ILLUSTRATED STUDIES IN THE GENUS OPUNTIA. 



261 



The description is a compilation of two — one made in the 

 field where the species was first collected; and the other from 

 living, mature; cultivated plants. The name is coined to 

 designate a relationship to 0. arbuscula Engelm. 



The type is a specimen prepared from the cultivated plant 

 and numbered 9219 D. G., April 22, 1908, The plant was 



nnVinnllv mllpntnd in thn foothills of the Santa Rita Moun- 



Arizona 



Plate 



Opuntia castillae sp- nov. 



An erect, compactly branched plant, 18 to 30 dm. higli, with a strong, 

 scaly, black trunk 3 or 4 dm. in diameter; young growth deep dark green, 

 turning slightly glaucous, then scaly brown, and finally black; joints 

 broadly obovate, commonly 21 by 28 cm., thick; arcoles eUiptical to 

 obovate, about 6 mm. in longest diameter, enlarging to subcircular on old 

 joints or in vicinity of the articulation becoming transversely elongated, 

 or linear, deep purplish brown when young but soon becoming black; 

 leaves dark glossy green, circular in section, subulate, with reddish apex, 

 ending in a white or gray, delicate, recurved apiculus; spicules yellow, 

 seldom visible on the joints; spines white, translucent bonelike when young 

 but soon turning to a mottled, dirty gray, 1 to 5 on last yearns joints, more 

 commonly 1 to 2, but central, unless alone, more erect than others, when 

 two or more, one or more tightly recurved, more or less flattened or tri- 



gul 



sometimes crooked-wavey, 15 to 22 



mm. long, increasing in both length and numbers for several years; flowers 

 yellow, tinged w^ith red, 8 to 9 cm. in diameter; petals broadly obovate, 

 roxmded, retuse-notched at apex and minutely and irregularly toothed on 

 margin, yellow with tinge of red on outside in lower portion of midrib; 



triangul 



bel 



pistil 2.5 to 3 cm. long; style brilliant red; stigma light green with tinge of 

 red in outer folds as well as in the throat, 8-to 12-parted; ovary broadly 

 obovate or subglobose with subcircular arcoles about 2 mm. in diameter 

 and 5 mm. apart, deep dark brown with sometimes a tinge of purple, beset 

 with dark brown spicules and a few dark brown short (G mm.) dchcate, 

 straight or contorted fugacious hairlike spines, deeply pitted at apex; 

 fruit large, yellowish, toothsome. 



b 



Mexico. In general habit and 



0. 



streptacantJia about as closely as any, but it is much less spiny 

 and the spines are not so stiff and rigid. The joints also are 

 somewhat longer and the fruit is entirely different. 

 The description is drawn from the cultivated plant which 



