Dry aggregates were separated from the "latossolo roxo" and red-yellow podzolic-ortho soil to find out the effect of the size on the growing of aerial parts and on the development of the root system of the corn plant, grown in pots. It was noted that the size of aggregates of the two soils presented great differences concerning the development of corn plants. In the "latossolo roxo" the < 1.0 mm size class was the most appropriated for the plant growing and development of the root system. In the red-yellow podzolic-ortho soil, the best conditions for growing were presented by the size class 4.0 to 2.0 and 2.0 to 1.0 mm in diameter. The variation for the growing of the aerial part and the root system might be attributed to the physical nature of the soil. The intensive digging up of the red-yellow podzolic soil seems to have an unfavorable effect on the development of the root system of the corn plants.