326 PLANTS PRODUCING GUMS AND RESINS 



Ri. 

 1900-01 ... ... ... ... ... ... 699,883 



1902-03 ... ... ... ... ... ... 454.639 



1906-07 ... ... ... ... ... ... 609,263 



Acacia Senegal — This is the most interesting species; it is a small 

 tree, 5 to 7 metres high, with a leaning trunk and a very large number 

 of branches. The leaves are alternate with two or three spines which 

 are probably modified stipules. It grows in dry and sandy districts, 

 especially on the right bank of the Senegal, extending over vast sandy 

 tracts frequented by various Moorish tribes, Trarzas, Braknas, &c., 

 who gather the gum. 



The rainy season being over in October, operations are begun 

 towards December. Owing to the tissues being swollen with water due 

 to the humidity, the cellular membranes begin to gelatinize, and when 

 the burning east wind starts blowing the trees dry up, the bark cracks 

 and splits, and the gum flows through the cracks and solidifies. 



In January and February the product is most abundant, the trade 

 being then at its highest. It ceases in June. 



The gum generally appears as round, white, or light-coloured, trans- 

 lucent masses, with an opaline fracture ; the colour passes from yellow- 

 ish to red, and occurs in larger masses than the Turkish gum. 



The density of gum Senegal is i"436. It is very soluble in cold 

 water, and its ash contains oxide of iron, potassium chloride, silica, 

 alumina, magnesia, lime, and potash. 



Its composition is as follows : — 



Arabin 



Water 



.Saline matters and organic debris 



Distinction is made between two sorts of gum Senegal : — 



(i) The hard gum from the lower portion of the river, from Galam 

 or Cayor. 



(2) The friable gum from the top of the river. 



In all probability this latter is the product of Acacia albida; it 

 resembles coarse salt, whilst the former occurs as white tears ; the inter- 

 mediate colours are from yellow to red. 



The gum is collected by Moors and transported by caravans to 

 various stations of Medina, Nioro, &c., where exchanges are effected. 

 The Somali pack it in a sort of wicker basket covered with goatskin 

 and convey it to the Gulf of Aden, more especially to Berbera. 



Acacias yielding gum occur along the whole of the northern frontier 

 of the Soudan; Acacia Senegal is the predominant species, then follow 

 A. albida and A. Seyal. 



As in the cnse of the Indian gum arabic, the value of the gum of 

 the Acacia Senegal varies according to the districts whence it is taken. 

 Senegal and Kordofan are quoted highest; after that come Stiakin, 

 Sennaar, and Blue Nile. 



