44 FRESH- WA TER AQUA RIA. 



leaves. These roots terminate in a spongy base, 

 through which the work of absorption is carried on. 



In forming aquaria wherein it is intended to grow 

 aquatic plants, a good deal of attention ought to be 

 paid to the fact whether such plants require much or 

 little soil. With the exception of the duckweeds, all 

 require some, if only to anchor their roots in. But 

 this mud should be dispensed with as much as pos- 

 sible, on account of the tendency there is to thicken 

 the water whenever fishes or other animals stir it 

 up. The great water beetle (Dyticus) very often does 

 this, especially in the night time ; and so you awaken 

 some morning to find the water, which was clear the 

 night before, in what seems a hopelessly muddy condi- 

 tion ! Little if any soil is required by the Anacharis 

 (a Canadian plant), one of the most useful an aqua- 

 rium keeper can have if kept in proper bounds, for it 

 grows only by shooting or budding, never by seeding, 

 and many aquatic animals, fishes especially, are very 

 fond of nibbling at the young green shoots. Another 

 plant, equally useful and even more beautiful, is the 

 star-wort (Callitriche), which requires a little sediment 

 for its roots to be planted in. The leaves of the 

 star-wort are much used by fishes and amphibia for 

 depositing their spawn upon. The water crowfoot 

 (Ranunculus aquatilis) requires little soil for its roots, 

 but its needle-shaped leaves soon branch through and 

 fill up the interior of the tank if too strong and old a 

 plant be introduced. It is worth trying a little of this 



