Plant Defences 



107 



districts. Compare the rainfall of these regions with that of 

 neighbouring districts. 



Fortunately for the plants, these waterproof garments are 

 also useful summer styles. The hairs reflect the bright light 

 from the plant, and keep a cool layer of air next the leaf, while 

 preventing too rapid evaporation, although transpiration helps 

 to keep the plant cool, just as it makes us cooler to perspire 

 in summer. 



Fig. 91. — Cotyledon reticulata, Th. 



The thick waxy coverings on the leaves of Senecios, Cras- 

 sulas, and Aloes, which shed rain, also prevent the escape of 

 water in summer. Low-growing plants are often protected 

 by incrustations of lime, which also absorbs and retains 

 moisture. 



Besides especial coverings of leaves, many Karroo plants 

 have their leaves packed as closely as possible. In Crassula 



