Every seed is _provided with food_ to support the germinating plant. Commonly this food is starch. The food may be stored _in the cotyledons_, as in bean, pea, squash; or _outside the cotyledons_, as in castor bean, pine, Indian corn. When the food is outside or around the embryo, it is usually called =endosperm=. [Illustration: FIG. 16.--EXTERNAL PARTS OF BEAN.] =Seed-coats; Markings on Seed.=--The embryo and endosperm are inclosed within a covering made of two or more layers and known as the =seed-coats=. Over the point of the caulicle is a minute hole or a thin place in the coats known as the =micropyle=. This is the point at which the pollen-tube entered the forming ovule and through which the caulicle breaks in germination. The micropyle is shown at _M_ in Fig. 16. The scar where the seed broke from its funiculus (or stalk that attached it to its pod) is named the =hilum=. It occupies a third of the length of the bean in Fig. 16. The hilum and micropyle are always present in seeds, but they are not always close together. In many cases it is difficult to identify the micropyle in the dormant seed, but its location is at once shown by the protruding caulicle as germination begins. Opposite the micropyle in the bean (at the other end of the hilum) is an elevation known as the =raphe=. This is formed by a union of the funiculus, or seed-stalk, with the seed-coats, and through it food was transferred for the development of the seed, but it is now functionless. Seeds differ wonderfully in size, shape, color, and other characteristics. They also vary in longevity. These characteristics are _peculiar to the species or kind_. Some seeds maintain life only a few weeks or even days, whereas others will “keep” for ten or twenty years. In special cases, seeds have retained vitality longer than this limit, but the stories that live seeds, several thousand years old, have been taken from the wrappings of mummies are unfounded. =Germination.=--The embryo is not dead; it is only dormant. _When supplied with moisture, warmth, and oxygen (air), it awakes and grows: this growth is_ =germination=. The embryo lives for a time on the stored food, but gradually the plantlet secures a foothold in the soil and gathers food for itself. _When the plantlet is finally able to shift for itself, germination is complete._ =Early Stages of Seedling.=--The germinating seed first _absorbs water, and swells_. The starchy matters gradually become soluble. The seed-coats are ruptured, the caulicle and plumule emerge. During this process the seed _respires freely, throwing off carbon dioxid_ (CO₂).