244 American Midland Naturalist Monograph No. 4 



never be confused with sagebrush which has a strong aromatic odor nor with 

 Acamptopappus which has conspicuous globose heads with fringed invoiucral 

 bracts. They may be distinguished from the snakeweeds by the numerous 

 white hair-like pappus bristles. The pappus of the snakeweeds consists of 

 several short scales. (Syn. Haplopappus.) 



Field Guide to the Species 



A. Leaves not toothed, lobed, nor divided. 



Flower heads small, mostly 1/6 to nearly 1/3 inch high, borne m compact flat- 

 topped clusters; involucres surrounding the flower heads narrowly top- 

 shaped; leaves conspicuously dotted with small resm pits; petal-like ray 

 flowers lacking (rarely present in A. cuueatus) ; found in California parks. 



Leaves narrowly linear 1. A. arborescens. 



Leaves spatula-shaped or wedge-shaped 2. A. cunealus. 



Flower heads larger, mostly 1/3 to % inch high, borne singly or in loose clusters; 

 involucres narrowly bell-shaped to broadly hemispheric ; leaves not dotted 

 with resin pits (except A. Unearif olms) ; species not restricted to Califor- 

 nia parks. 



Leaves dotted with conspicuous resin pits; petal-like ray flowers present; bracts 



of involucre papery white; large or medium-sized shrubs 



3. A. Unearif alius. 



Leaves not dotted with resin pits, sometimes sticky-glandular; low shrubs or 

 semi-shrubs. 



Heads borne singly on nearly naked stems; involucre of pule papery 

 bracts; plants low, scarcely shrubby; ray flowers present. 

 Invoiucral bracts sharp-pointed at the tips, often with middle part 

 greenish, not green at tips; outer bracts not regularly shorter 

 4. A. acaulis. 



Invoiucral bracts blunt at tips, the outer regularly shorter, greenish at 



the tips 5. A. armerioides. 



Heads borne on leafy stems or in leafy clusters; involucre of loose bracts, 

 these often leaf-like. 



Stems densely white-felty; leaves green, glandular; petal-like ray 



flowers lacking 6. A. macrouema. 



Stems only thinly if at all while-woolly (white-woolly in one var. of 



A. Bloomeri) ; ray flowers usually present. 



Heads large, 20- to 40-flowered; bracts of involucre not overlap- 

 ping in unequal rows 7. A. suffruticosus. 



Heads smaller, 6- to 23-flowered; bracts of involucre loosely 

 overlapping in unequal rows. 



Bracts of involucre papery, only the tips green, the margins 

 frayed; leaves usually not more than about 1/6 

 inch wiae 8. A. Bloomeri. 



Bracts of involucre mostly green and herbaceous, the outer 

 often leaf-like; leaves up to '/4 inch wide; found 

 at Crater Lake National Park 9. A. Creenei. 



B. Leaves toothed, lobed or divided. 



Plants tall shrubs; flower heads small, cylindric, less than }/4 inch broad; ray flowers 



none 10.^. acraJenius. 



Plants scarcely shrubby; flower heads large, the involucres % to % inch broad, ^/^ 

 to I/2 inch high. 



