Though olives are known and consumed throughout the civilized world, comparatively few persons, aside from those living in the regions of their cultivation, know that olives have to undergo certain treatment before they can be eaten. It is a common practise in olive regions to encourage the visitor to taste the fruit directly from the tree. The fruit, both green and black, looks so fine and tempting, that the disgust on tasting is correspondingly great. It is claimed that some of the older varieties could be eaten without preparation, that they dried naturally, and were sweet like raisins. The olive contains a bitter and acrid substance or substances which must be removed before the olives are edible. It is referred to in most of the literature as a “bitter principle”, and has been called an acid, a tannin, and more recently a glucoside. Cruess has repeated the work of the various investigators, who claimed these different substances, and as a result has come to the conclusion that it is a glucoside, that is, a combination of glucose with another compound. In immature fleshy fruits there is usually an accumulation of acids, tannins, and sometimes starch. As ripening proceeds, carbohydrates and aromatic substances are formed, and the bitter, acrid, or astringent taste disappears. In the olive there is no starch found at any stage of maturity. Glucose has been found in all stages, and is supposed to be the substance from which the oil is formed. The oil is in very minute quantities in the fruit up to the time when the pit is formed, from then on it increases gradually up to its maximum when the fruit is not quite mature. In the plant economy the fat or oil is one of the most important food reserves of plants. All parts of the fruit--rind, flesh, stone, and seed--contain oil, the fleshy part, forming about 80% of the fruit, containing the largest amount. Contrary to the condition existing in most fruits, the bitterness remains through all stages of development in the olive. A substance of glucosidic nature, given the name “oleuropeine”, has been isolated, and found to be of extreme bitterness. This may be the substance or one of the substances which cause the inedibility of the untreated olive. The oil is the most important constituent of the fruit on account of its high food value and its use in the industries. It is used to a large extent in cold countries and also in dry countries where there are few cattle, the oil taking in the various culinary operations, the place of butter and other fats.