MAMILLARIA Haw. Synop. 177 (1812), not Stackh. (1809).
Usually globose to oblong plants (simple, branching or
cespitose), but sometimes slender-cylindrical, covered with
spine-bearing tubercles: flower-bearing areola axillary (with
reference to tubercles), entirely separate from the terminal
spine-bearing areola, although sometimes (Coryphantha) connected
with it by a woolly groove along the upper face of the tubercle:
ovary naked: seeds smooth or pitted: embryo usually straight,
with short cotyledons. Originally defined by Linnaeus in his
Systema, ed. l (1735).
The Linnaean genus Cactus of 1753 included 22 species and was
coextensive with the present order. In 1812 the species were
separated by Haworth into five genera, the original generic name
Cactus being discarded. Among these species C. mamillaris seems
to have stood as the type, not only of the Linnaean genus Cactus,
but also of Haworth's Mamillaria, and as such should retain the
original generic name. Besides, Mamillaria was used as the
generic name of an alga in 1809. Cactus mamillaris L. is the
West Indian Mamillaria simplex Haw.
From one point of view the two sections of the genus
(Eumamillaria and Coryphantha) deserve generic separation, for
the character of grooveless and grooved tubercles seems to hold
without exception, and the sections are separated with more
certainty than are certain species of Coryphantha and
Echinocactus. If genera are simply groups of convenience the
separation should be made.
I. EUMAMILLARIA. Flowers from the axils of the older or
full-grown tubercles (hence usually appearing lateral), mostly
small, and generally from whitish to pink or red: tubercles never
grooved: fruit almost always clavate and scarlet.
A. Tubercles more or less quadrangular.
* Central spines not hooked.
+ More than one central spine.