COMPOSITAE 



AA 



Pappus none, or of 2-4 stout hooks: fls. yellow 49. Lapsana 



BB. Pappus of bristles. 



C. Pappus bristles stout, plumose. 



Plants glabrous or appressed-tomantose: lvs. mostly lanceolate 

 or linear, entire: involucre large, 2-6 cm. high: plume 

 of pappus bristles interlaced. 

 Involucral bracts imbricated in several series: 



f r . beakless 52 . Scorzonera 



Involucral bracts in a single series: fr. beaked 51. Tragopogon 



Plants setose or hirsute: lvs. mostly elliptic, toothed or 

 pinnatifid: involucre 1-1.5 cm. high: plumes of pappus 



bristles not interlaced 50. Picris 



CC. Pappus bristles very numerous, slender, simple. 

 D. Heads borne on brg., lfy. or bracteate stems. 



E. Heads with 5-30 florets: pappus bristles all nearly alike, 

 not cottony and adhesive. 

 Infl. cymose or corymbose: tube of corolla 1/5-1/3 as 

 long as the ligule, glabrous or evenly scabrous. 

 Fr. beakless, unequally ribbed, 4 or 5 of the ribs 

 stronger than the others: ovary with 5 or 4 vas- 

 cular bundles 57. Youngia 



Fr. definitely beaked (except in /. lanceolata), mostly 

 10 (in I. denticulata 12-15)-ribbed; the ribs equal, 

 prominent, often alate: ovary with 5 vascular 



bundles 56 . Ixeris 



Infl. (in our species) racemose-paniculate: tube of 

 corolla 1/2-1 times as long as the ligule: ovary 



with 2-4 vascular bundles 55 . Lactuca 



EE. Heads with 75-100 or more florets: pappus bristles of 

 two sorts; some straight and many-celled in cross- 

 section; others flexuous, cottony and adhesive to 



clothing, etc 54. Sonchus 



DD. Heads solitary on leafless, hollow scapes: plant acaulescent .. 53. Taraxacum 

 Fls., when hermaphrodite, with the corolla tubular and regular or 

 essentially so (or rarely bilabiate); marginal fls. of the head often 

 pistillate or neutral (that is, without stamens or style, and with 

 infertile ovary) and often with strap-shaped, 2-3 (-4)-toothed corolla: 

 plants without milky latex. 

 F. Heads discoid or disciform (no strap-shaped ray fls.) 

 G. Pappus none. 



H. Plant thistle-like, with spiny lvs.: corollas bright orange.. 45. Carthamus 



HH. Plant not thistle-like, the lvs. not spiny: corollas not orange. 



Plant monoecious; the pistillate heads 2-fid., in the form 



of a bur clothed with hooked prickles; the corolla 



wanting; the staminate heads in short spikes or 



racemes, discoid, many-fid., with an involucre of a 



few small bracts 15 . Xanthium 



Plants not monoecious, the individual fls. of the head 

 hermaphrodite (but the inner sometimes functionally 

 staminate) or the outer ones pistillate. 

 Outer phyllaries herbaceous: achenes rather slender and 



elongated, narrowed into a short beak 13. Carpesium 



Outer phyllaries with scarious margins, not at all 

 herbaceous: achenes short, not beaked 31 . Artemisia, 



388 



