550 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



Scarlet sumac. In the fall the leaves turn bright red, giving a 

 brilliant touch of color to the forest. The acidulous fruits are official 

 in the United States Pharmacopoeia, having astringent and refrigerant 

 properties. Greene published also R. albida, R. elegantula, and R. 

 calophylla,] based upon Arizona types, but these appear to be mere 

 forms of R. glabra. 



6. Rhus choriophylla Woot. and Standi., Contrib. U. S. Natl. Herba- 



rium 16: 146. 1913. 



Cochise, Santa Cruz, and Pima Counties, 4,000 to 6,000 feet, rocky 

 slopes (often limestone), sometimes growing with Cupressus arizonica 

 and Juniperus pachyphloea, August to September. Southern New 

 Mexico, southeastern Arizona, and Sonora. 



Very close to R. virens Lindh., differing chiefly in the usually larger, 

 glabrate leaflets and in the more frequent occurrence of axillary in- 

 florescences. This shrub attains a height of about 2 m. (7 feet). 



7. Rhus microphylla Engelm. in A. Gray, PL Wright. 1: 31. 1852. 



Rhoeidium microphyllum Greene, Leaflets 1: 143. 1905. 



Greenlee, Cochise, and eastern Pima Counties, 4,000 to 6,000 feet, 

 dry mesas and slopes, March and April. Western Texas to south- 

 eastern Arizona and northern Mexico. 



A much -branched shrub, up to 1.8 m. (6 feet) high. 



68. CELASTRACEAE. Bittersweet family 



Plants of diverse habit, more or less woody; leaves simple, alternate 

 or opposite, sometimes reduced to scales; flowers small, regular, 

 usually perfect; calyx lobes and petals 4 to 6; stamens as many or 

 twice as many as the petals, inserted on or below the margin of a 

 basal disk, this rudimentary or wanting in Canotia. 



Key to the genera 



1. Leaves reduced to small deciduous scales; seeds with a thin terminal wing; 



plant a large shrub or small tree 4. Canotia. 



1. Leaves with well-developed blades; seeds without a terminal wing (2). 



2. Plant a creeping undershrub; leaves mostly opposite; flowers reddish brown. 



1. Pachystima. 

 2. Plants intricately branched shrubs; leaves alternate; petals whitish (3). 

 3. Herbage scabrous, yellowish; leaves persistent, the blades very thick, 

 with cartilaginous margins, elliptic to nearly orbicular; flowers in 

 panicles, these mostly terminal; stamens commonly 5; capsules sym- 

 metric, short-cylindric, rounded and abruptly apiculate at apex. 



2. Mortonia. 

 3. Herbage not scabrous, glabrous or puberulent, pale green, somewhat 

 glaucous; leaves deciduous, the blades not very thick, elliptic or 

 oblanceolate ; flowers axillary, scattered along the branchlets, often 

 solitary; stamens often more than 5; capsules asymmetric, ovoid, 

 pointed at apex 3. Forsellesia. 



1. PACHYSTIMA Boxleaf 



Undershrub with creeping stems, glabrous or nearly so; leaves 

 mostly opposite, thickish, evergreen, somewhat shiny above, the 

 margins serrate or serrulate; flowers minute, axillary, solitary or in 

 very few-flowered clusters; fruit a 2-celled, finally dehiscent capsule. 



The name of the genus is often spelled Pachistima. 



