Stereo Copyright, Underwood & UnderwoodLondon and New YorkGathering Rubber in TehuantepecIncisions may be seen in the bark of the tree. The rubber milk runs out from these into the vessel held in the man's hand.
Stereo Copyright, Underwood & UnderwoodLondon and New YorkGathering Rubber in TehuantepecIncisions may be seen in the bark of the tree. The rubber milk runs out from these into the vessel held in the man's hand.
Stereo Copyright, Underwood & UnderwoodLondon and New York
Gathering Rubber in Tehuantepec
Incisions may be seen in the bark of the tree. The rubber milk runs out from these into the vessel held in the man's hand.
What is supposed to be the original wild plant from which the opium poppy was derived seems to have been cultivated in the ancient Swiss lake dwellings, for the seeds ofPapaver setigerumoccur there in abundance. The price of the crop may amount to £90 or £120 per acre.
Another very ancient plant is the Hemp,Cannabis sativa. It was known to Herodotus, who says that "in the country of the Massagetæ there is a tree bearing a strange produce which they casting into a fire inhale its fumes on which they straightway become drunk." It is a tall, rather handsome annual, with stems from three to fifteen feet high. It is cultivated all over the world, from the Equator to 60° north latitude, but for different purposes. In India it is chiefly for the resin, "haschisch, churrus, bhang." (That was the drug used by the Count of Monte Cristo.) In Russia it is for the seed and the fibre that the plant is cultivated, and in France, Italy, and Austria the fibre seems to be the most important product.
Some of the plants produce only stamens or male flowers. The fibre given by these is stronger and more tenacious than that of the female plant, which, however, is finer and more supple. The fibre obtained from the cold northern districts of Russia is said to be the strongest of all.
The preparation of the fibre is a long, tedious, and laborious operation. It is also unhealthy, for the fibre has to be "retted" (steeped in water so that the soft partsdecay), "scotched" (that is the hard wood must be broken and removed), and "heckled."
This last process is familiar to all who are interested in political matters. It consists of being drawn on hard points difficult to traverse and of a very fine and sharp character! Hemp is the commonest fibre for string, rope, etc.; it used to be employed for sailmaking by the Romans. Catherine de' Medici is said to have had two chemises made of hemp.
Hempseed is much appreciated by poultry and birds of all kinds (which makes both harvesting and sowing rather difficult); but the chief use of the seed is to furnish a fatty oil used for soft soap, lighting, and painting. The remains, after taking the oil, are employed as a cattle food, but it does not form a satisfactory cake.
The chief interest of hemp is, however, the drug that is made from the resinous juice. No doubt this has the effect of keeping off dangerous insects, for it is said that plants of hemp even keep off insects from other plants planted close beside them.
Sometimes the leaves and stalks are dried in order to make the drug "bhang." Many allusions to this substance are found in Eastern poetry, where it is called the "Leaf of Delusion," "Increaser of Pleasure," and "Cementer of Friendship," but madness is the result of addiction to its use.
The resin is collected by making the labourers put on leather aprons, and then run up and down vigorously through the hempfields. The resin is then scraped off the leather, or off their skins if they prefer to do without leather. It is either eaten or smoked. Burton describes how at every cottage door in East Africa the Arabs may be seen smoking bhang with or without tobacco. "It produces a violent cough ending in a kind of scream after a few longpuffs." In small doses haschisch (resin) has pleasant effects, for people experience pleasant illusions, good appetite, excitement, and laughter, followed, however, after an interval by stupor and sleep.
People addicted to the use of haschisch roll their eyes violently, and have a wild, startled appearance.
Naturally so dangerous a drug cannot be recommended unless under the most exceptional circumstances, but it is employed in cases of asthma and insomnia. Haschisch and opium are the two great curses of the Chinese, Malays, and the inhabitants of British India and the East. They may be compared to "drink" in this country, but they are important medicines.
Among the most curious and interesting facts in Nature is the extraordinary variety of the ways in which at present gutta-percha and india-rubber are employed. We should not be able to ride bicycles, or in motor-cars; we could not use Atlantic cables and many electrical apparatus; our railway carriages would be most uncomfortable; golf would be impossible; we should have no waterproof coats and no goloshes [sic], if it were not for these valuable and extraordinary substances, india-rubber or caoutchouc, and gutta-percha.
