I IO 
Salmon. — On the Genus Fissidens. 
are usually described as 2-lobed, with the smaller dorsal 
lobe (a) attached intramarginally on the larger ventral lobe 
(b, b'). It seems to me more probable, however, that we have 
here a keeled leaf bearing a laminar appendage (b), and that 
consequently a close approach is made to the structure of 
a Fissidens leaf. A transverse section in the lower part of 
these Schistochila leaves is shown at Fig. 24. It is not 
unusual to find in some species of Schistochila with this 
‘ intramarginally ’ placed lobe, e.g. 5 . alata (Lehm.), Schffn., 
that instead of the single outgrowth ( b in Fig. 24) at the 
back of the leaf, there are two of these (Fig. 25, b , b ), when 
it is clearly impossible to consider both as anything but 
laminar outgrowths. This view of the morphology of the 
leaf is supported by the occurrence of species in the same 
genus, e.g. 5 . lamellata (N. ab E.), Dum., (Fig. 26), in which 
the whole back of the leaf is covered with numerous parallel 
laminae. 
Goebel ( 13 , 14 ) gives quite a different explanation of the 
leaf-structure of these Hepaticae. The part (a) of Fig. 23 is 
considered a ‘ lamella ’ borne on the upper surface of the leaf, 
which consists of the rest of the expansion ( b, b '). According 
to this view there would be no real resemblance between 
the leaves of these species of Schistochila and those of 
Fissidens, for the ‘ lamella ’ of the Schistochila leaf (Fig. 24, a) 
would correspond to the inferior lamina of the Fissidens 
leaf (Fig. 3, i. /.). But in the face of the general occurrence 
of concave or keeled leaves in the genus Schistochila , as well 
as in such genera as Diplophyllum (Fig. 27) (which perhaps 
shows the primitive form of these leaves), it is difficult to 
accept Goebel’s explanation. Such cases, too, as that men- 
tioned above (Fig. 25) cannot possibly be explained on this 
theory. 
The other objection to Robert Brown’s theory is raised 
by Braithwaite, who says, ‘ there are species in which the 
duplicate part is nearly or altogether wanting, e.g. F. dealbatusl 
I have not been able to find any leaves of a Fissidens with 
the vaginant laminae absent; in F. dealbatus (Fig. 13) these 
