22 Journal OF the Department of Agriculture. — July, 1922. 



Combretum Guirii — As a result of the article on (^oin})ret\im f?\iTn 

 which appeared in the Jovrnal (December, 1920, p. 834) a number of 

 inquiries have been marie as to the possibility of collectinfi' the gum 

 in quantity. The collection of the gum from trees in their natural 

 habitat cannot be expected to yield sufficient quantity for its exploita- 

 tion on a commercial scale, and more satisfactory results will be 

 obtained when trees can be planted in large numbers in suitable locali- 

 ties. Seeds of Covibretum erythropJiyllvm have been planted experi- 

 mentally near Pretoria, and the seedlings are doing very well. The 

 young- trees are about 3 feet high although they are only twelve months 

 old. It will be a matter for experiment to determine at what age the 

 trees will yield the maximum of gum. 



Cassava is a crop Avhich should do well in the sub-tropical 

 parts of the Union, and the powdered starch extracted from its large 

 tubers commands a ready market in Europe, and would probably find 

 a market in South Africa. Not only are meal, flour, tapioca, and other 

 starchy foods prepared from Cassava roots, but they are also a valu- 

 able source of alcohol, glucose, and dextrins, and the residues are 

 largely used as feeding stuff for live stock. 



The Prisons Department has been interested in the cultivation of 

 this crop, and an experiment recently carried out on a small scale at 

 the Reformatory at Eshowe, in Zululand, proved that the plants could 

 be successfully reared in that district. They have also been grown 

 successfully in Swaziland and in the Northern Transvaal. 



Cassava belongs to the natural order Euphorbiaceae and the genus 

 Manihot, and is related to the Ceara rubber tree. It is a much 

 branched shrub that, \inder cultivation, reaches a height of 6-10 feet. 

 The leaves are large, roundish, and deeply lobed ; the flowers are borne 

 in spreading clusters at the ends of the branches. The fruits contain 

 the seeds about the size and shape of castor oil seed, to which it is 

 related. The root tubers are large, and vary in size according to the 

 age of the plant, but usually when ready for harvesting they are from 

 lA-4 feet long, and are borne in clusters at the base of the stem. 



There are two kinds of Cassava groAvn, the sweet and the bitter. 

 Authorities differ as to the exact relationship of one with the other ; 

 by some they are considered distinct species, the bitter being known 

 as Manihot utilissima and the sweet as Manihot palwata, while other 

 botanists consider the latter but a cultural variety of the former. The 

 sweet Cassnva is on the whole the better variety to cultivate. The 

 tubers yield a greater amount of starch, and contain less of the 

 poisonous hydrocyanic acid than the latter variet3^ The poisonous 

 acid commonly known as prussic acdd is present only in the outer 

 layers of the sweet Cassava, and is removed by peeling the roots, 

 while in the bitter variety it is more evenly distributed through the 

 roots, and can only be neutralized by heating. 



As Cassava roots decay very (juickly after removal from the 

 ground they must, therefore, be dried at once, either in the sun or 

 with artificial heat. The usual process is to wash and peel the roots, 

 and halve them longitudinally, and cut out the more fibrous central 

 portions ; the remainder is cut into strips, and laid in the sun till 

 thoroughly dried, when they will keep for months. The drying 

 must be rapid in order to preserve the colour of the material. 



