Plant Life in the Scottish Highlands
The Lochs (Part 2)

Amphibious Persicaria (Polygonum amphibium)

This is a very common plant in tarns, streams and watery places, and its handsome spikes of rose-pink flowers brighten the surface of the shallower waters.  As it forms large colonies the effect is heightened.

The thick, hollow stems, which have much swollen nodes, creep along the mud at the bottom of the pool.  From the nodes are given off many tough, much-branched, fibrous, reddish roots which anchor the plant firmly and prevent it from being dragged away by currents.  The creeping stem becomes erect at the extremity, branches profusely, and rises to the surface of the water.  Here it produces several long-stalked, oblong leaves which float on the surface and help to buoy up the stem.  From the nodes more branching roots hang down in the water and help to supply the large plant with water and mineral salts.

If we examined the leaf, we should see that at its base is a cylindrical, membranous sheath which embraces the stem.  This is actually the leaf stipule, but it is known as the ochrea.  We should notice that the leaves are shiny above and it is on this surface that the stomata are found.

The flowers are produced from the summit of the stem in dense spikes supported on tall, stout peduncles.  Each flower consists of a pink, bell-shaped corolla, from the base of which arise four stamens whose long filaments project beyond the mouth of the bell.

The ovoid ovary is terminated by two erect styles with stigmas like pin-heads.  The surface of the ovary has a depression all round it and in this nectar is secreted.

The stamens mature before the stigmas and in a young flower the styles are twisted together, but when all the pollen is shed, the anthers drop off and the two styles spread apart.  A bee on visiting the flower must push its head into the corolla to reach the nectary and will leave transported pollen upon the stigmas.  Self-pollination is obviously impossible.  To ensure that bees will visit the flowers, the conspicuous spikes are sweetly scented.

THE INHABITANTS OF THE LOCH FRINGES

Having described the inhabitants of the Highland lochs, we must now make the acquaintance of some of the interesting plants that inhabit the shallow edges and marshy shores of these delightful stretches of water.  The delta-like areas formed around the mouths of small streams which run down into these lochs are especially rich in littoral plants.

In these places we shall find the stately Yellow Iris, with its large, handsome flowers, the beautiful fringed chalices of the Bog-bean, the bright blue spikes of the Water Lobelia, the large Water Plantain with its spikes of tiny flowers and many others, such as the Water Avens, the Marsh Cinquefoil and the Meadow Sweet, which have been described elsewhere in this book.

They include many interesting plants and among them we shall find many adaptations to habitat and insect visitors.  A visit to the shores of any Highland loch is very illuminating, offering as it does a chance to study Nature under ideal conditions and amid beautiful scenery.  All these large sheets of water have a beauty of their own enhanced by the floral wealth along their shores.

Let us commence with a typical inhabitant of the shallow loch fringes, the Water Lobelia.

The Water Lobelia (Lobelia Dortmanna)

This species is quite a common plant in the shallow water around the shores of many Highland lochs.  In Speyside it is very common in all the many lochs of Rothiemurchus and it is there that I first made the acquaintance of this lovely plant.

The Water Lobelia usually forms a carpet of green leaves beneath the surface of the water, sometimes completely submerged with a part of the leaves above the water.  The individual plant has a root system of fine roots which anchor the plant in the mud and stones at the bottom of the lake.  The rootstock is crowned by a tuft of bright green, radical, cylindrical leaves, which are very peculiar, for they are formed of two hollow tubes placed side by side.  As we know, a tube is one of the strongest forms of architecture and thus, the leaves of the Water Lobelia are well adapted to withstand currents and also the strong waves which often beat upon the shores of the Highland lakes.

From the tufts of leaves arise leafless flower stalks which attain a height of from nine inches to one foot.  They are terminated by a spike of three or four distant flowers, the flower stems consisting of a single cylindrical tube.

The flowers themselves are peculiar structure.  They possess a tiny green calyx from which protrudes the long tubular corolla which is slit open to the base on the upper side.  The tube is more or less two-lipped at the entrance and irregularly lobed.

These flowers show us the transition from the perfect bell-shaped corolla of the Bellflowers to the strap-shaped tubular florets of the Composites.

