During the 7th century the power of the Eastern Roman (Byzantine) Empire was challenged by the Sassanids of Persia, who invaded Egypt in 616. They were expelled again in 628, but soon after, in 642, the country fell to the Arabs, who brought with them a new religion, Islam, and began a new chapter of Egyptian history.
Bark comprises all the tissues outside the vascular cambium of a vascular plant. The majority of the bark of woody plants develops from three meristems: the vascular cambium that gives rise to the secondary phloem, the phellogen that gives rise to the cork and dilatation meristem that produces parenchyma cells to avoid cracking when the axis increases in diameter.
Trunk wounds that penetrate the bark will damage the cambium layer, a thin layer of vascular tissue, which is vital to movement of water and nutrients. If less than 25% of the bark around the trunk has been damaged, the tree will probably recover. When fresh wounds occur on the trunk, the injured bark should be removed carefully, leaving healthy bark that is sound and tight to the wood. A wound dressing (tree paint) is not necessary.