This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erigeron Bellidiastrum Nutt. Trans. Am. Phil. Soc. (II) 7: 307. 1841.
Annual, much branched, 6'-15' high, cinereous-pubescent throughout. Leaves entire, linear-spatulate, the lower and basal petioled, l'-1 1/2' long, the upper sessile and smaller; heads several or numerous, 5"-8" broad; involucre hemispheric, about 2" high, its bracts linear, hirsute, acute; rays 30-65, purplish, about 2" long; pappus a single series of capillary bristles.
In moist soil, South Dakota to Nebraska, Kansas, Texas, Wyoming and Arizona. May-July.
Aster annuus L. Sp. Pl. 875. 1753.
Erigeron annuus Pers. Syn. 2: 431. 1807.
Annual, sparingly pubescent with spreading hairs; stem erect, corymbosely branched, 1 °-4° high. Leaves thin, the lower and basal ones ovate or ovate-lanceolate, mostly obtuse, petioled, usually coarsely dentate, 2'-6' long, l'-3' wide, the upper sessile or short-petioled, lanceolate, oblong, or linear-lanceolate, acute or acuminate, mostly sharply dentate in the middle, those of the branches narrower and often entire; heads rather numerous, $"-7" broad, mostly short-peduncled; bracts of the hemispheric involucre somewhat hispid; rays 40-70, linear, white, or commonly tinged with purple, 2"-4" long; pappus double, the inner a series of slender fragile deciduous bristles, often wanting in the ray-flowers, the outer a persistent series of short, partly united, slender scales.
5: 1838. Erigeron ramosus B.S.P. Prel. Cat. N. Y. 27. 1888. Erigeron ramosus Beyrichii Smith & Pond, Bot. Surv.
Neb. 2:11. 1893.
Resembles the preceding species, but is usually lower and the pubescence more appressed. Stem leaves linear-oblong or linear-lanceolate, nearly all of them entire; basal and lowest spatulate or oblong, usually serrate; bracts of the involucre glabrous or nearly so; pappus similar to that of the preceding; rays white, or sometimes purplish, occasionally minute or wanting.
In fields, Nova Scotia to British Columbia, Florida, Louisiana, Texas and California. Naturalized in Europe. White-top. May-Nov.
Erigeron tenuis T. & G. Fl. N. A. 2: 175. 1841.
Annual or biennial, branched from the base and sometimes also above, strigose-pubescent; stems slender, erect or ascending, 1° high or less. Basal leaves obovate to spatulate, 1'-2 1/2' long, 3"-6" wide, usually toothed; stem leaves linear or linear-oblong, toothed or entire; heads several or solitary, slender-peduncled, 7"-10" broad; involucre 2"-3" high, its linear bracts glabrous or sparingly pubescent; rays white or purplish, numerous; pappus of ray-flowers and disk-flowers alike, of few long bristles and short small scales.
Moist prairies and plains. Missouri to Texas and Louisiana. April-May.