204 AFRICA 



mostly bare, with blue-green patches of alfa grass, and 

 only in the ravines and at the heads of gorges, sheltered 

 and inaccessible, can scattered woods of green oak, 

 Aleppo pine, and juniper be discovered : they are 

 probably vestiges of once much more extensive forests. 

 The high plateaus can support but temporarily the 

 passing herds of sheep and goats, or trains of camels 

 and horses. The esparto grass is, however, a valuable 

 product, the collection of which occupies a few hundreds 

 of workmen scattered in wandering communities along 

 the railway lines. 



The African Islands. The Canary Islands grouped 

 on the west coast of the Sahara are able, by reason 

 of their altitude, to condense a certain amount of oceanic 

 moisture, and form a link between the Mediterranean 

 region and the desert. The lower slopes are related 

 with the neighbouring mainland in point of aridity. 

 Their vegetation is of semi-desert character, consisting 

 mainly of succulent plants. The dragon tree and the 

 Canary date-palm are the chief trees, in addition to the 

 olive, the Atlantic pistacia, and the Phoenician juniper. 

 Outside the cultivated alluvial valleys, this belt offers 

 little else than stone fields and rocks bestrewn with 

 succulents and meagre bushes of the broom and heather 

 type. The middle belt, from 4,000 to 7,000 feet, has 

 open slopes clad with scrub of mediterranean character, 

 and in the secluded gorges, temperate evergreen rain- 

 forests have found refuge. The extension of Canary 

 pine-forests above the preceding zone coincides with 

 the belt of clouds and mists which frequently hide the 

 upper slopes. More or less scattered bushes of retama, 

 a kind of broom, characterize the Alpine zone, which 

 reaches 8,500 feet. 



The Canary Islands have played an important part in 



