Developments of the Oophyte in Trichomanes . 293 
varied external conditions upon their growth. I would not 
be understood to question the main points of Goebel’s theo- 
retical sketch of the descent of the oophyte in the Hymeno- 
phyllaceae and other Ferns, and their relations to the Mosses, 
as given in the concluding paragraphs of his ‘ Studien ’ ; but the 
detailed application to present forms is to be conducted with 
the greatest reserve. At present, as the result of my own ob- 
servations, it appears to me to be probable that such features 
as the transition from the filamentous to the flattened form 
are due rather to the impress of external conditions under 
which the prothalli are grown than to inherited or ancestral 
characters. 
Thus, while admitting the value of Goebel’s comparative 
study of the conformation of the oophyte as a whole, I can- 
not think that comparison can be safely followed into details 
of the vegetative growth. Before we are in a position to do 
this, and draw phylogenetic conclusions from details of con- 
formation of the vegetative oophyte of the Hymenophyllaceae 
or other Ferns, we require to be better acquainted with the 
prothalli of a larger number of species, to know more of the 
influence which external conditions may exercise upon them, 
and to make very liberal allowance for probable retrogression 
of development 1 . 
Because we may be doubtful as to the use of details of 
vegetative conformation in our comparison, there need be no 
objection to a comparison of a more general nature, based 
upon those characters which are more constant throughout 
the series of observed forms. Thus, the species of Trichomanes 
above described illustrate once more the general filamentous 
tendency of the oophyte in the genus, the resemblance of 
which to the protonema of the Mosses is too striking to 
be overlooked, and it is clear that, as regards the main points, 
the above observations fall in with the outlines of comparison 
of the oophyte as sketched out by Goebel. We may regard 
these filamentous prothalli as illustrating the affinity of the 
Hymenophyllaceae, and especially of the genus Trichomanes > to 
This Goebel admits ( 1 . c. p. 116). 
