22 Transactions. — Miscellaneous. 



blackberry {Biihus fmticosus, L.), &c., by overgrowilig their 

 unfortunate competitors, deprive them of light and air while 

 absorbing their nourishment. 



The tutsan {Hy'pericum anclroscEnum, L.), although little 

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

 plants previously mentioned, has become abundant in cer- 

 tain 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 hahylonica), 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. 



Intkoduced Plants on Bkoken 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 sancjuisorbce, Vahl.), toad-grass {Juncus bufonius, L.), 

 Danthonia semi-annnlaris (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 

 {Silyhum marianum, Goertn.), which distributes vast quanti- 

 ties 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 spear- 

 thistle (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 growtli becomes less luxuriant dur- 

 ing the second season, so that the grass is able to make head- 

 way, 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 [G. arvensis, Curtis) is the 



