In a cereal grain (e.g., wheat), the single cotyledon of embryo is represented by the scutellum. Scutellum is specialized for nutrient absorption from the endosperm. Coleoptile is a modified ensheathing leaf that covers and protects the young primary leaves of a grass seedling. Coleorhiza is a sheath like structure found on the radicle which covers and protects it during the growth into the soil.
Related Theory
The scutellum is a modified cotyledon, or seed leaf in grasses which never develops into a green structure but serves only to digest endosperm and transfer nutrients to the rest of the embryo. Scutellum is diploid while endosperm is triploid.