What is mammillaria marcosii?

Mammillaria marcosii is a species of cactus that is native to Mexico. It belongs to the family Cactaceae and is commonly known as the Marcos' nipple cactus. It is a slow-growing cactus that can reach up to 2 inches (5 cm) in height and 6 inches (15 cm) in diameter. It has cylindrical, green stems that are covered in small white spines. The flowers of Mammillaria marcosii are pink or red and usually bloom in the spring and summer. It requires well-drained soil and full sun to thrive. While it is not considered endangered, it is a relatively uncommon plant in cultivation.