Differs from the last form (var. greggii) chiefly in its
cespitose habit, much larger tubercles, and two unusually stout
and short central spines (fide Engelmann, who examined specimens
in Coll. Salm-Dyck).

Credited to Mexico in general, but said by Budd to occur within
the southern border of Pecos County, Tex.

** Central spines present and one or more hooked.
+ Mostly globose and simple plants (occasionally somewhat
cylindrical).

15. Cactus wrightii (Engelm.) Kuntze. Rev. Gen. Pl. 261 (1891).

Mamillaria wrightii Engelm. Syn. Cact. 262 (1856).

Globose or depressed globose (top-shaped below), 3 to 7.5 cm. in
diameter, simple: tubercles 10 to 12 mm. long, with naked axils:
radial spines 8 to 12, white (the upper dusky-tipped), pubescent,
8 to 12 mm. long central spines mostly 2 (usually side by side
and divergent), rarely 1 or 3, scarcely longer, hooked and
reddish-black: flowers 2.5 cm. long, bright purple: fruit about
2.5 cm. long, somewhat subglobose, purple: seeds 1.4 mm long,
black and pitted. (Ill. Cact. Mex. Bound. t.8. figs. 1-8) Type,
Wright of 1851 in Herb. Mo. Bot. Gard.

High plains and rocky places, from the Upper Pecos, east of Santa
Fe, N. Mex., southward through extreme southwestern Texas
(between the Pecos and El Paso), and into Chihuahua (near Lake
Santa Maria).