Wood and bark anatomy of Alluaudia (Didiereaceae) from Madagascar

Abstract

The anatomy of the secondary phloem and xylem of the tree Alluaudia ascendens Drake has been compared with that of Alluaudia humbertii Choux, both belonging to the endemic family Didiereaceae of Madagascar. The differences between the two species are small. In contrast with A. humbertii the cortex of A. ascendens, persistent during the lifetime of the tree, is thick and possesses a network of vascular bundles. These bundles are in connection with the vertical system of the stem via the horizontal ray system in non-conducting and conducting secondary phloem and secondary xylem. The function of these bundles is discussed.