370 Bower. — Studies in the Phytogeny of the Filicales. 
Lophosoria. But, on the other hand, it is now more evident than before 
that the relationship upwards between Matteuccia ( Struthiopteris ) and the 
genus Blechnum , so clearly recognized by the early systematists, has the 
support of more detailed comparison than they had instituted. The new 
facts appear to suggest that the Blechnoids probably sprang from some 
early Cyatheoid source, and the nearest indication of the connexion is seen 
in the Fern so happily named by Christensen, Matteuccia intermedia. With 
this general indication, which coincides with the opinions of early sytematists, 
the detailed study of the Blechnoid Ferns may be entered upon. 
Blechnum . 
For purposes of the present description, and in accord with general 
opinion since the time of Mettenius, the genus Blechnum is accepted in its 
wider sense, as comprising the sub-genera (i) Lomaria , (2) Salpichlaena , 
(3) Eu-Blechnum. As there is reason to believe that Lomaria most nearly 
represents the phyletically prior type — a question which will be discussed 
when the facts are before us — this sub-genus will be taken first. Lomaria 
differs from Eu-Blechnum in the relation of the sorus to the ostensible margin 
of the leaf. Presl, in his Tentamen (1836, p. 141), speaks of the ‘indusium 
marginarium’ of Lomaria. But in the case of Blechnum (p. 101) he speaks 
of ‘indusium lineare, scariosum, margine libero, costam respiciente \ And 
later (p. 102), he writes of Blechnum more explicitly thus : ‘ Attamen margo 
frondis semper evidentissime liber est, et indusium proprium adest, cum in 
Lomariis, quibuscum hae species confundi possunt, indusium spurium 
e margine frondis replicato et alterato exoritur.’ Clearly he held the 
indusium in the two genera as essentially different things, and since his time 
the question has never been cleared up by comparative and developmental 
observations. Evidence will here be adduced from comparison of the 
development in numerous species, which leads to the conclusion that the 
protective organ is phyletically the same throughout the genus Blechnum in 
its extended sense, and it will be styled the ‘ phyletic margin ’. This true 
margin of the pinna, or ‘ indusium ’, comes to be apparently intramarginal in 
Eu-Blechmim owing to the formation of a new structure, which will here be 
styled ‘ the flange \ Its origin will be traced by comparison of the species 
to be described ; but its formation does not alter the nature of the protective 
‘ phyletic margin ’, notwithstanding that the position of the latter may no 
longer be ostensibly marginal in cases where the flange has attained large 
proportions. The ‘ phyletic margin ’, which then appears as an indusial 
covering to the sorus, and has usually been so described, is still held to 
maintain its identity. But it will be shown that it may undergo considerable 
further modifications by segregation into short lengths ; this will be seen in 
genera held to be derivative from the simpler Blechnoid type, such as Wood - 
wardia and Doodia. 
