107a. Inflorescence ovoid or pyramidal =Joe-Pye Weed, Eupatorium purpureum.=
107b. Inflorescence depressed or flattened =Joe-Pye Weed, Eupatorium purpureum var. maculatum.=
108a. Rays yellow or brown --109.
108b. Rays white to blue or red, never yellow or brown --197.
109a. Princ.i.p.al leaves basal, the stem merely with bract-like scales --110.
109b. Princ.i.p.al leaves on the stem, opposite or whorled --111.
109c. Princ.i.p.al leaves on the stem, alternate, or with smaller ones cl.u.s.tered in their axils --132.
110a. Flower-stalk 1-5 dm. high, 1-flowered (spring) =Coltsfoot, Tussilago farfara.=
110b. Flower-stalk 1-3 m. high, several-flowered (summer) =Prairie Dock, Silphium terebinthinaceum.=
111a. Ray-flowers pistillate (the 2-lobed style protrudes from their base) --112.
111b. Ray-flowers with neither stamens nor pistil --118.
112a. Princ.i.p.al leaves lobed (summer) (Leafcup) --113.
112b. Princ.i.p.al leaves toothed or entire, not lobed --115.
113a. Rays 10 or more (1-2 m. high) =Leafcup, Polymnia uvedalia.=
113b. Rays 5 (5-15 dm. high) --114.
114a. Rays shorter than the involucre or none =Leafcup, Polymnia canadensis.=
114b. Rays about 1 cm. long =Leafcup, Polymnia canadensis var. radiata.=
115a. Stem 6 dm. high or less; pappus of slender hairs (spring) =Arnica, Arnica cordifolia.=
115b. Stem usually 8-20 dm. high; pappus of short scales or none (summer) --116.
116a. Leaves united at base into a cup surrounding the stem =Cup Plant, Silphium perfoliatum.=
116b. Leaves closely sessile with a rounded base =Rosin Weed, Silphium integrifolium.=
116c. Leaves tapering to a short petiole; princ.i.p.al leaves whorled =Rosin Weed, Silphium trifoliatum.=
116d. Leaves abruptly rounded at the sessile base, all opposite (Ox-eye) --117.
117a. Leaves smooth =Ox-eye, Heliopsis helianthoides.=
117b. Leaves rough =Ox-eye, Heliopsis scabra.=
118a. Princ.i.p.al stem-leaves lobed or divided --119.
118b. Princ.i.p.al stem-leaves entire or serrate --127.
119a. Submerged aquatic; leaf-segments filiform =Water Marigold, Bidens beckii.=
119b. Terrestrial plants; leaves merely 3-lobed (3-8 dm. high; late spring and summer) (Tickseed) --120.
119c. Terrestrial plants; leaves compound or dissected (summer and autumn) --121.
120a. Leaf-lobes linear-oblong, all about equal =Tickseed, Coreopsis palmata.=
120b. Lateral leaf-lobes very much smaller than the terminal =Tickseed, Coreopsis lanceolata.=
121a. Leaf-segments entire (Tickseed) --122.
121b. Leaf-segments serrate (5-15 dm. high) (Tickseed Sunflower) --124.
122a. Leaf-segments numerous, linear or nearly so (4-10 dm. high) --123.
122b. Leaf-segments 3-5, lanceolate (1-3 m. high) =Tickseed, Coreopsis tripteris.=
123a. Rays yellow throughout =Tickseed, Coreopsis verticillata.=
123b. Rays brown, at least at the base =Tickseed, Coreopsis tinctoria.=
124a. Achenes wedge-shape, the inner ones less than 2 mm. wide --125.
124b. Achenes obovate, the inner ones more than 2 mm. wide =Tickseed Sunflower, Bidens aristosa.=
125a. Leaf-lobes lanceolate =Tickseed Sunflower, Bidens trichosperma.=
125b. Leaf-lobes linear =Tickseed Sunflower, Bidens trichosperma var. tenuiloba.=
126a. Outer leaf-like bracts 10-16; achenes brown =Beggar Ticks, Bidens vulgata.=
126b. Outer leaf-like bracts 5-8; achenes black =Beggar Ticks, Bidens frondosa.=
126c. Outer leaf-like bracts about 4 =Beggar Ticks, Bidens discoidea.=
127a. Bracts of the involucre all essentially alike in form and texture (flowers in summer and autumn) (Sunflower) --179.
127b. Bracts of the involucre in two distinct sets, differing in form or consistency or both --128.
128a. Leaves entire (3-8 dm. high; late spring and summer) --120b.
128b. Leaves serrate (late summer and autumn) (Bur Marigold) --129.
129a. Rays large and conspicuous, 2-3 cm. long (3-10 dm. high) =Bur Marigold, Bidens laevis.=