<P> Ancestral flowering plants have seeds with small embryos and abundant endosperm, and the evolutionary development of flowering plants tends to show a trend towards plants with mature seeds with little or no endosperm . In more derived flowering plants the embryo occupies most of the seed and the endosperm is non developed or consumed before the seed matures . </P> <P> Endosperm is formed when the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte (sometimes called the embryo sac). One sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell (its nucleus is often called the triple fusion nucleus). That cell created in the process of double fertilization develops into the endosperm . Because it is formed by a separate fertilization, the endosperm constitutes an organism separate from the growing embryo . </P> <P> About 70% of angiosperm species have endosperm cells that are polyploid . These are typically triploid (containing three sets of chromosomes), but can vary widely from diploid (2n) to 15n . </P> <P> One species of flowering plant, Nuphar polysepala, has been shown to have endosperm that is diploid, resulting from the fusion of a pollen nucleus with one, rather than two, maternal nuclei . The same is supposed for some other basal angiosperms . It is believed that early in the development of angiosperm lineages, there was a duplication in this mode of reproduction, producing seven - celled / eight - nucleate female gametophytes, and triploid endosperms with a 2: 1 maternal to paternal genome ratio . </P>

Endosperm tissue of angiosperms has what ploidy level
find me the text answering this question