THISTLE FAMILY 227 



Bracts of the involucres longitudinally striate; heads in con- 

 gested corymbs. 28. Oligonetjron. 

 b. Ray-flowers blue, pink, or white. 



1 . Pappus a mere crown or of few scales or awn-like bristles. 



Pappus of a cup-shaped crown and a single awn ; dwarf annuals, branched 

 at the base. 29. Monoptilon. 



Pappus of a series of long awns or that of the rays of short scales ; annuals 

 or perennials. 30. Townsendia. 



2. Pappus of numerous capillary bristles. 



a. Bays only slightl;^ if at all exceeding the pappus; annuals. 

 Bracts in 2-3 series, the outer foliaceous ; stigma-tlps acute. 



31. Brachyactis. 

 Bracts in 1-2 series, narrow, not foliaceous; stigma-tips obtuse. 



46. Leptilon. 



6. Rays conspicuous, longer than the pappus, usually equalling or exceed- 

 ing the width of the disk. 

 Style-tips lanceolate or oblong to filiform. 



Bracts in a single series, with hyaUne-scarious erose-flmbriate mar- 

 gins; dwarf winter annuals. 32. Eremiastrum. 

 Bracts in at least 2 or usually in more than 2 series. 

 Pappus simple, of similar bristles. 



Plants rush-Uke, spiny. 33. Leucosyris. 



Plants not spiny. 



Perennials, with a rootstock or caudex. 



Bracts acuminate, as well as the leaves tipped with 

 callous poults or spines; plants with soUtary 

 heads at the ends of the stems or branches, and 

 cespitose caudices. 

 Achenes pubescent; bracts all narrow, the outer 

 not passing into the leaves; heads distinctly 

 peduncled. 34. Xylorrhi7a. 



Achenes glabrous; outer bracts broad, foliaceous, 

 passing into the leaves; heads subsesslle. 

 35. Herrickia. 

 Bracts not acuminate, or if long-attenuate with soft 

 tips. 

 Pappus dilated at the apex; bracts narrow, more 



or less keeled. 36. Unamia. 



Pappus not dilated at the apex. 



Bracts broad, with a distinct keel or mid-vein, 



not at all foUaceous. 37. Eucei'hai.us. 

 Bracts usually narrow, when broad neither 

 keeled nor with a prominent midvein. 

 Bracts more or less foliaceous or foUaceous- 

 tipped, usually in several series; heads 

 usually several, racemose or paniculate; 

 stigma-tips lanceolate to subulate, 

 shorter than the stigmatic portion. 

 38. Aster. 

 Bracts not foliaceous, narrow and in 1-3 

 series. 

 Style-tips slender, usually twice as long 

 as the stigmatic portions; achenes 

 terete. 39. Obeostemma. 



Style-tips ovate or triangular and 

 acuminate-subulate; achenes flat. 

 40t Asterigeron. 

 Annuals or biennials, or if short-lived perennials, with a 

 taproot; bracts in many series, with herbaceous 

 spreading or reflexed tips; stigma-tips linear to fili- 

 form. 44. Machaeranthera. 

 Pappus double, the inner of capillary bristles, the outer of short 

 bristles or scales. 

 Inner pappus-bristles more or less thickened above; bracts 

 thin-coriaceous, without herbaceous tips, shorter than the 



disk. 4i; DOEUNGERIA. 



Inner pappus-bristles filiform, not thickened above; bracts 

 equalling the disk. 42. Ionactis. 



Style-tips triangular or ovate, obtuse or rarely acutish ; bracts not foU- 

 aceous. 

 Involucres tm-binate; bracts well imbricate, in several series, scarious- 



margined ; disk-flowers white. 43. Leucelene. 



Involucres hemispherical or broader; bracts not scarious-margined, 

 in 1-3 series; disk-corollas yellow, rarely ochroleucous. 



45. Erigeron. 

 II. Marginal pistillate flowers not ligulate, reduced to a flUform or narrow short tube. 



47. ESCHENBACHIA. 



B. Heads unisexual, dioecious, discoid; pappus of the staminate flowers with clavate tips. 



48. Baccharis. 

 Tribe 4. GNAPHALIEAE. 



Shrubs ; bracts coriaceous ; receptacle naked ; pistillate flowers numerous ; corolla reduced 

 to a short slender tube; hermaphrodite flowers few and sterile, their pappus with 

 clavate tips. 49. Beethelotia. 



