ILLUSTRATED STUDIES IN THE GENUS OPUNTIA — II. 93 



eight feet high, which applies much better to Opuntia Lind- 

 hdmeri than to this species. Again, the spines of Opuntia 

 Ldndheimeri, under many conditions, might be considered 

 yellow rather than white. However, should the translucent, 

 bone-like appearance of the spines of some forms of 0. Lind- 

 heimeri be called yellow, they are very different indeed from 

 the yellow of the species here described. 



The type is No. 9640 D. G., collected at San Antonio, Texas, 

 October 1, 1908. The description is a compilation of one 

 made when the type specimen was collected and previous field 

 notes, together with laboratory examinations of fresh hving 

 material. — Plates 9; 13, f. 1. 



Opuntia arizonica sp. nov. 



A prostrate to ascending species, 8 to 10 dm. high and often widely- 

 spreading, sometimes 2.5 m. in diameter but usually about 18 dm., the 

 joints of the main branches mostly on edge and radiating outward but 

 often flattened upon the ground; joints large, subcircular, commonly 2.7 

 dm, in diameter but mostly about 22 cm., glaucous, blue-green but becom- 

 ing yellowish green with age; areoles tawny, turning gray-black, large, 

 obovate, about 8 mm. in longest diameter on sides of joints but on edges 

 some, at least, are subcircular and often 10 to 13 mm. in diameter, not en- 

 larging much with age but finally becoming black, and central tissue proli- 

 ferating irregularly into a low cone; spicules reddish-brown, with abrupt 

 yellow tips, becoming lighter with age, somewhat mottled brown and yel- 

 low, about 6 to 10 mm. long, unequal, scattered, but more abundant in 

 upper portion of areole, increasing with age from central proliferating 

 areolar tissue, sometimes becoming 12 or 13 mm. long, sometimes flat- 

 tened and twisted; spines large, stout, formidable, reddish-brown through- 

 out, soon bleaching distally, becoming irregularly mottled, reddish-brown 

 and flesh-colored, then yellow with reddish bases, or yellow throughout, 

 and finally on very old joints dirty gray, flattened, twisted, faintly annular 

 in color but not in structure, 2 to 6, mostly 3 or 4, erect, divergent, but 

 the lower ones usually recurved, and all having a tendency to slope down- 

 ward in age, the longest 4 to 5 cm. in length; flowers not seen; fruit large, 

 subglobose, somewhat tubercular, pitted at apex, reddish-purple with 

 greenish rind which has some red in its vascular system and pulp mottled, 

 its areoles large, subcircular to obovate, about 4 mm. in diameter, tawny 

 to light gray, bearing spicules about 3 mm. long, and in upper areoles 1 

 or 2, delicate, fugacious, mottled yellow and brown spines 12 to 25 mm. 

 in length; seeds flattened, angular, quite uniform in size but somewhat ir- 

 regular in shape, with marginal callus, rather prominent and 1 mm. wide, 

 with distinct deeply notched hilum, about 4 mm. in diameter. 



