AND GENERA OF PLANTS. 415 



lanceolate. Stamens and stigmas not exserted, very short. — This plant appears to have no relation 

 to Senecio. The general appearance of the flower is much like that of Chrysanthemum segetum. 



TETRADYMIA. (Decand.) 



Capitulum homogamous, four-flowered. The involucrum of four biserial, foli- 

 aceous, oblong, obtusely carinated sepals, the inner membranaceous on the 

 margins. Receptacle naked and narrow. Corolla tubular, deeply five-cleft, 

 the lobes linear. Branches of the stigma nearly terete, the apex obtuse and 

 hirsute. Achenium turbinate, densely villous with simple hairs. Pappus 

 copious, in many series, the setse all equal, rather rigid and barbellate. — 

 Canescent, much branching, and sometimes spiny shrubs of the plains of 

 the Rocky Mountains or Northern Andes. Leaves alternate, sessile, fasci- 

 culate in the axills, entire and linear. Capituli in terminal fascicles or ra- 

 cemes, pedicellate. Flowers deep yellow. 



Tetradymia canescens, (Decand.;) leaves mucronate; capituli racemose. 



Hab. Oregon; (Douglas.) I have never seen this species, and think it more probable to be a 

 native of California, or the Rocky Mountains. Certainly not along the plains of the north-west 

 coast. 



Tetradymia *inermis; shrubby, much branched, and canescently tomentose; 

 leaves oblong-linear, slightly acute, somewhat clustered; capituli in terminal 

 clusters of three to five, upon short peduncles, the central ones often sessile. 



Hab. On the dry barren plains of the Rocky Mountains. Common, particularly near Lewis' 

 River, of the Shoshonee, but not in the plains of Oregon. A much branched shrub, two or three 

 feet high, whitely canescent with a close soft tomentum, which is also spread over the branches; 

 the branches studded with the cicatrices of former buds. Leaves about three-quarters of an inch 

 long, often obtuse, slightly apiculated. Sepals oblong, obtusely carinated, connected at base, 

 Achenium thickly clad with long simple hairs, beneath which it is entirely hid ; the pappus very 

 copious and long, at length longer than the florets, becoming pale brown, the setae rather slender, 

 and all similar; at length growing out to the length of half an inch. 



Tetradymia spinosa; canescently tomentose, shrubby and much branched ; 

 axills spinescent; leaves linear-oblong, obtuse or acute, clustered, at length 

 nearly smooth ; capituli in terminal clusters, pedunculate. 



Hab. With the above, on the dry plains of Lewis' River, and on Ham's Fork of the Colorado of 

 the West: common. Flowering in July. A very elegant and singular shrub, growing in tufts. 



