1	"Plants aquatic; fertile leaves with much narrower segments than the sterile leaves (Ceratopteris thalictroides)"	"Ceratopteris {Ceratopteris  thalictroides}"
1	"Plants terrestrial; segments of fertile leaves not much narrower than those of sterile leaves"	2
2	"Leaves fan-shaped, dichotomously branched into linear segments"	Actiniopteris
2	"Leaves not fan-shaped, pinnately divided, often more than once"	3
3	"Sporangia borne on specialized reflexed marginal flaps"	Adiantum
3	"Sporangia borne near the margin and usually covered by it but not borne on specialized flaps"	4
4	"Lower surface of leaf blades covered with a whitish powder"	"Negripteris {Negripteris scioana}"
4	"Lower surace of leaf blades without powder"	5
5	"Leaf blades several times pinnately divided, ultimate segments linear, up to 1.5 mm wide"	Onychium
5	"Leaf blades one or twice pinnately divided, ultimate segments wider than 1.5 mm"	6
6	"Sori interrupted, not more than twice as long as wide"	Cheilanthes
6	"Sori more or less continuous, often more than 5 times as long as wide"	7
7	"Petioles dark brown or black"	Pellaea
7	"Petioles dull brown"	"Pteris {Pteris vittata}"