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.
1. Cactus alternatus, sp. nov.
Subglobose, 10 cm. in diameter, simple: tubercles long (15 to 20 mm.) and spreading, with woolly axils: radial spines 3, rigid and recurved, 5 mm. long; central spines 3, very stout and much recurved, 20 to 30 mm. long, alternating with the radials; all ashy colored and often twisted: flower and fruit unknown.—Type in Herb. Coulter.
The few spines, with the very short radials alternating with the very long and stout centrals, furnish a striking character. Occasionally one of the centrals is wanting.