Their history is full of romance, but perhaps the most striking part of it is just this fact. Because a few (only a very few) plants found it necessary to protect their wood from burrowing beetles by a specially poisonous and elastic substance,thereforewe can play golf and enjoy free-wheel bicycles.
The rubber is derived from the resinous latex or milky juice, which pours out from any wound in the bark of certain trees and creeping plants. This milk must be poisonous enough to kill the rash and intrusive mother beetle, whowishes to lay her eggs in the wood. It must be elastic, because the branches and stems swaying to and fro in the wind require a yielding, springy substance, but resin is contained in it, so that it promptly hardens and closes up the scar. The traveller Belt, in hisNaturalist in Nicaragua, mentions that those trees which had been entirely drained of their rubber by the Indian gatherers were riddled by beetles, and in an unhealthy, dying condition.
Almost all the important rubber plants are found in wet, unhealthy, tropical forests; they are by far the most important jungle product in West Africa, as well as on the Congo River and in the Amazon valley.
It is quite impossible to describe the various rubber trees, and the different methods of gathering rubber, but it may be interesting to quote from an account of the method of its collection in Nicaragua, by Mr. Rowland W. Cater.[135]
The best season for tapping the trees ofCastilloa elasticais from August to February. It is best also to perform the operation early in the morning before the daily rain, "or in the evening after the rain has fallen. The milk ... is white and of the consistency of cream. The tree thrives best in moist but not marshy forests.
"It seeds in the tenth year, and ought not to be tapped before its eighth year, or its growth may be much retarded.
"On reaching the group of trees, which numbered seventeen of various sizes, my Carib friends first cut away the twining creepers that almost hid the trunks, and then carefully removed a couple of buruchas, natural ropes of rubber, formed in the following manner: From incisions in the bark, possibly caused by woodpeckers or some insect, the juice often exudes, trickling down the trunk, in and out of the encircling creepers,and sometimes reaching the ground. The milky stream coagulates and turns black as it runs, forming a long strip or cord, with which the huléros often tie up their bales.
"The parasites removed, Pete and José strapped on their espuelas (climbing spurs), fastened at the knee and ankle, and having dug a small pit or basin at the foot of each of a couple of trees, passed a ring of stout rope round the trunks and their own waists, and walked up with their machetes between their teeth. By lifting the rope at every step they were enabled to stand almost erect, and when lying back in the ring both hands were at liberty.
"José, whom I watched closely, commenced operations immediately below the first branch. With his broad-bladed sword he cut in the bark a horizontal canal which almost encircled the trunk and terminated in a V-shaped angle. From the point of the V downwards he next cut a perpendicular canal about two feet in length, which joined another horizontal channel ending in a V, and so on to the ground. In the last cut he inserted a large green leaf to serve as a funnel and guide the milk into the basin.
"The Brazilian rubber collectors always place a receptacle of tin or earthenware in the hole at the foot of the tree to prevent the admixture of grit or other foreign matters; they also strain the milk through coarse muslin; hence the greater value of Pará rubber. But Nicaraguan methods are primitive."
In the Congo Free State the taxes are paid by the collection of rubber. It is alleged that "if the demands for rubber or other produce were not satisfied, the people at fault were flogged often most barbarously with a thong of twisted hippopotamus hide, called thechicotta. Or else the natives were told to catch the women from the offendingvillages, who were brought to theChef de Posteand imprisoned by him as hostages for the industry of their husbands. Or else the sentries shot some of the defaulters as examples to the rest. Frequently there were armed expeditions into refractory districts and widespread promiscuous slaughter. The cannibal soldiers of the State or of the Company sometimes feasting on the bodies of the slain."[136]
The supply of rubber has of recent years shown signs of becoming exhausted. As time goes on the Indians of the Amazon and Orinoco must every year travel deeper into the inaccessible forests of the Amazon, Orinoco, or in Nicaragua. Every year also makes it more difficult for the Malagasy in Madagascar, or the Negroes in West Africa and the Congo, to gather sufficient rubber for the world's ever-growing needs. Liberia, the Negro Republic, is said still to possess plenty of rubber; but it is probable that the true solution of the difficulty will be found in the plantation of rubber trees. The exports from Madagascar in 1903 were valued at 2,585,000 francs; from Brazil, £9,700,000; from Nicaragua, 400,000 gold pesos (twelve pesos to the £); from the Congo, 47,000,000 francs; but even then about 85,000 rupees worth of rubber was exported from plantations in Ceylon. Unfortunately the trees do not begin to yield until they are eight years old, but the estimated profit per acre is very high, at least according to some authorities, who give a yield of £88 per acre (in Nicaragua).
