FLOWERING PLANTS AND FERNS OF ARIZONA 595 



Key to the species 



1. Stems not more than 3 cm. in diameter, densely puberulent; spines less than 

 10 mm. long; flowers salverform, white; plant rarely 2 m. high; root tuber- 

 ous; fruit red (2). 

 2. Branches 1.5 to 3 cm. thick, strongly angled with 3 to 6 prominent rib-; 

 root large, carrot-shaped; flowers 12 to 20 cm. long; fruit 12 to 15 cm. 

 long; seeds 3.5 mm. long, tessellate and rugose, dull 1. C. greggii. 



2. Branches 5 to 8 mm. thick, not angled, deeply striate; ribs 6 to 9, low, broad, 



flattened; roots clustered; flowers 7 to 15 cm. long 2. C. diguetii. 



1. Steins very stout, glabrous; spines more than 10 mm. long; flowers funnelform; 

 plant arborescent, 4 to 17 m. high; roots not tuberous (3). 



3. Plant with a massive stem more than 30 cm. thick, this usually continuous, 



often unbranched but usually bearing smaller variously curved lateral 

 branches; ribs 12 to 24, 5 to 10 cm. apart; flowers white, 10 to 12 cm. 

 long, borne in crownlike clusters at the ends of branches; fruit ovoid, 6 

 to 9 cm. long, naked or sparsely spiny; seeds tessellate. 



3. C. GIGAXTEUS. 



3. Plant with several to many stems, these of approximately equal size, less 



than 20 cm. thick, mainly produced from base of the plant; flowers 



pink (4). 



4. Spines similar all along the stem; ribs 12 to 17, 2 to 4 cm. apart; flowers 6 



to 7.5 cm. long; fruit globose, 5 to 7.5 cm. in diameter, densely spiny; 



seeds tessellate or reticulate and obscurely pitted. _ 4. C. thtjrberi. 



4. Spines twisted and conspicuously longer on the upper (floriferous) part of 



the stem; ribs 5 to 7 in number, 6 to 10 cm. apart; flowers 3 to 4 cm. 



long, often 2 or more at an areole; fruit globose, 2 to 3 cm. in diameter, 



unarmed; seeds tessellate, at least toward the base. _ 5. C. schottii. 



1. Cereus greggii Engelm. in Wisliz., Mem. North. Mex. 102. 1848. 



Peniocereus greggii Britt. and Rose, Contrib. U. S. Natl. 

 Herbarium 12: 428. 1909. 



Southern Mohave County to Graham, Cochise, Pima, and Yuma 

 Counties, commonly at low altitudes with Larrea, June and July. 

 Western Texas, southern New Mexico, Arizona, and northern Mexico. 



Nightblooming cereus, reina-de-la-noche. The beautiful, white, 

 heavily fragrant flowers last only 1 night. The root sometimes is 

 enormous but ordinarily weighs from 5 to 15 pounds. It is reported 

 that the Indians formerly utilized the root for food. 



*2. Cereus diguetii Weber, Paris Mus. Hist, Nat. Bui. 1: 319. 1895. 

 A living specimen was collected in 1939 by J. Whitman Evans in 

 the vicinity of Sonoita, Sonora, a few miles south of the international 

 boundary. According to Evans the flowers are nocturnal and white, 

 as described for C. diguetii, a species regarded by Britt. and Rose as 

 synonymous with C. striatus T. S. Brandeg. (WUcoxia striata Brill . 

 and Rose). Flowers of the latter are believed to be diurnal and purple. 

 A. A. Nichol has observed plants very similar to Evans' specimen 

 in western Pima County along the Mexican boundary. 



3. Cereus giganteus Engelm. in Emory, Mil. Reconn. 159. 1848. 



Carnegiea gigantea Britt. and Rose, N. Y. Bot, Gard. Jour. 9: 

 188. 1908. 



Yavapai and Mohave Counties to Graham, Pima, and Yuma Coun- 

 ties, up to 3,500 or exceptionally 4,500 feet, warm situations in well- 

 drained soil, common, flowering May and June, type from along the 

 Gila River, southern Arizona. Arizona, Sonora, and very locally 

 in southeastern California. 



Sahuaro, saguaro, giant cactus. Designated Arizona's Stale 

 flower, this massive succulent is the largest cactus in the Stale, 



