12 THE CACTACEAE. 
Plants simple, globose to conic, glaucous, small, up to 3 cm. high, very spiny; ribs usually 8, 
broad, somewhat tubercled; areoles approximate; spines highly colored, sometimes bright red or 
yellowish or red and yellow; radial spines 9 to 18, widely spreading or sometimes bent backward at tip, 
3 cm. long or less; central spines usually 4, ascending or porrect, all straight, 3 to 5 cm. long, subu- 
late; flowers large, 5 to 6 cm. long and fully as broad when expanded; outer perianth-segments pale 
purple; inner perianth-segments deep purplish pink, oblong, acute; scales on ovary and flower-tube 
imbricated, ovate, with scarious and ciliate margins; filaments white to purple; stigma-lobes pale to 
pinkish yellow; fruit small, about 1 cm. long, dehiscing by a large irregular basal opening; seeds 2 
mm. long, black, broader at apex, tuberculate with a circular and depressed basal hilum. 
Type locality: Mexico. 
Distribution: Southern Texas to central Mexico. 
Echinocactus tricolor, E. castaniensis, and E. bicolor montemorelanus Weber (all in 
Dict. Hort. Bois 465. 1896) are usually referred here but were never described. 
Illustrations: Jard. Fleur 3: pl. 270, as Echinocactus ellipticus ; Gartenflora 38: 106. f. 
21, as Echinocactus bolansis ; Curtis’s Bot. Mag. 76: pl. 4486; Jard. Fleur 1: pl. ror; Loudon, 
Encycl. Pl. ed. 3. 1377. f. 19375; Gard. Mag. Bot. 1: 40, as E. rhodophthalmus ; Curtis’s 
Bot. Mag. 78: pl. 4634, as E. rhodophthalmus ellipticus; Karsten and Schenck, Vegeta- 
tionsbilder 2: pl. 20, c; Pfeiffer, Abbild. Beschr. Cact. 2: pl. 25; Schumann, Gesamtb. Kak- 
teen Nachtr. 87. f. 14; Ann. Rep. Smiths. Inst. 1908: pl. 13, f. 2; Bliihende Kakteen 2: 
pl. 74; Monatsschr. Kakteenk. 12: 7; 29: 81; Schelle, Handb. Kakteenk. 157. f. 86; Blanc, 
Cacti 41. No. 412, as E. bicolor. 
Figure 11 is from a photograph taken by Robert Runyon at Saltillo, Mexico, in 1921. 
= 12. Thelocactus pottsii (Salm-Dyck). 
Echinocactus pottsi * Salm-Dyck, Allg. Gartenz. 18: 395. 1850. 
Echinocactus bicolor pottsii Salm-Dyck, Cact. Hort. Dyck. 1849. 173. 1850. 
Echinocactus heterochromus Weber, Dict. Hort. Bois 466. 1896. 
_ Globular or somewhat depressed, ‘10 to 15 cm. in diameter, somewhat glaucous, yellowish; 
ribs 8 or 9, broad and obtuse, more or less distinctly tubercled; areoles large, closely set on old plants, 
densely felted when young, naked in age; spines variable as to number, shape, size, and color; radial 
spines 7 to 10, acicular, usually terete, straight or incurved, more or less banded with red and white 
or pale yellow, 1 to 3 cm. long; central spines several, stout-subulate, more or less flattened, 3 or ; 
4 cm. long, often white, but sometimes banded with red; flowers 5 to 6 cm. long; scales on ovary ; 
and flower-tube ovate, greenish; margins thin and ciliate; inner perianth-segments light purple, : 
darker at base, oblong; stigma-lobes yellow; fruit globose, small, 1.5 cm. in diameter; seed tubercu- 
ate, black, truncate at base, ridged on back; hilum basal, white, circular. 
Type locality: Near Chihuahua City. ' 
Distribution: Chihuahua to Coahuila, Mexico. { 
There are three illustrations passing as Echinocactus pottsii, none of which agrees with : 
the original description of Salm-Dyck. Two of these are in Nicholson’s Dictionary (Dict. 
Gard. 4: 540. f. 23 and Suppl. f. 359) where the species is described as follows: flowers 
yellow, about 2 inches across, short-tubed, several expanding together at the top of the 
stem; stem globular, 114 feet in diameter: ridges about a dozen, rounded and even, with 
acute sinuses; spines 1 inch long, bristle-like, arranged in clusters of 7 or 9, with a cushion 
of white wool at the base. , 
Nicholson indicates that his plant of E. pottsii was from California and introduced 
into cultivation in 1840. There is no Californian species which answers this description 
or illustration. 
_The other illustration is Schumann’s (Gesamtb. Kakteen 328. f. 57), which is somewhat 
similar to the above. Schumann states that the radial spines are commonly 6, spreading 
and yellow; central spines solitary. We are not able to identify this illustration; it sug- 
gests some Echinocereus as much as it does an Echinocactus. 
—— 
* 
Salm-Dyck (Cact. Hort. Dyck. 1849. 35. 1850) credits this name to Scheer. 
