Oxford has a semi-decent grasp of the English language. In their ever precise British tone, they provide the following as a definition for embryo:
Embryo: 1 an unborn or unhatched offspring in the process of development, especially an unborn human in the first eight weeks from conception. Compare with FETUS. 2 the part of a seed which develops into a new plant.It appears that everyone can find a dictionary that agrees with them.