oblong-ovate, large at base, 4 to 5 cm. long: radial spines 7 or
8, radiant and equal, 8 to 10 mm. long or more, more or less
pubescent; central spines 1 to 3, somewhat longer and spreading:
flower 4 cm. long, becoming 6 cm. broad when fully expanded,
yellow. (Ill. DC. Mem. Cact. t. 5.)

II. CORYPHANTHA. Flowers from the base of a groove on young or
nascent tubercles (hence appearing terminal), mostly large:
spines never hooked (except in the doubtful C. brunneus).

* Flowers yellow.
+ The originally central flowers pushed aside by the continuous
development of new tubercles: usually a single prominent
central spine.

37. Cactus missouriensis (Sweet) Kuntze, Rev. Gen. Pl. 259
(1891).

Cactus mamillaris Nutt. Gen. i. 295 (1818), not Linn. (1753).
Mamillaria missouriensis Sweet, Hort. Brit. 171 (1827).
Mamillaria simplex Torr. & Gray, Fl. N. Am. i. 553 (1840).
Mamillaria nuttallii Engelm. Pl. Fendl. 49 (1849).
Mamillaria notesteinii Britton, Bull. Torr. Bot. Club, xviii,
367 (1891).

Globose, 3.5 cm. in diameter, simple or nearly so: tubercles
ovate-cylindrical, 12 to 14 mm. long, slightly grooved: radial
spines 13 to 17, straight, whitish, setaceous, somewhat unequal,
8 to 10 mm. long; central spine more robust, straight and
porrect, puberulent, 10 to 12 mm. long, often wanting: flowers