Sir Daniel Morris, in his Cantor Lectures, states that "In 1873 the Government of Bengal decided to start regular plantations of Ficus elastica in Assam. The order, issued in 1873, was repeated in 1876, and has been acted upon with slight interruption until the present time" In 1884 nearly 900 acres had been planted in the Charduar district, and in the same year directions were issued that the plantations should be increased by 200 acres annually. It is said to be well known that although the trees grow vigorously in situations remote from the hills, the yields of rubber are then almost negligible. It appears, however, that even in its native hills the yields of the Assam india-rubber tree are very small from a planter's point of view. Thus in 1896 the Inspector general of Forests, H. C. Hill, was glad to estimate a yield of a maund (about 80 lbs.) per acre at an age of 50 years.
Ficus elastica has been widely planted in Java in more recent years, but here again no better yields appear to be obtained. Berkhout estimated 17 lbs. of dry rubber per acre in the eighth year from planting, 26 lbs. in the tenth year, and 70 lbs. an acre in the twentieth year. Such yields render the trees almost useless for plantation purposes, and in many parts of the Dutch East Indies where they have been planted they are already being cut down to make way for Hevea.
The above comprise all the species which have been used at all extensively in plantations proper. The method of replanting in the forests in which the wild rubber plants have been partly destroyed is being adopted in several countries, notably in Brazil and in the Mabira forest of Central Africa. Rubber vines were extensively planted some years ago in the Congo by the orders of the Belgian Government. This method was recently given up in favour of Funtumia plantations, and still more recently there has been a tendency to abandon Funtumia in favour of Hevea. On the whole, it seems probable that in the future the world's supply of rubber will depend more and more upon the plantations of Hevea, including those established or about to be established in Brazil.