CHAPTER VI. 



-WATER-PLANTS. 



T has already been explained why aquatic plants of 

 some kind or other should always be present in an 

 aquarium ; and in this chapter a few hints are 

 given as to the choice and management of such vegetation. 

 Half the pleasure of owning and caring for an aquarium would 

 be gone if no plants were necessary : they give to the tank 

 nearly all its beauty. 



Almost every aquatic plant can be grown in the still water 

 of an aquarium, and be made more or less useful there. Some 

 may be introduced chiefly for their beauty, others for their 

 utility; but for both beauty and utility none is superior to 

 the Italian Water-weed Vallisneria spiralis. This plant has 

 for many years been a great favoui-ite with those who keep an 

 aquarium; for besides being ornamental and useful, it is also 

 exceedingly interesting, inasmuch as it possesses a peculiar 

 method of reproduction, and in its graceful grass-like leaves 

 the cyclosis, or circulation of the sap, may be readily seen by 

 the help of a microscope, just as one may observe the circu- 

 lation of the blood in a frog's foot or in a tadpole's tail. 



Vallisneria spiralis belongs to the natural order Hydro- 

 oharidese, of which there are only three species native in Britain, 

 viz., the Frog-bit (Hydrocharis morsus-rance), the Water- 

 Soldier {Stratioies aloides), and the somewhat lately introduced 

 Canadian Water-weed Anardharis Alsinastrum. 



