8 
INTRODUCTION. 
given by Suminski, but these have been since made out, and the existence of 
sexes in the Ferns placed beyond a doubt. Thus the supposed hybrid forms 
which had been frequently observed among cultivated Ferns, are no longer 
anomalous or inexplicable. It will be unnecessary to enter very minutely here 
into the phenomena now in question, or into the history of their elucidation ; a 
full account of these points will be found in the ‘ Transactions of the Linnean 
Society.’* The main particulars are as follows : — At an early period of the 
expanding growth of the leaf-like product of the spore (called the prothalliuin, 
or germ-frond), a number of little cellular bodies are found, projecting from the 
lower surface, which, if placed in water -when ripe, burst and discharge a quantity 
of microscopic filaments, curled like a cork-screw, and furnished with vibrating 
hair-like appendages (cilia), by the motion of which they are actively propelled 
through the water. The cellular bodies from which these are discharged, are 
called the antheridia of the Ferns, and are, in their physiological nature, the 
representatives of the pollen of the Flowering Plants. At a somewhat later period, 
other cellular bodies, of larger size and more complex structure, are found, in 
small number, about the central part of the lower surface of the prothallium, on 
the thickened portion situated between the notch and the part where the radical 
filaments arise. These, the pistillidia or archegonia of the Ferns, are analogous to 
the ovides or nascent seeds of the Flowering Plants, and contain, like them, a 
germinal vesicle, which becomes fertilized through the agency of the spiral 
filaments mentioned above, and is then gradually developed into an embryo plant 
possessing a terminal bud. This bud at once begins to unfold, and push out 
leaves with a circinate vernation, which are of very simple form at first, and rise 
up to view from beneath the prothallium, coming out at the notch ; single fibrous 
roots are at the same time sent down into the earth, the delicate, expanded 
prothallium withers away, and the foundation of the perfect Fern-plant is laid 
(see fig. h in the woodcut illustrative of the genus Asplenium). As the bud 
unfolds new leaves, the rootstock gradually acquires size and strength, and the 
leaves become larger and more fully developed ; but it is a long time before they 
assume the complete form characteristic of the species. — A.H.] 
NUMBER and DISTRIBUTION. — For the following remarks upon this 
subject I am indebted to H. C. Watson, Esq., than whom no botanist has more 
studied the subject. He says, “ Dorsiferous Ferns are found in even' part of 
Britain, except on the summits of the loftier mountains, and in small spaces of 
the lower grounds, whence they are banished by local peculiarities of the soil or 
surface. But overlooking these merely local exceptions, of trifling extent, Poly- 
podiaceae may be stated to range over the whole of Britain, from south to north, 
from east to west, and from the shores of the sea almost to the summits of flic 
highest hills; in which latter situation their absence is to be attributed rather to 
the bleak exposure than to the absolute height. The number of our dorsiferous 
Ferns will be estimated variously, according to the views entertained with respect 
* Henfrey on the Development of Ferns from their Spores. Linn. Transactions, 
vol. xxi, p 117- 
