MANAGEMENT OF AQUAEIUMS 249 



Washington plant, or Cabomba viridifolia, 

 whose stem and leaves are fern-like in their 

 gracefulness. The fan-shaped leaves are a 

 brilliant glossy green and are slashed clear to 

 the stem into thread-like sections. 



The pond-weeds (Potamogeton) and the 

 hornwort (Ceratophyllum) are both favourites, 

 especially Potamogeton densus, with brownish- 

 green leaves attached opposite each other on 

 a reddish stalk, but on account of the eager- 

 ness with which mollusks and fish attack and 

 devour the leaves and stems it soon loses much 

 of its beauty. The hornwort is an attractive 

 and effective plant, with narrow forked leaves 

 set round the stem in whorls. It is one of the 

 commonest of our native water-plants, and 

 takes to an aquarium as to the manner bom. 

 It may be tied together in little bunches, 

 weighted with a piece of stone or lead and sunk 

 to the bottom, where it will flourish just as 

 well as though it were regularly planted. 



The duck-weeds are favourites among the 

 floating plants. They have minute generally 

 rounded leaves which rest flat upon the sur- 

 face of the water, and small roots that hang 



