A rust fungus Cronartium quercuum produces galls and another rust fungus Peridermium yamabense, a pine-to-pine stem rust of white pines, produces fusiform swellings. Those rust cankers were sectioned into 15 ㎛ using cellophane tape as support and stained with saffranin and fast green. Under the light microscope, rust galls by C. quercuum are made by increasing numbers and diameter of tracheids. On the contrary, rust swellings of P. yamabense are produced by hyperplasia of cortical parenchyma cells. These results suggested that the hormonal activities are different between those twe rust fungi on cambium as a border line. For instance, the activity inward by C. quercuurn and outward by P. yamaberzse might present.