GROWTH OF FERNS. 
7 
moisture that clings to the under surface ; this is really 
necessary for the following reason, where damp exists, 
mould or other forms of minute fungi are sure to appear. 
They love a close atmosphere, but will not grow to any 
great extent if it is constantly renewed. The reason for 
the occasional removal of the glass is therefore obvious, 
i.e. if not removed, the strong growth of moulds would 
choke the more delicate and gradual increase of the 
minute prothallus of the fern, as drawn at fig. 11, and 
described at page 19. 
To observe the growth of these spores, a good plan is 
to place in a common flower-pot saucer pieces of chalk,, 
sandstone, or pumice-stone. Over these dust the spores 
which have been collected as above mentioned, remem¬ 
bering to keep half the quantity for future experiments 
and microscopical examination ; pour in water sufficient 
to damp the stone by its capillary action, but not to 
cover its upper surface. Over all place a bell-glass, 
which must be cleaned once in every three or four days 
to prevent fungoid growths, or it may be left uncovered , 
though not so favourable for the successful growth of 
young ferns. In either case the water must be kept up to 
B 
