The stoma on the left is also cut parallel to the guard cell, but the section is almost at the pore – it has just grazed a guard cell ledge, so the stoma appears to be blocked. Notice how small the two guard cells appear to be: those are actually the two ends of the same cell – the cell is crescent shaped and the section has just barely caught the two ends. If the section were a little deeper into the guard cell, it would look like the one on the right. |