Osmunda claytoniana , Z., and O. cinnamomea , L. 85 
developed archegonial cushion and the dehiscence of the 
antheridia. 
As has already been pointed out in a former paper 1 , the cor- 
respondence in the development of the prothallium of ferns, 
especially the Osmundaceae, with the thallus of many Hepa- 
ticae, is too obvious to be overlooked. If the sexual organs 
of the two groups are compared, we find here, too, that the 
correspondences are greatest in the Osmundaceae. The anthe- 
ridia are larger than in any of the Leptosporangiatae, and 
often distinctly stalked, and their method of dehiscence is 
more like that of the liverworts. The somewhat simpler 
form of the spermatozoids may be cited also, especially when 
contrasted with the many coiled spermatozoids of such spe- 
cialized forms of Marsilia . 
The straight neck of the archegonium, while also probably 
a primitive structure, cannot be certainly considered as such, 
since the curved neck of the archegonium, found in most 
other ferns, is also found in certain liverworts, e.g. Asterella , 
where this condition is obviously due to the conditions under 
which fertilization is effected. 
The occasional presence of a division-wall in the neck-canal- 
cell, however, is in all probability a character inherited from 
an ancestral form, in which, as in all Bryophytes, the neck- 
canal-cell is regularly divided by transverse walls. Of the 
other Pteridophytes the Marattiaceae and some species of 
Lycopodium show the same thing. 
Several peculiarities in the embryo also indicate the primitive 
nature of the Osmundaceae. The large size of the foot, and 
the consequent long dependence of the embryo upon the 
prothallium, and the late differentiation of the organs and 
tissue-systems, are all evidences of this. Accompanying this 
is the very large calyptra. 
We have seen that the root of the embryo has a single 
tetrahedral cell, as in all the other Filicineae except the 
Marattiaceae and Isoetes , if we regard the latter as belonging 
1 Campbell, On the Affinities of the Filicineae; Bot. Gazette, Jan. 1890. 
