=662. Presence or absence of endosperm in the seed.=—In many of the angiosperms all of the endosperm is consumed by the embryo during its growth in the formation of the seed. This is the case in the rose family, crucifers, composites, willows, oaks, legumes, etc., as in the acorn, the bean, pea and others. In some, as in the bean, a large part of the nutrient substance passing from the endosperm into the embryo is stored in the cotyledons for use during germination. In other plants the endosperm is not all consumed by the time the seed is mature. Examples of this kind are found in the buttercup family, the violet, lily, palm, jack-in-the-pulpit, etc. Here the remaining endosperm in the seed is used as food by the embryo during germination. [Illustration: Fig. 397. Section of one end of ovule of trillium, showing young embryo in endosperm.] [Illustration: Fig. 398. Embryo enlarged.] [Illustration: Fig. 399. Seed of violet, external view, and section. The section shows the embryo lying in the endosperm.] [Illustration: Fig. 400. Section of fruit of pepper (Piper nigrum), showing small embryo lying in a small quantity of whitish endosperm at one end, the perisperm occupying the larger part of the interior, surrounded by pericarp.] =663. Outer parts of the seed.=—While the embryo is forming within the ovule and the growth of the endosperm is taking place, where this is formed, other correlated changes occur in the outer parts of the ovule, and often in adjacent parts of the flower. These unite in making the “seed,” or the “fruit.” Especially in connection with the formation of the seed a new growth of the outer coat, or integument, of the ovule occurs, forming the outer coat of the seed, known as the _testa_, while the inner integument is absorbed. In some cases the inner integument of the ovule also forms a new growth, making an inner coat of the seed (rosaceæ). In still other cases neither of the integuments develops into a testa, and the embryo sac lies in contact with the wall of the ovary. Again an additional envelope grows up around the seed; an example of this is found in the case of the red berries of the “yew” (taxus), the red outer coat being an extra growth, called an _aril_. In the willow and the milkweed an aril is developed in the form of a tuft of hairs. (In the willow it is an outgrowth of the funicle, = stalk of the ovule, and is called a funicular aril; while in the milkweed it is an outgrowth of the micropyle, = the open end of the ovule, and is called a micropylar aril.)