Embryology of Nemacladus interior (Munz) Robbins
Nemacladus Interior has an eight-nucleate, Polygonum type of embryo sac which forms a haustorial process at its chalazal end. This process invades and crushes part of the chalazal tissues of the integument. Fertilization takes place within twenty-four hours after pollination. All nuclei except the zygote nucleus and the primary endosperm nucleus break down before or immediately after fertilization. During embryo sac development, an endothelium is differentiated around it. This endothelium forms a protective layer outside the endosperm in the mature seen. The endosperm is cellular from the beginning. I^s development is characterized by a transverse division of the primary endosperm nucleus followed by a longitudinal division in the primary micropylar chamber and a transverse division in the primary chalazal chamber. The mature endosperm cells have thick walls and contain oi1. Two endosperm haustoria are formed—a large two-celled micropylar haustoria and a small, single-celled chalazal haustorium. The zygote elongates during early stages of endosperm development but does not divide at this time. The development of the embryo generally follows the Solenad type.