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



ously radiate, yellow, in dense rounded terminal clusters, these 

 panicled; involucre graduated, the phyllaries chartaceous, with short 

 green tips; achenes glabrous, 4- or 5-ribbed; pappus none. 



1. Selloa glutinosa Spreng., Nov. Provent. Hort. Hal. 36. 1819. 



Gymnosperma glutinosum hess., Syn. Gen. Compos. 194. 1832. 

 Gymnosperma corymbosum DC, Prodr. 5: 312. 1836. 



Maricopa, Pinal, Cochise, Pima, and Yuma Counties, 2,000 to 6,000 

 feet, rocky canyons and slopes, August to October. Texas to southern 

 Arizona, south to Central America. 



The plant is used in Mexico in decoctions for treating diarrhea, 

 and the gum is used externaUy in cases of rheumatism and ulcers. 



9. XANTHOCEPHALUM 



Annual herbs, nearly or quite glabrous, sometimes glutinous; 

 leaves alternate, linear to lance-oblong; heads radiate, yellow, cymose- 

 panicled or scattered; involucre broad, the phyllaries graduated, 

 chartaceous, green-tipped; pappus of several unequal more or less 

 united awns, or reduced to a setulose crown, sometimes none in the 

 ray achenes. 



Key to the species 



1. Leaves chiefly lanceolate, 5 to 20 mm. wide; heads crowded in cymose panicles, 

 the pedicels stipitate-glandular; rays 12 to 19; pappus in the ray achenes 

 none or reduced to an obscure border, in the disk achenes of unequal, 

 basally united squamellae or paleae 1. X. gymnospermoides. 



1. Leaves chiefly linear, 2 to 4 mm. wide; heads mostly solitary at the tips of 

 cymose] y arranged glabrous branches; rays about 30 to 50; pappus a 

 short undulate crown 2. X. wrightii. 



1. Xanthocephalum gymnospermoides (A. Gray) Benth. and Hook. 



ex Rothr. in Wheeler, U. S. Survey West 100th Merid. Rpt. 6: 

 140. 1878. 



Gutierrezia (?) gymnospermoides A. Gray, PI. Wright. 2: 79. 

 1853. 



Pinal, Cochise, Santa Cruz, and Pima Counties, 1,200 to 5,500 

 feet, locally abundant in alluvial, often saline soil, August to October. 

 Southeastern Arizona to northern Mexico. 



The plant attains a height of 6 feet or more. 



2. Xanthocephalum wrightii A. Gray, Amer. Acad. Arts and Sci. 



Proc. 8: 632. 1873. 



Gutierrezia wrightii A. Gray, PL Wright. 2: 78. 1853. 



White Mountains (Apache County) to the mountains of Cochise, 

 Santa Cruz, and Pima Counties, 5,000 to 8,500 feet, openings in pine 

 forest, August to October. New Mexico and Arizona. 



10. GRINDELIA. 61 Gumweed 



Herbs, more or less resinous-viscid; leaves alternate, entire, toothed, 

 or rarely pinnatifid ; heads medium-sized, yellow, radiate or discoid; 

 involucre strongly graduated; achenes short, more or less thickened; 

 pappus of 2 to 8 slender caducous paleaceous awns. 



61 Reference: Steyermark, J. A. studies in grindelia. n. a monograph of the north American 

 species of the genus grindelia. Mo. Bot. Gard. Ann. 21: 433-608. 1934. 



