Studies in the Phylogeny of the Filicales. 
/W;> 
IV, Blechnum and Allied Genera. / c i 
BY 
F. O. BOWER, F.R.S. 
With Plates XXII-XXXII and twenty-six Figures in the Text. 
HE Ferns now included in the comprehensive genus Blechnum number 
JL about 140 species, and are very widely spread geographically. They 
vary considerably in habit, some being small erect Tree-Ferns, others having 
an elongated creeping rhizome, while some assume even a climbing habit. 
In their leaves also they show great diversity, for in some there is a strong 
dimorphism of the sterile and fertile fronds, the latter having narrow 
segments and standing usually erect, the former being broader in expanse 
and more or less inclined. In others the sterile and fertile leaves resemble 
one another both in form and position ; others, again, among the climbing 
species bear three distinct types of leaf, of which two are sterile. The 
leaves are usually simply pinnate, but some species show more complex 
branching. The 4 sori which as we shall presently see are really the result 
of the extension and fusion of true sori, are elongated, running parallel to 
the midrib of the segment, and are protected by an indusial flap, which has 
its margin directed towards the midrib. But there is some diversity in the 
position which the sorus holds relatively to the apparent margin of the leaf ; 
sometimes it appears to be near to the margin itself, in other species it 
appears to be distinctly intramarginal, but it is always in close proximity 
to the midrib even where the fertile pinna is a broad one. 
The genus thus variable has undergone vicissitudes of classification. 
Originally Linnaeus founded the genus Blechnum in 1753 . The Index to 
the Linnaean Herbarium, printed as a Supplement to the Proceedings of 
the Linnean Society (1911-12, p. 45), shows five species included in the 
genus. Of these three are still retained (B. australe , Occident ale , and 
orientale ), but the other two are now separated in the genus W oodwardia 
( W. radican * and virginica). Thus not only was the genus undivided, but 
Linnaeus included in it also Ferns now segregated in W oodwardia. In the 
Synopsis Filicum of Swartz (1806) W oodwardia was separated, though the 
[Annals of Botany, Vol. XXVIII. No. CXI. July, 1914.] 
