HOMEOSIS AND SHOOT CONSTRUCTION IN AZARA-MICROPHYLLA HOOK (FLACOURTIACEAE)

Each node of the dorsiventral shoot of Azara microphylla appears to have two leaves, a large and a small one, inserted on the same side of the stem. These have previously been interpreted as a leaf and a leaf-like stipule. There is a small, partly glandular, stipule-like structure at the outer edge of each pair of 'leaves', and one between the two 'leaves'. Developmental and anatomical studies suggest that there has been homoeotic replacement of the upper stipule by a 'leaf'. One of the small stipule-like structures, that at the outer edge of the larger 'leaf', appears to represent a normal, if reduced, stipule. The other two appear to be additional stipular structures related to the presence of homoeotic 'leaf'. Both the 'leaves' receive traces direct from the stem vasculature in a leaf-like manner. There are some structural anomalies which appear to have no functional significance and which may have arisen as side-effects of the homoeotic process.