RELATIONS OF ANIMALS AND PLANTS 127 



birds which subsist largely or entirely on some 

 particular desert perennial. In Mesopotamia we 

 observed a very close relationship between the salt- 

 loving bush (Suseda) and a Dwarf Gerbille {Dipo- 

 dillus dasyurus). The Suaeda was a bush about 

 3 feet high and grew in salt patches in the desert : 

 a few bushes of Atriplex and Salsola were the only 

 plants found associated with it, and they were not 

 common. Several insects lived on the Suseda, and 

 the Dwarf Gerbilles Uved on any insects they could 

 catch, and on the succulent leaves of the plant. 

 They required no water in captivity, and in nature 

 they and the Suaeda bush lived far from the River 

 Tigris : there is little doubt that they were entirely 

 dependent on it, and the insects found upon it, for 

 food and water. The desert was flat and composed 

 of silt : it was devoid of any form of shelter except 

 the Suseda bushes, and among its roots the Dwarf 

 Gerbilles made their burrows. We may therefore 

 suppose that they derived from the plant not only food 

 and water but also protection from the foxes and 

 occasional jackals which existed in those parts of 

 the desert. So far as I know only one other 

 mammal, a hare {Lepus connori), occurred in the 

 salt patches of desert where the Suseda flourished. 

 It is natural that the animals should be few in a 

 place where only one plant grows and no water 

 can be obtained except from the plant, and it is 

 noticeable that three of the four mammals, the 

 fox, jackal, and hare, are active cursorial forms able 

 to wander far from the Suseda patch in search of 

 water and food. 