One cannot help hoping that this will be the case. When one thinks, e.g., of the Uachins in the forests at the head of Namkong, who spend forty days in carrying their rubber on men's shoulders across the mountains to Assam, or of the horrible stories of the Congo Free State, plantationseems decidedly a more satisfactory method of supplying us with golf balls and bicycle tyres.
The first account of india-rubber is found in Herrera (Columbus's second voyage), who describes the way in which the natives play "with great dexterity and nimbleness." "They struck balls with any part of their bodies."
Juan de Torquemada in 1615 gives quite a good description of the Castilloa rubber:—
"The tree is held in great estimation, and grows in a hot country. It is not a very high tree: the leaves are round and of an ashy colour: it yields a white milky substance, thick and gummy and in great abundance. It is wounded with axe or cutlass, and from the wound the liquid drops into calabashes: Indians who have got no calabashes smear their bodies over with it (for nature is never without a resource), and when it becomes dry remove the whole incrustation."[137]
The first patent for waterproofing seems to have been granted in 1791. A Charles Macintosh invented the garment named after him in 1823.
Very little of the commercial rubber is obtained from the common india-rubber Fig (Ficus elasticus) which we commonly grow indoors. This is one of those species of the Fig family which are generally found growing on the branches or trunks of other trees, though their own roots crawl down the trunk of the support to the ground. Once these roots have reached the ground, they take firm hold and grow so large and thick that they may be able to hold up the Fig tree even if the original support decays and crumbles away.
The gutta-percha which we use comes chiefly from Singapore,which is a sort of world's market for rubber. There are a great many different varieties and substitutes of this substance, but the best kinds come from Malaysia, Singapore, Sumatra, Java, and Borneo. The uses of gutta-percha and of vulcanite, which is manufactured from it, are very varied. Thus, it is employed for the soles of boots, door-handles, pipes, ear-trumpets, buckets, submarine cables, etc. It is indestructible in sea-water, and does not conduct electricity.
A very extraordinary exception to the general rule that latex is highly poisonous, is found in the famous Cow Tree of Venezuela. This tall tree (it is often 100 feet high) is found in large forests near Cariaco, on the coast of that country. Its milk is said to closely resemble ordinary milk in taste, and to be perfectly wholesome and nutritious, but it is rather sticky. This tree was responsible for all sorts of curious and extraordinary legends in the sixteenth and seventeenth centuries.
Robin-run-the-Hedge—Bramble bushes—Climbing roses—Spiny, wiry stems of smilax—The weak young stem of a liane—The way in which stems revolve—The hop and its little harpoons—A climbing palm—Rapidity of turners—The effect of American life on them—Living bridges—Rope bridges in India—The common stitchwort—Tendrils—Their behaviour when stroked or tickled—Their sensibility—Their grasping power—The quickness with which they curve and their sense of weight—Charles Darwin—Reasonableness of plants—Corkscrew spirals—The pads of the Virginian Creeper—The ivy—Does it do harm?—Embracing roots—Tree ivy.
THERE are many plants which depend upon and cling to other more sturdy kinds, and which would be quite unable to live upon the earth at all if they had not developed the most beautiful methods of doing so.
In autumn, as soon as the leaves of the Hawthorn have fallen off, one is sure to find upon the hedges the common Robin-run-the-Hedge (Goosegrass, Cleavers, or Sticky Willie, for it is known by all these nicknames as well as by its proper name,Galium aparine).
Its stem is exceedingly weak, but it will be found sometimes to be six or seven feet long. It does not support itself, but is resting amongst and entangled in the outer twigs of the hedge in such a manner that it cannot be blown away by the wind or indeed picked out without its being broken. The young stems grow upright and are vigorous at first, but soonthey cannot bear their own weight, and fall back upon a branch of the hedge. There are small curved little roughnesses along the stem and on the under side of the leaves of the Galium; these hitch on to the twig. Up to this point then the stem is supported, and the young part above grows until it also gets a lodgment, and so it goes on until it sometimes reaches right over the top of the hedge.
Its young flowering branches grow out towards the light away from the main stem, and the yellow withered stem in autumn rests upon the hedge just as a piece of string laid upon it might do.
