Isothecium alopecuroides new to North America [Musci]

The genus Isothecium is represented in North America by three species: I. cristatum (Hampe) Robins., I. stoloniferum Brid. and, reported for the first time in North America from Newfoundland and Ontario, I. alopecuroides (Dubois) Isov. Isothecium alopecuroides is distinguished from I. cristatum by the restriction of quadrate cells to the alar region of the leaves, and from I. stoloniferum by the presence of leaf margins that are inflexed above the middle, entire below and denticulate near the apex.