Eurhynchium praelongum

The peristome teeth are spectacular. The teeth of many mosses in this group are hygroscopic, which means that they change their shape depending on how wet or dry they are. The teeth aid in spore dispersal by flicking the spores farther than they might otherwise go. There are two rows of teeth on this sporangium: the endostome (inner row) and the exostome (outer row). Many mosses have only one row.