leathery leaf surface. Cushion plants and bulbous plants are such adapted
forms. Trees and shrubs with these characteristics are concentrated in loca-
tions with deeper soils, i.e. in wadi beds, depressions and in the foot zone of
escarpments. Seasonally and episodically growing grasses, herbs and bulbous
plants also occur, covering patches of the soil surface. For the growth of the
vegetation it is important which kind of surface run-off prevails. It can be
linear or diffused, depending on the topographical conditions.
After Kassas (1971: 477ff ) we can differentiate between three regional types
of vegetation in Egypt:
• the type of the Mediterranean coastal zone, which spreads southward to
29o
 latitude
• the type of the coastal region of the Red Sea
• the type of the Western Desert, the Eastern Desert and the Nubian
Desert.