146 SPECIAL FEATURES 



economic point of view being the archil hchen from 

 which the dye called litmus is obtained. Darwin 

 describes this lower zone as uninviting in the extreme, 

 the scanty brushwood leaving the black basaltic lava 

 exposed, and giving the district the appearance of an 

 iron-smelting region in the ' black country ' of England. 

 But the clouds hang low, and above an elevation of 

 about eight hundred feet not only is there abundant 

 rain during the raiay season, but even at other seasons 

 a constant mist keeps the vegetation fresh. The plants 

 of the two regions differ fundamentally, and in the 

 upper cultivated plants from many climates thrive. Of 

 the native vascular plants, about one-half are pecuhar 

 to the islands. The group consists of five principal 

 and eight small islands, with a total area of nearly 

 3,000 square miles. The hills range in height from 

 3,000 to 4,000 feet. The more conspicuous bushes and 

 trees are species of euphorbia, cactus, and acacia, 

 so that the islands generally resemble savanas and 

 desert regions in their vegetation. Palms are entirely 

 absent. 



Turning now to the fauna, we find that mammals are 

 practically absent. There are two mice, but of these 

 one belongs to the widely distributed genus Mus, and 

 has doubtless been introduced ; the other belongs to 

 a South American genus (Hesperomys), and has also 

 possibly been introduced. That there is nothing in the 

 conditions of the islands to prevent the existence of 

 even large herbivorous mammals is, however, shown by 

 the fact that goats, pigs, horses, &c., introduced by 

 man, have become wild, and have multiplied exceed- 

 ingly- 



The birds present some interesting features. About 

 seventy species, according to Wallace, have been 



