Articles taken from the “ Twentieth Century Impressions of Ceylon “ printed by Lloyd’s Greater Britain Publishing Company Limited in 1907
THE TWENTIETH CENTURY IMPRESSIONS OF CEYLON – 1907
By HERBERT WRIGHT, A.R.C.S., F.L.S.
The development of the rubber industry of Ceylon Has attracted the attention of almost every one interested in topical economic botany, and the prospects of its future have aroused the investing public to a degree which is described as being unparalleled in the historic of other products which have had their day. Planters are eager to experiment with soils in districts which have hitherto been disregarded. Efforts have been made to grow rubber-yielding plants in the north, south, east and west of the island at altitudes ranging from sea-level to over 5000 ft. Already it is possible to say that certain species will only thrive under certain climatic conditions, and a centralization of individual species over large areas having similar climatic is now manifest.
At the present time but few Ceylon estates have large acreages of rubber-trees in bearing, and it is with surprise that one realises how keenly and thoroughly the methods of collecting, purifying coagulating, drying smoking, and forms of preparation have ben already taken up in the island.
The amount of rubber annually exported from Ceylon is small, but the knowledge which has been so eagerly gained concerning its preparation, and the freedom with which it has been circulated, will materially help the industry and assist all t place it on a sound basis long before the large acreages are in bearing.
Rubber consists of the dried milk or latex of certain plants. n the temperate and subtropical zones several species possess lactiferous systems: the number of these in the tropical zone is very often considerable.
Plants processing latex are distributed in various parts of both hemispheres, where they grow a variety of conditions, sometimes on hilly land, sometimes on alluvial plains, and also in swamps and desert areas. Some of the rubber plants are shrubby in character, notably the Guayule. (Parthenuimargentatum) others have a climbing habit, such as Landolphias and Willughbcias: but most of those which are of considerable importance from large trees, often measuring nearly a hundred feet in height, and frequently over 9 ft. in circumference. To the last group belong the Funtumia trees of Africa, the Castilloa, Para, and Cears rubber –trees of tropical America. Gutta Rambong and species of Sapium and Palaquum in the Indo-Malayanegion.
In Ceylon a large number of plants are known which yield rubber of commerce. There are several species of Ficus, Sapium ,Bassia, Palaquum, and Willughbeia which yield lattices processing high percentages of resin, and there are also several introduced species, such as Palaquum Gutta, Payena Leerii, Sapiumbiglandulosum, & c., which, though they yield varying quantities of caotchouc,a have not yet taken a place in the rubber industry of Ceylon.
The sources of rubber in Ceylon are mainly Heveabrasiliensis, Mull.-Arg., which yields the Para rubber of commerce; Castilloaelastica, Cerv., Panama rubber; Manihotglaziovii, Mull.-Ard., which gives the Ceara rubber of commerce; Ficuselastica , L., the source of GuttaRambong, and the Landolphia vines. It is interesting to note that the three most promising forms of rubber in Ceylon-Para, Ceara, and Castilloa-have all been introduced from other topical counties, and that at the present time not a single native or indigenous species is known in this island which promises to produce rubber in quantity and quality sufficient to make it a commercial success.
Though rubber trees had been known for many years, it was not until about 1875 that they were seriously considered suitable for experimental cultivation in Ceylon. Various expeditions were sent out to tropical America by several countries, and this island ultimately obtained Castilloa, Ceara, and Para rubber plants in 1876 and 1877.
In the early days the planters appeared to have more confidence in their quick-growing Ceara rubber plants, but finding that they did not give profitable yields after a few years waiting, they were either left to grow in the wild state of were cut down to make room for other products. Ceara rubber–trees grow well in many climates, and have been successfully reared in the dry, arid, northern parts as well as in the damp, cooler parts of the south of the island. This species grows from sea-level to over 4,000 ft., and has at the present time, a wider distribution on Ceylon than any other introduced rubber-yielding species.
Castilloa rubber cultivation appears to have been taken up seriously at a later date, but at the present time owing to difficulties in obtaining a free flow of latex and a sufficiently large quantity of rubber therefrom, is showing signs of being neglected, and on several estates is being cut down to make room for Para rubber trees. Castilloa rubber-trees grow best where the temperature never falls below 60 .F And in districts with a well-distributed rainfall of at least 70 ins. They have been tried in the Kalutara, Matale,Dumbara,Peradeniya and Passara districts, and, though they grow very rapidly in the first three years, do not appear to give as favorable results as those of Pra rubber.