The Bramble and Rose manage to get a support in very much the same way, but in Great Britain the Bramble generally grows in open ground and its branches take root.
The peculiar, curved-back prickles of the Bramble and its arching sideways growth would of course hang it on to any horizontal branches in the neighbourhood. Kerner measured the length of the stem of a Bramble which had interwoven itself into the boughs of a tree, and found that it was over twenty feet long, although it was only one-third of an inch thick. In Chile one often finds hedges of Brambles ten to fifteen feet in height, which have been formed by the aid of other plants, and also by the way in which the branches become entangled with one another.
Some Climbing Roses act in a very similar way, especially if grown on trellis, but the flower shoots always turn to the light like those of the Galium.
But it is the creepers and lianes of the tropical forests that are the most remarkable of all climbing plants. They twine round the stems and hang in great loops and grotesque folds from the branches. Sometimes in the dense shade itmay be difficult to see the main stem, for it is quite thin, though as strong as a piece of steel wire. It often happens, when hurrying through a rather open part of the forest after game, that one's leg suddenly catches in a thin, spiny, wiry stem of Smilax or some such creeper. The first that one knows of the creeper is when a quarter of an inch of the spine is buried in one's flesh.
Away up amongst the branches and foliage far above one's head, leaves and flowers are developed on numerous branches which have vigorously pushed out as soon as they got near the sunlight, this tough, spiny, thread-like stem being their only connexion with the ground.
The development of these climbing plants is probably connected with the dense shade of forests. In such places a young stem growing up will become long and drawn out; its tip will droop over and hang downwards. But there is a curious peculiarity in the growth of all stems. The stem generally grows more rapidly at any one time on one side, say on the north, and therefore bends over to the opposite side. After a time it will be growing most rapidly on the eastern side and then its head points westwards, and so on. The result is that the tip of the stem swings in an irregular circle round the stem itself. Its head turns to every point of the compass in succession. Supposing a stone is tied to the end of a piece of string, and one swings the stone horizontally in a circle, then, if an upright stick is put in the ground and the string comes against it, the string will coil itself round the stick because the stone goes on swinging horizontally.
Our young climbing plant in the shade of the forest acts in exactly the same way. If there is any trunk of a suitable size, it will in the course of its revolving or sweeping roundfirst touch and then coil itself round and round the trunk.[138]Of these twining stems, one of the most interesting and beautiful is the common Hop. The young shoots or suckers which come from the ground may be seen waving their stems helplessly round in the air. If they cannot find something to cling to, then they form weak limp curves, but if one such shoot touches a pole it very soon obtains a hold, wraps itself round the support, and easily climbs up to a height of many feet. But the Hop is worth examining closely. If one passes the fingers along the stem, it feels rough and prickly. With the aid of a hand-lens, a whole series of most exquisite little hooks will be discovered. They are like small pimples with two or three very fine and minute, sharp grappling-hooks on the top. These prevent the stem from slipping off. It is also helped in climbing by its leaves, which curve outwards, and are also provided with grappling prickles on the under side. At the top of the stem the young leaves are close together, and folded near the point, so as not to interfere with the tip finding its way in and out of a trellis-work or amongst branches.
These grappling-hooks on the Hop are as perfect in their way, though by no means so beautiful and elegant as those which are found in the climbing palm, Desmoncus, so well described by Kerner in hisNatural History of Plants. It is one of the rotang palms which reach lengths of 600 feet, though their stem may be no more than 1-1/3 to 2 inches thick. The leaflets towards the end of the leaf are transformed into strong spiny barbs which are exquisitely adapted to hang on to other plants. In many places, thickets in which these rotang palms have developed are so matted andtangled together that it is quite impossible even to cut into them, and they are practically impenetrable.
In a Kentish Hop Garden
In a Kentish Hop Garden
In a Kentish Hop Garden
Some of our common British twiners climb very quickly. A complete turn round the supporting pole was made in England, at Charles Darwin's home, in the following times. The Hop took 2 hrs. 8 mins., Wistaria 2 hrs. 5 mins., Convolvulus 1 hr. 42 mins., and Phaseolus 1 hr. 54 mins. A Honeysuckle took 7 hrs. 30 mins. to make one complete turn round the support.
