PLANTS FOR. 31 



whorl. The cellular tissue of these leaves, like 

 those of Valisneria, exhibits a circulation. They 

 are also lined with -a siliceous deposit, which 

 render them beautiful objects under the micro- 

 scope with polarized light. 



THE FROG-BIT (Hydrocharis Morsus-Rance), Fig. 8, 

 is also a British plant, belonging to the family of 

 Hydrocharads, and which may be made use of 

 for the Aquavivarium. It is very commonly 

 found in ditches and ponds all over England. 

 It is a floating plant, with horizontal stems, from 

 which it sends down rootlets into the water, and 

 sends up several long-stalked kidney-shaped 

 leaves, which lie upon the surface of the water. 

 It has large white delicate flowers, which blossom 

 in July and August. 



THE WATER SOLDIER (Stratiotes aloides), Fig. 9, is 

 another Hydrocharad. It is not uncommon in 

 lakes and ditches in England. It is abundant on 

 Wandsworth Common, also in the fens of Norfolk 

 and Lincolnshire. Whilst growing in the water, 

 it looks very like the top of a pine-apple. It 

 has long sword-shaped leaves, with sharp teeth 

 on their edges, hence its name of Water Soldier. 

 When young, the leaves are green, and look 

 pretty in the water ; but as they grow old they 

 become darker and decay. It does not appear 

 to grow very rapidly ; and although it forms a 

 curious variety for the Aquavivarium, it is not 

 advisable to be entirely dependent on it for 

 appearance or the aeration of the water. 



THE NAIADS (Naiadacce) are a submerged or float- 

 ing family of plants, almost any of the species of 

 which may be cultivated in the Aquavivarium. 

 The great British genus of this family are the 

 Pond-weeds (Potamogetori). Upwards of twenty 

 species of Pond-weeds have been described. They 



