PhotoSkeen and Co.Cinnamon Peeling in Ceylon
PhotoSkeen and Co.Cinnamon Peeling in Ceylon
PhotoSkeen and Co.
Cinnamon Peeling in Ceylon
Then, after being stripped from the branches, in someout-of-the-way forest-clad range of Burma, Celebes, South America, or Madagascar, these orchids are dried, put up in crates and packed off to London, where they are carefully cultivated in hot-houses and persuaded to flower. They may be worth sixpence or they may be worth £500 each, but no one can tell until they have flowered in London.
But the romance of the orchid-hunter is not exactly what we have to describe here. It is rather the romance of the life of the orchid itself.
It is perched high up on the branches of the tallest trees in the forest, exposed to sun, exposed to wind, and quite unable to gather either salts or rain from the soil. How, then, does it manage to live?
These orchids, it must be remembered, are only found in out-of-the-way and feverish, unhealthy places, where the aboriginal savages still lurk and endure a dreadful existence of hunger and starvation in dense tropical forests.
Now the word "dense" explains the whole story. Those forests are so thick, so full of giant trees and exuberant growth, that civilized man even to-day in 1906 can make nothing of them, and leaves them to the savage. The reason why vegetation is so luxuriant is simply that there are both plentiful moisture and a hot, tropical sun. That makes the life of the orchid possible, and also ensures malaria for the hunter.
It hangs out into the moist air long pendulous roots which act as so many sponges absorbing and soaking in moisture. The tremendous energy of growth covers bark and branches with creeping plants innumerable, with a profusion of moss, liverworts, and ferns such as we cannot imagine from our own experiences in this country. So the roots of our orchid find on the branches rich leaf-mould,and it lives happily and contentedly on the salts and moisture accumulated by the mosses and other plants. Its leaves are fleshy and succulent, rather like those of a desert plant, so that it can store up water against a season of drought.
These plants which grow in this way on other plants, do not, as a rule, greatly injure them, but many have not stopped at this stage. Take, for instance, the Gooseberry growing in the fork of an old tree. Some bird has been eating gooseberries and dropped the seed there. The roots of the gooseberry will grow down into the rotten part of the trunk. Earth and leaf-mould will accumulate there, and it is quite probable that the whole inside of the tree will decay away. The roots of the gooseberry will, if only indirectly, help in this decay.
But it is far otherwise with another set of plants—the Mistletoe and its allies. There is plenty of romance connected with the mistletoe. Dr. M. T. Masters says as follows: "The origin of the modern custom connected with mistletoe is not very clear. Like many other customs, its original significance is only guessed at. If known, perhaps, the innocent merriment now associated with the plant would be exchanged for a feeling of stern disapproval, and the mistletoe would be banished from our homes. In such a case ignorance is bliss."
It will be remembered that all the gods of Iceland were once gathered together so that a general oath might be exacted of every plant "that grew upon the earth," that they would do no harm to Balder the Beautiful. The Mistletoe did not take the oath, because it does not grow upon the earth but upon a tree. Then the enemy fashioned an arrow out of the mistletoe, and killed Balder.There is a modern idea that the story is a myth representing the death of Spring, for a great many similar stories occur in widely distant places.
However, it seems pretty certain that the plant was a sacred one to the Druids in the time of the Romans.
Ovid speaks of this in the line, "Ad Viscum Druidæ cantare solebant." At their solemn meetings, which were held in remote sacred groves, a Druid clad in white robes cut the mistletoe with a golden sickle. Then, apparently, human sacrifices were offered and a general festival took place.
Some remnant of this custom seems to have persisted in Herefordshire until recent times, for the tune "Hey derry down, down down derry" (which meansin a circle move we round the oak) is supposed to be a relic of the hymn chanted by the Druids when they had found mistletoe on the oak.
It was said in the Middle Ages to be a useful cure for apoplexy, madness, and giddiness. That is not at present the general view. Indeed, under present conditions it might conceivably promote the last and even the second of these disorders, though in an agreeable way!
The Mistletoe and its allies, Loranthus and Arceuthobium, grow upon the branches of trees like the orchids and gooseberries already mentioned, but they differ altogether in having a special kind of absorbing root which sinks down into the bark until it reaches the wood of the "host" tree. The sap running up the tree is then tapped by this root, and goes to supply the mistletoe with water and salts in solution. It has, however, its own green leaves. Thrushes eat the berries of the mistletoe; they will be left upon a branch with theguano; as the latter dries up, the seed is drawn to the underside of the branch, and sticks in a crackor crevice; it then sends the sinker-root mentioned above into the branch.
Every year afterwards new mistletoe "roots" are formed which grow through the soft part of the bark and send down sinkers into the wood. Cases of Mistletoes forty years old have been recorded. The trees which they prefer are the Apple, and after that Black Poplar, though mistletoe may be found on Silver Fir, various Pines, and others. It is more difficult to get it to grow on the Oak than on any other tree. Indeed, only seven cases of mistletoe growing on oak have been recorded in this country.[145]It is quite a valuable crop in some places, and is sent in tons to the London market.
