yellowish-white filiform-tubular corolla which at the tip is microscopically un- 

 equally toothed with 3 of the teeth much longer than the other 2 (the 3 longer 

 teeth corresponding to the 3 teeth at the end of a ray and oriented to the outside 

 of the head); central flowers numerous, perfect, fertile, the corollas with basal 

 tube and a flaring equally 5-toothed limb; achenes all alike, columnar; pappus 

 of copious soft white capillary bristles. 



Infrequent in muddy places, about seepage and lakes, along streams, in s.e. 

 Tex. and s. part of e. Tex., Aug.-Nov.; e. U.S. 



48. Cirsium Mill. Thistle. Plumed Thistle 



Winter annual, biennial or perennial herbs; leaves alternate, entire or often 

 lobed, usually also irregularly serrate, the whole blade plus each lobe plus each 

 tooth usually ending in a spine-tip, sessile, often narrowed to a subpetiolar base, 

 often slightly decurrent on the stem, often with a thin floccose wool beneath or 

 on both surfaces; heads singly terminating the pedunculiform upper parts of the 

 branches; involucre ovoid or subcylindric to urceolate or nearly globose, usually 

 much broader and more saucer-shaped after anthesis and when the achenes are 

 mature; receptacle covered with soft hairlike bristles; phyllaries in many series, 

 strongly imbricated, mostly lanceolate and nearly always each one ending in a 

 spine-tip (not in C muticum); ray flowers absent; disk flowers numerous, perfect, 

 fertile; corolla usually mauve, reddish-purple, purple or pink, rarely white or 

 yellowish (in C horrididum) , deeply and subequally 5-lobed; filaments separate; 

 achenes mostly oblong or elliptic-oblong, flattish, unribbed, attached basally to the 

 receptacle; pappus of numerous bristles united in a ring at the base, the lower 

 part of each bristle plumose, the entire pappus deciduous as a unit. 



A north-temperate genus of about 150 species. Differing from Carduus only 

 in that each unit of the pappus is decidedly plumose in the lower part; probably 

 should be submerged in Carduus. 



1. Distribution in eastern Texas and/or eastern Oklahoma (2) 



1. Distribution in mountains of New Mexico and Arizona (3) 



2(1). Flowers pinkish or yellowish; phyllaries of the true involucre all with weak 

 flat tips but the large heads (4-8 cm. broad) subtended and often 

 equalled or surpassed by a false involucre of large very spinescent 

 appressed bracteal leaves 1. C. horridulum. 



2. Flowers purple or rarely whitish; outer phyllaries barely pointed, scarcely 



prickle-tipped; inner phyllaries with broadly lanceolate tips; heads 

 essentially naked 2. C. muticum. 



3(1). Corollas yellow or greenish-yellow; at least some phyllaries usually 

 pectinate-ciliate (4) 



3. Corollas purple, pink, red or white; phyllaries typically not pectinate-ciliate 



(6) 



4(3). Phyllaries not densely arachnoid on backs 3. C. inornatum. 



4. Phyllaries typically densely arachnoid throughout (5) 



5(4). Inner phyllaries with dilated-lacerate tips 4. C. Parryi. 



5. Inner phyllaries without dilated-lacerate tips 5. C. pallidum. 



6(3). Outer phyllaries strongly reflexed for half their length, purple; entire plant 

 commonly tinged with brownish-purple 6. C. vinaceum. 



6. Outer phyllaries not strongly reflexed for half their length, only the tips purple 



at most; entire plant not purplish (7) 



7(6). Inner phyllaries elongate, attenuate, plane 7. C. nidulum. 



7. Inner phyllaries with dilated twisted frequently fimbriate tips 8, C. foliosum. 



1694 



