THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 3i3 



but tlie fact remains. Seeds of rye-grass, meadow-grass, white or 

 red clover, &c., germinate by the side of the coarse-growing toitoi, 

 and gradually abstract the moisture which it has been enjoying 

 undisturbed ; the growth of the sedge becomes less vigorous, while 

 that of the interlopers is more robust. The result would not be in 

 doubt were the jolants now left undisturbed, but an overpowering 

 force comes to the help of the invaders — the rich grass attracts 

 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 con- 

 tinually extend their area by giving off new shoots from the base, 

 and occasionally by producing seed. As their groAvth increases the 

 vigour of the toitoi perceptibly diminishes, and its ultimate ex- 

 tinction is certain, although the process may occupy several years. 

 The occasional replacement of manuka (Leptospermum scopmrium) 

 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 naturalized Sporoholus indicus was spreading 

 amongst manuka from 5 ft. to 8 ft. 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 

 naturalized love-grass [Eragrostis Broicnii) 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 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 (Loliuvi perenv.e) or meadow-grass [Poa pratensis) 

 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 [Aciphylla Colensoi) 

 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 destroyed 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. squarrosa) is often displaced 

 in the same way. 



Amalgamation of 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 invaders, and ultimately become 



