Cactus succulents

Stems 1 to several, more or less spherical, dark green, to 2 inches in diameter, covered with spirally arranged projections called tubercles; areoles at tubercle tips, white-woolly when young; perianth parts numerous, petal-like, in several rows; outer parts greenish or brownish; inner parts pink to reddish purple; tips sharply pointed; stamens numerous, anthers bright orange. Fruits are berries, fleshy, oblong to club-shaped, green when mature; seeds tiny, pitted, yellowish brown.