The midvein of a moss leaf, because its not really a vein, is called something else: the costa. Some leaves have a single costa, some have one that is short and double, some lack a costa entirely.


 
Back to the microscope! Another leaf cell question!


Asexual reproductive structures, when they're reliably produced and the key asks about them, can be very helpful in identification.


The plants bear a striking resemblance to the malevolent Simpsons character Sideshow Bob. Crum reports  that this species is "exceedingly common on bark of trees, often in rather dry, brushy, disturbed places, such as roadside, pastures, and edges of woodlots."