Bower —Studies in the Phytogeny of the Filicales. 385 
Diels (Nat. Pflanzen-Fam. i. 4, p. 247), Christ (Farnkrauter, p. 183), and by 
Christensen (Index Filic., p. 161). 
The two distinct conditions coexisting in what is otherwise a uniform 
species illustrates again the instability of development of the ‘ flange ’. 
But the question which of these states is the more primitive must be left 
open. It cannot be rightly assumed a priori that in the Lomaria type the 
lamina is reduced (‘stark in der Spreite reducirt ’, Diels, 1 . c.). A decision 
on this point can only be based on grounds of broad comparative and 
physiological consideration. The question will be taken up later. 
Sadler ia cyatheoides , Klf. 
This Fern is maintained as the type of a substantive genus, though in 
many respects it is very closely allied to Blechnum . It is subdendroid in its 
habit, and a distinguishing mark is the double pinnation of its leaves. But 
as B. Fraseri and volubile both show a 
similar condition, this cannot be held 
as a very valid generic distinction. The 
specific name points a comparison with 
the Cyatheaceous habit ; a similarity 
there exists which may be accepted as 
having more than a mere external 
significance. 
The pinnules of the fertile leaf have 
a distinct Blechnoid character. One of 
them is represented whole in Text-fig. 6 , 
as viewed from below. The venation 
springs wholly from a single strand given 
off from the midrib of the pinna, and its 
branching is like that of Blechnum. On 
either side of the midrib runs the sorus, with a vascular commissure, and 
‘indusia’ arching towards the midrib. Transverse sections show that the 
relations are the same as those in Blechnum , while there are indications of 
a basipetal sequence of origin of the sporangia, but this does not appear to 
be strictly maintained. I owe the supply of material of this Fern to the 
kindness of Professor Campbell of Stanford University. 
Text-fig. 6. Sadleria cyatheoides , Klf. 
A pinnule, showing the venation and its 
relation to the fusion-sori. x 3. 
Comparative Conclusions on the typical Fusion-Sorus and ‘ Flange ’ 
in Blechnum. 
The reader who has carefully followed the details described in the 
foregoing pages will have already perceived the morphological progression 
which they indicate. The description started from a type of Fern with 
dimorphic leaves and superficial sori, which were protected by a simple 
curling downwards of the leaf-margin, and its development as a thin, even 
