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



16. Asclepias erosa Torr., U. S. and Mex. Bound. Bot. 162. 1859. 



Asclepias demissa Greene, Leaflets 2: 231. 1912. 



Mohave and Yuma Counties, 3,500 feet or lower, usually at road- 

 sides and in washes, September and October. Southern Utah and 

 western Arizona to southeastern California and northwestern Mexico. 



Desert milkweed. The stems grow in clumps, reaching a height of 

 1.8 m. (6 feet). This is one of the most promising sources of rubber 

 among plants native in the United States. A. demissa, based on an 

 Arizona type, appears to be merely an extremely depauperate form. 



17. Asclepias nummularia Torr., U. S. and Mex. Bound. Bot. 163. 



1859. 

 Cochise, Santa Cruz, and Pima Counties, 3,000 to 5,000 feet, dry 

 mesas and slopes, March to June. Western Texas to southern 

 Arizona. 



18. Asclepias cryptoceras S. Wats, in King, Geol. Expl. 40th Par. 5: 



283. 1871. 

 Near Pipe Springs, Mohave County, 5,000 feet (Peebles and Parker 

 14705). Utah to Oregon, northwestern Arizona, and California. 



19. Asclepias lemmoni A. Gray, Amer. Acad. Arts and Sci. Proc. 19: 



85. 1883. 



Mountains of Cochise and Pima Counties, 4,000 to 6,000 feet, 

 mostly in open pine woods, July and August, type from the Chiricahua 

 or the Huachuca Mountains (Lemmon in 1881). Known only from 

 southern Arizona. 



One of the largest leaved of the Arizona species, with pale-pink 

 hoods. 



20. Asclepias elata Benth., PL Hartw. 290. 1848. 



Graham, Gila, Cochise, Santa Cruz, and Pima Counties, 4,000 to 

 6,000 feet, openings in pine forests, etc., August and September. New 

 Mexico, Arizona, and Mexico. 



Flowers greenish yellow, faintly fragrant. A. elata is doubtfully 

 distinct from A. glaucescens H. B. K. 



21. Asclepias latifolia (Torr.) Raf., Atlant. Jour. 146. 1832-33. 



Asclepias obtusijolia Michx. var. latifolia Torr., Ann. Lye. 

 N. Y. 2: 217. 1828. 



Apache County to Coconino and Yavapai Counties, 5,000 to 7,000 

 feet, plains and mesas, often abundant along roadsides, June to 

 August. Nebraska to Utah, Texas, and Arizona. 



5. ASCLEPIODORA. Antelope-horns 



Stems usually decumbent, leafy; leaves thickish, lanceolate to 

 linear ; flowers many, large, in a terminal umbel, like those of Asclepias 

 except as stated in the key to genera. 



1. Asclepiodora decumbens (Nutt.) A. Gray, Amer. Acad. Arts and 

 Sci. Proc. 12: 66. 1876. 



Anantherix decumbens Nutt., Amer. Phil. Soc. Trans, ser. 2, 5: 

 201. 1837. 



Almost throughout the State, 4,000 to 7,500 feet, common on dry 

 plains and slopes, sometimes in openings in pine forests, April to 



