X 
European Ferns. 
like the calyx, corolla, stamens, and pistil, susceptible of almost infinite variety and' modification, 
upon which the numerous genera are based. The minute reproductive organs on the prothallia 
of ferns have as yet been examined in comparatively few 
species, and even the prothallia themselves have not afforded 
any points of difference which can be used for classification, 
and the botanist accordingly does not take them into con- 
sideration. But the organs on the fully-developed fern con- 
nected with the production of the spores — that is, the sporangia 
both individually and as combined with sori and the indusium 
• — present us with important modifications, and it is these which 
are principally used in the classification generally followed. It 
is therefore quite necessary, when determining the name of any 
fern, first of all to examine these parts, by which alone its 
position can with certainty be ascertained. 
Before attempting to classify the bulk of our species, 
there are two genera which are so very different from all the 
rest as clearly to belong to a group of themselves : these are 
Ophioglossum and Botrychium. Their appearance is quite 
unlike that of the remainder of our species ; their fronds when 
young are not circinate, and the spike of fructification is given 
off from the base of the barren one ; the spores, too, are con- 
tained in cavities very unlike, and indeed quite different in 
origin from, the sporangia of other ferns. So fundamental 
are these points (and there are others), that the Ophioglossacece 
are by some botanists removed from the true ferns altogether, 
and constituted a distinct family. It contains one other genus, 
not European, called Helminthostachys. 
The great bulk of ferns remain, and they are found to 
fall under seven groups, of which the distinguishing marks are 
given below ; but only three of them have representatives 
in Europe — the BPymcnophyllacece, the Polypodiacece , and the 
Osmundacece, and by far the greater part belong to the second 
of these, which contains) indeed, three or four times more 
species than all the other groups put together, and has to be 
divided into a number of tribes. Of our European Ferns, 
Trichomanes and Hymenophyllum fall under the Hymenophyl- 
lacece, and Osmunda under the Osmundacece ; all the remainder 
belong to the Polypodiacece. The above-named ferns are each 
so characteristic as to be readily recognised, and the difficulty 
of determining the genus to which any specimen belongs can 
scarcely occur with any of them. It is different with the 
Polypodiacece , and we must now say a few words on the classi- 
fication of this great sub-order. 
Many plans have been proposed for grouping this: the character of the rhizome — desmobryoid 
or eremobryoid (see above*) ; the venation, and the habit ; but the most convenient single 
THE ADDER’S-TONGUE ( Ophioglossum 
vulgatum.) 
* These two terms have been unfortunately transposed at p. iv. 
