STANDLEY — TREES AND SHRUBS OF MEXICO. 725 



Flowers all or mostly in pedunculate umbels. 



Loaves covered beneath with a minute close white tomentum. 



1. B. tomentella. 

 Leaves green beneath, short-pilose, glabrate, or with a loose coarse tomentum. 



Leaves acuminate, long-petiolate 2. R. discolor. 



Leaves rounded or obtuse at apex or sometimes acute, short-petiolate. 

 Leaf blades broadly oval, less than twice as long as broad, densely vil- 



lous-tomentose beneath 3 R. palmeri. 



Leaf blades oblong to elliptic, short-pilose or glabrate beneath. 



4. B.. betulaefolia. 

 Flowers solitary in the axils or in sessile umbels. 



Leaves entire, glabrous. Petals none 5. R. brandegeana. 



Leaves serrulate or dentate or if (rarely) entire, copiously pubescent. 

 Fruit normally dicoccous ; leaves persistent, often pungent-dentate ; sepals 

 usually 4. 



Leaves linear-oblong, 3 mm. wide or less 6. R. stenophylla. 



Leaves elliptic-oblong to orbicular, 5 to 35 mm. wide. 



Leaves acute or acutish 7. R. serrata. 



Leaves rounded or very obtuse at apex. 

 ; Leaves orbicular to rounded-obovate, 7 to 35 mm. wide. 



8. R. ilicifolia. 



Leaves oval to elliptic-oblong, 5 to 8 mm. wide 9. R. microphylla. 



Fruit tricoccous ; leaves mostly deciduous, not pungent-dentate ; sepals 5. 

 Leaves rounded or very obtuse at apex. 



Leaves densely pilose, 1.5 to 3 era. wide 10. R. pringlei. 



Leaves nearly glabrous, less than 1 cm. wide 11. R. macrocarpa. 



Leaves acute or acuminate. 



Leaves elliptic, abruptly short-acuminate 12. R. capreaefolia. 



Leaves mostly oblong or ovate-oblong, acute or acuminate. 



13. R. m^ucronata. 



1. Rhamnus tomentella Benth. PI. Hartw. 303. 1848. 



Rhanmus califomica tomentella Brewer & Wats. Bot. Calif. 1 : 101. 1876. 



Northern Baja California. New Mexico to southern California. 



Large shrub with tomentulose branchlets; leaves oblong, 3.5 to 6 cm. long, 

 rounded to acute at apex, green on tlie upper surface and minutely puberulent, 

 the lateral nerves very prominent beneath, the margins revolute, subentire; 

 jlowers 5-parted, puberulent; fruit usually dicoccous. 



2. Rhamnus discolor (Donn. Smith) Rose, Contr. U. S. Nat. Herb. 5: 51. 1903. 

 Rhamnus capreaefolia discolor Dt)nn. Smith, Bot. Gaz. 20: 200. 1893. 

 Oaxaca. Guatemala to Costa Rica ; type from Coban, Guatemala. 



Small tree; leaves long-petiolate, deciduous, mostly elliptic or ovate-elliptic, 

 6 to 15 cm. long, pubescent beneath or finally glabrate, obscurely serrulate; 

 umbels densely pubescent, some of them sessile and some pedunculate; flowers 

 5-parted, green; fruit usually tricoccous. " Duraznillo " (Costa Rica). 



3. Rhanmus palmeri S. Wats. Proc. Amer. Acad. 22: 403. 1887. 



Known only from the vicinity of Tequila, Jalisco, the type locality. 



Shrub, 1 to 2 meters high, with tomentose branches ; leaves very short- 

 petiolate, 2 to 7 cm. long, broadly rounded at base and apex, coarsely or finely 

 serrate, densely pilose on the upper surface; umbels partly sessile and partly 

 pedunculate; fruit tricoccous. 



