12 THE CACTACEAE. 



Plants simple, globose to conic, glaucous, small, up to 3 cm. high, ver}^ spiny; ribs usually 8, 

 broad, somewhat tubercled; areoles approximate; spines highly colored, sometimes bright red or 

 yellowish or red and 3'ellow ; 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 ovarj' and flower- tube 

 imbricated, ovate, with scarious and ciliate margins ; filaments white to purple ; stigma-lobes pale to 

 pinkish 3-ellow; fruit small, about i 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. 



Echinocadus tricolor, E. castaniensis, and E. bicolor niontemorelanus Weber (all in 

 Diet. Hort. Bois 465. 1896) are usually referred here but were never described. 



Illustrations: Jard. Fleur 3: pi. 270, as Echinocactus ellipticus; Gartenflora 38: 106. f. 

 21, as Echinocactus bolansis; Curtis's Bot. IMag. 76: pi. 4486; Jard. Fleur i : pi. loi ; Loudon, 

 Encycl. PI. ed. 3. 1377. f. 19375; Gard. Mag. Bot. i: 40, as E. rhodophthalmus; Curtis's 

 Bot. ^lag. 78: pi. 4634, as E. rhodophthalmus ellipticus; Karsten and Schenck, Vegeta- 

 tionsbUder 2: pi. 20, c; Pfeiffer, Abbild. Beschr. Cact. 2: pi. 25; Schumann, Gesamtb. Kak- 

 teen Xachtr. 87. f. 14; Ann. Rep. Smiths. Inst. 1908: pi. 13, f. 2; Bliihende Kakteen 2: 

 pi. 74; Monatsschr. Kakteenk. 12: 7; 29: 81; Schelle, Handb. Kakteenk. 157. f. 86; Blanc, 

 Cacti 41. No. 412, as E. bicolor. 



Figure II is from a photograph taken by Robert Runyon at Saltillo, Mexico, in 1921. 



12. Thelocactus pottsii (Salm-DA-ck). 



Echinocactus pottsii * Salm-Dyck, Allg. Gartenz. 18: 395. 1850. 

 Echinocactus bicolor pottsii Salm-Dyck, Cact. Hort. Dyck. 1849. 173. 1S50. 

 Echinocactus heterochromus Weber, Diet. 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, i 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 ovar\' 

 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, ri dged 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 (Diet. 

 Gard. 4: 540. f. 23 and Suppl. f. 359) where the species is described as follows: flow^ers 

 yellow, about 2 inches across, short-tubed, several expanding together at the top of the 

 stem; stem globular, 1^2 feet in diameter: ridges about a dozen, rounded and even, with 

 acute sinuses ; spines i 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 Calif ornian 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. 



