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(1) In botany, a squamous growth on the outer side of the embryo of many herbs. The epiblast covers the plumule partially or completely. It is well expressed in most bread grains and meadow grasses, for example, rice, Poa, barley, and bamboo. It is absent in millet, sorghum, corn, and canes. The epiblast protects the plumule. During germination it swells greatly, accumulating moisture like a sponge and participating in dehiscence of the caryopsis. The morphological nature of the epiblast is unclear.
(2) In zoology, the outer epithelial layer of the discoblastula, or blastoderm, in scorpions, cephalopods, mollusks, sharks, and bony fishes, as well as in most reptiles, birds, and lower mammals. The epiblast contains ectodermal and mesodermal material. It is isolated from the cells of the internal layer, or hypoblast, by a cavity known as the blastocoel.