Recently Miss Elizabeth A. Simons timed the rate of growth of the same plants at the University of Pennsylvania. They seem to have been stimulated by the exhilarating atmosphere of the United States, for they were all growing faster. The Hop did its turn in 1 hr. 5 mins., Phaseolus took from 1 hr. to 1 hr. 20 mins., Convolvulus 57 mins. only, Lonicera from 1 hr. 43 mins. to 2 hrs. 48 mins., and Wistaria 2 hrs.[139]But there are curious variations in the rate at which these plants revolve.
Thus when coming towards the light they go as fast as they can, but revolve more slowly, and as it were reluctantly, away from it. It has been found in one case that the shoot took thirty-five minutes to do the semicircle towards the light, and an hour and fifteen to twenty minutes going away from it, but this is not always the case, for sometimes the reverse takes place[140](Baranetzki).
These twining plants are not very common in Great Britain, and indeed in Europe. Some of them move or twine to the right (in the same direction as the hands of a watch or of the sun), such as Convolvulus (Bindweed), Phaseolus, Ipomœa, and Aristolochia. Others, like the Hop,Polygonum, Convolvulus, Honeysuckle, and Elephant's Foot, move in the opposite way from right to left, or "widder-shins." But there is nothing very important in this distinction, for the Bittersweet may be found twining in either direction, and in some plants part of a stem may be twining one way and the other in the opposite direction.
It is in the tropics, and especially in the rank, dark, moisture-laden atmosphere of the coast jungle forests, that these twiners attain their greatest development.
They show the most extraordinary variety. Sometimes a twiner hangs in elegant festoons from branch to branch, forming a convenient suspension bridge for monkeys. Sometimes four or five are wound round one another or twisted together, so that they look like some gigantic cable. In other cases they are knotted, looped, tangled, and twisted in the most inextricable manner.
Some creepers are flat, like green ribbons or broad bands. In others the dense mass of old, thick creepers and twiners round some sturdy trunk becomes so thick and so fused together that when the trunk dies the lattice-like arrangement of these creepers may keep them upright although the original supporting trunk is quite rotten and decayed away.
More usually, a tree will become unhealthy because its branches are overladen with the dense foliage and flowers of heavy lianes, and because both trunk and branches are so strangled in the embrace of great creepers that they cannot expand and develop in the proper way. Then a storm will overthrow the dead giant of the forest, and these creepers, entangled with all the surrounding trees, will produce ruin and destruction all around.
A regular duty of the foresters in India is to cut the stemsof climbing plants. These twining, trailing, rope-like creepers are, in fact, natural ropes, and are used as such in India, Burma, and other places. Sometimes they form natural bridges of living plants extending across a stream. The great suspension bridges in the valleys of the Himalayas are sometimes made without a single nail or plank. They are just three ropes (one for the feet and two to hold on by) made of jungle creepers. Crossing one of these swinging, swaying creeper-bridges is not an easy matter for those whose heads are unaccustomed to depths of hundreds of feet below them, especially if combined with a motion of the creeper-bridge sufficient in itself to produce violent seasickness. Yet the natives run across them with loads on their heads!
But it is not necessary to go to the tropics to find interesting and ingenious climbing plants.
There is a very common little British plant,Stellaria holostea(the Star of Bethlehem, Great Starwort, or Stitchwort), which is common in shady places, light woods, and by hedges. In the spring it grows very quickly, and the pairs of leaves are shut together over the growing point, so that the end of the stem is narrow and can insert itself between the leaves and twigs of the neighbouring plants. As soon as such a growing end gets out of the foliage into the light, each pair of leaves opens out and curves backwards, making a pair of broad, curved hooks excellently suited to hang the stem on to the leaves or twigs. Then another period of growth follows, and again a new pair of hook-like leaves opens out. The stem may be five or six feet long.
In a rather rare Speedwell (Veronica scutellata) a very similar method is used, but the leaves have special little backward-pointing teeth on their edges which assist in the attachment process.
But these leaves are not to be compared as regards perfection of mechanism with the tendrils by means of which plants climb. These tendrils are thin, flexible, twining threads, which may be formed by the modification of whole leaves, in other cases of leaflets, or sometimes of branches. Sweet Peas, Vetches, Passion-flowers, Vines, and many other plants possess them.
They are like twining plants in the way in which they revolve or twine so as to wrap themselves round anything which they touch. They move much faster than twining plants. A Cobæa tendril only takes twenty-five minutes to make a complete turn, Passion-flowers take from half to three-quarters of an hour, and the Vine tendril takes a little over an hour to make one complete turn.
