Key to the Families of the Fern Allies. 



I. — Sporangia in terminal cones 

 Stems hollow, rush-like 



Equisetacea 



II. — Sporangia in the axils of the leaves or leaf- 

 like bracts, often forming terminal 

 spikes 

 Plants apparently stemless . . Isoeiacece 



Plants with evident stems 



Spores of two sizes . Selaginellacece 



Spores all alike 



Sporangia in spikes . Lycopodiacece 



Sporangia in clusters . Psiloiacece 



111. — Sporangia in berry-like sporocarps 



Whole plant floating . . . Salviniacece 



Plant rooting in mud . . ATarsiliacecE 



