The previous references indicate that on incubating at 30' C under waterlodged condition, the mineralization of organic nitrogen of the paddy soil hardly takes place in wet soil untreated, whereas markedly in soils respectively air-dried, added sufficient alkali to reach over pH 9, and added the neutral salts such as NaF, Na2HPO4, Na2C2O4 etc, which are soil humus eptizable. The incubation of wot soil untreated, however, leads to the mineralization of soil organic nitrogen by raising the incubating temperature from 30℃ to 40℃. In this paper, we called all the organic matter easily mineralized by treatments above mentioned "easily decomposable organic matter, and studied, in the first, on the relation of such organic matter to Tyulin's so-called organomineral colloidal complexes of paddy soil?G1, and G2 groups?, and in the second on it's forms. From the results obtained in the first experiment; it was concluded that (1) the organic nitrogen mineralized by air-drying paddy soil is largely originatedfrom G1, (2) that mineralized by raising the incubating temperature from 30℃ to 40℃, with the exception of the annual water-lodged paddy soil, is largely originated from G2, (3) that mineralized by treating the paddy soil with alkali and adding the neutral sals is respectively originated from both G1 and G2. It was, therefore, elucidated that "easily decomposable organic matter" is held on Tyulin's so-called G1 and G2 groups. Now, when we call the organic matt e r which is peptized by the Tyulin's method "easily soluble humus", "easily decomposable organic matter" is presumably contained in it. The results obtained in the second lead to the conclusion that easily soluble humus is for the most part Simon's so-called rotted products and Page's so-called non-humic matter, and that "easily decomposable organic matter" is a part of the rotted products and non-humic matter.