Fluorescence micrograph of a fragment of the dorsal part of the thalloid liverwort Blasia pusilla. The red area is a Nostoc sp. cyanobacteria colony embedded in the liverwort thallus tissue. The presence of symbiotic cyanobacteria is a characteristic feature for Blasi sp. liverworts. The golden colour of the liverwort cells is due to the fluorescence of the stain berberine. The red colour of the cyanobacteria is due to chlorophyll autofluorescence. Observed in ultraviolet (UV) light. Magnification: x166 when printed at 10 x 10 cm.