Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Areoles are the distinctive feature of cacti, and identify them as a separate family from other succulent plants. Areoles give rise to spines or, on certain cacti, small, detachable glochids which are an additional form of protection. The areoles on cacti are clearly visible. They generally appear as small light to dark colored bumps, out of which grow clusters of spines. Areoles represent highly specialized branches on cacti. They are believed to have evolved as vestigial leaves of cacti which were modified into spines over time. Thus, the branches became reduced to buds which give rise to the spines. This means that as cacti adapted and evolved to the desert climate, over time they got rid of branches and leaves, which were converted into areoles and spines to protect the plants, and to reduce water loss.

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