Anatomía compararada de óvulos y semillas de dos especies del género Mammillaria (Cactaceae)

Flowers and fruits in different developmental stages of Mammillaria rhodantha Link & Otto and M. compressa De Candolle were collected to study the ovule and seed ontogeny. Microscopic slides were made by common techniques. The ovules are campylotropous, crassinucellate and bitegmic. The nucellar curvature of M. rhodantha is 130º and its micropylar curvature is 25º. The funiculus nearly surrounds the ovule and has no trichomes. In M. compressa the nucellar curvature is 90º and its micropylar curvature is Oº. The funiculus is long and surrounds the ovule incompletely or not at all. Trichomes are present on the ventral side. The embryo is curved in both species, 40" in M. rhodantha and 8º in M. compressa. The food reserve tissues are: perisperm and endosperm. The seed coat is formed from endotegmen and exotesta.