Mamillaria micromeris greggii Engelm. Syn. Cact. 261 (1856).
Larger (2.5 to 5 cm. in diameter) and becoming oblong, with
larger globose-ovate tubercles (2 to 2.5 mm. long), fewer rigid
spines all radiant (interior 5 to 7 shorter and stouter, 1 to 2
mm. long; the outer 15 to 18, 3 to 4 mm. long), and fruit 1.5 to
2 mm. long. (Ill. Cact. Mex. Bound. t. 2. figs. 5-8) Type, Gregg
508 in Herb. Mo. Bot. Gard.
Mountain ridges near Saltillo, Coahuila. Said by Budd to occur
within the southern borders of Pecos County, Tex.
Specimens examined: Coahuila (Gregg 508; Palmer of 1880).
It is a question whether this variety does not merely represent
an older and better developed plant than those upon which the
species is based. Mr. Harry I. Budd, who has made extensive
collections of Texan and Mexican Cacti for the market, reports
that it is impossible to separate sharply the variety from the
species in the field, and regards the difference merely as one of
age. Unfortunately, only living material of the species could be
examined, but its characters seem well sustained even in the most
vigorous plants, some of which reach the size of the variety.
Through this variety the species is brought very near the
following: