Genus 104. 



THISTLE FAMILY. 



549 



1. Cirsium lanceolatum (L.) Hill. Common 

 Bur or Spear Thistle. Fig. 4636. 



Carduus lanceolatus L. Sp. PI. 821. 1753. 

 Cirsium lanceolatum Hill, Herb. Brit. 1 : 80. 1769. 

 Cnicus lanceolatus Willd. Prodr. Fl. Berol. 259. 1787. 



Biennial ; stem stout, branched, more or less to- 

 mentose, 3-5 high, leafy to the heads. Leaves dark 

 green, lanceolate, acuminate, deeply pinnatifid, 3'-6' 

 long, or the lowest larger, decurrent on the stem and 

 branches, the lobes triangular-lanceolate, tipped with 

 stout prickles, the margins and decurrent bases 

 bristly, the upper surface strigose-pubescent or his- 

 pid, the lower brown-tomentose and midnerve pilose, 

 especially when young ; heads mostly solitary at the 

 ends of the branches, li'-2' broad, li'-2' high; bracts 

 of the involucre cottony, narrowly lanceolate, acumi- 

 nate, all tipped with slender, erect or ascending 

 prickles; flowers dark purple. 



In fields and waste places, Newfoundland to Georgia, 

 Minnesota, Nebraska, Oregon and California. Natural- 

 ized from Europe. Native also of Asia. Plume-, bank- 

 or horse-thistle, bell-, bird-, blue-, button-, boar-, bull- or 

 roadside-thistle. July-Nov. 



2. Cirsium altissimum (L.) Spreng. Tall or Roadside Thistle. Fig. 4637. 



Carduuse altissimus L. Sp. PI. 824. 1753. 

 Cnicus altissimus Willd. Sp. PI. 3: 1671. 1S04. 

 Cirsium altissimum Spreng. Syst. 3: 373. 1826. 



Biennial or perennial; roots often thickened; 

 stem pubescent or tomentose, stout, branched, leafy 

 to the heads, 3-io high. Leaves ovate-oblong or 

 oblong-lanceolate, sessile or slightly clasping, spar- 

 ingly pubescent above, densely white-tomentose be- 

 neath, scarcely or not at all decurrent, acute, spinu- 

 lose-margined, entire, dentate with bristle-pointed 

 teeth or lobed, sometimes pinnatifid into oblong or 

 triangular-lanceolate segments, the lowest some- 

 times 8' long, narrowed into margined petioles, the 

 uppermost linear or lanceolate, much smaller; 

 heads about 2 broad, 1V-2' high, mostly solitary at 

 the ends of the branches; outer bracts of the invo- 

 lucre ovate or ovate-lanceolate, firm with a dark, 

 slightly glandular spot or band on the beak, tipped 

 with short prickles, the inner linear-lanceolate, 

 acuminate, unarmed ; flowers light purple. 



In fields and thickets, Massachusetts to Ohio, Min- 

 nesota, Florida, Nebraska and Texas. Aug.-Sept. 



Cirsium iowense Pammel, with slightly larger heads 

 and longer-tipped inner involucral bracts, appears to 

 be a northwestern race of this species. 



3. Cirsium discolor ("Muhl.) Spreng. Field 

 Thistle. Fig. 4638. 



Cnicus discolor Muhl. ; Willd. Sp. PI. 3 : 1670. 1804. 



Carduus discolor Nutt. Gen. 2: 130. 1818. 



Cirsium discolor Spreng. Syst. 3: Z7Z- 1826. 



Similar to the preceding species, but lower and 

 more leafy, seldom over 7 high. Leaves deeply pin- 

 natifid into linear, linear-lanceolate or falcate, prickly 

 toothed segments, white tomentose beneath, sessile, 

 the basal ones sometimes 12' long; heads \l'-2' broad, 

 about ii' high, usually involucrate by the upper 

 leaves, mostly solitary at the ends of the branches; 

 outer bracts of the involucre coriaceous, ovate, 

 slightly woolly, tipped with slender bristles, which 

 are longer than those of the preceding species; inner 

 bracts lanceolate, acuminate, unarmed; flowers light 

 purple or pink, rarely white. 



In fields and along roadsides, New Brunswick to On- 

 tario, Georgia, Minnesota, Nebraska and Missouri. July- 

 Nov. 



