THE BISKRA REGION. 6 1 



be distinguished as follows: The alluvial desert (reg), which lies on every 

 side of the oasis save the north; low hills adjoining the oasis on the north; 

 Ed Delouatt hills, southwest; the oueds and their flood-plains; the Dj. Bou 

 Rhezal ; the hamada ( ?) lying both to the north and to the south of the latter. 



VEGETATION OF THE BISKRA REGION. 



A glance over the list of plants which grow naturally in the vicinity of 

 Biskra* shows that many are the same as occur farther south, with many 

 unlike these, having affinities outside of the desert proper; also, the number 

 of plants as well as species is greater at Biskra than farther south. This 

 would be expected from the greater rainfall and more diverse topography. 



The flora of the Biskra oasis, according to the authors referred to above, 

 consists of 175 or more species. Of cultivated plants there are 25 or more 

 species, the most conspicuous being the date. The other species are mostly 

 the same as have already been noted at other Algerian oases, except that 

 both the peach and the apricot are wanting at Biskra, although cultivated 

 at Laghouat, Ghardaia, etc. On the outskirts of the town the fairly ex- 

 tensive flood-plain is given over mainly to the cultivation of grain, barley 

 predominating. 



The hills and mountains, and the bajada at their base, as well as certain 

 oueds with water relations, exposure, and soils different from those of the 

 oasis, have also a very different flora, which, for the most part, is desertic 

 in character. For purposes of comparison, some of the leading character- 

 istics of the plants growing in a half-dozen localities will be given. 



As stated above, to the southwest of Biskra there runs a range of hills, 

 Ed Delouatt, to the south and the north of which may be found interest- 

 ing plants and plant conditions. On the south side the slope (bajada) 

 descends gradually to the great reg, and near the base of the range, in the 

 vicinity of the place where tradition says a Roman town formerly existed, 

 there is a wide, sandy plain, reaching from the Oued Melah, which pierces 

 Ed Delouatt hills, nearly or quite to the western extension of the oasis. 

 There are no large dunes here, but sand billows about a meter in height 

 and sand hillocks diminutive in size. Between these the plain is fairly 

 level. Over this whole tract there seemed to be only one species {Euphorbia 

 guyoniana), but this was fairly abundant. (Fig. 65.) As at Ghardaia and 

 elsewhere, this species grows in small colonies because of its suckering habit, 

 and acts to a small degree as a sand-binder, each group being situated on a 

 sandy hillock. It will be remembered that this species at Ghardaia, as well 

 as at a certain bordj east of that place, had roots which were somewhat fleshy 

 as well as roots which were fibrous, on one and the same plant. I was inter- 

 ested to learn whether similar conditions should obtain at Biskra, since it 

 had been learned, in the case of two species of Opuntia in the Tucson region, 



* Liste des plantes observes aux environs de Biskra et dans l'Aures, Trabut et al., 

 Alger, 1892. 



