MOUNTAIN FLORA OF GREAT ATLAS. 445 



together form about one-half of the Flora of the region here 

 discussed, amount to very nearly two-thirds of the species found 

 in the higher zone. We remark that of these northern plants 

 none are of Alpine or Arctic t5^e, that nearly all belong to 

 what has been called the Germanic Flora, and all are plants 

 of the plain, not in Europe characteristic of mountain vege- 

 tation. • 



Of the species belonging to the Mediterranean region, 

 which constitute more than one-half of the vegetation of the 

 middle zone, and about one-third of that of the higher zone of 

 the Atlas, the large majority are widely diffused species. The 

 remaining number, for the most part mountain plants, may be 

 divided into three neaiiy equal sections, some being common 

 both to Southern Spain and Algeria, others to the Atlas and 

 Southern Spain exclusively, and others to the Great Atlas and 

 the Lesser Atlas of Algeria. Nothing indicates any special 

 connection with the Floras of either of those regions. 



The absence of any distinct generic types from the Great 

 Atlas Flora has already been remarked. It is not less impor- 

 tant to note the absence of any of the southern types, charac- 

 teristic of the sub-tropical zone, some representatives of which 

 are found in the same or even in higher latitudes, in Arabia, 

 Syria, Persia, and Northern India, and which also appear in 

 the Canary Islands. We finally are led to regard the mountain 

 Flora of Marocco as a southern extension of the European 

 temperate Flora, with little or no admixture of extraneous ele- 

 ments, but so long isolated from the neighbouring regions, that 

 a considerable number of new specific types have here been 

 developed. The physical causes which have operated to bring 

 about these conditions are doubtless numerous and complicated, 

 but the most important of them are easUy indicated. The in- 

 fluence of the Atlantic climate, and the prevaiUng direction of 

 the aerial and oceanic currents, have fitted this region for the 

 habitation of such northern species as do not require a long 

 period of winter repose. In the present condition of the 

 African continent, the Great Desert, extending for a distance of 

 700 or 800 mUes between the Atlas and the river region of 



' The only apparent exception is Sagina lAimcei. This is habitually 

 a mountain plant ; but in Germany it is often seen in the moorland 

 region, at a level of about 2,500 feet above the sea. 



