T. KiKK. — Displacement of Species in Neio Zealand. 19 



cattle and horses to graze upon it ; this increases the vigour of 

 the grass, while the native plants have to contend against the 

 consolidation of the soil caused by the trampling of heavy 

 stock; this further invigorates the interlopers, and enables them . 

 to continually extend their area by giving off new shoots from 

 the base, and occasionally by producing seed. x*\.s their growth 

 increases the vigour of the toitoi perceptibly diminishes, and 

 its ultimate extinction is certam, although the process may 

 occupy several years. The occasional replacement of manuka 

 {Leptospermuvi scoparium, Forst.) and other shrubs by grasses 

 is still more striking. Sir George Grey drew my attention to 

 this fact on my first visit to the Kawau, in 1864, where the 

 naturalised Sporoholus indicus (E. Br.) was spreading amongst 

 manuka from 5ft. to 8ft. in height, forming a sward which, 

 notwithstanding the coarse character of the herbage, was 

 closely cropped by stock, to the benefit of the grass and 

 injury of the shrub. But even this is less surprising than an 

 instance of a similar kind at the Bay of Islands, where 

 a delicate and slender naturalised love -grass {Eragrostis 

 brownii, Nees) is exerting the same influence on a large 

 scale. Introduced grasses exhibit similar action upon many 

 native grasses in all parts of the colony and at all elevations. 

 In the Upper Waimakariri, Triodia exigua (T. Kirk) often 

 forms a compact and extensive sward, which is usually able 

 to resist aggression on the part of its indigenous allies, but if 

 a single grain of rye-grass {Lolium pcrenne, L.) or meadow- 

 gi-ass [Poa pratensis, L.) falls amongst it and germinates, the 

 continuity of the sward is speedily interrupted and a process 

 of disintegration sets in which ultimately destroys the whole, 

 or reduces it to small tufts or patches. The same result is 

 often exhibited at the expense of more robust plants. The 

 gradual replacement of the Spaniard {Acipliijlla colensoi, 

 Hook, f.) by self-sown pasturage-plants is most remarkable. 

 It seems next to impossible that the large rigid bayonet-like 

 leaf-segments which surround the base of the flower-stem in 

 this strange plant should be injured by a growth of soft 

 herbs, however compact : yet, so it is : dense masses of the 

 Spaniard actually impenetrable to stock of any kind are de- 

 stroyed by this simple agency. When once its vigour is 

 reduced the ultimate destruction of the Spaniard is simply a 

 matter of time. The common spear -grass {A. sqiiarrosa, 

 Forst.) is often displaced in the same way. 



Amalgamation op Native and Introduced Plants. 



But there is another aspect to the case ; for, however 



remarkable it may seem after the statements that have just 



been made, certain slender native grasses, of great value on 



•.account of their nutritive qualities, are able to resist the 