At the base of the corolla-tube we shall find the ovary and the nectarines.  The ovary is surmounted by the long hairy style, while in a newly-opened flower we shall find that the anthers of the five stamens are pressed close against the style.  At this stage the three stigmatic surfaces are pressed close together so that there is no chance of self-fertilization.  At a later stage, when the stigmas are well clear of the anthers, the filaments retract and pull the anthers away from the style towards the base of the tube, while the three stigmatic lobes unfold to expose their receptive surfaces.

From this description it is obvious that a bee visiting a flower will leave pollen upon the stigmas at the entrance and then, as it pushes its head into the tube, it will become dusted with pollen still adhering to the hairy style.  In this species, the flower is so well adapted that self-fertilization is well nigh impossible.

Bees, whose favourite colour is blue, are the chief benefactors as their tongues alone are long enough to reach the nectarines, and as they must push their heads into the tube to do this, they become dusted with pollen.

At the same time, their habit of commencing at the bottom of a spike of flowers mans that they will visit the older pistillate flowers at the base of the spike first, thus assuring pollination with pollen from a distinct plant.

Thus do we see how amazingly bees and flowers have evolved for the common good of each other.

The Bog-bean (Menyanthes trifoliata)

Along the edges of lochs, tarns and streams, especially in shallow muddy places, where inflowing streams have formed swampy deltas, we may find this strange, beautiful, little plant.

I first had the pleasure of studying its lovely flowers in a little pond covered with Pondweed and fringed with Irises, Lousewort, and Marsh Cinquefoil, on the edge of the sterile Moor of Granish in Speyside.  Since then I have found it in many different parts of the Highlands.

It is a typical aquatic plant with a thick rootstock which creeps in the mud at the bottom of the loch, sending out dense growth of matted roots into the mud in search of food and anchorage.  The rootstock sends up a thick stem which in deeper water may float upon the surface, but in shallow water creeps along the mud.  The stem produces a dense tuft of leaves which have along, thick stalk and a long, thick stalk and a long, white sheathing base.  The leaves consist of three large ovate leaflets, which are quite smooth, as in most aquatics, and usually stand erect above the surface of the water.  From the base of the tuft of leaves arises the thick flowerstalk which may attain as much as one foot in height.  It is leafless and crowned by a raceme of beautiful white flowers, which are often delicately tinged with pink.

The individual flower is an interesting and beautiful structure.  It consists of a short green calyx from the base of which arises the bell-shaped corolla crowned by five deeply cut lobes which usually recurve.  The outer surface of the corolla is of a reddish hue shading to white and is quite smooth, but within the petals are covered with a thick mantle of hairs.  These hairs prevent crawling insects and small insects with short tongues from reaching the nectarines at the base of the bell.  As these insects would otherwise steal the nectar, and by their smallness miss the anthers and stigmans, they could not benefit the plant.

If we examine flowers from different plants, we find that in some the style is long, the stigma occupying a position at the mouth of the bell and that in these cases the stamens only arise half-ay up the inside of the bell.  In others, the stamens are long, reaching the mouth of the bell while the style is short.  This is the same construction as in the primrose and is another example of heterostylism.

As with that flower a full yield of seed is only obtained when pollen from the long stamens is transferred to a long-styled pistil and vice-versa.  Any pollen transferred from the long stamens to the short-styled pistil will be almost infertile.  Thus has the Bog-bean ensured cross-pollination.  As this plant forms large colonies along the loch shores, the chance of a legitimate transfer of pollen is great, for many flowers of the two types will be found in close proximity.

Bees are the chief visitors to this plant as only they possess a tongue long enough to pass between the hairy filaments and reach the nectarines at the base of the bell.

The Greater Skull Cap (Scitellaria galericulata)

One summer’s day I was exploring the boulder-strewn shore of Loch Lomond, between Luss and Tarbett, where the craggy mountains drop almost sheer to the water’s edge and where the shapely peak of Ben Lomond dominates the landscape.  Here, where one obtains charming views across the loch to Rowardenan and down the island-studded lower portion towards Balloch, I first discovered the Greater Skull Cap.

A little stream came tumbling joyfully down the rocky hillside rushing into the loch by a verdant mossy-green channel.  Here large tufts of the Greater Skull Cap with its beautiful deep blue flowers grew out from the chinks of rock along the cool water course, and I was able to watch a large bumble-bee diligently visiting each flower, unaware of the interest being taken in it.

