INTRODUCTION. 
5 
compound, the larger divisions first opening, and by degrees the pinnae and 
pinnules. 
The Scales, so visible upon the stems and petioles of some species, have 
been regarded by some authors as leaves, the true leaf being then called a branch. 
The term ramentum is often applied to these scales which, with those found upon 
the divisions of the leaves, are probably mere appendages of the epidermis, like 
the hairs and scales found on the surface of the higher plants. 
The Epidermis of the expanded portion of the leaf presents a reticulated 
appearance (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. On the number of these on a given space is in a great degree dependent 
the rapidity of the leaf’s withering when gathered. They are very abundant in 
Aspidium filix-fcemina, 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 leaves of both being 
thicker, the deprivation of an equal quantity of water not producing so great 
an effect. 
THE REPRODUCTION of Ferns has long been a subject involved in much 
obscurity. Hedwig, Bernhardi, and others, proposed theories to explain this 
intricate matter, but without success. That the Ferns have no visible flowers is 
evident ; but that they had some apparatus analogous to stamens, was 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 epidermis, and the glands which are 
sometimes found attending upon them. 
Sprengel long ago stated that the young sori, or rather that the swollen extre- 
mity of the veins, of Polypodium vulgare, which sometimes remain abortive, and 
at others produce thecae, were filled with oblong-shaped bodies of a greyish colour, 
which he considered to be 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 decayed or were 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 remarks, 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, drew a 
stronger interest to the subject : — “ The part which Sprengel years ago in- 
distinctly figured, and which Blume and Presl at present consider to be male 
organs of fructification, have been more accurately examined by Professor Link, 
and illustrated by drawings. They are long hollow filaments, separated by septa 
into articulations generally simple, rarely ramified ; the last articulation is thicker, 
