f i
I 1
re^pii’atio u , a n d rep ro d u c tio n , ai*e in fin ite ly m o re vai’i^blc a n d su sc ep tib le o f ch a n g e an d even o b lite r
a tio n in p la n ts , w ith o u t affec ting th e life e ith e r o f th e in d iv id u a l o r o f th e species*. T h e r e s u lt ot
th e s e facts is th a t we h av e th e m e an s in an im a ls o f a p p re c ia tin g th e e x te n t an d value o f diflercuces,
b y com b in ed o b se rv a tio n s u p o n structm*e a n d fu n c tio n s , u p o n h a b its a n d o rg an iz a tio n , w b ich ive have
n o t in th e v eg e tab le k in g d om , a n d w h ich th e p h en om e n a o f cu ltiv a tio n assui’e u s do n o t ex ist to a
d eg ree th a t h a s , w ith in th e lim it s o f oui' ex p e rien ce , p ro v ed av a ilab le fo r th row in g m u c h lig h t o n th e
su b je c t.
T h e a rg um e n ts in fav om o f th e p e rm an en c e o f specific c h a ra c te rs in p la n ts a r c :—
1. T h e fa c t th a t th e am o im t o f c h a n g e p ro d u c ed b y e x te rn a l causes does n o t w a r r a n t o u r a ssum -
ju g th e c o n tra i’Y as a g en e ra l law. T h o u g h th e re ai'e m a n y n o to rio u s cases in w h ich cu ltiv a tio n
a n d o th e r causes p ro d u c e ch an g e s o f g r e a te r a p p a re n t v alu e th a n specific chai’a c te rs g e n e ra lly possess,
th is h ap p e n s in compai’a th 'e ly v e ry few fam ilies, a n d o n ly in su ch as a re ea sily culti-\^ated. I n th e
wh o le ra n g e o f th e v eg e tab le k in g d om i t is difficult to p ro d u c e a c h a n g e o f specific v alue, h owever
m u c h we m a y a lte r c o n d itio n s ; i t is m u c h m o re difficult to p re v e n t a n in d u c e d v a rie ty from re v e rtin g
to its o rig in a l s ta te , th o u g h we p e rsev e re in s u p p ly in g th e o rig ia a l c o n d itio n s ; a n d i t is m o s t difficidt
o f all to rep ro d u c e a v a rie ty w ith sim ila r m a te ria ls a n d processes t -
2. I n tracLug w id ely d isp e rsed species, th e p e rm a n e n c e w ith wliich th e y r e ta in th e ir ch a ra c te rs
s trik e s th e m o s t ordinai*y o b s e rv e r; a n d th is , w h e th e r we ta k e su ch p la n ts as h av e b e e n d ispersed
^vithout th e a id o f m a n (as S onchus oleraceus, Callitriche, a n d M o n tia ) th ro u g h a ll la titu d e s from E n g la
n d to N ew Z e a la n d ; o r su ch as h av e w ith in m o d em tim e s followed th e m ig ra tio n s o f m a n (as Po a
annua, P h a la r is Canarieyisis, D o ck , Clover, A ls in e m edia, Capsella bu rsa -p a sto ris, a n d a h o s t o f o th e rs) ;
o r su c h as m a n tr a n s p o r ts w ith h im , w h e th e r su ch tem p e ra te c lim a te p la n ts as th e ce re alia, fru its , an d
flowers o f th e g a rd e n o r field, o r su ch tro p ic a l fo rm s as Convolvulus B a ta ta s a n d y am s, w h ich were
in tro d u c e d in to N ew Z e a lan d b y it s e a rlie s t in h a b ita n ts ;— all th e se , in w h a te v e r c lim a te to w h ich we
m a y follow th em , r e ta in th e im p re s s o f th e ir k in d , u n c h a n g e d save in a triflin g d egree .
Though to a great extent these differences accompany a habit of growth (as in the case of erect and scandent Bauhi-
nidi), there is nothing in the abnormally developed wood of the climbing Bauhinia that would lead a skilled physiologist
ignorant of the fact to say that it was better adapted to a climbing than to an erect p lan t; the function is
experimentally known to be indicated by the structure, but the structure is not seen to be adapted to the function.
