_ Manganese 10% | All as metallic, in the form of hydrated oxides, Copper 10% | and applied at the rate of 4 lbs, for the combination Zinc 5% | material per 100 gallons. Boron 1% _| The addition of 2 lbs. lime is optional. In California a manganese deficiency has been observed on English Walnuts[10], and 5-15 lbs. commercial manganese sulphate was used per 100 gallons of water during late May, through June, to correct this. Sprays should be applied at ten day intervals until the deficiency symptoms no longer persist. Plausible reasons for the somewhat quicker action of sprays than fertilizers may be furnished by two prominent authorities: McCollum[11], one of our foremost nutritionists, first noted the discovery that the leaf of the plant is a complete food, and that none of the storage organs of plants, seeds, tubers, roots, fruits enjoy that distinction. In the leaf, biological processes are most active. It is the site of synthesis of proteins, carbohydrates and fats. The leaf is rich in actively functioning cells which contain everything necessary for the metabolic processes, and they supply all the nutrients which an animal requires. ("All flesh is grass"). Hoagland[12], another authority, writes on this subject thus: "It is now certain that soils are not invariably capable of supplying enough boron, zinc, copper and manganese to maintain healthy growth of plants. This knowledge has come mainly during the past ten years. Within this period thousands of cases from many parts of the world have been reported of crop failure, of plant disease, resulting from deficiencies of micro nutrient elements.... The statements do not imply that most soils are deficient in any of these elements, but the areas involved are large and important enough to warrant the view that the recognition of micro nutrient deficiencies constitutes a development in applied plant nutrition of major significance. "When I refer to deficiencies of boron, copper, manganese, or zinc, it is not a question of absolute deficiency in total quantity of the element present in the soil, but rather a physiological deficiency arising from the insufficient availability of the element in the plant; in other words, not enough of the element can be absorbed and distributed in the plant for its physiological needs at each successive phase of growth." Nutritional sprays under such circumstances may prove the remedy, and we have experimental evidence to support this. Nut trees as is shown by the above mentioned experiment, may respond to spray applications equally as well as citrus, other fruit and vegetables, and effects, too may possess special diagnostic values, showing the need of trees, and therefore also the need of soils on which they are grown.