50 



THE CACTACEAE. 



6. Opuntia arbuscula Engelmann, Proc. Amer. Acad. 3: 309. 1856. 

 Opuntia neoarbusciila Griffiths, Rep. Mo. Bot. Gard. 19: 260. 1908. 

 Forming a bush 2 to 3 meters high, often with a rounded, very compact top with numerous 

 short branches; trunk short, 10 to 12 cm. in diameter, with several woody branches; ultimate joints 

 5 to 7.5 cm. long, 8 mm. in diameter, with low, indistinct tubercles; leaves small; spines usually i, 

 but sometimes several, especially on old joints, porrect, up to 4 cm. long, covered with loose straw- 

 colored sheaths; flowers greenish 3'ellow tinged with red, 3.5 cm. long; fruit often proliferous, some- 

 times only one-seeded. 



^ M\X-i 



Fig. 60. — Opuntia arbuscula. 



Type locality: On the lower Gila near ISIaricopa village. 



Distribution: Arizona and Sonora. 



Opuntia congesta Griffiths (Rep. Mo. Bot. Gard. 20: 88, pi. 2, f. 4, 7; pi. 8; pi. 13, f. 5. 

 1909), from the description, is near this species and probably a race of it. 



Races of the species differ in size, in armament, in the length of the tubercles, and in 

 size and shape of the fruit. 



Illustrations: Ariz. Agr. Exp. Sta. Bull. 67 : pi. 6, f. 2; Bull. Torr. Club 32 : pi. 9, f. 3; 

 Plant World 11'^°: f. 11; Rep. Mo. Bot. Gard. 19: pi. 22; 19: pi. 23, in part, this last as 

 Opuntia neoarbuscula; Carnegie Inst. Wash. 269: pi. 11, f. 95. 



Plate vr, figure 5, represents a flowering branch from Professor J. W. Toumey's collec- 

 tion at Tucson, Arizona. Figure 60 is from a photograph taken by Dr. ISIacDougal near 

 Tucson, Arizona, in 1906; figure 61 is from a photograph taken by George B. Sudworth in 

 Santa Rita INIountains, Arizona; figure 62 shows a fruiting branch from the same collection. 



