300 DESCRIPTIONS OF NEW SPECIES 
*DIETERIA. 
Flower radiate, rays styliferous, fertile? liguli one or two series, broadish, those 
of the disk hermaphrodite, fertile. Stigma filiform, hirsute and exserted. 
Sepals of the involucrum, for the most part, closely imbricated in two to four 
series, Scariose and carinate, the tips usually reflected and herbaceous. Re- 
ceptacle flat or convex, alveolate, the alveole deep, with toothed and lace- 
rated margins. Achenium obovate, subcylindric, ten to fifteen striate, pubes- 
cent. Pappus of several series, scabrous and unequal, that of the ray shorter 
and less copious.—Annual or biennial, (in one anomalous species perennial, ) 
divaricately branching herbs, more or less pubescent; leaves nearly entire, 
incisely serrate or pinnatifid, the points often pungently mucronulate. Flow- 
ers fastigiate. The disk yellow. Liguli red or purple—Allied to Aster, 
but with the involucrum regular; the achenia convex, distinctly striate 
when ripe; the receptacle deeply alveolate; the pappus of the ray different 
from that of the disk; the leaves incise or pinnatifid, and the duration only 
to the first period of flowering. They are also allied to the first section of 
Heterotheca by the deficient pappus of the ray, but that of the disk is simple, 
and the rays are purple. The whole plant bitter to the taste.—(So called 
from their biennial duration. ) 
+ Involucrum subovate, of three or four series of scales. 
Dieteria canescens; leaves entire, linear, sessile, radical spathulate; stem low 
and much branched, canescently villous, as well as the involucrum; flowers 
fastigiate ; rays about eighteen to twenty; pappus very slender. 
Has. On the denuded banks of the Missouri. Aster canescens, Pursu, Bor. Am., Vol. II., p. 
547. _ Not in the least allied to Aster multifiorus. A. biennis, Nutt. Gen. Am., Vol. IL., p- 155. 
I doubt if the leaves are always entire, a fact so contrary to all the rest of the genus to which it is, 
in all other respects, so intimately allied. 
Dieteria * pulverulenta; minutely pubescent, leaves linear sessile, below here 
and there incisely serrulate, above entire; stem divaricate; flowers fastigiate, 
upon rather naked branchlets; involucrum almost hemispherical; rays eight to 
twelve. 
