The prickly grey tips of the stem ridge tubercles of Quaqua mammillaris are straight, pointing outwards. The second, younger stem, partly visible in the photo although out of focus, has orange or light brown prickles.
This plant was seen at the Minwater farm near Oudtshoorn in April. It may grow better in the veld when sheltered by shrubs, although well developed specimens fully exposed to the elements are also found. It often grows among spekboom or guarri in clay soils. In shade the hairless stems might be greener (Vlok and Schutte-Vlok, 2010; iSpot).