■ t
XXii FLOILV OF NEW ZEALAND.
need n o t b e d e n i e d ; a n d tb e o th e r, th a t su ch ris in g s a n d s in k in g s a re in ac tiv e progi’ess over
la rg e p o rtio n s o f th e c o n tin e n ts a n d is lan d s o f th e s o u th e rn h em isp h e re . I t is to th e works o f
L y e ll* th a t I m u s t re fe r fo r a ll th e n e c e ssa ry d a ta as to th e in flu en c e o f c hm a te in dii’e c tin g th e
m ig ra tio n o f p la n ts a n d an im a ls, a n d fo r th e evidence o f th e ch an g e s o f c lim a te b e in g d ep e n d e n t on
g eological ch an g e . I n th e ' P rin c ip le s o f G eo lo g y ’ th e se laAvs a re p ro v ed to b e o f u n iv e rsa l ap p lica
tio n , a n d am p ly illu s tr a te d b y th e ir b e in g ap p lied to th e e lu c id a tio n o f difficult p ro b lem s in g eo g ra p
h ic a l d is trib u tio n . I t folloAvs from Avhat is th e r e shown, th a t a ch a n g e in th e re la tiv e p o sitio n s o f sea
a n d la n d h a s o c c u rre d to su ch a n e x te n t s in c e th e c re a tio n o f s till ex istin g species, th a t we h av e no
rig h t to a ssume th a t th e p la n ts a n d an im a ls o f tw o giv en area s, howev er iso la te d b y ocean, m a y n o t
h av e m ig ra te d over p re -e x is tin g la n d b e tw e en th em . T h is was illu s tr a te d b y an ex am in a tio n o f
th e n a tu r a l h is to ry o f S icily (where la n d -sh e lls , s till ex istin g in I ta ly , a n d w h ich co u ld n o t have
cro ssed th e S tr a its o f M e ssin a , a re fo u n d im b ed d ed o n th e flanks o f E tn a h ig h above th e sea-leA^el),
re g a rd in g w h ich S ir C h a rle s LyeU s ta te s th a t m o s t o f th e p la n ts a n d an im a ls o f th a t is la n d a re o ld e r
th a n th e m o u n ta in s , p la in s , a n d riA'ers th e y now in h a b itf .
I t was re serv ed fo r P ro fe s so r E dw a rd F o rb e s , o n e o f th e m o s t ac comp lish ed n a tu r a lis ts o f his
d ay , to ex ten d a u d enlai’ge th e se views, a n d to iU u s tra te b y th e ir m e an s th e n a tu r a l h is to ry o f an
ex ten siv e a r e a ; w h ich h e d id b y ap p ly in g a p ro fo im d k n ow led g e o f geology an d n a tu r a l h is to ry to
th e m a te ria ls h e h a d coUected d u rin g h is a rd u o u s su rv ey s o f m a n y o f th e sh o res o f E u ro p e a n d th e
N led ite rran e an . T h e re s u lt h a s b e e n th e e n u n c ia tio n o f a th e o ry , from Avhich i t follows th a t th e
g re a te r p a rt, i f n o t a ll, o f th e an im a ls a n d p la n ts o f th e B ritis h Is la n d s h av e im m ig ra te d a t d iffe
re n t p erio d s, u n d e r v e ry d iffe ren t c lim a tic c o n d itio n s ; an d th a t aU h av e su rv iv ed im m en se changes
in th e c o n fig u ra tio n o f th e la n d a n d seas o f N o r th e r n E u ro p e . T h e ai’g um e n ts w h ich su p p o rt
th is th e o ry a re b a sed u p o n evidence d e riv ed from Zoology a n d Geo lo g y J , a n d th e y rece ive ad d iimportant
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 gi-eatly
furthered my progress; and I feel it the more necessary to mention this here, because Mr. Darwin not only directed my
earliest studies in the subjects of the distribution and variation of species, but has discussed with me ail the arguments,
and drawn my attention to many of the 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, than 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 extinction, 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 tbe ‘ 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 Survey of Great Britain,
vol. i. p. 336. This is the most original and able essay that has ever appeared on this subject, and though I cannot
tio n a l w e ig h t from th e fa c t th a t th e d is trib u tio n o f B ritis h p la n ts is in a c co rd an c e w ith its p rin c ip a l
fe a tu re s* .
