COMPOS1TAE (THISTLE FAMILY) 



44 BlDENS. 



1 a Plant growing in water, the submerged leaves dissected 



into capillary segments. .WATER MARIGOLD. (B. beckii.) 

 b Plants not growing in water 2 



2 a Ray flowers present, */4 in. or more long 3 



b Ray flowers wanting or less than ^4 in. long 5 



3 a Leaves pinnately divided into 3-7 leaflets 



TICK-SEED SUNFLOWER. (B. trichosperma.) 

 b Leaves toothed, not pinnately divided 4 



4 a Heads 1-3 in. broad; bases of opposite leaves not joined 



around the stem. ... SMOOTH BUR-MARIGOLD. (B. laevis.) 

 b Heads %-i in. broad; bases of opposite leaves often 



joined around the stem STICK-TIGHT. (B. cernua.) 



5 a Lower leaves lanceolate to oblong, toothed but not 



pinnately divided 6 



b Lower leaves pinnately divided into 3-5 leaflets .... 8 



6 a Outer bracts of involucre 1-3 in. long, lanceolate, 



usually toothed. . .LEAFY-BRACTED TICKSEED. (B. combsa.) 

 b Outer bracts of involucre i in. or less long, entire. ... 7 



7 a Leaves sessile; heads nodding after flowering 



STICK-TIGHT. (B, cernua.) 

 b Leaves petioled ; heads erect after flowering 



SWAMP BEGGAR-TICK. (B. connata.) 



8 a Achenes %-% in. long, much longer than the bracts; 



outer bracts of involucre about the length of the 



inner SPANISH NEEDLES. (B. bipinnata.) 



b Achenes less than l /2 in. long; outer bracts of involucre 



much longer than the inner 9 



9 a Heads V^-V-2 in. broad; outer bracts of involucre usu- 



ally 4 SMALL BEGGAR-TICK. (B. discoidea.) 



b Heads 1 X>-% in. broad; outer bracts of involucre usu- 

 ally 5-8 BEGGAR-TICK. (B. frondbsa.) 



45 GALINS6GA GALINSOGA. ( G. parviflbra.) 



46 ARCT6TIS ARCTOTIS. (A. breviscapa*) 



47 HELENIUM SNEEZEWEED. (H. autumnale.) 



48 ACHILLfeA. 



i a Ray flowers 4-6 YARROW. (A. millefblium.) 



b Ray flowers numerous WHITE TANSY. (A. ptdrmica*) 



49 ANTHEMIS. 



1 a Ray flowers yellow YELLOW CAMOMILE. (A. tinctbria*) 



b Ray flowers white 2 



2 a Cultivated, aromatic species 



GARDEN CAMOMILE. (A. nbbilis*) 

 b Wild species 3 



236 



