THISTLE FAMILY 273 



Involucres less than 4 cm. broad. 



Spines of the middle bracts 5-10 mm. long. 



Spines of the middle bracts slender and spreading. 4S. C. acualum. 

 Spines of the middle bracts stout and ascending. 



Upper leaves entire or with shallow lobes; involucre less than 2 cm. 



broad, very dark. 49. C. canescens. 



Upper leaves deeply pinnatifld: involucres about 3 cm. broad, light 

 colored, except the viscid ridge. 50. C pulcherrimum. 



Spines of the middle bracts 5 mm. long or less, weak and spreading. 



Leaves, at least the upper ones, entire or slightly lobed, tomentose on both 

 sides. 51. C. oblanceolalum. 



Leaves pinnately divided or deeply lobed. 



Leaves deeply pinnatifld, with narrow, linear-lanceolate lobes; plant 



yellowish. 52. C. Flodmanii. 



Leaves with triangular or ovate-lanceolate lobes. 



Bracts with very inconspicuous glandular ridge, not at all viscid. 



53. C. floccosum. 

 Bracts with a conspicuous glandular ridge, surrounded by a viiscd 

 area. 

 Leaves tomentose on both sides. 54. C. undulatum. 



Leaves glabrate and dark green above. 55. C. Engclmannii. 

 Involucres 4-7 cm. in diameter. 



Spines of the involucral bracts rarely more than 5 mm. long; leaves not con- 

 spicuously decurrent. 56. C. megacephalunx- 

 Spines of the middle bracts fully 1 cm. long; leaves narrower, conspicuously 

 decurrent. 57. C. ochocentruni. 

 Leaves greenish and sparingly floccose on both sides; bracts linear-lanceolate, very viscid, 

 with stout erect or ascending spines. 41. C. canovirens. 



XI. Arvexsia. 

 One species. 58. C. arvense, 



134. ONOPORDON (Vaill.) L. Cotton Thlstle, Scotch Thistle. 



1. O. Acanlium, 



135. CENTAUREA L. Blue Bottle, Corxflower, Bachelor's Buttons, 



Star Thlstle. 



Involucral bracts with lacerate broad appendages; flowers blue. 1. C. Cyanus. 



Involucral bracts with 3-5 spines; flowers yellow. 2. C. solstitial is. 



Family 137. CICHORIACEAE. Chicory Family. 



A. Pappus none; achenes with corkj- pericarp. 1. Atrichoseris. 



B. Pappus present. 



I. Pappus of plumose bristles, often more or less paleaceous at the base. 



Achenes truncate at the apex, not beaked. 



Flowers yellow; simple plants with fusiform roots. 2. Ptiloc.\l.\is. 



Flowers pink, rose, or wliite; branched plants with rush-like stems. 



3. PXILORLi. 



Achenes with long beaks. 

 Receptacle not chaffy. 



Involucres of 7-15 linear-acuminate equal bracts and smaller calyculate 

 ones at the base; achenes obscm-ely ribbed; branched annuals with pin- 

 natifld leaves. 4. Xemoseris. 

 Involucres of several lanceolate-attenuate herbaceous bracts; no calvculate 

 ones at the base; achenes 5-10-ribbed; leaves grass-like and heads soh- 

 tary. 5. Tragopogon. 

 Receptacle chaffy. 6. Hypocheris. 



II. Pappus not plumose. 



a. Pappus consisting, at least partly, of squamellae or these reduced and united 



into a crown. 



1. Involucres simple and naked, i. e., ^vithout smaller calyculate ones below: 



pappus of both squamellae and bristles; flowers yellow. 



7. Adopogox. 



2. Involucres double, either imbricate or with smaller calyculate ones below. 

 Flowers blue; pappus crowTi-like of small numerous blunt squamellae in 



2 or more series; tall perennials. 8. Cichorr^l 



Flowers yellow; pappus of large squamellae; low annuals, acaulescent or 

 nearly so 

 Squamellae of the pappus 5, cleft at the apex with an awn in the notch; 



involucres calyculate. 9. Urop.\ppu3. 



Squamellae of the pappus 20-30. very narrow, linear-lanceolate, taper- 

 ing into a bristle-like apex; bracts nearly equal, in two series. 



10. Nothocalais. 



b. Pappus of capillary bristles, not plumose, slightly if at aU broadened below. 



1. Achenes not flattened. 



a. Pappus-bristles promptly deciduous, mainly together, only a few of the 

 stouter ones in some species remaining. 

 Achenes more or less narrowed into a beak. 



Achenes without a cup-shaped shoulder, not cancellate. 



