Fig. 10.3-8. Magnification of fig leaf stoma. This micrograph shows you a common artifact: the stoma appears to have a very wide stomatal pore. In fact, this pore is too wide for the guard cells to be able to close it, no matter how much they shrink. But this view reflects an error rather than the reality of what the stoma was like on the plant: between the time the section was cut and when it was glued onto the microscope slide, it expanded, and the guard cell on one side of the pore was pulled far away from the guard cell on the other side. This width is so extraordinary that it arouses our suspicion, but if it had pulled only slightly apart, we might not have suspected an artifact. Even in sections that appear to be perfect, it would be risky to try to measure the width of the pore we could never be certain we were not measuring artifacts.