Mammillaria duwei Rogoz. & P.J.Braun
Mammillaria crinita subsp. duwei, Mammillaria nanasubsp. duwei, Mammillaria trichacantha subsp. duwei
Mammillaria duwei is a small, solitary, rarely offsetting cactus with stem up to 1.6 inches (4 cm) tall and up to 2.4 inches (6 cm) in diameter. The stem is dark green, with 28 to 36 radial spines. They are thin, white, brownish at base, interlacing and densely wrapped against the body. The central spine is yellowish, hooked, and is not present on all clones. The flowers are funnel-shaped, yellowish-cream to light yellow and up 0.8 inch (2 cm) in diameter.