But in one way they differ altogether, for they are sensitive to contact. If tickled, they contract and embrace closely the object which is touching them. They show a most extraordinary sensibility and sensitiveness.
As a matter of fact, these tendrils have a finer sense of touch and a much more delicate feeling of weight than any human being. They detect the weight of twenty-seven inches of a spider's thread.
It is, however, best to explain what happens. A half-grown curved tendril of the Passion-flower is perhaps the most interesting to experiment with, but any sort of tendril does quite well. If one very gently rubs the inner or concave side of its little hook, then in a very few minutes, or even seconds, the tendril distinctly curves. If this has happened naturally, as when for instance it has been rubbing upon a pea-stick, this curve makes it curl round the stick, and the more it touches the more it curls, until the whole tendril is wrapped round the support.
It is, of course, quite impossible to explain it all exactly: the sensitive part on the inside of the curve differs from the outside or convex part of the tendril; the former has a layer of elongated, thin-walled cells, full of the living matter, protoplasm, which are absent on the outer side. Immediately the tendril touches the stick, the outer convex surface begins to grow rapidly. It grows from forty to 200 times as fast as the inner side which touches the stick! Very soon after it has clasped the stick the tendril becomes woody and forms a strong, woody, spiral coil.
These tendrils can be made to curve by a weight exceedingly small. The most sensitive part of our own skins is quite unable to distinguish so small a weight as is perceived by these tendrils. Even the sensation of taste can only be produced by a weight eight times as great as that shown by some of them. Tendrils curve very quickly after they have been touched. In twenty seconds some tendrils curve (Cyclanthera), others (Passiflora) take thirty seconds, and some of them require four to five minutes or even longer before they make up their minds to coil.
Even more remarkable, however, is the fact that they do not coil when raindrops fall on them, giving a much harder blow than small weights. If one tendril touches or rubs against another, it is said not to curve. They are persevering little things also, for Darwin got a passion-flower tendril to curve when struck or rubbed no less than twenty-one times during fifty-four hours.
If one reflects on all these curious facts, it is difficult to help feeling that these plants behave very much in the way that a reasonable animal would do. There are many other cases in which some vegetable does exactly what we should expect of reasonable beings under the circumstances. The tipof the root (see p.89), the Sensitive Plant, the Monkey and Barberry flowers, are all well-known cases.
So that it is difficult to find anything in science to contradict the comfortable belief that wide-open flowers and stretched-out leaves of plants as they drink in the warm rays of the sunlight are really enjoying themselves, whilst they are doing their day's work.
All these interesting facts are so beautifully described and so carefully summed up by Charles Darwin, that we shall only earnestly recommend our readers to get first that fascinating bookThe Power of Movement in Plants, and then read all the rest of his works.[141]
There are an extraordinary number of these plants and the tendrils are formed exactly where they will be most useful. Every part of a leaf may become a tendril. The whole leaf is changed into one in some kinds of Lathyrus. In a very beautiful creeper which is not so often grown in greenhouses as it might be (Gloriosa superba), the tip of the leaf only acts as a tendril. Leaflets are often made into tendrils. The Clematis is the most economical of them all, for the leaf-stalk coils round and forms little woody rings which hold up the plant.
Before leaving the subject of tendrils, it may be interesting to notice the queer corkscrew spirals in which they roll themselves up. These spirals are formed after the end of the tendril has tied itself to the support and become woody. The free part between the end and its own stem goes on revolving; now if you tie a piece of string at both ends and make it revolve, you will see at once that it must coil itselfinto a double spiral, one part in one direction and the other in the opposite way, with a flat piece between them.
One might be disposed to think no more about these double coils; but here comes in one of the curious, inexplicable coincidences which happen so often in plant life. Such a coil is much stronger than a straight bit of wire or string would be, because if pulled out it yields and is springy. That of course makes it less probable that the tendril will be broken. Attached by a series of wiry springs, the plant yields and sways to the wind, and it is not likely that it will be torn away. Besides this, the coiling of the tendril pulls the stem closer to its support, which is also a great advantage.
