262 ASTER FAMILY 



receptacle flat, without chaff, involucre bell-shaped or hemispheric, the 

 bracts nearly equal, in 1-2 rows; heads solitary or in corymbs; leaves op- 

 posite or alternate, parted or divided ; annual or perennial. 



1 . Perennial from a woody root ; rays 5-6, short ; 



leaves 3-5 parted B. oppositifolia 



2. Annual 



a. Rays present ; leaves mostly alternate B. dissecta 



b. Rays none ; leaves mostly opposite B. neo-mexicana 



BALSAMORRHIZA Hooker 1833 BALSAM ROOT 

 (Gr. balsamon, balsam, rhiza, root) 



Heads with yellow ray-flowers, disk-flowers yellow, perfect, achenes 

 of the ray-flowers 3-angled or flattened, of the disk-flowers 4-angled ; re- 

 ceptacle flat or convex with lance-linear chaff, involucre broad, the bracts 

 imbricated or nearly equal and the outer enlarged; heads mostly solitary 

 on few-leaved or naked stalks; leaves large, mostly basal, simple to pin- 

 natifid; perennial. 



1. Leaves entire or toothed B. sagittdta 



2. Leaves, or some of them, pinnatifid 



a. Stems and leaves smooth or slightly hairy B. macro phylla 



b. Stems and leaves white-hairy to woolly B. incdna 



BIDENS Linne 1753 BEGGAR'S TICKS, BUR-MARIGOLD 



(Latin bi- f two, dens, tooth, from the pappus) 



PL 40, fig. 1. 



Heads with white or yellow neutral rays or none, disk-flowers perfect, 

 yellow to brown, achenes flat, angled or rounded, wedge-shaped to linear, 

 pappus of barbed awns; receptacle flat, with chaff, involucre bell-shaped 

 to hemispheric, bracts in 2 rows, separate or somewhat united at the base, 

 the outer often larger and leaf-like; heads solitary or in corymbs or pani- 

 cles; leaves opposite, or alternate above, toothed, lobed or dissected; an- 

 nual or perennial. 



1. Leaves simple, toothed 



a. Rays present B. levis 



b. Rays none B. comosa 



2. Leaves, or some of them, divided or dissected 



a. Rays none ; achenes oval to obovate, flat, 2- 



awned B. frondosa 



b. Rays present ; achenes long-linear, angled, 2-4- 



awned 



