A portion of primary xylem (PO:0005849) tissue that has as part one or more metaxylem tracheary elements (PO:0025576) embedded in parenchyma (PO:0005421) tissue and may contain xylem fiber cells (PO:0000274). [source: ISBN:047125208, ISBN:0471738433, POC:curators]
Comment
Metaxylem has larger tracheary elements (PO:0000290) than the protoxylem (PO:0000272), and develops after the formation of the protoxylem, once elongation of the plant axis (PO:0025004) has completed.