More or less hairy, varying to smooth, 3—18 inches high, simple or branching. Leaves spatulate or lanceolate, obtuse, 1—3 inches long, hairy and entire. Heads ¼ of an inch or more broad, single or several, more or less paniculately disposed; involucre hemispheric, its bracts linear and hairy; rays numerous, very narrow, only slightly exceeding the yellow disc, blue or purple. In dry stony ground and slopes throughout the region, very variable as to size; flowering during July. [Sidenote: =Erigeron drobrachiensis= O. Muell.] Nearly or quite smooth, 1—2 feet high, usually paniculately branched. Leaves spatulate to lanceolate, acute, rather numerous. Heads on peduncle-like branches, an inch or more long, involucre, ⅓ of an inch or more broad, scales narrowly lanceolate, attenuate and glandular, green; rays numerous and thread-like, pink, but slightly exceeding the disc. On banks and more or less shaded places at the lower altitudes throughout the Rockies; flowering during July. [Sidenote: =Erigeron philadelphicus= L. _Philadelphia Fleabane._] Soft-hairy or sometimes nearly smooth, stems slender, mostly branched above, 1—3 feet high. Leaves spatulate or obovate, obtuse or acute, dentate or entire, 1—3 inches long. Heads several or numerous, corymbose-paniculate, ¼—⅓ of an inch broad; involucre depressed hemispheric, its bracts linear with roughened margins; rays 100—150, ¼—⅓ of an inch long, bright rose-colour. In open grassy and wet places at the lower altitudes, throughout the Rockies; flowering in June and July. This species, the most widely distributed of any member of the genus, is found throughout North America; though locally rare, where found it is usually in great abundance. [Sidenote: =Aster Richardsonii= Spreng. _Richardson’s Aster._] Hairy, often much branched from the base, 3—12 inches high. Leaves oblong, spatulate to broadly lanceolate, more or less sharply serrate, an inch or more long. Heads solitary, terminating the stem or branches; involucre broadly campanulate, ¼ of an inch high, shorter than the disc; the bracts narrowly lanceolate, with mostly acute and loose herbaceous tips; rays nearly half an inch long, violet-purple. In gravelly ground and river bottoms frequent in the region; flowering during July. [Sidenote: =Aster conspicuus= Lindl. _Large Purple Aster._] Rough, stout, and rigid, 2 feet high. Leaves firm, ovate, oblong, or the lower obovate, acute, 4—6 inches long, 1½—4 inches broad, acutely serrate, reticulate-veiny. Flowers numerous in a broad head, involucre, broadly campanulate, equalling the disc, half an inch high; bracts in several series, minutely glandular, lanceolate, acute, the greenish tips a little spreading; rays ½ an inch long or more, violet. The most showy of all the Asters, frequent in the Rockies at the lower altitudes, on slides and on gravelly river banks, forming great masses of colour when flowering in late July and early August.