Outermost layer of endosperm of maize grain is
In monocotyledonous endospermic seed, endosperm is surrounded by a special one- cell thick layer, called aleurone layer. The cells of aleurone layer are filled with proteinaceous aleurone grains which play an important role at the time of germination. Maize grain is a monocotyledonous endospermic seed. So, the correct answer is 'Aleurone'.