SELAGINELLA. 
231 
takes place more or less when it is in contact with stagnant 
water, an outlet at the bottom of the case should be care- 
fully provided, by which all the free water at least, which 
drains through after the soil has been irrigated, may be 
removed as it accumulates. 
As to aspect, the northern is decidedly the best, princi- 
pally for the reason that in such a situation the sun has 
less influence on the temperature of the interior of the 
case ; and an extreme degree of confined heat would be 
anything but favourable to these plants. 
The appearance of the case, would, no doubt, be improved 
by covering the soil entirely with living Sphagnum moss, 
which, if neatly packed on the surface, with the tops of its 
stems uppermost, would continue to grow. Most of the 
species of Club-moss would prefer to grow amongst the 
Sphagnum, which, to prevent its being drawn up and 
smothering the plants, should be neatly clipped down 
occasionally with a pair of scissors. 
The interest of such a collection, so far as their appear- 
ance is concerned, would depend of course upon the taste 
with which the rockwork was designed and executed, and 
the plants distributed about it ; but whatever the result as 
a matter of taste, the study of the living plant might be 
