Areole

Areolae are a distinctive feature and always existing in two closely related with each other plant families, the cactus family ( Cactaceae ) and the Didiereaceae. They can be evolutionarily traced back to arising in the axils of short shoots. Over the evolution of plants, the leaves were gradually reduced in number and size in order to reduce the evaporation surface and converted into thorns to ward off predators.

Areoles of Didiereaceae

The bare areolae of Didiereaceae form warty elevations from which the leaves and thorns spring. You is their origin of short shoots still to be considered.

Areoles of cacti

The areoles of cacti are circular to oblong- oval, felt-like pad from which spring usually thorns and often hair and bristles.

• The species of the genus Pereskia originally appearing ( subfamily Pereskioideae ) produce from the hairy areoles next thorns still normal leaves.
• In the subfamily Opuntioideae the areoles bear, in addition to not always trained normal spines very fine, barbed spines, the so-called glochids, as well as short-lived, pfriemförmige leaves.
• The species of the subfamily Cactoideae are completely leafless. In most species arise from the areoles both branches and flowers. In Mammillaria and closely related genera flower formation is shifted to the axillae. These lie between the areoles bearing warts are also tomentose and often wear hair and bristles. In some genera, such as Ariocarpus the separation of areola and Axille is incomplete, then they are connected to each other by a furrow.

Areola of Echinocactus grusonii.

Areoles of Pereskia grandifolia.

Mammillaria marksiana bearing areoles with spines between them on the warts and white, woolly axils.

Swell

• Sprossachse