ILLUSTRATED STUDIES IN THE GENUS OPUNTIA — III 



BY DAVID GRIFFITHS. 



Studies in field and cultivated plantations during the past 

 five years have brought together sufficient data to warrant 

 the addition of the following species to the genus Opuntia. 



Opuntia alta sp. nov. 



A strictly arborescent species with distinct, short, cylindrical trunk, 

 3 to 3£ dm. in diameter and huge, spreading branches 1£ to 2 dm. in 

 diameter, early becoming bare, brown-gray and scaly-cracked, 2\ to 

 3£ meters high in large specimens, mostly lower than this and often 



wi 



form 



possibly more often 



green, 

 -green 



areoles obovate, about 3 to 5 mm. long and 3 cm. apart, slightly 

 raised, closer on edges where they are also larger, rendering a some- 

 what congested appearance to spines and spicules, enlarging with age 

 to sub-circular and often 1 cm. in diameter, tawny when young, be- 

 coming dirty black in age; spicules yellow, abundant, 8 mm. long, 

 mostly scattered throughout the entire areole but more numerous 

 above, increasing with age and filling and crowding the entire areole, 

 the tissues of which proliferate slightly into a raised hemispherical 

 structure, the outer spicules becoming dirty yellow and the central 

 newer ones a brighter color; spines yellow, typically, one 15 to 20 mm. 

 long, erect, and one 10 to 12 mm. long, and sloping down on sides of 

 joints and two or even 3 long ones on edges, not increasing with age 

 to any appreciable degree, at about 5 years of age and older the 

 trunks becoming comparatively bare of spines but covered with the 

 scattered, formidable, bunches of spicules only, slightly flattened and 

 the largest ones faintly annular; flowers yellow, with broadly-rounded, 

 wavy-margined, obovate petals, with abrupt cuspidate point, filaments 

 yellow, greenish at very base, style white, stigma yellowish tinged, 

 10 to 12-parted; ovary broadly obovate to conical, about 2 by 3 cm. 

 having small sub-circular areoles bearing spreading, unequal, yellow, 

 fugacious spicules about 5 mm. long. 



This species is distinctly arborescent in habit, one of the 

 tallest and largest of our United States forms. It is very 

 different indeed from Opuntia cacanapa, although one or 



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