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


A number of tropical trees exhibit structural features which appear strange to the eyes of those from most temperate regions. Many trees, particularly in swampy situations, develop thin flanges or plank buttresses from the bases of their trunks. It is suggested that these plank buttresses, which are more or less triangular in form and may extend for several metres up the trunks and out along the roots, confer greater stability on the often shallowly rooted trees. These plank buttresses are very inconvenient for tree fellers who often find it necessary to construct scaffolding so that the trunk can be sawn through above them.

Other trees increase support for their trunks by forming downwardarching prop roots. This can be seen, perhaps most conspicuously, in mangrove forests. In swampy situations many trees send up pneumatophores or breathing roots, through which air is taken in and transferred to the root system beneath the swamp. Pneumatophores are particularly conspicuous in saline coastal swamps inhabited by mangrove forests, but are also found in inland freshwater swamps. An unusual type of aerial root in tropical forests is the column root, which descends to the ground from horizontal branches, such as in the banyan figs. Individual banyan trees can sometimes spread out by this means over hectares of ground.