Mammillaria gracilis var 'Arizona Snowcap' [Monstrose]
Mammillaria gracilis var 'Arizona Snowcap' - a Monstrose (monstrosa) Mutant-form version of Mammillaria gracilis.
The last two plants are the Mother plants. Very graceful and fragile-looking, although being a very tough and hardy plant.
As you can see they flower very readily, beautiful small yellow flowers scattered throughout the snowy texture of their white spines. Truly a beautiful cactus and one of my all-time favorite non-Trichocereus cactus out there. :)