

xii PREFACE. 
very many so-called species, founded on slight differences, and 
often on the mere fact of geographical separation, are nothing 
more than local variations. Many apparently genuine species 
become broken down and amalgamated by the discovery of such 
connecting varieties, it may be, at their antipodes; and so an 
extended series of observations may eventually tend to bring 
the ‘species’ of the botanist in better agreement with those of 
Nature’s own contrivance. We may at least prove, from the 
evidence afforded by the variations among the British Ferns, that 
so-called ‘species’ do vary very much within a limited area; 
and may hence draw the inference, sufficiently supported by facts, 
that they vary much more when a wider range is taken into 
account; such a conclusion being clearly unfavourable to the 
multiplication of their numbers. 
These considerations do not at all affect the question whether or 
not the forms, widely different as many of them are, to which we 
have been referring, are to be recognised and named, as distinct 
objects. They exist, and they upset all definitions of species when 
they are ignored; so that in some form or other, whether as “species” 
or ‘varieties,’ they command the attention of even the most rigid 
and conservative of botanists. 
We have only further, in this place, to perform the grateful task 
of tendering our thanks, generally, to those who have kindly assisted 
us with materials both for description and illustration. In particular 
our account of the many variations of some of the species, could not 
have been so complete without this assistance. We trust that the 
friendly intercourse now for many years held with the majority of 
our most enthusiastic Fern-gatherers, may yet long continue. 
CHELSEA, August 31st, 1859. 

