Ecological Botany.'] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



193 



aerial roots of the Metrosideros frequently arise from near the upper branching of 

 the tree. They may measure 3 cm., 4 cm., or even more in diameter. They pass 

 downwards along the trunk, often twining round it, and giving of! in many places 

 a network of considerable size, made up of slender lateral roots, which ramify 

 in the bryophyte mantle covering the bark. The main roots sometimes quite sur- 

 round the trunk, and may finally reach and even penetrate into the ground. Where 

 they are numerous, they closely overlie one another, looking not unlike liane-stems. 

 On some trunks the network of aerial roots may extend for many metres, and be 

 17 cm. or more in depth. It is plain that these aerial roots of M. lucida are not 



Flo. 4. — Intebior or the Rata Fokest, rhowino Pro*tbate Habit or Growth of Metrosideros lucida, Oajip Cove, 



Cabxley Harroub, Ai:cKi,ANn Island. 

 On the forest-floor the ferns lUecliniim durum and Asplevium obtusntiim. 



positively geotropic, or they would turn from the leaning trunk and descend verti- 

 cally to the ground, while much less would they, liane-like, coil round it. At the 

 same time there is a general positive geotropic tendency, as shown by the roots occa- 

 sionally penetrating the ground. They are undoubtedly in harmony with the moist 

 atmosphere, but are not an " adaptation," though, all the same, they must utilise 

 the abundant water of the moss mantle or liverwort cushions within which they 

 are stimulated to excessive branching, and so supply no inconsiderable amount of 

 moisture to the leaves, which will decidedly benefit during the abnormal transpira- 

 13— S. 



