Lignified
parenchyma cells surround the vessels of the
metaxylem, however, the parenchyma in the
surrounding intercellular space always remains
unlignified. The parenchyma cells that surround
the vascular bundle are usually smaller
than those of the general parenchymatous tissue
and have a higher number of pits in their
walls (Grosser and Liese 1971, Liese 1998)