Studies in the Phytogeny of the Filicales. 
II. Lophosoria, and its Relation to the Cyatheoideae and 
other Ferns. 
BY 
F. O. BOWER, Sc.D., F.R.S. 
Regius Professor of Botany in the University of Glasgow. 
With Plates XXX-XXXVI. 
I N my ‘ Studies in the Morphology of Spore-producing Members, No. IV. 
Leptosporangiate Ferns’ (‘Phil. Trans.’, 1899, vol. cxcii, p. 122), the dis- 
tinction was drawn according to the mode of development of their sori 
between the Ferns designated as the Simplices, the Gradatae, and the 
Mixtae. These were held to illustrate three steps in the evolution of the 
sorus. It was specifically stated that there was no intention to assert that 
the living Ferns of any one of these categories were the actual ancestors of 
those of any other. Nor was it suggested that the progression was by any 
single line of descent. Parallel development along a multiplicity of lines 
was distinctly contemplated^ involving in any one of them progressions 
from the Simple to the Gradate, or from the Gradate to the Mixed state. 
It was even held as possible that a progression might have been effected 
directly from the Simple to the Mixed state ( 1 . c., p. 124), a transition which 
has since been demonstrated to have occurred within the genus Dipteris 
(Miss Armour, ‘New Phytologist,’ 1907, p. 238), and it is highly probable 
that it has occurred also in the descent of Plagiogyria (‘Annals of Botany ’, 
vol. xxiv, p. 438). 
Perhaps the most obvious suggestion of transition from the Simple to 
the Gradate sorus that could be made is that from some Gleicheniaceous type 
to the Cyatheaceae. Already in 1899 it was pointed out ( 1 . c., p. 123) that 
‘ Gleichenia dichotomci has a naked sorus ’ differing ‘ little in general con- 
struction from that of Alsophila atrovirens ’. This case was not quoted 
then as indicating a true line of descent, but as an illustration how near 
one type may be to another in point of arrangement within the sorus. 
The widening of the basis of comparison, especially in respect of the vascular 
anatomy, led in 1908 to a more explicit statement (‘Land Flora’, p. 610), 
that ‘ there seems good reason to see in the Cyatheaceae a series having 
[Annals of Botany, Vol. XXVI. No. CII. April, 1912.] 