Para rubber trees are being successfully cultivated in districts with a rainfall of 60 to 120 ins., and encouraging results have even been obtained in relatively dry districts, and in some with a high rainfall.
The Para rubber districts of Ceylon range from sea-level over 3000 ft., though the best results have been obtained below 2000 ft., where the average annual mean temperature varies from 75 to 81 F .and the rainfall from 70 to 120 ins. Para rubber to-day appears to be the favorite, and the extension of its cultivation has been influenced or determined by the results obtained during many years of patient waiting and working. The opinions of many persons vitally concerned in the Ceylon rubber industry is that, where Par rubber-trees will grow, they can be cultivated as the mainstay of the estate.
The rate of growth and present immunity from pests of Hevea Brasiliensis put it, in Ceylon, above Funtumia; its yielding capacity places it on an equal or even higher plane than the best Castilloas, and it’s hardly characteristics and response to the extensive use of the ordinary tapping knife appear to render is superior to Ceara and other rubbers. Para rubber-trees, as far as can be judged-in growth, hardiness, and yielding capacity-are superior to many other rubber-trees, The confidence in this species is not confined to Ceylon, but has spread to many islands and territories through-out the tropical zone.
Planters in the Indo-Malayan region are unanimous in their opinion, and trees of Cears, Castilloam, and GuttaRambong are often felled in order that Para rubber-trees may be planted or their growth encouraged. Africa or at least the West Coast of that vast continent, will take as many seeds ofHeveabrasiliensis as we can give, because it has been found to be superior to others native in that area. Even during this year thousands of seeds for planting purposes, have been sent to Brazil- the country whence all our Hevea rubber seeds were obtained in 1876.
The cultivation of Gutta Rambong and Landolphia is in a backward state in this inland, and it is not likely to develop at a rapid rate if considerable improvements are not evolved. Trees of Gutta Rmbong are somewhat difficult to establish, and owing to the enormous size which they attain, are planted at very wide distances from one another, thus allowing only a small number of trees to each acre. A few estates at a high elevation possess a small number of trees.
The landolphias are creeping plants, and must be grown among other trees if success is to be attained; they appear to thrive at Heneratgoda. Gutta Rambong trees and Landolphia vines do not yield good rubber until they are many years o9ld, and do not appear to be regarded in Ceylon with as much favor as is even Ceara and Castilloa, and for the purposes of his article they may be disregarded.
The development of the rubber industry in Ceylon should not be associated exclusively with the fact that excellent rubber-yielding trees have been acclimatized.
The impetus to the planting of rubber-trees is partly due to the discovery of improved methods of tapping, of new paring and pricking knives, to information regarding the best frequency for tapping, and to the invention of machinery for smoking, coagulating, drying, and blocking of rubber. Simultaneously with these general improvements there has been a rise in price to over 6s. a pound for some samples of plantation rubber, and this alone has been responsible for much of the activity during the last few years.in 1892, when the price of some samples of plantation rubber was 2s. 10d. per pound, the planted areas in Ceylon was only 400 acres. In 1903 when the price was 5s a pound, 7,500 acres were planted in Ceylon; in 1995, when the price rose up to 6s ; the planted acreage roe to 40,000 acres ; and now, at the end of 1906, when the prices range from 5s.3d. to 5s. per pound. Ceylon alone can claim over 100,000 acres of planted rubber, and promises in the near future to far exceed its already large acreage.
Rubber trees are sometimes cultivated as a single product, and frequently very large blocks of land are planted with one kind only. On several estates he Para rubber-trees are inter-planted with ta and cacao, and appear to give profitable results, especially with the latter product. Where the rubber is first planted alone it is customary, on a few properties, to plant catch crops in the form of chillies, cassava, lemon grass, cotton, and other products which may give a return during the first or second years. Where such catch crops are not used it is customary to regularly weed the whole of the estate, or to interplant herbaceous green manures (Crotalaria and Vigna species) or leguminous trees such as Albizziamoluccana and Erythrinalithosperma.
Before plantation operations are commenced it is usual to cut down and burn the vegetation on the forest of chena land ; the cleaning is then lined and holed, and when suitable weather arrives the seeds or young rubber plants are put out. Ceara plants may be easily propagated from cuttings, but most species are in Ceylon grown from seed only.
