Pyrenula punctella

Brown spores are a characteristic of this genus as is their multicelled nature. The whitish septa dividing the cell into four locules can be faintly seen. Although the locules are roundish in the spore to the left, this species usually is characterized by having odd shaped sharp cornered locules 

Occasionally spores become aborted or are not ejected from the cavity. In most cases they shrink and collapse. A few produce visible oily substances, clear or colored, which are useful in their identification.