THE VOICE OF THE DESERT 



no 



many plants grow upon trees, have no roots in the ground, 

 and depend upon rainfall or dew. But no plant in the 

 desert can do that because rainfall is too infrequent and 

 dew nonexistent, except perhaps in winter. In air so dry, 

 the dew point is usually at a below-freezing temperature 

 — ^which is certainly not to be looked for except during the 

 early mornings of midwinter. And no plant of either the 

 desert or the tropics can imitate Dipo's feat. Plants do not 

 eat hydrocarbons from which the kangaroo rats make their 

 water. As a matter of fact plants make hydrocarbon and 

 to do that you have to use up water, not create if. 



Moreover, though all of the three less radical solutions 

 have been hit upon by both plants and animals, they do 

 not seem to be equally characteristic of both. On the 

 whole, plants tend to store as well as to economize; on the 

 whole, animals tend to have httle or no provision for stor- 

 ing. They can get along on little and hence go long periods 

 without replenishing the supply, but that is principally be- 

 cause they use so little, not because they put aside a supply 

 to be drawn upon. Dipo doesn't. Even his blood is not un- 

 usually watery at any time. 



There is, however, at least one desert ailimal who may 

 violate the general rule and is worth mentioning for that 

 reason, as well as for some others. He is the desert tortoise, 

 a great lumbering fellow, scaly skinned and hard backed, 

 who may be almost a foot in length, eight inches wide, and 

 stand five inches off the ground. He is a formidable look- 

 ing creature who appears, as most turtles do, not only very 

 ancient as a type but almost equally ancient as an indi- 

 vidual. He also looks rather threatening, though he is ac- 

 tually completely inoffensive — which all turtles certainly 

 are not, as anyone who has ever had any experience with 



