Intercalary meristem is present away from apical meristem in primary permanent tissue. It is present at the base of internodes, $e g$, in family-Gramineae or at the base of leaves, $e g$, Pinus or at the base of node, eg, Mentha. Intercalary meristem is responsible for increase in length.
The shoot apical meristem present at the apices of shoot, is self determining and autonomous organizing centre. The primary growth and differentiation of primary tissues is entirely due to this meristem as it continuously divides giving rise to new cells. These are the apical meristems that increase the length of plant but not internodes variability.