404 Bower.- — Studies in the Phytogeny of the Filicales. 
an anatomical advance on Blechnum , a point to be placed in relation to the 
more advanced condition of its fertile pinna. 
The facts thus appear to indicate that Woodwardia and Doodia are 
Blechnoid derivatives, in which the fusion-sorus has been disintegrated, 
while in Doodia a displacement of the separate portions has also occurred. 
But the displacement thus seen in Doodia is a relatively minor matter 
compared with those displacements which are next to be considered. These 
are associated with bold curvatures of the Blechnoid fusion-sorus, accom- 
panied by its disintegration, as before, into detached portions. Their study 
will begin from typical species of Blechnum , and the modifications there 
seen will form the basis for comparisons, leading on to those states which 
are characteristic of Scolopendrium and Asplenium. 
The comparison may start from Blechnum fraxineumPNWXd. B. longi- 
folium , H. B. K.), a commonly cultivated species, with rather simple leathery 
leaves bearing relatively few pinnae. It belongs to Eu-Blechnum , and the 
character of the normal pinnae is shown in PI. XXIX, Fig. 20, d } as regards 
venation and sori. In this there is nothing calling for special remark. But 
the interest centres round those points where the pinnae are attached, and 
especially those pinnae which appear successively smaller as the large terminal 
segment is approached. This region of a normal leaf is represented in 
Fig. 20, e, which shows the basal part of a large terminal lobe, together 
with the bases of the two next lower pinnae. Here are plainly conditions 
of the sori and of the venation which represent additional pinnae not fully 
formed. Possibly it is a species whose relatively simple leaf-structure is 
the consequence of reduction from a more fully pinnate ancestry, and the 
outward archings or diverticula of the sori may be recognized as partial 
pinnae (Fig. 20, i-vi). It is important to note that each of these archings 
arises opposite to the departure of a lateral vein from the midrib, while the 
main strand of it forms a midrib in cases where the arch is large ; clearly 
this is of the nature of a stunted pinna. 
It has already been noted that the venation of the pinna and the 
vascular supply to the receptacles, though intimately connected, constitute 
two systems. Their behaviour in these stunted pinnae illustrates this. At 
the apex of the arch (iii) in Fig. 20, e, where the interruption of the sorus 
and indusium is not fully carried out, as it is at (iv), a disposition of the 
vascular tissue is seen which gives some insight into the behaviour of the 
storage-xylem. Fig. 20,/, shows it on a larger scale. The indusial flap is 
not actually interrupted, but the series of sporangia ceases at the apex of 
the curve. The veins which run nearer the upper surface of the leaf are 
shaded relatively lightly, and constitute a connected system. But what 
this transparent preparation brings out prominently is, that the xylem of 
the receptacle consists of short storage tracheides, distinct in form from the 
