There are several commercial varieties of the rubber obtained from Castilloa spp. Cartagena rubber arrives from New Granada (Colombia) in black sheets in. thick, having a somewhat rough or "chewed" appearance, and more or less " tarry " or sticky. It also occurs in strips or scraps pressed together in bags. It loses about 35 per cent. of its weight on drying. Guayaquil rubber comes from Ecuador in large flakes and lumps, the better quality being whitish coloured, while the inferior is porous and saturated with a fcetid black liquid. Its loss by washing sometimes reaches 40 per cent. This and the preceding kind go chiefly to America. Nicaragua rubber, which mostly reaches the same market, loses only 15 per cent. by drying. The best of the Central American rubbers is that known as " W. Indian," not from its being produced in the W. Indies, but coming in steamers sailing thence. It consists of blocks which, in the first quality, are formed of thin separ able sheets, and, in the second, of conglomerated " scraps" with fragments of bark. Honduras rubber is of good quality, and free from " tarry " matter. Guatemala rubber is one of the lowest and least regular kinds; the best specimens are whitish, while the "lower" are black and " tarry." This rubber arrives in sheets compacted together, whence a thick resinous fluid exudes on pressure ; this fluid, on evaporation, leaves a hard resinous substance unaffected by steam.
The wasteful and destructive local methods of collecting the milk of this genus are causing its rapid extermination in the countries where it is indigenous. Attention has been directed to its naturalization in our tropical possessions, but though the plant is of rapid growth, it will scarcely thrive in regions that are not equally suited to the Hevea spp., and its rubber is much inferior. It has been introduced successfully in Ceylon, Singapore, and Perak. With regard to its culture, it may be observed that trees in good situations will produce seeds early, but these need to be planted without delay, as drying destroys their vitality. Flowering occurs in January, and the fruits ripen in April (in Brazil). Stout branches, cut into pieces, each possessing a bud, and covered lightly with soil, will generally be found to grow. Strong cuttings 1 ft. long and furnished with buds, planted in the usual way, sooner develop strong plants, But the propagation of this tree is not reckoned so easy as that of the Ceara rubber (lIllinihot Glaziovii). In setting out young plants, the petiole or lesf stalk of the lowest or oldest leaf should be buried in the soil ; this simple devioe ensures the immediate and vigorous growth of the plant, and a symmetrical stem. When the planting, leaves much bare stein above gmund, the growth is slow, the plant long remains "leggy," nnd neve: forms a goo.I tree. The plant has the curious habit of dropping its young bmnches, which disartieulate by a regular joint, and leave a elean sear on the surface of the stem. It is believed that after 6 years, the trees might be judiciously bled every 3 years.
PARA.—Pant rubber, which is second to none in importance, is afforded by several species of H.rea [Siphonial the most important being H. bra.siliel131,, guianensis, and H. Sprucean 7. These trees inhabit the dense, st2aming forests on the Amazon and its tributaries, other species replacin4 them in some of the adjacent countries, e. g. H. paucifolia in British Guiana, where Prestoe believes it will be found in c,onsiderable abundance. Brazil is being gradually but surely denuded of its rubber-trees, collectors being now driven to the Tocantins, lifadeira, Purus, and Negro rivers in search of supplies. A recent traveller sta tes that, in Bolivia, extensive rubber forests are at present profitably worked on the Lower Beni, and it is natural t,o suppose that they exist to an equal extent 011 the Mayutata and Aquiry ; those on the Mamore and Lower Iteuez, though giving rubber of a superior quality, do so in less quantity.
In the Para district of the Lower Amazon, the temperature varies between 74' and 95° F., the mean of the year being 81° F.; the supply of moisture is also very regular. On the Upper Amazon, the atmosphere is densely vapour-laden. The soil frequented by these trees is extremely rich mould. The trees will grow on the terra firme when planted, but their seeds naturally lodge in lowland swamps. All the species flourish best on rich alluvial clay slopes by the side of running water, where there is a certain amount of drainage; those growing on land which is periodieally inundated (even to a depth of 5 ft.) are more prolific than those on very low or on elevated ground.
