A concrete juice produced by various trees found in the Malayan archipelago, especially by the , syn. . It becomes soft, and unpressible at the tamperature of boiling water, and, on cooling, retains its new shape. It dissolves in oils and ethers, but not in water. In many of its properties it resembles caoutchouc, and it is extensively used for many economical purposes. The of Guiana also yields this material.