Copiapoa humilis (Philippi) Hutchison

Stems mostly clustering, more or less spherical, dark green to blackish or brown, arising from a tuberous root. Ribs 8-14. Areoles with 0-4 central spines and 7-13 radial spines. Flowers 3-4 cm long.

N Chile

C. tenuissima F. F. Ritter is an invalid name for a similar but smaller plant with 13-16 ribs and flowers less than 3 cm long.

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        Copiapoa Britton & Rose