 Cardu us ochrocentrus Greene, Proc. Phil. Acad. 



1892:336. 1893. 



Similar to Carduus undulalus, 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 / -8 / 

 long; heads about 2 / broad, i / ^ / -2 / 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 lanceo- 

 late, long-acuminate; flowers purple (rarely 

 white ?) . 



On plains, Nebraska to Texas, Nevada and 

 Arizona. May-Sept. 



g. Carduus Nebraskensis Brittou. 

 Nebraska Thistle. (Fig. 4066.) 



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 prickly; 

 heads solitary, or few, short-peduneled, about \%, f 

 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. 

 no. 1891). 



