On the Genus Fissidens. 
ERNEST STANLEY SALMON. 
With Plates V-VII. 
Part I. Morphology. 
HE structure of the leaf in the genus Fissidens is 
JL generally described as quite anomalous amongst 
Mosses. The leaf may be divided into three distinct parts : 
(i) the sheathing part, consisting of the two wings, or vaginant 
laminae (Fig. i, a , a\ inserted more or less horizontally on 
the stem ; (2) the part above the vaginant laminae, con- 
stituting the superior lamina (b) ; (3) the whole length of 
the leaf below the nerve, the inferior lamina (e). Figs. 2, 
3, and 11 show the position of the parts as seen in transverse 
section. This peculiar leaf-structure occurs, without excep- 
tion, throughout the large genus of Fissidens , which numbers 
[including the subgenus Conomitrium ( Octodiceras)\ nearly 500 
species. 
The only variations from the type of leaf shown at Fig 1 
are in the following points : (1) the relative size of the 
sheathing part — this is sometimes broad, and extends more 
than half the length of the leaf, or it may be small, and 
comparatively insignificant (Fig. 13); (2) the inferior lamina 
may be well developed to the base of the leaf, and inserted 
[Annals of Botany, Vol. XIII. No. XLIX. March, 1899.] 
