Repeated nuclear division without formation of cell wall and appearance of large central vacuole pushing the newly formed nuclei towards the periphery is observed in ________ endosperm.

In nuclear endosperm development, the primary endosperm nucleus undergoes repeated free nuclear divisions without the formation of cell walls. This results in a multinucleate condition.

Subsequently, a large central vacuole appears in the embryo sac, which pushes the newly formed nuclei towards the periphery. Cell wall formation may or may not occur later.

Cellular endosperm involves cell wall formation immediately after each nuclear division. Helobial endosperm is an intermediate type where the first division is followed by cytokinesis, but subsequent divisions are free nuclear.

Answer: nuclear