Markham asserts that the trees may be tapped at 25 years, and that after 50 years they will yh hl 40 lb. ot rubber every 3rd year. Murton says that in the Malay Peninsula the milk is obtained from tho largo roots, which aro tapped 10-12 times in a year ; a picul (133-k lb.) is sometimes taken from a largo tree, but the usual yield is about * picul. This kind is said to require no preparation for market, and to present the appearance of long strings irregularly welded together, the best quality being gummy-looking, of very firm texture, and reddish-brown colour, while the inferior quaties have a large admixture of bark, and are much drier, without the gum-like consistence of the better grades. In Assam, on the other hand, it is the " loaf" rubber obtained from the lower parts of the stem and roots that requires artificial preparation, while none is bestowed upon the produce of the smaller branches. The treatment consists in pouring the milk into boiling water, and stirring until it assumes sufficient consistenee to admit of being handled without becoming clammy or sticky. The plan adopted by a European house at Tezpore is to ruu the milk into woolen bins 6 ft. sq., partially filled with water, on which the rubber floats after a time. The latter, while still liquid, is removed and boiled over a slow fire in iron pans 4-6 ft. diam., and 2-2* ft. deep, 2 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 rapid destruetion by the natives of the wild rubber trees in Assam has called forth efforts to establish their cultivation in regular plantations. That at Chardwar has an area of 80 sq. miles, some 700 acres being under cultivation already. In 1678, it was stated that the planting had scarcely emerged float the experimental stage, for though no doubt remained that the tree would grow luxuriantly in the locality chosen, there was much variation in the degree of success gained by the soveral methods of planting. The plants put out in cane baskets in the forks of trees, though alive and healthy, remained nearly stationary ; and many of those simply planted in the ground also (lid badly, thus condemning these two plans. All those planted. on low split stumps, in earthenware cylinders on low stutnps uf trees, on piles of wood put crossways and mixed with earth, and on small mounds of earth 2-3 ft. high, did remarkably well, drainage about the roots b,ing ensured by these modes. It has been proved that the best cuttings do not transplant so well as :codlings, and that raising plants frum seed will be the method of propagation to be chiefly depend( d on.
Assaua rubber has a peculiar mottl( d appearance, and varies in colour from cream or flesh tints to blight pink or reddish ; it is very glossy, and sometimes covered with a groyish-whito film, which may arise from oxidation or from some foreign application. lts form is either that of iiregular lumps (" slab" or "loaf") produced as already described, or " balls " of the unprepared stringy substance obtained from the smaller branches. The impurities (bark, sand, clay) often read, 35 per cont., especially in the " balls." It arrives iu baskets made of split rattail, covered with gunuy-sucking, and weighing about 3 cwt. each.
Java rubber is also obtained from Ficus elastica, according to De Vrij. It is prepared by allow ing tho milk to concrete in the incisions made in the tree. It closely resembles Assam rubber, but has a deeper tint, with occasional reddish streaks.
Penang rubber is presumably identical in origin, no evidence being forthcoming in support of Wallich's statement that it is afforded by Cynanchum ovalifollum.
Rangoon rubber is also attributed to a Ficus, probably F. hispida.
These three kinds may be classed with Assam rubber for all technical purposes.
Attention has recently been called by G. NV. Strettell to a troublesome climbing " weed," Urceola [Chavannesia] esculenta, very common in the Burmese forests, as a. valuable source of rubber. It is urged that its cultivation could be made highly profitable. Assuming the plants tu be placed 30 ft. apart, 400 acres would contain 19,200 of them, which are estimated to yield 1 ri:ss (3 lb. 2 oz.) each per annum, worth 201. per 100 viss, or 38401. It is supposed that the eost of starting the pla.ntation would be trifling, uot exceeding 8s. per acre per annum on the first 7 years, making a total for that period of 1120/. The further cost of tapping, pressing, and preparing the juice is placed at 12* per cent. of the profits, leaving a nett asset of over 30001. per annum. The milk is said to coagulate more readily than that of Ficus spp. The incision adopted by Strettell is arrow like, aud made on the sides of the stem. The rows of cuts are 3 ft. apart, and art anged to be in vertical lines. Funnels formed of the leaves of Butea frondosa are selected for catching the exudation. The best season for tapping is a.bout the end of April ; between October and March, circulation is slow and the milk is scarce, but during the rains, the milk is more watery and abundant.
BORNE0.—The sources of Bornean rubber are not very accurately known. One authority names as the chief plant Urceola elastica, a climber with a trunk as thick as a man's body, and a soft thick bark, capable of being tapped at 3 years, and soon shooting up after having been cut down. Of this, Burbidge specifies 3 varieties, known respectively as petabo, yielding the best rubber, nicativati, the most prolific, and serapit, giving the lowest quality. On the other hand, the pctubo plant bas been identified at Kew as a Leuconotis sp. Again, Burbidge himself more recently writes that the Bornean rubber or gutta-susu is the mixed saps of 3 species of Viiillughbeia, with the milks of 2 or 3 other plants surreptitiously introduced to increase the quantity; and he gives the Malay names of the 3 species aa manungan, manungan puti, and manungan manga. Their stems have a length of 50-100 ft., and a diameter rarely exceeding 6 in. He adds that they are being slowly but surely exterminated by the collectors in Borneo, as throughout the other Malay islands, and on the Peninsula, where they likewise abound; on the other hand, they grow rapidly, and readily lend themselves to both vegetative and seminal methods of propagation, and hence are especially deserving of the attention of the Government of India, where they may reasonably be expected to thrive. The stems of these creepers are cut down to facilitate the collection of the creamy sap, being divided into sections measuring a few inches to 2-3 ft. long ; the escaping milk flowa into jars or buckets, the exudation being sometimes hastened by applying heat to one end. When sufficient sap has been thus collected, it is coagulated into rough balls by the addition of salt water or nipa salt (the latter obtained by burning the foliage of the nipa or susa [Nipa fruticans]). It reaohes Liverpool in porous or spongy balls and shapeless lumps, internally white or pinkish, and saturated with salt water in such quantity as to cause a loss of 20-50 per cent. in weight on drying.