mammillaria

From the genus name.

mammillaria (plural mammillarias)

1. (botany) Any member of the cactus genus Mammillaria.
   • 1841, John Claudius Loudon, The gardener's magazine and register of rural & domestic improvement (volume 7, page 511)

     For some years back collections of mammillarias, from whatever parts of the world they came, were grown in our hothouses, and many of them are still kept there.