Filmy Ferns 



the Latin radix, " a root," and is probably a reference to 

 the very long, extensively-creeping rhizome. 



On the rocky sides of the waterfall we must search 

 diligently for the two Filmy Ferns. As they are the 

 smallest of British ferns, resembling more some of the 

 mosses among which they grow than the ordinary type 

 of ferns, they must be carefully sought for with an 

 exact knowledge of what we are seeking,, or they will 

 escape our observation. They may frequently be 

 found growing together, and it is only by attention to 

 small points of difference that they can be distinguished 

 from each other. 



One easy test for distinguishing the Tunbridge 

 Filmy Fern from the One-sided Filmy Fern is the 

 presence of teeth on the lips of the cup-shaped indusium 

 of the former, and their absence on the similarly shaped 

 indusia of the latter. Another and, perhaps, a more 

 reliable test is that in the first-named fern the pinnae, 

 the leafstalks, and the indusia all lie in one plane, 

 while the One-sided Filmy Fern has its indusia set 

 almost at right angles to the fronds, the pinnae of 

 which curve backwards and give the one-sided appear- 

 ance to the fern, to which it owes its specific name. 



Both ferns have very thin threadlike rootstocks 

 which frequently become interlaced, as these ferns 

 generally grow in colonies. Both also have the semi- 

 transparent membranous fronds with prominent veins 

 that we noted in the Bristle Fern. 



Let us now examine the two ferns in more detail. 

 B.F. 49 7 



