202b. Flower-cl.u.s.ters very convex =Yarrow, Achillea lanulosa.=

203a. Princ.i.p.al leaves pinnatifid --213a.

203b. Princ.i.p.al leaves 1-3 times pinnately parted or dissected --204.

204a. Leaf-segments very narrowly linear; leaves 2-3-pinnate --205.

204b. Leaf-segments linear or lanceolate; heads 2.5-5 cm. wide =Camomile, Anthemis arvensis.=

204c. Leaf-segments ovate to ovate-oblong; heads 1-2 cm. wide =Feverfew, Chrysanthemum parthenium.=

205a. Foliage strongly scented =Dog Fennel, Anthemis cotula.=

205b. Foliage not ill-scented =Wild Camomile, Matricaria inodora.=

206a. Heads 3-6 mm. broad, including the rays (summer and autumn) --207.

206b. Heads 7 mm. broad or larger, including the rays --209.

207a. Rays purple (1-4 dm. high) =Horse Weed, Erigeron divaricatus.=

207b. Rays white --208.

208a. Leaves obovate to oblong (3-10 dm. high) --135a.

208b. Leaves linear or narrowly lanceolate (2-25 dm. high) =Horse Weed, Erigeron canadensis.=

209a. Pappus none, or minute and not of hairs (summer and autumn) --210.

209b. Pappus of hairs --214.

210a. Disk-flowers purple or brown (4-12 dm. high; rays pink) (Purple Coneflower) --211.

210b. Disk-flowers yellow or nearly white --212.

211a. Leaves ovate or ovate-lanceolate, most of them serrate =Purple Coneflower, Brauneria purpurea.=

211b. Leaves narrowly lanceolate, gradually narrowed at the base, entire =Purple Coneflower, Brauneria pallida.=

212a. Rays broadly obovate; heads 1-2 cm. wide (3-6 dm. high) =Sneezewort, Achillea ptarmica.=

212b. Rays oblong or narrowly elliptical --213.

213a. Leaves serrate (3-10 dm. high) =Ox-eye Daisy, Chrysanthemum leucanthemum var. pinnatifidum.=

213b. Leaves entire (8-25 dm. high) =Boltonia, Boltonia asteroides.=

214a. Involucral bracts all the same length or nearly so and narrow, or with a few short outer ones; plants blooming in spring and summer, or a few plants persisting in bloom until autumn (Fleabane) --215.

214b. Involucral bracts unequal, the outer successively shorter (or rarely nearly equal), loosely or closely overlapping; plants 3-15 dm. high, blooming in late summer and autumn (Aster) --221.

215a. Rays short and inconspicuous, barely longer than the pappus (1-5 dm. high; summer) =Fleabane, Erigeron acris var. asteroides.=

215b. Rays conspicuous, spreading, 3 mm. long or more --216.

216a. Rare plants of the Northern Peninsula, with entire leaves and stems 1-5 dm. high, from a thick woody root (flowers white or purple, summer) --217.

216b. Common species, with erect stems from fibrous roots; leaves toothed (except in one species) --218.

217a. Heads 3-5 cm. wide; rays about 100 =Fleabane, Erigeron glabellus.=

217b. Heads 1-2 cm. wide; rays 20-30 =Fleabane, Erigeron hyssopifolius.=

218a. Stem unbranched, except for the peduncles; leaves chiefly basal; heads 1-9 (2-5 dm. high; flowers pale-purple, spring) =Fleabane, Erigeron pulch.e.l.lus.=

218b. Stem branched; princ.i.p.al leaves on the stem; heads usually numerous (3-12 dm. high; spring and summer) --219.

219a. Stem-leaves linear, entire =Fleabane, Erigeron ramosus.=

219b. Stem-leaves ovate-lanceolate, the princ.i.p.al ones toothed --220.

220a. Rays 100 or more, light-purple or pink =Fleabane, Erigeron philadelphicus.=

220b. Rays much fewer, white =Fleabane, Erigeron annuus.=

221a. Basal leaves petioled and heart-shape at the base --222.

221b. Basal leaves not petioled; stem-leaves with heart-shape clasping bases --231.

221c. Basal and stem-leaves sessile or petioled, but never heart-shape or clasping --240.

222a. Rays white or violet --223.

222b. Rays blue --225.

223a. Plant glandular, especially on the pedicels and branches of the inflorescence =Aster, Aster macrophyllus.=

223b. Plant not glandular --224.

224a. Leaves rough above =Aster, Aster schreberi.=

224b. Leaves smooth above =Aster, Aster divaricatus.=

225a. Stem-leaves clasping the stem by a cordate base =Aster, Aster undulatus.=

225b. Stem-leaves not cordate-clasping --226.

226a. Leaves entire --227.