Acala upland cotton grown in sand beds supplied with nutrient solutions containing: trace, 1, 5, 10, 15, and 25 p.p.m. of B has shown the highest B requirement of some 60 plants with which it has been compared. In 1930, 3, 22, 28, 37, 23, and 21 bolls were produced by 4 plants in the respective concentrations, with similar results both for Pima Egyptian and Acala upland cotton in 1929. B concentrations in the leaves (dry wts.) were respectively 16, 187, 306, 522, 833, and 1625 p.p.m., and in the combined stems and roots 15, 24, 32, 33, 48, and 60 p.p.m. Gratify- ing results might, therefore, follow experimental application of B as a fertilizer for cotton. At B concentrations optimum for cotton, the growth of corn, other cereals, and beans is reduced about 25%, but alfalfa, Melilotus, Windsor beans, and vetch are not materially affected. Only a part of the B added to a soil remains in solution. An acre of cotton plants like those of the 10 p.p.m. culture bed would contain 5.2 pounds of anhydrous sodium borate.