f 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 pubescence
=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 pubescent, 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 principal ones --249.

248a. Stems in clusters; 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 clusters; leaves lanceolate or broader -