674 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



33. ERIGERON L. Fleabane. 



Annual or perennial herbs, sometimes woody at the base, with entire or toothed, 

 mostly sessile leaves, these sometimes all basal; heads solitary or corymbose, often 

 showy, the disk flowers yellow, the rays white to purple, sometimes short and incon- 

 spicuous, rarely wanting; involucral bracts narrow, imbricated in 2 to 4 series, the 

 outer sometimes shorter; receptacle flat or convex, naked; achenes flattened or nearly 

 terete, pubescent or glabrous, smooth or striate; pappus a single series of bristles or 

 with an outer series of short bristles or inconspicuous palese. 



KEY TO THE SPECIES. 



Bracts of the involucre in 3 or 4 series, imbricated, thickened 

 on the back, the outer successively shorter. 



Pubescence spreading; basal leaves oblanceolate, obtuse 1. E. caespitosus. 



Pubescence appressed; basal leaves linear or linear-oblanceo- 

 late, mostly acute. 



Achenes glabrous 2. E. canus. 



Achenes pubescent. 

 Heads large, 10 to 12 mm. broad; stems sparingly strigose; 



bracts thin 3. E. pulcherrimus. 



Heads small, 6 to 8 mm. broad; stems densely grayish- 



strigose; bracts very thick 4. E. utahensis. 



Bracts in 1 or 2 series, about equal, not thickened on the back. 

 Rays inconspicuous, slightly if at all exceeding the disk, 

 usually with a row of rayless pistillate flowers inside; 



heads racemose 5. E. minor. 



Rays conspicuous (in one species wanting), much longer than 

 the disk, without rayless pistillate flowers inside; heads 

 not racemose. 

 Plants with runners, at least at maturity. 



Leaves and stem with spreading pubescence 6. E. commixtus. 



Pubescence all appressed. 

 Whole plant nearly glabrous, bright green; heads about 



5 mm. broad 7. E. tonsus. 



Plants abundantly strigose, grayish; heads more than 

 5 mm. broad. 

 Stems branched at the base; cauline leaves narrowly 



oblanceolate to linear, acute 8. E. flagellwis. 



Stems branched above the base; cauline leaves obo- 



vate or oblanceolate, obtuse 9. E. senilis. 



Plants without runners. 

 Annuals or biennials. 



Cauline leaves broad, cordate-clasping; rays white or 



pink 10. E. philadelphicus. 



Cauline leaves narrower, not cordate-clasping; rays 

 variously colored. 

 Pubescence more or less appressed, not always 

 closely. 



Rays about 100; disk 7 to 8 mm. broad 11. E. gilensis. 



Rays 40 to 50 or fewer; disk less than 7 mm. broad. 

 Pappus in 2 series; rays narrow; achenes slightly 



compressed 12. E. modestus. 



Pappus in a single series; rays broader; achenes 

 conspicuously compressed. 



