Parenchyma cells, description

The other major cell wall structure found on longitudinal tracheids is termed a ray crossing and is illustrated in Figures 7 and 8. Ray crossings consist of pits which interconnect longitudinal tracheids to ray parenchyma. Due to the diverse structure of ray crossing pits they are extremely useful in the identification of wood and wood fibers. However, since identification is beyond the scope of this review, a description of the different types of pits found in ray crossings is not included. 

Based on the wood anatomical descriptions presented, it is obvious that hardwoods and softwoods differ considerably from each other. For example, vessels are present in hardwoods and absent in softwoods. In hardwoods more cell types, shorter cells, more parenchyma and a more variable arrangement of cell types occur. The relative uniformity of softwood anatomy is the result of the preponderance of a single type cell, the longitudinal tracheid. 

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