Solitary, to 12cm across.
This cactus is known as a peyote due to B.P. Reko's chemical studies which found that it contained alkaloids similar to those in the well known Ariocarpus peyote species. From this data alone comes the assumption of O. denegrii being a peyote species. Extracts of this cactus have been shown to have antibiotic activity.
Cacti, The Illustrated Dictionary, Preston-Mafham, 1991 The Last Peyotero
data regenerated on Mon, 18 Feb 2019 12:36:56 -0500 [bcm v4.0]