Fig. 14-32. Diagrammatic representation of intercalary extension in hyphae among enlarging plant cells of the leaf expansion zone. The plant cells increase in size and the attached hyphal strand increases in length accordingly to accommodate the increased distance between the two lateral hyphal branches that penetrate between files of expanding host cells. New compartments are formed along the length of the elongating hyphal strand. Intercalary hyphal growth enables the hyphal branches to remain intact rather than being sheared off the primary filament by upward movement of the host cells.