There are many species of Mistletoe, and at least one kind attacks, and is parasitic upon, another species of Mistletoe.
Most Mistletoes and Loranthus have their own green leaves, and only take from the plant to which they are attached sap and mineral salts. But in Chile there is a beautiful Loranthus that has practically no green leaves at all. Its blood-red flowers grow in dense masses upon the giant Cactus, which is common on the drier hills, and these are always mistaken for the Cactus's own flowers, which are quite different. These almost leafless Loranthus, and the curious Arceuthobium are more parasitic than ordinary mistletoes, for they obviously take other food material (probably sugar and albuminoids) from their "host."
Another series of parasites or cannibals are quite common in Great Britain. One often sees in some meadow that the grasses are growing in a scanty and unhealthy manner; one then notices amongst them numbers of the Yellow Rattle or the Eyebright (which the Germans callMilk-thief). Theseplants are not very remarkable in any way, but if one examines them closely one sees that the leaves and stems are more purplish-red than is at all usual with our ordinary flowering plants. But if you dig up some specimens very carefully, then the wickedness of the Yellow Rattle and Eyebright becomes apparent; every here and there upon their roots are little whitish swellings which are firmly attached to the roots of other plants (generally of grasses). These two robber plants send from these swellings minute sucker-roots which pierce into the grass-root and intercept the water which the grass has been absorbing for itself.
They are therefore parasites, and indeed they may cause a considerable loss of forage in a meadow.
A good many other British plants are root thieves. Besides these two, there are the Cow-wheat, Red Rattles, Toadflax, Broomrapes, and Toothwort.
A curious point about them is that they differ amongst themselves in the degree in which they are dependent on the work of others. Some are able to grow quite well without any such extraneous help, but the Broomrape and Toothwort are entirely dependent on others' labours. They have extremely little chlorophyll and very small leaves, and are clearly parasites "pure and simple."
There are about 180 species of Broomrape (Orobanche). All of them attack roots, and most confine their attentions to one particular flowering plant. Their colours are generally very striking and unusual. Our British species are reddish, flesh-coloured, or dirty white, but some of the foreign kinds are blue or violet, yellow, or yellowish to dark brown. Generally the seedling Broomrape worms its way down into the earth till its root-tip touches the root of its special favourite host, then the root of the Broomrape fixesitself for life; its suckers grow into the host and absorb all the food material which it requires. Those kinds which attack Tobacco and Hemp are dangerous pests and do considerable damage.
The Toothwort (Lathraea) is so called because its scales have a sort of resemblance to human teeth. With the curious superstition which prevailed in medieval times, it was supposed that the plant must be a remedy for toothache because it resembled teeth. Unfortunately this is not the case.
It is, generally, quite like the Broomrape in its method of growth, but it sends out long thread-like branching roots with suckers on the ends, which become fastened on the Hazel roots. For several years the plant remains underground and forms very odd-looking, white, scaly branches. These scales are rolled back in such a way as to form peculiar and irregular cavities which open to the outside near the tip of the leaf. There is no doubt that animalcula of sorts get into these cavities and probably die there. In that case, their remains will form a useful supplement to the diet of the plant. The following remarks, however, taken from Kerner have been disputed by other botanists.
Certain of the cells lining these cavities "appear to send out delicate filaments.
"When small animals penetrate into the labyrinthine chambers of a Lathraea leaf and touch the organs just described, the protoplasmic filaments are protruded and lay themselves upon the intruders. They act as prehensile arms in holding the smaller prey, chiefly Infusoria, and impede the motion of larger animals so as to cut off their retreat. No special secretion has been observed to be exuded in the foliar chambers of Lathraea. But seeing that some time after thecreatures have entered the chambers, the only remains of them that one meets with are claws, legs, bristles, and little amorphous lumps, their sarcode-flesh and blood having vanished and left no trace, we must suppose that the absorption of nutriment from the dead prey here ensues...."[146]
But strange as these Broomrapes and Toothworts may be, they are quite inconspicuous as compared with the gigantic parasites found in Sumatra and Java.
In 1818, when Sir Stamford Raffles was making a tour in the interior of Sumatra, his party came across one of those extraordinary plants which have been called after him.
Imagine a gigantic flower in shape resembling a very fleshy forget-me-not, but more than a yard across! The colour is a livid, fleshy tint, and the smell is like that of a charnel-house. This extraordinaryRafflesia Arnoldiiis the biggest flower in the world. It has no proper stems or leaves, but consists merely of this huge flower-bud attached to the roots of Figs, etc., which traverse the ground in these forests. It is said to be only found in places frequented by elephants, which are supposed to carry its seeds on their feet.
