A NEW OPUNTIA FROM ARIZONA 



By J. N. ROSE 



(With One Plate) 



While going from Tucson, Arizona, to the Pictured Rock some 12 

 miles to the southwest, my attention was called by Dr. D. T. Mac- 

 Dougal to a peculiar Opuntia resembling the very common 0. versi- 

 color, but of very different habit, branching and with larger fruit, 

 etc. At first we came upon a large group of these plants where 

 they formed the dominant element in the landscape. Farther on 

 the species was less common and was associated with 0. versicolor 

 and 0. spinosior, but it surely does not intergrade with either of 

 them. It is much more open in its manner of growth than 0. versi- 

 color, while the branches readily drop off and take root about the 

 old plant. This is shown very well in the accompanying illustration. 



This species may be technically described as follows : 



OPUNTIA VIVIPARA Rose, sp. nov. 



Stems 2 to 3.5 meters high, usually several from the base, 8 to 

 10 cm. in diameter, much branched, but not compactly so ; old 

 stems with rather smooth bark; young branches bluish green, slen- 

 der, I to 2 cm. long, 10 to 12 mm. in diameter; tubercles low, ob- 

 long, 15 to 20 mm. long; areoles when young forming a dense cush- 

 ion of yellow wool with few or no glochides; spines i to 4, 2 cm. 

 or less long, covered with straw-colored sheaths ; leaves small, terete, 

 acutish, purple; flowers numerous, borne in clusters at the top of 

 last year's branches, purplish; ovary strongly tubercled, bearing- 

 white deciduous bristles ; fruit oblong, 4 to 6 cm. long, smooth with 

 a somewhat depressed umbilicus, yellowish-green, spineless ; seeds 

 white, 5 mm. long. 



On a mesa near Tucson, Arizona, to the southwestward, J. N. 

 Rose, April 21, 1908 (No. 11836). 



Type in U. S. National Herbarium, No. 454,531. 



Illustration (PI. xii) furnished by courtesy of the Carnegie Insti- 

 tution of Washington. 



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