ON FLOWERS OF THE WATER
The first plant--Seaweeds in hot baths--Breaking
of the meres--Gory Dew--Plants driven back to
the water--Marsh plants--Fleur-de-lis--Reeds and
rushes--Floating islands--Water-lilies--_Victoria
regia_--Plants 180 feet deep--Life in a pond, as seen by
an inhabitant--Fish-farming--The useful Diatom--Willows
and Alders--Polluted streams--The Hornwort--The Florida
Hyacinth--Reeds and Grass-reeds--The richest lands in the
world--Papyrus of Egypt--Birds and hippopotami--Fever and ague.
What was the first green plant? When was the surface of the earth
first covered with flowers? Such questions are quite impossible
to answer. We cannot even tell how plants ever came to exist on
the earth at all. Wonderful as are the stories of the hardihood of
bacteria, of spores, and of seeds, it is not possible to imagine that
they could have been whirled or drifted through infinite space to
this particular planet.
Yet it is at least probable that the first real plant on this world
was a seaweed or alga.
In Germany and Austria there are certain springs in which the water
coming from immense depths is at an exceedingly high temperature.
These hot springs are used as natural hot baths, and have many
interesting peculiarities. Amongst others there is the fact that
certain seaweeds or algæ are found luxuriating in the hot water. Some
of these can even live in springs with a temperature of 176° F.!
Such algæ may have remained living in exceedingly hot water ever
since that long distant time, the very first of all the geological
periods, when there was no distinct separation betwixt land and
water, and when the waters which were below the firmament had not
been separated from those which were above it. Then the world seems
to have been all fog and mist at a very high temperature.
But all theories on the origin of the world might be briefly
summarized by the last nine words!
At any rate, the first plant was almost certainly a seaweed or alga
not unlike those which produce the so-called "breaking of the meres."
At some seasons the water of certain lakes, usually quite clear
and pure, becomes discoloured, turbid, and everywhere crowded with
multitudes of tiny, bright, verdigris-green specks. The fish at
once begin to sulk, refuse to take the fly, and live torpid at
the bottom of the water. The minute green particles consist of a
certain seaweed or alga. Mr. Phillips put the head of a common pin
in the water so as to obtain a very small drop. When placed under
a microscope, this minute amount of water was found to contain 300
individual algæ.[102] This was in Newton Mere (Shropshire), and as
this lake extends over 115 acres, it is possible to imagine the
millions upon millions of algæ which must have existed in it. The
names of these seaweeds are many thousand times longer than the algæ
themselves, and it is not really necessary to give them. One of
them, however, _Aphanizomenon flos-aquæ_, has been noticed "tingeing
with its delicate green hue the margin of the smallest of the Lochs
Maben, in Dumfriesshire."[103] Yet it is not so big as the dot on
the _i_ in its name. Many other cases have been recorded of lakes
that were coloured sometimes a "pea-green," or even brown or red by
similar tiny little seaweeds. As we shall see, the water of such
lakes generally contains a very large amount of suspended or floating
vegetable life.
[102] Cooke, _British Freshwater Algæ_, on the authority of
Phillips, _Trans. Shropshire Natural History Society_.
[103] Dickie, _Journal Bot. Soc. Edin._, vol. 3, p. 79.
Another curious appearance is _Gory Dew_. Patches of a deep blood-red
or purple colour are found on the ground or on walls. They have just
the appearance of recently-shed blood. This also is due to an alga
(_Porphyridium cruentum_). Dr. Cooke quotes from Drayton as follows:
"In the plain, near Hastings, where the Norman William, after his
victory found King Harold slain, he built Battle Abbey, which at
last, as divers other monasteries, grew to a town enough populous.
Thereabout is a place which, after rain, always looks red, which some
have attributed to a very bloody sweat of the earth, as crying to
Heaven for vengeance of so great a slaughter."
The ordinary "Rain of Blood" which appears on _not too fresh_ meat,
and looks like minute specks of red-currant jelly, is due to one of
the Bacteria (_Micrococcus prodigiosus_).
The original algæ or seaweeds probably had descendants which migrated
to the land and eventually after many geological periods became
our flowering plants and ferns. But the earth has become so richly
supplied with plants of all sorts and kinds that it is now by no
means easy for any plant to find a roothold for its existence. So
that a considerable number have been forced back to the water, and
have accustomed themselves to live in or even under water in company
with their lowly cousins, the seaweeds, who remained below its
surface.
These water plants are very interesting. They are always competing
with one another. There is a perpetual struggle going on round every
pond and loch, and by every river side.
If you look carefully round the edge of a loch or pond which lies in
a grass field, certain series of plants are generally found to follow
one another in quite a definite way. The first sign of water in grass
is generally the presence of moss or "fog" between the grass-stems
and the appearance of what farmers call the "Blue Carnation Grass."