The Skull Cap genus (Scutellaria), a member of the Labiate Family, is large and widespread although in Britain we have but two native species.

The Greater Skull Cap is a fairly frequent plant in damp rocky places beside streams and rills, although I have not found it very often in the Highland area, it is certainly common enough along the shores of Loch Lomond.

It possesses a creeping rhizome which gives off fine roots which are well able to push down into the crevices of the damp rock on which it loves to grow.  It sends up many weak stems which often hang down gracefully and attain about one foot in length.  The stems are clothed by many pairs of sessile leaves which are ovate-lanceolate in shape and slightly toothed and covered with a slight down.  In the axils of these leaves arise pairs of beautiful blue flowers which are produced along the greater part of the stem and they all face in the same direction.  Thus the inflorescence is in reality a long interrupted spike.  The corolla consists of a long tube which is very slender in the lower part, but is much wider above, in order to permit the bee to enter the flower.  It is terminated by a pair of lips, the upper one of which is concave, whilst the lower one is three-lobed.

These flowers, which are typical of the Labiate Family, are adapted for bees, especially the larger types.

If we dissect a single flower, we shall find that the ovary is situated at the base of the slender tube where the nectarines are also situated.  The ovary is surmounted by a long slender style which is curved near the apex in order to fit into the concave upper lip.  The two stigmatic surfaces project downwards.  The four stamens lie parallel to the style in the roof of the mouth, but two to them are shorter than the other two and lie farther back.  The concavity of the upper lip protects the anthers beautifully against rain and damp.

At first the anthers only are mature, but later after the pollen has been shed the stigmas become receptive.   A bee on visiting the flower alights on the lower lip, and forcing its head into the mouth of the tube to reach the nectar at its base, becomes dusted on the top of the head and the back by the anthers in the upper lip.  On going to an older flower with mature stigmas, it is obvious that its pollen-covered head and back must come in contact with the stigmas which are in the same position as the anthers occupied.  Thus cross-pollination is assured.

As only the larger bees have long enough tongues to reach the nectar, they are the only visitors.  From their habit of visiting the lower flowers of a spike first, i.e. the older flowers with mature stigmas, it is obvious that they will always pollinate these flowers with pollen transported from another plant or stem which is just what the plants wants.

This, then, is another example of how amazingly flowers are adapted to their insect visitors and how hard they strive to avoid self-fertilization.

Yellow Iris (Iris Pseudacorus) 

Most of us must be familiar with the stately, purple, blue and white Irises, which form such splendid beds in most ornamental gardens.  Their erect posture and their sword-like leaves enhance their military bearing, whilst their velvety petal rival those of the Orchid in colour and form.

Our garden Irises are, for the most part, natives of dry countries and do not need more water than the other inhabitants of the garden.  In this our present subject is very difficult as it can only flourish where it can obtain abundant moisture.

The Yellow Iris is a very common plant throughout Britain and is quite common in the lower parts of the Highlands.  It prefers the shallow fringes of lochs, the edges of streams and swampy places, whoever the soil is soft enough for its roots to penetrate and where the soil is not too acid.

I found it one June growing in profusion within a stone’s throw of the sea, forming a dense mass of vegetation along the muddy edge of Loch Morar, just where that delightful sheet of water hurls itself in showers of spray into the Morar River to dash in impetuous glee into the nearby sea.  From this charming spot one looks out over the silver Minch to the sharp points of Rum and romantic Coolins, and if the time be near sunset and the sun is descending in crimson glory, few of Nature’s master pieces can rival the magnificence of the scene.

The Yellow Iris is a perennial and forms extensive colonies.  Its main stem is a thick, creeping rhizome which lies upon the surface of the mud and is usually immersed several inches in the water.  It gives off many thick white roots, which penetrate deeply into the mud.

If a rhizome is dug up and a transverse action is cut, it will be found to consist of a sold white tissue containing many oval yellowish spots.  These spots represent the vascular bundles of the rhizome and contain the vessels by which water, salts, and other food products are distributed to the various parts of the plant.  If a drop of iodine is placed upon the section a deep blue coloration will be given, due to the abundant starch grains stored up in the cells.  During the winter this store of food remains safely at the bottom of the lake, where frost and cold cannot attack it.

