40 TUNISIA 



and set 25 cm. (10 inches) deep. It is strengthened by posts 

 every 1.2 metres (4 feet) and smaller posts or stays every 

 5 to 8 metres (6 to 9 yards). The hedge is wired on each side 

 and the wires joined. The sand washed down on these hedges 

 is retained, and forms a series of horizontal paths or shallow 

 ditches, one above the other, to retain the water. The work 

 costs at a rate of 50 centimetres ($0.10) per running metre 

 (i yard). 



At El-Oudian still another method is used to protect the 

 springs. There the ditches are designed to carry off the sur- 

 plus water to a point where it will do no harm. The slope 

 is steeper than at Tozeur, but not so vertical as at El-Hamma. 



Besides mere protective works, the Forest Service has experi- 

 mented in the matter of plantations, but they have not as yet 

 been successful, except where they could be irrigated. The 

 only tree (small and crooked at best) which seems to come in 

 naturally on the edges of the desert is the tamerisk (africana). 

 The best shrub seems to be the retem and the best grass the 

 alfa. The tamerisk can be reproduced by shoots 30 cm. (11.8 

 inches) long and placed 28 cm. (11 inches) in the sand; but on 

 an area of several acres recently every shoot thus set had died. 



The following official statement of the problem is perhaps too 

 optimistic: 



" ... The Forest Service tries to cover the zones of 

 protection with tree species, but has met in this respect serious 

 difficulties. The annual rainfall is only a few centimetres, 

 sometimes almost nothing. The species to be grown must, 

 besides, withstand the burning sirocos which blow during the 

 summer. It is, therefore, necessary that the fibres be as 

 tough as leather and small, to lessen evaporation, a charac- 

 teristic of all desert plants. The land to be restocked can 

 not be irrigated and sprinkling is only possible on restricted 

 areas for fear of high costs." 



Strange to say, some of the railroad right-of-way area in 

 Tunisia has been sown to aleppo pine, an inflammable species; 

 but most of the planting has been with eucalyptus, which has 

 done remarkably well where there was sufficient water. On 

 dry ground the trees were spindling and of little value. 



