Page:Popular Science Monthly Volume 85.djvu/451

Rh In 1876, some seeds of Hevea brasiliensis were sent from Brazil to Kew Gardens, and some young plants from these seeds were shipped the same year to Ceylon, where they were planted in low land and the grove then started is now historic, for it was the beginning of the later industry. Up till 1899 there were only about 750 acres of rubber plantation in Ceylon and these were apparently not intended for commercial purposes. In 1899 the first company in the Malay States was formed and it declared a dividend of 75 per cent, in 1908, and owing to the high prices or rubber in 1909 the dividend was 250 per cent.

The large amount of rubber required for automobile tires naturally stimulated the planting of rubber areas. According to figures given in a U. S. Consular Report in January, 1913, the acreage in Ceylon in 1912 was 220,000 and in the Malay States 430,000, while in other countries over 100,000 acres were under cultivation. Figures given later in the year by The Economist were higher. The larger part of this area is not yet productive, and some of it will not yield for five or six years.

The source of cultivated rubber is almost entirely Hevea brasiliensis, which seems to be adapted to wide differences of conditions. In Ceylon, though first planted in low land, it grows on hills with large boulders, in the Malay district it thrives on flat land with hardly a stone. On the Malay hills, where heavy rains would carry away the young trees, contour drains are constructed. The genus Castilloa does not grow so readily in the East; it takes longer to reach the producing stage and it does not produce so much rubber when it has attained its proper growth. It has, however, been largely planted in its original home, Mexico. Manihot-Glaziovii is planted in dry regions, where Hevea does not flourish.

Hevea is not fit for tapping till it is seven years old. As the seven or eight feet nearest the bottom of the trunk are richest in latex, the object in cultivation is to produce short trunks of large circumference. With this end in view, the trees are planted far apart, at a distance of about twenty feet from each other, giving approximately a hundred trees to the acre. They are induced to fork at a height of about ten feet, and it is said that the best arrangement is a tripartite forking of the main trunk, each branch in turn forming three subordinate branches. In places where there are high winds, however, this style of forking may provide so large a surface that the trees may be blown over.

There are various methods of tapping, the most satisfactory apparently being full or half "herring bone." A vertical groove is made in the bark of the tree from the base to a height of five or six feet. Then parallel incisions are made from this vertical groove in an upward slanting direction, in the case of the half-herring bone, on one side, and in the case of the full herring bone, on both sides. So important is it to cut through the laticiferous vessels without injuring the cambium layer and so difficult is it to accomplish this kind of incision, that dozens of