The rhizome sends out branches and in the course of time large areas are colonized by a single plant.  On decay of the intervening portions of the rhizome, the daughter plants become independent of the parent.  This is a means of reproduction by vegetative process.

In the spring, when the water begins to get warmer, a large bud at the extremity of the rhizome commences to swell and, fed by the starch in the cells, it sends up a bunch of radical leaves.

The sword-shaped, very acute, rather glaucous leaves attain as much as three to four feet in height and are remarkable for the fact that they possess no under surface, but stand erect.  They are very strong and are not likely to be damaged by strong winds, and as they have a large surface area, they are very efficient assimilating organs.

From the midst of the leaves arise one or several tall, stout, cylindrical stems upon which the flowers are borne.  They bear very large, leafty bracts very similar to the foliage leaves in form, and from the upper two or three of which are produced the large showy flowers.  Whilst young the flower bud is safely hidden in the hollow sheathing base of the leaf.

Each flower, when in bud, is beautifully wrapped up in membranous, translucent, boat-shaped bracts, the one enveloping the other, but as the flower develops, it gradually burst out of the sheath.

The fully-opened bloom is a very beautiful structure indeed and can well claim a place among our most lovely flowers.  Only in the Orchid Family do we find such a modification of structure and such nice adaptation to insect visitors.

The flower is large and complicated.  The corolla (or as it is called, the perianth) consists of six petals in two whorls, of which the three outer ones have a large, broad, ovate blade which is bright yellow in colour. The blade narrows into along claw which is united to the claws of the inner petals to form a long tube.  The lower portion of the blade has a brown hart-shaped mark at its base, with deeper yellow colouring within.  Brown veins run down to the base of the claw and guide the bees to the entrance of the perianth tube.  These outer petals curve down gracefully and form a fine landing stage for insects.

The three inner petals are very small and much less conspicuous, the blade being narrow, spoon-shaped, and bright yellow in colour.

If we examine the flower, we shall see that in addition to the petals there are three large, erect, conspicuous, bright yellow, petal-like objects which curve upwards from the centre of the flower.  These structures are actually the styles and stigmas, the tip of the style being expanded into a much-cut fringe below which and on the under side of which, is a tiny, raised ridge which is the actual stigma.

Each flower contains three stamens, whose anthers are produced under the over-aching style which protects the pollen from rain and damp.

The ovary is a smooth, cylindrical structure at the base of the perianth tube and is concealed in the bracts.  Nectar is produced by the glandular summit of the ovary and it often almost fills the perianth tube.

To what end has this beautiful, complicated structure been evolved?  This is best answered by gong to the nearest loch-side in June and watching the bumble-bees at work.  As we watch a particular bloom, we may be rewarded by the flash of closing wings as the large insect alights upon the broad outer petal.  Without wasting any time and guided by the brown veins it pushes its head down between the overhanging style and petal, any pollen upon its head and back being scraped off by the ridge-like stigma.  The bee then brushes its back against the anthers.  By this time it can push its long proboscis into the perianth tube and suck up the nectar.  It then flies off to the next bloom with a good cargo of pollen upon its back ready for the next stigma that it touches.  Thus the flower has assured cross-pollination.

After fertilization the ovary swells to form a large ovoid capsule which splits into three divisions to display the bright, orange-red seeds.

Purple Loosestrife (Lythrum Salicaria)

This beautiful plant is confined mainly to the western Highlands and does not penetrate far into the northern Highlands.  It is surely one of the loveliest denizens of our marshlands, its tall, purple spikes dominating the loch shores, river and stream sides and the wet meadows in full summer.

It is a perennial and possesses a tough rhizome which becomes quite thick and woody with age and is anchored strongly by its many, tenacious, spreading roots.  Each year the flowering shoots die down, the stems of the next season arising from buds produced upon the underground rhizome during the autumn.

The stout, flowering stems, which branch above, reach two or three feet in height and are clothed with opposite pairs of long, lanceolate, soft downy leaves which clasp the stem by their bases.  The whole the upper part of the stem and branches is occupied by a handsome spike of reddish-purple flowers arranged in dense whorls, which are so close together as to give the illusion of a continuous spike of flowers.  A pair of leafy bracts spreads out from beneath each whorl.

