1	Plants emergent; microphylls 3-4.5 cm, ca. 1 mm wide; megaspores smooth.		5 I. hypsophila
+	Plants submerged or emergent; microphylls longer than (10-)15 cm, 1-10 mm wide; megaspores textured with spines, tubercles, or ridges		(2)
2 (1)	Plants emergent; microphylls 1-2 mm wide; sporangia with white membranous velum cover		(3)
+	Plants submerged or emergent; microphylls 5-10 mm wide; sporangia without velum cover		(4)
3 (2)	Roots without reddish sheathing mantle; cross section of microphylls more circular; microphylls with 3 or more intrastelar canals; lucunae thick-walled; megaspore proximal hemisphere spinulose to spinulose-cristate, distal hemisphere cristate.		1 I. sinensis
+	Roots with reddish sheathing mantle; cross section of microphylls oval; microphylls with 1 intrastelar canal; lucunae thin-walled; megaspore proximal hemisphere cristate, with muri irregularly anastomosing, distal hemisphere cristate-reticulate.		2 I. orientalis
4 (2)	Plants submerged or emergent; microphylls 10-60 cm; megaspore proximal hemisphere rugulate-cristate with muri irregularly anastomosing, distal hemisphere cristate-reticulate.		3 I. yunguiensis
+	Plants emergent; microphylls 7-25 cm; megaspore proximal hemisphere tuberculate, distal hemisphere rugulate with rounded muri irregularly anastomosing.		4 I. taiwanensis