Certain Virginian Creepers and Vines behave in quite a different manner. The tendrils grow away from the light and so seek the shadow of the leaves. They are also divided into little branches. At the tip of each little branch is a small knob; if this should touch the wall or the trunk of a tree, etc., it immediately secretes a drop of cement and glues itself firmly to the wall. There is a curious difference in different sorts ofAmpelopsisin this respect. There is no adhesive pad in one of them (Ampelopsis hederacea) until it touches, whilstA. Veitchiihas them more or less ready for gluing before they touch (though they become much larger and better developed as soon as they rub against the wall).[142]
One of the most interesting of our common climbers, "that rare old plant the Ivy green," has not yet been mentioned. It is exceedingly decorative on walls, especially on ruins and on old tree-trunks in winter time, where its dark, brilliant green is most effective.
A violent controversy rages as to whether it does good or harm. Unhappily it does not do any good to trees. It does not suck their sap, for its roots do not get through the bark, but it does choke, with its clinging branches, young tree-stems, and prevents their growing properly.
Also, in winter storms an ivy-covered tree is much more likely to be blown down. But on walls the ivy certainly does good, for it sucks up the moisture, and ivy-covered walls are much more dry inside than those which are exposed to rain.
Its method of climbing is very curious. All along the stem quantities of little roots are produced. They dislike light, like most roots, and creep into crevices and cracks, where they wedge themselves in by growing thicker. Thus the stem is anchored all along its length. It is curious to find that these roots are formed before a twig is actually touching the wall, so as to be ready for any emergencies.[143]
One interesting little point in the growth of the ivy on a tree is perhaps worth mentioning. The main stem runs nearly straight up the trunk, and when young is pulled down into the crevices or cracks in the bark. But its branches leave the main stem at an angle of forty-five degrees or so to it; these latter may often grow in this direction for a foot or eighteen inches, but then they gradually begin to turn more and more distinctly up the tree. Still these branches firmly clasp the trunk like arms spread out on either side of it, and make it almost impossible to dislodge the main stem.
Old plants of ivy entirely surround the trunk. The flowering branches grow straight out into the air, and have no tendency to cling to the bark. Their leaves are also different.
The ivy may be considered as a root-climber, although the branches assist by growing round the stem.
A curious instance has been given me of the longevity of ivy and its power of clinging to life. A correspondent mentions the case of a Scotch fir whose life was threatened by an ivy. The trunk of the ivy was sawn through. That did not kill it, at any rate immediately!
Probably the rain soaked up by the leaves, and by the roots in the crevices of the bark, kept it sufficiently fresh to cling to life. As it refused to die, a ladder was brought, and it was dragged off the tree. No doubt it would have died if the weather had been at all dry.
There are some very beautiful tropical plants which also climb by means of their roots. These roots, the so-called girdle roots, grow right round the stem and embrace it, so that the climber is perfectly supported.
It is impossible not to be impressed with the extraordinary variety of all these contrivances by which plants are able to escape the trouble of supporting themselves. But such ways of life involve certain disadvantages. Supposing there is nothing on which to climb, the stems trail feebly on the ground, and are probably soon choked by the surrounding grasses. Curiously enough, there are varieties of the Ivy, Wistaria, and the French Bean which are upright, and do not climb at all. The Tree Ivy has all its leaves like the leaves of the flowering shoot in the common form. In America,Wistaria sinensisis often grown as a standard tree, and does not send out the long shoots, sometimes thirty feet in length, which are common when it grows on walls. The dwarf French Bean has a thick stem and requires no support, yet it often puts out a long slender shoot which tries to twine round something.
In a tropical forest also, the creepers, though they damage the trees, yet manage to find space for their leaves and flowers: more vegetable matter is formed per square yard of ground than would be the case if there were no climbing plants.
The kinds of cannibals—Bacteria—Spring flowers—Pale, ghostly Wood-flowers—Their alliance with fungi—Gooseberries growing on trees—Orchid-hunting—The life of an orchid—The mistletoe—Balder the Beautiful—Druids—Mistletoe as a remedy—Its parasitic roots—The trees it prefers—TheCactus Loranthus—Yellow Rattle and Eyebright, or Milk-thief, and their root-suckers—Broomrape and toothwort—Their colour and tastes—The scales of the toothwort which catch animalcula—Sir Stamford Raffles—A flower a yard across—The Dodder—Its twining stem and sucker-roots—Parasites rare, degenerate and dangerously situated.
THE wordcannibalis often used in a very loose and unscientific way. Amongst some savage tribes it is the custom to eat old people and young children; but this is only in seasons of famine and scarcity, when there is no other food available, and not because they are specially fond of them. But amongst other tribes wars are made for the special purpose of capturing fat young people to cook. Sometimes they have become so accustomed to such delicacies that they are unable to get their food in any other way. Of course, when tribes become "pure cannibals" of this last type they have to be destroyed like wild beasts.