It is not a grass but a sedge (_Carex glauca_ or _C. panicea_) with
leaves rather like those of a carnation. A little nearer the border
of the pond, there may be a tall coarse grass (_Aira caespitosa_
or _Festuca elatior_). Next there is almost certain to be a fringe
of Rushes. Where the Rushes begin to find the ground too wet for
them, all sorts of marsh plants flourish, such as Water Plantain,
Cuckoo-flower, the Spearwort Buttercup, Woundwort, and the like.
As soon as the actual water begins, one finds, whilst it is still
shallow, the Flag series of yellow or purple Irises, Bogbeans, Marsh
Cinquefoil, Mare's Tail, and Sedges of various kinds. In this part
the water ranges from an inch or two to about eighteen inches deep.
The Flag or Iris is a very common and yet interesting plant. It
has a stout, fleshy stem lying flat on the mud, and anchored to
it by hundreds of little roots. The flower is the original of the
Fleur-de-lis, or Lily of France, which took the fancy of the King of
France as he rode through the marshes towards Paris. (It is true that
there are some unromantic authors who hold that the emblem was really
intended to represent a frog or toad!)
The flower consists of three upright petals and three hollow sepals,
which make so many canals leading down to the honey, and roofed over
by an arched and coloured style. As the bee hurries down the canal
to its nectar, its back is first brushed by a narrow lip-like stigma
and then dusted with pollen. The leaves overlap in a curious way,
and, when they have withered, their stringy remains serve to protect
the fleshy stem. _Orris root_, which is used in perfumery, is the
stem of the _Iris florentina_.
Most of the other plants in this Flag series will be found to
have prostrate main stems growing under the water, but giving off
flowering and foliage stems which stand up above it, so that the
leaves and flowers are above the surface.
In the next part of the pond, where the water is from eighteen inches
to nine feet deep, masses of reeds will be found usually swaying,
sighing, and whispering in the wind. There are many kinds, such as
Bulrushes, Phragmites, Horsetail, Scirpus, etc. It seems to be the
depth, the exposure to wind, the character of the soil, and other
unknown factors, that determine which of those will be present. All
of them are tall, standing well above the water; their main stem is
usually flat on the bottom of the pond, or floating horizontally in
the water, but giving off many upright branches.
Floating islands are often formed by some of these horizontal main
stems breaking off and being carried away. Those Chinese who possess
no land make floating islands of such reeds for themselves, and grow
crops on them. There are hundreds of such islands in the Canton River.
[Illustration: _Stereo Copyright, Underwood & Underwood_
_London and New York_
A LEAF RAFT
Victoria Regia, the giant water-lily of the Amazons. Those shown
are in a public park in Minnesota and are able to support the
weight of a child. In their native home the leaves are said to be
ten feet in diameter.]
Beyond the reeds, one sees the large flat, floating leaves and
beautiful cup-like white or yellow flowers of the Water-lilies. They
grow in water which is not more than fifteen feet deep. Their long
stalks and leaf-stalks are flexible and yield readily, so as to keep
the flowers and leaves floating. There are narrow submerged leaves
as well. The actual stem of the White Water-lily is about three
inches in diameter, and stout and fleshy. It is full of starchy
material, and lies upon the mud deep down at the bottom of the pond.
There are many advantages in the position of the flowers, for bees,
flies, and other useful insects can reach them easily, but slugs,
snails, and other enemies cannot do so. The little seeds have a
curious lifebelt-like cup, which enables them to float on the surface.
Of course, our own British water-lilies cannot compare with the
magnificent _Victoria regia_ of the tropics. Its petals are white
or pink on the inside, and its gigantic leaves, six feet or more in
diameter, can support a retriever dog or a child. There used to be
some of them at Kew Gardens. A curious point about these enormous
floating leaves is that they are covered with little spiny points on
the under side and at the margin; that is probably to keep some sort
of fish from nibbling at the edges.
But to return to our pond. Beyond the water-lily region and so long
as the water is from twelve to twenty-four feet deep, Pondweeds are
able to grow, and their leaves may be seen in the water, whilst their
stalks stand up above the surface so as to allow wind to scatter the
pollen.
This depth of twenty-four feet seems at first sight very great, but
it is a mere nothing compared with the regions entirely below the
water, where certain Stoneworts (_Chara_) and Mosses have been found
flourishing. The former has been dredged up from depths of ninety
feet, and a little moss was discovered in the Lake of Geneva growing
quite comfortably at a depth of 180 feet below the surface.
But it is quite impossible to appreciate the wonder and beauty of the
life in a pond unless by a strong effort of the imagination.
Suppose yourself to be a fish two or three inches long, and
accustomed to the dim, mysterious light which filters down through
the water from the sky above. Every here and there great olive-brown
leaf-stalks and stems cross and, branching, intercept the light.
