Scouleria aquatica Hook.

Stem leaves ligulate to lanceolate, (2.8-)3-5 × 0.8-2.5 mm, margins 1-stratose or partially (rarely fully) 2-stratose, serrate distally; basal laminal cells isodiametric to shortly rectangular or juxtacostal cells linear to long-rectangular, 15-36 × 10-12 µm; medial and distal laminal cells 10-25 µm; marginal laminal cells similar to the medial or appearing differentiated, darker and walls thicker, 1-stratose to partially to nearly entirely 2-stratose. Peristome present.