54 ANIMAL LIFE IN DESERTS 



another that they do not colour the landscape, except 

 for a short period after rain has fallen. In most 

 deserts bushes are rare and tend to become con- 

 spicuous features of the scenery, if they are present : 

 trees are so rare that they are regarded with venera- 

 tion by desert-dwelling races in more than one part 

 of the world. At certain spots in the desert water 

 is available in relatively large quantities : such spots 

 are oases, and are characterized by a dense growth 

 of vegetation, often consisting of plants which do 

 not and cannot grow in the surrounding desert, and 

 which are not found outside the oasis, until a second 

 oasis is reached. This growth of vegetation provides 

 food for a number of animals, many of which are 

 specially dependent on one of the oasis plants, or 

 for some other reason unable to live in the surround- 

 ing desert. The edge of an oasis is usually extremely 

 sharply defined : the plants of the oasis grow up 

 to the edge of the area which has the abundant water 

 supply, and there they stop abruptly. Fig. 23 

 illustrates this admirably.^ On the left is a dense 

 growth of poplar, fig, apricot, bramble, and many 

 other wild and cultivated plants, dependent on a 

 perennial spring in the bottom of a " wadi " : on the 

 right, a yard or two away, is the " wilderness of 

 Judaea," with no living plants except Atriplex 

 halimus, and not many of that. The photograph 

 was taken in July, after the spring annuals had died : 

 their dried remains may still be seen. Fig. 22 gives 

 a general view of the same country. 



Very few natural oases exist, and many of them 

 1 See also Fig, 10, opposite p. 42. 