There are four other kinds known: all of them occur in Sumatra, Java, and other neighbouring islands.R. Padmafor example, has a flower about eighteen inches across. The central part is a dirty blood-red, while the lobes have almost the colour of the human skin. This also has a "cadaverous smell, anything but pleasant."
These weird Rafflesias seated on the roots "which wind about on the dark forest ground" have impressed every observer.
Yet if one glances back, it is interesting to see how insensible are the transitional steps which lead from independentlife by the plant's own exertions to these last "pure parasites," which are entirely dependent on other plants for everything that they require.
The only other flowering plant which we shall mention in this chapter is now fortunately very rare in Great Britain. This is the Dodder,Cuscuta. It belongs to the Convolvulus or Bindweed order, but is entirely different from the rest of the family. Some climbing plants do throttle or choke the trunks of young trees if they twine round them too closely, but the Dodder has an entirely special and peculiar way of supporting itself to the detriment of others. It has no roots, no leaves, and scarcely any green chlorophyll; the Dodder is just a twining, thread-like, yellowish stem which carries here and there small round clusters of little convolvulus-like flowers. Wherever the Dodder thread twines round a hop or other plant, it puts out small suckers which drive their way into the stem of the hop and take from it all the food which the Dodder requires. When well developed it forms dense yellowish tangles of intricately entwined threads, which may cover whole bushes and entirely destroy the supporting plants. The Flax, Clover, and Hop Dodders are perhaps the worst of them all.
There are some rather interesting points in the history of the tiny dodder-seedling. It remains, quietly waiting, for about a month after most other plants have germinated.
Then it begins to grow rapidly: its tip pierces the soil and becomes fixed in it; then the rest of the little thread-like seedling begins to curve round or revolve. If it touches a grass or even a nettle stem, it twines itself or coils round it, drives in its suckers, and, on the strength of the nourishment which it extracts, it goes on revolving or turning until it forms the dense tangled masses referred to.
Then an eruption of flowers appears, from which later on hundreds of tiny seeds are let loose which will become Dodders in their turn.
The series of parasitic plants which have now been mentioned form a very interesting set. It must be pointed out that those which live merely on dead vegetable matter are "good" plants. They help on the quick and thorough employment of worn-out material.
Nor can we say off-hand that other parasites are "bad." They do kill other plants and do them harm, but then, are they not like a cattle-breeder who sends his inferior cattle to the butcher, keeping only those which are the very best of their kind? Perhaps these plants, by destroying the weak and unhealthy kinds, are doing a great deal of good.
Another interesting point about such parasites is that they are generallyrare. They must be less common than their "host." Yet another is that they are all "degenerates." They show distinct traces of decay and bad development in their flowers and seed. That is also true in the case of parasitic animals.
Whether they do good or harm to the world of plants is doubtful, but there is no doubt that they are doing harm to their own chances!
Brittle Starv.algæ—Fungusv.meal-worm—Stag-headed caterpillars—Liverwortv.small insects—Natural flower-pots—Watercups of Bromeliads—Sarracenia and inquiring insects—An unfortunate centipede—Pitcher-plants: their crafty contrivances—Blowflies defy them and spiders rob them—Bladderwort's traps which catch small fry—Hairs and their uses—Plants used as fly-papers—Butterwortv.midges—Its use as rennet—Sundew and its sensitive tentacles—Pinning down an insect—Suffocating and chloroforming the sundew—Venus' fly-trap which acts like a rat-trap—Have plants a nervous system?
ON the whole the animal world preys upon the vegetable world, and is in a way parasitic upon it. Indeed, the connexion between the two is very intimate—that of the diner and his dinner. One can scarcely imagine a more intimate connexion than this!
There are, however, a great many cases in which plants have turned the tables on their enemies and deliberately laid themselves out to catch and to destroy, to feed upon and to devour insects and small animals. One finds a few examples in almost every group of plants.
Thus there are certain green seaweeds or algæ which are said to attack and prey upon those peculiar sea-urchins known as Brittle Stars. The fungus which forms loops, acting exactly like a poacher's rabbit-snare, in order to catch mealworms, has been already mentioned.
Sometimes in the summer one may notice a little red clubabout two to three inches long sticking out of short grass. If one carefully pulls this up it is found to be growing out of a dead chrysalis or grub. It is a fungus whose spores have attacked the caterpillar; they have developed inside its body, and eventually, having completely eaten up the insect, form the red club, which is producing hundreds of thousands of spores intended to attack other caterpillars.
The branches like stag's horns are the fruit of a fungus, Cordyceps Taylori, which lived inside and killed the caterpillar.
The branches like stag's horns are the fruit of a fungus, Cordyceps Taylori, which lived inside and killed the caterpillar.
The branches like stag's horns are the fruit of a fungus, Cordyceps Taylori, which lived inside and killed the caterpillar.
