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1 Petals usually 5, white with a reddish mark near the cordate base of the petal blade; buds glutinous (sticky); fruit spiny; leaflets 7 (-9) per leaf; [alien, uncommonly planted, rarely naturalized]; [section Aesculus]
1 Petals 4 (or 4-5 in A. parviflora), cream-colored, yellow, red; or white (and then lacking a red blaze); buds not glutinous; fruit smooth (or with some prickles in A. glabra var. glabra); leaflets 5 (-7) per leaf; [native].
..2 Petals white, unmarked with red; stamens exserted, 2-4× as long as the petals; inflorescence 2-5 dm long; [section Macrothyrsus]
..2 Petals cream-colored, yellow, or red; stamens included or exserted, 1-2× as long as the petals; inflorescence 1-2.5 dm long; [section Pavia].
....3 Stamens about 2× as long as the petals, well-exserted beyond the corolla; petals only slightly unequal in size; fruit spiny with short prickles (rarely essentially smooth).
......4 Leaflets on well-developed leaves mostly 7-11; leaflets 1-3 (-5) cm wide