191 1.] TRELEASE— THE DESERT GROUP XOLIXE.E. 439 



Shortly caulescent. Trunk scarcely i m. high. Leaves 15-20 

 or 25 mm. wide, scarcely i m. long, glaucous, nearly 

 smooth, dull: prickles 5-10 mm. apart, 2-3 mm. long, 

 yellow, becoming brown upwards. Inflorescence 3-5 

 m. high. Fruit round-obovate, 6-7 X 7-9 mm., the 

 style normally about equaling the open moderately deep notch. Seed 

 (immature) 3 mm. long. — PL /, 8, 11, 12. 



Southeastern Arizona and adjoining ^Mexico, Xew Mexico and 

 Texas. Region of Koliiia microcarpa and caiidata. 



Specimens examined: Arizona. Ash Creek, etc. (Rothrock, ^2p, 

 6jj, — the types). Rio Grande to Gila Rivers (Emory, 1846). Sun- 

 flower Valley (Girard, 1873). Dragoon Summit (Vasey, 1881). 

 Sta. Catalina ^Mountains {LcDimon, 1881 ; Pringle, 1881 ; Tourney, 

 1894). Without locality {Pringle, 1884). Sta. Rita ^Mountains 

 {Brandegee, 1891 ) . Ft. Huachuca ( Wilcox, 208, 264, 1894) . Chiri- 

 cahua Mountains (Touiney, 1894). San Carlos {Straiih, 1895). 

 Xogales {CoviUc, 162^, 1903; TJiompson, 1911). White Tail (Pils- 

 bry, 1906). Benson (Rose, Staiidley & Russell, 12^26, 1910). Xew 

 Mexico. Silver City (Greene, 1880; Metcalfe, dj/, 1903). Burro 

 Mountains (Rusby, 41J, 1881, — leaves). Pinal ^Mountains (Tourney, 

 449, 1892). Las Cruces (IVooton, J2, 1897). Mangos (Metcalfe, 

 1897). Kingston (Metcalfe, 1014, 1904). Alamogordo (Rehn & 

 Viereck, 1902). Organ Mountains (Standlcy, 1906). Texas. El 

 Paso (Evans, 1891). Tortugas Mountains (Rose, Standley & Rus- 

 sell, I22J4, 1910). Boundary Line (Parry ct al.). Chihuahua. 

 Lake Sta. Maria (Nelson, 6^93, 1899). 



Fruit triangular-obcordate : prickles moderate. 



D. Wheeleri Wislizeni Trelease. 



Shortly caulescent. Leaves 15-20 mm. wide, scarcely i m. long, 

 green or slightly glaucous, typically smooth and rather 

 glossy : prickles 5-10 mm. apart, 2-3 mm. long, red- 

 brown or with yellow base, the intervening denticles 

 often reddish. Inflorescence ample. Fruit triangular- "^ — 

 obcordate, 6-7 X 8-9 mm., the thick style about equaling the open 

 moderately deep notch. Seed (immature) 3 mm. long. — PI. 12. 



