Page:Journal of botany, British and foreign, Volume 34 (1896).djvu/373

 the displacement of species in new zealand. 345 Displacement and Increase. The blue-gum (Eucalyptus 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 E. 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, Hakea acicularis, 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 (Robinia Pseudacacia) foims 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 (Ulex eurcpcBus), by its dense habit, has killed tauhinu (Pomaderris phi/lici/olia), manuka, &c., over large areas, and is continually extending, whilst its near relative, the broom (Cytisiis scojmrius), is no less troublesome. The injury to pasturage caused by the sweetbriar (Eosa rubiginosa) 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 fruticosus), &c., by overgrowing their unfortunate competitors, deprive them of light and air while absorbing their nourishment. The tutsan [Hypericum Androsamum), 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 (Salix babylonica), a native of Northern China, and the crack-willow {S. fragilis), of Northern t Ibid. XV. (1882), 291. Journal of Botany. — Vol. 34. [Aug. 1896.] 2 a
 * Trans. N. Z. Inst. xvi. (1883), 883.