The flowers are remarkable, not only for their beauty, but also for the fact that it was from careful study of this plant by Darwin that it assumed an important place in this theory of the origin of species.

The flowers are remarkable, not only for their beauty, but also for the fact that it was from careful study of this plant by Darwin that it assumed an important place in his theory of the origin of species.

The flowers possess a cup-shaped calyx-tube from the summit of which six or seven teeth project.  It is usually twelve-ribbed, each rib being covered with long, upward-pointing hairs.  From the top of the calyx-tube arise five, six or seven spreading, narrow, purple petals which have deep red veins acting as honey-guides.  The twelve stamens spring from the calyx-tube in two whorls, the stamens of one whorl being longer than those of the other.

In some plants one set of stamens is short and the other intermediate in length; in others one set is intermediate and other is long; whilst in other one set is long and the other is short.

From the bottom of the calyx-tube arises the conical ovary, terminated by the style with its knob-like stigma.  Around the base of the ovary is a glandular ring which secretes nectar.

Corresponding to the three different sets of stamens, we have three different styles, i.e. short, intermediate and long, but we should also remark that a short style does not occur in a flower with short stamens, nor an intermediate style in a flower with intermediate stamens and similarly in the case of the long style.

Having plucked three spikes, each of different type, let us carefully examine the pollen and we shall find that that of the long stamens is large-grained and green in colour, whilst that of the short stamens is yellow and small-grained, the medium stamens having pollen of an intermediate type.

A bumble-bee visiting a long-styled flower must alight upon the stamens and style as no other landing stage is offered to it, and on so doing its hairy abdomen touches the stigma.  It then pushes its head into the flower, brushing the medium stamens with its thorax, whilst its head touches the short stamens in the calyx-tube.  If it now visit’s a short-styled flowers, its abdomen will be covered with pollen from the long stamens, its thorax from the medium ones, whilst as it pushes its head down the calyx-tube, it will touch the stigma hidden within and will leave upon it pollen from the short stamens of the flower previously visited.

If we catch one of these bees and examine its under surface, we shall see that its abdomen is colored green with pollen from long stamens.  Its head is covered with yellow dust, whilst its thorax is greenish-yellow, these colours corresponding to the different lengths of stamens.

My readers who have had the patience to follow me thus far must be wondering why such a complicated plan has been evolved.  Darwin asked himself the same question over eighty years ago and obtained the answer by careful experiments.  He proved that without insect visitors no seed was set.  He also shoed that in a long-styled flower very little fertile seed was set if the stigma was pollinated with pollen from short or medium stamens.  Abundant fertile seed was set, however, if the stigma was pollinated with pollen from long stamens.  He obtained similar results in the case of short and medium styles.

Now through the peculiar arrangement of the flowers cross-pollination is practically certain and there is a three to one chance of being arrived at. We can realize how marvelously insects enter into the flower’s plan and we can realize the joy of Darwin when his months of careful research were so amply rewarded.

OTHER PLANTS OF THE LOCH FRINGE

Many and varied plants compete with each other for the limited space available in the shallow waters at the loch’s edge, among them being many tall grass-like plants.

Here we shall find the tall, stalwart Cat’s Tail or Reedmace (Typhalatifolia). This plant, which forms dense masses of stems and leaves on the marshy edges of many lochs and ponds, has a thick, creeping rhizome giving rise to erect stems, often over six feet in height, and clothed with many very long, sheathing, grayish-green leaves.

Owing to the height of these plants, the water in which they live is in deep shade, and hence very few plants can thrive in a colony of Reedmace.

The flowers are produced in the well-known club-shaped ‘bullrush’. This is a huge spike of small flowers, the upper portion of which consists of stamens, the lower portion of ovaries surrounded by tufts of soft, brown hair.  They are wind pollinated.

Another plant of this ‘Reed Zone’ is the Erect Bur-reed (Sparganium erectum), a close relative of the Floating Bur-reed already described.  The rootstock gives rise to long, fleshy runners which creep long distances in the mud at the bottom of ponds and lakes.

The stem attains two or three feet in height and is covered by long, spreading, narrow leaves which are triangular in cross section.

The wind-pollinated flowers are produced on naked branches in spherical, sessile inflorescences.  The upper consist of male flowers only, the lower ones of females only.

