OIL-PRODUCINO SEEDS. By GILBERT H. HICKS, Assistant, División of Botany, U. S. Department of Agriculture. GENERAL REMARKS. There are over 200 species of plants whose seeds are used in making oil for illumination, medicine, food, soap, and lubricating machinery. A large proportion of these plants are natives of tropical regions, many of which will not thrive in colder climates. On the other hand, there are many plants which could be profitably grown in the United States for the oil contained in their seeds. A few such plants are now cultivated in this country, principally, however, for other pur- poses than the use of their seeds for oil, as in the well-known cases of cotton, peanuts, etc. The object of this article is to collate from reliable sources infor- mation concerning some plants which now are or which might be grown with profit for oil, thus developing a new line of agricultural activity which may in many cases prove profitable. Oils are divided.into three classes: Fatty oils, mineral oils (such as kerosene, benzine, etc.), and volatile, or essential, oils (oil of turpen- tine, camphor, etc.). Oils of the first group are subdivided into those of vegetable and those of animal origin. Of the former, seeds furnish the main supply, although no part of the plant seems to be entirely wanting in fat. That found in the organs of vegetation, however, is more wax-like. The oily matter in seeds is stored up as food to be used by the young plant during the early stages of germination, before it is able to absorb food materials for itself from the earth and air. All seeds store up oil or starch for this purpose. The amount of fat in plants is said to be in nearly an inverse ratio to the amount of starch and sugar which they contain, ranging from ^7 per cent in the brazil nut to only 1 per cent in barley. Oil is obtained from seeds by first crushing and then pressing them in cloth bags, or by boiling them in water and skimming off the oil which rises to the surface, or by using some chemical solvent, such as carbon disulphide, which extracts the oil. The first method is that generally employed, although the chemical process is coming into use to a large extent. Seeds are either pressed cold in mills con- structed especially for that purpose, or heat is used to coagulate any albumen present and to render the oil more liquid. In many 185 186 YEARBOOK OF THE U. S. DEPARTMENT OF AGRICULTURE. instances both cold and warm pressure are used, but in the case of the best medicinal or table oils no heat is employed. The method of using solvents commonly yields a greater amount of oil than does pressure, but is open to objections. The crude oils obtained by pres- sure or extraction are refined by filtering and the use of chemicals. The residue of the seeds after the oil is extracted is called ''oil cake, " and is often of great value as a stock food or fertilizer. It is composed of the woody fiber and mineral matter which the seed con- tained, a small per cent of unextracted oil, and, of more value than all else, the proteid or nitrogenous constituents of the seed. This gives it especial value as food, while the high per cent of phosphoric acid and potash in addition to nitrogen makes it a most valuable fertilizer. The exportation of cotton-seed cake from the United States in 1894 was over 600,000,000 pounds, worth over $7,000,000, while that of ñaxseed amounted to nearly 128,000,000 pounds, valued at $1,700,000. Three-fourths of this material went to Great Britain. FIG. 26.—Cotton (Gossypium barbadense). a, seed, delinted, magnified3 times; &, seed with coma attached; c, transverse section, showing the crumpled embryo filling the seed coats. COTTON-SEED OIL.^ The cotton plant (various species of Gossypium) has been culti- vated from time immemorial, principally for the fiber attached to the seeds. It occurs in Asia, Africa, and tropical America, but is also grown in some parts of Europe, and, as is well known, cotton fiber forms one of the principal products of the Southern States of this country. The black seeds (fig. 26) are almost hidden by a tuft of white fiber which covers their surface. They are irregularly egg-shaped, from 6 to 9 mm. 2 long and 4 to 5 mm. broad. The thick seed coat is filled 1 See Farmers' Bulletin No. 36, U. S. Department of Agriculture. 2 For metric system, see Appendix. Consult index. OIL-PRODUCING SEEDS. 