110 ANIMAL LIFE IN DESERTS 



45° C. : the air felt intensely dry and was charged 

 with sand-grains which produced a smarting effect 

 on the exposed skin. The wind went down during 

 the night, but it remained hot and no dew fell. 

 The storm continued in this way for the next two 

 days, and its effect on the vegetation was very 

 striking. All flowers and young parts of plants 

 had shrivelled, the upper portions of the green 

 branches of Calligonium had died and had often 

 been broken off, the fruits of this plant had dried 

 and had become quite hard : most of them were 

 detached from the plants and were blown about 

 in all directions. The upper portions of the stems 

 of Heliotropium luteum were withered and dead, 

 and had lost all the younger leaves. AU the plants 

 appeared very much withered, except Imperata 

 cylindrica, which seemed untouched. Many plants 

 seemed partially uprooted, especially PuUcaria and 

 Polygonum ; in reahty the wind had removed the 

 surface layers of the sand round them, and 20-25 cm. 

 of rootstock were exposed — this showed the im- 

 portance of being deep-rooted. The surface roots 

 of Panicum turgidum were very frequently laid bare. 

 In other cases plants were wholly or partially bm^ied." 

 The direct effect of wind upon the animals, 

 especially the smaller animals, also merits discussion, 

 as it has apparently caused modification of habit in 

 some animals and of structure in others. Certain 

 small Blue Butterflies (Lycaenidae) which inhabit 

 the Great Palsearctic Desert possess the power of 

 continued flight within one small bush, from the 

 shelter of which they seldom issue. Butterflies of 



