A primary meristem produces primary
growth at the apical shoot and root tip. 

Cells found here tend to be relatively
non-specialized and have a box-like appearance.  

Primary meristems often have a lot of growing and or dividing cells.  Many cells in the primary meristem are involved in mitosis. 

The primary meristem is responsible for the lengthening of root tissue.

The secondary meristem is involved in the thickening of the plant. 

There are two kinds of secondary meristem: 
cork cambrium and vascular cambrium.
·Cork cambrium cells are responsible for laying down the bark.
·Vascular cambrium cells lay down secondary xylem and phloem.