104 FILICES 
called the Wall Rue; or they form a ridge along the edge of the leaf, as in 
the Maiden Hair. More rarely they cluster closely, till all the segments of 
the leaf are contracted and curled up round the masses of fructification, and 
then they have an altogether different appearance, and resemble a kind of 
inflorescence. Our beautiful tall plant, called Royal Fern, and the little 
Adder’s-tongue found on pasture-lands, are instances of this form of fructi- 
fication. 
The small patches on the backs of fern-leaves are the sori, or clusters of 
capsules. The capsules themselves are sometimes termed spore-cases, or 
sporangia, or thece, and they contain the spores, which are the bodies from 
which another generation of ferns is produced. It is a mistake to call them 
seeds, for they differ widely in nature and origin from the seeds of flowering 
plants. A seed contains an embryo plant like that by whose floral organs it 
was produced. A spore is amere cell without cotyledons ; and instead of send- 
ing a shoot up into the air and radical fibres downward, as the seeds of flowering 
plants do, it germinates indifferently from 2ny part of the surface, but 
produces a plant quite unlike its parent. 
The capsules, as seen under a microscope, are beautiful objects, resembling 
little hollow spheres of crystal, tinged with a delicate brown hue, and sur- 
rounded by a jointed elastic ring, sometimes supported below on an exquisitely 
slender stalk. When the spores are fully matured, the ring is broken and 
its elastic nature causes various quick movements, by which the spores are 
jerked from the capsule like fine dust. In some plants, as in the Royal Fern, 
the Moonwort, and the Adder’s-tongue, the seed-cases are destitute of the 
elastic ring, and are two-valved. 
These clusters of spore-cases are sometimes formed outside the skin of 
the leaf, and are without covering ; but in most of our native ferns, especially 
during their early growth, the sori are covered by a thin membrane called 
the indusium. If we examine a young frond, we see first a number of little 
pale-coloured stripes appearing at equal distances upon some of the veins. 
In a short time the outer thin skin or cuticle of the leaf above these stripes 
separates a little from the green part; then it becomes raised by their 
growth, the raised part assuming the form of the little heap of capsules 
beneath ; till finally these burst through the skin, and separate it into two 
equal parts, one edge of which remains adhering to the leaf. This thin skin 
is the indusium, and it frequently disappears before the spores are ripened. 
The spores of ferns are very numerous, exceedingly minute, and of a some- 
what oval form. 
A fern-spore on germinating gives rise to a minute green scale (prothallus) 
which lies flat upon the ground, to which it becomes attached by delicate 
root-hairs from its under surface. This body is altogether different from a 
fern, and cannot grow into one, but it can develop organs by the interaction 
of whose products a true embryo may be produced, which may then grow 
into a fern. These organs are microscopic in size, and of two kinds. 
The first is the antheridium, and it corresponds roughly with the anthers of a 
flowering plant; but instead of discharging quiescent pollen-grains, the 
antheridium sets free a multitude of atoms (antherozoids) furnished with tails, 
and by lashing these they progress through moisture to their destination. 
