Fibers complying with these conditions will come into commercial use whenever the increasing costs of wood-pulp reach a figure approximately equal to cost of producing cellulose from any other available source. Up to the present time this has not been brought about, but the steady increase in the cost of wood-pulp is approaching a level with which crop pulps may soon compete. A synopsis of the fibers described in the circular referred to is given below. CORN STALKS.--On account of the enormous supply, corn stalks were first taken up by the Bureau. The yield of stalks per acre is conservatively estimated at one ton, and the annual product is placed as at least 100,000,000 tons, of which not over one-third is believed to be utilized by the farmers. Three products have been derived from the stalks: 1. Long fiber suitable for paper-making, composing 12 to 18 per cent of the bone-dry weight. 2. Pith pulp, suitable for paper specialties, equal to 15 to 30 per cent bone-dry weight. 3. Corn-stalk extract, obtained by lixivaition, and of value as a cattle food, a ton of stalks yielding 200 to 300 pounds of soluble solids. It would require an immense area to supply a mill of moderate capacity, and the question of whether the derivatives of corn stalks could be sufficiently valuable to overcome the costs of harvesting and hauling, has never been answered by any experiment on a commercial scale. BROOM CORN.--Broom corn contains a higher percentage of fibers than corn stalks. In laboratory and semi-commercial tests, fiber yields of 32 to 40 per cent have been obtained with a comparatively low consumption of chemicals. The Bureau claims that results “indicate that this material is suitable for immediate use in paper-making on the basis of quality of fiber produced and yield of fiber secured.” It is estimated that 450,000 tons is the approximate annual crop. Food extracts may also be obtained as well as the fiber. RICE STRAW.--The Chinese and Japanese have for years used rice straw in paper-making, and it is regarded by the Government investigators as one of the most promising crop materials, the annual crop approximating 1,500,000 tons. COTTON-HULL FIBER.--The lint adhering to the cotton hulls, after the long fiber has been removed, may be conserved as a by-product of the cotton-seed oil industry, and this fiber may be reckoned among the possibilities. Cotton stalks also have been the subject of experiment. The yield per acre, however, is not estimated at above 1,000 pounds, so that immense tracts would have to be covered in accumulating any considerable supply, and after the cotton crop has all been picked, negro help is very difficult to obtain.