Again, the question as to whether the storage of energy-producing materials for the use of the next generation shall be in the form of carbohydrates or of fats seems to be definitely connected with the size of the seed, and the consequent available storage space (see page 138). Animals habitually use the space-conserving form of fats for their energy-storage, while plants more commonly use carbohydrates for this purpose, except in the case of those small seeds in which sufficient energy cannot be stored in carbohydrate form to develop the young seedling to the point where it can manufacture its own food. As a general rule, nuts, which contain the embryo of slow-growing seedlings, and need large proportions of energy reserve, are characteristically _oily_ instead of _starchy_ in type. But, aside from temperature reactions and space requirements, there is no law which has yet been discovered which determines the character of the energy-storage compound which any given species of plant will elaborate. The process of photosynthesis would seem to be identical in all cases, at least up to the point of the production of the first hexose sugar; but the transformation of glucose into other monosaccharides, disaccharides, and polysaccharides seems to be a matter which obeys no rule or law. Finally, there remains to be considered the occurrence and uses of sugars in the fleshy tissues of fruits. These tissues have, of course, no direct function in the life history of the plant. They surround the seed, but they must decay or be destroyed before the seed can come into the proper environment for germination and growth. In most fruits, starch is the form in which the carbohydrate material is first deposited in the green tissue, but as the fruit ripens the starch rapidly changes into sugars, with the result that the fruit takes on a flavor which makes it much more attractive as a food for men and animals. This purely biological significance of the presence of sugars (and of the other substances which give desirable flavors to fruits, vegetables, etc.), can have no possible relation to the physiological needs of the individual plant, however. It is apparent that the production of these immense stores of reserve food by plants makes them useful as food for animals, and it is, of course, the storage parts of the plants which are most useful for this purpose. This biological relationship needs no further emphasis. REFERENCES ABDERHALDEN, E.--"Biochemisches Handlexikon, Band 2 ... Die Einfachen Zuckerarten, Inuline, Cellulosen, ...," 729 pages, Berlin, 1911, and "Band 8--1 Ergänzungsband (same title as Band 2)--" 507 pages; Berlin, 1914. ARMSTRONG, E. F.--"The Simple Carbohydrates and Glucosides," 233 pages. _Monographs_ on Biochemistry, London, 1919 (3d ed.). FISCHER, E.--"Untersuchung ueber Kohlenhydrate und Fermente, 1884-1908," 912 pages, Berlin, 1909.