Greek diskos—disk, referring to the flattened stems.
Body mostly solitary, low-growing, flattened spherical to spherical. Stems spiny, the ribs distinct or tuberculate. Flowers nocturnal, arising from an apical, often sunken, woolly head (cephalium), white; summer. Flower tube narrow, scaly. Fruit mostly spherical to club-shaped, fleshy.
The 2 commonly cultivated species are keyed out below. D. placentiformis (Lehm.) K. Schum. from Brazil (Bahia) is generally known under its synonym D. bahiensis Britton & Rose while D. horstii Bruining & Brederoo from E Brazil is generally grown as a cristate form grafted onto other cacti.
Flowers nocturnal, fragrant, white, arising from a cephalium.
5-8 species from Brazil, E Bolivia and N Paraguay.
Taylor, N.P. (1981).
Source: (1997). Cactaceae. In: . 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.