1. Mammillaria sphaerica A. Dietrich, Allg. Gartenzeitung. 21: 94. 1853 (as Mamillaria).
Longmamma nipple cactus
Dolichothele sphaerica (A. Dietrich) Britton & Rose; Mammillaria longimamma de Candolle var. sphaerica (A. Dietrich) K. Brandegee
Plants many branched; branches 10-30(-50). Roots thick taproots, large in upper portion. Stems subspheric, 4-5 × 5-8 cm, soft, flaccid; tubercles 12-25 × 5-8 mm; axils slightly short woolly, without bristles; cortex and pith not mucilaginous; latex absent. Spines 13-15 per areole, whitish to yellowish, glabrous; radial spines 12-14 per areole, gray, bristlelike, 6-9 × 0.1 mm, stiff; central spines 1 per areole, porrect, straight, not hooked or curved, similar to radial spines, 3-6 × 0.25 mm; subcentral spines 0. Flowers 4 × 5-7 cm; outermost tepal margins entire (or minutely toothed near base); inner tepals bright yellow, paler near base, 20-30 × 4.5-8.5 mm; stigma lobes cream to pale yellow, 5-6 mm. Fruits greenish white to dull pinkish tan or maroon, ovoid to short cylindric, 10-15(-20) × 7 mm, juicy throughout; floral remnant weakly persistent. Seeds brown, 1.3 × 0.9 mm, pitted; testa soft or leathery, not hard or brittle; anticlinal cell walls straight to slightly curved; interstices equal or narrower than pit diameters; pits bowl-shaped. 2n = 22.
Flowering Jul; fruiting May. Tamaulipan thorn scrub on plains and low gravelly hills; 0-300 m; Tex.; Mexico (Nuevo León, Tamaulipas).
A proposed taxonomic reduction of Mammillaria sphaerica to varietal rank within the geographically disjunct and morphologically distinct Mexican species, M. longimamma, while plausible, has not yet been convincingly justified.