Another common inhabitant is the Common Water Plantain (Alisma Plantago-aquatica).  It possesses a very short, corm-like rootstock, which is rooted in the mud by thick, fleshy roots.  From the summit of the corm buds are produced from which spring the leaves and flowering stalks.

The leaves are produced on very long petioles which support the large, ovate, deep green, smooth blades in the air well above the surface of the water.

From the midst of the radical leaves arises a tall upright stem often attaining three feet in height.  This develops a complicated and rather beautiful inflorescence, in the upper part of which whorls of branches are given off, and from each of them a further whorl is produced, the whole forming a pyramidal panicle clothed in hundreds of dainty, pale rose flowers.

The whole plant, with its masses of bloom and large, long-stalked leaves, is a quite distinctive and characteristic plant and cannot be confounded with any other member of the loch flora.

Each flower resembles that of the Ranunculus although actually widely separated from that plant.  The calyx is formed by three concave green sepals, the corolla of three rose-colored petals of a very delicate texture and with a yellow spot at the base.  The ovary resembles that of  a Ranunculus very closely and is surrounded by a ring of stamens.  The flowers produce nectar and are visited by small bees and flies.

Several species of real Rushes (Juncus) occur on the lake shores, the Common Rush (Juncus communis) being very abundant.  The tall, cylindrical, smooth, green stems each producing a dense panicle of brown flowers near the summit are too well know to warrant a close description.

The rootstock gives rise to long, creeping runners which produce further tufts of stems and thus new plants are produced vegetative.

It is remarkable in possessing no actual leaves, these being reduce to brown scales at the base of the stems.  The brown star-shaped flowers, with their six ovate, pointed sepals, their three to six stamens and their three feathery styles, are constructed for wind pollination.

A similar plant is the Hard Rush (Juncus effuses), which may be distinguished by the deeply channeled glaucous stems of a harder and stiffer texture than those of the Common Rush.  It is almost equally common.

A rather different plant is the Jointed Rush (Juncus articulatus) which has been divided into several sub-species and varieties. The stems are weak and spreading and are clothed by sheathing, cylindrical leaves.  If these be dried, they will be seen to have a jointed appearance, as they are divided internally by cross walls of pith.

The flowers are produced in large, terminal panicles and are similar, in structure, to those of the Common Rush, but always possess six stamens.  It is found on the damp shores of lochs and ponds as well as in marshes and bogs.

We may also find the strange little Toad Rush (Juncus bufonius). This plant is an annual and forms a dense tuft of pale green, weak stems with several short, cylindrical, radical leaves at their base.  The flowers, which are usually solitary or may be three to four together upon the branches, are pale green in colour and remarkable for their very pointed perianth segments.

Many species of Sedges may be found along the lake shores.  The Club Rushes (Scirpus) are conspicuous in forming very large colonies.  Each plant has a long, creeping rootstock giving rise to tufts of upright, cylindrical, green stems without leaves.  The green stems are the photosynthetic organs, containing chloroplasts, as do the stems of the Common Rush.

The wind-pollinated flowers are produced in dense, ovoid heads at the summits of the stems.  They contain three stamens on long slender filaments and two spreading feathery styles.  The genus Scirpus contains a large number of species which are very similar to one another.

The ordinary Sedges (Carex) are well represented and include a vast number of species which are beyond the scope of this book to describe. 

Among common grasses may be mentioned the Flote-grass (Poa-fluitans) whose weak stems creep over the mud or float upon the water, the long pale green leaves being usually floating.  The flowers are produced in a long spike of spike lets each containing eight to twenty flowers.

The Common Reed (Arundo Phragmites), a stout perennial often over six feet high, forming large colonies, may often be met with.  The stems are covered by long, broad leaves resembling those of a Bamboo.  The panicles of flowers are very large and conspicuous, and are composed of hundreds of purple-brown spike lets.  As the seed ripens, it becomes surrounded by a mass of silky hairs which give the panicle a silvery appearance and act as parachutes when the seeds are born away upon the autumn gales. 

The Invertebrate Fauna of the Inland Waters of Scotland
Part III. By Thomas Scott, F.L.S. Loch Morar, Inverness-shire (1893) (pdf)