The author has studied the water relation as to the transpiration and the water-absorption of the thirty- three species of herbs, including mesophytes, suculents, both halophitic and non-halophitic, for the first twentyfour hours, under the potometer condition, either in well-water or in seawater. The value of the transpiration and of the water-absorption were converted into the relative value of the "unit volume of tissue-powder" of professor KOKETSU- : For the sake of the comparative study, the respective value of transpiration and of the water-absorption of each species of plants were reduced to the relative values comparing them to the atomometer. The said two values and their sum were largest in the case of the mesophytes, but smallest in the case of the non-halophitic succulents;-this was cosntant under the two water conditions, in spite of the fact that there existed a marked reduction of values, when the sea-water used, instead of well-water. The ratios of the value of water-absorption to the transpiration were about 1 in the case of the mesophytes; much larger than 1 in the case of the halophitic succulents, but a little larger than that of the non-halophitic succulents under the well-water conditions. When the sea water used, the values of mesophytes became less than 1; the plants getting wilted, though there was no marked change in the values of succulents, both halophitic and non-holo-phitic. Each succulent much resembled the other, not only in the outward appearances, but also in the tendencies of the water relations above described. Some abnormalities in appearance, however, to be observed in the case of the non-halophitic succulents treated with sea water. It may be inferred, therefor, that the two succulents, the halophitic and non-halophitic, differ from each other, notwithstanding their structural likeness, in the physiological behaviour.