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Forest Vines to Snow Tussocks: The Story of New Zealand Plants

Teeth, Pulvini and Drip Tips

Teeth, Pulvini and Drip Tips

The proportion of woody dicotyledon species in the conifer broadleaf page 37forest with smooth-margined leaves or leaflets is lower than that of tropical forests: about 56 per cent compared with 80 per cent recorded, in a Nigerian forest.21 Godley24 has observed that some New Zealand trees have much more prominent teeth on the leaves of young plants than on those of adults; for example wineberry (Aristotelia serrata) and ngaio (Myoporum laetum). In other cases, some trees with smooth-margined adult leaves or leaflets have juvenile leaves with toothed or lobed margins; for example puriri (Vitex lucens), titoki (Alectryon excelsus), kohekohe (Dysoxylum spectabile) and several species of Hebe.

Pulvini also are not common. The species of maire (Nestegis) have dark-coloured pulvini at the petiole bases and kohekohe (Dysoxylum spectabile), titoki (Alectryon excelsus) and king fern (Marattia salicina) have them at the bases of the leaflet petioles. Hinau (Elaeocarpus dentatus) is an interesting case. The adult leaves do not have pulvini, but on juvenile leaves they can be observed at each end of the petioles. The larger-leaved tropical species of Elaeocarpus have prominent pulvini in the same position on adult leaves.

Drip tips are neither strongly developed nor very common in the New Zealand forest. In fact the most that can be said is that ten or so species tend to have slightly to moderately drawn out leaf tips especially when growing under sheltered, shady conditions. Perhaps both drip tips and pulvini were better developed in the ancestors of our present trees.