84 University of California Publications in Botany. t v L - 3 



tricata Gray, Proc. Am. Acad. xvii. 208 (1882). Leucosyris car- 

 nosa Greene, Fl. Fr. 384 (1897) ; Pitt. iii. 243 (1897). 



A rigidly much branched shrub, 6 or 8 dm. high, with slender 

 pale branches and inconspicuous scale-like leaves: leaves linear 

 or subulate, entire, mostly .2 to 1 cm. long, the lower fleshy 

 ones sometimes 2 cm. long : heads solitary, terminating geniculate 

 or widely spreading branchlets : involucre 6 mm. high ; its lanceo- 

 late-acuminate imbricated bracts chartaceous, with a greenish 

 midrib : rays none : style-branches linear-subulate : achenes seri- 

 ceous-pubescent. 



Restricted chiefly to the Lower Sonoran Zone of the Mohave 

 Desert and Inyo Co., not common : alkaline meadow near Colton, 

 Parish, no. 2005; Rabbit Springs, Parish, no. 1453; alkaline 

 plains of Antelope Valley; etc. 



14. A spinosus Benth., PL Hartw. 20 (1839). Leucosyris 

 spinosa Greene, Pitt. iii. 244 (1897). MEXICAN DEVIL-WEED. 



Slender, reedy, 6 to 12 dm. high and herbaceous throughout 

 (12 to 25 dm. high and shrubby in the Mexican form), brancn- 

 ing above, the ascending branchlets terminated by solitary heads, 

 or ending in short racemes : herbage light green, glabrous : leaves 

 few, linear, mostly less than 2 cm. long (basal sometimes 5 cm.), 

 often with spines in or above their axils, only the upper subulate 

 scale-like ones present at time of flowering: involucral bracts 

 lanceolate, acute, sometimes minutely pubescent or ciliate, brown 

 or greenish, with a scarious or reddish border : rays white, drying 

 brown, 3 mm. long: style-branches triangular-subulate: achenes 

 glabrous. 



South San Diego, Chandler, no. 4013 ; Tia Juana Valley, San 

 Diego Co., Alderson, no. 971; Colorado Desert, Davy, no. 8016, 

 Schellenger, no. 3, etc. ; thence to Texas and Central America. 

 According to Mr. J. E. Roadhouse, this species gives promise of 

 becoming a very troublesome weed in Imperial Valley, Colorado 

 Pesert. He observes that the plants become 9 to 12 dm. high 

 the first season and that by the end of the second season they 

 have thrown out numerous rhizomes 2 m. or more long. The 

 style-branches in Guatemalan specimens have been described as 

 very short and obtuse. 13 In ours the tips are ovate or lanceolate 

 and acute. 



s Coulter, Bot. Gaz. xx. 46 (1895). 



