36 BOTANICAL FEATURES OF THE ALGERIAN SAHARA. 



occurs very sparingly by the roadside. The habits and the habitats of 



certain of the above-mentioned species will be described in greater detail 



later in this paper. 



GHARDAIA. 



The Ghardaia region can be characterized as a vast plain, broken to the 

 north by low, irregularly disposed mountains, and stretching for a great 

 distance to the south and southeast with a fairly monotonous surface, diver- 

 sified only by oueds, chotts, or occasional dunes, which may be the size of 

 small mountains. Thus on the one hand one finds the fairly diversified 

 and stony Chebka and on the other the hamada, which has been aptly 

 described by Brunhes* as "le d6sert par excellence, la vrai desert . . . les 

 grandes plaques pierreuses ind^finies des hamadas!" 



The leading oued of this region is the M'Zab, which extends for about 

 270 kilometers in a direction south of east across the southern part of the 

 Chebka. It takes its origin about 80 kilometers west of Ghardaia and ex- 

 tends to the vicinity of Ouargla, where it debouches on the Ouargla plain. 

 At Ghardaia the oued lies in a valley, with abrupt sides, which is sunk 

 about 60 meters below the surrounding plain and which at this place is 

 about 3 kilometers in width. (See fig. 16.) There are four main tributaries 

 of this oued, all of which join it from the north or the Chebka side. The 

 valley of the M'Zab becomes more and more shallow as one proceeds east- 

 ward and at last lies but little below the general level of the country. Like 

 the other deeper valleys of the Chebka, the M'Zab Valley represents the work 

 of erosion by water at an earlier geological epoch, when the great terraces were 

 formed. The filling of the eroded valleys has perhaps taken place during the 

 long arid period since that time and has probably proceeded very slowly. 



It appears to be uncertain how long the M'Zab has been inhabited by 

 man, or, more accurately, by the race now dwelling there ;t but it has 

 probably been not less than nine centuries. J 



* Les Oasis du Souf et du M'Zab, La Geographie, 1902. 



t Foureau, d'AIger au Congo par le Tchad, 1902, mentions having met with indica- 

 tions of early settlement of the Sahara by people now forgotten, and whose tombs, 

 inscriptions, and other remains, were well known by his Touareg servants, although 

 not at all understood by them. So far as I have learned, however, it is not supposed 

 that the region of the M'Zab was inhabited before the coming of the Beni M'Zabs. 



t There are seven cities of the Beni M'Zab, of which five lie in the M'Zab Valley, 

 close to one another. These are El Ateuf, Ben Noura, Melika, Beni Isguen, and Ghar- 

 daia. In the pre- French times these cities were bound together in a confederacy with 

 Ghardaia as the capital. The M'Zabites are at present, and probably always have been, 

 a peaceful trading folk. They are heterodox Moslems. In an early time they aroused 

 the antagonism of their more warlike as well as more orthodox Arab neighbors of the 

 Tell, who drove them away from the coast region, and again from Ouargla and other 

 places settled by them, until safety was at last secured in the eleventh century in the 

 " inhospitable Chebka." Palm gardens were established which for centuries have been 

 irrigated laboriously by very primitive methods, and the inhabitants have accumulated 

 wealth in flocks and by barter. The relatively large population (there were 92,761 

 inhabitants in 1908), the really great number of domestic animals, and the great length 

 of time which the region has been occupied, are all factors of importance in bringing 

 about a modification in whatever way of the primitive flora. 



