Light micrograph of a thin section through the lobe of Leptogium saturninum, Saturn skin lichen, showing the red auto fluorescence of the algal symbiotic cells of genus Nostoc and the blue auto fluorescence of the fungi hyphens. One isidium on the upper side of the lobe with Nostoc cells. Microscopic contrast method: Fluorescence contrast, UV excitation. Magnification 580x when printed at 10 centimetres width.