PREVALENCE OF INTRODUCED PLANTS EXAGGERATED. 147 
man as their potent ally, 66 per cent. of the species are rare or 
local, 40 per cent. being so rare as to be negligible, while merely 
34 per cent. can be classed as extremely common, common, or 
fairly common, these being taken together. 
In order to get a true estimate of the actual position of the plant 
invaders it is necessary to go into this matter of commonness and 
rarity from another standpoint—that of distribution with regard to 
soil and other conditions. Thus what is called “ waste ground ” 
—e.g., sides of roads, neglected building-sites, and rubbish-heaps— 
is occupied by about 355 species, some 255 of which are confined 
thereto. Add to the latter 60 species restricted to cultivated land, 
and it is plain that 60 per cent. of the invaders do not molest in 
the slightest degree the indigenous plant inhabitants. But even 
this estimate is far too low, for there are 102 pasture-plants which 
do not invade the natural unploughed lands. In short, there are 
probably only about 100 species which are established on land where 
the vegetation would be, in their absence, exposed to modification 
only by grazing, fire, and other causes due to the influence of man. 
The warfare, indeed, between the primitive New Zealand plant 
inhabitants and the alien invaders is waged almost entirely under 
conditions where man takes a hand, for, except for certain rock 
formations, stony-debris formations, and water formations, with but 
one trifling exception,* no truly primitive plant-formation is desecrated 
by a single foreign invader! This is a very different version of 
the story to that current in biological literature, where it is affirmed 
ad nauseam that the New Zealand vegetation is powerless when it 
comes into competition with the European plants, which by natural 
selection have become the very élite of the weed-world. 
In order to gauge the effect of the invasion by alien plants, first 
of all a classification of the different kinds of plant-associations 
which exist in New Zealand at the present time must be made. 
These associations may be divided into the following natural groups : 
(1) Primitive—i.e., the unchanged indigenous associations ; (2) modt- 
fied—i.e., where the primitive associations are altered to some 
* This is on the bed of the River Minchin just where it enters the little lake of 
the same name. Here the author in 1899 observed one plant of chickweed. With 
this exception the author has never seen an introduced plant in what still remains 
of primitive New Zealand, and he, for years past, has been making careful 
observations on this head, 
