Through the preliminary observation of some external characteristics of three lines (Ehl-jioou-narn, Ehl-jioou-aai, Taih-yiin No. 1) of rice (Oryza sativa L.). we know that when the differentiation of the shoot apex takes place, the distance bet- ween two adjacent of the last 3,4 leaves of the plant becomes prominently elongating. Rice and some other graminae such as wheat, millet, etc. are charac- terized by this morphological feature. The differentiation of the shoot apex of rice initiates at a definite double Oleaf period, passes through the first, second and third elongating periods of distance between pulvini successively and then emerges. There is no great external- ly morphological difference during the differentiation of the shoot apex among the early maturing or the late maturing varieties of rice. In growing plant, any central young (0 leaf) will make a chance to coincide with leaf, forming double 0 leaf. During the stage of vegetative growth, the double 0 leaf plant has two central young leaves, denoted by -1 leaf and -2 leaf, the blades of which are more slender; while during differentiation of the shoot apex the double 0 leaf plant has only one central young with compara- tively broad blade so that it is possible to make a distinction from that of vegeta- tive stage. According to this characteristic, the floresence of any variety of rice may be estimited.
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