INTRODUCTION. 
3 
POLYPODIACEAE. 
(Including Grammitis, Polypodium , Woodsia, Cistopteris , Aspidium, Asplenium, 
Scolopendrium, Blechnum, Pteris, Cryptogramma, Adiantum.) 
PoLYPODiACEiE, Br., D.C., Kaulf., Hook., Grev., Mack., %c. ; — Filices ver.e, 
Willd., Linn., Schreb., Juss. ; — Filices Annulate, Hoffm. ; — Filices 
Gyrate, Web., Mohr., Sw.z.; — Filices dorsieer.e, Smith ; — Filicai.es, 
Lindl. ; — Pteridales, Filicales Phylloeteriues, Epiphyllosper- 
ME.E, l$C. $C. 
STRUCTURE.* — A Fern consists of root, frond, and fructification : under 
the first term is included the rhizomas or subterranean stems, while the frond 
comprises every part above the ground except the fruit and its appendages, and 
is subdivided into rachis or stem,f and pimne or leaves, which latter are more 
or less branched, lobed, or indented. 
The Root of all is perennial, fibrous, and sometimes creeping. The fibres 
are stout, generally hairy or scaly, and in many instances furnished at the ex- 
tremity 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 Lemme 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 other 
instances from thick stems, which in the British species creep under ground. 
These Rhizomas or creeping stems are furnished with buds irregularly dis- 
posed 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 
green bark, and the space within this is filled with cellular tissue. Through 
the tissue run longitudinally accumulated vessels, most of which are true 
spirals, not, however, formed of a cylindrical thread coiled up as in more per- 
fect plants, but rather of a flat band, like a riband rolled spirally on a cylinder. 
*In illustration of the structure of all the tribes, the reader is referred to the Plate of Genera 
and its 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 arrange- 
ment of the vessels in the stem are 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 betweeu 
the Rachis and Stipes, nor to divide the part under ground into Root and Rhizoma, the first term 
of each being sufficient. 
A 2 
