FLORA OF THE DISTRICT OF COLUMBIA. 271 



Leave shallowly toothed or entire: plants never with viseid pul>efeonce. 



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



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



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



reduced alternate ones about the inflorescence 42. AB.NICA. 



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. SILPHIUM. 

 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 c^odu falling 



from the fruit; perennials or annuals 30. HELIANTHUS. 



CO. Leaves alternate. 



Stems narrowly or broadly winged. 

 Leaves ^\4th 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. RID AN. 

 Stems not winged . 

 D. Rays yellow, the inner flowers of the head yellow, brown, or i)urple. 

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



7. GRINDELIA. 

 Teeth of the leaves never ending in spinelike haii's, 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 while bristles. 



46. SENECIO. 

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



minute crown 29. RXJDBECKIA. 



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. HELIANTHUS. 



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



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



appressed hairs, often deciduous 8. CHRYSOPSIS. 



