m down. . TEST YOURSELF Fill in the blanks. (a) A cell is the basic unit of ........... (b) The outer covering of a plant cell is called (c) The jelly-like fluid found between the plasma membrane nucleus is called ........ d) are fluid-filled spaces. e) Plastids are absent in .... cells. Lysosomes are found in .... ...... cells only. en Graded Science and Environment Book 7​