1 8 Campbell— Observations on the Development 
eusporangiate Pteridophytes. In all of these it is usually 
completely sunk in the tissue of the prothallium and its 
dehiscence is much the same. The archegonium also in these 
other forms has the short neck of Marattiaceae. From 
a study of these facts the inference may be drawn, that the 
ancestral forms had a relatively massive prothallium with 
the sexual organs upon the upper side, and that they were 
completely sunk below the surface as in Anthoceros and 
Marattia ; further, that the projecting neck of the arche- 
gonium and the peculiar antheridium of the Leptosporangiatae 
are secondary characters correlated with the pecularities in the 
prothallium of these forms. This, of course, implies that the 
filamentous prothallium characteristic of certain species of 
Trichomanes , and found occasionally in other ferns, is a 
secondary and not a primary character. 
In regard to the sporophyte, it will not be necessary to 
repeat what has already been said in a former paper as to 
a comparison of the sporophyte of Anthoceros with that of 
Ophioglossum. One additional point, however, may be 
brought out. At an early stage in the development of the 
embryo of Anthoceros the capsule-wall is separated from the 
central tissue, and by a subsequent division of this outer layer 
of cells, the sporogenous tissue is cut off. That is, the 
archesporium is derived from hypodermal cells exactly as 
is the case in the eusporangiate Pteridophytes, but this does 
not occur elsewhere among the Bryophytes. 
Like the Osmundaceae, the Marattiaceae seem to stand 
near the junction of several divergent lines of development. 
Related on the one hand to the Ophioglosseae, they show 
unmistakable resemblance to the Osmundaceae, and possibly 
to Eqnisetum. It has already been suggested that Isoetes 
also belongs to the same stock, and that through forms like it 
the Angiosperms may have arisen. If this hypothesis should 
prove to be correct, Marattia must be regarded as one of the 
earlier forms in which the single initial cell in the different 
members is being replaced by the group of initial cells found 
in most Angiosperms. 
