M a d ra s p en in su la , e x c e p t th e w e ste rn co a s t and m o u n ta in s , th e v a lle y o f th e Ir raw ad d i, an d th e low e r
fla t d is tr ic ts o f th e M a la y I s la n d s , w h en c e it is c o n tin u e d in g r e a t fo r c e o v e r th e w h o le o f t r o p ic a l
A u s tr a lia .
R e v e r s in g th e p o s it io n , and b e g in n in g a t th e so u th e rn e x tr em e o f th is aa*c o f v e g e ta t io n , th e r e is
first th e A n ta r c tic F lo r a ( th e c om p lem e n t o f th e S c a n d in a v ia n ), w ith it s d e c id ed A u s tr a lia n rep r e sen ta
tiv e s in C en tro le p id eæ au d S ty lid ieæ , c om m e n c in g in F u e g ia , th e F a lk la n d s , and L o rd A u ck la n d ’s and
C am p b e ll’s g r o u p , r eap p ea r in g iu tb e a lp s o f N ew Z ea la n d , T a sm a n ia , aud A u s tr a lia , an d d isap p ea r in g
u n d e r th e eq u a to r , o n th e a lp s o f B o r n e o , b e in g th u s s tr ic tly con fin ed to th e so u th e rn h em isp h e r e .
N e x t th e r e i s th e A u s tr a lia n F lo r a prop e r, a la r g e and h ig h ly d ev e lop ed o n e , d im iu ish iu g rap id ly afte r
c r o s s in g th e so u th e r n trop ic , a n d as i t ad v an c e s tow ard s th e n o r th -w e s te rn sh o r e o f th e c o n tin e n t ,
r e a p p ea r in g in v e r y sm a ll n um b e r s in th e M a la y Isla n d s , a n d te rm in a te d b y a C a su a r in a on th e ea st
c o a s t o f th e B a y o f B e n g a l, and a S ty lid iu m on th e w e st. N o t o n e r ep r e sen ta tiv e o f th is v eg e ta tio n
a d v a n c e s fu r th e r n o r th -w e s t.
A n a lo g o u s a p p ea ran c es are p r e sen ted b y A fr ic a an d A m e r ic a . I n A fr ic a In d ia n fo rm s p r ev a il
th r o u g h o u t th e tro p ic s, an d , p a s s in g so u thw a rd s, o c c u p y th e n o r th e rn b o u n d a ry o f th e s o u th t em p e ra
te z o n e ; b u t th e r e a v e r y c o p io u s an d w id e ly d iffe r en t v e g e ta tio n su c c e ed s, o f w'hich b u t few r ep r e se
n ta t iv e s ad v an c e n o r th to tb e trop ic , au d n o n e t o In d ia , b u t w ith w b ich are m in g le d S ca n d in a v ia n
g en e r a and ev en sp e c ie s . In th e N ew W o r ld , A r c tic , S c a n d in a v ia n , an d N o r th A m e r ic a n g en e r a and
sp e c ie s ai-e c o n tin u o u s ly e x ten d ed from th e n o r th to th e so u th t em p e r a te an d ev en A n ta r c t ic z o n e s ;
bu t sc a r c e ly o n e A n ta r c tic sp e c ie s , or e v e n * g e n u s [F o r s te ra , C a lc e o la r ia , Co lo b an th u s, G u n n e ra , e tc .
e tc .) a d v an c e s n o r th b e y o n d th e G u lf o f M e x ic o .
