INTRODUCTION. 
5 
The Scales so visible upon some species, have been thought merely an 
excrescent growth caused by superabundant sap exuded from the surcharged 
pores. Sprengel supposed that they were part of the epidermis itself, lacerated 
by the pressure of the juices beneath. Perhaps both of these opinions are cor- 
rect, a part of the epidermis of the frond being first detached, and afterwards 
nourished in the same manner as animal hair, and although void of life, yet 
increasing from the base. 
The Cuticle of the leafy portion of the frond presents a reticulated appear- 
ance (the meshes having wavy sides), and is furnished on the under surface 
with respiratory stomata, similar in form and function to those of Flowering 
Plants. The number of these on a given space is in a great degree accordant 
with the rapidity of the frond’s withering when gathered. They are very abun- 
dant in Aspidium filix-foemina, Aspidium dilatatum, and Polypodium Dryopteris. 
Thus is explained the cause of the drooping habit of this last and some other 
species. Be it observed, however, that in Grammitis ceterach and Aspidium 
lobatum they are still more numerous, yet these latter plants do not wither so 
soon, a circumstance that may easily be accounted for from the frond of both 
being thicker, the deprivation of an equal quantity of water not producing so 
great an effect. 
THE REPRODUCTION of Ferns is a subject involved in much obscurity, 
lledwig, Bernhardi, and others, have proposed theories to explain this intricate 
matter, but without success. That the Ferns have no visible flowers is evident ; 
but that they have some apparatus analogous to stamens, is maintained by most 
of our first botanists. So keen has been the search for these in the present tribe, 
that every part of the plant has been subjected to the minutest investigation ; not 
only the thecae, their ring, and their cover, but the spiral vessels of the rachis, 
the stomata upon their cuticle, and the glands which are sometimes found 
attending upon them. 
Sprengel long ago stated that the young sori, or rather that the swelled extre- 
mity of the veins of Polypodium vulgare, which sometimes remain abortive, and 
at others produce thecae, w T ere filled with oblong-shaped bodies of a greyish colour, 
which he considered to he stamens, and as yielding pollen in the same manner as 
the external stamens of flowering plants. These being attended upon by young 
ovules, the latter became impregnated and grew* to perfection, while the pollen 
masses were decayed or absorbed. This opinion was in a great degree and for a 
long time disregarded (perhaps because of his imperfect figures), and the grey 
bodies considered to be abortive capsules. The following remark, however, from 
‘ The Annals of Natural History,’ given in the synopsis of a paper read before 
the Academy of Sciences at Berlin, March 1840, by Professor Link, throws a 
stronger light upon the subject. “ The part which Sprengel years ago indistinctly 
figured, and which Blume and Presl at present consider to be made organs of 
fructification, have been more accurately examined by Professor Link, and illus- 
trated by drawings. They are long hollow filaments, separated by septa into 
articulations generally simple, rarely ramified; the last articulation is thicker, 
