AQUATIC PLANTS 



203 



long for the size of the plant, but fishes usually eat them down to 

 about half length, which interferes with a full development of plant. 

 In the greenhouse, where they have a moist atmosphere and no inter- 

 ference, they develop with great rapidity. The variety illustrated, 

 Sahnnia natans, is native to Europe and is the form commonly used. 



Although it is claimed that neither Salvinia nor the common wild 

 Duckweed performs any oxygenating function, the author and others 

 have many times seen aquaria completely covered with either of these 

 plants and, with no other plants in the aquarium, the fishes were get- 

 ting along perfectly well — a state of affairs which would be impossible 

 if the water were blanketed over by an inert substance. 



TRIANEA 



Trianea bogotcnsis is an attractive, small floating plant with thick, 

 heart-shaped leaves. It needs a moist warm atmosphere and not too 

 much direct sun. Under these conditions it thrives and is a valued 

 feature in the summer pool or greenhouse tank. It is not found 

 locally in temperate climate, but may be had of dealers. 



FROGBIT 



HydrocJiaris morsns-rance, requiring the same conditions as Trianea 

 bogotensis, deserves more attention than it is receiving. Of very pretty 



I Fig. 192. 



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