African india rubber is mostly exported from the west coast. The belt of country producing it extends nearly across the continent. Those who are familiar with the india rubber plants of our conservatories are apt to think of the gum as the product of trees, but in Africa it is largely yielded by climbing plants of very numerous varieties, belonging generally to the Landolphia species. It is collected by the natives by careless or desultory methods, probably less advanced than the ways followed by the South Americans. Possibly its marked inferiority may be partly attributed to this. It is also supposed by many that, were the gathering restricted to the vine producing the best gum, better results would follow. As it is now all gums are mixed indiscriminately. African gum is of very inferior quality.

The African india rubber vines grow often in dark moist ravines, where no valuable product other than themselves could be cultivated. They are entirely wild. The vines when cut exude an abundance of sap, which differs from the South American product in its quickness of coagulation. As it escapes from the wound it at once solidifies and prevents the further escape of juice. The negroes are said to employ the following highly original method of collecting it. They make long gashes in the bark. As fast as the milky juice comes out they wipe it off with their fingers and wipe these in turn on their arms, shoulders, and body. In this way they form a thick covering of inspissated juice or caoutchouc over the upper part of their body. This from time to time is removed by peeling. It is then said to be cut up and boiled in water. This is one account. According to others the natives remove a large piece of bark, so that the juice runs out and is collected in holes in the earth or on leaves. Wooden vessels are said to be used elsewhere. Sometimes the juice is said to be collected upon the arms, the dried caoutchouc coming off in the shape of tubes. A clew to the inferiority of African india rubber is afforded by the statement that too deep a cut liberates a gum which deteriorates the regular product if it mixes with it. The drying of the gum is thought to have much to do with its quality and it is highly probable that this affects the African product. Some samples seem to be partly decomposed they are so highly offensive in odor. The South American rubber is often dried in thin layers, one over the other, by a smoky fire, which may have an antiseptic effect upon the newly coagulated caoutchouc. No such process as far as known is used in Africa.

The African india rubber appears under different names in commerce. From the Congo region lumps of no particular shape called “knuckles”; from Sierra Leone smooth lumps, “negro-heads,” and “balls” made up of small scrap; from the Portuguese ports “thimbles,” “nuts,” and “negro-heads;” from the gaboon “tongues;” and from Liberia “balls” are received. It is all characterized by great adhesiveness and low elasticity.

From Assam, Java, Penang, and Rangoon there is considerable gum exported. It is supposed to be the product of trees of the ficus species, in all these places, as it is known to be in Java and Assam. In the latter place rigid restrictions are imposed as far as possible upon the gathering. In the case of wild trees scattered through the forest the carrying out of these restrictions is not practicable. The trees are cut with knives in long incisions through the bark and the juice is collected in holes dug in the ground, or often in leaves wrapped up into a conical form, somewhat as grocers form their wrapping paper into cornucopia shape for holding sugar, etc.

It has seemed reasonably certain that the india rubber producing plants might be cultivated with profit, and it is as certainly to be feared that without such cultivation they will become extinct. Efforts have been made in the direction of raising them artificially but without much success. In Assam numerous experiments have been made to propagate the india rubber bearing ficus tree.

A good instance of the ill effects of carelessness in the original gathering of the crop is afforded by the Bornese collectors. The source of Borneo india rubber is a variety of creepers. These are cut down and divided into short sections from a few inches to a yard in length. The sap oozes out from the ends. To accelerate its escape the pieces are sometimes heated at one end. It is coagulated by salt water. Sometimes a salt called nipa salt, obtained by burning a certain plant (nipa fruticans), is used for the purpose. In either case it is coagulated into rough balls and masses. These masses are heavily charged with the salt water, often containing as much as fifty per cent., and rarely much less than twenty per cent.

Central America and Panama are great producers of the gum. In Panama the custom of felling the trees is often adopted. In this case grooves are cut around the prostrate trunk, and under each groove as the trunk lies on the ground a vessel is placed to collect the sap. Its coagulation is often effected by leaving it for a couple of weeks standing at rest in a hole, excavated on the surface of the ground, and covered over with leaves. The caoutchouc separates under these conditions. A quicker method, but one yielding an inferior product, is obtained by adding to the fresh juice some bruised leaves of a plant (ipomæa bona nox) which acts something like acid upon milk, in separating the desired solid matter or caoutchouc. A jelly like accretion saturated with blackish water is thus obtained. By working it together a blackish liquid is caused to escape, and comparatively pure gum is gradually obtained. As much as one hundred pounds of india rubber may be obtained from a single tree where this destructive system is employed. Further north, where a better counsel has prevailed, the trees are only tapped, and the india rubber hunter is satisfied if from a tree eighteen inches in diameter he obtains twenty gallons of sap, giving fifty pounds of gum. Even where tapping is done the tree is often destroyed by carelessness or ignorance.

Two systems are followed in Nicaragua. The operator ascends by a ladder if he has one, or in any case climbs as high as he well can and begins to make a long incision. Sometimes he carries one long straight cut clear down to the ground. This is made the starting point for a number of side cuts, short, and running diagonally into it. This is also one of the Brazilian methods. The Nicaraguan sometimes also makes two spiral incisions, one right-handed and the other left-handed, crossing each other as they descend so as to divide the surface of the tree into roughly outlined diamonds. In either case the juice flows down to an iron spout, placed at the bottom of the tree, which spout leads to an iron pail. The milk is gathered and passed through a sieve, and coagulated in barrels by the ipomæa plant as before mentioned. This gives three grades of rubber. The bulk is obtained from the barrels and is called often méros; the small lump which forms in the spout is rolled into a ball and called cabezza; the dried strips pulled out of the cuts is of very good quality and is called bola or burucha.

From Brazil is exported the famous Para india rubber. This is of very high quality, and is greatly esteemed by all manufacturers. No process can make a poor gum give a really good product. The system of gathering it varies. Sometimes the tree is cut into by gashes from an axe, such gashes extending in a row all around the trunk. Under each gash a small clay cup is luted fast with some fresh mixed clay. These collect from a tablespoonful of juice upward, which is collected, and the cups are removed on the same day. The next day a second row of cuts is made below the others, and the same process is repeated. This is continued until from a point as high as a man can reach, down to the ground the tree is full of cuts. Sometimes a gutter of clay is found partly around the trunk with gashes above it. In other cases a vine is secured around the tree and a collecting gutter is worked with it for a basis.

The juice is coagulated in a smoky fire. A bottomless jar is placed over the fire and some palm nuts are mixed with the fuel. The mould, which is often a canoe paddle, is smeared with clay to prevent adhesion and is then heated. A cup of juice is poured over it, and after the excess has dropped off it is moved about rapidly over the smoke and hot air which ascends from the mouth of the jar. This series of operations is repeated until the coating is quite thick; it may be as much as five inches. After solidifying over night it is cut open and the paddle or mould is removed. After a few days drying it is sent to market. With all the heating, during which it sweats profusely, it still retains fifteen per cent. of water.

India rubber sap may be coagulated by an aqueous solution of alum. The process has been tried in Brazil, and is used to a considerable extent in Pernambuco. It was proposed by an investigator named Strauss, and the process is still called by his name. One objection is that it gives a very wet product, and apparently one of inferior value to the smoked gum.

The feeling that india rubber suffers in the gathering has been so much felt that it has been recently suggested that if possible the uncoagulated juice should be exported to Europe there to be worked up from the beginning.