need not be denied; and tlie otber, th a t sucb risings and sinkings are in active progress os er
large portions of the continents and islands of the southern hemisphere. I t is to the works of
LyeU* th a t I must refer for all the necessary data as to the influence of climate in dii’ecting the
migration of plants and animals, and for the evidence of the changes of climate being dependent on
geological change. In the ‘ Principles of Geology’ these laws are proved to be of universal application,
and amply illustrated by their being applied to tbe elucidation of difficult problems in geogra-
pliical distribution. I t folloAvs from wbat is there shown, th a t a change in the relative positions of sea
and land has occurred to snch an extent since the creation of still existing species, th a t we have no
right to assume th a t the plants and animals of two given areas, how^ever isolated by ocean, may not
have migrated over pre-existing laud between them. This was illustrated by an examination of
the natural history of Sicily (where land-shells, still existing in Italy, and which could not have
crossed the Straits of Messina, are found imbedded on tbe flanks of E tn a high above the sea-level),
regarding whicli Sir Charles LyeU states th a t most of the plants and animals of th a t island are older
th an the mountains, plains, and rii’ers they now inhabitt*
I t was reserved for Professor Edward Forbes, one of tbe most accomplished naturalists of his
day, to extend and enlarge these views, and to iUustrate by thefr means the natural history of an
extensive a re a ; which he did by applying a profound knowledge of geology and natm-al history to
the materials he had coUected during his arduous surveys of many of the shores of Europe and the
IMediterranean. The result has been the enunciation of a theory, fr'om which it follows th a t the
greater part, if not all, of the animals and plants of the British Islands have immigrated at different
periods, under very different cUmatic conditions; and th a t aU have survived immense changes
in the configuration of the land and seas of Northern Europe. The arguments which support
this theory are based upon evidence derived from Zoology and Geologyl, and they receive addiimportant
observations on his own islands. The fact of this accomplished Naturalist and Geologist having preceded
me in the investigation of the Natural History of the Southern Ocean, has materially influenced and greatly
furthered my progress; and I feel it the more necessaiy to mention this here, because IMr. Darwin not only directed my
earliest studies in the subjects of the distribution and variation of species, but has discussed with me all the arguments,
and drawn my attention to many of tbe facts which I have endeavoured to illustrate in this Essay. I know
of no other way in which I can acknowledge the extent of ray obligation to him, thau by adding that I should never
have taken up the subject in its present form, but for the advantages I have derived from his friendship and
encouragement.
* To Sir Charles Lyell’s works, indeed, I am indebted for the enunciation of those principles that are essential
to the progress of every naturalist and geologist; those, I mean, that affect the creation and extraction, dispersion
and subsequent isolation of organic beings; and though botanists still differ in opinion as to the views he
entertains on the most speculative of subjects (the origin and permanence of species), there is, I think, but one as
to the soundness and originality of his observations on all that relates to the strict dependence of organic beings on
physical conditions in the state of the earth’s surface. I feel that I cannot over-estimate the labours of this great
philosopher, when I reflect that without them the science of geographical distribution would have been with me
little beyond a tabulation of important facts; and that I am indebted to them, not only for having given a direction
to my studies in this department, but for an example of admirable reasoning on the facts he has collected regarding
the distribution of plants and animals. I have no hesitation in recommending the ‘ Principles of Geology’ to the
New Zealand student of Nature, as the most important work he can study.
T See the Principles of Geology, ed. 9. p. 702, and Address to the Geological Society of London by the President
(Leonard Horner, Esq.), in 1847, p. 66.
X For the contents of the Essay itself, I must refer to the Records of the Geological Sui’vey of Great Britain,
vol. i. p. 336. This is the most original and able essay that has ever appeared ou this subject, and though I cannot
tional weight from the faet th a t the distribotion of British plants is in accordanee with its prineipal
features*.
Tlie geograpliical distribution of B ritisli plants has been the subject of the most rigorous investigation
by one of our ablest British botanists, Mr. H. C. Watson, who first drew a ttention to the
\-arious botanical elements of which the flora is composed, and grouped the species into botanical
provinces. These provinces were intended for “ shoving the areas of plants, as facts in nature independent
of all theoretical explanations and reasons.’’ (Cybelc 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 iUustration of his views of the original introduction of plants into the British Islands, proceeds to
show th a t their migration took place at different periods, contemporai’y of course with the connection
by land of each botanical region of B ritain with th a t part of the continent which presents a similar
association of plants.
To extend a theoretical application of these views to th e New Zealand Flora, it is necessary to
assume th a t there was at one time a land communication by which th e ChUiau plants were in te rchanged
; th a t a t the same or auother epoch the A ustralian, at a third the A ntarctic, and a t a fourth the
Pacific floras were added to the assemblage. I t is not necessaiy to suppose th a t for this interchange
there was a continuous connection between any two of these localities, for an intermediate land,
peopled r i t h some or all of the plants common to both, may have existed between New Zealand and
Chili when n either of these countries was as yet above w ater t- To account, however, for the A ntarctic
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 cUmate of the intermediate area
must necessarily have prevented it. B ut changes of relation between sea and land induce clianges of
climate, and the presence of a large continent connecting the Antarctic islands would, under certain
cfrcumstances, render New Zealand as cold as Britain was during the glacial epoch. Sir C. Lyell
first demonstrated this, and showed what such conditions should b e ; and by consulting the ‘ P rin ciples
of Geology,’ my reader will understand how such a climate would reign in the latitude of
New Zealand, as th a t 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 application,
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 fiora, 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, aud land,
which auiinals do; the cause is evident, for the bones of quadrupeds, shells of mollusca, and hard parts of mauy
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 arc.
f lilis 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 cliange of the river channel fills up that
between the islet and the opposite shore, to whicli it hence becomes a peninsula, peopled by mangroves, whose
parents grew on the opposite hank. Here, be it remarked, no subsidence is required, such as must have operated
in tlie assumed isolation of New Zealand.