Dicotyledones. 117 



occur on the receptacle among the flowers. The receptacle is said 

 to be naked when these are absent. 



A, Corollas all tubular, or ligulate and pistillate, or neutral only, at the margin of the head. 



Flowers of the head all tubular; dioecious. Antennakia II. 



Disk flowers tubular; ray flowers ligulate. 



Ray flowers white, pink, or purple, rarely yellow. 

 Pappus of capillary bristles. 



Ray flowers numerous and pistillate; bracts of the involucre little im- 

 bricated; receptacle naked. Erigeron I. 

 Pappus a minute crown or wanting. 



(fl) Ray flowers pistillate or neutral; bracts of the involucre imbricated in 



several rows ; receptacle convex and chaffy near the summit; heads 



on long, terminal peduncles. Anthemis III. 



(^) Ray flowers pistillate; bracts of the involucre imbricated in few rows, 



appressed; receptacle chaffy; heads small in corymbose clusters. 



Achillea IV. 



(c) Ray flowers pistillate; disk flowers with flattened tubes; involucral 



scales imbricated in several rows ; receptacle without chaff"; heads 



large on long peduncles. Chrysanthemum V. 



Ray flowers yellow. 



Pappus of capillary bristles; disk flowers as well as ray flowers, when present, 

 yellow. Senecio VI. 



B. Corollas all ligulate, and all flowers of the head perfect. 



Heads borne singly on a scape. 



(a) Leaves tufted at the base, entire. Troximon VII. 



(6) Leaves tufted at the base, pinnatifid or runcinate. Taraxacum VIII. 



Heads borne on long, bracted peduncles, sometimes scapose. Pvrrhopappus IX. 



Heads in corymbose or paniculate clusters on leafy stems; leaves with prickly 



margins. Sonchus X. 



I. TubuliJlor<2, 



I. ERIGERON. Fleabane. 



(Gr., eri, early ; geron^ old man, from the hoariness of some of the early spring species.) 



Heads radiate on the margin. Ray flowers white, pinkish, or purple ; 

 disk flowers yellow. Ray flowers numerous and pistillate. Involucre 

 hemispheric or campanulate, its bracts narrow and little, or not at all, 

 imbricated. Receptacle naked, nearly flat. Pappus a row of capil- 

 lary bristles with smaller ones interspersed. Achenes flattened, often 

 pubescent and 2-nerved. 



I. Erigeron annuus, Pers. (L., annuus, annual.) Sweet Scabious. Slightly 

 pubescent annuals, i to 4 feet higli, corymbosely branched above. Lower leaves 

 petioled, ovate, or ovate-lanceolate, mostly coarsely dentate; the upper leaves 

 lanceolate or ovate-lanceolate, sessile or short-petioled, shaiply dentate. 40-70 

 linear, white or purplish, rays. Pappus doubled by an outer row of slender 

 scales; the inner row of capillary bristles often wanting in the ray flowers. In 

 fields and waste places. 



