376 Bower. — Studies in the Phytogeny of the Filicales. 
covers them is usually and normally formed from it ; at least in the middle 
region of the pinna it is so, though at the basal and apical ends this may be 
departed from. A slightly later stage is seen in Fig. 6 , e , in which it is 
plain, by comparison with Fig. 6,d, that the indusial flap has sprung from 
the marginal cell. Fig. 6,f, which shows a still more advanced stage, with 
the segmentation of the sporangia beginning, indicates again that the 
indusial flap is developmentally the extension of the margin of the pinna. 
It may be noted that there is some evidence of a gradate sequence of origin 
of the sporangia, as shown by this drawing. 
It will be seen from Fig. 5 that the indusial flap, which may be held to 
be the ‘ phyletic margin ’, stops short of the apex and the base of the pinna, 
and that it is there replaced by another distinct margin. Such a condition 
is explained by Fig. 6 ,^*, which was cut from near the base of the pinna. It 
shows the ‘indusial’ flap projecting apparently from the under surface, at 
some distance from the actual margin. A similar condition may be seen in 
sections from near to the apex. Fig. 6 , c , shows a section of a younger 
pinna near to its apex. On the right-hand wing two wedge-shaped cells 
are seen ; one of these is presumably the source of the ‘ indusial ’ flap, 
the other is presumably the margin of the ‘flange’. A somewhat similar 
condition is seen on the opposite wing, though not so clearly. Such 
conditions bring into prominence the question of the true and phyletic 
relation of the ‘ indusial 5 flap to the 1 flange ’ or apparent margin of the 
pinna. This question can only be decided after a wide basis for comparison 
has been established, by examination of various species, both in external 
form and by means of sections. 
Three species from the sub-genus Lomaria have now been described as 
regards the structure and development of the fertile pinna. They have 
been selected as outstanding examples from the sub-genus in respect of 
simplicity ; they show in the form of the maturing pinna, and in the early 
stages of its development, the nearest similarity seen in the genus to what is 
found in the similarly dimorphic genera of Matteuccia and Plagiogyria . 
These are all alike in the absence from the fertile pinna of any distinct 
flange, though in varying degree there are indications of its origin in the 
three species. But substantially the ‘ indusial flap ’ is the recurved leaf- 
margin, as it is in Matteuccia or Plagiogyria. We shall next proceed to 
examine such further species from the sub-genus Lomaria as show a distinct 
‘flange’, apart from the indusial flap, but in which that flange is not a domi- 
nant feature. It will be found, however, that though of small size in these 
species, still it is actually present. The species are — B. attenuatum (Sw.), 
Mett. ; B. V Herminieri (Bory), Mett. ; B. spicant (L.), Wither, and B. capense 
(L.), Schlecht. They will be taken in the order in which they stand in the 
Synopsis Filicum. 