Everything, the surface of the mud, the stems and branches of the
submerged water-plants, is covered by an exquisite golden-brown
powder, which consists of hundreds and thousands of "Diatoms." Here
and there from the Pondweed and other stems hang festoons or wreaths
or threads of beautiful green Algæ. Little branching sprays of them,
or perhaps of the brown kind, are attached here and there to the
thick stems.
Even the very water is full of small, floating, vivid green stars or
crescents or three-cornered pieces which are free floating Algæ or
Desmids. Other diatoms are also free or swim with a cork-screwing
motion through the water. Great snails and slugs crawl upon the
plants, and weird large-eyed creatures, with a superfluity of legs
and an entire absence of reserve as to what is going on inside their
bodies, skirmish around. So that such a pond is full of vegetable
activity. The free-swimming diatoms and desmids make up the food of
the snails and crustaceans. These latter in turn are the food of
fishes.
It is even possible to-day by carefully stocking an artificial pond
with water plants, by then introducing Mollusca and Crustacea, and
finally by the introduction of "eyed ova" or fry of the trout, carp,
or other fishes, to produce a regular population of fishes which can
be made more or less profitable, and the process can be spoken of
as "fish-farming." Unfortunately there are a great many gaps in our
knowledge as to what fish actually feed on, and we know even less
about what the Mollusca and Crustacea require.
There is, however, a distinct annual harvest of these minute
seaweeds, of which different sorts appear to develop one after the
other, just as flowering plants do. The two months January and
February, which are almost without flowers, are also those in which
most of these minute vegetables take their repose in the form of
cysts or spores.
But these diatoms are too important and too interesting to be
dismissed in such a cursory manner. Each consists of a tiny speck
of living matter with a drop or two of oil enclosed in a variously
sculptured flinty shell. They have, in fact, been compared to little
protected cruisers which pass to and fro in the water and multiply
with the most extraordinary rapidity.
If you (1) use dynamite to blast a rock, (2) if you employ a
microscope or telescope, (3) if you paint an oil picture, (4) if you
make a sound-proof partition in a set of offices, the probability is
that it has been necessary to use the substance diatomite in each
case. This consists of the accumulated shells of myriads of diatoms.
Nor does that represent by any means the whole of the usefulness of
these tiny seaweeds. The oil shales, such as occur in Linlithgowshire
and elsewhere, are supposed to be the muddy, oily deposits of such
ponds as we have endeavoured to describe. The oil found in the shales
was probably worked up by these diatoms in long-past geological ages.
It may be used to-day either (1) to drive motors, (2) to light lamps,
(3) to burn as so-called "wax" candles, (4) to eat (as an inferior
sort of chocolate cream).
Interesting as these diatoms are, it is not really possible to
understand their structure without the use of a microscope, so that
we must pass on to another side of the activity of water plants.
Let us, for instance, notice some of the ordinary plants to be found
along a riverside. Willows and Alders are the ordinary trees, because
they are specially fitted to stand the danger of being regularly
overflowed. They easily take root, so that branches broken off and
floated down are enabled to form new trees without much difficulty.
In the United States, it has become a custom to plant Willows along
the banks, because they are then not so liable to be broken down and
worn away. Yet when a big Willow tree has become undermined, the
weight of the trunk may cause it to fall over towards the water, so
that a large section of the bank may be loosened and serious damage
may be done if it is torn away by a heavy flood.
Amongst such Willows, should be mentioned the "cricket bat" kind,
which has to be grown with the very greatest care, and of which a
single tree may be worth £28.
Many of our rivers are, alas, sadly polluted by artificial and other
impurities which kill the fishes and destroy the natural vegetation.
When this happens a horrible-looking whitish fungus (_Apodytes
lactea_) coats the stones and banks under water and the water swarms
with bacteria. This fungus and the bacteria are really purifying the
water, for they break up the decaying matter in it.
The oily or slimy character of the outside skin of all submerged
plants is of very great importance to them. It allows the water to
glide or slip over them without any friction.
Still keeping to our river bank, let us look for submerged plants.
What is that dark green feathery plume? It is the Hornwort
(_Ceratophyllum_) gently wriggling or moving from side to side. It
has probably never been still for a moment since it first began
to grow. Take it out of the water, and it collapses into a moist,
unpleasant little body, but as soon as it is put in its natural
element again it is seen to have a thin flexible stem along which
there are circles of curved, finely divided leaves. Watch it in
the water and one is filled with astonishment at the perfection of
the shape, arrangement, and character of the leaves, which enables
them to hold their place even when a flood may cover them with an
extra twenty feet of water! The same sort of leaf, but with great
difference in detail, is found in the submerged Water Crowfoot,
Water Milfoil, Potamogetons, and others which live under the same
conditions.
