Allg. Gartenzeitung 16: 20. 1848.
Plants unbranched, protruding relatively little above soil. Roots obconic taproots; secondary-roots diffuse. Stems top-shaped, flat-topped (aerial part sometimes hemispheric in old age or in dense subtropical vegetation), protruding above ground 0–2 × (4–) 7.5–15 cm, firm; tubercles 9–15 (–20) × 3–7 mm; axils with short wool, bristles absent; cortex and pith not mucilaginous; latex abundant in healthy tissue throughout cortex of stem, tubercles, and sometimes flower receptacle, sticky, white. Spines (8–) 10–18 (–27) per areole, usually brownish, darker at tip, glabrous; radial spines (8–) 10–22 (–26) per areole, white to white-and-brown or brown, needlelike, 6–15 (–16) mm, stiff, abaxial spines longest; central spines (0–) 1 (–4) per areole, porrect or ascending, not hooked, (0.5–) 2–8 × 0.15–0.45 mm; subcentral spines 0. Flowers 1.9–3.8 × 1.5–3 cm; outermost tepal margins entire; inner tepals white, greenish or cream to pale-pink, with tan, pink, greenish, or brownish midstripes, 11–19 × 2–2.5 mm; stigma lobes externally green, internally green or red (or pink), 2.5–3 mm. Fruits brilliant red: scarlet, carmine, or crimson, obovoid to clavate, 10–35 (–40) × 5–8 mm, juicy only in fruit walls; floral remnant weakly persistent. Seeds reddish-brown, sometimes yellowish when fresh, 1–1.2 mm, deeply pitted; testa thin, relatively flexible; anticlinal cell-walls sinuate, interstices narrower than pit diameters; pits cavernous or deeply concave. 2n = 22.
Ariz., N.Mex., Okla., Tex., n Mexico
Varieties 2 (2 in the flora).
Green fruits of Mammillaria heyderi with fully mature, viable seeds precede the ripe (elongate) fruits by six months to a year.
|1||Central spines 0.15-0.35 mm diam.; radial spines (7-)13-17(-26) per areole, abaxial radial spines 6-11(-16) mm; e of El Paso, Texas, New Mexico, Oklahoma.||Mammillaria heyderi var. heyderi|
|1||Central spines 0.35-0.45 mm diam.; radial spines 10-14 per areole, abaxial radial spines 9-15 mm; El Paso, Texas, w to Arizona||Mammillaria heyderi var. bullingtoniana|