An important step, the conversion of the electron microscopic picture into a sketch of the outline remains to be done by hand. As has been mentioned before , is the cell wall in many places perforated by pits . Plasma bridges, so-called plasmodesmata run through them and connect the protoplasts of neighbouring cells. The pits and plasmodesmata can occur in various shapes. Especially striking pits can be found in the different cell types of the vascular tissues, they have already been mentioned .
Examples are the pores in sieve plates or the pit areas in xylem elements.
As we have been seen before, can a number of cell and tissue types be identified by means of light microscopy. But the use of the electron microscope allows a closer examination of the differences between certain cell types.