THISTLE FAMILY 1003 



purple or violet; tube slender; throat inflated, and limb 5-toothed. Flowers 

 hermaphrodite and fertile. Anthers caudate at the base, with setiform ciliate or 

 villous appendages. Pappus double, the outer of short rigid bristles, the inner of 

 stout plumose bristles united at the base. 



Leaves broadly ovate or the lower cordate; plant tall, 4-10 dm. high. 1. S. americana. 

 Leaves lanceolate to linear. 



Leaves lanceolate; stem 1-2 dm. high; heads crowded. 2. S. densa. 



Leaves very narrowly linear-lanceolate; stem 3-4 dm. high; heads long-pedunlced. 



3. S. remotiflora. 



1. S. americana D. C. Eat. Stem 4-10 dm. high, glabrous or slightly arach- 

 noid-hairy when young, leafy; lower leaves petioled, the uppermost sessile; blades 

 cordate or ovate, thin, arachnoid when young, dentate, acute or acuminate; 

 heads more or less paniculate; involucres cylindro-campanulate, about 12 mm. 

 high, 7-9 mm. broad, arachnoid-pubescent; bracts in 5-6 series, deltoid or deltoid- 

 ovate, acute, the inner dark-margined; corollas blue or purple. Mountain mead- 

 ows and slopes: Ore. Ida. Wash. Submont. Mont. Jl-Au. 



2. S. densa (Hook.) Rydb. Stem short, 1-2 dm. high, leafy; leaves 5-10 

 cm. long, the lower with winged petioles, the upper sessile; blades lanceolate, 

 arachnoid-hairy when young, sinuate-dentate; involucres campanulate, about 1 

 cm. high and broad, arachnoid-hairy; bracts in 4-5 series, but almost of the same 

 length, lanceolate or ovate-lanceolate, acuminate; flowers purple. AS. alpina densa 

 Hook. High mountains: Canadian Rockies. Alp. Au. 



3. S. remotiflora (Hook.) Rydb. Stem slender, 3-4 dm. high, glabrous or 

 slightly arachnoid, sparingly leafy, often purple-tinged; lower leaves petioled, 

 5-10 cm. long, arachnoid when young; blades linear-lanceolate, remotely dentate; 

 inflorescence corymbiform; involucres turbinate, about 12 mm. high and 10 mm. 

 broad, slightly arachnoid; bracts lanceolate, acute, well-imbricate, the outer 

 successively shorter; flowers purple. S. alpina remotiflora Hook. Valleys: Sask. 



-Yukon Alaska. Alp. Jl-Au. 



133. CIRSIUM (Tourn.) Hill. THISTLE. 



Stout perennial or biennial herbs. Leaves alternate, with spinosely tipped 

 lobes or teeth, often decurrent on the stem. Heads discoid. Involucres globose, 

 campanulate or urceolate, of many imbricate bracts in several series. Receptacle 

 flat, bristly. Flowers hermaphrodite and fertile, or the plant rarely dioecious. 

 Corollas all alike, tubular, deeply 5-cleft. Anthers sagittate at the base, the two 

 lobes produced into longer or shorter tails. Styles filiform or sometimes thick- 

 ened, or with a ring at the base of the stigmatic portion. Achenes obovate or 

 oblong, somewhat flattened. Pappus of one series of slender plumose bristles, 

 united at the base and falling off together. 



Bracts of the involucre conspicuously arachnoid-pubescent. 



Bracts not reflexed, only the tips sometimes spreading; stem arachnoid. 



Inner bracts conspicuously dilated. I. PARRYANA. 



Inner bracts not dilated. 



Leaves not conspicuously decurrent. II. ERIOCEPHALA. 



Leaves conspicuously decurrent, forming wings on the stem. 



III. LAXCEOLATA. 



Bracts squarrose and the lower reflexed. IV. XEOMEXICAXA. 



Bracts of the involucre not arachnoid-pubescent, or only slightly so on the margins. 

 Bracts all, except the outermost, with dilated fimbriate tips. V. CARUXOIDIA. 



Bracts all, except sometimes the very innermost, without dilated fimbriate tips. 

 Bracts neither with a dorsal glutinous ridge, nor a dark spot. 



Bracts, at least some of them, spinulose-ciliate on the margins, not very un- 

 equal in length. VI. LEIOCEPHALA. 

 Bracts not spinulose-ciliate, regularly imbricate, the inner much longer. 



Innermost innocuous bracts not conspicuously elongate, their tips more or 

 less spreading, usually crisp or twisted, sometimes erose. 



VII. FOLIOSA. 



Innermost innocuous bracts elongate and usually more or less reddish, 



straight, neither dilated, crisp or twisted. VIII. PULCHELLA. 



Bracts with either a glutinous dorsal ridge or a black spot near the tip. 

 Bracts with a dark spot, but not glutinous; their spines erect. 



IX. GRISEA. 

 Bracts with a glutinous dorsal ridge. 



Flowers perfect. X. UXDTTLATA. 



Flowers dioecious. XL ARVENSIA. 



