During cool and wet summers, the native flora of the islands of the Outer Hebrides creates an extravagant display of wildflowers. The bright and beautiful will always attract attention, but some of the more modest members of the plant kingdom such as the ferns, are worthy of attention and offer a fascinating insight into the diversity and complexity of our natural environment.
The ferns are the group of non-flowering plants which most of us can recognise, and although they have their enthusiasts amongst botanist and gardeners, they attract relatively little attention from the other members of the community. There are only 60 species of ferns in Britain and about 30 in the Outer Hebrides. This is a tiny fraction of the global diversity and a small remnant from the period when they first emerged when the dinosaurs ruled. For plants that do not have flowers, they have a subtle charm. They are not amongst nature’s extroverts but there is sometimes a suggestion of a hint of magic and other worldliness.
The question of how a plant, which produced no obvious flowers or seeds, could reproduce, perplexed our forefathers and implied the involvement of magic or witchcraft. Searching for fern seeds was believed to be fraught with danger, but success brought good fortune. The possession of these elusive seeds was believed to endow the power of invisibility, as observed by Shakespeare in Henry IV, Part I:
“we have the receipt of fern-seed; we walk invisible”.
Eventually the mystery was resolved in the mid-19th century, alas not magic but the production of spores and two alternating generations. The spores are produced in sporangia which form clusters (sori) on the underside of the frond, although in some species not all the fronds are fertile. Perhaps a risky process, but the ability of a mature plant to produce millions of spores seems to ensure success.
Most of us will be familiar with the large ferns found in shady woodlands or on moist banks, and even the smaller, more delicate species found in rock crevices, walls and mountain ledges are recognisable as ferns. They all have a similar structure with the leaves or fronds arising from a rhizome (swollen stem) with a central stem and the leaf blade which is either simple (complete) or divided. Some flowering plants have fern-like leaves, but a closer look will reveal differences in structure and the absence of sori on the underside of the leaf.
For a group of plants which have been evolving for over 400 million years, it is not surprising that some species are atypical, and structurally and genetically distinct. These are the Ophioglossums (adder’s-tongues and moonworts). They are small and inconspicuous and can be found in moist, unimproved grassland or in sand dunes, particularly in dune slacks.
In adder’s-tongues there is one sterile, slightly succulent undivided leaf and a single central stem which has sporangia arranged on either side. Moonworts are similar, but the sterile leaf is divided (pinnate) and the stalk bearing the sporangia is branched.
Flowering plants, grasses, sedges and ferns of Great Britain (1865). Ann Pratt.
Image from the Biodiversity Heritage Library. Contributed by Cornell University Library.
These are slightly mysterious plants, which in some years remain hidden underground and in others only produce sterile leaves. Their enigmatic nature and unusual structure have given rise to some interesting attributes. The snake like appearance of adder’s-tongue is clearly the source of the common name, and its alleged reputation as a cure for snake bite. Similarly, the pinnate nature of the sterile leaf in moonwort is said to resemble a key which is believed to unlock the portals to the underworld or remove the shoes from your horse should you be unwise to gallop over it.
Ferns have a reputation as being challenging to identify, but perhaps no more than some other groups of flowing plants such as grasses. However, do take the time to take a closer look, after all they are the descendants of a group of plants which survived the mass extinction which wiped out 75% of the Earth’s animals, including most of the dinosaurs.