FORESTRY 207 



cushions. The seeds contain 28 per cent of oil, and cattle-cake 

 can be made from the residue. The best floss, known as kapok, is 

 yielded by Ceiba pentandra, which grows wild in Africa, especially 

 near the West Coast. This product is receiving attention in Central 

 Nyasaland and the Tanga Province of Tanganyika, and trials have 

 been carried out in Kenya. 



Gum is a viscous substance which exudes from cracks or wounds 

 on the bark of many trees. Gum arable, the most valuable kind, is 

 completely soluble in water and is used as mucilage. It is the sub- 

 ject of a book by Blunt (1926). A considerable part of the world's 

 supply is obtained from the Sudan, where it is the most important 

 article of trade after cotton, and exports have had an annual value 

 in recent years of about ^^750,000. It is obtained from a number of 

 trees of which Acacia Senegal {verek), the most important, grows 

 abundantly in the dry Kordofan Province of the Sudan and ex- 

 tends westward to parts of Northern Nigeria. As a result of the 

 organization of the gum arable trade in Nigeria by the forestry 

 department, the export rose from 285,548 lb. in 1930 to 1,431,915 

 lb. in 1933. Gum-bearing trees are common in other dry parts of 

 Africa, and there is promise of a considerable industry in Tangan- 

 yika where the gum arable has been the subject of an inquiry and 

 report by D. W. Malcolm (1936). There appears to be room for 

 co-operation in marketing between the Sudan, Tanganyika, and 

 Nigeria. 



Resins are distinguished from gums by being insoluble in water, 

 but soluble in either alcohol or oil of turpentine. The kinds used 

 for making varnish are collected in the form of copals exuded from 

 trees. There is a considerable export of copals from West Africa, 

 where they are obtained from Copaifera, Trachylobium, and Daniellia 

 spp. The best quality comes from the Belgian Congo, medium 

 quality from the Gold Coast and Sierra Leone, and the poorest 

 from Nigeria. Mertens (1933) has given a full account of recent 

 researches on the constitution of copal from the Belgian Congo, 

 with special reference to its uses. In East Africa the chief copal 

 tree is Trachylobium hornemannianum. Copal of fossil origin, known 

 as 'Zanzibar anime', is found near the East Coast, chiefly in 

 Tanganyika, but exports are steadily decreasing. 



Most commercial oil-seeds are now cultivated as field crops. 



