Developments of the Oophyte in Trichomanes . 295 
striking fact that in both, though they differ so materially 
in details, there is great plasticity of conformation of the pro- 
thallus in the single species, as well as in different species of the 
genus ; in both there is a filamentous tendency, and in both 
special organs of vegetative development of the oophyte are 
found. Since the question whether the differences of the 
oophyte, when the sporophyte shows greater constancy, be 
truly ancestral characters, or merely the result of comparatively 
recent special adaptation, affects both families, it deserves the 
greater attention. In view of the variability even in the single 
individual, and the want of constancy of succession of the various 
phases of development, I am inclined, at least in the case of 
Trichomanes , to the opinion above expressed, that the details 
of conformation of the vegetative thallus in this genus are 
not to be regarded as trustworthy genealogical data. 
Passing on to the details of the oophyte in the species 
above described, the protonemal filaments are coarser than 
those of the Mosses, the septa transverse and the branching 
not perfectly regular, though in the majority of cases each cell 
produces a lateral outgrowth, which may develop as a new 
protonemal branch, a flattened expansion, or a rhizoid. When 
in T. alatnm the protonemal filament widens out into a 
flattened expansion, the septa correspond at first in position 
to those of the original filament, though curved in accordance 
with the law of rectangular intersection ; in some cases, how- 
ever (Fig. 37), there are indications of the presence of a wedge- 
shaped apical cell, as in the Polypodiaceae, and this is worthy 
of note, since the figures of Mettenius, Cramer, and Goebel do 
not indicate such a structure in this genus ; traces of it are to 
be found in the prothalli of Hymenophylhim described by 
Goebel. 
Vegetative propagation of the oophyte, though apparently 
uncommon or even absent in Tr. pyxidiferum , is profusely 
present in Tr. alatum. The results obtained on the latter 
species place it beyond reasonable doubt that the obser- 
vations of Cramer on spindle-shaped gemmae related actually 
to a species of Trichomanes. Not only do his figures and 
