tetr displacement of species in new zealand. 345 



Displacement and Increase. 



The blue-gum {Encalijptns Globulus''') in some localities shows 

 itself able to compete with the indigenous vegetation under special 

 circumstances. Seedlings germinating amongst manuka 4 ft. or 

 5 ft. in height will speedily overtop it. In several localities self- 

 sown plants are found by thousands, and, as a second generation 

 of naturalized plants is already to be found, there can be no doubt 

 that if not interfered with it would entirely alter the aspect of large 

 portions of the colony. E. piperita and K. rostrata appear to have 

 the same power of adapting themselves to new situations, although 

 perhaps not to an equal extent. 



The brush-wattle (Albizzia lophantha), a native of Western 

 Australia, is able to destroy the strongest vegetation in open 

 manuka country, as may be seen in numerous localities ; while 

 the tan- wattle {Acacia decurrens) and the silver- wattle {A. dealhata), 

 although much slower, are equally effective in the northern districts. 

 Another Australian plant, Hakca acicnlaris,\ according to Mr, 

 Cheeseman, " has established itself over several miles of open 

 manuka country at the foot of the Waitakerei Ranges, and is 

 increasing fast." Cobbett's locust-tree [llohinia Pseudacacia) iovms 

 large groves in the Waikato and other localities ; its lofty stature 

 and numerous suckers effectually prevent the growth of other vege- 

 tation. The well-known furze (Ulcx eurcpcBus), by its dense habit, 

 has killed tauhinu [Pomaderris plu/lici/uUa), manuka, &c., over large 

 areas, and is continually extending, whilst its near relative, the 

 broom [Ci/tisns scnparius), is no less troublesome. The injury to 

 pasturage caused by the sweetbriar (Piosa ruhiginosa) is unhappily 

 too well known to need special mention; but few are equally 

 familiar with its power of overcoming manuka and other shrubs of 

 similar habit. The dog-rose (R. canina) exerts the same influence 

 to a less extent in several districts of the South Island ; while 

 various forms of the European blackberry {Rubus J'ruticosus), &c., 

 by overgrowing their unfortunate competitors, deprive them of light 

 and air while absorbing their nourishment. 



The tutsan [Hypericum Androsanmin), although little more than 

 a strong-growing herb, less robust than any of the plants previously 

 mentioned, has become abundant in certain districts, and is able to 

 compete successfully with manuka, karamu, hange-hange, and other 

 shrubs of stronger growth. Its seeds appear to be disseminated by 

 birds. 



Two trees may be mentioned here, although they do not perhaps 

 displace the indigenous vegetation to any great extent. They never 

 perfect seeds or give off suckers, yet they have become self-diffused 

 along the margins of rivers and in similar situations to such an 

 extent as to impart a distinct character to the landscape in certain 

 districts. They are the weeping-willow (Sali.v babylonica), a native 

 of Northern China, and the crack-willow (S. frayilis), of Northern 



* Trans. N. Z. Inst. xvi. (1883), 383. 

 t Ibid. XV. (1882), 291. 

 Journal of Botany. — Vol. 34. [Aug. 1890.] 2 a 



