Developments of the Oophyte in Trichomanes . 299 
may arise apart from, or in connection with, the sorus, and 
in the former case either from the margin or the surface of 
the frond, and the same is the case in the specimens of 
Polystichum. The examples of apospory in Tr. pyxidiferum 
are much less profuse than in Tr. alatum , and are confined, 
so far as my observations go, to the sorus ; but though the 
growth is here less frequent than in the other species, it is 
clear that the phenomenon of apospory does actually occur, 
for by direct vegetative outgrowth filaments are formed, which 
have been observed to bear antheridia. 
That the discovery of new examples of apospory among 
the Ferns was to be anticipated has already been suggested 1 , 
and if one family of Ferns might be thought more likely than 
another to supply such, it would be Hymenophyllaceae . In 
it the characters of the sporophyte and of the oophyte 
are more like one another, as regards structure and the 
circumstances under which they grow, than is the case in 
other families. The frond, like the flattened prothalloid growth, 
is only a single layer of cells in thickness, while both are 
extremely susceptible to changes of dampness of the air, and 
thus it might be reasonably expected that the sporophyte 
might run on directly by vegetative growth into the oophyte: 
more especially is this probable in specimens grown like those at 
Kew, in an atmosphere which is more carefully protected from 
changes of temperature and dampness than can possibly be 
the case in nature. 
We have every reason to regard the oophyte of the 
Filicineae as the more ancient generation of the two : in the 
lowest forms of the series it was probably of littoral habit, 
growing where moisture was easily and constantly accessible, 
while without the presence of fluid water the sexual act in 
these forms could not be performed. Subsequently, by the 
more full development of the sporophyte, which is as a rule 
so constituted as to withstand greater changes of dampness 
and dryness, these lower forms spread to higher and dryer 
1 l.c. p. 322. 
Y 
