FLORA OF THE DISTRICT OF COLUMBIA. 271 



Leave shallowly toothed or entire; plants never with viscid pubescence. 

 Bracts all of equal length, in one series; pappus of numerous long 

 soft bristles. Leaves mostly borne at the base of the stem, the 

 stems bearing one or 2 pairs of sessile opposite leaves and a few- 

 reduced alternate ones about the inflorescence 42. ARNICA. 



Bracts unequal, the outer ones shorter, in more than one series: pappus 

 never of long bristles. 

 Leaves mostly in whorls of 3 or 4; inner flowers of the head sterile, 

 not producing fruit. Tall perennials with glabrous stems. 



24. SILPHITJM. 

 Leaves opposite by 2's, never whorled; all the flowers fertile and 

 producing fruit. 

 Bracts obtuse or rounded at the apex; rays papery and persisting 

 on the fruit; perennials with petioled leaves. 



27. HELIOPSIS. 

 Bracts acute or long-pointed; rays thin and usually soon falling 



from the fruit; perennials or annuals 30. HELIANTHTJS. 



CC. Leaves alternate. 



Stems narrowly or broadly winged. 

 Leaves with numerous oil glands; rays much broadened near the apex, deeply 

 3-lobed; fruit neither flattened nor winged, the pappus of 5-8 scales. 



36. HELENIUM. 

 Leaves without oil glands; rays narrowed at the apex, shallowly toothed or 

 entire; fruit flattened, broadly winged, the pappus of 2 slender awns. 



31. RIDAN. 

 Stems not winged. 

 D. Rays yellow, the inner flowers of the head yellow, brown, or purple. 

 Teeth of the leaves ending in short stiff spinelike hairs; bracts very viscid. 



7. GRINDELIA. 

 Teeth of the leaves never ending in spinelike hairs, the leaves often entire; 

 bracts very slightly if at all viscid. 

 Leaves, at least some of them, deeply lobed or divided. 

 Bracts equal, in one series, a few very small ones sometimes present at 

 the base of the involucre; pappus of numerous soft white bristles. 



46. SENECIO. 

 Bracts very unequal, the outer gradually shorter; pappus none or a 



minute crown 29. RUDBECKIA. 



Leaves entire or toothed, never lobed or divided. 

 Pappus of a few teeth or short awns or wanting; flower heads large, with 

 very large and showy rays. 

 Bracts reflexed; receptacles of the flower heads conical, 1-1.5 cm. 

 broad; disk flowers dark purple; leaves broader than linear. 



29. RUDBECKIA. 

 Bracts erect or appressed ; receptacles of the flower heads flat or some- 

 what convex, often 5 cm. broad or even larger; disk flowers often 

 yellow; leaves linear to broadly ovate-cordate. 



30. HELIANTHTJS. 



Pappus of numerous slender bristles; flower heads large or often very 



small. 



Pappus in 2 series, the inner of long soft brownish bristles, the outer of 



very Bhort stiff bristles; heads about 1 cm. high, the rays nearly 



or quite 1 cm. lonp; pubescence of the leaves of very long silky 



appressed hairs, often deciduous 8. CHRYSOPSIS. 



