GHARDAIA. 43 



always an older portion and always a newer portion, and the part once 

 used is never afterwards made use of again. From this fact, as well as 

 others which need not be entered into, the more ancient portion of the 

 cemeteries, after a lapse of several centuries, or even several decades, with- 

 out disturbance, must be in essentially the same condition as regards the 

 soil and water relations, which would be most affected by the fact of inter- 

 ment, that they were in in pre-M'Zabite times. 



Several cemeteries near Ghardaia and the other M'Zab towns vary 

 greatly in their position as well as exposure; some are on the valley floor 

 below the town of Ghardaia, and others are in side canons; one is on the 

 south wall of the valley with a northern exposure, and another is on the 

 opposite wall and hence with a southern facing; one cemetery is on the 

 edge of the plain iteslf. So far, therefore, as the flora of the older portions 

 of these areas represent the ancient vegetation of the same areas, we have 

 in them at present a means of learning something of the kinds as well 

 as the abundance and the habits of the plants which formerly occurred here, 

 and (by inference) of the plants which were in the region in primitive times. 



Below and not far from Ghardaia, in the valley floor, is a very ancient 

 cemetery, or rather a cemetery with a very ancient part. In the old por- 

 tion the drifting sand has obliterated all traces of graves, which have long 

 since been forgotten by the citizens of the town. In the newer portion, 

 farther from the edge of the oued and on higher ground, the sand gives 

 place to clay. In the older portion of the cemetery may be found a fairly 

 rich flora and rather large plants — a striking contrast to the vegetation of 

 the unprotected area immediately without the wall. Here one finds Hal- 

 oxylon articulatum and Henophyton deserti, both species eagerly eaten by 

 animals, as well as Deverra scoparia, Lithospermum callosum, Zilla macrop- 

 tera, and Helianthemum sessiliflorum; also grasses and other plants which 

 I did not know. Something of the abundance and the large size of the 

 plants is indicated in figs. 29, 31, and 32. 



In one of the cemeteries situated against the south wall of the valley, 

 but not including the wall, the conditions are somewhat different from those 

 just sketched; the soil is a sandy loam, with rocks of various sizes in abund- 

 ance, and here may be found a fairly rich flora. In the ancient portion of 

 this cemetery the most numerous species is perhaps Haloxylon articulatum, 

 also Fagonia glutinosa, Fagonia bruguieri, Cleome arabica, Echinopsilon 

 muricatus, Helianthemum sessiliflorum, Zollikoferia resediflora, Salsola sp., 

 and others. The plants are relatively abundant and of fairly large size. 



In a cemetery on the north wall of the valley, reaching from the floor to 

 the plain above, the wall is less precipitous than at other places and there 

 is a small amount of earth. The number of species here is very limited, 

 being confined almost wholly to Haloxylon articulatum, which is fairly 

 abundant; but in the upper portion of the cemetery are also found Peganum 

 harmala and Cap par is spinosa. 

 4 



