INTRODUCTION. 
3 
POLYPODIACEiE. 
( Including Grammitis, Polypodium , Woodsia, Cistopteris, Aspidium, Asplenium, 
Scolopendrium, Blechnum, Pteris, Crypt ogramma, Adiantum. 
Polypod i ace^e, Br., D.C., Kaulf., Bory, Hook., Grev., Mack., 8fc. 
Filices ver.e, Willd., Linn., Schreb., Juss. 
Filices Annulat.-e, Hoffm. 
Filices Gy hale , Web., Mohr, Swtz. 
Filices Dorsifer/e, Smith. 
Filicales, Lindt. 
Pteridales, Filicales Phyllopterides, Epipiiyllospermeas, &c. &c. 
STRUCTURE.* — A Fern consists of root, frond, and fructification. The 
rliizomas or subterranean stems, as well as the fibrils or true roots, are included 
under the first term ; while the frond comprises every part above the ground, 
except the fruit and its appendages ; and is subdivided into rachis or stem,f and 
pin me or leaves, which latter are generally more or less compound, lobed, or 
indented. 
The Root of all our native Ferns is perennial and fibrous. The fibres are 
stout, generally hairy or scaly, and in many instances furnished at the extremity 
with hoods or sheaths, the use of which is not very obvious. Modern botanists 
agree with Sprengel in believing them the organs of absorption, as the hoods of 
the Lemna and some other of our water plants. Roth maintained that they were 
mere defensive organs, intended to prevent the introduction of the grosser fluids, 
and to shield the extremity of the fibre from injury. In many cases the fibres 
issue from a crown, and form a tufted root : in others, from thick stems, which in 
the British species creep under ground, sometimes to a considerable distance. 
These rhizomas or creeping stems are furnished with buds, irregularly disposed 
upon their surface ; the uppermost ones yielding fronds, while those below produce 
as invariably radical fibres. 
The Rachis is sometimes smooth, at others scaly or hairy, sometimes wholly 
clothed with leaf-like expansions ; at others void of them at the lower part. When 
cut transversely, it is seen to consist first of a cuticle ; then we find a hard, woody, 
green, brown, or black bark, the space within being filled with cellular tissue. 
Longitudinally through the tissue run bundles of sap vessels, most of which are 
true spirals ; not, however, formed of a cylindrical thread, coiled up as in more 
* In illustration of the structure of all the tribes, the reader is referred to the illustrations 
of genera and their explanation. The stomata afterwards spoken of may very easily be seen 
in any under part of the cuticle, merely by tearing it off and submitting it to the microscope. 
The arrangement of the vessels in the stem is apparent to the unassisted eye in any transverse 
section of it ; and to view the spiral vessels it is only necessary to take two pins, and having 
thrust them through one of the bundles of vessels, separate them a little from each other, 
and in the cleft thus made the spirals will appear distinct when considerably magnified. 
t In the progress of the work it has not been thought necessary to make a difference between 
the rachis and stipes, nor to divide the part under ground into root and rhizoma, the first 
term of each being sufficient. 
