Cockayne. — On Vegetation of Open Bay Islands. 373 



In one place where the ground is boggy are large quantities 

 of Carex ternaria* together with Hydrocotyle americana,1f but 

 where the ground is drier at this point is Muehlenbechia com- 

 plexa growing over Lepidium oleraceum and Asplenium obtu- 

 satum. 



Excepting in the immediate neighbourhood of the shore the 

 remainder of the island is occupied by a dense growth of " Mueh- 

 lenbechia scrub," at first mixed with Veronica elliptica, but 

 afterwards, towards and at the actual summit of the island, 

 it is almost pure Muehlenbechia. 



4. Origin of the Liane Formations.^ 

 That the Open Bay Islands have formed a part of the South 

 Island mainland at no very distant date, as stated above, there 

 can be no doubt : the shallowness of the sea, the glacial deposit 

 on the main island, and other facts connected with the general 

 geological history of New Zealand, which need not be cited here, 

 offer ample proof. 



The islands when forming part of the mainland would be 

 densely covered with an evergreen subtropical forest, as men- 

 tioned before, similar to that which occupies the whole coast of 

 south Westland at the present time, and which is very briefly 

 described at the beginning of this paper. In such a forest, 

 it may again be pointed out, Freycinetia banhsii is a most con- 

 spicuous feature, climbing the highest trees and in some places 

 spreading over the forest-floor. Muehlenbeclda adpressa, too, as 

 in nearly all New Zealand lowland forests, is by no means un- 

 common. With the separation of the Open Bay Islands from 

 the mainland the forest would be at first exposed to few de- 

 leterious influences, but as the area that it occupied became 

 gradually smaller and smaller, so would the forest be exposed 

 more and more to the furious north-west wind laden with sea- 

 spray, until, by slow degrees, those plants unable to endure 

 such conditions, such as most rain-forest hygrophytes, would 

 go to the wall, while those plants possessing a more xerophytic 

 structure would be better able to survive. Notwithstanding 

 that lianes are amongst the most highly specialised of forest 

 plants, their whole organization having been evolved by forest 

 conditions, they are usually more xerophytic than the trees 



* This also occurs in some low ground on the larger island in the 

 midst of " M uehlenbecki a- Veronica- Pteris scrub." 



t I am indebted to my friend Mr. D. Petrie, M.A., for the identifica- 

 tion of this species. 



% A preliminary account of this was given in a paper read by me at 

 the Dimedin meeting of the Australasian Association for the Advancement 

 of Science, and published in the Canterbury Agricultural and Pastoral 

 Association Journal, vol. vi., 1904, p. 7. 



