MARSH FERN. 
183 
MARSH FERN [pne-ninth the natural size). 
Lastr^ea Thelypteris, Presl, Babington. 
Aspidium Thelypteris, Smith, Hooker. 
This fern must be considered local, but its distribution is very 
general : it occurs only on those boggy heaths where the soil is 
so moist and soft that its rhizoma can extend itself with rapi- 
dity and freedom : it is found in great abundance in such situ- 
ations. The list of localities which I have received through the 
kindness of correspondents, is far too voluminous to publish : 
