CiRsiuM. COMPOSITE. 407 



spine. — DC. prodr. 6. p. 651 ; Torr. ^ Gr.Jl. N. Am. 2. p. 459. Carduus odoratus, Muhl. 

 cat. p. 70. C, pumilus, (and var. Histrix), Nutt. gen. 2. p. 130 ; Beck, hot. p. 173 ; Dar- 

 lingt. fl. Cast. p. 437. Cnicus pumilus, Torr. compend. p. 282 ; Bigel. jl. Bost. p. 292. 



Biennial. Stem usually 1-2 feet high, but sometimes much taller (3-5 feet), erect. 

 Leaves more or less hairy, particularly on the midrib underneath, spinulose on the margin. 

 Heads about an inch and a half in diameter, often with several pinnatifid bracts at the base. 

 Outer scales of the involucre ovate-lanceolate ; the inner much narrower, with acuminate and 

 sometimes dilated scarious and serrulate tips. Flowers pale reddish purple, odorous. 



Dry fields and pastures ; common in the southern part of the State and on Long Island, but 

 rare in the interior counties. July - August. 



5. CiRSIUM HORHIDULUM, MicllX. YclloW ThlslU. 



Whole plant arachnoid-woolly when young, smoother when old ; stem stout, simple or 

 sparingly branched ; leaves lanceolate, partly clasping, pinnatifid ; the lobes toothed or incised, 

 very spiny ; heads (large) surrounded by a whorl of spinose bracts ; involucre ovate-globose, 

 linear-lanceolate, tapering to a very acute point, scarcely spinose. — Michx. Jl. 2. p. 90 ; DC. 

 prodr. 6. p. 651 ; Torr. <^ Gr. jl. N. Am. 2. p. 460. C. megacanthum, Nutt. in trans. 

 Amer. pliil. soc. (n. ser.) 7. p. 419. Cnicus horridulus, Pursh,Jl. 2. p. 507 ; Bigel. Jl. Bost. 

 p. 291 ; To7-r. compend. p. 281. Carduus spinosissimus, Walt. Jl. Car. p. 194; Darlingt, 

 Jl. Cest. p. 438. 



Biennial ? Stem very thick, hollow, 2-3 feet high. Leaves closely sessile, armed with 

 numerous short stout yellow spines. Heads nearly as large as in the preceding species, partly 

 concealed by the numerous pectinated involucral bracts. Flowers usually pale dull yellow, 

 but occasionally reddish or purplish. 



Sandy fields, particularly near the salt water ; rather common on Long Island. June - July. 



G. CiRSiUM ARVENSE, Scop. (Plate LXL) Canada Thistle. 



Rhizoma creeping ; stem paniculately branched ; leaves oblong-lanceolate, sessile, slightly 

 decurrent, smoothish, sinuate-pinnatifid, undulate ; heads small and numerous ; scales of the 

 involucre ovate-lanceolate, mucronate, the outermost tipped with a short spine. — DC. prodr. 

 6. p. 643 ; Torr. <^ Gr. Jl. N. Am. 2 p. 460. Serratula arvensis, Linn. Carduus arvensis, 

 S77iith, Engl. hot. t. 975 ; Hook. Jl. Bor.-Am. 1. p. 301 ; Beck, hot. p. 172; Darlingt. Jl. 

 Cest. p. 439. Cnicus arvensis, Pursh, Jl. 2. p. 506 ; Bigel. Jl. Bost. j). 291 ; Torr. camp, 

 p. 281. 



Perennial. Rhizoma descending deep in the earth and then spreading, very tenacious of 

 life. Stems 2-3 feet high, smooth, striate and angular ; the branches slightly woolly. 

 Leaves 3-6 inches long and about an inch wide, sometimes a little woolly underneath. 

 Heads, by abortion, dioecious. Involucre usually globose-ovate, but sometimes oblong ; the 

 scales appressed ; some of the outer ones tipped with a very short bristle or weak spine. 

 Flowers pale purple, or rarely whitish. 



