AND GENERA OF PLANTS. 361 



Hab. Georgia. (Dr. Baldwyn.) A small species, about a foot high, with long, narrow, linear 

 entire leaflets, sometimes with here and there a distant gash. Flower rather small, rays nearly 

 entire. 



§ I. *Meduse^. — Outer involucrum very hng and squarrose, of trventy to 

 trventy-four leaves! the inner eight-leaved. Achenium ciliate, terminated by 

 two very short teeth. 



Diodonta inwlucrata. Coreopsis involucrata; Nutt. in Journ. Acad. Nat. 

 Sci. Philad., Vol. VII., p. 74. Very remarkable for the singular involucrum, 

 which, while all the other parts of the plant are smooth, has its segments 

 strongly ciliated with rigid hairs. I have not seen the mature achenium. 



§? II. * Heterodonta. 



Bidens, but with the outer, foliaceous involucrum three to four-leaved, the 

 inner about six-leaved, elongated. Rays two or three, very short, not ex- 

 serted. Stigma smooth, with a small conic point. Achenium linear, flatly 

 compressed, without angles at the sides or summit, hirsute, immarginate. 

 Pappus of two long, diverging, hispid bristles, with the hairs erect, not re- 

 trorse! radial, abortive fruit, with very short awns. — A dwarf, much branched 

 annual? with opposite, lanceolate-linear, incisely serrated leaves, attenuated 

 at each extremity. Flowers solitary, terminal; scales of the involucrum 

 yellowish. Discal florets shorter than the awns, campanulate with a very 

 slender tube. — (The name in allusion to the erect, instead of reverted bris- 

 tles of the teeth of the achenium.) 



Diodonta * Bidentoides. 



Hab. The vicinity of Philadelphia? With entirely the aspect of the dwarf variety oi Bidens 

 cernua, but with the capitulum almost obconic-oblong. Height two or three inches, spreading out 

 five or six inches ; l6aves attenuated into long petioles, somewhat connate at base. 



A second species of this section, or rather genus, occurs in the south-west, and will be described 

 by Mr. Gray. 



*COSMIDIUM. (§. CosMiDiuM of Coreopsis, Gray.) 



Coreopsis, but with the discal florets long, tubular and campanulate, deeply 

 five-cleft. Achenium subcylindric, usually tubercular and indurated, with 



VII.— 4 Q 