T h e s e c o n sid e r a tio n s q u ite p r e c lu d e m y en te r ta in in g th e id e a th a t th e S o u th e rn an d N o r th e r n
F lo r a s h a v e h a d c om m o n o r ig in w ith in com p a r a tiv e ly m o d e rn g e o lo g ic a l e p o c h s ; o n th e contrary,
th e E u r o p e a n an d A u s t r a lia n F lo r a s se em t o m e to b e e s s e n tia lly d is tin c t, an d n o t u n ited b y th o se
o f in te r v e n in g c o u n tr ie s , th o u g h fr a gm en ts o f tb e fo rm e r are a sso c ia ted w ith th e la tt e r in th e so u th e rn
h em isp h e r e . F o r in s ta n c e , I reg a rd th e In d ia n p la n ts in A u s tr a lia t o b e a s fo r e ig n to it , b o ta n ic a lly ,
as th e S c a n d in a v ia n , an d m or e so th an tb e A n ta r c tic ; an d th a t t o w h a te v e r le n g th s th e th e o r y o f v a r ia tio
n m a y b e car ried , w e c a n n o t b y i t sp e cu la te o n th e S o u th e r n F lo r a b e in g d ir e c t ly a d e r iv a tiv e o n e
from th e e x is t in g N o r th e r n . On th e con tr a r y , th e m a n y b on d s o f affin ity b e tw e en th e th r e e so u th e rn
F lo r a s , th e A n ta r c tic , A u s tr a lia n , an d S o u th A fr ic a n , in d ic a te th a t th e s e m a y a ll h a v e b e en m em b er s
o f o n e g r e a t v e g e ta tio n , wRich m a y o n c e h a v e cov e r ed a s la rg e a so u th e rn area a s th e E u r o p e a n n ow
d o e s a N o r th e r n . I t i s tr u e th a t a t som e a n te r io r t im e th e s e tw o F lo r a s m a y h a v e h ad a com m o n
o r ig in , b u t th e p e r iod o f th e ir d iv e r g en c e a n ted a te s th e c r ea tio n o f th e pr in c ip a l e x is t in g g en e r ic
fo rm s o f ea ch . T o w h a t p o r tio n o f th e g lo b e th e m a x im um d e v e lo pm en t o f th is S o u th e r n F lo r a
is to b e a s s ig n ed , it is v ain a t p r e sen t to sp e c u la t e ; b u t th e g e o g r a p h ic a l ch a n g e s th a t h a v e r e su
lt e d in it s d ism em b e rm e n t in to iso la ted g ro u p s sca tte r ed over th e S o u th e rn O c ean , m u s t ha v e
b e en g r e a t in d e e d . C ir cum sc r ib ed a s th e s e F lo r a s ar e , an d en c ro a ch ed up on e v e ryw h e r e b y n o r th e rn
fo rm s, th e ir u ltim a te d e s tin y m u s t d ep en d o n th a t p ow er o f appropr iation in th e str ife for p la c e wh ich
w e s e e in th e fo r c e w ith w h ich an in t r u s iv e fo r e ig n w e ed e s ta b lish e s it s e l f in o u r a lr ead y fu lly p eopled
fie ld s a n d m e a d ow s, an d o f th e r ea l n a tu r e o f w h ich p ow er n o c o n c e p t io n h a s b e en fo rm ed b y n a tu ra
lists, an d w h ic h h a s n o t e v en a n am e in th e la n g u a g e o f b io lo g y . E v e r yw h e r e , h ow ev e r , w e s e e th e
m o r e w id e ly d is tr ib u ted , an d th e r e fo r e le a s t p e cu lia r fo rm s o f p la n ts , sp r ead in g , and th e m o s t p e cu lia
r d y in g oJit in sm a ll areas, a n d th e p ro g r e ss o f c iv iliz a tio n h a s in tr o d u c ed in m a n a n ew e n em y to
* Acæna is a remarkiible exception. See p. xc. in note.
th e sca rc e o ld fo rm s, and a s tr o n g a lly o f th o s e a lread y c om m o n : n o r ca n i t be d o u b ted b u t tb a t
m a n y o f th e sm a ll lo c a l g en e r a o f A u s tr a lia , N ew Zea lan d , and S o u th A f r ic a , w ill u lt im a t e ly disappear,
ow in g t o th e u su rp in g t e n d en c ie s o f th e em ig r a n t p la n t s o f th e n o r th e rn h em isp h e r e , e n e r g e tic a lly
su p p o r ted as th e y are b y th e ar tific ia l a id s th a t th e n o r th e rn rac es o f m an afford th em .
§ 1 4 .
On som e o f th e N a tu r a liz e d P la n ts o f A u s tr a lia .
M y so u r c e s o f in fo rm a tio n u p o n th is su b je c t are u n fo r tu n a te ly e x t r em e ly s ca n ty , and a lm o st con fined
to d a ta procured from th e v ic in ity o f M e lb o u rn e , wh e r e M r . A d am so n h a s p a id e sp e c ia l a tt e n tio
n to th e in tr o d u c ed sp e c ie s w h ich h a v e ru n w ild , and a ssum ed th e p o s itio n s and im p o r ta n c e o f
n a tiv e p la n ts. I t w o u ld b e in te r e s t in g to d isco v e r th e d a te and pa r ticu la r c ir cum s ta n c e s u n d e r
w h ich th e s e p la n ts w e r e in tr o d u c ed , an d so to r e g is te r th e ir in c r ea se an d m ig r a tio n s as t o afford
to su c c e ed in g ob se rv e r s th e m e a n s o f c om p a r in g th e ir fu tu r e c o n d itio n w'ith th e ir p r e sen t. I n th e
ea r ly t im e s o f a c o lo n y , th e r e is com p a r a tiv e ly lit t le d ifficu lty in d is tin g u ish in g th e c o lo n is ts from
th e n a tiv e sp e c ie s ; b u t a s th e su r fa c e o f th e lan d b e c om e s a r tific ia lly d istu rb ed , tb e h a b its o f a ll it s
p la n ts are in flu en c ed ,— tb e en d em ic sp e c ie s a r e dr iv en from th e ir n a t iv e p la c e s, and ta k e r e fu g e in
h ed g e row s, d itch e s, and p la n ted co p se s, an d from th e r e a s so c ia tin g w ith th e in tr o d u c ed p la n ts , are
ap t to b e c la ssed in th e sam e c a te g o r y w ith th em ; w liils t th e in tr o d u c ed w an d e r fr om th e cu ltiv a ted
sp o ts and e je c t th e n a tiv e , or, ta k in g th e ir p la c e s b y th em , appear, lik e th em , to h e tru ly in d ig en o u s .
