Mature Embryo
A typical dicotyledonous embryo, as seen in a median longitudinal section, consists of an embryonal axis having two broad cotyledons. The portion of embryonal axis above the level of cotyledons is termed epicotyl which terminates in the plumule or stem tip. The cylindrical portion below the level of cotyledons is called the hypocotyl which terminates at the lower end in the radicle or root tip. The root meristems is covered by a well defined root cap.
The embryo of monocotyledons, possesses only one cotyledon. The grass embryos is highly specialized and has received a great deal of attention. It has a single cotyledon in the form of scutellum, which appears to be laterally attached to the embryonal axis. At its lower end the embryonal axis has the radicle and root cap, enclosed in an undifferentiated part of the embryo called coleorhiza. On one side the coleorhiza is given out a small outgrowth called the epiblast. The portion of embryonal axis above the level of attachment of the scutellum is termed epicotyl. It has a shoot apex with some leaf primordia, enclosed in a hollow foliar structure called the coleoptile.