834 Journal of the Department of Agriculture. 



A SOUTH AFRICAN GUM 



(iCOMBRETUM ERYTHROFHYLLUM, Burch.). 



By K. A. Lansdell, Division of Botany, Pretoria. 



In recent years much difficulty lias been experienced in obtaining 

 supplies of "Gum Tragacantli," whicli to-day is selling- in South 

 Africa at 22s. per lb. Gum Tragacanth is used extensively in 

 tanneries, and the prohibitive price and lack of material suggested 

 that local sources of a substitute should be investigated. 



Mr. Chas. Maggs, of Pretoria, approached the Division in 

 October, 1919, for assistance in this matter, and the subsequent 

 investigations of Dr. I. B. Pole Evans resulted in an excellent native 

 substitute for Gum Tragacanth being brought to light in the shape 

 of a half-insoluble gum produced by a local tree — Combretvm 

 erythrophylUim. A sample, 2 lb. in weight, was submitted to Mr. 

 Maggs for trial, and he reported as follows: " I have carefully tested 

 the sample and am very pleased with the result. The gum is soluble 

 with difficulty, and when applied as a coating is elastic, quite unlike 

 Gum Arabic, whicli powders and crumbles when dry. I consider that 

 this gum is a good substitute for Gum Tragacanth, as it is tasteless, 

 and so far as I am aware does not possess any injurious properties. I 

 shall be very pleased if you could inform me where I may obtain 

 trees or seeds of the tree for planting." 



Mr. Maggs further states that the local gum has been used by 

 him as an elastic non-cracking varnish for finishing uppers and 

 other leather; previously he had used the imported Gum Tragacanth 

 exclusively, but finds the local product every bit as effective, and, 

 especially now that Gum Tragacanth is such a prohibitive price, 

 infinitely cheaper. The gum is applied in a solution of water mixed 

 with various dyes : the strength of the solution varies with the nature 

 of the surface under treatment. As there is a large demand for gums 

 of this nature a sample of the local gum was submitted to the Imperial 

 Institute for valuation on the London market, and the following 

 report has been received : — 



" Descriptioii of Sample. — The sample weighed 2 lb., and con- 

 sisted of small irregularly shaped tears, many of which were elongated 

 and stalactitic in form. The tears were pale yellow to pale yellowish- 

 brown, and had an average weight of about 2 grammes. The sample 

 was in fairly clean condition, and contained only a small amount of 

 adherent bark. 



" Results of Examination. — The gum was analysed, with the fol- 

 lowing results: — 



Per cent. 



Moisture 11.2 



Ash 2.6 



Acid val ue 7.1 



