Blunt-leaved pocket moss, or Fissidens obtusifolius, is a member of the Fissidentaceae, a family containing 450 species, all within the genus Fissidens.
Members of the Fissidentaceae are set apart from similar taxa by two determining features. Firstly, they have distichous leaves, meaning that the leaves are arranged in two vertical rows on either side of the stem. Secondly, they have equitant leaves; the bases of the leaves overlap those growing above them. Both of these characteristics can be seen in Robert’s photo, but if your eyes are not eagle-sharp, you might appreciate the magnified image of blunt-leaved pocket moss at the Ohio Moss and Lichen Association website. The ovate to oblong, broadly obtuse leaves have inspired Fissidens obtusifolius‘ species name; these leaves are about 1mm in length and have no teeth.
Fissidens obtusifolius is found in eastern North America on wet limestone and limestone-bearing sandstone. It is almost always found near water, or in the recesses of wet cliff faces. I love that Robert’s photo makes the scale of this species ambiguous. I have the image filling my computer screen, making it look showy and extravagant (for a moss), but in reality this moss is easily-overlooked and reaches a height of only 1 cm. Thanks, Robert, for taking the time to notice the little things!