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For the two major groups, granites and basalts, he found that basaltic soils are higher in lime and phosphoric acid than granitic soils. The potassium and nitrogen contents could not be definitely correlated with parent material. —Soil formation and development of vegetation are concomitant. As the soil features change, the plant cover adjusts itself accordingly. In very immature soils, the situation is different. Within a given climatic region, the growth of vegetation is mainly determined by the character of the parent material, whether limestone, igneous rock, sand deposit, or clayey shale.

In point of fact, this procedure brings us back to the firstmentioned criterion of maturity, namely, the morphological definition of Marbut, which states that a soil is mature when it possesses welldeveloped profile features. The dynamic and the morphologic criteria of soil maturity are in fair harmony as long as soils of equal constellations of cl, o, r, and p are being considered. Uncertainty arises in comparisons of soils of different origins or different climatic regions, for the morphologic and the dynamic criteria may stand in contradistinction to each other.

For each of the 68 soil profiles the leaching factor β was calculated according to methods outlined on page 27. A graphical summary is presented in the form of a frequency diagram in Fig. 35. 2β is shown on the ordinate. The effect of parent material is clearly manifested, especially in the case of limestones versus igneous and metamorphic rocks. 80, respectively. Enhanced leaching due to calcium carbonate is strongly suggested. There are a few low β values within the igneous rock group. They refer to profiles developed on basaltic rocks that are high in calcium, which, as one would expect, behave more like calcareous rocks.