An allied fungus forms a peculiar branched fruit rather like a minute stag's horn, and the caterpillar may be seen for some time crawling about with this extraordinary fungus sticking out of its head. Of course the bacteria are, some of them, by far the most dangerous foes of animals (see page328).
Then there is a small Liverwort, a little red, moss-like plant (Frullania tamarisci), which may be found growing on the bark of trees, which is said to catch animalcula in the small sack-like leaves which are underneath the ordinary ones.
But it is amongst the higher flowering plants that one discovers the most extraordinary and purposeful arrangements for capturing and digesting insects and other creatures.
In the case of many of these insectivorous plants, traps or pitfalls are prepared for the insect to fall into.
There are many plants in which the rain is intended to run in one particular direction, and it is not at all uncommon to find hollows at the base of the leaf where dust, dirt, and dead insects accumulate. One very curious plant of this sort isDischidia Rafflesiana, in which the leaves have become quite like a pitcher, and have been compared to "natural flower-pots" intended to hold rain and leaf-mould.[147]
Then there is the Bromelia or Pineapple family, which consists for the most part of plants which live on the branches of trees. In very many of these a small cup is formed in the middle of the rosette or tuft of leaves, and water collects in this central cup.
The water smells abominably, and contains the bodies of dead insects, and rubbish of all kinds (see also p.298). The remnants of these drowned insects are probably of use, because any valuable nitrogenous or other material may be absorbed with the water by the plant and help to nourish it, but in such a rough contrivance as this there is nothing comparable to the Side-saddle plant, Pitcher plant, and others.
The former, Sarracenia (or Side-saddle plant), is a common and rather widespread North American plant, which is especially abundant in Florida. It is cultivated in most botanical gardens, but can only be grown in greenhouses. The leaves are about six inches to a foot long, and arehollow, funnel-shaped tubes with a short, flat wing along one edge. They may be an inch or two in diameter at the top or wider end, where there is also a sort of half-open lid which keeps rain from getting into the inside of the leaf. The colour of these tube-like or vase-like leaves varies. It is often variegated with brown, red, and yellow, and is conspicuous enough even at a distance. Thus insects fly to these vases and alight on the little cap or lid, where they find honey and enjoy themselves. Other insects crawl up along the rim or wing of the vase, finding honey here and there along their road. Having got to the lid, the insect, being of an inquiring or inquisitive disposition, will look inside the tube and endeavour to find more honey therein.
It reaches the rim of the vase and finds that there is honey inside; it can easily crawl down, and fails to notice that the inside of the vase is lined with long stiff points which all point downwards. These points or hairs do not at all interfere with its passage down, and it proceeds to the honey which forms a smooth, slippery coating. Then, after greedily absorbing the honey, it tries to get out again. But that is quite a different matter. Each one of these points or hairs is facing it, and the whole inside is smooth and slippery. It struggles, slips, and falls into a pool of water which fills the lower part of the vase. That is what the plant has developed these pitchers for. The body of the insect after a time decays away, and only its empty shell remains. An extraordinary number of insects are caught by these Sarracenia vases. Sometimes in one which is only ten inches long, three or four inches will be full of the corpses of blackbeetles and other drowned insects, and it is said that birds occasionally visit these vases in order to pick them out. There is probably some sort of secretion in thewater. "A centipede 1-2/3 inches long having fallen into a vase ofSarracenia purpureain the night was found only half-immersed in the water. The upper half of the creature projected above the liquid, and made violent attempts to escape; but the lower part had not only become motionless, but had turned white from the effect of the surrounding liquid; it appeared to be macerated, and exhibited alterations which are not produced in so short a time in centipedes immersed in ordinary rainwater."[148]
In some Sarracenias the vase is brought up into a sort of hood or dome with the entrance at one side and below. There are thin patches on this dome or cupola, and small insects, attracted by the light which comes through these bare places, remain dashing themselves against them or crawling over them just as flies do on a window-pane, until they become tired and fall down into the water below.
There is something horrible in the cold and careful way in which this plant arranges its baits for "confiding insects. The latter are fed with honey, even on the very border of the assassin's den, but after this farewell revel they generally slip upon the smooth edge, and are hurled, like lost souls, down into the abyss."[149]
In another plant, the Pitcher Plant (Nepenthes, so called from the drug which produces the sleep of death), we find an even more beautifully arranged pitcher which acts in very much the same way. It is, however, only the end of a rather long leaf, or rather of its midrib, that is turned up to act as a pitcher. There are similar stiff hairs pointing downwards, and honey is plentifully secreted. But, in Nepenthes, there is also a distinct secretion which digeststhe bodies of the drowning insects. The ferment resembles the active principle of the gastric and pancreatic juices of the human body, and, as acids are also present, the insect's body becomes changed into nutritious juices which readily diffuse into the plant.[150]Dr. Macfarlane found that when the pitchers were stimulated by being given insects, the liquid inside them could digest fibrin to jelly in from three-quarters to one hour's time.[151]But certain insects have somehow managed to educate their larvæ to resist the gastric juices of Nepenthes.
