FLOWERING PLANTS AXD FERNS OF ARIZONA 407 



loosely villous and the upper leaf surface and hypanthium substrigose 

 when young, then glabrate, seems to have been collected in Arizona 

 only in the Navajo Reservation (Vorhies 81, L. Whitehead in 1916). 

 The common form in the Grand Canyon region, occurring also on 

 Black Mesa (Apache and Navajo Counties), is var. mMosus C. K. 

 Schneider (C. arizonicus M. E. Jones), with young branches 

 villous-tomentose and the upper leaf surface and hypanthium pilose 

 with curly hairs, sometimes permanently so. The type of C. ari- 

 zonicus was collected at Willow Soring, Coconino Countv {Jones in 

 1890). 



3. Cercocarpus breviflorus A. Gray, PL Wright. 2: 54. 1853. 

 Southern Apache. Coconino, and Yavapai Counties to Cochise and 



Pima Counties, 5,500 to 8,000 feet, common in chaparral on dry 

 slopes and mesas, March to November. Western Texas to Arizona 

 and Mexico. 



A shrub, sometimes treelike and up to about 4.5 m. (15 feet) high. 

 The Arizona specimens all seem to belong to var. eximius C. K. 

 Schneider (C. eximius Rydb.) which, as compared with the typical 

 form, has more spreading pubescence, larger and more distinctly 

 dentate leaf blades, and usually a longer hypanthium and style. 



4. Cercocarpus betuloides Xutt. ex Torr. and Gray, Fl. Xorth Amer. 



1: 427. 1S40. 



Cercocarpus douglasii Rydb., North Amer. Fl. 22: 421. 1913. 



Apache County to Mohave County, south to Greenlee, Gila, Pinal, 

 Maricopa, and Cochise Counties, 3,000 to 6,500 feet, mostly in chapar- 

 ral, March to July. Arizona, Oregon, and California. 



Birchleaf mountain-mahogany. A large shrub or small tree, some- 

 times attaining a height of about 6 m. (20 feet). Probably the most 

 important of the Arizona species as a browse plant. Intergradations 

 with C. breviflorus occur. 



5. Cercocarpus montanus Raf., Atlant. Jour. 146. 1832. 



Grand Canvon, Coconino Countv (Thornber, Goldman), McMillen- 

 ville (Gila County), 4.500 to 6.800 feet. South Dakota and Montana 

 to Kansas, New Mexico, and Arizona. 



Alderleaf mountain-mahogany. The Arizona plants belong to var. 

 flabellijolius (Rydb.) Kearney and Peebles (C. flabettifolius Rydb.), 

 which apparently differs from the typical form only in the more 

 appressed pubescence of the leaves and hypanthium. 



17. COLEOGYXE. Blackbrush 



A small to rather large shrub with rigid spinescent branches and 

 strigose-pubescent herbage; leaves opposite, crowded, with narrowly 

 spatulate entire blades; flowers solitary; sepals 4, yellow; petals 

 usually none; stamens numerous; disk at base of the hypanthium 

 with a sheathlike prolongation enclosing the solitary pistil. 



1. Coleogyne ramosissima Torr., PI. Fremont. 8. 1853. 



Navajo County to Mohave County. 3.000 to 5.500 feet, well- 

 drained, usually gravelly soils of open plains and mesas, sometimes 

 in pure stands to the exclusion of other shrubs, March to May. 

 Colorado to northern Arizona and southeastern California. 



