This report deals with some results of the experiments the authors carried on, as a part of studies on the cuttings of forest trees, with an intention to clarify the relationship between the rooting responses of cuttings and their phytohormones. To make these problems clear, the authors experimented in the first place with the rooting behavior by the method of water culture, using the cuttings obtained from the mother trees of Populus nigra and Metasequoia glyptpstroboides. In the second step the knowledge derived from the first experiment was to apply the experiment on Pinus densiflora cuttings, which was recognized as very difficult material for rooting. 1. Relationship between the rooting responses of cuttings and their hormones. 1) In Metasequoia, the cuttings taken from the lower part of the crown contained more growth inducing substances and less growth inhibiting substances than that from the upper part. In the cuttings of Cryptomeria japonica and Metasequoia, the growth inducing substances seemed to increase, and the inhibiting substances to decrease, in accordance with the advance of age. The rooting was most favorable when the hormone ratio (the ratio of the volume of growth inducing substances to the growth inhibiting substances) was high. 2) Rooting of cuttings was induced when the hormone ratio was adjusted by hormone treatment. The effects of the treatment seemed to vary with the degree of rooting ability of cuttings. The effect, however, was remarkable on the cuttings having a rooting ability of 30% (rooting percentage) in a non-stabilized state, and the effects decreased as the rooting ability rose or decreased from this figure. 2. Cuttings of Pinus densiflora In order to improve the ability of the cuttings to root in P. densiflora, the part of the top part of the lateral branches of the 10--13 years old mother trees were cut out, and from the section developed adventitious branches. 3) The adventitious branches showed a higher hormone ratio than the ordinary ones, and the former contained more nitrogen and less carbon than the latter and showed a smaller C--N ratio. 4) The water exracts of P. densiflora cuttings had no apparent restraint on the rooting of Populus nigra ones. 5) The cuttings of leaf-bunddles obtained from the adventitious branches kept the waters balance for some time being planted compared with the ordinary ones. From these results the authors thought that the adventitious branches provide more excellent conditions of inner part than the ordinary ones for the rootings. 6) When the top parts of lateral branches of the mother trees of 10--12 years old were cut off in the middle of May, the adventitious branches developed. The cuttings of these (adventitious ones) were planted in the autumn of the same year and in the next spring they rooted much better than the ordinary ones. 7) When the top parts of lateral branches of the mother trees were cut off in the middle of May, the adventitious branches reached the full growth within the same year, and the cuttings obtained from these showed good rooting. When the branches of the mother trees were treated, the rooting was not good. 8) The rooting of the cuttings of adventitious branches, which contained only one bud, was best. The rooting of those from which all of the buds was cut off was good in the second place and for those on which all of the buds were left was feeble. 9) Hormone treatment took effect for the cuttings of adventitious branches: the cuttings which retained all of the buds showed a high percentage of the dead cuttings and the rooting percentage was not improved by the treatment. But both the number of roots, and the total length of main roots per rooted cuttings were fairly increased. The cuttings which retained a single bud and the ones from which all of the buds were cut off were both encouraged by the hormone treatment in regard to the percentage of rooted cuttings, the number of main roots, and the total length of main roots per rooted cutting. Therefore, the hormone treatment was especially effective on the cuttings which retained only a single bud. 3. Environmental conditions 10) The percentage of the dead and decayed cuttings became larger in proportion to the amount of organic materials in the cutting medium. 11) Under the shade of 75 ~ 90%, the percentage of rooted cuttings was very small, while that of the dead cuttings was high. In the shade of 25 ~ 50%, the percentage of the dead cuttings was smaller than that of the cuttings which were not given any shade (open) at all. However, it seemed to more or less slow down for the rooting. 12) It seemed that the favorable temperature for a cutting medium ranged from 23℃ to 30℃.