INTRODUCTIOX. 1 3 



Plants. 

 Marine Plants for an Aquarium should be taken attached 

 to the stones or pieces of rock on which they grow. When 

 once the root is detached the plant is dead. The stone 

 should be as clear as possible from sponges ; and many other 

 living incrustations are likely to die, and their decay will 

 prove injurious to the water. Rhytiplil(Ea imiastroides, Coral- 

 Una officinalis, Lelesseria alata, Chondrus crispus, Poly si- 

 phonia, Phi/llophora ruhens (Plate XIII.), Griffithsia, and 

 Callithamnion are recommended for red seaweeds; species 

 of Codium, Cycladopliora, Bryopsis, and Viva are suitable for 

 greens. In ordinary tanks, the green w^eeds are decidedly 

 the most healthy, but the deep sea tank on trial by Mr. 

 Warrington is partly contrived to encourage tlie growth 

 of reds, which are very pretty objects, to tlie discourage- 

 ment of the greens, which flourish in the light. It is 

 found that weeds of any kind may be used more sparingly 

 than was at first supposed. After a time the stones in 

 a tank will be found covered with a brownish confervoid 

 growth, which throws off a considerable amount of oxygen, 

 as may be observed by the little quicksilver-like bubbles 

 about it. When a tank is in this condition, larger weeds 



