The yellows or little-leaf of walnut trees and the rosette of pecan trees, as well as little-leaf of the peach and mottling of apricot and of citrus, are independent of the N requirements, the anion content of the water extract of the soil, climatic factors, cultural and irrigation practices, nematode infestations and soil types, but appear to be dependent on the base relationship in the soil. These tree diseases are "physiological" and not due to infection. The ash of affected leaves is lower in Ca and higher in K than that of healthy leaves of the same age. The percentage of Ca in the ash of the water-soluble fraction of diseased leaves increases as maturity is approached, and finally becomes considerably greater than that of healthy leaves. Nearly all the Ca in the dry matter of healthy walnut leaves is insoluble in water. The sap drawn by suction from diseased walnut branches shows a greater Ca concentration than that from healthy branches. The ash'' content of walnut leaves increases very rapidly at the outset of growth, then shows a slow but progressive increase until maturity is reached, after which there may be a slight decline. By July 1 the ash content of the dry matter is about i that at maturity. Expressed juice of orange leaves is from 3 to 4 times as concentrated in ash content as that of walnut leaves. The percentage of Ca in the ash of expressed juice of orange leaves is about 15 times as great as that of walnut leaves. Practically no differences exist in the ash composition of the expressed juice of healthy and diseased walnut leaves. Expressed juice of diseased walnut leaves has a lower pH value and a greater total acidity than that of healthy walnut leaves.