196 PROCEEDINGS OF THE AMERICAN ACADEMY 



::= = Leaves thinner, sometimes membranaceous : bracts of the 

 involucre chiefly linear, obtuse. 



S. Leavenworthii, Torr. & Gray. Southern Atlantic States near 

 the coast. 



S. RUPESTRis, Raf. Probably an extreme glabrous and slender form 

 of S. Canadensis, growing in shade. 



S. SEROTiNA, Ait., which, as already stated, is the S. gigantea of 

 Willdenow and American botanists, the S. glabra, Desf. ; and a 

 form of it S. Pitcheri of Nuttall. — Its var. gigaxtea, that is, »S'. 

 gigantea, Ait., but the serotitia of Willdenow and of later authors, 

 differs only and very variably in having some pilose or hirsutulous 

 pubescence on the veins or the under surface of the leaves. 



•H- -H- Minutely pubescent or glabrate, not cinereous or scabrous : 

 leaves thinnish, veiny, and with lateral ribs sometimes evident 

 but often obsolete : panicle usually erect and thyrsiform, with 

 the heads hardly at all secund : involucral bracts small, thin 

 and narrow. Intercalated between the j^receding and the fol- 

 lowing, to both which the species are nearly related, yet as 

 much so to S. rvgosa. Northwestern species. 



S. LEPiDA, DC. Not too well distinguished from the next, by 

 its fewer and larger usually glomerate heads, little surpassing 

 the upper leaves, and the subulate-linear acute involucral bracts. 

 Belongs to the Northwest Coast, Alaska, &c. 



S. ELONGATA, Nutt. S. stricta, Less, in Linnasa. S. elata, Hook. Fl. 

 Eastward it seems to pass into S. Canadensis. 



++ -H- ++ At least the stem pubescent or hispidulous-scabrous, 

 either hirsutely or canescently : branches of the panicle when 

 well developed secund. 



= Leaves tapering gradually to an acute or acuminate apex : 

 panicle open : bracts of the involucre narrow and thin : rays 

 small and short. 



S. Canadensis, L. Also the original S. altissima, L., founded on 

 Martyn's Hist. PI. 14, t. 14, but not of most subsequent authors, 

 who have followed the conjectural references to Dill. Elth. (See 

 S. rugosa.) S. rejiexa^ Ait., Willd., &c. S. nutans. Desf. S. fongi- 

 folia, Schrader in DC. — Var. procera, Torr. & Gray, the X pro- 

 cera, Ait., &c., and S. eminens, Bischoff. — Var. scabra, Torr. & 

 Gray. Chiefly a southern form, apparently extending well into 



