As the cotyledon elongates, a notch forms on one side. This notch deepens as a marginal sheath-like extension of the cotyledon forms. Within the notch surrounded by the sheath, the shoot apex develops. During germination, the first leaf will emerge from this enclosure through a small slit above the sheath. In Commelina L-, the shoot apex is surrounded by a cotyle-donary sheath and the bulk of the cotyledon
over-tops the shoot apex at a 90° angle