428 Bower . — Studies in the Phytogeny of the Filicales. 
It has already been shown that, among the Blechnoid Ferns, transitions 
are common from the more primitive gradate sorus to the * mixed 5 type, 
and that the transition may often be traced in the individual as it passes 
from the young to the mature state. Such facts accord with the experience 
in other phyla, such as the Davallioid and the Cyatheoid Ferns (compare 
Land Flora, pp. 595-600 ; Ann. of Bot., vol. xxvi, p. 316; Davie, Ann. 
of Bot., xxvi, p. 263). 
The transition from a gradate to a mixed sorus is usually accompanied 
by a transition from the oblique to the vertical annulus, and from the com- 
plete to the interrupted ring. This has been seen with special clearness in 
Odoiitosoria and Lindsaya (Ann. of Bot., xxvii, p. 460, PI. XXXIV, Fig. 22). 
Some transitional states might therefore be anticipated in the Blechnoid 
series. It will be remembered that in Plagiogyria a complete oblique 
annulus is present, with lateral dehiscence (Ann. of Bot., vol. xxiv, 
PI. XXXIII, Fig. 1 8, a-d). The same is the case in the Cyatheoid Ferns, 
with which Matteuccia is specially related. In some of these, and especially 
in Cyathea itself, there has been a considerable reduction in size of the 
sporangium. But this is not the case with those of Lophosoria (Ann. of Bot., 
xxvi, PL XXXV, Figs. 18-20), where the sporangium is relatively large, 
with continuous oblique annulus of numerous cells. A comparison of these 
with the sporangia of Matteuccia shows a considerable similarity in size, 
while the annulus is still more complex in the number of its cells. But it 
is only slightly oblique, and is interrupted at the insertion of the stalk 
(Text-fig. 2). The sporangia of Blechnum are again smaller. They appear 
to be of very uniform type throughout the genus, and are adequately 
represented by those of Stenochlaena (Text-fig. 12, a-d). The stalk is 
composed of only three rows of cells ; the annulus also consists of fewer 
cells than in Lophosoria or Matteuccia , and it is only slightly oblique, 
showing complete or sometimes partial interruption at the insertion of the 
stalk. These characters are in fact just such as might be expected in Ferns 
derived from an ancestry with oblique annulus, in which the oblique position 
is no l onger a matter of biological importance. They accord with the general 
hypothesis advanced in this memoir, though they are not so distinctive 
as the facts from the Dicksonia , Lindsaya , and Davallia are seen to be. 
From the above paragraphs it will be apparent that comparisons in 
respect of several distinct criteria lead to similar conclusions, with greater 
or less clearness. They have been based on external form, on dermal 
appendages, on the vascular anatomy, on the characters of the sorus, and 
on the sporangium. The general result has been to indicate a progression 
from a Cyatheoid source, such as is represented by Matteuccia intermedia , 
through the large and varied genus Blechnum , to certain derivative genera, 
culminating in S colop endrium and Asplenium . Not only do the several 
lines of comparison mutually support one another, but also a line of bio- 
