CHAPTER II.
THE NATURAL HISTORY AND COLLECTION OF INDIA RUBBER.
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.
Tree Felled for Collection of India Rubber.
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.