Fig. 6.3-1a and b. Longitudinal section of a shoot tip of a fern (Nephrolepis). Ferns have a shoot apical meristem that contains a prominent single apical cell (arrow), which is visible here as the uppermost, central cell at the tip of the shoot. Notice that there are two cells on either side of the apical cell, and another cell below it (mostly distinguishable because their nuclei are visible). The three cells plus the apical cell altogether make up a pyramidal complex that has the outline of an apical cell, and that is because the surrounding cells were recently parts of the apical cell, and became cells during the last few divisions of the apical cell. Below the apex is a column of lightly-stained cells that will develop into pith, surrounded by dark red cells that will become cortex. The rows of cells projecting upward are trichomes.
Figure b is a high magnification view of the apex of Nephrolepis. The apical cell (AC) is the triangular cell. It seems somewhat small, perhaps because it has just finished a cell division or perhaps because the section is passing through one of the narrow parts of its pyramidal shape. To its right is a large square cell (arrow) with a prominent nucleus, and below that cell is an inconspicuous cell about the same size (arrow). Those two cells are sister cells, produced by the transverse division of a long narrow cell that had been cut off from the side of the apical cell. Soon, the apical cell will cut off another long narrow cell along its left side, and then that cell will divide into two progeny cells by a transverse wall, creating a stack of two cells similar to the stack that already occurs on the right side.
Note the dividing nucleus near the bottom of the micrograph.