16 BRITISH FERNS. 
“introduced, and the sides may be clothed throughout 
with graceful and luxuriant Lycopodiums and delicate 
Filmy Ferns. 
And now I must say a few more words about the 
use of glass for ferneries, In almost every part of 
England there is an absofute necessity for a covering 
of glass, the advantages of which are manifold: in 
the first place, the ferns are thus entirely protected 
from the effects of wind, so fatal to the perfect 
development of their tender and delicate fronds, and 
also from the worst effects of frost. The glass 
“covering may be of any form that taste may dictate 
or convenience require. It is quite impossible that 
any resident in the neighbourhood of great cities 
should have failed to observe the continued falling 
of smoke-flakes, or « smuts,” as they are usually and 
a yellowish speck on the leaf, but that they impeore 
and enrich the water with which they may be 
mixed. ‘The glass canopy, of whatever shape or 
character it may be, receives these smuts they fall, 
