STUDIES IN THE COMPOSITJE. 47 
lication, that is, Xylorrhiza. But I could not, at this junc- 
_ ture, leave out of consideration another set of suffrutescent 
-  asteraceous plants in habit different from both Stenotus and 
_ Xylorrhiza, which are also almost as foreign as either to true 
- Aster, but which may in some way more easily conjoin them- 
- selves to Xylorrhiza than to Stenotus. It was largely in ref- 
erence to these few half-shrubby, but more freely branching, 
cyanic plants of southwestern deserts that I long since de- 
termined to present as distinct genera Stenotus and Xylor- 
rhiza. I here present the species, as far as they are known 
- to me, under the two groups. 
XvLoRRHIZA proper (Nutt. Trans. Am. Phil. Soc. vii. 297, 
1840). Stems low, with erect leafy monocephalous branches ; 
leaves entire. 
1. X. GLABRIUSCULA, Nutt. l.c. Aster glabriusculus, Torr, 
& Gray, Fl. ii. 159 (1841).—Western. Wyoming, in clayey 
soils or among rocks. 
.. 92. X. virnosa, Nutt. l.c. Aster Xylorrhiza, Torr. & Gray, 
l. c. 158. — Habitat of the preceding, and very distinct from 
3 it, though less common. 
|. 8. X. Pannyr Aster Parryi, Gray, Am. Nat. viii. 212 
- (1874). A.venustus, Jones, Zoe, ii. 247 (1891).—Southwestern 
. Wyoming and adjacent Utah. Plant differing from the two 
preceding in general aspect, being more leafy below, with . 
fewer and larger long-peduncled heads, thus connecting 
with the succeeding. 
Subgenus Mecatastrum. Larger, more freely branching ; 
aves more or less toothed or serrate. 
4. X. Wnrenrnu. Aster? Wrightii, Gray, Pl. Wright. ii. 
75 (1853). Townsendia Wrightii, Gray, Bot. Mex. Bound. 
18. be —On the lower. Rio Grande, ' Texas. 
