To determine the amylase fromation mechanism and the effect of GA. in germinating barley seeds, they were divided into embryo-less seed, isolated embryo, aleurone layer and pure endosperm etc., treated with GA, and cultured separately or in mixed lots. The result obtained are as follows. 1) The amylase of barley seed is formed in the aleurone layer under the effect of inducing materials excreted from the embryo. 2) The embryonic materials amylase formation could be substituted for by GA. Therefore it can be presumed that the substance produced by the embryo which induces amylase synthesis is probably GA or material similar to it.