the triploid tissue in the seeds of some angiosperms that furnishes food for the embryo —note 1. the hereditary characters of an endosperm may be determined independently from those of the embryo —note 2. the analogous tissue to an endosperm in conifers is haploid female tissue and is referred to as the megagametophyte —see double fertilization, gamete, megagametophyte, polyploid, xenia This definition last updated 07/30/2008