Light micrograph of a thin section through the lobe of Leptogium saturninum, Saturn skin lichen, showing the upper surface of the lichen lobe with isidiae, the brownish skin, followed by the algal layer with the photosymbiont, a cyanobacterium genus nostoc. Underneath the algal layer internally with loosely interwoven chains of Nostoc and hyphae. Microscopic contrast method: Differential interference contrast. Magnification 580x when printed at 10 centimetres width.