Technical Abstract: Plastids in the coenocytic endosperm of young wheat caryopses were mostly in the form of proplastids. During the first week of endosperm development, newly formed cells had plastids that were pleomorphic in shape, while subaleurone cells interior to the meristematic region contained amyloplasts that contained a single size class of starch granules (type A starch granules). The plastids exhibited protrusions that extended a considerable distance through the cytoplasm. Amyloplasts interior to the meristematic region did not exhibit the protrusions at this time. Both subaleurone and central endosperm cells had amyloplasts that exhibited protrusions at 10-12 DAF, with some protrusions containing small starch granules. By 14 DAF, endosperm amyloplasts lacked protrusions and had two sizes of starch; large type A and small type B granules. Amyloplast protrusions were numerous again at 17 DAF in both subaleurone and central endosperm cells and by 21 DAF a third size class of small type C starch granules was present in the cytoplasm. Binary fission typical of plastid division was never observed in wheat endosperm cells. The results suggest that there are three sizes of starch granules produced at specific times during wheat endosperm development.