Body compressed spherical. Ribs mostly 7-9, straight, tubercles obscure. Central spines eventually 1-2, radials 3-6, to 5 mm long, curved. Flowers short tubed with pale purplish segments paler at the tip and with a reddish midstripe; throat dull red. Fruit green.

Bolivia

 

G. spegazzini Britton & Rose from N Argentina is also red throated and differs in having spines to 2 cm long.

Species in this group that do not have a red throat include G. bruchii (Speg.) Hosseus from N Argentina, G. mihanovichii (Fric & Gürke) Britton & Rose from N Paraguay and G. horstii Buining from S Brazil. G. mihanovichii is perhaps best known for the brightly coloured and strongly promoted colour cultivars, mostly red, pink and yellow, that are grafted on the top of green stock; it has greenish flowers.

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. (as Gymnocalycium cardenasianum)