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.=