394 
THE FERN WORLD 
it must be remembered that the researches of our botanists 
have been necessarily limited, and the fact that a particular 
Fern is more or less plentiful in the localities which have 
been searched, cannot be accepted in proof of the general 
abundance or scarcity of the same Fern in localities which 
have not been searched. 
Description. — The general resemblance, or resemblance 
at first sight, of the present species to Hymenophyllum 
tunbridgense, necessitates that the description of JJnilaierale 
should be directed to an indication of the points of difference 
between the two ferns. The caudices and rootlets in 
both are alike, as also are the colour of the fronds and 
the general habit and mode of growth — the caudices of the 
one being, in fact, often densely interwoven with those 
of the other on the surface of the same rock. The stipes 
in both is similar, and the pellucid and semi-transparent 
texture of the fronds is also similar in both, the fructifica- 
tion is produced in the same manner, and the indusia are 
similar in shape. The frond of Unilaterale, however, is 
narrower and more lance-shaped than that of Tunbridgense , 
the pinnae being — and this is the chief point of distinction 
— decidedly one-sided — that is to say, instead of the divisions 
of the pinnae being equally produced on both sides of their 
mid-stems — the secondary rachides— as in Tunbridgense, 
they are produced on the upper side only. The pinnae are, 
therefore, simpler and less divided ; and their mid-stems 
or veins are convex on the upper side, so that the points of 
the pinnules are sometimes bent back and directed down- 
wards. With the aid of a magnifying glass, it will also be 
noticed that, whilst the cup-shaped indusia in Tun- 
bridgense are fringed or indented on the upper margins, in 
Unilaterale they are entire or smooth. When the two 
plants are seen growing side by side, it will be noticed that 
the pinnae in Tunbridgense overlap each other somewhat like 
