Osmund a claytoniana , Z., and O. cinnamomea , Z. 89 
Filicineae. The end-branches of this series are seen in the 
heterosporous Marsiliaceae and Salviniaceae. Of the homo- 
sporous forms, the Gleicheniaceae connect the Osmundaceae 
with the Cyatheaceae and Polypodiaceae. The Schizaeaceae 
probably form a distinct branch, as do the Hymenophyllaceae. 
The last probably originated early in the development of the 
series, and their peculiarities are probably due to the nature 
of their environment. 
Whether or not the Lycopodineae form a branch of the 
original pteridophyte stock, or whether they have an entirely 
distinct origin directly from the Bryophytes, must remain for 
the present an open question. 
The relationships of the groups assumed here may be 
graphically represented by the accompanying diagram : 
Marsiliaceae 