187 witli the coiled embryo, whicli is sprinkled witli brownish resin glands easily seen with the naked eye. The cells composing the embryo are filled with drops of fat and other matter. The seeds contain from 15 to 20 per cent of oil, which for hundreds of years was wasted, for the seeds proper were thrown away after stripping off the fiber. It is only within the present century that they were considered of any value except for planting. In 1826 a Virginian was led to experiment with cotton seed. He made a small machine with which he was able to express a dark- red oil that gave a fair light when burned in an ordinary lamp. In the same year, it is reported, an oil mill was constructed at Columbia, S. C, which expressed a good quality of oil from cotton seed. From this beginning there has arisen a great industry, and although cotton is still grown mainly for the fiber, the seeds are now carefully saved for the oil. Great difficulties were experienced at first in extracting all of the oil contained in the seeds, since in the process of delinting a considerable amount of fiber remained attached to the seed coat, and this greedily absorbed a large per cent of the oil. Machines have been invented, however, for removing almost all the lint as well as the hulls themselves. In Europe the seeds are first pressed cold and then warm, but in America warm pressure is generally used from the first. The crude oil is a thick fluid, of a dirty brown color. By refining it becomes straw colored or nearly colorless. Estimating 2 pounds of seed for every pound of ginned cotton, nearly 4,000,000 tons of seed were produced in the United States in 1894-95. Deducting about one-third of this, required for sowing, there would remain over 2,500,000 tons of seed. Of this amount about 1,500,000 tons were worked at the oil mills, each ton producing 45 gallons of crude cotton-seed oil and 800 pounds of cotton-seed cake. This estimate gives the immense total of 60,000,000 gallons of oil and 600,000 tons of oil cake produced in the United States in a single year. At 30 cents a gallon, this crude oil was worth $18,000,000, while the oil cake exceeds $12,000,000 in value. Of this annual pro- duction of oil about 9,000,000 gallons are used in making "compound lard," while the rest is either exi3orted or mixed with drying oils or used in the manufacture of soap. Cotton-seed oil is also largely used for adulterating olive, lard, sperm, and other oils. During the last two years the exportations of cotton-seed oil from this country have been as follows: In 1892-93, 9,462,074 gallons, valued at $3,927,556; in 1893-94, 14,953,309 gallons, valued at $6,008,405. The principal European country extracting oil from cotton seed is England, the seed being obtained mainly from Egypt, from which country the United Kingdom imported, in 1894, 314,756 tons. Cotton-seed meal makes an excellent fertilizer. In exchanging with farmers, oil mills give 1 ton of meal for 2^ to 2^ tons of seed. The hulls are used for fuel, paper, or feeding like hay. In Russia oil cake is used to some extent for stock food. In America the cake 188 YEARBOOK OF THE U. S. DEPARTMENT OF AGRICULTURE. (ground to meal) is used extensively and with good results as food for cattle and sheep, but has frequently been found poisonous to pigs and calves, especially when it has undergone fermentation. The meal is not infrequently used to adulterate mustard. The prin- cipal States manufacturing cotton-seed oil are Tennessee, Mississippi, Louisiana, Texas, and Arkansas. Further data concerning cotton seed may be found in Farmers' Bulletin No. 36, published by this Department. FLAX. IsText in importance to the cotton seed for oil purposes in the United States is that of the common flax {Linum usitatissimum) ^ which, like the cotton plant, originated in the far East and has been known since the times of Moses and Homer. Flax is an annual, and at present is cultivated in nearly every country of the globe, especially in Russia and India. The seeds (fig. 27) are flattened ^ h elliptical oval, pointed at the lower end, smooth, shining, and of different shades of brown. They are 3 to 4 mm. long, 2 to 3 mm. wide, and about one-half mm. thick. They are produced in a 10-seeded globular capsule, which either remains closed at ma- turity or in some forms opens suddenly, scattering the seeds. Unlike cotton, flax- seed contains beneath the shell a hard layer FIO 27 -Common flax {Linum ^f eudospcrm surrouudiug the cmbrvo. usttahssimum). a, seed, mag- . ^ o j nified 6 times ; 6, longitudinal This layer, howcvcr, is Comparatively thin, section, showing embryo im- ^^^ the oil is derived principally from the bedded m the endosperm.