342 THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 



In a few localities goats have been equally destructive. I have been 

 informed that the tainui [Pomaderris apetala) has been completely 

 destroyed at Kawhia, where it was formerly abundant, and is now 

 restricted to the south head of the Mokau River and the Chatham 

 Islands. 



Injury caused by Rats. 



Some plants formerly plentiful have been to a large extent 

 destroyed by the pig and the rat, as the curious orchid, Gastrodia 

 Cunniniihaiini, the tubers of which are highly nutritious. This 

 plant has become very rare in districts where the black rat is 

 plentiful. On one occasion, in 1874, I found three remarkably fine 

 specimens, quite 2 ft. in height, with tubers G in. or 7 in. in length, 

 and placed them in what seemed a safe place in a hut at Omaha, 

 but during the night they were carried off by the rodents, Both 

 the pig and the grey rat feed upon the fleshy roots of the larger 

 Umbellifercc. 



Injury caused by Insects. 



A small native beetle, which I have not been able to identify, 

 has greatly reduced many species of Cehnimi and other CompositcB 

 by depositing its eggs on the disc florets, where they quickly enter 

 the larval state, and destroy the carpel before it reaches maturity. 

 The great increase of this insect during recent years is doubtless 

 caused by the frequent burning of the surface vegetation, and con- 

 sequent destruction of the lizards and predatory insects which kept 

 the beetle in check. Several species of Diptera which are equally 

 destructive doubtless owe their rapid increase of late years to the 

 same cause. 



Displacement by Introduced Plants. 



In many instances a comparatively few species of naturalized 

 plants have taken possession of sea-beaches, completely displacing 

 the original vegetation by their more vigorous growth and their 

 vast numbers — simply crowding it out by depriving it of air and 

 light, and to a large extent absorbing its nourishment. This may 

 be seen, for instance, south of the township of Kaikoura, where a 

 broad stretch of land at the water-margin is wholly given up to 

 such weedy plants as the common brome-grass {Bromus sterUis), 

 docks (liuinex ohtusifolius, E. crispus, &c.), fleabane {Eriijeron cana- 

 densis), catchfly {Silene anglica), Yorkshire-fog [Holms lanatus), 

 and others, perchance intermixed with one or two native plants of 

 similar habit. Here the displacement is almost complete, the 

 original littoral vegetation having been driven to a few peculiarly 

 favoured spots, where it maintains a somewhat precarious existence. 



The displacement of the New Zealand flax {Fhonnium tenax), 

 the coarse sedge known as toe-toe-whatu-manu {Cijpenis iistulatiis), 

 and the common fern {Pteris esculenta), by European grasses and 

 clovers is so striking that it has arrested the attention of the 

 natives, and, indeed, it is calculated to attract the notice of even a 

 casual observer, for the indigenous species mentioned are so robust 

 that the mere idea of their being overcome in the struggle for 

 existence by such plants as clovers and grasses seems almost absurd : 



