444 Bower.—Studies in the Phytogeny of the Fiticales. 
system of Plagiogyria is thus relatively primitive, but with distinct advance 
beyond what is seen in the earliest types; the closest correspondence being 
with Anemia^ which, though it belongs to the primitive Schizaeaceae, is one 
of the most advanced members of that anatomically variable family. 
Turning to the fertile leaf and sorus as seen in Plagiogyria , the general 
habit, with narrow pinnae having their margins reflexed like an indusium 
over the superficial sori, at once suggests the old comparison with Lomaria, 
or stated more generally, with the Pterideae as a whole. But it is to be 
remembered that the same holds, though with less closeness of the parallel, 
for the fertile leaves of Gleichenia § Mertensia ; for though here the 
margins are not thinned off in the membranous fashion of the Pterideae, 
the venation corresponds in point of the absence of fusions with that of 
Plagiogyria. On the other hand, though Lomaria and Pteris habitually 
show fushions of the venation, many of the simpler Pterideae show a com¬ 
plete absence of vein-fusions ; this is conspicuously the case with Crypto- 
gramme and Llavea , genera with which Plagiogyria has been specially 
related by Diels (Engler and Prantl, i, 4, p. 381). 
The superficial sorus of Plagiogyria , so far as the observations here 
recorded are concerned, is restricted to the vein, but extended along it, 
borne on a slightly enlarged receptacle ; it is not unlike what would result 
from an elongation of a sorus of the type of Gleichenia pectinata or dicho- 
toma , or, on the other hand, it may be directly compared with that of 
Cryptogramme or Llavea , to which it corresponds very closely. As regards 
the composition of the sorus, it has been noted that most of its sporangia 
arise simultaneously, as is the case in the Simplices ; but that subsequently 
others are interpolated between those first formed, giving the sorus the 
character of the Mixtae. This character is also shown by Cryptogramme 
and Llavea , but it is worthy of note that it is only arrived at as a late and 
subsequent condition in Plagiogyria. 
It is, however, the character of the sporangium itself which has always 
been held as distinctive for Plagiogyria among those Ferns with which 
on ground of habit it has hitherto been classed. The oblique annulus, 
continuously indurated as it passes the insertion of the sporangial stalk, is 
a feature unknown elsewhere among Ferns having a mixed sorus, with the 
solitary exception of Dipteris conjugata - 1 The usual comparison of 
Plagiogyria on this point has been with those prominent families of the 
Gradatae, the Cyatheaceae, and Dicksoniaceae, which share with Plagio¬ 
gyria the features of lateral dehiscence and small spore-output. But it 
ought to be borne in mind that there is in Plagiogyria no basipetal 
1 The peculiar case of Dipteris conjugata , of which a phyletic explanation was offered by the 
discoverer of the fact of its having a mixed sorus, may be held as an example of the adoption of 
a mixed condition of the sorus by a single species, in a genus having the soral character of the 
Simplices. (See Miss Armour, New Phyt., vol. vi, p. 238.) 
