M. karwinskiana and M. schiedeana self-sterile or fertile?

[mattcoondawg]

Are M. karwinskiana and M. schiedeana self-fertile or self-sterile?

[iann]

Mammillarias, and most other cacti, should be considered self-sterile until proved otherwise. I don't have a single Mammillaria that is reliably self-fertile. Many of them throw an occasional fruit without my help, although perhaps with help from someone smaller, but they don't seem to contain good seed.