OPUNTIA. 



145 



back from the Southwest by W. H. Emory. They can never be critically identified, but 

 are probably of this relationship. 



Illustrations: Engler and Prantl, Pflanzenfam. 3 6a : f. 57, C; Forster, Handb. Cact. ed. 

 2. f. 141 ; Illustr. Fl. 2 : f . 2530; ed. 2. 2: f. 2989; Pac. R. Rep. 4: pi. 9, f. i to 5; pi. 22, f. 

 12 to 15; Wiener Illustr. Gartenz. 10: f. 115, all as Opuntia caiihiucliica; N. Mex. Agr. Exp. 

 Sta. Bull. 78: pi. [7], as Opuntia chihuahuensis; Contr. U. S. 

 Nat. Herb. 12 : pi. 55, as Opuntia blakeana; Cact. Mex. Bound, 

 pi. 75, f. 9 to 13. 



Plate xxv, figure 2, represents a flowering joint of a 

 plant sent from Tucson, Arizona, in 1916, by Dr. Mac- 

 Dougal. 



146. Opuntia mojavensis Engelmann, Proc. Amer. Acad. 3: 293. 

 1856. 



Prostrate, with suborbicular joints; pulvini remote, with large 

 yellow bristles; spines 2 to 6, stout and annulate, acutely angu- 

 lar and compressed, more or less curved, reddish brown, paler 

 toward tip, 2.5 to 6 cm. long, i to 3 smaller, slenderer, pale ones 

 added below; fruit oblong, 4.5 cm. long. 



of the Colorado, 



FIG. 183. Opuntia covillei. Xo-4- 



Type locality: On the Mojave, west 

 California. 



Distribution: Known only 

 from the type locality. 



The fragmentary type speci- 

 men has been examined ; we have 

 been unable to refer any other 

 specimens to this species, which 

 is thus very imperfectly under- 

 stood. 



Illustration: Pac. R. Rep. 4: 

 pi. 9, f. 6 to 8. 



147. Opuntia covillei Britton and 

 Rose, Smiths. Misc. Coll. 50: 

 532. 1908. 



Opunlia megacarpa Griffiths. 



Rep. Mo. Bot. Card. 20: 



91. 1909. 

 Opuntia ntgosa Griffiths, Proc. 



Biol. Soc. Washington 27: 



27. 1914. 



Bushy plants, usually growing 

 in dense thickets; joints orbicular to 

 obovate, 10 to 20 cm. long or more, 

 pale green, sometimes purplish, 

 slightly glaucous ; areoles 2 to 4 cm. 

 apart; spines several from an areole, 

 slender, unequal, the longest ones 

 6 cm. long, white when young, 

 brownish when old; flowers large, 

 yellow. 



Type locality: San Bernard- 

 ino, California. 



Distribution: Interior valleys 

 of southern California. 



Opuntia covillei and O. vaseyi grow in the same valleys, often in adjoining colonies, 

 and while hybrids may occur, the two species could easily be distinguished. When growing 



^- - 



FIG 184. Opuntia covillei. 



