ECHINOCEREUS. 
27 
visor, Mr. Frank Rush, to have living plants sent on to Washington. These arrived in 
November. Besides several single plants there was a large clump, 3 dm. in diameter, 
consisting of 25 branches. 
Illustrations: Contr. U. S. Nat. Herb. 12: pi. 56, 57. 
Figure 27 is a copy of the first illustration above cited. 
Fig. 26.—Echinocereus reichenbaehii. Fig. 27.—Echinocereus baileyi. 
35. Echinocereus rigidissimus (Engelmann) Rose, Contr. U. S. Nat. Herb. 12: 293. 1909. 
Cereus pectinatus rigidissimus Engelmann, Proc. Amer. Acad. 3: 279. 1856. 
Echinocereus pectinatus rigidissimus Riimpler in Forster, Handb. Cact. ed. 2. 818. 1885. 
Echinocereus pectinatus robustus Bauer, Gartenflora 39: 513. 1890. 
Plants simple, erect, rigid, short-cylindric, 1 to 2 dm. high, 4 to 10 cm. in diameter, usually 
hidden by the closely set interlocking spines; ribs numerous, iS to 22, low; areoles approximate, 
elliptic, 5 to 6 mm. long; radial spines about 16, gray to reddish brown, arranged in horizontal bands, 
pectinate, rigid, 15 mm. long or less, often recurved; central spines none; flowers purple, 6 to 7 cm. 
long, fully as broad when expanded; perianth-segments oblong, 3 to 4 cm. long, acute; stamens 
numerous, shorter than the style; areoles on ovary somewhat floccose, very spiny; fruit globular, 3 
cm. in diameter, very spiny; seeds black, tuberculate, 1.5 mm. in diameter. 
Type locality: Sonora. 
Distribution: Southeastern Arizona and northern Sonora. 
This species is a great favorite in collections, although it does not last long. Its 
varicolored spines arranged in bands have given it the appropriate name of rainbow cactus, 
