Sporangia 2–3 (rarely 4), fused into synangia (Fig. 12), 2–6 mm in diam. or length, occurring in the axils of 2-lobed appendages. Sterile lateral appendages either minute and scale-like or leaf-like and 1–4 cm long. Stems simple or dichotomously branched. Rupestral or epiphytic plants Psilotaceae
Sterile lateral appendages 6–31 mm long; the apex mucronate. Synangia composed of 2 sporangia Tmesipteris
Apices of the majority of the sterile lateral appendages on each plant acute or rounded. Synangia rounded. Aerial shoots 5–16.5 cm long including the stems. Sterile lateral appendages almost equally-sided at the base
Apices of sterile lateral appendages truncate or bilobed. Synangia pointed or rounded. Aerial shoots 8.5–86 cm long including the stems. Spores 85–90 µm diam. Sterile lateral appendages not dilated to very much dilated at the base