Pneumatophores

Pukatea, when growing in swamps, also forms large pneumatophores. These are basically shield-shaped and sometimes several times higher than they are wide (Figs. 10, 11). These pneumatophores originate when a root tip arches above the swamp surface and then grows back in again so forming a loop. Wood is then added mostly on the upper and lower sides of the loop which leads to the eventual shield-shape. The pneumatophores are covered with mosses and have pustules (lenticels) of loose corky cells, through which air enters the root system.

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Swamp maire (Syzygium maire) is often associated with pukatea in swamp forests and it too forms specialised pneumatophores. In this case, however, they are not woody loops, but smaller, finger-like and rather spongy root tips several centimetres long. They are orangey-brown in colour and often branch near the base to form coral-like clusters. A longitudinal section through such a 'peg root' reveals a white outer cylinder of air-filled tissue (Fig. 12).

In the same swamps, kiekie (Freycinetia baueriana var. banksii) often sprawls on the forest floor as well as climbing up tree trunks. In the former situation it forms what may be pneumatophores of an unusual type. They are slender and finger-like, and have a succession of tyre-like rings of white aeration tissue.

Finally the pneumatophores which catch the eye of many people in the Auckland region are those formed by the mangroves. These too are finger-like and project above the mud surface at low tide (Fig. 13).