from Key to Frullania species in North America

1. Ventral leaves 2-fid.
2. Plants without caducous leaves.
3. Dorsal lobes lacking ocelli or ocelli inconspicuous.
4. Inflated lobule erect or obliquely spreading, contiguous or approximate with stem, separated by a distance that is less than or nearly equal to its width [as opposed to being more distant]
5. Proximal lobule portion not noticeably expanded
6. Inflated lobule cylindric or sac-shaped, about two or more times longer than wide [as opposed to being cap-shaped]
7. Ventral leaf margins plane, slightly recurved or contorted. [as opposed to being reflexed]
8. Dorsal lobe bases truncate [as opposed to being cordate]
9. Lobules separated from the stem by a distance that is less than or nearly equal to its width [as opposed to being superimposed with stem in F. kunzei]

From FNA key to Lejeuneaceae:

1. Plants with underleaves
2. Underleaves 2-lobed

Key to plants with 2-lobed underleaves

1. Underleaves half as many as lateral leaves
2. Lateral leaf lobes without ocelli
3. Plants yellow-geeen, smaller oil cells

Key to Lejeunea

1. Lobule never saccate, reduced to a small basal fold bearing a linear to lanceolate stylus 1--3 cells wide, 5--12 cells long.
2. Lobule tooth small, 1 cell wide, 2--12 cells long; underleaves distant, small