A sheath-like plant organ (PO:0009008) that surrounds the radicle (PO:0020031) of a plant embryo (PO:0009009) or the emerging root (PO:0009005) of a seedling (PO:0000003). [source: ISBN:0471244554, PMID:19386806, PO_REF:00003]
Found in Poaceae and some other monocots as well as some gymnosperms. Protects the emerging radicle in a plant embryo or seedling. The parenchyma cells of both the coleorhiza and epiblast may function in storage.