992 MISC. PUBLICATION 423, U. S. DEPT. OF AGRICULTURE 



1. Heads smaller, the disk less than 1 cm. high, or (in D. acerosa) up to 1.5 cm (3). 

 3. Paleae of the pappus each dissected into 5 to 12 capillary bristles, the 

 alternate ones in D. acerosa dissected into only 3 bristles (4). 

 4. Leaves entire, linear-filiform, needlelike; plant perennial, the numerous 



stems or branches woody at base 3. D. acerosa. 



4. Leaves pinnately lobed, not needlelike; plants annual (5). 



5. Rays white, conspicuous; involucre essentially naked at base, the 

 phyllaries united three-fourths of their length or more, and with 



numerous small roundish glands 4. D. concinna. 



5. Rays yellow, small, inconspicuous; involucre subtended by several 

 mostly herbaceous bractlets of about its own length, the phyllaries 

 distinctly in 2 series and united only toward the base, their glands 



few, linear or elliptic, rather large 5. D. papposa. 



3. Paleae of the pappus tipped with only 1 to 3 bristles, or the outer paleae 

 without bristles (6) . 

 6. Outer paleae (as well as the inner ones) bristle- or awn-tipped. 



6. D. THURBERI. 



6. Outer paleae merely acute or obtuse, not awn-tipped (7) . 



7. Phyllaries of both the inner and the outer series (not the bractlets of the 

 caly cuius) united nearly to the apex; involucre puberulent all over. 



7. D. hartwegi. 

 7. Phyllaries of the outer series free-margined to below the middle of the 



involucre, the free margins densely short-ciliate; involucre other- 

 wise glabrous 8. D. pentachaeta. 



1. Dyssodia porophylloides A. Gray, Amer. Acad. Arts and Sci. Mem. 



ser. 2, 5: 322. 1854. 



Clomenocoma porophylloides Rydb., North Amer. Fl. 34: 166. 

 1915. 



Western Mohave and southern Yavapai Counties to Pinal, Pima, 

 and Yuma Counties, 4,000 feet or lower, washes, mesas, and dry rocky 

 slopes, March to October. Arizona, southern California, Sonora, and 

 Baja California. 



The plant has a strong, disagreeable odor. 



2. Dyssodia cooperi A. Gray, Amer. Acad. Arts and Sci. Proc. 9: 201. 



1874. 



Clomenocoma cooperi Rydb., North Amer. Fl. 34: 166. 1915. 

 Clomenocoma laciniata Rydb., ibid. 



Hackberry to the Colorado River (Mohave County), 3,500 feet 

 or lower, dry canyons, slopes, and mesas, April to August, type of 

 Clomenocoma laciniata from Hackberry (Jones in 1884). Western 

 Arizona, southern Nevada, and southeastern California. 



3. Dyssodia acerosa DC, Prodr. 5: 641. 1836. 



Aciphyllaea acerosa A. Gray, Amer. Acad. Arts and Sci. Mem. 

 ser. 2, 4: 91. 1849. 



Southern Coconino, Yavapai, Gila, Cochise, and Pima Counties, 

 3,500 to 6,000 feet, dry rocky slopes and mesas, April to October. 

 Texas to southern Nevada and Arizona, south to central Mexico. 



4. Dyssodia concinna (A. Gray) Robinson, Amer. Acad. Arts and Sci. 



Proc. 49: 507. 1913. 



Hymenatherum concinnum A. Gray, Syn. Fl. 1 2 : 446. 1884. 

 Boeberastrum concinnum Rydb., North Amer. Fl. 34: 162. 1915. 



Mesas near Tucson (Pringle in 1884, the type collection), 2,500 feet 

 or lower, May. Southern Arizona and Sonora. 



