ILLUSTRATED STUDIES IN THE GENUS OPUNTIA — II. 85 



On the other hand we have a most curious antithesis in 0. 

 echinocarpa. This reaches its maximum development of 6 or 

 7 feet high upon the deserts of Salt River Valley and its trib- 

 utaries, but decreases in stature as one ascends the mountains. 

 There is consequently the curious anomaly half-way up the 

 San Francisco highlands on the west and south sides, of two 

 dwarfed species of the same genus, one increasing in size 

 toward the summit and the other increasing in size toward 

 the valley. It is also equally strange that the dwarfed 

 condition of both plants is proportionately less productive of 

 seed than the normal larger forms. A few scattering plants 

 of 0. echinocarpa may be found as high as Fort Whipple, 

 nearly the limit of 0. Whipplei, but the latter never, so far as 

 I have seen, reaches the desert mesas of the Salt River or 

 Colorado valleys, where O. echinocarpa reaches its best devel^ 

 opment. — Plate 13, f. 11. 



Opuntia tricolor sp. nov. 



An erect to ascending, spreading, open branching species about 9 dm. 

 high, and 10 to 12 dm. in diameter; joints large, obovate, blue-green turn- 

 ing to a grayish brown and scaly upon old trunks, commonly 20 to 22 by 

 30 cm. in current year's growth, frequently only 17 or 18 by about 25 cm., 

 obovate and either broadly rounded above or obtusely pointed both above 

 and below; areoles subcircular, about 3 mm. in diameter on the sides, 

 commonly 4 mm. on edges in current year's growth, enlarging in ago to 

 6 or 7 mm., about 3 to 3.5 cm. apart; wool very light tawny; spicules 

 brown with yellow tips or brown throughout when young and always dull, 

 dirty yellow in age; spines bright yellow turning abruptly reddish-brown 

 to black at base, or when young some may be yellow throughout, erect, 

 diverging but slightly, 2 or 3 but 6 or more in age and still erect and only 

 slightly diverging, flattened, twisted, faintly annular, 5 to 7 cm. in length; 

 flowers yellow; fruit reddish-purple. 



The species is related to Opuntia Lindheimeri, from which 

 it differs in shape of joints, in color, length, position, and gen- 

 eral aspect of spines. It is a very striking species and so dis- 

 tinctly different from any of the described forms as to be very 

 clearly marked. The spines are much longer, yellower dis- 

 tally and darker at the base than any of the forms of the va- 

 riety cuija* with which it also has affinities. 



♦Bull. 60:44. pZ. 2, figs. 1 and 2. (1906.) Agricultural Experiment 

 Station of New Mexico. 



