Cheeseman. — On Naturalized Plants of Auckland District. 273 



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

 they have gained a vigour of constitution and a faculty of adapting them- 

 selves to a great variety of conditions which enable them to readily over- 

 come plants that have not been so advantageously modified. 



This supposition will also throw some light on the curious fact that the 

 vast majority of our plants are of northern origin. It is now generally 

 admitted by geologists that the present continents are of immense antiquity, 

 and that there has been no great alteration in the relative proportions of 

 land and water during vast geological epochs. Mr. Darwin therefore argues 

 that as the northern hemisphere has probably always possessed the most 

 extensive continuous land area, so the wonderfully aggressive and colonizing 

 power of its plants at the present time is due to development where the 

 competition of species has been the most severe and long continued, owing 

 to the presence of facilities for natural migration. The plants of the com- 

 paratively isolated countries of the southern hemisphere have not been 

 subjected to the same degree of competition, and consequently could not be 

 so advantageously modified. 



It is difficult to predict the ultimate result of the struggle between the 

 invaders and the natives. Many naturalists believe that the foreign species 

 will succeed in displacing and exterminating a large section of the indigenous 

 flora. Mr. Travers, for instance, goes so far as to say* — " 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 displacing the indigenous fauna and 

 flora." Also, in his presidential address to the Wellington Philosophical 

 Society,! he states : — " Indeed, I have no doubt, from the present compara- 

 tive rarity of many plants which were formerly found in abundance in such 

 districts " (the sub-alpine portions of Nelson), " that in a few years our only 

 knowledge of them will be derived from the dried specimens in our her- 

 baria." On the other hand, Mr. Kirk, who has paid special attention to 

 the naturalization of plants in New Zealand, and whose views are there- 

 fore entitled to careful consideration, takes a much more hopeful view 

 of the future of the native flora. In a paper on the naturalized plants 

 of Port Nicholson,| he says : — " At length a turning-point is reached, the 

 invaders lose a portion of their vigour and become less encroaching, 

 while the indigenous plants find the struggle less severe and gradually 

 recover a portion of their lost ground, the result being the gradual 

 amalgamation of those kinds best adapted to hold their own in the 



* Trans. N.Z. Inst., vol. ii., p. 312. t Trans. N.Z. Inst., vol. iv., p. 359. 



+ Trans. N.Z. Inst., vol. x., p. 363. 

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