GENUS 104. THISTLE FAMILY. 551 
7. Cirsium platténse (Rydb.) Britton. 
Prairie Thistle. Fig. 4642. 
Carduus plattensis Rydberg, Contr. Nat. Herb. 3: 167. 
pl. 2. 1895. 
Perennial or biennial, the root thick and deep; 
stem stout, simple, or little branched, 12°-23° tall, 
densely white-felted. Leaves deeply pinnatifid, 
white-tomentose beneath, green, loosely tomen- 
tose, or glabrate above, the lower 5’-7’ long, the 
lobes lanceolate to oblong, acute, prickly tipped 
and margined; upper leaves smaller and less di- 
vided; heads few, about 2’ high and broad; outer 
bracts of the involucre lanceolate to ovate-lanceo- 
late, firm, dark, tipped with a short weak spread- 
ing prickle, the inner linear-lanceolate, unarmed, 
tipped with a scarious reflexed erose appendage; 
corolla yellow, its lobes linear; pappus of outer 
flowers merely barbellate. 
Sand hills, Nebraska, Colorado and South Dakota. 
May-July. 
8. Cirsium Flédmani (Rydb.) Britton. Flod- 
man’s Thistle. Fig. 4643. 
Carduus Flodmani Rydb. Mem. N. Y. Bot. Gard. 1: 451. 
1900. 
Stem rather slender, 14°-3° tall, loosely white-cottony, 
usually more or less branched. Leaves deeply pinnatifid 
into linear-oblong or lanceolate, acute or acuminate, 
toothed or entire segments, floccose and green above, 
densely white-cottony beneath, the lower 6’ long or less; 
heads 14’-2’ broad; involucre campanulate, its linear 
bracts tipped with yellow prickles; flowers reddish- 
purple to rose. 
Ad 
Meadows and river bottoms, Iowa and North Dakota to 
Saskatchewan, Nebraska and Colorado. Has been referred 
to the western C. canescens. July—Sept. 
g. Cirsium ochrocéntrum A. Gray. 
Yellow-spined Thistle. Fig. 4644. 
Cirsium ochrocentrum A. Gray, Mem. Am. Acad. 
Li 17, 1840 
Cnicus ochrocentrus A. Gray, Proc. Am. Acad. 19: 
57. 1883. 
Carduus ochrocentrus Greene, Proc. Phil. Acad. 
1892: 336. 1893. 
Similar to Cirsium undulatum, but commonly 
taller and more leafy, often 6° high, equally 
white-tomentose. Leaves oblong-lanceolate in 
outline, usually very deeply pinnatifid into tri- 
angular-lanceolate, serrate or entire segments, 
armed with numerous long yellow prickles; 
lower leaves often 6’-8’ long; heads about 2’ 
broad, 14’-2’ high, solitary at the ends of the 
branches; outer bracts of the involucre lan- 
ceolate; tipped with stout yellow prickles of 
nearly or quite their own length, the inner nar- 
rowly lanceolate, long-acuminate; flowers pur- 
ple (rarely white?). 
On plains, Nebraska to Texas, Nevada and Ari- i 
zona. May-—Sept. D 
FS 
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