bark
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Bark of a white oak
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General term for the outer protective covering of the stems
of woody plants. It consists of several layers, including the secondary
phloem, cork
cambium, and cork. The last of these, which
is waxy and waterproof, is the thickest and hardens into the tough, fissured
outer cating.
The bark is impervious to water and protects the stem from excessive evaporation;
it also protects the more delicate tissues within. Lenticels (pores) in
the bark allow gas exchange between the stem and the atmosphere. Extracts
of bark may have medicinal uses, e.g., quinine
from chinchona bark. Related category
• BOTANY
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