88 JOURNAL OF SCIENCE, - 
nent bore an abundant flora of south temperate forms, obtained 
probably trom South America, the nearest continental area. 
(3) The third mode of plant-dispersion alluded to is by means 
of ocean currents. This subject has also been carefully examined 
by Mr. Darwin, and the results of his interesting experiments are ~ 
detailed in ‘‘ The Origin ot Species,” and have been largely em- 
ployed by Wallace in accounting for the flora of oceanic islands, 
such as the Azores. I need not recapitulate these results here, 
but will merely point out that the length of time during which 
many seeds will float and retain their vitality, and also the proba- 
bilities of such seeds being carried to localities suitable for their 
germination, are probably much greater than popular idea would, 
assign to them. In former epochs, when there was a greater land 
extension, and perhaps a more temperate climate in the antarctic 
regions, this mode of distribution may have sufficed to introduce 
some species into New Zealand, but it appears somewhat im- 
probable that it still continues to act to any considerable extent. 
A correct knowledge of the oceanic currents which impinge on 
our coasts will alone enable us to torm an estimate of this means 
of plant immigration, and this intormation I do not possess. 
Having considered very briefly these modes of plant dispersal, 
and roticed the geographical distribution and relationships of 
those genera which have been effected chiefly by their modifica- 
tions of form, I would take a brief glance at the endemic torms 
which occur so abundantly in our islands. As these have probably 
all originated in or near the localities where they now exist, they 
ean only aid us in the solution of the present question by their 
affinities. 
Many of these affinities are very difficult to establish, but in 
the majority of cases where the relationship of our endemic species 
to the flora ot other countries is evident, it is tound that Australian 
forms greatly predominate. Long isolation, together with complete 
change in their environment, has probably served to modify many 
of the immigrants, so that their affinities have become obscured, 
and this has acted in many cases so effectually as to mask them 
altogether. Usually variation first appears in the habit of the 
plant, and we see this in the form of the foliage, &c., ot Ranunculus 
Lyallii, our coriaceous Veronicas, Olearias, Ligusticums, &e. The same 
change is seen in recently introduced plants, as in the common 
Watercress (Nasturtium officinale), which in New Zealand rivers 
shows a tendency to assume a very different habit from its European 
parent. Protection against some forms of insect enemies, probably 
Orthopterous, appears also to have played an effectual part in 
modifying the epidermal structures of many of our species, and 
may partly account for the prevalence of coriaceous-leaved and 
woolly plants, among the alpine species in particular. But we have 
little data here to go upon, and before passing on to the last part of 
this address, I will just point out a few peculiarities ot structure in 
our plants which are of interest and full of suggestiveness, 
One of these is the scarcity of spiny or prickly plants. As the 
function of spines and prickles is probably that ot defence against 
mammalian enemies, we can readily understand the paucity of such 
contrivances in our plants. Even the apparent exceptions go to 
prove the rule in nearly every case. Where such defensive modi- 
fications do occur, we notice that the plants are usually to be found 
