In a study reported in the previous paper (Hanawa and Ishizaki, 1953) , it was found that the embryo of Sesamum indicum L. was a suitable material for investigating morphogenesis, and that the embryo which was deprived of seed-coat and divided by a longitudinal cut into halves was capable of growing, that is, the operation did not essentially prevent the growth of the seeding but the divided plumules regenerated normal shoots. Moreover, at the time of regeneration of new plumule, the first

more »

... ge leaves frequently fused side by side into one double-leaf. Pilkington (1929) investigated regeneration of shoot apices of Vicia faba and Lupinus albus after decapitation, a median split or a prick of the apex. Snow and Snow (1935) cut the decussate apex of Epilobium hirsutum by a diagonal cut, and found that new apices were formed from both halves by regeneration. Similar cases were also exemplified by Ball in a series of his experiments (1948, 1950a, b, 1951, 1952, 1955). The regeneration of the new plumule in Sesamum occurred in the same manner as reported by the investigators cited above. However, the formation of the doubleleaf was never studied by them. The causes and the processes of the double-leaf formation are particularly investigated in the present experiments. Material and Methods. In the earlier stages of development, Sesamum indicum L. shows a decussate phyllotaxis, which, however, turns gradually into a spiral one. The first foliage leaves arise simultaneously on both sides of the apex in its intercotyledonary plane. The second pair of leaves is set in the plane of the cotyledons. The rest of the pairs decussates for several nodes, and then. two members of a pair shift out of the same level so that the decussate arrangement is eventually lost in the upper part. In the present experiment the positions of the opposite leaves of the first pair were frequently so moved on the same level as to unite together (Fig. 2) .