348 THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 



of species is certainly over five hundred, as already stated. Making 

 all fair allowance for the imperfection of the records for 1855 and 

 1869, it will be seen that naturalized species have increased with 

 great rapidity during the last fifty years. But it is not probable 

 that this rate can be maintained ; the number of encroaching species 

 suitable for a given habitat, after all, must be limited, and it may 

 well be that the limit for New Zealand, so far as introductions from 

 European countries are concerned, is very nearly reached. As 

 bearing upon this point, it may be remarked that, as many of the 

 naturalized plants of different countries are migrants from a com- 

 mon centre, a large proportion must necessarily be identical; for 

 instance, out of 243 species enumerated by Mr. C. Moore, F.L.S., 

 as naturalized in New South Wales, fully three-fourths are natu- 

 ralized in New Zealand also; the remainder, consisting chiefly 

 of plants from warmer countries, are not capable of becoming 

 naturalized here. Again, out of 103 species of plants recently 

 introduced with ballast from Buenos Ayres, eighty-six were already 

 naturalized here. 



The distribution of naturalized plants in the colony follows to a 

 very great extent the same lines as those of the indigenous flora : 

 the number of species decreases rapidly southward. Upwards of 

 four hundred and twenty species are found in the Auckland District, 

 but no other district in the colony contains so large a number; less 

 than three hundred species would be found in the Wellington 

 District. It must, however, be remembered that the climate of 

 Auckland is much more favourable to the naturalization of plants 

 from warm temperate climates than that of any other part of the 

 colony. A singular illustration of this has been recently given. 

 A large quantity of ballast taken on board at Buenos Ayres was 

 discharged at Wellington from a vessel loading for Europe. Over 

 a hundred species of plants made their appearance on the ballast 

 before the close of the second summer, the great majority being 

 plants already naturalized in the Auckland District ; twenty-seven 

 species, however, had not previously been observed in Wellington, 

 and of these seventeen species had not previously been seen in any 

 part of the colony. In all probability not more than two of these 

 will become naturalized — most likely only one. But had the ballast 

 been deposited on the light scoria soil of the Auckland isthmus 

 instead of on the stifl' Wellington clay, it is absolutely certain that 

 in the absence of interference fully one-third would have become 

 established— probably more. I will only add, as an additional 

 reason for not expecting so large an increase in the number of 

 introductions as formerly, that during the last fifteen years great 

 improvements have been made in cleaning garden-seeds, agricultural 

 seeds, and cereals, which will not only tend to reduce the number 

 of species likely to be introduced in the future, but to prevent the 

 yearly importation of certain species which at present are but 

 partially naturalized. Chiefly from this cause certain species, such 

 as Fumaria officinalis, Lepidium campcstre, Papaver Rhccas, GitJiaijo 

 se'jetiim, Scandix Pecten-veneris, are less plentiful in many districts 

 than they were twenty years ago. 