Near Fort Dauphin, in Madagascar, I found great quantities ofNepenthes madagascariensis. Almost every pitcher was one-third to two-thirds full of corpses, but in some of them large, fat, white maggots, of a very unprepossessing appearance, were quite alive and apparently thriving. These must have been the larvæ of a blowfly similar to that which has been mentioned by others as inhabiting Sarracenia. At the same place a white spider was very often to be seen. Its web was spun across the mouth of a pitcher, and its body was quite invisible against the bleached remains inside.
It had suited its colour to the corpses within, in order that it might steal from the Nepenthes the due reward of all its ingenious contrivances!
A totally different arrangement is found in an inconspicuous and ugly little marsh and ditch plant called Utricularia or Bladderwort. It is very difficult to see, for unless it happens to be in flower it is entirely submerged in the water. The flowers, which are purple, are conspicuous and easily seen even at a distance. On these submerged leaves there are hundreds of small bladders. They are about thesize of a pea, and are most ingeniously contrived to catch small water-animalcula. The general idea of the bladderwort is exactly that of the eel-pots so common in some parts of the Thames. There is a small flap which acts as a trapdoor. Small creatures probably take refuge in the bladders when pursued by the larger water-fleas, etc., for it must seem to them to be a safe and secure retreat.
But once within the door, they are imprisoned and cannot find their way out again. They perish inside and their bodies are digested by the plant; on the inside of the bladder there are gland hairs which also secrete a digestive fluid.
The bladderwort is dangerous to fish, for the little fry, when quite small, run their heads and gills into the bladders and are suffocated.
There are a great many kinds of Utricularia, and they occur in most of the great floral regions.
One of them has chosen a very extraordinary and curious situation. It lives inside the little cups of water which, as we have already mentioned, are formed by the leaves of some Bromeliads. The insects in the water which ought to nourish the Bromeliad (Tillandsia) are really used by the Utricularia. Other Utricularias live in damp earth, moss, etc.
It is not only by traps and pitfalls that plants catch insects: many have specially modified hairs which are quite efficient insect-catchers.
Hairs are used by plants for many different purposes, and it is rather interesting to see how quite a simple organ like a hair can be altered. The stinging hair of the nettle has already been mentioned; many grasses possess minute, rough, flinty hairs, which probably prevent snails from eating them. That also is probably the reason of the strong, rough, coarse hairs which cover the Borage and the Comfrey.
Then on the Chickweed and the Bird's-eye Speedwell there are lines of rather long, flexible hairs which at first sight appear to be of no use at all. But if you take either of these plants, and, holding it upright, place a large drop of water on the leaves, you will see that these hairs are intended to carry the water down the stem. The water runs along them. It is a very pretty little experiment, especially if done in artificial light, so that these hairs are, like the root hairs, intended to absorb or suck up water as it passes over them. Then the Edelweiss and the Lammie's Lug (Stachys lanata) are entirely covered with white cotton-woolly hairs: these are intended to keep the water in the plant, and do so as effectually as a rough woollen coat will keep out rain and mist. Silky hairs, downy hairs, and others are found wrapping up the tiny baby leaves in the bud: they probably keep them warm, and perplex and ward off objectionable insects.
But, perhaps, the sticky or glutinous hairs are the most wonderful of all. They are found on many plants, such asSalvia glutinosa,[152]Plumbago, and Catchfly. One can see insects stuck on them and vainly struggling to be free, and the hairs undoubtedly prevent green-fly and other such pests from interfering with the honey of the flower. In some of these cases it has been shown that the body of the insect is actually used as food, but that is more obvious with two interesting plants which specially devote themselves to the capture of insect prey. One of these is very often kept in the Boer farmhouses near Tulbagh, in South Africa, simply to attract the flies, which are a perfect pest in those dry valleys. Another Drosophyllum, the Fly-Catcher, grows on sandy and rocky ground in Portugal and Morocco. This isalso used by the peasants near Oporto as a convenient fly-paper.
In both of these plants large drops of a sticky, glistening liquid are secreted by the hairs which cover the leaves. Any small insect alighting on the latter is sure to get covered by the liquid, and in trying to get away will become hopelessly involved in it. It is probably soon suffocated, for the gummy matter will choke the small air-holes by which it breathes. Both these plants are said to secrete both an acid and a digestive secretion.
But we have two plants which are even more interesting in this country.
Walking over the rough marshy pastures or moors of Scotland one is sure to notice, generally on wet peaty and barren soil, a little rosette of bright, yellow-green, glistening leaves. If it is the right season there will be a handsome purple flower whose stalk springs from them. This is the Butterwort (Pinguicula), and it is not a bad name, for the leaves remind one of butter. The whole upper surface of the leaves is covered with tiny glands secreting a sticky, glistening matter. It is said that there will be as many as fifty thousand of these glands on a square inch of the upper surface.
