GHARDAIA TO OUARGLA — VEGETATION. 53 



GHARDAIA TO OUARGLA— VEGETATION. 



The plants seen during the first day's march from Ghardaia were such 

 as have already been observed to be characteristic of the valley of the Oued 

 M'Zab or of the neighboring hamada. The vegetation of the hamada, 

 usually very sparse, was noticeably more abundant wherever the sand had 

 been drifted over it from the dunes of the valley, even if the thickness of 

 the sand was so slight as to be little more than a mulch. Here low grasses, 

 much eaten, were the prevailing forms. On the dunes in the valley of the 

 M'Zab, 20 kilometers from Ghardaia, the number of species and individuals 

 is relatively large, the most abundant species being drinn (Aristida -pun- 

 gens), although Deverra scoparia is also fairly numerous. Somewhat farther 

 on the route, and in a sandy flat, besides these two species, there is much 

 Ephedra alata. On the slopes leading from this flat and on the plain above, 

 there is an almost pure stand of Rhantherium adpressum. 



Crossing relatively small portions of the plain, in place of always follow- 

 ing the bends of the Oued M'Zab, about noon of the second day we reached 

 the bordj Zolfana, in the valley of the Oued amidst low and narrow dunes, 

 which are moving slowly across the flats. (Fig. 441.) No vegetation 

 appears on the dunes, but on the fixed sand between them, or on the 

 stationary dunes at the border of the flats, some plants are to be found. 

 Among these the most abundant, but really not numerous, are Euphorbia 

 guyoniana and retam (Retama retam), which was often seen later along the 

 line of march as well as in the vicinity of Biskra. Retam superficially 

 resembles Ephedra alata in having rudimentary leaves and green, reed-like 

 branches ; it is carefully avoided by animals, although Genista saharce, a very 

 similar plant, which grows in like situations between Ghardaia and Ouargla, 

 is said by Massart (loc. cit.) to be eaten greedily by them. (Fig. 43.) 



A short distance beyond the bordj the bottoms suddenly widened, the 

 dunes disappeared, and for the remainder of the day's march we passed 

 through the richest vegetation we had seen since reaching the M'Zab region. 

 (Figs. 45, 46, and 47.) Here the shrubs were of fair size and of sufficient 

 abundance to give character to the landscape. About the 63 kilometers 

 camp the leading species are Retama retam, Ephedra alata, and Haloxylon 

 schmidtianum. On the hamada adjoining the flat are several species, in- 

 cluding Aristida ciliata, Artemisia herba-alba, Farsetia cegyptiaca, Farsetia 

 linearis, Gymnocarpon fruticosum, Helianthemum eremophilum, Henophyton 

 deserti, Marrubium deserti, Salsola vermiculata, Teucrium polium, Thymelcea 

 microphylla, and Zollikoferia mucronata. On the hamada just adjoining the 

 place of our camp, however, there appeared to be Haloxylon schmidtianum, 

 to the exclusion of other species. 



After crossing the bottoms of the oued the trail climbed up to the hamada 

 and we did not see the M'Zab Valley afterward. The vegetation of the 

 hamada soon becomes very sparse and as far as the eye can reach the ap- 

 pearance is that of entire bareness. But, as was found to be the case near 



