402 Bower . — Studies in the Phytogeny of the Filicales. 
dimorphism is secondary ; it compares with that in B. Patersoni , and 
a somewhat similar condition is also seen in Doodia caudata. 
The development of the fertile pinna has been followed out in the 
last-named species. It is specially interesting because the terminal lobe of 
the sporophyll frequently shows the fusion-sori on either side of the midrib 
uninterrupted for considerable distances. This may be held as a retention 
in the apical region of the leaf of that state which was characteristic of 
its ancestry, according to the hypothesis above stated. The lateral wing of 
the pinna arises, as usual, with segments from alternate sides of the marginal 
cell. The wing, as in B. brasiliense , attains considerable size before any sign 
of the sorus appears (PI. XXX, Fig. 26, a). A rather broad upgrowth then 
makes its appearance far within the margin ; it gives rise at the marginal 
limit to the indusial flap ( x , Fig. 26, b), while several deep cells lying more 
towards the midrib are the parent-cells of sporangia. These parts come 
rapidly forward (Fig. 26, c, d)> and take the characters respectively of an 
inward-turned indusium, and of sporangia upon a slightly convex receptacle. 
In order of their appearance they show a slight basipetal sequence. Below 
the receptacle runs the vascular commissure, here cut transversely. The 
development of the fertile pinna of Woodwardia rad'icans shows similar 
steps. It will not be necessary to do more than illustrate this by a single 
section (PL XXX, Fig. 27), which shows the very large indusial flap strongly 
curved towards the midrib, covering the receptacle with its slightly basipetal 
sequence of sporangia. Below this runs the commissure. Clearly the two 
genera closely coincide ; but whereas in Woodwardia the assimilating flange 
is broad and flat, in Doodia it is reduced, and its margin reflexed (as in 
W. areolata ), probably in accordance with a xerophytic habit. 
It is well known that in Doodia the parts of the fusion-sorus thus 
isolated do not maintain the regular linear sequence which is so character- 
istic of Woodwardia . Steps leading to the irregularity which they show 
may be seen illustrated in any large series of specimens. Commonly, the 
sori on either side of the midrib form two series, one nearer to, the other 
further from it. In that case their position is alternate, and they may be 
held to be the result of displacement of an originally linear series. But this 
explanation will only account for the simplest cases, and it seems probable 
that an initiation of new sori must have taken place at points previously 
untenanted. Of this there is abundant evidence in other affinities among 
Ferns. 
The rough anatomy of Doodia and Woodwardia has been examined, 
and presents features of interest. As an example of the former genus, 
D. maxima , J. Sm. (= D. blechnoides , Cunning), was taken, as being a larger 
species, in place of the small and possibly reduced D. caudata. A transverse 
section is shown in Text-fig. 15. It is clear that the dictyostele is like that 
of Blechnum , as also the departure of its root-traces and leaf-traces. The 
