<P> Cellular endosperm formation - where a cell - wall formation is coincident with nuclear divisions . Coconut meat is cellular endosperm . Acoraceae has cellular endosperm development while other monocots are helobial . </P> <P> Helobial endosperm formation - Where a cell wall is laid down between the first two nuclei, after which one half develops endosperm along the cellular pattern and the other half along the nuclear pattern . </P> <P> The evolutionary origins of double fertilization and endosperm are unclear, attracting researcher attention for over a century . There are the two major hypotheses: </P> <Ul> <Li> The double fertilization initially used to produce two identical, independent embryos ("twins"). Later these embryos acquired different roles, one growing into the mature organism, and another merely supporting it . Thus the early endosperm was probably diploid, like the embryo . Some gymnosperms, such as Ephedra (genus), may produce twin embryos by double fertilization . Either of these two embryos is capable of filling in the seed, but normally only one develops further (the other eventually aborts). Also, most basal angiosperms still contain the four - cell embryo sac and produce diploid endosperms . </Li> <Li> Endosperm is the evolutionary remnant of the actual gametophyte, similar to the complex multicellular gametophytes found in gymnosperms . In this case, acquisition of the additional nucleus from the sperm cell is a later evolutionary step . This nucleus may provide the parental (not only maternal) organism with some control over endosperm development . Becoming triploid or polyploid are later evolutionary steps of this "primary gametophyte". Nonflowering seed plants (conifers, cycads, Ginkgo, Ephedra) form a large homozygous female gametophyte to nourish the embryo within a seed . </Li> </Ul>

Explain the absence of the endosperm in dicots