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
mm.), stout, porrect or deflexed: flowers about 2.5 cm. 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 strobiliformis 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 the type 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.
Specimens examined: Texas (Wright 18, 19, 20, 23, 24, 29,
30,31,32, 535, of 1849 and 1852; Bigelow of 1852; Engelmann, with
no number or date; Evans of 1891): Chihuahua (Pringle 250, 251 in
part, and 258 of 1885): Coahuila (Palmer of 1880): also specimens
from Coll. Salm. Dyck in 1857; also growing in Mo Bot. Gard. 1893
(specimens, sent by G. G. Briggs in 1892 from El Paso, Texas.
The identification of Engelmann's tuberculosa with Scheer's
strobiliformis was made by Dr. Engelmann himself upon an
examination of Scheer's type. The use of the specific name
tuberculosa is necessitated by the law of homonyms, as
strobiliformis had been used twice already before it was taken up
by Scheer. M. strobiliformis Muhlenpf. is C. scolymoides
sulcatus; and M. strobiliformis Engelm. is C. conoideus.