58 BOTANICAL FEATURES OF THE ALGERIAN SAHARA. 



TOUGGOURT TO BISKRA— PHYSICAL FEATURES AND VEGETATION. 



From Ouargla to Touggourt we have found that the country gradually 

 descends, the former place being 124 meters and the latter 77 meters above 

 the level of the sea. From Touggourt, also, for a distance of about 120 

 kilometers, the descent along the route continues until at the Chott 

 Merouan a level of 6 meters is attained. The lowest places in every case 

 are of course the chotts and the connecting oueds. The most important 

 chott of this series is Melrirh, 11 meters or more below sea-level. This 

 drainage system is the northern culmination of the vast one of which the 

 Oued Igharghar is the most important part. In an earlier age water came 

 north in the oued from the highlands of central Sahara and poured into 

 the Chott Melrirh, having passed successively through the lesser chotts 

 farther south. At that time, also, the Chott Melrirh probably was con- 

 nected with the Gulf of Gabes. 



From Touggourt to Chott Merouan, the lowest portion of the route to 

 Biskra, the topography is that of a region of chotts; that is, there are salt 

 spots surrounded on every side by higher ground, which in many cases is 

 of sand. From Chott Merouan the route passes over a higher desert of a 

 different character, which in part bears a remote resemblance to the Gantara 

 and in part to the Ouargla plain. It is a vast plain, with little topographical 

 diversity, which rises to meet the Atlas Mountains to the west and north. 

 In the eastern portion it is somewhat rolling, stones are strewn plentifully 

 on its surface (hamada), and there has been considerable erosion, so that 

 gullies are formed. In the portion nearer Biskra the surface is more level, 

 the soil is fine (reg), and there has been comparatively little erosion. 



The soil of the chott region is largely of sand; on the hamada there is 

 much clay, while on the reg it is fine and easily blown by the wind, and this 

 in spite of the fact that the most vegetation seen in the Sahara was in this 

 region. A slight breeze picks up the dust and carries it long distances in 

 dark clouds. It fills the throat, nose, and eyes of the traveler and makes 

 crossing the reg exceedingly disagreeable. 



The plant life as seen along the portion of the route through the chott 

 region consists almost wholly of halophytes, as would be expected, in addi- 

 tion to which, where for short distances the hamada or dunes were crossed, 

 there were forms characteristic of such areas. The Tamarix is especially 

 common in the region and Limoniastrum guyonianum is also often met. 



The date gardens of the Oued Rirh are justly famous. One passes num- 

 berless plantations where the date is cultivated, and in the neighborhood 

 of each group of gardens one sees squalid Arab villages. Over 19,000 tons 

 of dates are said to be carried each year by camel from the Oued Rirh to 

 Biskra, whence they go to the markets of the world. One day we passed 

 700 camels laden with dates going to Biskra. 



As soon as the chott region is left and the higher ground is reached a dif- 

 ferent as well as a richer flora is encountered. Here diversity of topography 

 favors diversity of plant life. On the reg near Biskra vegetation is especially 



