Because of the simple geographical dynamics of the state of California,
the state has a very rich moss flora with over 600 species
(as documented by James Shevock,
and at least, 65 genera
comprised of some 257 species have been included in Volume 27, Flora of North
America. Of these many genera of mosses that have been listed by
eFloras.org four genera, Grimmia, Didymodon, Tortula, and Sphagnum
comprise 30% fo the listed moss flora for the state, with one
family of mosses, the Pottiaceae (into which Didymodon and Tortula
are classified), has some 33% of the species found within the listed
flora.

While the northern part of the state is rich in the number of
prominent mosses, the southern part of the state has a diversity of
species occupying microniches and include weed species that can
make their home in the most unexpected of places. One such species is
Bryum argenteum.