246 



ASTER ORDER 



(r) Scales of the pappus 10-20 Hymenopappus 

 (s) Scales of the pappus 4-14 Chaenactis 

 b. Heads green or greenish-yellow, inconspicuous 

 (1) Leaves not lobed or divided 

 (a) Leaves opposite 



IVA 



(b) 



X. 



Leaves alternate 



Fruit a spiny bur with 2 achenes 

 Achenes not in a bur 

 (x) Receptacle chaffy 

 m. Pappus of several scales 

 n. Pappus none 

 (y) Receptacle without chaff; pappus 

 none 

 (2) Leaves lobed to pinnatifid 



(a) Some of the leaves opposite ; spines of 



fruit in 1 row 



(b) Leaves regularly alternate 

 x. Spines of fruit in several rows 

 y. Achenes not in a spiny fruit 



(x) Bracts imbricated, not sharp-pointed Artemisia 



Xanthium 



Dicoria 

 Parthenice 



Artemisia 



Ambrosia 



Franseria 



(y) Bracts in one row, sharp-pointed 

 2. Heads with rays 



a. Receptacle with chaffy scales among the disk- 

 flowers 



(1) Rays not yellow 



(a) Rays white 



x. Leaves finely dissected 



(x) Rays 2-6 



(y) Rays 10-18 

 y. Leaves entire to pinnatifid 



(x) Rays 4-9; pappus none 



(y) Rays 8-13; pappus hairy 

 z. Leaves 2-3-pinnatifid into linear seg- 

 ments ; involucre white-bordered 



(b) Rays pink to purple; chaff spiny 



(2) Rays yellow 



(a) Rays pistillate, i. e., with a style 

 x. Achene broadly winged ; pappus of 2 



awns 

 y. Achene scarcely or not at all winged 

 (x) Rays 2-5 



OXYTENIA 



Achillea 



Anthemis 



Mela m podium 

 Layia 



Leucampyx 

 Brauneria 



XlMENESIA 



