16 
BRITISH FERNS. 
{ Lobes of the pinnas entire. Sori near their margins .. .. 22 
Lobes of the sori slightly toothed. Sori near their base or 
centre ..23 
{ No scarious scales on the stalk. No glands on the leafy part. 
Aspidium Thelypteris. 
Stalk with brown scarious scales at the base. Minute glands on 
the under surface of the segments. Aspidium Oreopteris. 
23 
24 
{ Segments of the pinnas oblong, very numerous, scarcely broader 
at the base . Aspidium Filix Mas. 
Segments ovate, wedge-shaped at the base. 
Aspidium cristatum. 
/ Segments of the pinnas with finely pointed, almost prickly 
teeth ; the inner lobe or tooth at the base much larger than 
I the rest .. .. .. Aspidium aculeatum. 
Segment of the pinnas with shortly pointed teeth or pinnatifid ; 
\ the lobes of each side similar . .. .. 25 
25 
26 
Sori circular. No indusium .. .. Polypodium ALPESTRE. 
Sori circular, with a kidney-shaped or almost peltate indusium 
I attached by a point .. .. .. .. .26 
Sori rather oblong, with an indusium attached along one side 
Asplenium. 
( Segments ovate or ovate-lanceolate. Indusia conspicuous and 
persistent . Aspidium cristatum. 
Segments oblong-lanceolate. .27 
! Indusia conspicuous and persistent .. Aspidium rigidum. 
Indusia small and often soon disappearing. 
Aspidium spinulosum. 
The way in which this index is used is as follows: 
Suppose we have the Common Hart’s-tongue, Scolo - 
pendnum vulgare, in our hands ; we look to the para¬ 
graph numbered 1, and here we have three forms of 
fructification mentioned. The form to which the 
Scolopendrium belongs is “ Fructification on the back 
or under side.” Opposite this is the figure 5. This 
to direct us to paragraph 5. Here we find two 
