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| The lower surface color on the lichen lobe above differs from the top surface; the lower surface is whitish, while the upper surface is yellow green. The granular structures along the margins are soredia. | The lower surface here is also white or light brown, but it looks much darker because of the brown tomentum (small hairs) covering the lower surface. |
| Sometimes the color on the undersurface of the lichen thallus is similar to the upper or more exposed surface, but more often the color is different. This character is only useful when identifying foliose lichens, because fruticose and crustose lichens have no definable lower surface. The colors of the lower thallus is quite variable, from tan to black, from white to dark brown. Often the color changes from light to dark from the outer to inner portion. |