Cactaceae

Succulent, usually leafless stems studded with areoles — small cushion-like pads that are the only place spines, hairs, and new growth emerge from; large, many-petalled radial flowers open directly from an areole and ripen into a fleshy berry.

Nearly all photosynthesis happens in the green, water-storing stem itself since true leaves are reduced to spines — an extreme adaptation to arid conditions found almost nowhere else in the plant kingdom.