Ceara, Castilloa and Para rubber-trees are planted at distance varying from 10 ft. to 30 ft. apart, according to the local conditions prevailing. They require approximately the same distance in similar stags of their development. Each species regularly sheds the whole of its foliage after it is three to five years old, during the hot and dry part of the year. The Ceara rubber-trees remain leafless for several weeks or months, while the Para and Castilloa trees are leafless for only a few days or a couple of weeks each year.
Thirty-year-old trees of Para rubber often grow to an enormous size, producing stems 90 ft. in height and 109 ins, in circumference. They tend to produce taller trees, for a given age, than either Ceara or Castilloa, The Ceara rubber-trees though do not produce such tall stems as either Para or Castilloa, are characterized by a low and spreading branch system, and rarely grow to a height much above 40 ft. Castilloa rubber-trees are considered to require shade, and species of Erythrina andalbizzia have been used for such a purpose.
The methods adopted in tapping, collecting, coagulating, washing, and general preparation of rubber are somewhat similar for each of the three species. The latex is extracted from the trees by making incisions in the cortex or bark of the trunk and branches, this being done in such a manner as not to injure the trees. With Para and Castilloa rubber-trees the outer rough bark is simply cleaned by hand, but with Ceara rubber 0treesd it is often necessary to remove the thin, hard outer bark before tapping operations can be commenced. The incisions in the trees may take the form of a V. a single oblique cut, V’s joined by a vertical line to form a herringbone arrangement, or long spiral lines. This operation is usually carried out on the trunk from the base to a height of 6 ft. occasionally the first branches and the height of 20 ft. are tapped. In each case the incision is made carefully, to avoid damaging the cambium, and the line is made on a gradient to allow a flow of latex among the lower surface of line of excision from above downwards. Water, either from bottles or drip-tins, is allowed to flow along the cut In order to accelerate the flow of latex and to prevent coagulation from taking place in the cut.
In most of the systems of tapping the operator commences at the highest point and repeatedly pares of the surface of the lower edge of the bark (cortex) until he has completely stripped it to the base of the tree. At each paring or shaving operation only a small piece of the dries corky tissue is removed so as to reopen the latex tubes; on certain days, instead of paring the lower surface, rotatory or comb pricker is used, the teeth of which penetrate the inner cortex and cut or prick the latex tubes. The tapping operation is performed at intervals varying from twice per day to once per month on individual trees. It is therefore obvious that by the method of extraction of latex at present employed the lactiferous system is temporarily depleted, cut and torn, and a large quantity of the bark or cortex is cut away. The latex tubes Par and Ceara rubber trees do not arise from internal tissues and push themselves into the cortex, but by a process of decomposition of the partition walls of the cortical cells. The bark or the cortex, which is thus the mother of the future lactiferous system is during paring operations, either partially or entirely removed from the tree at a time when the component cells possess reserve food material intended for the future use of the plants. The latex, as it issues from the tree has a milky appearance, and in very dry weather is apt to coagulate t the point of issue or in the cuts.
When large quantities of latex have been obtained in the liquid condition, they are removed to a central factory. On arrival at the factory the latex often contains a large proportion of foreign matter, such as sand and pieces of bark. These mechanical impurities are removed by filtering the latex through thin porous cloth or by means of a centrifugal machine made to revolve at the rate of about 3,000 revolutions per minute The Latex thus freed from some of its impurities is then either accumulate in settling tanks or placed in coagulating receptacles. Sometimes it is smoked by being passed through an apparatus charged with the smoke from smoldering logs of wood which have been soaked in creosote; this operation is often considered advisable in order to prevent subsequent softening of the rubber.
In coagulating the latex different methods are adopted. In the first method is poured into a barrel-like receptacle; acetic acid is added, and the apparatus made to revolve. The coagulated latex accumulates in the centre and the watery portion on the outside. When he latter is no longer turbid the coagulation of the latex is considered perfect and the rubber removed. In the second method acetic acid is added to the latex which has accumulated is large settling tanks and the rubber allowed to accumulate on the surface. The third method-often spoken of as the natural one-consists in allowing the latex to undergo ordinary putrefaction. If the latex is allowed to stand in any receptacle some of its constituents decompose and give rise to acidity; this is followed by coagulation, when the rubber rises to the surface.
