Determinations of the concentration of bicarbonates in soil samples taken from immediate contact with roots of plants and in other samples taken at a distance of 2-4 in. from the roots were made in both greenhouse and field soils. Of 66 such pairs of determinations, 53 showed a higher concentration of bicarbonates around the roots, 4 showed equal concentration, and 9 showed higher concentration in the samples away from the roots. With wheat, corn, and kafir the maximum difference in concentration of bicarbonates occurred at the fruiting period of the plants. Since CO2 excretion of roots is greatest at this period, these results seem to indicate that plants are capable of exerting an appreciable solvent action on soil minerals through CO2 excretions of their roots.