CHARACTERS OF TRIBES AND GENERA, 343 
as a distinct natural order of Ferns, which I do not deem 
it desirable to adopt. I must, however, admit that it has 
no direct affinity with any other family of Ferns, except 
with the tribe Saccolomow, through the genera Lozsoma 
and Microlepia. 
The peculiarity of the sporangia consists in being ses- 
silely attached by its inner side to the columnar receptacle, 
the point of attachment being central, or more generally 
eccentric towards the lower limb, and the numerous spo- 
rangia being compactly seated round the receptacle, they 
consequently acquire a flattened form, each having an arti- 
culated ring passing round it, at a more or less oblique or 
at a right angle with the point of attachment, being thus 
analogous to the flattened sporangia of many Cyathee, as 
noticed at page 41. 
Most authors place the whole of the species under the 
genera Hymenophyllum and Trichomanes. On comparing 
the respective characters of these two genera it will be 
observed that their technical distinctions are not very 
definite, depending chiefly upon the difference in length 
. and more or less bilabiate character of the indusium, in 
conjunction with the varying length of the sporangiferous 
receptacle. In those species which may respectively be 
considered as typical, these characters are sufficiently mani- 
fest, and leave no doubt as to the genus to which they 
should be referred ; but the numerous intermediate forms, 
and the different appearances presented by some species at — 
different periods of growth, often render the determination - 
ofthe genus by herbarium specimens very embarassing, 
and the difficulty is still further increased by the fact that 
the two genera contain individual species agreeing perfectly 
in general habit. It therefore appears to me that the 
m: between Hymenophyllum and Trichomanes is 
