Mammillaria johnstonii Britton & Rose

Solitary, body globular or eventually elongate, to 12 cm wide and 20 cm high. Tubercles prominent, pyramidal. Axils bare. Central spines 2(-6), 10-25 mm, brownish to black. Radial spines 10-16, 6-9 mm long, white, tips brown. Flowers whitish, 2 cm long and wide. Fruit scarlet.

NW Mexico

This species includes forms with widely varying spination, sometimes listed as varieties.

Source: Thompson, A, ; Forbes, S.; Spencer, R. (1997). Cactaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.

kingdom Plantae
phylum   Tracheophyta
class    Magnoliopsida
superorder     Caryophyllanae
order      Caryophyllales
family       Cactaceae
genus        Mammillaria Haw.