blackberry (Rubus fruticosus, L.), &c., by overgrowing their unfortunate competitors, deprive them of light and air while absorbing their nourishment. The tutsan (Hypericum androsœnum, L.), 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 weepingwillow (Salix baby lonica), a native of Northern China, and the crack-willow (S. fragilis, L.), of Northern Europe. Twigs of these trees are easily detached, and are floated by the river to new situations, where they quickly take root and develope with rapidity, so that in certain situations navigation is impeded. Introduced Plants on Broken Soil. Introduced plants compete with indigenous species for the possession of any newly-loosened surface, and especially for waste land. The margins of newly-formed roads are speedily clothed with a dense growth of sheep's-cress, docks, thistles, Yorkshire-fog, and many others, mixed with the native piripiri (Accena sanguisorbœ, Vahl.), toad-grass (Juneus bufonius, L.), Danthonia semi-annularis (R. Br.), and when neglected form splendid nurseries for injurious insects and fungi. Crumbling places on hillsides in many localities are quickly covered with a strong and permanent growth of the blessed-thistle (Silybummarianum, Goertn.), which distributes vast quantities of seeds, and overcomes indigenous and introduced plants alike, forming continuous masses of variegated foliage in the early spring, but presenting a ragged and untidy appearance during the autumn and winter months. The common spearthistle (Cnicus lanceolatus, L.) furnishes a striking example of the ability of a plant to seize upon situations suitable for its growth; in many districts immediately after the bush is burnt off the entire area is overrun by this rapacious invader, which exhibits a dense luxuriant growth often 4ft. to 5ft. high, preventing the growth of grass, and forming an almost impenetrable mass. The growth becomes less luxuriant during the second season, so that the grass is able to make headway, and by the end of the fourth season only a few old thistles have retained sufficient vigour to reassert themselves. The so-called Californian thistle (C. arveensis, Curtis) is the