1	Leaf-lobes with denticulate to coarsely dentate margins	Sect. Microfrullania: Frullania chevalieri, Frullania microscopica, Frullania parhamii [incl. New Zealand, New Caledonia, and Fiji]
–	Leaf-lobes with entire margins, lacking any form of marginal dentition	2
2	Stylus a distinct, obovate to subrectangular in shape with a truncate apex; a distinctive angular projection on the lobule immediately above the slit; plants small (c. 250–500 µm)	Frullania truncatistyla[North Island, South Island, Stewart Island]
–	Styli sickle-shaped, subtriangular to triangular; distinctive angular projection absent (not to be confused with the ± discoloured, gibbous, cell above mouth); plants small to medium	3
3	Dioecious, gynoecia terminal on leading stems with subfloral systems (i.e., subfloral innovations or subfloral branches); stylus small to medium, 0.25–0.5× the length of the lobule), typically stylus with up to 10–35 cells	4
–	Monoecious, gynoecia on short lateral branches lacking subfloral systems; stylus typically large, 0.75–1.0× the length of the lobule, stylus with up to 100 cells total	Frullania magellanica [Chile]
4	Lobules typically at an angle in relation to the stem, leaf-lobe median cells smaller than basal cells and with 3–4 oil bodies per cell, occupying <50% of the area of the cell lumen; perianth typically 3-keeled	Frullania rostrata s. l. [Australasia]
–	Lobuli varied, typically subparallel to the stem; a band (pseudovitta) of median cells (of leaf-lobe) as large as basal cells and with 1–2 oil bodies per cell, occupying almost entire cell lumen (where known); perianth plicate 5–6 keeled	5
5	Leaf lobes often squarrose;main stem underleaves small, ± as wide as stem;leaf lobuleclavate,cell walls distinctly flexuose toward the lobule apex	Frullania pseudomeyeniana [New Caledonia]
–	Leaf lobes flat, not squarrose;main stem underleaves medium to large, wider than stem;leaf lobulecylindrically helmet-shaped, cell walls becoming distinctly semi-straight toward lobule apex	Frullania knightbridgei [Stewart Island, Auckland Island]