226b. Leaves serrate --228.

227a. Leaves glabrous above =Aster, Aster shortii.=

227b. Leaves rough above =Aster, Aster azureus.=

228a. Involucre 4-6 mm. long --229.

228b. Involucre 6-10 mm. long --230.

229a. Leaves rough; petioles mostly winged =Aster, Aster lowriea.n.u.s.=

229b. Leaves smooth; petioles slender, not winged =Aster, Aster cordifolius.=

230a. Heads few, seldom more than 10, in a loose spreading cl.u.s.ter =Aster, Aster lindleya.n.u.s.=

230b. Heads numerous, in a rather elongate crowded cl.u.s.ter =Aster, Aster sagittifolius.=

231a. Stem hirsute or rough-p.u.b.escent --232.

231b. Stem smooth, or essentially so --236.

232a. Leaves conspicuously serrate =Aster, Aster puniceus.=

232b. Leaves entire or nearly so --233.

233a. Leaves narrowed toward the base and barely clasping, linear or oblong-linear --234.

233b. Leaves ovate-oblong or lanceolate, with a broad conspicuously clasping base --235.

234a. Involucre p.u.b.escent but not glandular =Aster, Aster amethystinus.=

234b. Involucre glandular =Aster, Aster oblongifolius.=

235a. Involucre very glandular and viscid; rays very numerous, violet-purple; leaves lanceolate =Aster, Aster novae-angliae.=

235b. Involucre slightly glandular or not at all; rays 20-30, generally blue-purple; leaves ovate-oblong =Aster, Aster patens.=

236a. Leaves of a linear type --237.

236b. Leaves broader than linear, at least 1 cm. wide --238.

237a. Bracts narrow, approximately equal in length --253a.

237b. Bracts of several lengths, the outer successively shorter --256a.

238a. Leaves smooth above =Aster, Aster laevis.=

238b. Leaves rough above --239.

239a. Leaves contracted below the middle and then abruptly dilated to the clasping base =Aster, Aster prenanthoides.=

239b. Leaves gradually narrowed toward the base =Aster, Aster puniceus.=

240a. Rays conspicuous --241.

240b. Rays minute or wanting =Aster, Aster angustus.=

241a. Stems and leaves gray with a silky p.u.b.escence =Aster, Aster sericeus.=

241b. Stem and leaves green, not silky --242.

242a. Bracts glandular-viscid; rays violet =Aster, Aster oblongifolius.=

242b. Bracts bristly-ciliate --243.

242c. Bracts smooth or p.u.b.escent, not glandular or bristly-ciliate --244.

243a. Leaves crowded, rigid; rays white =Aster, Aster multiflorus.=

243b. Leaves not crowded and rigid; rays blue --234a.

244a. Bracts narrowed at the tip into thickened firm green awl-shape points --245.

244b. Bracts acute or obtuse at the flattened tip --247.

245a. Involucre 4-5 mm. long --246.

245b. Involucre 7-8 mm. high =Aster, Aster polyphyllus.=

246a. Stem smooth =Aster, Aster ericoides.=

246b. Stem hairy; leaves linear =Aster, Aster ericoides var. villosus.=

246c. Stem densely white-woolly =Aster, Aster ericoides var. platyphyllus.=

247a. Leaves at most 4.5 cm. long --248.

247b. Leaves larger, at least the princ.i.p.al ones --249.

248a. Stems in cl.u.s.ters; leaves rigid, linear, with 1 vein; flowers blue =Aster, Aster linariifolius.=

248b. Stem solitary; leaves not rigid; flowers rose-pink =Aster, Aster nemoralis.=

249a. Heads solitary at the end of minutely leafy branchlets; leaves linear =Aster, Aster dumosus.=

249b. Heads in flat-topped cl.u.s.ters; leaves lanceolate or broader --250.

249c. Heads in more or less one-sided racemes --251.