58 THE AQUARIUM. 



CHAPTER V. 



SIMILARITY BETWEEN THE FUNCTIONS OF PLANTS AND ANI- 

 MALS THE AQUARIUM PRINCIPLES UPON WHICH IT IS 



SUSTAINED EARLY EXPERIMENTS WITH THE AQUARIUM 



PLANTS MOST SUITABLE FOR THE PURPOSE SEA WEEDS, 

 MOULD, LICHENS, MOSSES, FERNS. 



is a very curious fact that in many of 

 the functions of plants, we observe a 

 close resemblance to those witnessed in 

 animal life ; thus, the circulation of the 

 sap, which will be more fully described 

 hereafter, is in effect precisely similar 

 to the circulation of the blood in the human 

 body, vessels being provided in each, which 

 are peculiarly adapted to carrying the fluids 

 which support their existence to the parts 

 where they are needed. Respiration is also a point 

 in which great similarity exists. Leaves are the 

 breathing organs of plants ; through them the sap is 

 brought into contact with the air, where it absorbs 

 that which is necessary for its purification. In this 

 operation we shall notice a wonderful provision by 

 which nature seeks to preserve a proper balance be- 

 tween the requirements of the animal and vegetable 

 world. In the purification of the blood, the air taken 



