Results of recent analyses of the mixed fatty acids of various seed-fats from some of the Palme Cruciferae, and Umbelliferae, together with earlier data on other members of these orders and of the Myristiceae, have been compared in detail. In any one of these 4 orders the composition of the fatty acids of the seed-fats is of the same general type, but each order is marked by definite and specific characteristics in the composition of the fatty acids. Thus, the Palmae seed-fats almost always contain 46-50% of combined lauric acid, with minor amounts of caprylic, capric, myristic and palmitic acids, and relatively small proportions of oleic acid; in the Myristiceae seed-fats myristic acid predominates; in cruciferous seeds there is usually 40-50% of combined erucic acid, the remainder consisting of oleic and linoleic acids in varying proportions; and umbelliferous seeds appear to be characterized by the presence of an isomeric form of oleic acid, petroselinic acid (20-75%), which has not yet been observed in the seed-fats of any other order except the closely related Araliaceae. It is inferred that the seed-fats of any given botanical order have certain characteristics of their own and much in common with each other, differing from those of dissimilar orders.