Now in such places every one knows that there are quantities of midges, and also that these insects are always exceedingly thirsty. They prefer blood, it is true, but when they see these bright yellowish leaves they naturally go to them. When, however, the midge touches the leaf, the sticky liquid clings to its wings and legs, and it cannot escape.
So far this does not differ from the Fly Catchers mentioned above, but another very curious action then begins.If the midge or fly is near the margin of the leaf, the edge of the latter begins to curl or roll inwards over it. It does so very slowly, and may not finish rolling over the insect for some hours. Whilst this is going on acids and "gastric juice," or ferments which act in the same way, are being poured over the body of the midge, which is finally completely digested. Next day, having finished the midge, the leaf majestically unrolls itself again and waits for another.
The juice contains rennet, and is used by the Lapps in making a horrible delicacy called Tätmiölk. It has also been used by the Swiss shepherds for at least two hundred years, to cure sores on cows' udders.
The other British plant is the Sundew (Drosera). Every one who has been on peat-mosses and moors probably knows its little reddish rosettes of small rounded or spoon-shaped leaves lying on bare peat or wet mossy ground. Each leaf seems to be covered by hundreds of glittering little dewdrops (whence the name).
The hairs or tentacles which cover the leaf secrete this glistening, sticky fluid. There must be about two hundred of them on a single leaf.
An insect flying about near the Sundew is sure to be attracted by the conspicuous glittering, reddish leaves, and probably alights upon it. Then it finds itself caught and begins to struggle, but this simply brings it against more tentacles.
Now happens the most wonderful part of the whole performance. All the neighbouring tentacles, although they have not been touched, bend over towards the struggling insect and pin it down in the middle of the leaf. They do not bend over very quickly. In two or three minutes theywill bend over towards it through an angle of forty-five degrees, and it takes them ten minutes to bend over ninety degrees.
There is something rather horrible in the sight of a large insect struggling with these slow, remorseless, well-aimed tentacles; most people free the insect unless, at least, it happens to be a midge. The point which is so difficult to understand is to know how those untouched tentacles know that the insect is there and exactly where it is. There is no doubt that they do know, for they behave exactly as if they were the arms of a spider.
If you put two insects on either side of the middle of the leaf, half the tentacles will pin down one and the other half will deal with the other insect.
At the same time acids and ferments are poured out which digest the insect. It takes about two days for a leaf to finish off an insect, and then the tentacles again unclose.
Moreover it is difficult to deceive those tentacles. They will bend in for the tiniest piece of useful substance; for instance, a length of one-seventy-fifth of an inch of woman's hair will make them secrete digestive fluid. One millionth part of a pound of ammonium phosphate will also produce secretion. But a shower of heavy rain, grains of sand, or other useless material, will not cause any secretion, and even if they do bend in a little, they soon discover their mistake and stand out again. If you try the same experiment under a bell-glass from which the oxygen has been withdrawn by an air-pump, nothing happens; or if you chloroform the Sundew it will pay no attention to small pieces of meat until it recovers from the effects of the chloroform.
When these Droseras are taken to a greenhouse and experiments are made on them, they run into very greatdanger. They are almost certain to die of overfeeding or indigestion. It is impossible to keep people from giving them too much to eat.
This wonderful little plant shows quite distinctly that there must be some way of sending messages in its leaves. Somehow the message travels from the tentacle which the fly has touched, down the stalk into the leaf, and up into the other tentacles, and tells them that there is something worth stooping for.
No one has explained this, and probably no one will ever do so.
The last, and in some ways the most interesting, of all these carnivorous plants is Venus' Fly-trap (Dionæa muscipula), which grows in North America from Rhode Island to Florida.
It is a quite small herb with a small circle of leaves which lie flat on the ground. Each leaf ends in a nearly circular piece which is divided by a very marked midrib. The two semicircular halves have a series of teeth along their edges; these margin teeth are stiff and a little bent upwards. In the centre of each half there are three small hairs. On looking closely at these hairs one finds that each has a joint near the base; all over the centre of these leaf halves there are scattered glands which secrete ferments intended to digest any animal matter.
The really interesting point is connected with these central jointed or trigger hairs; they are extremely sensitive. But when they are touched it is not they themselves that are affected, but the entire circular end of the leaf!
Suppose an insect wanders on to the leaf and reaches one of these semicircular halves, nothing happens until it touches one of these hairs, but thenbothhalves suddenly closetogether, exactly like an ordinary rat-trap! The teeth on the edges of the halves interlock like the teeth of a trap, and the insect is caught and imprisoned.
Its body is slowly digested away and goes to nourish the plant. The use of the joint in the sensitive hairs can be easily perceived, for when the two halves shut up together, the hairs fold down exactly like the funnel of a river steamboat when it passes under a bridge.
