26 BRITISH FERNS. 
the back of the frond; but this character being 
Common to more than a thousand species, an im- 
Provement was suggested, namely, that the masses 
of seed in the true genus Polypodium ought to be 
naked, that is, uncovered by that filmy membra- 
naceous scale to which has been applied the sounding 
and singular name of “indusium.” Thus restricted 
the genus includes certain British Ferns which have 
not the slightest relationship to each other; such 
are Vulgare, Dryopteris and Alpestre; and these 
differ more essentially than any others that could 
be named. Eventually a more natural system will 
undoubtedly prevail, but at present all is artificial, 
unnatural and arbitrary. | kas 
- Then, as regards the arrangement of species: it 
is impossible for the candid mind to dwell for a 
moment on the fact that Britain Produces only about 
one-fourth part of the ferns already known as in- 
habiting the globe, without Perceiving the imprac- 
ticability of arranging that fractional part in anything 
like a connected series. Select one British species, 
find that there are at least a hundred Species which 
the True Maidenhair, as an instance, 