The freshly coagulated rubber is soft, pliable, and spongy, and while in this condition is subjected to much stretching and washing. The washing machines is use in Ceylon consist essentially of pairs of metal rollers running at uneven rates. They are supplied with a pipe which delivers cold or hot water between the rollers. The rollers are usually fluted horizontally or spirally, and when the rubber is placed between them it is thoroughly pressed, stretched, and washed. The rubber, after it has gone through the rollers, is usually free from all mechanical impurities; the superficial or soluble ingredients are considerably reduced in quantity; it is often much torn and irregular in outline, and is subsequently passed through smooth rollers, there to be finished off as crepe rubber.
Where the freshly coagulate rubber is not passed through a washing machine it is generally allowed to set in circular or rectangular receptacles, and is turned out in the shape of biscuits and sheets. In other cases are freshly coagulated rubber is cut up into thin strips or “worms” and at other times converted into a lace-like mass this rubber. But whether in the form of crepe, biscuit, sheet, worm, or lace rubber, the prepared material possesses a large percentage of water, and hitherto the Ceylon Planters have generally tried to remove his moisture in order to be able to ship the rubber in a dry state. The drying is usually done in hot-air chambers, supplied with the minimum amount of light and a good current of hot, dry air. The wet rubber is either arranged on shelves or hung up on strings, and is allowed to stay in this condition for a few days or weeks until the moisture content is less than 1 per cent. The time taken in the hot- air drying process is a great disadvantage, and a few estates are contemplating the introduction of vacuum dryers, which by means of high temperatures and low pressure, enable the operator to sufficiently dry the rubber in a few hours instead of days. It is not unlikely that several planters will to a large extent dispense with drying process and ship heir rubber in large rectangular blocks containing as much moisture as the rubber which is exported at the present time from tropical America and Africa. Rubber processing 20 per cent. Of water may be sent over long distance without deteriorating providing it has been properly treated with antiseptics.
The biscuit, sheet, crepe, worm, lace, and scrap rubber is usually sent from Ceylon in rectangular boxes made to hold one or two hundredweight. Some of these especially the biscuits, are difficult y pack and in all cases a very large surface on rubber, per unit of weight, is exposed to the air. In order to overcome the disadvantages associated with the original and more recent forms in which plantation rubber is exported, several planters have adopted 5he “block” rubber devised by Mr. Pears, of Lanadron Estate, Johore. Each block of rubber is rectangular in form and may weigh from 25 to 30 lbs. or even more. The block is made from partially dried crepe rubber, but there is no reason why it should not be made from lumps of freshly coagulated latex if the presence of moisture and antiseptics is not objected to by the Home manufactures. Block rubber has also been made in Ceylon by pressing biscuits which had been kept in a dry state for several weeks, and though the immense pressure obtained by a large screw-press made a satisfactory block, the lines separating some of the biscuit could be distinguished. The great reduction in area exposed to light and air by turning out the rubber in block form is manifest from the fact that 10 biscuits, each measuring 8 to 10 ins. In diameter, and 1/8 to ¼ in, in thickness, were pressed into one block measuring 12 x 12 x 5 ins. The weight of the block was approximately 26 lbs., and several such samples could be packed easily in one box for shipment. At the present time block rubber prepared well-washed and partially dry crepe rubber is in favor among Ceylon planters, though it may yet be necessary to make the blocks not quite so thick, but of larger area than those recently placed on the market.
It cannot be doubted that the feature on which the prosperity of the rubber industry depend are the yield of rubber obtainable and the period over which they can be guaranteed. Old trees of Ceara rubber trees given from 65 to 169 grams of dry rubber each is a period of three to four months, whilst others have given an annual yield of ½ to 1 lb. of rubber per tree for a few years in succession. Trees of Castilloa have given somewhat similar yields, and it is generally conceded that an average annual yield of 1 lb, of dry rubber per tree is rarely exceeded by either of these species. Para rubber-trees, on the other hand, have given far more promising yields, and much information has been published showing the results obtained on private and public properties in various parts of the island. A yield of 1 ½ lbs. of dry rubber per tree per year for nine years has been obtained from a few old Para rubber-trees at Henaratgoda. Estates in the Matale and Kalutara districts have given an annual yield of ¾ lb to 3 lbs. per tree, and during 1905 a known 138655 trees yielded 189743 lbs. of rubber individual trees at Henaratgoda have given 2, 3, 8, 10, 11, 12 and 15 lbs. of dry rubber each in eleven months, when tapped on certain systems, and it would not be an exaggeration to say that thirty-year old trees of Para rubber could be made to yield as much as 500lbs. of rubber each in one year, at the sacrifice of the tree. The manner in which tree of Para rubber have yielded to the use of paring and picking knives has occasioned much surprise, and though it is perhaps too early to make any definite statement as to the ultimate effects, the results have admittedly exceeded expectations.
