932 Compositae Aster 



purple. (See excluded species no. 625, p. 1097) 



A . amethystinus. 



Involucral bracts not as above: 



Involucres mostly 6-9 mm long, their bracts essentially of the 

 same length, in 2 loosely imbricated rows; plants of wet 

 places with stems 5 mm or more in diameter near the base. 



Branches usually much exceeding the subtending leaves 



. 21. A. puniceus. 



Branches shorter than the subtending leaves. 



Leaves elongate-lanceolate, hispid on the midrib beneath. 



21a. A. puniceus var. demissus. 



Leaves subrhomboidal, smooth or sparingly hispidulous be- 

 neath 21b. A. puniceus var. compactus. 



Involucres not as above; plants of a dry habitat; stems less 



5 mm in diameter, near the base. 



Rays violet purple; median stem leaves more than 12 mm 



wide, their basal lobes usually developed so that the 



leaves appear perfoliate; heads large, 20 mm wide or 



more, solitary or a few together at the ends of long 



branches, rarely racemose 10. A. patens. 



Rays white; median stem leaves mostly less than 5 mm 

 wide; heads small, 6-8 mm wide. 

 Pubescence of stem dense and spreading. .22. A. exiguus. 



Pubescence of stem not dense, upwardly appressed 



23. A. ericoides. 



B. Stem leaves sessile or sometimes the lower on very short petioles (petiolate in 

 no. 27), not at all clasping, 

 a. Leaves more or less pubescent over the entire under surface. 



Blades silky-pubescent above and beneath 24. A. sericeus. 



Blades not silky-pubescent above and beneath. 



b. Involucral bracts (at least the outer ones) and leaves of the branchlets 

 with mucronate tips. 

 Rays blue or violet. 



Plants glabrous or nearly so; bracts with recurving tips. (See 



excluded species no. 631, p. 1098) A. novi-belgii. 



Plants pubescent. 

 Bracts glandular. 



Pubescence of stem and branches spreading 



11. A. oblongifolius. 



Pubescence of stem and branches not dense, upwardly appressed. 



11a. A oblongifolius var. rigididus. 



Bracts not glandular, linear and long-acuminate, more or less 

 tinged with purple. (See excluded species no. 625, p. 1097. 



A. amethystinus. 



Rays white. 



Stems more or less densely pubescent. 



Bracts (at least the lower ones) with recurved tips, stout, hispid 

 and hispid-ciliate or only hispid-ciliate; heads small, densely 

 clustered. 

 Pubescence of stems dense and spreading; bracts, at least the 



outer ones, hispid on the back 22. A. exiguus. 



Pubescence of stem not dense, upwardly appressed; bracts gen- 

 erally glabrous on the back 23. A. ericoides. 



Bracts appressed, not stout; heads larger than in the preceding, 

 usually not in clusters. 

 Bracts generally more than 7 mm long. (See excluded species 

 no. 633, p. 1098) A. polyphyllus. 



