 Cystidia that are located along the edge of the cap ( called cheilocystidia ) are spherical , and 30 – 120 by 20 – 74 µm . The facial cystidia ( called pleurocystidia ) are club @-@ shaped or elongated ellipses , up to 130 – 155 µm in length . The pleurocystidia protrude from the face of the gill and act as guards , preventing adjacent gills from touching each other , and also ensuring that the basidia and spores have sufficient room for development . C. micaceus may also have scattered caulocystidia ( cystidia on the stem ) that are 60 – 100 by 5 – 10 µm , but their presence is variable and cannot reliably be used for identification . Both De Bary and Buller , in their investigations into the structure of the cystidia , concluded that there is a central mass of cytoplasm formed where numerous thin plates of cytoplasm meet at the center of the cell . De Bary believed that the plates were filamentous branching processes , but Buller thought that they were formed in a process similar to the walls of foam bubbles , and that the central mass was able to slowly change form and position by altering the relative volumes of the vacuoles enclosed by the numerous thin cytoplasmic walls . In older cells , the cytoplasm may be limited to the periphery of the cell , with one huge vacuole occupying the cell center . 