One of the most serious troubles to the rubber planter is Ceylon is the liability of the prepared rubber to become soft and sticky during the course of drying or in the packing-cases during transit. The rubber first becomes sticky or tacky in local areas. These sticky patches spread, and the whole biscuit or sheet may rapidly soften and become almost liquid. The change is supposed to be due to the development of bacteria which live on the sugary, proteid, of foreign impurities in the rubber or latex. Rubber obtained from the first tappings of young and old trees appears to be especially liable to become tacky, but the change is due to a disease which may appear on the best rubber prepared without smoking, and be spread by contact. Its appearance may often be associated with the use of impure water, or insufficient washing. In one case rubber from thirty-year-old trees developed tackiness along the lines where the rubber, when drying had been in contact with strings of fiber. In order to keep this disease in check it is advisable to store and dry the rubber on dark rooms, and to effectively wash the freshly coagulated material. Any pieces of tacky rubber should be isolated, and the affected area either cut away or treated with formalin. Smoking the rubber and marking it into blocks is also said to reduce its liability to become tacky.
The latex of most of the rubber is, as it issues from the tree, of a creamy white colour, faintly alkaline or neutral, and rapidly turns acid and coagulates on exposure to the air. By the addition of ammonia or formalin it may be kept is a liquid state indefinitely. The composition varies according to the age, season, and section of the stem from which it is obtained, but as a general average that from Heveabrasiliensis processes 50 to 55 per cent of water 30 to 40 per cent. of caoutchouc, 2 to 3 per cent of proteid matter, 2 to 4 per cent of resins, and varying proportions of other constituents. The proportions of resins and proteids appear to be higher in the lattices from Ceara and Castilloa rubber trees. In the same tree the percentage of caoutchouc often shows a decrease in young trees, branches, of old trees, or when obtained from the reneved bark of tapped areas.
During the coagulation and drying process it is obvious that the main loss is water and ingredients of the latex which remain in solution in the mother liquor. When the rubber is subjected to washing and rolling superficial and soluble ingredients are largely removed, so that the proportionate composition of the final dry product may be slightly different from that of the original latex. Samples of dried Ceylon rubber process from 76 (Ceara) to 86 (Castilloa) and 95 (Para) per cent of caoutchouc, from 2 to 12 per cent of resin 0.8 to 8 percent of protieds and other ingredients. By a change in methods of coagulation and preparation it is possible to considerably change the percentages of the caoutchouc and, other constituents. The elasticity, resiliency, colour, and odour of Ceylon rubber vary according or the species, age of trees, and methods of preparation, Ordinary rubber reacts with chlorine, bromine, acids, alkalies, sulphur, & c it rapidly swells when immersed in water, and becomes sticky when subjected to high temperatures. Quite recently the desirability of colouring, and sulphurising the latex before coagulation, and coating or mixing it with various mineral and fibrous substances, has been publicly discussed, but as yet no definite commercial importance has been associated with such changes in preparation and manufacture.
In connection with other products, especially coffee, cacao, and also tea and coconuts, the planting community have realised that pests of some kind or other usually make their appearance when large acreage of the same species are planted, that it pays to keep a sharp look-out for parasitic fungi and insect pests, and to attack them while their numbers are small. The rubber plants in Ceylon suffer from the attacks of root, stem, and fruit pests, but by isolating, spraying excising or destroying affected specimens he injurious insects and fungi are easily controlled, The list of insects and fungi known to attack the various parts of rubber plants from the nursery to maturity is a very long one, but up to the present none have been recorded which are incapable of being effectively dealt with.
In the early days of the Ceylon rubber industry, most of the rubber –producing species-Para, Castilloa, and Landolphias – were considered suitable only for place at or near sea-level and even Ceara rubber-trees were tried mainly below 2,000 ft. altitude. Para rubber-trees were, whenever possible, planted along the banks of rivers, where, owing to occasional floods, the conditions in the Amazon Valley-the hone of the Heveabrasiliensis-might be as nearly as possible imitated. Experience has shown that this species can be successfully grown not only on alluvial banks, but on poor cabooky and even swampy land, when the latter has been well drained. The climate and soil conditions under which it has been prove 1 that our introduced rubber-trees and vines can be grown have aroused the interest of all persons and institutions concerned with tropical cultivations, and it would be difficult to forecast the ultimate effect which the publication of the results of our experience will have. Certainly every one now knows that there are thousands of acres which can be made to grow rubber-producing plants, not only in parts of Ceylon at present under forest and chena, but in the Malay, Archipelago, West Indies, Africa, and South and Central America. Ceylon is under a disadvantage when compared with many parts of Africa and Tropical America, as it does not process any endemic or indigenous rubber-trees of value, and the whole of the forest has to be cleared and four to six and seven years allowed to lapse returns are obtained from the rubber plantations: whereas, in the forest of many other counties, an immediate return is obtained from the rubber-trees already in the forest at a time when the price paid for rubber is very high.
