ASTERACEAE 





2. Leaves pinnately divided 



a. Annual; fertile heads clustered; involu 



b. Perennial; fertile heads solitary; involu i 





Bidens— Biden . 



I I at. bi-, two, dens, tooth, 1 '.■■ 



1. Heads yellow 



a. Heads nodding after flowering 



b. Heads always erect 



( 1) Rays i onspii uou >; heads l 6 



(2) Rays small or wanting; heads 1 4 cm. 



(a) Leaves not divided 



x. Outer bracts 2-4 times longer than 

 y. Outer bracts not longer than hi 



(b) Leaves pinnately 3-5-divided 



2. Heads red 



Centaurea — Bachelor's Button, Bluel 



(Gr. nam.- 



K'-.'fe 



Head of bluebottle, Centaur< 

 Leaves gray, linear; rays blue, more rarely white or pink 



