EUROPEAN OCCUPATION 531 



settlers to make room for their cultivations, or in the construction of 

 roads, or in the cutting down of the forests for timber, etc.; second, the 

 introduction of sheep, cattle and horses, and their spread over the greater 

 part of the country ; third, the practice, now very generally followed, of 

 burning off the vegetation in the open districts at regular intervals. 



If the above facts are duly considered there will not be so much cause 

 for wonder in the introduction and rapid spread of so many foreign plants. 

 For instance, it might be expected that the weeds of our corn-fields and 

 pasture — ^which now form such an important and conspicuous element 

 in the naturalised Flora — would be almost wholly composed of introduc- 

 tions from abroad. The native Flora possessed few plants suitable for the 

 places they have taken, and these few could hardly compete with a chance 

 of success against species that have from time immemorial occupied the 

 cultivations of man, and whose best adapted varieties have been rigorously 

 selected. The introduced weeds flourish and multiply because they have 

 an environment suited to them and to which they have been modified ; the 

 native ones fail because the conditions have become altogether different 

 to those they had been accustomed to. 



Similarly it was to be expected that foreign plants would in some 

 degree displace the indigenous ones in districts grazed over but not actually 

 cultivated. Many native species will not bear repeated cropping, and soon 

 decrease in numbers when cattle and sheep are brought in. Their places 

 will, therefore, be taken by plants that are indifferent to this, or escape 

 by reason of being unpalatable .... At the same time it must be remem- 

 bered that any native plants possessing similar advantages would also 

 increase; and in many cases this has actually taken place. The spread of 

 such indigenous plants as Poa australis and Discaria in the river valleys 

 in the interior of Nelson and Canterbury, of Cassinia on the shores of Cook 

 Straits; and of some grasses (as Danthonia semiannularis and Microlcena 

 stipoides) in Auckland, are well-known examples, and it would be easy 

 to enumerate more. 



But although we may safely credit the changed conditions of plant life 

 with being a powerful reason for the spread of naturalised plants in New 

 Zealand, it is impossible to consider it as the sole explanation. For we 

 find that not a few species have penetrated into localities where cultivation 

 and cattle are alike unknown, and where man himself is a rare visitant ; 

 where in fact, the conditions are still unchanged. This is the most interesting 

 part of the subject, for it proves conclusively, as remarked by Mr Darwin, 

 that the indigenous plants of any district are not necessarily those best 

 suited for it. In most cases it is impossible to assign any obvious reason 

 for the fact that these intruders should be able to thrust on one side the 

 native vegetation; but it is significant that all, or nearly all, are common 

 and widely distributed in their native countries, in short, are predominant 

 species; and that they have followed almost everywhere the footsteps of 

 man, being as extensively naturalised in many other countries as in New 

 Zealand. We may, therefore, suppose that by long-continued competition 

 with other species, in different localities and in different climates, they 

 have gained a vigour of constitution and a faculty of adapting themselves 

 to a great variety of conditions which enable them to readily overcome 

 plants that have not been so advantageously modified. 



34—2 



