Bower . — Studies in the Phytogeny of the Filicales. 401 
of the separate sori to the several veins, each is covered in by its portion of 
the indusial flap, that is (on the present view) by a portion of the original 
(phyletic) leaf-margin ; while frequently avascular process, projecting on the 
anadromic side, represents a part of the commissure, which is a derivative 
structure. It is thus apparent that the resolution is not simply and directly 
into the original sori, but into fragments of the fusion-sorus, involving 
bodies which did not form part of the primitive sori. 
Woodwardia and Doodia. 
Such disintegration of the fusion-sori as that described is not uncommon 
in the genus, especially in leaves which are half sterile and half fertile. 
Particularly good examples have been seen in B. cartilagineum , as grown 
at Kew (PI. XXIX, Fig. 24). It has also been observed occasionally in 
Sadleria y which is to all intents and purposes a bipinnate Blechnum. But 
it has become stereotyped in the genera Woodwardia and Doodia. There 
are so many published figures showing the relation of the sori of these 
Ferns to the venation that it seems unnecessary to produce new ones. 
It will suffice to quote Mettenius, Fil. Hort. Lips., PI. VI ; Christ’s 
Farnkrauter, Figs. 569-72; and Diels, in Engler u. Prantl, i. 4, Fig. 134. 
Special allusion may be made to the case of Woodwardia areolata , in which 
there is strongly marked dimorphism, though most of the genus are con- 
forming, as in Eu-Blechnum. The broad sterile leaves are plagiotropic, but 
the narrow fertile leaves stand erect, and the disintegrated fusion-sori form 
lines on either side of the midrib. Intermediate conditions have been seen 
between the sterile and fertile pinnae, and from one of these PI. XXIX, Fig. 25, 
has been drawn. It shows the same relations as seen in W. radicans and 
other species, but here the indusial flaps are of small size, arching inwards 
from the loops of the vascular commissure. Further reticulations of the 
veins are to be noted, which give the species its name and indicate 
by their presence a character more advanced than others of the genus. 
The hypothetical position as regards Woodwardia and Doodia is this. 
That these genera were derived from a Blechnoid source, by partition of 
the fusion-sorus into isolated portions. Each of these corresponds to a loop 
of the commissure. In that case the indusial flap will correspond to a part 
of the phyletic leaf-margin, and the broad assimilating ‘flange’ with its 
venation will be the correlative of the similar ‘flange’ seen in the more 
advanced types of Blechnum. Further, in the case of W. radicans , and 
other relatively primitive Woodwardias with free venation, there is no 
dimorphism of leaves, their condition being as in Eu-Blechnum> from which 
the genus was probably derived. But in the reticulate, and thus probably 
derivative W. areolata , a dimorphism has again been assumed ; the erect 
fertile leaves have their reduced assimilating flange reflexed for purposes of 
protection of the sori. There seems good reason to believe that this 
