Ko e ʻakau sukau (gnetophyta) ʻi he saienisi ʻo e ʻakau ko e taha pē ʻo e vahe ʻo e ngaahi meʻamoʻui ʻe 5 ʻi he ʻuluʻivahe ko e ʻakau tengaʻiʻakau (spermatophytes). ʻOku ne kau ki he pupunga ʻo e tengaʻiʻakau telefua (gymnospermae), tatau mo e