Two localities only in the Nomad Mountains were seen. One was in a pass through which caravans travel _en route_ to Laghouat, from the High Plateau or the more distant Tell; the second to the east of the pass is much less often visited by flocks. The physical plant conditions appeared to be the same in both locations. As one approaches the mountains from the south the number of plants grows less until on the south face they quite disappear, but on attaining the crest they quickly increase and form a noticeable element in the landscape. In fact, the flora of the northern gentle slope, where the soil conditions are relatively favorable, is much richer than on the plain or the dunes. Had the shrubs been of good size they would have been very conspicuous.[10] A certain area on the north slope of the Nomad Mountains, not far from the pass through which the Oued Mzi goes, was selected for making a census of the plant population. Here the number of individuals, as well as their size, showed that the moisture relations were good as compared with those of the plain. On an area 16 meters square 422 living perennials were found, mainly of the following species: _Acanthyllis tragacanthoides_, _Asparagus spinosa_, _Deverra scoparia_, and _Zollikoferia spinosa_. The most numerous, _Zollikoferia_, was represented by 96 individuals. The general character of the habitat and the plants is sufficiently well shown in fig. 8 and does not need further mention in this place. EFFECTS OF GRAZING ON VEGETATION NEAR LAGHOUAT. It is generally recognized that a potent influence is exerted by man, and the lower animals, in shaping the flora of an arid region, not only as regards the kind and number of plants, but also as concerns certain of the leading characteristics of the plants themselves. The action is largely such as brings about a survival of the “useless” forms, so that we do not know, from the plants we meet in the desert to-day, how many or what kinds of plants it might support. It also may be true that no desert shows the modifying effects of the causes suggested more than the northern Sahara.