The part of the seed that develops into a seedling at germination is the embryo.

Here's a breakdown:

* Embryo: This is the tiny, undeveloped plant within the seed. It contains the radicle (future root) and the plumule (future shoot).

* Seed coat: This protective outer layer of the seed.

* Endosperm: This provides food for the developing embryo.

During germination, the embryo uses the stored food in the endosperm to grow. The radicle emerges first, anchoring the seedling in the soil. Then, the plumule grows upward, developing into the shoot with leaves.