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Agavaceae:
Amaryllidaceae:
Cactaceae:
Iridaceae:
Liliaceae:
Ranunculaceae:
Areole, Glochid
The areole is the absolute diagnostic feature of the family Cactaceae - the cacti. If a plant has areoles it is a cactus: if it hasn't, it isn't. The areole consists a cushion of bristles, usually, but not always, bearing spines. In morphological terms they are regarded as abortive branch buds. The spines are sometimes regarded as vestigial leaves, though the fact that some cacti have both leaves and spines leaves a question mark over this assumption. See examples of cacti with areoles and a non-cactus succulent without.
Beware the Glochid !
The areoles of the genus Opuntia (and some closely related genera) often feature glochids. These are small, thin, sharp, barbed bristles which have the unpleasant habit of getting into the skin. When rubbed, the main shaft breaks off, leaving the tip, too thin to see, and being barbed, almost impossible to remove. Learn more about glochids.