The closing of the two halves, which has been well compared to shutting up a half-open book, is very quick, as it does not take more than ten to thirty seconds. There is an abundant flow of "gastric juice," but the leaf takes a long time to digest its food. It may require three weeks to finish one insect. Moreover, if overfed, it may turn a bilious or dyspeptic yellow colour, and wither or even die. It only shuts for a short time if a grain of sand touches the sensitive hair, and, like Drosera, is not deceived in its food.
The Dionæa, Drosera, the Sensitive Plant, Mimulus, Barberry, and others, all show us clearly that plants somehow or other act as if they were conscious of what they ought to do. In fact, in all these cases, it is scarcely possible to help believing in some sort of rudimentary nervous system. At any rate Wordsworth comes near this belief, for he has written:—
"It is my faith, that every flower that blowsEnjoys the air it breathes."
"It is my faith, that every flower that blowsEnjoys the air it breathes."
"It is my faith, that every flower that blowsEnjoys the air it breathes."
"It is my faith, that every flower that blows
Enjoys the air it breathes."
Peat-mosses and their birds—Moorlands—Cotton-grass—Scotch whisky—Growth of peat-moss—A vegetable pump—Low-lying and moorland mosses—Eruptions and floods of peat—Colonizing by heather and Scotch fir—Peat-mosses as museums—Remains of children and troopers—Irish elk—Story of the plants in Denmark—Rhododendrons and peat—Uses of peat—Reclaiming the mosses near Glasgow.
IN Great Britain in this present year one finds exceedingly few places where the influence of man cannot be traced. Over most of the country, indeed, it is impossible to discover a single acre of land where Nature has been allowed to go on working at her own sweet will without interference or restraint.
But near Stirling, between the Lake of Monteith and the sea, there is a wide, desolate valley which is probably in exactly the same condition as it was when the Roman legions halted to reconnoitre before Agricola passed onwards to Perth and Aberdeen.
Indeed, this great peat-moss has been probably in very much the same condition for some 200,000 years, which is a nice round number to represent the ages that have passed since the Great Ice Age.
Now, as then, it is inexpressibly dreary and desolate; everywhere saturated with water, and only to be traversed in dry seasons and with much agility. Even with thegreatest care the pedestrian may sink to the waist in a hole of black, slimy, peaty water. Moss, Heather clumps, Sedges, Rushes, and occasionally Cotton-grass, almost at one dead level, stretch right across from the one side of the huge valley to the other.
Even grouse are not common. In summer great numbers of gulls lay their eggs upon the moss. This also is one of the few places in Britain where great flocks of wild geese can be heard and seen, but only at a distance.
It is almost impossible to get near them, for the upright neck of the sentinel cannot be seen by the stalker as he wriggles towards the flock on his face, until long after the stalker himself has been plainly visible to the bird.
Of all useless stretches of barren waste, such a moss as this seems one of the worst. It would, of course, be possible to reclaim it; probably, fertile fields and rich meadowscouldbe formed over the whole valley, but it would not pay nowadays. There is so much good land available in Canada, the United States, and Australia, that this great stretch of our native country will probably remain as useless as it was in Agricola's days.
In the Scottish Lowlands and Highlands the moorlands are almost as desolate. At a height of 1500 to 1600 feet in Southern Scotland there is nothing to be seen but the undulating lines of hills, all dark purple with heather or with the peculiar scorched reddish green of Deer's Hair and dried sedges.
Perhaps on the nearer hills small streams may have cut a whole series of intersecting ravines in the black peat. They may be six to ten feet deep, and here and there the bleached white stones which underlie them are exposed. Now and then the "kuk-kuk-kuk" of an irate cock grouse, and muchtoo frequently the melancholy squawking of the curlew, irritates the pedestrian as he stumbles over clumps of heather, plunges in and out of the mossy holes, or circumvents impossible peat-haggs.
An Arctic Alpine PlantThis is Draba Alpina from Cape Tscheljuskin, and it is drawn the natural size. The stunted, closely set leaves show the inclement character of the climate.
An Arctic Alpine PlantThis is Draba Alpina from Cape Tscheljuskin, and it is drawn the natural size. The stunted, closely set leaves show the inclement character of the climate.
An Arctic Alpine Plant
This is Draba Alpina from Cape Tscheljuskin, and it is drawn the natural size. The stunted, closely set leaves show the inclement character of the climate.
It is indeed a remarkable fact that though these islands support 44,000,000 of inhabitants, including at least 1,000,000 paupers and unemployed, one-seventh of Ireland and many square miles in Scotland are still useless peat-bogs!
The Bog of Allen alone covers 238,500 acres, and the peat is twenty-five feet deep.
In some few places the peat is still used for fuel, and there is a theory to the effect that peat reek is necessary for the best kinds of Scotch whisky, but neither grouse nor black-faced sheep, which live on the young shoots of the heather, employ in at all a satisfactory way these great stretches of land.
