Hemicelluloses from the bark of Ehgelmann spruce (Picea engelmannii).

The term "bark" is applied in common parlance to denote the material that surrounds the woody substance (xylem) in a mature tree. It is thus situated outside the cambium which is the living tissue of a growing tree. The anatomical structure of bark is rather complex but in general it can be said that the bark tissue is composed of different kinds of cella, such as sieve, longitudinal parenchyma, ray parenchyma, fiber cella, etc., some of which are also typical of the wood tissue. The physiological function of these tissue elememts in the bark is mainly concerned with the translocation and storage of solutes. As the tree matures, the outermost layers of the bark are broken and die by exposure and especially by the stoppage of food and water supplies. This layer is commonly referred to as the outer bark as opposed to the active tissue beneath it which is termed, inner bark or phloem. [...