T h e g eo g rap h ic a l d is tr ib u tio n o f B r itis h p la n ts h a s b e e n th e su b je c t o f th e m o s t rig o ro u s in v e s tig
a tio n b y o n e o f o u r a b le s t B r itis h b o ta n is ts , M r. I I . C. W a ts o n , who firs t d rew a t te n t io n to th e
vario u s b o ta n ic a l e lem en ts o f w h ich th e flo ra is composed, a n d g ro u p e d th e species in to b o ta n ic a l
provinces. Th e se p ro v in c es were in te n d e d fo r " sh owin g th e a re a s o f p la n ts , as fa c ts in n a tu r e in d e p
en d e n t o f a ll th e o re tic a l ex p lan a tio n s a n d re a so n s .” (Cybele B rita n n ic a , vol. i. p. 18.) A n in sp e c tio n
o f th em shows th e re la tio n s b o rn e b y th e p la n ts o f E n g la n d to th o s e o f c e rta in p a r ts o f E u ro p e an d
o f th e A rc tic r e g io n s ; a n d P ro fe s so r F o rh e s , ap p ly in g a mo d ific a tio n o f th e s e b o ta n ic a l p ro v in c e s to
th e illu s tra tio n o f h is views o f th e o rig in a l in tro d u c tio n o f p la n ts in to th e B r itis h Is la n d s , p ro c e ed s to
show th a t th e ir m ig ra tio n to o k p la ce a t d iffe ren t p e rio d s, c o n tem p o ra ry o f co u rse w ith th e co n n e c tio n
b y la n d o f e a ch b o ta n ic a l re g io n o f B r it a in w ith th a t p a r t o f th e c o n tin e n t w h ich p re s e n ts a sim ila r
asso cia tio n o f p la n ts .
To ex ten d a th e o re tic a l a p p lic a tio n o f th e s e views to th e N cav Z e a la n d F lo ra , i t is n e c e ss a ry to
as sum e th a t th e r e Avas a t o n e tim e a la n d com m u n ic a tio n b y w h ic h th e C h ilian p la n ts w e re in t e r ch
a n g ed ; th a t a t th e same o r a n o th e r epoch th e A u s tra lia n , a t a th i r d th e A n ta r c tic , an d a t a fo u r th th e
Pacific floras w e re ad d ed to th e assemb lag e. I t is n o t n e c e ss a ry to su p p o se th a t fo r th i s in te rc h a n g e
th e r e was a co n tin u o u s c o n n e c tio n b e tw e en a n y Iavo o f th e s e lo c a litie s , fo r a n in te rm e d ia te la n d ,
peopled Avith some o r all o f th e p la n ts com m o n to b o th , m a y h a v e ex isted b e tw e en N ew Z e a la n d a n d
Ch ili w h en n e ith e r o f th e s e co u n trie s was as y e t above w a t e r f . T o a c co u n t, hoAvever, fo r th e A n ta r c tic
p la n ts o n th e lo fty m o u n ta in s , a n ew s e t o f in flu en ces is d em a n d e d ; n o la u d c o n n e c tio n b e tw e e n
th e se is lan d s an d N ew Z e a la n d co u ld h av e effected th is , fo r th e c lim a te o f th e in te rm e d ia te a re a
m u s t n e c e ssa rily h av e p re v e n te d it. B u t ch an g e s o f r e la tio n b e tw e en se a a n d la n d in d u c e ch a n g e s o f
clim a te , a n d th e p re sen c e o f a la rg e c o n tin e n t co n n e c tin g th e A n ta r c tic is la n d s would, u n d e r c e rta in
circum stan c e s, re n d e r N ew Z e a la n d as co ld as B r ita in w'as d u rin g th e g la c ia l epoch. S ir C. LyeU
first d em o n s tra te d th is , a n d sh owed w h a t su ch co n d itio n s sh o u ld b e ; a n d b y c o n su ltin g th e ' P r in ciples
o f Geo lo g y ,’ m y re a d e r will u n d e rs ta n d hoAv sn ch a c lim a te w o u ld re ig n in th e la titu d e o f
N ew Ze a lan d , as th a t its flo ra sh o u ld co n s is t o f w h a t a re now A n ta r c tic fo rms o f v e g e ta tio n . T h e
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 Avest Irish flora, whose peculiarities appear to me
to be considerably over-estimated.
* I t 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 d o ; the cause is evident, for the bones of quadrupeds, shells of mollusca, and hard parts of many
animals, aflord an abundant means of specific identification, and such are preserved Avhcn the animals perish. In
plants the case is widely different; their perishable organs of I’eproduction, Avhich alone are available for systematic
purposes, arc seldom imbedded, even when other parts of the iilants are.
t Tins 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 oil, 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 mangroA’es, whose
parents grew on the opposite bank. Here, be it remarked, no subsidence is required, such as must have operated
in tlie assumed isolation of New Zealand.