<P> Stipule spines on Acacia xanthophloea . </P> <Li> <P> Areoles and spines of the tree - like Pereskia grandifolia . </P> </Li> <P> Areoles and spines of the tree - like Pereskia grandifolia . </P> <Li> <P> Spines of Mammillaria balsasoides </P> </Li>

What is the function of the leaf stalk