216 NEW ZEALAND PLANTS. 
author, though reluctantly, declares himself in favour of great land- 
extension. Moreover, speaking as one who for years has studied 
plants as they grow wild, the extreme difficulty of a species being 
able to establish itself in a new land, especially if a stable plant- 
covering be already present, must never be lost sight of. In support 
of this statement there is the remarkable fact, already emphasized in 
Chapter X but not yet sufficiently known to biological geographers, 
that in New Zealand, notwithstanding the host of introduced plants 
(more than 520 species), many of them the most aggressive weeds 
of the Old World, which in New Zealand thrive amazingly, none 
are established in any actually virgin plant-association, aquatic and 
some rock associations excepted. That is, that in those places where 
man, grazing-animals, and fire have not been, notwithstanding wind- 
transit of millions of seeds for more than one hundred years and 
constant carriage of such by both indigenous and introduced birds, 
primitive New Zealand still exists. 
The view, then, which may be taken is that New Zealand 
possessed a primitive flora of her own—the Palaeozelandic— which 
probably formed part of that of a wide land-area, perhaps united 
to Antarctica; that at an early date the ancestors of the present 
subantarcltic element came in; that later there was an invasion of 
tropical Malayan species, and also perhaps of the Australian element, 
these happenings occurring during a great northern land-extension 
by way of New Caledonia and the New Hebrides. The reason 
for assigning an early date to the subantarctic colonization is that 
the southern-beech (Nothofagus), a typical subantarctic genus, still 
maintains a few isolated outposts in the North Auckland Botanical 
District, while elsewhere it is, generally speaking, absent in the low- 
land belt, or, if present, confined to stations unsuitable for tropical 
rain-forest. According to this view, a “ struggle’ between the sub- 
antarctic and tropical elements is postulated, through which many 
species of the former were driven into the mountains or the more 
inhospitable lowland stations. Or, on the other hand, the struggle 
may have taken place much later, after a cold period, and the 
present arrangement, even in the North Island, be post-glacial. Then, 
perhaps in mid-Tertiary times, New Zealand, through depression of 
the land-surface, was reduced—so geologists assert—to a few small 
islands, the climate at the same time being much warmer than now. 
Under such conditions many subantarctic species would go to the 