The future of the Ceylon rubber industry is intimately associated with that of the countries with that of the countries just enumerated, and the developments in all parts of the tropics will require constant and close study. Rubber cultivation in other countries is rapidly developing into a science and the areas processing indigenous rubber vines and trees are being surveyed, exploited, planted, and controlled by men of high scientific ability. In these circumstances it becomes necessary for Ceylon to carry out its land selection and planting operations in the best possible manner, to continue exercising every care to eradicate pests as soon as they appear, and for all planters to use the latest results of research in their attempts to place on the world’s markets the best specimens of rubber they can. The indo-Malayan region alone may, in a few years, be able to turn out rubber from one quarter million acres, and by that time must be prepared to meet competition from all parts of the world.
Of the many introduced rubber-trees which have been tried in Ceylon, but few can authoritatively be said to give less favourable results than in their native homes. Certainly, Funtumiaelastica trees are annually defoliated by an insect pest, the Castilloa trees do not quire give the yields which were originally expected, and Ceara rubber-trees have, in Ceylon, to be tapped with care. Oararubbe-trees, on the other hand, appear to be exceedingly hardy. Trees may be blown over and give of shoots with subsequently from upright stems capable of being tapped. Many can be made to yield several pound of rubber, though heir root systems are nearly all under water. The bark may be occasionally completely stripped with-out killing the tree; and fungi, and insect pests have hitherto not proved unsurmountable. The trees of Hevea brasiliensis readily produce large and paying quantitates of latex of high quality, and the future difficulty will probably lie in supplying the labour necessary to take full advantage of the trees which have already been planted. Even to-day, on estates which have a few hundred acres in bearing , labour difficulties are experienced , and should it ultimately be proved that the tree will stand tapping every alternate day throughout the greater part of the year, the question of labour may become serious. The best results appear to be obtainable when the trees are tapped in a definite manner, and according to a certain frequency, and if it is necessary to continue such, estate being tapped during particular seasons. In any case, it appears very probable that the tapping operations will ultimately be limited to the first 5 ft. or 6 ft. of the trunk, and that the collecting of latex above this height, involving a much increased labour force, will not be practicable.
It must be admitted that our experience of the effect of tapping, repeatedly extracting the latex, and excising that bark or cortex is still young. It is however, well known that the extraction of the latex, and nothing more, means the removal of a liquid which contains the minimum of reserve food, and essentially belongs to what are described as waste products. The lactiferous system is not of vital importance to plants, and, indeed, most of the native species in the island thrive luxuriantly without any vestige of such a system. In those plants where latex tubes occur, the latter are not vitally associated with the more important structures of the cortex, though, in periods of drought, they may serve some useful purpose. Trees of Para rubber which have given 10 lbs. to 25lbs. rubber annually, or the equivalent of about 20 lbs. to 50 lbs. of latex per year, appear to be almost as healthy as others which have never been tapped. The bad effect of tapping cannot, at present, be solely associated with the removal of latex, but with injury done to the cambium or healing layer and the mutilation and excision of the cortex while in a living condition. At the present time the methods of tapping involve the gradual paring away of the cortex from above downwards, and, though systematic and satisfactory s far as we have gone, maybe subject to much modification in the near future. From results which have already been published, it is probable that the extraction of the latex maybe done by incising instead the latex tubes; the more frequent use of pricking knives and shower rate of bark paring. The rapid paring away of the bark is an unnatural process analogues to the treatment meted out to cinchona in the past.
An important question arises regarding the suitability of the renewed bark to atmospheric conditions and various pests, The renewed bark is not at first protected by a hard, corky layer, similar to that which covers he original tissue; immediately following the removal of the bark in the paring operation a comparatively soft inner cortical tissue is exposed, which may prove to be less resistant than the original covering.