Th e r e are m a n y in te r e s t in g su b je c ts o f in q u ir y c o n n e c ted w ith th is r ep la c em en t o f o n e v e g e ta b le b y
an o th e r , su ch a s d e te rm in in g th e r e la tio n s b e tw e en th e fa c ility w ith w h ich th e n ew p la n ts o f c e r ta in c o u n tr
ie s or g en e r a are in tr o d u c ed an d e s ta b lish th em s e lv e s , an d th e c o u n tr ie s su ch p la n ts com e from , or
F lo r a s o f wh ich th e y form a p a r t.* M u ch o f c o u r se d ep en d s o n th e n ew com e r f in d in g a su ita b le
c lim a te a n d s o il for it s fu tu r e in c r e a se , b u t th e r e m a y b e m o r e in th e p h y s iq u e o r c o n s titu tio n o f th e
n ew c om e r th a t en a b le s i t to d isp la c e o th e r p la n t s ^vbich are a p p a r en tly eq u a lly w e ll ( if n o t better )
ad ap ted to th e c ir cum sta n c e s i t finds it s e lf en v iro n ed w ith . T h e n a tu r e o f th e p a s t in te r c o u r s e b e tw
e en E u r o p e and A u s tr a lia sh o u ld le a d u s to a n tic ip a te th a t a far g r e a te r n um b e r o f E n g lish p la n ts
are n a tu ra liz ed iu A u str a lia th a n o f A u s tr a lia n in E n g la n d ; b u t th e fa c t o f im p o r ta tio n d o e s n o t
e x p la in n a tu r a liz a tio n , n o r boAV it is th a t n o A u str a lia n p la n t h a s b e c om e n a tu r a liz ed in E n g la n d .
T h is to ta l w a n t o f r e c ip r o c ity in m ig i’a tio n is n o d o u b t m a in ly a ttr ib u ta b le to c lim a te , b u t th e n we
h a v e th e ap p a r en t d o u b le a n om a ly , th a t A u s tr a lia is b e t te r su it e d to som e E n g lish p la n ts th a n E n g la
n d is , an d th a t som e E n g lis li p la n ts are b e tte r su ite d to A u s tr a lia th a n th o s e A u s tr a lia n p la n ts we re
w h ich h a v e g iv e n w a y b e for e E n g lish in t r a d e r s . F o r ray ow n par t, I am d isp o sed to c o n sid e r th a t
tb e th r e e e lem e n ts o f (1) a b u n d a n t ex p o r ta tio n o f s e ed from E u r o p e in to A u s tr a lia for ag r icu ltu ra l
an d h o r ticu ltu r a l p u rp o se s, au d s c a n ty exp o r t o f A u str a lia n se ed p ro d u c e to E n g la n d ; (2) b e tte r
adap ta tion o f A u s tr a lia th a n E n g la n d to su p p o r t n um e ro u s fo rm s o f v e g e ta b le lif e ; and (3) a b u n d
a n c e o f u n o c cu p ied g ro u n d iu A u s tr a lia a s com par ed w ith E n g la n d ; are, com b in ed , a ll b u t su fficien t
to a c c o u u t for th e pr ed om in an c e o f so m an y E u rop ean n a tu ra liz ed p la n ts in A u stra lia , and fo r th e
c on v e r se s ta t e o f th in g s in E n g la n d . B u t I th in k i t m a y s t ill r em a in to b e se en w h e th e r th e alte r ed
* The reader will find some admirable discussions on this and kindred subjects in the chapters of A. De Candolle’s
‘ Géographie Botanique Raisomiéc ’ devoted to naturalized and introduced plants.