226 REPORT OF rnEMicAr, r.AnoRATouY 



cstalilisli villages noar suitalik- tracts of Waily. Food stuffs ciiii lie liouglil or cxcluiiigctl 

 for gnni, lint often some diikhn is cultis'uteil liy Geneiiiit owners. 



" Tile i|iiiUitity of gum produceil on a given area varies very much (aieording to the 

 stock of trees). 

 Vifici of gum " On an average (Jeneina near Sliergeila, area ulniiil in acres, the owner stated that 



the first collection yielded ahout 100 Ihs. of gum, droi)iiing to Tf) lbs. and (!0 llis. at 

 the second and third picking. After that it averaged ahout 50 lbs. each for several 

 collections, and goes on diminishing to 10 lbs. at the close of the season. He estimated 

 the annual yield at I'i nr IT) Kantars (1,200 to l/)00 lbs.). 



" Near Agari, where the fJeneina were much better, the estimate for 'M) Geneiiuis for 

 the sea.-<on was 700 Kantars (70,000 lbs.), of which 470 Kantars had then (7th Aja-il) 

 bei'U collected. 



" For equal areas the out-turn at Agari, would be about double that at Shergeila, due 

 chiefly to the want of density in the stock of trees in the Shergeila Geneinas. 

 ■'■'»"' " T.\LH Gum.— Talh gum is collected chiefly from the JMue Nile forests; these were 



visited before the gum collecting season had commenced, consequently the work of 

 collecting was not seen. 



" According to the information obtained the 7'iilh trees are not barked or wounded 

 in any way by gum collectors, who take such pieces of gum as they find exuding from the 

 trees. It is impossible to form any estimate of the immense area over which the Talh 

 Acacia grows. There arc twcj varieties of trees, one witli a led powder which so covers 

 tlie bark of the tree as to uudvc it appear entirely red, is called Jii't/ Tulli, the other is 

 similarly coateil with a white powder, has a staring white appearance, and is generally 

 called White Titlh, but bears also tlie name •'^offur, from the fact that the base of its 

 stipular spines are usually enlarged by llie [miicture of smiie insect wln'ili dijiiisits its 

 eggs there, the larva emerging makes a small hole through the globular enlargcna-ut 

 and the wind blowing on this produces a whistling .sound. 



" Both varieties produce gums, which appear to be indistinguishable, but the llid TnUi 

 being very nnieb nuire almndaut than the White, it is fnjiii that variety that most of the 

 TiiUi gum is obtained. 



" The localities where this gum is collected in quantity ai-e in the Karkoj JIamuria, 

 and the South part of the Wad-lOl-Abbas Mamuria. A small ipiantity is also collected 

 in th(' Roseires District. A eonqiaratively small (|Uaiitity is extraete(l fnun tin- for<'sts 

 West of Kaka on the Whit.' Nile." 



Origin of glim OiiioiN OF GuM. — According to the recent researches of Greig Smith* the production 



of gum is due to a specific microbe, which he has named lUirt. tiniriir. The gum has been 

 shown to be formed from the wandering sugars, levulose and maltose, in the sap. Another 

 organism, />. iiii-/<ini/'iiiiiiii, was also isolateil. This was foiuid to produce the form of gum 

 which swells up in water, but does not dissolve. Further, it was found that the host plant 

 was able to convert /i. acuritr into /{. iiiffnriiliiiinin. thus proving that the latter organism is 

 sinqily a variety of the former. It appears evident from these rescandics that /i. iinirin is 

 the prime cause of the formation of gum in all varieties of acacias, the character of the gum 

 formeil ilepending upon the nature of the sap of the host. This would explain the 

 uniformity of the gum from certain species of trees. 



• IVuceudings of the Linncan Society of New South W.-ilof, 190'.'-.1-4 ; .1. Soc. Cheni. In<l., Feh. .'ukI Oit., 19o|. 



