Very fleshy and commonly leafless plants; the stems globose or columnar and angled, or of flattened joints, mostly prickly. Flowers solitary, sessile. The numerous sepals and petals adherent to the 1-celled ovary. Style 1, stigmas many. Fruit a 1-celled berry with many seeds on the walls.
1. Mamillaria. Stems globose or oval, covered with spine-bearing tubercles, the flowers between these.
2. Opun'tia. Stems of flattened joints, bearing very small awl-shaped leaves with clusters of bristles in their axils.
Haw. M. vivip'ara, Haw. Stems 1-5 inches high, the tubercles bearing bundles of 5-8 reddish-brown spines, surrounded by numerous grayish ones. Flowers purple. - N. W. plains.
Tourn. Prickly Pear. 0. Rafines'quii, Engel. Stem prostrate, deep green. Bristles reddish-brown. Spines few. Flowers yellow, sometimes with reddish centre. - Point Pelee.