We had already perceived that the vegetation of this part of the Atlas is much less varied than that of Aït Mesan; and this impression became stronger with subsequent experience. Something may be due to the fact that we had there more time and opportunity for close examination; but this could only slightly alter the general result. This may be partly due to the more permeable character of the rocks in the Amsmiz valley preventing moisture from resting on the surface; and in part to the fact that, although nearer to the Atlantic, the range here is less lofty, and the precipitation of vapour, in the shape of rain or snow, is less frequent and abundant during the summer months. The subject is more fully discussed in Appendix E; but it will be seen by reference to our lists, that only seventy-six species seen by us were confined to the Amsmiz valley, that nearly twice as many were found common to both valleys, while more than three times that number were seen in Aït Mesan, but not in Amsmiz. If a similar comparison be made as to the endemic species which, as far as we know, are peculiar to the flora of the Great Atlas, the proportions are nearly identical. A further peculiarity of the vegetation here, is the greater resemblance which it bears to that of the mountains of Southern Spain than does that of the Aït Mesan valley. Several plants not before seen by us were identical with Spanish species; and of the undescribed forms here collected, at least four have their nearest allies among the endemic plants of the Peninsula. Two or three characteristic species of the Algerian flora were also seen here for the first time; but these will doubtless be found to extend through the intervening region when this has become accessible to scientific travellers.