FLOWERING PLANTS AND FERNS OF ARIZONA 465 



30. PETERIA 



Plants herbaceous, perennial; stems low, slender, rather stiff; leaves 

 pinnate, the leaflets many, small, the stipules spiny; flowers in long- 

 stalked loose racemes, the banner recurved, the keel incurved; pods 

 narrow, several-seeded. 



The tuberous rootstocks of P. scoparia, known in Texas as camote- 

 de-monte, are reported to be edible. 



Key to the species 



1. Leaflets not more than 2 mm. wide, acute or acutish at apex, soon deciduous; 

 stem freely branched above the base; calyx strigose, only slightly glandular- 

 puberulent, the teeth deltoid, 2 to 4 mm. long; corolla 12 to 16 mm. long. 



1. P. SCOPARIA. 



1. Leaflets 4 mm. wide or wider, obtuse, rounded, or slightly retuse and often 

 mucronate at apex; stem simple or very sparingly branched above the base; 

 calyx more or less hirsute, copiously glandular-pubescent, the teeth 5 mm. 

 long or longer; corolla 16 to 25 mm. long 2. P. thompsonae. 



1. Peteria scoparia A. Gray, PL Wright. 1: 50. 1852. 



Petrified Forest, Apache County (Toole and Goodding in 1936), July 

 to August. Western Texas to northeastern Arizona. 



2. Peteria thompsonae S. Wats., Amer. Nat. 7: 300. 1873. 

 Northern Coconino County, near the Utah State line (Kelly in 1932, 



Cottam et al. 4199), 4,000 feet, sometimes with Coleogyne. Southern 

 Utah and northern Arizona. 



31. ROBIXIA. Locust 



Large shrubs or small trees, thorny; leaves odd-pinnate, the leaflets 

 numerous, rather large; flowers many in rather dense racemes, large 

 and showy, fragrant, the corolla purplish pink; pedicels glandular; 

 stamens diadelphous, 9 of them with the filaments united below into 

 a tube ; pods flat, 2-valved, several-seeded, hispid and usually glandular. 



1. Robinia neomexicana A. Gray, Amer. Acad. Arts, and Sci. Mem. 

 ser. 2, 5: 314. 1855. 



Coconino County, and Hualpai Mountain (Mohave County), south 

 to Cochise and Pima Counties, 4,000 to 8,500 feet, common and often 

 abundant, mostly in canyons and in coniferous forests, often with 

 Quercus gambelii, May to July. Southern Colorado to southern 

 Nevada, western Texas, New Mexico, Arizona, and northern Mexico. 



New Mexican locust. The plant reaches a height of 7.5 m. (25 feet) 

 and being very handsome in flower is sometimes cultivated as an 

 ornamental. The flowers are relished by cattle and the foliage is 

 browsed, both by cattle and deer. The Hopi Indians are reported to 

 use the plant as an emetic and in treating rheumatism. The habit of 

 forming thickets and of sprouting freely from stumps and roots makes 

 this plant valuable for control of erosion. 



Two forms of this species are common in Arizona, var. luxurians 

 Dieck (R. luxurians Rydb.) and var. subvelutina (Rydb.) Kearney 

 and Peebles (R. subvelutina Rydb.). Both are supposed to be distin- 

 guished from typical R. neomexicana by the presence of gland-tipped 

 hairs on the pods. In var. luxurians the pubescence of the herbage 4 





