MAMMILLARIA

(genus Mammillaria), any member of a large genus (more than 200 species) of low-growing cacti, native to the Western Hemisphere but concentrated in Mexico. It includes pincushion, fishhook, snowball, bird's-nest, golden-star, thimble, old woman, coral, royal cross, feather, and lemon ball cacti, all of which are small plants suitable to pot culture in cold climates. Mammillaria species bear tubercles arranged spirally on the cylindroid-to-globose stem; most species bear spines, either straight or hooked. Many small flowers, in a variety of colours, are borne in rings around the plant below the tip. Although some species may reach only 5 cm (2 inches) in height and only a few exceed 60 cm, most grow to less than 30 cm. A number of them, such as old woman cactus (M. hahniana) and feather cactus (M. plumosa), are woolly or hairy.