RIVER GARDENS; 
arrange plenty of drainage where you plant your 
Perns, hits of charcoal, sharp sand, or rotten 
leaves have been recommended by Mr. Hibberd and 
others. The water must he prevented also from 
running in constantly to the roots; a certain de¬ 
gree of dryness about the root is essential to Perns, 
and your Pern-ground must he constructed accord- 
ingly. 
As a general principle, the water-plants do not re¬ 
quire much, if any, soil; as water is to them, as pre¬ 
viously stated, what earth is to terrestrial ones, and 
the bed of the stream or pond only serving them as 
anchorage. Nevertheless, some plants, especially 
the Water Lilies, apparently require a somewhat 
strong soil to grow in. Plants of this class are, 
however, too large for most Aquaria, though it 
is stated that the Nupliar lutea may he grown in a 
vessel one foot square. 
When the Aquarium has been furnished with 
its plants, with snails to destroy the confervoid 
growth on the glass, and to consume decaying 
vegetation, at the same time furnishing a vast num¬ 
ber of eggs to nourish the fish and other animals 
in the tank, a complete circle of compensating prin¬ 
ciples may he said to have been established which 
impart to an Aquarium many of the permanent 
28 
