The New Student's Reference Work/Nucleus

Nucleus (nū′ klḗ-ŭs), (in plants), a special protoplasmic body always found in cells.  So far as known, every cell must contain nucleus and cytoplasm.  In the process of ordinary cell division the initial steps are taken by the nucleus.  Ordinarily, the nucleus is a spherical body and is usually centrally placed.  It is difficult to see under ordinary circumstances without the use of special stains which color it.  See Cell.