RUBBERS AND GUMS 199 



bark. In tapping young trees good results were obtained from 

 the use of long V-shaped cuts leading nearly to the base of 

 the tree. The flow of latex has been found to be most pro- 

 fuse from the base of the trunk and decidedly less vigorous 

 from the upper portion of the trunk. In Hawaii, the method 

 adopted on Ceara plantations in preparing rubber consists 

 merely in the use of the ordinary rubber mangier through 

 which a continuous stream of water runs during the cleaning 

 process. By this machine the latex is freed of dirt and much 

 of the resin, proteid, and other impurities under the great 

 pressure of the mangier and the dissolving influence of the 

 water. The thick crepe-like sheets into which it is finally 

 rolled are then dried in the vacuum drier. Ceara rubber con- 

 tains about 91.5 per cent, caoutchouc, 1.5 per cent, ash, 0.5 

 per cent, moisture, 3.5 per cent., resin, and 3 per cent, protein. 



Other species of Manihot are also being tested in various 

 rubber-growing districts, but commercial experience with these 

 species is too recent for reliable opinions The species which 

 have received most attention are M. dichotoma, M. piauhyen- 

 sis, and M. heptaphylla. 



The African rubber tree (Funtumia elastica) has been com- 

 monly referred to as the source of Lagos silk rubber. The 

 tree bears smooth oblong leaves 5 to 10 inches long and i to 4 

 inches wide. The trunk is erect and tapering, covered with a 

 mottled gray bark, and reaches a height of 100 feet at maturity. 

 In Central Africa, from Sierra Leone to the East African 

 Protectorate, the native methods of collecting Funtumia rubber 

 were to cut down trees and then slit the bark or coagulate 

 the latex in the bark by heat. The bark was then beaten into 

 fragments from which the rubber was gradually collected into 

 shreds or balls. Later the natives adopted the full herring- 

 bone system of tapping and carried the tapping wounds up 

 the trunk to a height of 50 feet with the help of ladders and 

 slings. Funtiunia latex is rather difficult to coagulate. It 

 coagulates spontaneously only after standing about 6 weeks. 



