FLOWERING PLANTS AND FERNS OF ARIZONA 613 



17. Opuntia phaeacantha Engelm. in A. Grav, Amer. Acad. Arts and 



Sci. Mem. ser. 2, 4:^52. 1849. 



Opuntia tortispina Engelm. and Bigel. in Engelm., Amer. 

 Acad. Arts and Sci. Proc. 3: 293. 1856. 



Throughout most of the State, 1,200 to 7,500 feet, common, April 

 to June. Colorado, Utah, and Arizona to Texas and northern Mexico. 



0. procumbens Engelm. and Bigel. and 0. angustata Engelm. and 

 Bigel., both known only from Arizona, probably are merely infrequent 

 variants of 0. phaeacantha. The twisted spines ascribed to 0. torti- 

 spina Engelm. and Bigel. are not of diagnostic importance. The 

 writers assume that Boissevain and Davidson (see footnote 89, p. 607 I 

 are correct in referring to 0. rafinesquei Engelm., the plant regarded 

 by Britton and Rose as 0. tortispina. 



The writers have seen no local material of O. tenuispina Engelm., although 

 the species is reported from Arizona. Specimens from southern New Mexico, 

 supplied by A. R. Leding, do not appear to be very closely related to O. phaea- 

 cantha. The joints are rather small, exceedingly spiny, and transversely wrinkled, 

 and the fruits are not more than 3 cm. long. 



18. Opuntia engelmannii Salm-Dvck ex Engelm., Boston Jour. Nat. 



Hist. 6: 207. 1850. 



Opuntia discata Griffiths, Mo. Bot. Gard. Ann. Rpt. 19: 266. 



1908. 

 9 Opuntia Canada Griffiths, ibid. 20: 90. 1909. 



Throughout the southern part of the State, common or abundant, 

 1,000 to 6.500 feet or somewhat higher, April to June. Texas to 

 Arizona, and Mexico. 



In Arizona the plants are somewhat variable but usually recog- 

 nizable, 0.5 to 1 .5 m. high, the joints obovate, 20 to 35 cm. long. A 

 very robust form, often mistaken for the form described by Griffiths 

 as 0. discata but apparently undeseribed, is common in the south- 

 eastern counties. The plant is often 2 m. high and 3 m. in diameter. 

 The joints are orbicular or slightly rhombic, 30 to 45 cm. long. The 

 type plants of 0. discata and 0. Canada were found in Pima. County. 

 0. engelmannii has become a pest on some cattle ranges but has 

 potential value as feed in times of drought. 



*19. Opuntia pulchella Engelm., Acad. Sci. St. Louis Trans. 2: 201. 

 1863. 



Corynopuntia pulchella Knuth in Back, and Knuth, Kaktus- 

 ABC 115. 1935. 



Reported from Arizona and to be looked for hi northern Mohave 

 County. Nevada. 



20. Opuntia parishii Orcutt, West Amer. Sci. 10: 81. 1896. 



Corynopuntia p>arishii Knuth in Back, and Knuth, Kaktus- 

 ABC 115. 1935. 



Thirty -five miles north of Hackberry, Mohave County (Evans in 

 1935). Nevada, Arizona, and southern California. 



Opuntia clavata Engelm. is reported from Apache and Navajo Counties. White 

 spines distinguish this New Mexican species from O. parishii. 



