118 
closely appressed-imbricate (‘‘giving the plant the appearance of a 
pineapple or cone”): radial spines 10 to 16, ashy to white, straight and 
stout, 6 to10 mm. long, the upper longer (10 to 15 mm.); central spines 3 
to 5, stouter, brownish-black, 10 to 16 mm. long, the two or three smaller 
ones erect-spreading, the single lower one more rigid, porrect or deflexed, 
15 to 20 mm. long: flowers 2 to 3 cm. long and wide, deep purple: fruit 
unknown. (JU, DC. Mein. Cact. t. 2)—Type unknown. 
On rocks, Coahuila and Nuevo Leon to San Luis Potosi and southern 
Mexico. 
Specimens examined: COAHUILA (Palmer 378 of 1882; Pringle 3117 
of 1890): NUEVO LEON ( Wislizenus of 1847): SAN Luis Povrost (Posel- 
ger of 1851; Hschanzier of 1891). 
55. Cactus potsii (Scheer) Kuntze, Rev. Gen. Pl. 261 (1891). 
Mamillaria potsit Scheer in Salm Cact. Hort. Dyck. 104 (1850), 
Cylindrical, 80 to 35 em. high, 2.5 to 3 em. in diameter, somewhat 
branching: tubercles ovate, obtuse, very lightly suleate, with somewhat 
woolly axils: radial spines very numerous (entirely covering the whole 
plant), slender and white; central spines 6 to 12, stouter from a broad 
base: flowers large, green, or reddish: fruit red—Type unknown. 
From the Rio Grande region, near Laredo, Texas, to Chihuahua. 
Specimens examined: TEXAS (Poselger of 1851): CHINUANUA (speci- 
meus trom Coll. Salm-Dyck.), 
56. Cactus tuberculosus (Engelm.) Kuntze, Rev. Gen. Pl. 261 (1891), 
Mamillaria strobiliformis Scheer in Salm Cact, Hort. Dyck. 104 (1850), not 
Muhlenpf. (1848), nor Engelm, (1818), 
Mamillaria tuberculosa Engelm. Syn. Cact. 268 (1856), 
Ovate to cylindrical, 5 to 15 em. high, 2.5 to 5 em. in diameter, simple 
or branching at base: tubercles short-ovate from a broad base, 5 to 6 
mm. long, deeply grooved, crowded and imbricate, at length covering 
the older parts as naked and gray corky protuberances: radial spines 
20 to 30, slender but stiff, white, radiant and interwoven with adjacent 
clusters, 4 to 8mm. long (uppermost rarely 10 to 12 mm.); central spines 
5to 9, stouter, purplish above, the upper ones longer, erect, 10 to 14. mm. 
long (Sometimes even 16 to 18 mm.), the lower one shorter (6 to 8 mm.), 
stout, porrect or deflexed : flowers about 2.5 em. in diameter, pale purple: 
fruit oval, elongated (sometimes almost cylindric), red, about 18 mm. 
long: seeds subglobose, brown and pitted, very small (0.8 to 1.2 mm. 
long). (Ill. Cact. Mex. Bound. t. 12. figs.1-16)—Type of Scheer’s. stro- 
biliformis is unknown; but the specimens of Prince Salm-Dyck in Herb. 
Mo. Bot. Gard. are marked “authentic” by Dr. Engelmann. The 
Wright specimens in the same Herb. represent thetype of M. tuberculosa 
Engelm. 
From the mountains of extreme southwestern Texas (common west 
of Devil’s River), southward into Chihuahua and Coahuila. Fl. May- 
June. 
