36 COMMERCIAL BOTANY. 



piece of ordinary pure vulcanised rubber. In combination 

 with gutta-percha it is said to reduce the tendency to become 

 brittle. Washers made with thirty per cent, of this gum 

 and vulcanised stand well, and retain their elasticity. The 

 gum comes to this country in small balls or ovoid masses 

 from one to four ounces in weight each ; in fracture it has 

 the appearance of broken balls of putty, friable when cold, 

 but easily kneaded or pulled out in hot water. It is very 

 clean, and has scarcely any admixture of bark or other 

 impurities. The bulk of the gum is said to come from the 

 Cameroons district. Nothing definitely is known of its 

 botanical origin, except that it has been referred by some to 

 a species of Juj)horbia, and by others to a species of 

 Tragia. 



A. concrete milky juice, identical with this gum, was im- 

 ported into Liverpool in 1874 from St. Paul de Loanda, and 

 was then referred to the genus Euphorbia. Another sample 

 of a similar character was received at the Kew Museum in 

 1883 from Mossamedes, and upon being tried by a well- 

 known firm of linoleum manufacturers, was reported to be 

 likely to prove of some value in their trade. The develop- 

 ment of this gum, as well as its botanical origin, is still in 

 the future. 



