184 CTILIZATION OF KXDDED PRODUCTS. 



The Ficus elastica throws out numerous large aerial roots, some 

 of which run for many feet along the ground. Both the stem and 

 these roots are tapped, the latter being more productive. February- 

 March is considered the best time for tapping. Oblique incisions, 

 about 3 inches wide across the middle, are made ri^ht through the 

 bark. The exudations, if abundant, are received in conical cups 

 made of folded leaves (pots would surely be more convenient and 

 effective); otherwise they are allowed to concrete on the wound. 

 Native collectors often allow the milk to run down into holes made 

 in the soil. The incisions used to be made only 1 foot apart, but 

 this was found to weaken the trees. In the State forests an inter- 

 val of 2 feet is now adopted, and in tapping the same trees again, 

 the new incisions are made between the old ones ; if these latter 

 are opened again, not only do the trees suffer in vigour, but the 

 yield of milk is diminished 50 per cent. If the milk is left to it- 

 self, it solidifies in about 20 days, when it is stripped off the wounds 

 or taken out of the leaf-cups or holes in the ground, and kneaded 

 into a ball, whence the designation of hall rubber for this product. 

 Leaf or slab rubber is thus prepared. The fresh milk, collected 

 within 24 hours after incision, is poured into boiling water, and 

 the mixture is briskly agitated until the rubber separates and can 

 be handled without sticking and kneaded. A more elaborate plan 

 is to run the milk into wooden bins partially filled with water, on 

 which the rubber begins to float after a time. The rubber, while 

 still liquid, is removed and boiled over a slow fire in iron pans 4 to 6 

 feet in diameter and 2J feet deep, two parts of water being added 

 and the whole stirred constantly. When coagulated, the rubber is 

 removed with iron forks, pressed, again boiled and pressed, sun- 

 dried, and washed over with lime. 



The average yield of rubber is one-third the weight of the semi- 

 liquid latex. Ball rubber is obviously more impure than loaf rub- 

 ber (the impurities often reaching 35 per cent). Owing to lono-er 

 exposure to oxidation, while coagulating naturally, it also gives a 

 smaller yield. Even when loaf rubber is made, a certain quantity 

 of the ball kind is obtained from what collects subsequently and 

 solidifies in the wounds. The ball rubber, when just pulled off the 

 tree, contains about 17 per cent, of moisture, which, however, it 

 soon loses after being rolled up and sunned. 



The yield of course varies very much with the size and age of 

 the trees and the number of aerial roots, and with the weather. 

 Unseasonable rain may wash away almost all the latex. Middle- 

 aged trees are the most productive. Large healthy trees have been 

 known to yield as much as 150 to 200 lbs.; but the average yield 