This is not so in the sister kingdom, for we confidently pronounce an animal to be a climber, because we see that
its organs are adapted to the performance of that function; here the habit is not only indicated by the structure,
but the latter is explained by the function which it enables the animal to fulfil.
• To take an extreme case of th is ;—many plants are known, in a wild and cultivated state, which propagate
abundantly by roots or division, where they do not do so by seed. Anackaris Alsinadrum is a conspicuous example
: it is a unisexual water-plant, of which one sex alone was introduced from North America into England,
where it has within a few years so spread by division as to be a serious impediment to inland navigation. The
Horse-radish is another example, it being, I believe, never known to seed or even to bear perfect flowers. A still
more remarkable case has been pointed out to me by i l r . Brown, in the Acorus Calamus, a plant spread (not by
cultivation) over the whole north temperate hemisphere, which bears hermaphrodite flowers, but very rarely seeds.
t I am quite aware th a t this argument will be met by many instances of change produced in our garden
p lan ts; but, after all, the skill of the gardener is successfully exerted in but few cases upon the whole: out of more
than twenty thousaud species cultivated at one time or another in the Royal Gardens of Kew, liow few there are
which do not come up, not only true to their species, but even to the race or variety from whicli they spring; yet
it would be difficult to suggest a more complete change than that from the Alps or Polar regions to Surrey, or
from the free air of the tropics to the thoroughly artificial conditions of our hothouses. Plants do not accommodate
themselves to these changes : cither they have passive powers of resisting their effects to a greater or less degree, or
they succumb to them.
3. AVith compai-ativcly few ex c ep tio u s, p la n ts a re co n fin ed Avitlnn w e ll-m a rk e d lim its , w h ich ,
th o u g h o fte n v e ry Avide, a re som e tim e s as m n c h th e r e v e r s e ; Avhile th e in s ta n c e s a re r a r e o f sp o rad ic
species, as su ch a re ca lled w h ich a re fo u n d in sm a ll n um b e rs in w id ely s u n d e re d lo c a litie s . T h e se
fa c ts seem in c om p a tib le o n th e o n e h a n d w ith th e th e o ry o f species s p re a d in g from m a n y c e n tre s , an d
o n th e o th e r w ith th e ir v a rjd n g in d e f in ite ly ; fo r were i t o tlie n ris c , sp o rad ic d is tr ib u tio n w o u ld b e th e
ru le , in su la r floras w o u ld n o t n e c e ss a rily h e p e c u lia r, a n d s im ila r c lim a te s w o u ld h a v e s im ila r, i f n o t
id e n tic a l species, w h ich is n o t th e case.
4. A m u ltitu d e o f allied sp ecies o f p la n ts g row close to g e th e r AvitUout an y in te rc h a n g e o f sp e cific
c h a r a c te r ; a n d th e r e a re in s ta n c e s o f e x c e ed in g ly c lose ly a llie d p la n ts k e e p in g com p an y u n d e r
m a n y mo d ific a tio n s o f c lim a te , soil, a n d e lev a tio n , y e t n ev e r lo s in g th e ir d is tin c tiv e m a rk s.
5. T h e indiAuduals th a t in h a b it th e c ircum fe re n c e o f th e a re a occu p ied by a species, a re n o t
fo u n d p a s s in g in to o th e r species, b u t ce asin g m o re o r le ss a b r u p t ly ; th e ir lim its m a y m e e t o r overlap
th o s e o f o n e o r m o re v e ry s im ila r species, w h en th e in d iv id u a ls asso c ia te , h u t do n o t am a lg am a te .
