948 MISC. PUBLICATION" 42 3, U. S. DEPT. OF AGRICULTURE 



5,000 feet, usually in sandy soil, often in washes, locally abundant, 

 April and May. Southern Utah to southeastern California and 

 south-central Arizona. 



Woolly bur-sage. Plant up to 1 m. high, with rigid spreading 

 branches. 



6. Franseria deltoidea Torr., PL Fremont. 15. 1853. 



Maricopa, Pinal, and Pima Counties, 1,000 to 2,800 feet, very 

 abundant on plains and mesas, often in nearly pure stands, December 

 to April, type collected by Fremont on the Gila River. South- 

 central Arizona and Sonora. 



7. Franseria cordifolia A. Gray, Syn. Fl. I 2 : 445. 1884. 



Horse Mesa Dam (eastern Maricopa County), Santa Catalina? 

 Tucson, and Ajo Mountains (Pima County), 1,700 to 3,100 feet, 

 locally abundant, canyons, rocky slopes, and washes, March and 

 April, type from mountains near Tucson (Pringle). Southern Ari- 

 zona and northern Mexico. 



8. Franseria ambrosioides Cav., Icon. PL 2: 79. 1793. 

 Southern Yavapai County to Pinal, Pima, and Yuma Counties, 



up to 3,100 feet, common in sandy washes and canyons, March to 

 May. Southern Arizona and northern Mexico. 



9. Franseria ilicifolia A. Gray, Amer. Acad. Arts and Sci. Proc. 11: 



77. 1876. 



Desert mountain ranges of southern Yuma Coimty, 1,000 feet or 

 lower, usually in sand, March and April. Southwestern Arizona, 

 southeastern California, and northern Baja California. 



Hollyleaf bur-sage. A roundish, densely much-branched evergreen 

 subshrub, the leaves spinescent. 



51. XANTHIUM. ™ Cocklebur 



Monoecious weedy annuals; leaves alternate, sometimes with triple 

 spines in the axils; hermaphrodite (staminate) heads clustered, borne 

 above the pistillate ones, their involucres with free phyllaries; pistil- 

 late involucre burlike, 2-celled, 2-beaked, covered with stiff hooked 

 prickles. 



These are troublesome weeds in pastures and cultivated fields. 

 The spiny burs clot the manes and tails of horses, and occasionally 

 cause death of young animals by irritating or clogging the intestinal 

 tract. The seeds and seedlings contain a glucoside, xanthostrumarin, 

 which is poisonous to livestock, especially to swine and poultry. 

 Some of the species yield an extract which is stated to have styptic 

 properties. 



Key to the species 



1. Leaves lanceolate or lance-ovate, acute or acuminate at both ends, densely 

 whitish-strigillose beneath; axils of the leaves bearing conspicuous 

 3-forked spines; fruit about 1 cm. long 1. X. spinosum. 



1. Leaves deltoid or broadly ovate, usually cordate, green beneath; axils without 

 spines; fruit about 2 cm. long or more 2. X. saccharatum. 



" 2 References: Millspaugh, C. P., and Sherff, E. E. revision of the north American species of 

 xanthium. Field Mus. Nat. Hist. Bot. Ser. 4: 9-49. 1919. 



WlDDER, F. J. DIE ARTEN DER GATTUNG XANTHIUM. BEITRAEGE ZU EINER MONO- 



graphie. Kepert. Spec. Novarum Regni Veg. Beih. 20: 1-221. 1923. 



