Members of the genus Spartina are dominant macrophytes in many salt marshes of North and South America, Europe, and Africa. Although the genus is of great ecological importance, seeds and seedlings of its 16 species have not been described. The seed and seedling of an American species, Spartina alterniflora, are described. The embryo is enclosed in a lemma, a palea, and two glumes. Vascularization of the embryo is panicoid. After germination, leaves arise by periclinal division of cells of the first tunica layer. Laminae assume the adult form by growth of ribs and formation of furrows on the adaxial surface. The panicoid anatomy of each furrow contains a vascular bundle surrounded by a mestome sheath and large, nucleated, parenchyma (Kranz) cells.