WATER-PIiANTS. 



89 



Fig. 71. Lesser Duckweed 

 (Lemna minor). 



The Characece are divided into two genera — Cha/ra and 



Nitella (Fig. 73) — both of which are very useful and ornamental 



in aquaria, but particularly 

 ia those which contain only 

 very small animals. These 

 plants are too fragile to be 

 placed within the reach of 

 large fish. There are many 

 species of the Characece in 

 Britain, some of them being 

 common. They gi-ow ia ponds 

 and ditches where the water 

 is clear. They have neither 

 true leaves nor true flowers, 

 but they have instead sub- 

 divided branches and a curious 



kind of fruit. The principal difference between the Chara 



and the Nitella is that the 



former has a compound stem, and 



the latter a simple one. These 



plants, especially the Nitella trans- 



lucens, do not require much light 



for their development, growing far 



better when placed at some dis- 

 tance from the window than when 



cultivated in close proximity to 



it. A small portion of each 



plant should be sunk by the 



help of a small stone to the 



bottom of the aquarium. Both 



the Chara and the Nitella succeed 



much more satisfactorily when 



planted in this way than when 



simply thrown into the water. 



They grow very quickly, and will 



in a short time fill the recep- 

 tacle in which they are placed. These plants are also very 



interesting on account of the ease with which the circulation 



Fig. 72. Ivi'-LEAVED Duckweed 

 (Lemna trisulca). 



