Mamillaria potsii Scheer in Salm Cact. Hort. Dyck. 104 (1850).

Cylindrical, 30 to 35 cm. high, 2.5 to 3 cm. in diameter,
somewhat branching: tubercles ovate, obtuse, very lightly
sulcate, 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): Chihuahua
(specimens from 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. (1848).
Mamillaria tuberculosa Engelm. Syn. Cact. 268 (1856).

Ovate to cylindrical, 5 to 15 cm. high, 2.5 to 5 cm. 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 8 mm. long
(uppermost rarely 10 to 12 mm.); central spines 5 to 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