EUROPEAN OCCUPATION 527 



spreading in all directions, and in many places absolutely occupying 

 the ground they invaded. 



Many of these statements are unintentionally misleading. Thus 

 Hypochceris radicata, the most abundant and most widespread intro- 

 duced plant into New Zealand, can only assert itself in land grazed 

 over by cattle (it asserts itself in lawns), which eat out all the good 

 grasses and the clover, and leave the others. When sheep are intro- 

 duced the Cape-weed is itself quickly eaten out. Dr Cockayne is 

 very emphatic on the subject. He says : 



The often quoted stories of white clover being able to wipe out Phor- 

 mium tenax, of Salix Babylonica overcoming the water-cress, of Hypochceris 

 radicata displacing every other plant of excellent pastures in Nelson, are 

 without foundation. P. tenax has certainly been eradicated in many 

 places, and perhaps, in a sense, replaced by white clover, but not until 

 fire and feeding of stock had killed the plant. 



Dr Cockayne's reference is to a well-known passage in Darwinism'. 



A curious example of the struggle between plants has been communi- 

 cated to me by Mr John Enys, a resident of New Zealand. The English 

 water-cress grows so luxuriantly in that country as to completely choke up 

 the rivers, sometimes leading to disastrous floods, and necessitating great 

 outlay to keep the streams open. But a natural remedy has now been 

 found by planting willows on the banks. The roots of these trees penetrate 

 the bed of the stream in every direction, and the water-cress, unable to 

 obtain the requisite amount of nourishment, gradually disappears. 



Enys is partly right in this statement. I have recently noticed that 

 a species of Nitella, whether native or introduced I do not know, is 

 killing out the water-cress in some of the streams about Christchurch. 

 W. T. L. Travers, addressing the Wellington Philosophical Society 

 in 1871, in referring to the destruction of the native alpine and sub- 

 alpine flora of Nelson province said : 



Indeed I have no doubt, from the comparative rarity of many plants 

 which were formerly found in abundance in such districts, that in a few 

 years our only knowledge of them will be derived from the dried speci- 

 mens in our herbaria. 



In another place, quoted by Cheeseman, he stated: 



Such, in effect, is the activity with which the introduced plants are 

 doing their work, that I believe if every human being were at once removed 

 from the islands for even a limited number of years, looking at the matter 

 from a geological point of view, the introduced would succeed in dis- 

 placing the indigenous fauna and flora. 



I have no doubt that had Travers been living to-day he would 

 have completely reversed this judgment. The opinion of all botanists 

 in New Zealand to-day is that when the direct, or to a large extent 



