all its resources, and devotes them to the building of the seed. When done, the seed itself, the embryo, commonly possesses little substance and serves little use beyond its primary purpose, the reproduction of the plant. But in the coatings and coverings of the seed we find a large and abundant supply of substances, in variety and quantity the rarest and richest stock in the vegetable commonwealth. Indeed, the wrappings of seed-germs constitute the especial provision for the nourishment of the human race. The seeds enveloped with starch and albuminoids, as in the cereal grains, make up "the staff of life" for man. Seeds with oily coatings, including the nuts, present a good supply of fats for food. The seeds with succulent coverings, the fruits, yield a great number of sharply-defined substances, most of which claim the approval of man, and some of which require for their due application the best efforts of the human intellect. Without the grains, the fruits, and the nuts, man would be left to browse with the ox and prey with the wolf.
In this abundant material gathered around the seed-germs, chemistry has achieved more success than elsewhere in the organic world. It is well understood that chemists have no reason to boast of what they can do with the products of living cells. In an analysis of vegetable or animal products, there is always a percentage, and often a large percentage, of unknown matter: It might be named "chemist's dirt;" not "matter out of place," but simply "matter unknown." It has weight, it may have color and consistence, but it responds to no inquiries and yields to no suggestions. Like an open polar sea, it baffles and invites and baffles again. But, with all due reservation for unknown bodies, the condition of organic analysis gives good ground for encouragement. Especially in this material about the seed, the analyst finds numerous compounds of clearly definite chemical character, many of them capable of sure identification and exact separation, even when taken in complex mixtures. Working with some of these compounds, an insight into their chemical structure has been obtained; so that the chemist can bring together the materials and conditions for their production. In the products of the peach, at every autumn's ripening, certain chemical changes occur in the kernel under your hand—changes as well known to science and capable of as exact quantitative statement as the local changes of the planets in the solar system. Forty-four years ago, Liebig and his fellow-workers discovered certain links in those chemical changes, in the products of the almond family, and the discovery was an era in chemical science.
The chemistry of the covered seed is of interest not only for the quality of the compounds found in it, but, quite as much, for the history of these compounds, the chemical changes of seed and fruit-ripening in the plant. These changes differ in their general character from other changes of plant chemistry, coinciding more nearly with the