Among plants we find all sorts of transitions and degrees of cannibalism. There are plants which sometimes, and, as it were, accidentally, attack others. But there are also real cannibal plants which live entirely on the life-juices andsap of other plants, and cannot exist by their own labours at all. Moreover, we can find almost every conceivable state of transition. These can be clearly and definitely traced from those plants which depend on the labour of their own roots and leaves to others which have no leaves, and which consist merely of one large flower and a large adhesive sucker fixed on some one else's root.
The difficulty is very often to know where to draw the line. Probably no flowering plant is quite independent of the labour and work of its neighbours. As we have tried to show in another chapter, a long preliminary cultivation by bacteria, lichens, and mosses is required before flowering plants can develop on bare rock. That is also necessary in all cases where the soil is mineral orinorganic, without anyorganicdust or fragments of vegetable or animal matter. Bacteria must always begin the work by preparing nitrates and other salts.
So that only those bacteria which weather rocks can be called really free and independent. But other bacteria, such as those which cause typhoid, anthrax, hydrophobia, etc., are the best possible examples of pure cannibals, or, as they are usually described, parasites.
This last word is derived from a peculiar class of people in ancient classical times, who used to appear whenever a meal was going to begin, and received food without giving anything in return. They are represented by our tramps or by the "sundowners" in Australia, who appear as soon as the evening meal is ready and when there is no possibility of going any further on their journey.
The way in which plants became parasites or cannibals is a very interesting part of plant life, and we shall try to trace some of the various stages.
To begin with, if one looks out for them in spring one is sure to find a whole series of beautiful spring flowers. There is the Primrose, with its bright, hardy, yellow flowers; the Violet, whose strong perfume much annoys the huntsman, for it spoils the "scent" and shows him that the end of winter has come; the delicate little Moschatel, the Lesser Celandine, the Bluebell or Hyacinth, Dog's Mercury, the Male and the Lady Fern, and many others.
Most of these begin to grow and are in flower early in the season. That is because they are living on thedead leavesof the last year, or rather of two or three years ago. Their roots are breaking up and devouring, with the help of worms, beetles, and insects, the leaf-mould of past seasons.
They are quite dependent on the trees; they cannot exist except where such leaf-mould is formed.
But it is very difficult to tell whether these humble little herbs which live on the scraps that fall from the tall trees are either parasites or clients, which last do some good in return for their share.
Probably they are distinctly useful and good for the forest if this is considered as a wholeestablishment. They use light which would otherwise be wasted, and their own dead leaves increase the annual deposit of leaf-mould.
There are other plants, such as the Bird's-nest (Neottia) and Coralroot[144]Orchids, as well as Monotropa and others, which also live on the rich, decaying leaf-mould of forests, but these are generally pale in colour, for they possess but little green chlorophyll. They are more directly dependent on the mould and have ceased to do much work for themselves.Most of them in fact have entered into an alliance with fungi, and use these fungi to get their food material from the dead leaves.
Such fungi are always abundant in good, well-grown forests (see p.86). These Orchids and Monotropa have their roots and underground stems covered and wrapped round by the fungus threads, which extend from them in every direction, breaking up and decomposing the dead leaves.
The colour of Monotropa is a pale waxen yellow, that of the others is usually a ghostly pale, opalescent, steel-blue or coral-like hue, which makes them very distinct in the dim, mysterious shades of the forest.
These plants are undoubtedly of use, for they break up and decompose the leaf-mould.
Another very interesting group are not well represented in this country. Sometimes one may see on an old tree a Gooseberry bush in full foliage quite high up the trunk in the fork of the branches. In sheltered woody ravines, Polypody ferns are often established on old moss-clad branches, where their green fronds hang over to catch as much as they can of the sunlight. But Orchids, Bromeliads, and Ferns which grow upon the branches of great trees are one of the most conspicuous and beautiful features of tropical woods. It is for these tree-orchids that the orchid-hunter braves the head-hunters of Borneo or traverses the precipices and rugged forests of Guatemala and Brazil. It is often necessary to cut down a tall tree in order to get the orchids in its higher branches. Often, however, this is unsuccessful, for the tree is so held up by creepers and other giants of the forest that it never reaches the ground!