■WATBE-PLATNS. 



87 



Fig. 67. Fruit op Trapa natans. 



chestnut, hence the common name. This plant can often be 



bought in London for a moderate sum : but perhaps the seed 



might be obtained more readily. 

 The Water Awlwort {Subw- 



laria aquatica) (Fig. 68) has 



been strongly recommended 



as a plant suitable for an 



aquarium, but I have never 



been fortunate enough to 



obtain a specimen. It is only, 



as a rule, found in mountain 



lakes. The leaves, awl-like in 



shape, grow from the root, 



which is composed of long 



white fibres. The flowers are small, and sometimes are borne 



under water. 



Though almost everyone knows the duckweed when he sees 



it, yet very few, comparatively, know what an interesting plant 



it really is. Four species 

 of duckweed are found 

 in Great Britain, and all 

 are useful and pleasing 

 in the aquarium, for they 

 keep the water shaded at 

 the surface, they form 

 hiding-places for the 

 smallest animals, they 

 are introduced without 

 trouble, they grow well, 

 and their presence has 

 a pleasing efPect. Only 

 a few plants should be 

 placed in a tank at a 

 time, as they multiply 

 rapidly. They increase 

 by ofEshoots at the edges 



of the fronds. The duckweeds are the smallest of all flowering 



plants, but they blossom very rarely — ^the Greater Duckweeds 



Fio. 58. Water Awlwort 



(SUBDLARIA AQUATICA). 



