Escobaria vivipara ssp.arizonica

Escobaria vivipara is a species that deserves more attention from cactus collectors. There are couple dozens of recognized species in the genus, and much more interesting forms that do not get recognition in nomenclature.
The plant in the picture belongs to a very wide spread in Western US and variable species. The bright flowers are readily produced, and growing from seed is easy. Different forms of that species show various spine patterns, some all white, some with neat shorter spines, many red-brown like in the picture. The plants are known as singular in culture, but eventually they form large clumps.
The generic name was given by Britton and Rose in their historic work The Cactaceae published in early 20th century. The name honors brothers Romula and Numa Escobar, 'distinguished Mexicans'. In case you are like me get curious here is the short biographical article on them: http://dnn.epcc.edu/nwlibrary/borderlands/26/escobar.htm