Cockayne. — On Vegetation of Open Bay Islands. 375 



we are unable to estimate, and that where the two plants are 

 associated the latter is being slowly eradicated. Such silent 

 conflicts, of which we know nothing, must be constantly waged 

 between plants which apparently are equally well equipped for 

 the struggle. 



5. Summary. 



(1.) The Open Bay Islands are two small islets three nautical 

 miles from the coast of south Westland, to which they must 

 have been joined at no very distant date. 



(2.) Their most important vegetation consists of thickets 

 formed by the lianes Muehlenbeckia adpressa and Freycinetia 

 banksii. 



(3.) On the larger island Freycinetia is dominant, associated 

 with Muehl. adpressa, Calystegia tuguriorum, and Pteris incisa, 

 or it may be almost pure. 



(4.) On the smaller island there is no Freycinetia, but the 

 thicket consists of Muehlenbeckia adpressa associated with Ve- 

 ronica elliptica and Pteris incisa, or the Muehlenbeckia may be 

 pure. 



(5.) The form of Veronica elliptica is distinct from any found 

 elsewhere in the New Zealand biological region. Probably this 

 form may reproduce itself " true " from seed. 



(6.) Owing to the heavy rainfall there is in places a luxuriair 

 rock-vegetation. 



(7.) In certain places not occupied by " liane scrub " there is 

 a well-marked zonal distribution of certain New Zealand coastal 

 plants. 



(8.) When attached to the mainland the present islands must 

 have been occupied by subtropical evergreen rain-forest similar 

 to that now existine on the adjacent coast. After separation, 

 as the area of the islands became smaller and smaller, and the 

 climatic conditions more and more severe, only those plants 

 specially adapted to such conditions could survive, and of these 

 certain of the lianes, although most highly specialised forest 

 plants, are the most suitable. 



(9.) On the smaller island the dominant liane is Muehlenbeckia 

 adpressa ; and FreycineUa banksii, the dominant liane of the 

 larger island, is altogether wanting. 



6. List op Plants (Spermaphyta and Pteridophyta) 

 observed on the open bay islands. 



Filices. 

 Asplenium obtusatum. Forst. 

 Lomaria dura, Moore. 

 Pteris incisa, Thunb. 



