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Ferns: Explanation
of Terms,
adapted from
How to Know the
Ferns by Frances Theodora Parsons, illustrated by Marion
Satterlee and Alice Josephine Smith. Originally published in 1899
and now in the public domain.
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see photographic examples, click one of the cameras in the list of
botanical terms. |
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A fern is a
flowerless plant growing from a rootstock with leaves or
fronds usually raised on a stalk, rolled
up in the bud,* and bearing on their lower surfaces the spores,
by means of which the plant reproduces.
A rootstock
is an underground, rooting stem. Ferns are propagated by the growth
and budding of the rootstock as well as by the ordinary method of
reproduction.
The fronds spring
from the rootstock in the manner peculiar to species to which they
belong.
The Osmundas,
the Evergreen Wood Fern, and others grow in a crown or circle,
the younger fronds always inside.
The Mountain Spleenwort is one of a class which has irregularly
clustered fronds.
The fronds of the Brake are more or less solitary, rising from
distinct and somewhat distant portions of the rootstock.
The Botrychiums usually give birth to a single frond each season,
the base of the stalk containing the bud for the succeeding year.
* Ophioglossum
and the Botrychiums, not being true ferns, are exceptions.
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| SIMPLE |
PINNATIFID |
ONCE-PINNATE |
TWICE-PINNATE |
| A
frond is simple when it consists
of an undivided leaf such as that of the Hart's Tongue or of
the Walking Leaf. |
A
frond is pinnatifid when cut
so as to form lobes extending halfway or more to the midvein. |
A
frond is once-pinnate when
the incisions extend to the midvein. Under these conditions
the midvein is called the rachis,
and the divisions are called the pinnae.
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A
frond is twice-pinnate
when the pinnae are cut into divisions which extend to their
midveins. These divisions of the pinnae are called pinnules.
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A frond that
is only once-pinnate may seem at first glance twice-pinnate, as
its pinnae may be so deeply lobed or pinnatifid as to require a
close examination to convince us that the lobes come short of the
midvein of the pinnae. In a popular handbook it is not thought necessary
to explain further modifications.
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The
veins of a fern are free when, branching from the midvein,
they do not unite with other veins. |
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 SPORE |
Ferns
produce spores instead of seeds. |
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SPORANGIA
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These spores
are collected in spore-cases or sporangia.
Usually the sporangia are clustered in dots or lines on the back
of a frond or along its margins.
These patches
of sporangia are called sori or fruit-dots.
They take various shapes in the different species. They may be round
or linear or oblong or kidney-shaped or curved.
At times they
are naked, but more frequently they are covered by a minute outgrowth
of the frond or by its reflexed margin. This covering is called
the indusium. In systematic botanies
the indusia play an important part in determining genera. But as
often they are so minute as to be almost in visible to the naked
eye, and, as frequently they wither away early in the season, I
place little dependence upon them as a means of popular identification.
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A fertile
frond is one which bears spores.
A sterile
frond is one without spores.
Before attempting
to identify the ferns… it would be well to [read] the Explanation
of Terms, and with as many species as you can conveniently collect,
on the table before you, to master the few necessary technical terms,
that you may be able to distinguish a frond that is pinnatifid from
one that is pinnate, a pinna from a pinnule, a fertile from a sterile
frond.
You should bear
in mind that in some species the fertile fronds are so unleaf-like
in appearance that to the uninitiated they do not suggest fronds
at all. The fertile fronds of the Onocleas, for example, are so
contracted as to conceal any resemblance to the sterile ones. They
appear to be mere clusters of fruit. The fertile fronds of the Cinnamon
Fern are equally unleaf-like, as are the fertile portions of the
other Osmundas and of several other species.
In your rambles
through the fields and woods your eyes will soon learn to detect
hitherto unnoticed species. In gathering specimens you will take
heed to break off the fern as near to the ground as possible, and
you will not be satisfied till you have secured both a fertile and
a sterile frond. In carrying them home you will remember the necessity
of keeping together the fronds which belong to the same plant….
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