1. The development of an endosperm without fusion of the *polar nuclei
or *definitive nucleus
with a male gamete. It may arise spontaneously from the definitive nucleus or from somatic tissue and is therefore usually diploid.
2. In gymnosperms, the tissues of the female gametophyte, which nourish the embryo. It is not homologous with the endosperm of angiosperms, being haploid rather than triploid.