28 
the: cactacejaF. 
while in Mexico it is called cabeza del viego. It has often been regarded as a variety of 
E. reichenbachii, but it is abundantly distinct. It is known in the trade under various 
names, among which are Cereus candicans and Echinocereus candicans, a name which 
belongs properly to a very different plant from Argentina, Cereus rigidissimus, C. robustior, 
and Echinocereus robustior, but none of which has been formally published. Here also 
belong the names Echinocereus rigidispinus, E. pectinatus robustior (Monatsschr. Kakteenk. 
7: 95. 1897), and perhaps E. pectinatus candicans (Monatsschr. Kakeenk. 3: m. 1893). 
Figs. 28 and 29.—Echinocereus rigidissimus. 
The largest specimen which we have seen was collected by Dr. J. W. Gidley near 
Benson, Arizona, in 1921. This plant was fully 2 dm. tall and 1 dm. in diameter. The 
spines were nearly all red, separated by very narrow bands of white ones giving the plant a 
brilliant and striking appearance. 
Illustrations: Cycl. Amer. Hort. Bailey 2: 519. f. 748; De Laet, Cat. Gen. f. 36; Schelle, 
Handb. Kakteenk. 133. f. 63, as Echinocereus pectinatus rigidissimus; Gartenflora 39: 
pi. 1331, as E. pectinatus robustus; Cact. Joum. 1: pi. for September; 2: 18; (?) Balt. Cact. 
Joum. 2: 88; West Amer. Sci. 7: 236, as Echinocereus candicans; Stand. Cycl. Hort. Bailey 
2: f. 1376. 
Figure 28 is from a photograph of a plant sent from Sonora, Mexico, by Carl Lum- 
holtz in 1909; figures 29 and 30 are from photographs taken by F. E. Lloyd at the Desert 
Laboratory of the Carnegie Institution, Tucson, Arizona; figure 31 is from a photograph 
of a plant in its natural habitat, taken by Dr. MacDougal at Calabasas, Arizona, in 1908. 
