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.