Plant globular, very small, the surface divided into numerous tubercles arranged in spiraled rows, mostly hidden by the numerous small spines; flowers very small, from near the center of the plant, arising from upper part of the spine-areole on the young tubercles; outer perianth-segments 3 to 5; inner perianth-segments few, often only 5; stamens few, usually 10, included; fruit small, clavate, red, few-seeded; seeds black, shining, rather large, with a large depressed hilum.
Type species: Mammillaria micromeris Engelmann.
We recognize one species, from western Texas and northern Mexico.
The generic name is from em on, dr/H] nipple, and avdog flower, indicating that the flower is borne on the tubercle.
This genus has heretofore been associated with the so-called Mammillaria, some of the species of which it resembles in its globose shape and small clavate red fruits. On account
*The name Epithelantha was given by Weber (Dict. Hort. Bois 804. 5898) as a synonym of Mammillaria micromeris and therefore was not formally published by him.
of the position of the flower, however, which is at the spine-areole, the genus is better referred to the sub-tribe, Echinocactanae, where in the genera Lophophora and Ariocarpus we have a similar fruit.
Mr. Charles Wright, in his field notes, first called attention to the central position of the flower of Mammillaria micromeris, and Engelmann, who discussed it (Cact. Mex. Bound. 4) in some detail, was in doubt as to its position. Dr. Weber seems to have been the first to determine the exact position of the flower and, recognizing its significance, proposed a new generic name for it, but he also referred it to Echinocactus and in still another place left it as a Mammillaria.
1. Epithelantha micromeris (Engelmann) Weber.
Mammillaria micromeris Engelmann, Proc. Amer. Acad. 3: 260. 1856.
Mammillaria micromeris greggii Engelmann, Proc. Amer. Acad. 3: 261. 1856.
Cactus micromeris Kuntze, Rev. Gen. Pl. 1: 260. 1891.
Cactus micromeris greggii Coulter, Contr. U. S. Nat. Herb. 3: 101. 1894.
Mammillaria greggii Safford, Ann. Rep. Smiths. Inst. 1908: 531. pl. 4, f. 1. 1909.
Plants small, simple or cespitose, nearly globular, but depressed at apex, 6 cm. in diameter or less; tubercles very low, small, arranged in many spirals, x mm. long; spines numerous, white, the lower radials about 2 mm. long, the upper radials on the young tubercles 6 to 8 mm. long and connivent over the apex, narrowly clavate, the upper half finally falling off; flowers from near the center of the plant in a tuft of wool and spines; flower very small, whitish to light pink, 6 mm. broad; perianth-segments 8 to 10; stamens 10 to 15; stigma-lobes; fruit 8 to 12 mm. long; seed 1.5 mm. broad.
Type locality: Western Texas.
Distribution: Western Texas and northern Mexico.
Writers generally, as well as dealers of these plants, are disposed to treat the large forms of this species as a variety, var. greggii, but we have observed no reason except size for this conclusion. The large form seems to extend throughout the range of the species proper. In June 1921, Mrs. S. L. Pattison sent us from western Texas an unusually large plant which was nearly 8 cm. high and 6 cm. in diameter.
The plant is known as button cactus. Its fruits, called chilotos, are slightly acid and are edible.
The names Epithelantha micromeris Weber and Echinocactus micromeris Weber, although both mentioned by him (Dict. Hort. Bois 804. 1898), were not formally published.
Mammillaria micromeris fungifera (Monatsschr. Kakteenk. 19: 140. 1909) is only a catalogue name.
Pelecyphora micromeris Poselger and Hildmann appears as a synonym of Mammillaria micromeris in Garten-Zeitung 4: 322. 1885.
Illustrations: Cact. Mex. Bound. pl. 1; 2, 1. f. 1 to 4; Cact. Journ. 1: 43; pl.  for February in part; Rümpler, Sukkulenten 200. f. 115; Dict. Gard. Nicholson Suppl. 514. f. 4; Förster, Handb. Cact. ed. 2. 267. 1. 26, 27; Cycl. Amer. Hort. Bailey 1: 203. f. 302; Stand. Cycl. Hort. Bailey 5: f. 3016; Amer. Garden 11: 460; Monatsschr. Kakteenk. 20: 126; 29: 81; Schelle, Handb. Kakteenk. 248. f. 166, 167; Garten-Zeitung 4: 323. f. 76; Watson, Cact. Cult. 167. f. 65; ed. 3. f. 42; Blanc, Cacti 71. f. 1394, as Mammillaria micromeris; Cact. Mex. Bound. pl. 2, f. 5 to 8; Blanc, Cacti 71. f. 1395, as Mammillaria micromeris greggii; Ann. Rep. Smiths. Inst. 1908: pl. 4, f. 1, as Mammillaria greggii.
Figure 102 shows a plant in fruit, collected by Dr. Rose at Langtry, Texas, in 1908 (No. 11612).
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