Bark is outer covering of plant made of schlerenchyma. 
epidermis is the inner layer  of the bark.
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The difference between epidermis and bark is that epidermis is the outer, protective layer of the skin of vertebrates, covering the dermis while bark is the short, loud, explosive sound uttered by a dog or bark can be (countable|uncountable) the exterior covering of the trunk and branches of a tree or bark can be (obsolete) a small sailing vessel, eg a pinnace or a fishing smack; a rowing boat or barge. 
1. Single layered group of cells that cover plant leaves, flowers, root and stem.
2. It is permeable in nature. Protect against water loss, gas exchange and absorb water and minerals.
1. The cork is a water proof protective layer (bark) present on the cork trees. It consist of dead cells.
2. Impermeable in nature. 
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