These have dietary properties very different from the seeds. The contrast between the state of nutrition which can be secured in omnivorous animals with suitable mixtures of leaf and seed, as against mixtures of seeds alone, even in complex combinations, was first pointed out by McCollum, Simmonds and Pitz (23). It has not been found possible to secure satisfactory growth, or prolonged well-being in animals fed exclusively on seeds and seed products. The first leaf which was studied was that of the alfalfa plant, for the reason that the immature leaf in a finely ground form is available as a commercial product known as alfalfa flour.

The dietary properties of mixtures of leaf and seed are well illustrated by a series of nutrition experiments carried out with mixtures of seed 60 per cent and alfalfa leaf 40 per cent. The seeds employed included wheat, maize, rolled oat, rice, pea and navy bean. The degree of success in inducing growth with these simple mixtures of one kind of seed with one kind of leaf is much greater than can ever be secured with even such diets as a combination of wheat, maize, oat, hemp seed and millet seed in equal proportions. The latter mixture can support a fair amount of growth when its inorganic deficiencies are corrected, but without additions of mineral salts almost no growth can be secured. Chart 7 shows typical growth records of animals confined to diets of leaf and seed. Among the seeds studied, the oat kernel is best supplemented by the alfalfa leaf. A simple mixture of 60 per cent rolled oats and 40 per cent alfalfa leaf induces in the rat nearly normal growth to the full adult size. Animals grown on this diet have shown moderate fertility and fair success in the rearing of young. However, they were not nourished in the optimal manner, for they fell considerably below the maximum capacity of well nourished animals in respect to fertility and successful rearing of young.

An examination of the leaves of other plants showed that these can in a general way be classed together as food-stuffs of similar character, since they resemble one another more or less closely, just as the seeds resemble each other in their nutritive properties. From the dietary standpoint the leaf proves to be a very different thing from the seed. The dry leaf usually contains from two to five times as much ash as does the seed, and is always especially rich in just those elements in which the seed is poorest, calcium, phosphorus, sodium and chlorin. It follows that the leaf supplements the inorganic deficiencies of the seed. The leaf contains in most cases much more of the dietary factor fat-soluble A than is found in any seed. The leaf as well as the seed contains protein, and amino-acids (24). The amount varies from 8 per cent of protein (N x 6.25) in such fleshy leaves as cabbage, after drying, to more than 15 per cent in dry alfalfa leaf, and clover leaf, to 30 per cent or more in the dry leaf of the turnip. In most cases, probably not all of the nitrogen in leaves is in the form of compounds which have a nutritive value, but the leaves appear, from the data available, to supplement the proteins of the seeds and to enhance to some extent their value. The leaf supplements all the deficiencies of the seed, but not necessarily in a highly satisfactory manner at all times.