The methods adopted for tapping the trees are described at length by Cross. The collectors
begin work immediately at daybreak, or as soon as they can see to move about among the trees. Rain often falls about 2-3 o'clock in the afternoon, so the tapping must be done early, as in the event of a shower, the milk would be spattered about and lost. The collector, first of all, at the beginning of the dry season, goes round and lays down at the base of each tree a certain number (3-12) of sinall cups of burnt clay. On proeseding to his work, the collector takes with him a small axe for tnpping, and a wielter basket containing a good sized ball of well-wrought elay. usually has likewise a bag for the waste droppings of rubber, and for what may adhere to the bottoms of the cups, these promiscuous gatherings being termed sernarnby, and forming the " negro head " of the English market. The cups are sometimes round, but more frequently flat or slightly eoneave on ono side, so as to stick easily, when, with a small portion of clay, they are pressed against the trunk of the tree. The contents of 15 cups make about 1 pint. Arriving at a tree, the collector takes the axe in his right hand, and, striking in an upward direction as high as he can reaeh, makes a deep upward sloping cut across the trunk, which always goes threugh the bark, and penetrates 1 in. or more into the wood. The eut is 1 in. in breadth. Frequently a email portion of bark breaks off from the upper side, and oecasionallY a thin splinter of wood is also raised. Quickly stooping down, he balms a eup, and pasting a small quantity of elay on the flat side, presses it to the trunk close beneath the eut. By this time, the inilk, which is of dazzling whiteness, is beginning to exude ; if requisite, he smooths the clay so that the milk may trickle -directly into the cup. At a distance of 4-5 in., but at the same height, another cup is luted on ; and so the prooess is continued, until a row of cups eneircle the tree at a height of about 6 ft. from the ground. Tree'after tree is treated in like manner, until the tapping required for the day is fiuished. This work should be concluded by 9-10 o'clock in the morning, because the milk continues to exude slowly from the euts for three hours, or perhaps longer. The quantity of milk that flows from each eut varies; but if the tree is large and has not been much tapped, the majority of the cups will be more than half-full, and occasionally a few may be filled to the brim. But if the tree is much gnarled from tapping, whether it grows in the rich sludge of the gapo (inundated land) or on dry land, many of the cups will be found to contsin only about a tablespoonful of milk, and sometimes hardly that. On the following morning, the operation is performed in the same way, only that the cuts or gashes beneath which the eups are placed are made 6-8 in. lower down the trunks than those of the previous day. Thus eaeh day briogs the eups gradually lower, until the ground is reaehed. The colleetor then begins as high as he can reaeh, and descends as before, taking care, however, to make his cuts in separate plaees from those previously made. If the yield of milk from a tree is great, two rows of eups are put on at once, the one as high as ean be reached, and the other at the surface of the ground ; in the eourse of working, the upper row descending daily 6-8 in., while the lower one ascends the same distance, the rows in a few days come together. When the produce of milk diminishes in long-wrought trees, two or three cups are put on various parts of the trunk, where the bark is thickest. Although many of the trees of this elass are large, the quantity of milk obtained is surprisingly little. This state of things is not the result of over tapping, as sotne have stated. Indeed, Croi..s believes it impossible to overtap a tree, if, in the operation, the wood is not left bare or injured. But at every stroke, the eolleetor's axe enters the wood, and the energies of the tree are required in forming new layers to cover those numerous wounds. It has been supposed that the quality of the milk is better in the dry season than during the rains. In the rainy season, the milk probably contains a greater proportion of water ; but, on the other hand, a larger quantity of milk then flows from the tree. No doubt the dry season is the most suitable for rubber collecting, although, wherever a plantation is provided with a preparing-house, convenient tapping may certainly be always carried on when the weather is fine. It is a common report that the trees yield the greatest quantity of milk at full moon. Even if this were found to be true, it would probably make little difference, as tapping must be carried on when circumstances are most favourable.