CH. I. CHARACTER OF THE VEGETATION. 255 



We were led by the difference in geological structure 

 to anticipate a considerable change in the flora, as com- 

 pared with that with which we had already made acquaint- 

 ance ; and this expectation was confirmed by what we had 

 seen during our morning's ride, and still more by our 

 afternoon herborisation on the rocks and slopes above 

 Iminteli. 



We had already perceived that the vegetation of this 

 part of the Atlas is much less varied than that of Ait 

 Mesan ; and this impression became stronger with subse- 

 quent experience. Something may be due to the fact that 

 we had there more time and opportunity for close examina- 

 tion ; 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 Ap- 

 pendix 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 Ait Mesan, but not in 

 Amsmiz. If a similar comparison be made as to the en- 

 demic species which, as far as we know, are peculiar to the 

 flora of the Great Atlas, the proportions arenearly 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 Ait Mesan valley. 

 Several plants not before seen by us were identical with 

 Spanish species ; and of the undescribed forms here col- 

 lected, at least four have their nearest allies among the 

 endemic plants of the Peninsula. Two or three charac- 

 teristic species of the Algerian flora were also seen here 

 for the first time ; but these will doubtless be found to ex- 



