FERNS. 
THE plants included in this work form, together, a group 
known to botanists as vascular cryptogams , and have certain 
characters in common by which they are distinguished from other 
groups of plants, but, among themselves they present a con- 
siderable range of variation in structure, and no one who knows 
a little of botanical classification would think of associating with 
ferns such plants as Marsilia, Isoetes, or Psilotum. The con- 
nection will be explained further on ; but restricting ourselves 
meantime to the ferns, though most readers are familiar with them 
as a group, there are many who, while they recognise a plant as a 
fern, can give no definite character which identifies it as such, or 
which distinguishes it from other plants resembling ferns. This is 
not because they possess no such character, but rather because their 
reproductive parts are so small as to be difficult to understand 
aright. Anyone who examines a fertile frond of the common 
Bracken will find that the margin all along is closely folded back 
upon the underside of the frond, and that under this reflexed edge 
there are numerous small bodies which, when examined by a 
magnifying glass, are found to be cases containing abundant dust- 
like particles, differing in structure from true seeds, but generally 
supposed to act as such. If the common scented fern be examined, 
it will be found to have these seed cases, or capsules , as they are 
called, under the reflexed edge all along the upper part of the 
frond only, while in the larger tree ferns, and in many other ferns, 
they are arranged in round dots which have certain fixed positions 
on the under surface of the frond. 
In all ordinary flowering plants, where seed is produced, it is 
formed after the flower, and is the direct result of the sexual 
B 
