424 APPENDIX G. 



elements, represented by plants of the low country that reach 

 the base of the mountains, but do not penetrate the interior 

 valleys, and if these had been admitted the special features of 

 the mountain Flora would have become less apparent. The 

 plants collected in the course of a somewhat hurried excursion 

 from Seksaoua, when we reached a height of about 1,600 metres, 

 have been designedly omitted. On such occasions attention is 

 to a great extent monopolised by the new and rare species not 

 hitherto seen in the same region, whUe comparatively familiar 

 forms are less carefully noted. Collections made under such 

 circumstances rarely give a moderately complete report of the 

 vegetable population. 



In ascending to the higher region of mountains that 

 approach to the limit of vegetation the absolute number of 

 species is so much smaller that this source of error is far less 

 apparent ; and it is not likely that in the two ascents which we 

 made to the dividing ridge of the Atlas many species that came 

 within our range of vision were overlooked. The following 

 tabular arrangement shows that in the Ait Mesan valley, where 

 we spent the greater part of six days, we collected 375 species 

 of phsenogamous plants, to which have been added three subse- 

 quently found there by MM. Eein and Pritsch ; while in the 

 Amsmiz valley only 223 species — or less than three-fifths of the 

 above number — were collected. Of these 146 species are com- 

 mon to both valleys ; so that our list does not in all exceed 455 

 species of flowering plants, to which I have added 10 vascular 

 cryptogams, of which two only were found in the Amsmiz valley. 



In the following list I distinguish a middle zone, extending 

 from 1,200 to 2,000 metres above the sea, and a superior zone 

 including all above that limit ; the latter corresponding pretty 

 nearly with the sub-alpine and alpine zones of the higher moun- 

 tains of Europe. With reference to their distribution I have 

 divided the species into four categories : 1, Mid-Euro)3ean, those 

 extending to Central Europe, of which more than three-fourths 

 belong to the British Flora : 2, wide-spread Mediterranean, 

 extending beyond the bounds of the three adjoining regions, 

 Algeria, the Spanish peninsula, and the Canary Islands : 3, 

 confined to adjoining regions ; that is, to one or more of those 

 j ust enumerated : 4, endemic, known only in the Great Atlas, 

 or the neighbouiing provinces of Marocco. 



