i8 9 i.] 







Relationships of the Archegoniata. 



33i 



ably either these or the Schizaeacese are to be so considered. 

 Isoetcs is even more difficult to place. It is unquestionably 

 the nearest among living pteridophytes to the spermaphytes, 

 but with what group of homosporous ferns it is most nearly 

 related, is hard to say; for while showing evident relationship 

 to several forms, they are in widely separated groups. On 

 the whole, the evidence is in favor of regarding it as nearest 

 the Marattiaceae; but this is liable to be changed when the 

 embryogeny of the latter is known, and the life history of the 

 Ophioglosse2e. (See diagram 2.) 



Marsiliaceae 



Hepaticae. 



Diagram 2, illustrating the ontogeny of the vascular cryptogams and 



spermaphytes. 



The tendency toward the separation of the sexual organs, 

 occasionally found in nearly all forms examined, occurs regu- 



