ISOLATED STATIONS OF PLANTS. 211 
Ts not such our present experience, and such as we may con- 
jecture to have been the course in past time? Besides, no slight 
modifications may have arisen from the drying of the surface, 
whether natural or artificial, and this case is especially applicable 
to the narrowed range of aquatics such as Scheuchzeria (claimed, 
I believe, by certain other counties besides Yorkshire), to say 
nothing of the imperfect nature of negative evidence regarding 
an inconspicuous species. But if we have any species peculiarly 
British, as we have a Grouse, then must we suppose that it is the 
remains of a restricted dissemination which perhaps originated 
on that spot where we see it still. Such instances however ap- 
pear exceptional in the case of a district severed from a great 
continent, whence there was no difficulty in deriving its flora, 
though of course even the edge of a continent would have con- 
tamed centres much fewer in number than the central region. 
Far different were the opportunities for acquisition in a far 
isolated island, and there indeed we do find ample evidence of a 
separate creation; where there was need, there was the Hand to 
supply the want: and thence the origin of those remarkably dis- 
tinct faunas and floras of which we have experience. 
On the assumption too of “specific centres,’ with the assis- 
tance of the late Professor E. Forbes’s theory, there will per- 
haps be little difficulty in accounting for the peculiar position of 
Lloydia serotina ; nay, is not the highest of our southern group 
of mountains the very place where we should expect to find a 
native of the continental Alps, and sparingly, as in an_ outlying 
station ? 
‘Similarly we might ascribe the limited range, with us, of the 
Actea, to its being a member of the “ Germanic Flora,” at its 
furthest radiation, as well as to its partiality for limestone. 
And here it may perhaps be allowed to observe, that in our 
humble opinion the chemical, as well as the mechanical influence 
of soil, might well form a branch of study distinct from the geo- 
logical, which latter term would then be restricted to the expla- 
nation of the manner and degree in which the dissemination of 
species has been affected by the rising, subsidence, and disloca- 
tion of land. 
For further insight into the working of mineral causes, I pre- 
sume we must look to chemical analysis and the microscope, to 
say nothing of the effect which a hot, parching limestone-soil may 