Many attempts have been made to spin the silky threads of the Cotton-grass which grows abundantly on the Scotch lowlands. It is neither a grass, nor does it supply cotton, but is called Eriophorum. It is perhaps the one really beautiful plant to be found on them, for its waving heads of fine silky-white hairs are exceedingly pretty.
The heather itself gives a splendid red and purple shade, which in summer and autumn is always changing colour, but it is monotonous. Neither the little Bog Asphodel with its yellowish flowers, nor red Drosera, or butter-coloured Butterwort, are particularly beautiful.
After seeing such a country one understands something of the Cameronian Covenanters who held their conventicles and took refuge therein.
The manner in which these mosses and moors have developed is most interesting, and yet difficult to explain.
There are two kinds of peat-mosses, which, although there are many intermediate types, may be kept apart.
The first, like the one near Stirling, Lochar and Solway Moss, near Dumfries, and Linwood, near Glasgow, have been formed in low-lying flat estuarine marshes.
If one refers back to page210, it will be seen how reeds and rushes and marsh plants may gradually fill up river backwaters. Eventually a saturated, marshy meadow is produced.
Then comes the chance of that wonderful moss the peat-moss, or Sphagnum. It is scarcely possible to appreciate its structure without the help of a microscope and a good deal of trouble in the way of imagination.
It is in a small way a sort of vegetable pump which raises water a few inches or so. Stem and leaves and branches possess little cistern cells, which act both as capillary tubes raising the water and also retain it. The stems are upright and develop many branches, so that they become a close-ranked or serried carpet of upright moss-stems squeezed together, which floats on the surface of the water. Each moss-stem is growing upwards and dying off below. In consequence, the bottom gets filled up by dead mossy pieces, which accumulate there, while the live moss-carpet remains floating on the surface of the loathly, black, peaty water.
In many peat-mosses the water gets entirely filled up, but that does not stop the formation of the peat-moss. It is now resting on the water-saturated remains of its forefathers, and if water is abundantly supplied it goes on developing.
Thus in these lowland or estuarine peat-mosses the moss eventually occupies the water, and goes on growing. After this it develops like the moorland mosses which cover most of the Lowlands and Highlands of Scotland. They cover thehills, and it looks exactly as if some giant had plastered all those hills with a layer of six to ten feet of black peat from 1250 feet upwards.
The soil would at first be covered by a saturated moss-carpet ofSphagnumand other mosses. Rainwater falling upon it was all retained, and very little could get away, for the Sphagnum carpet is just like a huge sponge soaking up and retaining the water.
But it sometimes happens in these great upland mosses that there are enormous falls of rain which continue for days. Then the water collectsunderthe living moss-carpet and over the dead peat. It may be gathered together in such quantities that the carpet of living peat above it bursts, and a deluge of peaty water overflows the surrounding country, destroying and spoiling everything that it encounters.
The worst of these inundations of black mud that has happened in recent years was in December, 1896, near Rathmore, where 200 acres of bog burst and a horrible river of mud overflowed the country for ten miles. Nine people perished, and enormous destruction was caused.
There have been many other cases. In 1824 Crowhill Bog, near Keighley, burst; and in 1745, in Lancashire, a space a mile long and half a mile broad was covered by peaty mud. There was also a case in 1697, where forty acres of bog at Charleville burst in the same way.[153]
Attempts have often been made to calculate the rate of growth of such peat-mosses. A great many of them began to develop on the mud left by the ice-sheet when the glaciers retreated at the end of the Ice Age. Those mosses are therefore probably 200,000 years old. Some of our Scotch mosses are twenty to twenty-five feet in depth, whichgives a foot in 10,000 years. By calculation of the weight of the peat formed, Aigner made out that a certain moss was 20,600 years old, and was growing at the rate of two inches in a century.
But in Denmark ten feet has been formed in 250 to 300 years, and in Switzerland three to four feet of peat-moss has been formed in twenty-four years.
This shows quite distinctly that there is no regular rate of growth, and indeed it is obvious that much must depend on the climate, on the rainfall, on the drainage, and other circumstances.
Sooner or later, however, a limit comes to the growth of the moss. The surface then becomes gently curved: it is highest in the centre, and slopes very gently down in every direction to the edges.
What happens next? The first sign is that the surface begins to dry up, and Heather, with grey Cladonia lichens, begins to grow on the projecting tufts and tussocks.
Occasionally, if gulls build their nests on such drying-up mosses, patches of bright green grass appear wherever the gulls are in the habit of resting. That is due to the lime in their guano.
But under quite natural conditions a much more important and interesting change begins.
Here and there scattered over the moss, miserable little seedling Birches and Scotch Firs begin to struggle for life. Of course, if there are hares and rabbits, or if sheep and cattle are allowed to graze upon the moss, those firs have no chance whatever. They are eaten down to the ground.