Little is at present known of the large rubber tree of Tonkin (Bleckrodea tonkinensis), the latex of which is stated to furnish excellent rubber.
The rows of cells from which the laticiferous vessels are formed can be distinguished in many cases in the young embryo while still in the dry seed (Scott), but the latex vessels in process of formation are more easily seen when germination has begun.
The latex coagulates readily, especially if churned or if diluted with water, when a purer rubber is obtained.
As a secondary function we may recognize, in certain cases, the power of closing wounds, which results from the rapid coagulation of exuded latex in contact with the air.
To obtain the rubber, the latex is usually treated in the following manner.
The globules in the latex are liquid, and the phenomenon of coagulation would seem to consist in the passage of this liquid into solid caoutchouc through the kind of change known as polymerization or condensation, in which a liquid passes into solid without alteration of composition or by condensation with the elimination of the elements of water.
Africa the Hevea which has been planted promises well, especially in the Gold Coast, where good yields of latex are stated to have been obtained.
The latex is not to be confused with the sap of trees, on the circulation of which their nutrition depends.
The latex is collected in cups placed at the apex of each V.
The latex of this tree flows less freely than that of Hevea brasiliensis, and the collection of large quantities of the latex is attended with considerable difficulty.