1. Calcium concentration of recretion sap was nearly constant in certain range of the concentration of KNOP'S solution. When the nutrient solution became diluted, the calcium concentration in the recretion sap suddenly fell. When the nutrient solution became concentrated, the concentration of calcium in the recretion sap also rised. The calcium concentration in the exudation sap was lower than that of the nutrient solution when the nutrient solution was comparatively concentrated and higher when the nutrient solution was comparatively diluted.
2. The amount of calcium exuded per hour was almost constant in certain range of KNOP'S solution and diminished in the low concentration of calcium in the nutrient solution.
3. The volume of exudation sap per hour was almost constant in certain range of KNOP'S solution and diminished when the nutrient solution was more concentrated than natural KNOP'S solution or more diluted than 1/8-KNOP'S solution.
4. When the nutrient solution was simple KH
2PO
4 solution, recretion ceased when the solution became more concentrated than 0.075%. As the concentration of salt in KNOP'S solution is much higher than this, it seems that recretion has not necessarily to do with the sum of the concentration of salts in the case of KNOP'S solution.
5. The relation between the potassium concentration in the exudation sap and the nutrient solution showed equal tendency with calcium. But it must be noted that the potassium concentration was higher than that of calcium. The amount of potassium exuded per hour was not constant in some range of KNOP'S solution as calcium, but decreased as the concentration of nutrient solution became diluted. In individual plants, the variation of the concentration of calcium and potassium took equal tendency.
6. In soil-cultured plants, the recretion was more vigorous in comparison with that of the water-cultured plants.
7. From the results obtained in
Colocasia, the absorption of salts seems not to take place in epithem.
8. The concentration of calcium and potassium was not always low but often high when the volume of exudation sap was great. So great amount of calcium and potassium was excreted in strong recretion. The subject for investigation was suggested by Prof. Dr. H. NAKANO, to whom I wish to tender my best thanks for his kind directions.
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