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INTRODUCTORY ESSAY. XXIII 
tional weight from the fact that the distribution of British plants is in accordance with its principal 
features*, 
The geographical distribution of British plants has been the subject of the most rigorous inves- 
tigation by one of our ablest British botanists, Mr. H. C. Watson, who first drew attention to the 
various botanical elements of which the flora is composed, and grouped the species into botanical 
provinces. These provinces were intended for “showing the areas of plants, as facts in nature inde- 
pendent of all theoretical explanations and reasons." (Cybele Britannica, vol. i. p. 18.) An inspection 
of them shows the relations borne by the plants of England to those of certain parts of Europe and 
of the Arctic regions; and Professor Forbes, applying a modification of these botanical provinces to 
the illustration of his views of the original introduction of plants into the British Islands, proceeds to 
show that their migration took place at different periods, contemporary of course with the connection 
by land of each botanical region of Britain with that part of the continent which presents a similar 
association of plants. 
To extend a theoretical application of these views to the New Zealand Flora, it is necessary to 
assume that there was at one time a land communication by which the Chilian plants were inter- 
changed; that at the same or another epoch the Australian, at a third the Antarctic, and at a fourth the 
Pacific floras were added to the assemblage. It is not necessary to suppose that for this interchange 
there was a continuous connection between any two of these localities, for an intermediate land, 
peopled with some or all of the plants common to both, may have existed between New Zealand and 
Chili when neither of these countries was as yet above watert. To account, however, for the Antarctic 
plants on the lofty mountains, a new set of influences is demanded; no land connection between 
these islands and New Zealand could have effected this, for the climate of the intermediate area 
must necessarily have prevented it. But changes of relation between sea and land induce changes of 
climate, and the presence of a large continent connecting the Antarctic islands would, under certain 
circumstances, render New Zealand as cold as Britain was during the glacial epoch. Sir C. Lyell 
first demonstrated this, and showed what such conditions should be; and by consulting the * Prin- 
ciples of Geology,’ my reader will understand how such a climate would reign in the latitude of 
New Zealand, as that its flora should consist of what are now Antarctic forms of vegetation. The 
subscribe to all its botanical details, I consider that the mode of reasoning adopted is sound, and of universal appli- 
cation. What I dissent from most strongly is, the origin of the gulf-weed, the peopling of Scotch mountains by 
iceberg transport of seeds, and the too great stress laid upon the west Irish flora, whose peculiarities appear to me 
to be considerably over-estimated. 
* It may be well to state to the New Zealand student, that there are no reasons to suppose that Botany can 
ever be expected to give that direct proof of plants having survived geological changes of climate, sea, and land, 
which animals do; the cause is evident, for the bones of quadrupeds, shells of mollusca, and hard parts of many 
animals, afford an abundant. means of specific identification, and such are preserved when the animals perish. In 
plants the case is widely different: their perishable organs of reproduction, which alone are available for systematic 
purposes, are seldom imbedded, even when other parts of the plants are. 
T This disappearance of old land, and the migration of its flora and fauna to new, may be illustrated to a 
certain extent by the delta of any New Zealand river. A mud-bank on one shore, covered with mangroves, advances 
across the channel, the mangroves growing on the new land as it forms. ‘The current changes, and the end of the 
bank (with its mangroves) is cut off, and becomes an island: another change of the river channel fills up that 
between the islet and the opposite shore, to which it hence becomes a peninsula, peopled by mangroves, whose 
parents grew on the opposite bank. Here, be it remarked, no subsidence is required, such as must have operated 
in the assumed isolation of New Zealand. 