6. O n e n eg a tiv e a rg um e n t in fav o u r o f d is trib u tio n from o n e c e n tre o n ly , is, th a t ta k in g th e
b ro a d e s t Auew o f th e d isp e rs io n o f species, we fin d th a t th e m o re extensiA^e fam ilie s* a re m o re o r less
Aridely d is trib u te d , v e ry m u c h in p ro p o rtio n to th e fa c ilitie s th e y p re s e n t fo r d isp e rsio n . T h u s th e
m o s t m in u te -sp o re d Cry^ptogamsf a re th e m o s t AAudely d isp e rs ed o f a ll o rg an iz ed n a tu r e ; p la n ts th a t
re s is t th e in flu en c e o f c lim a te b e s t, ra n g e fLU-thest; w a te r-p la n ts a re m o re co sm o p o lite th a n la n d -
p la n ts , a n d in h a b ita n ts o f sa lt, m o re th a n th o s e o f fre sh w a te r : th e m o re eq u a b le a n d u n ifo rm is th e
cUmate o f a tr a c t o f la n d , th e m o re u n ifo rm ly a n d w id ely avUI its p la n ts h e d is trib u te d .
7. T h e species o f th e low e st O rd e rs a re n o t o n ly th e m o s t w id ely diffused, h u t th e ir specific
ch a ra c te rs a re n o t modified b y th e g re a te s t ch an g es o f c lim a te , h ow ev er m u c h th e ir s ta tu r e an d
lu xm ia n c e m a y v a ry . F u n g i offer a rem a rk a b le in s ta n c e o f t h i s : th e ir m ic ro s co p ic sp o re s a re Avafted
in m y riad s th ro u g h th e a i r ; th e life o f th e in d iv id u a ls is o fte n o f v e ry s h o r t d u ra tio n , a n d m a n y o f
th em b e in g as s en sitiv e as in s e c ts to tcm p e ra tiu 'e a n d h um id ity , th e y a re e p h em e ra l in all s e n s e s ;
som e tim e s a p p e a rin g o n ly o n ce in th e s am e sp o t, a n d rem a in in g b u t a few d ay s, n e v e r to re a p p e a r
AAithin th e o b serv er’s ex p e rien ce . T h e specific c h a ra c te rs o f m a n y re s id e in th e d iam e te r, fo rm , colour,
a n d a rra n g em e n t o f th e ir m o s t m in u te o rg an s , Avhose an a ly sis d em a n d s a re fin em e n t o f micro sco p ic
s k ill; y e t th e m o s t a c com p lish ed a n d p ro fo u n d b o ta n is t in th is N a tu r a l O rd e r (avIio h a s fav o u red m e
Avitli th e d e s c rip tio n s o f th e Ncav Z e a lan d F u n g i) fails to fin d th e m o s t triflin g c h a ra c te r b y wh ich
to s ep a ra te m a n y N ew Z e a lan d species from E u ro p e a n .
8. T h e fact, noAv u n iv e rs a lly co n c ed ed b y a ll in te llig e n t lio r tic u ltu r is ts , th a t n o p la n t h a s b e e n
a c c lim a ted in E n g la n d Avitliin th e ex p e rien c e o f m a n , is a v e ry suggestiA’e o n e, th o u g h n o t co n c
lu siv e ; fo r i t m a y be ansAvered, th a t p la n ts Avliich c a n n o t surAuve a su d d en ch a n g e , m ig h t a slow an d
p ro g ressiv e one. O n th e o th e r lian d , p la n ts h av e powers o f e n d u rin g c h a n g e Avhcn se lf-p ro p ag a ted
th a t th e y h av e n o t in o n r g a r d e n s ; th u s I find a g r e a t d ifte rcn c e in th e h a rd in e s s o f indiAudual species
o f several H im a la y a n p l a n t s j , d ep e n d in g u p o n th e a ltitu d e a t w h ich th e y Avere g a th e red . I n th e s e
* This rule does not extend to the Natural Orders themselves. The Composite, whose facilities for dispersion
arc proverbial, are amongst the most local; and the same may be said oi Leguminosa and Solanem, whose seeds
retain their vitality in a remarkable degree : a few of their species arc remarkably cosmopolite, but the greater number
liave generally narrow ranges.
t The fact (first communicated to me by the Rev. M. .1. Berkeley) of the spores of Fungi having been found
by Professor Ehrcnberg mingled with the atmospheric dust that has fallen on sliips far out at sea, is one of the
most decisive proofs of this.
X Thus some of the seedling Pines whose parents grew at 12,000 feet appear hardy, Avliilst those of the same
c 2