946 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



1. Ambrosia aptera DC, Prodr. 5: 527. 1836. 



Ryan Ranch (southern Apache County), Rice (Gila County), Gra- 

 ham, Cochise, Santa Cruz, and Pima Counties, 2,300 to 5,000 feet, 

 roadsides and bottom lands, July to October. Illinois to Colorado, 

 south to Texas, Arizona, and northern Mexico. 



2. Ambrosia psilostachya DC, Prodr. 5: 526. 1836. 



Ambrosia coronopifolia Torr. and Gray, Fl. North Amer. 2: 

 291. 1842. 



White Mountains (Apache County), Flagstaff (Coconino County), 

 Prescott (Yavapai County), south to Cochise and Pima Counties, 

 3,200 to 7,000 feet, along streams and at roadsides, July to October. 

 Illinois to Saskatchewan and Washington, south to northern Mexico. 



3. Ambrosia artemisiifolia L., Sp. PL 988. 1753. 



Ambrosia elatior L., Sp. PL 987. 1753. 



Sierra Ancha, Gila County, about 6,000 feet, in a meadow (Harrison 

 and Kearney 8317). A common weed nearly throughout the United 

 States and southern Canada. 



50. FRANSERIA. Bur-sage 



Plants with the characters of Ambrosia but with the pistillate 

 involucre armed with spines or prickles in more than 1 series, and 

 1- to 4-flowered. 



Key to the species 

 1. Plants herbaceous (2). 



2. Fruit (mature pistillate involucre) 2 to 4 mm. long, obovoid, armed with 

 about 10 to 20 hooked spines, these 0.8 mm. long or less. 



1. F. CONFERTIFLORA. 



2. Fruit usually 4 to 8 mm. long, the spines longer, rarely hooked (3). 



3. Leaves ovate or deltoid in outline, once to thrice pinnatifid, green or 

 merely slightly paler beneath; fruit 4 to 8 mm. long, 1-beaked, armed 

 with 6 to 30 strongly flattened straight spreading spines, these 2 to 



5 mm. long; annual 2. F. acanthicarpa. 



3. Leaves mostly oblong in outline, interruptedly bipinnatifid with a strongly 

 toothed or lobed rachis, green above, densely canescent-strigillose 

 beneath; fruit 3.5 to 6 mm. long, 2- or 3-beaked, bearing about 4 to 9 

 thick-subulate rarely hooked spines, these 1 to 2 mm. long and flattened 



only at base; perennial from running rootstocks 3. F. discolor. 



1. Plants shrubby, at least at base (4). 



4. Leaves canescent-pubescent beneath (5). 



5. Leaves once to thrice pinnately divided into small mostly ovate or obovate 

 divisions, canescent-strigillose on both faces; fruit 4 to 6 mm. long, 

 bearing about 25 to 40 rigid flattened straight spines__ 4. F. dumosa. 

 5. Leaves ovate to oblong, not pinnately divided into small divisions, 

 greenish above, densely canescent-tomentulose beneath; fruit other- 

 wise (6). 

 6. Leaves subsessile, sinuate-toothed to pinnatifid; fruit fusiform, 8 to 

 10 mm. long, 1-beaked, glandular and densely long-villous, especially 



on the 20 or fewer straight subulate spines 5. F. eriocentra. 



6. Leaves distinctly petioled, serrate or serrulate; fruit turbinate-ovoid 

 or turbinate-subglobose, about 6 mm. long, 2- or 3-beaked, glandular 

 and somewhat pilose-tomentose on the body, at least when young, 

 bearing about 20 or more mostly strongly flattened, often hook- 

 tipped spines 6. F. DELTOIDEA. 



4. Leaves green beneath or sometimes (in F. cordifolia) cinereous or canescent 



when young (7). 



7. Leaves sessile and cordate-clasping, coarsely spinous-toothed, ovate, 



reticulate; fruit fusiform or globose-fusiform, 10 to 23 mm. long, 



1- or 2-beaked, bearing very numerous hook-tipped spines, these 



4 to 6 mm. long 9. F. ilicifolia. 



