OF ARTS AND SCIENCES. 27 



cai'ination without and hollowing within of the axis of the involucral 

 bracts. Weddell's SchJcuhria pusilla, judging from the figure, must 

 either be of this genus or a species connecting it with Bakia. 



ScHKUHRiA, Roth. This genus, after elimination of species which 

 belong to Bahia, is not so closely related to the latter genus, or to 

 Achyropappus, as was supposed. It is completely characterized by its 

 turbinate or obpyramidal involucre, of few bracts with petaloid-mar- 

 gined summit, very few flowers, these either homogamous, or one or 

 two with very short ligule, truly obpyramidal akenes with four equal 



* * Genuine species : palesc of the pappus obovate or spatulate, scarious and 



rounded or truncate at sunnnit, and with a callous-tliickened base. 



-1- Rays white : leaves all opposite, much divided. 

 B. AMBROSioiDES, Lag. — Chili. 



i-t- Rays and disk yellow. — North American. 

 B. opposiTiFOLiA, Nutt. in Torr. & Gray, Fl. Trichophyllum opposilifolitim, Nutt. 

 Gen. The opaque thickish base of the paleas of the pappus extends into a kind 

 of costa, which is evanescent below the summit. 



B. ABSiNTHiiFOLiA, Beutli., whicli passes into its strongly marked variety 

 DEALiJATA. Pappus nearly that of D. ambrosioides. 



§ 2. Herbaceous from a perennial caudex : leaves all alternate and entire, cori- 

 aceous or tliickisli : paieje of the pappus about 10, linear-lanceolate, hyaline- 

 scarious, with a distinct excurrent or percurrent costa: flowers yellow. — 

 Schkahria § Plutyschkuhria, Gray, Proc. Am. Acad. ix. 198, & Am. Nat. viii. 

 213. 



B. NUDiCADLis. — Schkiihriu intefjiifoUa , Gray, 1. c. excl. var. 

 B. OBLOXGiFOLiA. Smaller, witli leafy stem, narrowly oblong leaves; pap- 

 pus little sliorter than tlie glabrate akene; its palea; firmer, smooth, entire-edged. 

 — S. inttyrifolia, var. obloiujij'olia, Gray, 1. C. 



§ 3. Annuals, the last species perhaps biennial, with palmately or pedately 

 parted or divided leaves : akenes all narrow, quadrangular, mostly hirsute 

 along the attenuate base. — Achyropappus, HBK., DC. 



* Leaves mainly opposite and tiie divisions narrowdy linear : paleas of the 

 pappus broad, very obtuse, scarious, with callous-thickened base not extended 

 into a distinct costa. — True Achyropappus. 



H- ]\Iexican species. 

 B. ANTHEMOiDEs, Gra}', Proc. Am. Acad. xv. 40. Achyropappus anihemoides, 

 HBK. Nov. Gen. & Spec. iv. 259, t. 390. 



B. scHKUURioiDES. — Achyropappiis schkuhrioides, Link & Otto, Abh. Neu 

 Gew. Gart. Berl. t. 30, 1828. Schhihria scnecionoides, Nee, Del. Sem. Hort. Bonu. 

 1831. — A close congener of the preceding, and near the following. 

 -t-H- North American (Texano-Arizonian) species, which were referred to 

 ScliLahria in Proc. Am. Acad. ix. 199, with the rest of Achyropappus. 



B. BiGELOvii, Gray, Bot. Mex. Bound. 96. 



B. Neo-Mexicana. — Schkuhria (Achyropappus) Neo-Mexicana,Gray,Fl. Fendl. 



