Mammillaria Haworth, Syn. Pl. Succ. 177-178. 1812; Zimmerman & Parfitt, Fl. North Amer. @ eFloras.org vol. 4: 221, 239.

Mostly erect, branched or unbranched, deep-seated in substrate or not, latex usually present. Stem succulent, unsegmented, green to grey-green, spheric, cylindric or turbinate, often flat-topped, 1-25 cm x 1.8-20 cm; tubercles distinct, not confluent into ribs, pyramidal, conic or cylindric, 3-25 mm x 2-9 mm; areoles of 2 kinds: vegetative with clusters of spines at tip; reproductive areoles in axils of tubercles, woolly, bristly or naked; spines few to many per areole, radial and central, sometimes central spines absent. Flowers diurnal, in ring distant from stem apex or nearly apical at anthesis forming a ring around new growth, in axils of tubercles, funnelform, campanulate or rotate. Outer tepal margins entire or fringed; inner tepals yellow, white, rose-pink, magenta or maroon. Stamens many. Ovary lacking scales and spines; stigma lobes up to 8 mm long. Fruit indehiscent, usually pink, bright red or greenish, clavate, cylindric, ovoid or barrel- shaped, usually juicy; scales and spines absent.

138 species

Mammillaria compressa DC., Mem. Mus. Hist. Nat. xvii. 112. 1828; Encyclopedia of Cacti; Cactus compressus (DC.) Kuntze, Revis. Gen. Pl. 1: 260. 1891; Mammillaria angularis var. compressa (DC.) K. Schum., Gesamtbeschr. Kakt. 577. 1898; M. angularis f. compressa (DC.) Schelle, Handb. Kakteen Kult. 265. 1907; Neomammillaria compressa (DC.) Britton & Rose, Cactaceae (Britton & Rose) 4: 90, figs. 84-88. 1923.

Erect, unbranched. Stem unsegmented, grey-green, globular, 8-10 cm in diameter, deep- seated, firm; tubercles distinct, ca. 1 cm x 1 cm, conic, not confluent into ribs. Areoles of 2 kinds: vegetative areole at tip of the tubercle; reproductive areoles in the axils of the tubercles, woolly. Vegetative areole containing 4-8 spines, all spines radial, central spines absent, spines up to 2 cm long, grey or grey-white, straight. Flowers diurnal, in ring distant from stem apex, campanulate or +/- funnelform, solitary in axils of tubercles, sessile, bisexual, actinomorphic, epigynous, purple-pink, 1.5-1.6 cm x 1.5 cm. Perianth tube ca. 5 mm long, throat ca. 1 cm long; perianth segments up to 20, outermost ring of 5 unequal tepals, green, oblong, mucronate; middle ring of 5 equal brownish tepals and inner tepals, generally 10, 6 mm x 2 mm, purple-pink, shining, oblong, mucronate, tepals margin entire. Stamens many; inserted in perianth tube and throat, filaments incurved, pink, 3-4 mm long; anthers cream coloured, ca. 1.5 mm long. Style ca. 1 cm long, pink, stout; stigma lobes 5-6, ca. 2 mm long.

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