234 SUBANTARCTIC ISLANDS OF NEW ZEALAND. [Ecological Botany. 



destroyed again and again, always to quickly reinstate itself. Even the forest can 

 have no chance of renewal when once the old trees die, so long as the birds are 

 present. 



On certain of the islands albatroses or moUymawks are extremely abundant. 

 I had especial opportunity of noting their effect on the vegetation of Disappoint- 

 ment and Antipodes Islands, but it may well be concluded that on all islands 

 where extensive bird-colonies exist analogous results must follow. 



Disappointment Island, as has been seen, is closely covered with a brown tussock 

 meadow, or else a formation of the large-leaved herbs similar to Fairchild's Garden, 

 but with fewer members. Also in many places are areas, large or small, of a vivid 

 green. The tussock meadow is dotted at a certain season of the year for acre upon 

 acre with the nesting mollymawks, which, when seen from the sea, look like in- 

 numerable great white flowers amongst the brown tussocks. Each of these birds 

 sits on its cheese-shaped nest hatching the egg during November and part of De- 

 cember. Finally, the chick, fed for many months by the parent bird, remaining all 

 this long time upon the nest, leaves it at last, and, walking for some weeks longer 

 in a narrow circle roimd the nest, quite kills out the vegetation. Thus in course of 

 time, on this island, on the Antipodes, and elsewhere where albatroses are numerous, 

 arise many bare patches, and these, as there is no longer shelter for the birds, are 

 abandoned, a piece of untouched tussock meadow being invaded by the birds and 

 the bare ground being available for reoccupation by plants. Various stages of such 

 new settlements may be seen, and every phase is present, from quite bare ground 

 to rejuvenated tussock meadow. In all probability, owing to the smallness of the 

 island and the immense number of birds, a constant change must be going on, and 

 the whole of the vegetation has been destroyed and reconstructed again and again. 



The first plant to appear is Acaena Sanguisorbae var. antarclica, which forms 

 sheets over the ground and gives the distinguishing pale-green colour noted above. 

 Then there will soon be abundance of a species of gentian, its spreading stems making 

 a glossy dark-green mat. Here and there will be small plants of the dark-green 

 Blechnum durum, small straggling Veronica Benthami, small mats of bright but rather 

 pale-green EfUobium confertifolium, a few dark-green plants of Polystichum vestitum, 

 and, growing through the mats of Acaena, a little Bulbinella Rossii, and perhaps some 

 Stilbocarpa polaris here and there. But easily dominant, and at a distance the sole 

 plant apparently, is the Acaena. Ultimately, such a piece of regenerated vegetation 

 as described above, and which represents quite a late stage, will be in process of 

 occupation by tussocks of Poa litorosa, which it is easy to see will, as they grow up, 

 destroy, or at any rate thin out, the present plants ; but the Acaena will finally, 

 liane-Iike, in many cases cUmb over the tussock, gain the light, and preserve itself 

 from destruction, a proceeding most common, too, on Antipodes Island. 



This regeneration of the meadow — a quite natural process depending upon the 

 presence of the sea-birds — is especially interesting, in that the Acaena — a plant of 

 Umited distribution in the original formation, where it is altogether kept in check — 

 becomes at once what is virtually a " weed " upon new ground being prepared ; 

 in other words, we have in this wild plant a potential weed (see Cockayne, " New 

 Zealand Indigenous Plants as Weeds"; Journ. Canterbury A. and P. Assoc, vol. 

 vii, p. 115; 1905), 



