KEY TO THE FAMILIES OF THE FERN ALLIES. 



I. Sporangia in terminal cones 



Stems hollow, rush-like . . Equisetacece 



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

 like bracts, often forming terminal 

 spikes 



Plants apparently stemless . . Isoetacece 



Plants with evident stems 



Spores of two sizes . SelaginellacecB 



Spores all alike 



Sporangia in spikes . Lycopodiacece 



Sporangia in clusters . Pstlotacecs 



III. Sporangia in berry-like sporocarps 



Whole plant floating . . . Salviniaccce 



Plant rooting in mud . . . Marsiliaccce 



