Gnetophyta is a small group of gymnospermous vascular plants represented by three living genera Ephedra , Gnetum and Welwitschia . This lineage dates back to the early cretaceous in the fossil record and is widely considered to be the closest relative of the flowering plants. A distinguishing feature of all gnetophytes is the presence of both tracheids and vessels in their xylem tissue, and absence of archegonia providing evidence that Gnetophyta might have been ancestral to flowering plants. All other gymnosperms (except gnetophytes) possess only tracheids and lack vessels in their xylem tissue.