Filicales. 
‘9 
ventral plane. The adaxial position of the sporocarp, may, however, 
be secondary, for Mr. Johnson has shown that it arises marginally 
on the leaf. 
The Hymenophyllaceae show few indications of affinity to the 
Marsileaceae, but Dr. Campbell has recently suggested that the 
latter may have been derived from the Schizaeaceae (13), (14). The 
sporocarp is compared to the fertile pinnae of Aneimia, and since it 
arises marginally, the comparison is a fair one. Other similarities 
mentioned are the solenostely, the dichotomy and dichotomous 
venation of the leaves, the shape of the sporangia, and the presence 
in the Salviniaceae of what appears to be a non-indurated apical 
annulus. The further comparison of the simple leaves of Pilularia 
and Schizcea pusilla is hardly legitimate, for both are clearly 
secondary for their respective orders. In spite of the non-soral 
condition of the sporangia of the Schizaeaceae, the Marsileaceae 
may be derived from the former if their solitary sporangia represent 
reduced monangic sori; in this case the Marsileaceae were presu¬ 
mably descended from ancestors of the Schizaeaceae in which this 
reduction had not taken place. 
Neither the Gleicheniaceae, Matonineae or Cyatheaceae appear 
to be closely related to the Marsileaceae, but as the Tree Ferns and 
the Polypodiaceae appear to have had a relatively recent common 
origin, and as there is at least a possibility that the Marsileaceae 
are descended from the Polypodiaceae, it may be that the Cyatheaceae 
are not as remote from the Marsileaceae as might be supposed from 
the much greater development of their stems and fronds. Dr. 
Campbell, in the first edition of his “ Mosses and Ferns,” suggested 
that Cemtopteris might be intermediate between the Polypodiaceae 
and Marsileaceae, a view withdrawn in the second edition in favour 
of the Schizaeaceous affinities of the latter. But even if we discard 
Ceratopteris as a link on account of its solitary sporangia and poly¬ 
cyclic dictyostele, it is still possible to derive the Marsileaceae from 
the simpler, solenostelic Polypodiaceae. The leaf-trace is funda¬ 
mentally of the same type, and the “ mixed sorus ” is only known 
in these two orders. But in spite of these similarities an origin 
from the Schizaeaceae seems at least equally probable. 
The Marsileaceae also show a certain, though a less marked, 
resemblance to Loxsonia. In this genus the sporangia of a sorus 
arise in basipetal order ; Professor Bower, however, has shown that 
such a type of sorus gave rise more than once to a “ mixed sorus.” 
As Loxsoma appears to be closely related to the Polypodiaceae, it is 
natural that forms similar to the latter should resemble the former. 
