Seeds lacking endosperm are seen in

Seeds lacking endosperm are seen in the Orchid.
Orchid seeds usually have no endosperm; the seed coat embraces like a balloon the air-filled space between embryo and testa.
The endosperm is a nourishing tissue present in the seed which nourishes the developing embryo. In orchids, seed endosperm is absent because it is used up during the time of seed development.