Abstract
In a recent paper, Cain and Friesner (3) found that there was a relation between topography and the hydrogen-ion concentration of the soil. This work was done on certain hills in the Sycamore creek region, Morgan county, Indiana, where it was found that the acidity was greater on the hilltops and less in the intervening ravines, so that curves representing the degree of acidity of the soil at different points on a line crossing the hills were roughly parallel with the topography. The average acidity on three ridge tops was pH 5.3, while the adjacent ravine bottoms were practically neutral, averaging pH 6.9. The consistently greater acidity of the ridge tops and upper slopes seems to play a significant part in the distribution of certain plants found only in such situations, viz., Vaccinium vacillans, Gaylussacia baccata, Polytrichum juniperinum, etc. Since these ridges studied in the Sycamore creek region were only about one hundred feet high, it was thought desirable to investigate some river hills which rise about 250 feet above their immediate bases.