If it were the St. John's River, we might see that extraordinary
Florida Hyacinth which has swollen, gouty-looking leaf-stalks,
and grows with such extraordinary rapidity that it covers the
whole surface of rivers, choking the paddle-wheels of steamers and
destroying the trade in timber, for no logs can be floated down when
it covers the water. Its rosettes float on the surface, and are very
interesting to examine. If you upset one or turn it upside down in
the water, the "buoys" or swollen stalks act as a self-righting
arrangement, and it slowly returns to its proper position.
But in most rivers, one is certain to come across backwaters where
it is impossible to force a boat through on account of the reeds and
other marsh-plants.
There are places on the Danube where hundreds of square miles are
occupied by waving masses of the feathery-plumed Phragmites, almost
to the exclusion of any other sort of vegetation. Giant specimens of
it eighteen feet high have been observed.
The same reed occurs in North and South America and far up towards
the Arctic regions. At first sight it seems as if this was a mistake
of Nature; why should so much of the surface be occupied by this
useless vegetable? But it is necessary to say a little more about
its habits and its object in life.
The most interesting and curious point is the way in which it grows
in dense thickets; the main stem is really horizontal and below the
water, but it gives off a number of upright stalks. Now every flood
will carry in amongst the stalks quantities of silt and rubbish.
Those upright stems will sift the water: all sorts of floating
material, sand, silt, dead leaves, fruit, etc., are left amongst
them. So that such a marsh or bed of Phragmites is gradually, flood
by flood, collecting the deposits of mud, and the bed becomes every
year more shallow. At the edge of the marsh there is scarcely any
water visible, and grasses and other plants are beginning to grow
between the Phragmites stems. Eventually these latter are choked out,
and a marshy alluvial flat occupies the site of the old reed-bed.
So that the work of Phragmites is of the greatest possible
importance: it has to form those fertile alluvial flats which are
found along the course of every great river, and which are by far the
most valuable lands in the whole world.
Look, for instance, at the population of Belgium, Holland, and Lower
Germany, and notice how dense it is upon the alluvial flats where the
Meuse, Rhine, and other rivers approach the sea. It is just the same
in Britain. London lies on the great alluvial flats of the Thames,
Glasgow on the Clyde, Liverpool on the Mersey. In China it is the
Yang-tze-kiang valley (especially near its mouth); in India, the
Ganges, of lower Bengal, and in the Argentine the La Plata River,
which show the greatest accumulations of humanity. In every case it
is the rich flat alluvium, which is exceedingly fertile when drained
and cultivated, that has originally attracted so many people.
Lower Egypt is the gift of the Nile, but it is not so much the Nile
as these neglected water plants which made the rich lucerne, cotton,
and food crops of Lower Egypt possible. Amongst the Egyptian Reeds
one especially is of great importance. The _Papyrus antiquorum_,
ten feet high, has much the same habit as our Phragmites and other
water plants. It forms dense, almost impassable thickets, sometimes
completely occupying and choking a small valley, or leaving only
a passage, often changing and half choked, through a larger one.
This, with other plants, makes the "sudd" of the Nile, which is one
enormous accumulation of marsh plants and reeds floating on the water
and covering a length of over 500 miles.
It was from the Papyrus that the ancient Egyptians made their paper.
The stems are six to seven inches in diameter. "The pith of the
larger flowering stems ... cut into thin strips, united together by
narrowly overlapping margins, and then crossed under pressure by
a similar arrangement of strips at right angles, constitutes the
Papyrus of antiquity."
These great marshes and reed-beds are full of interest to
naturalists. The Fens of Lincolnshire and the Norfolk Broads show the
way in which water plants keep hold of the worn and travelled rubbish
of the hills, and prevent most of it from becoming useless, barren
sea-sands. These places, however, like the sudd of the Nile, and
the Roman "Campagna," have an evil reputation so far as climate is
concerned. This used to be the case even in lower Chelsea, in London
(where snipe were shot not so very long ago). It is as if Nature had
desired to do her own work in peace and without being disturbed, for
fever, ague, mosquitoes, and malaria are very common. Yet a certain
number of people always live in such places. In France, e.g., the
leeches in the great marshes near the Landes form a source of riches.
Such reeds also are or were the home of the hippopotamus, crocodile,
and other extraordinary animals. The extinct British hippopotamus
no doubt found in the Chelsea or other marshes a home as congenial
to its tastes as is the sudd of Egypt to its living descendants or
allies. In other places the enormous quantities of water birds,
myriads of ducks, geese, swans, regiments of flamingoes, snipe, and
the like, have called into existence peculiar kinds of industry in
fowling and netting that are not without importance. The decoys in
the Fens yield hundreds of birds for the London market, and the
duck-punts with their huge guns also bring in quantities of wild fowl.
But all this industry is very trifling compared with that of
Phragmites and its associates, who have strained from the water of
the Thames most of the ground on which London now stands.