Plants of the Gila Wilderness

The Grimmiaceae is a diverse family that has traditionally presented problems to many a bryologist. They frequently are darker colored plants that grow on rocks.
Coscinodon is a genus that is characterized by having a calyptra that is as long as the capsule and seems to nearly enclose it.
Schistidium differs from Grimmia in that the columella of the sporophyte (central column of the capsule) falls with the operculum in Schistidium rather than staying with the capsule. In addition, the seta is twisted in Grimmia in the dry state while it is not twisted in Schistidium. A very useful clue to differentiate Grimmia from Schistidium is the undifferentiated costa in cross section in Schistidium-- the cells are mostly homogeneous in size and shape in most cross sections. In Grimmia, there are usually obvious small and thick walled stereids in at least the upper costal cross sections. Here is a pic comparing the costal anatomy of Schistidium and Grimmia (Schistidium rivulare on the left, Grimmia longirostris on the right.)