measure sizes of cells

• 1. place a Perspex ruler on top of your prepared slide so that it sits above a layer of onion epidermal tissue
• 2) place the ruler and slide back onto the stage of the microscope
• 3) use a medium power objective (totalling x100 magnification)
• 4) adjust the position of the ruler until it lines up with a continuous group of cells across 1mm of the ruler, 1mm = 1000 microns
• 5) count the number of cells across the 1000 microns sample
• 6) calculate the size of a single onion cell in microns using the formula (i = a m) by dividing the number of cells counted by the tissue sampled (1000 microns in this case)
• 7) write the actual length of the cell on the diagram you have drawn