32 THE AQUAVIVARIUM. 



are all characterized by having flowers without 

 stalks seated on spikes, and the parts of the flowers 

 answering to the number four. Thus they have 

 four anthers, four styles, four parted fruits, and 

 so on. They all grow in the water, some being 

 entirely submerged, whilst others have their 

 leaves floating, and project their spikes of flowers 

 into the air. Any of the species may be obtained 

 for the Aquavivarium. 



THE OPPOSITE- LEAVED POND- WEED (Potamogeton 

 densus) is a very pretty species ; the leaves are 

 ovate or lanceolate in shape, without stalks, and 

 are crowded together around the stems. It is 

 found in ditches, and is the only species of Pond- 

 weed that does not possess the little scaly bodies 

 at the base of the leaves, which botanists call 

 stipules. 



THE FENNEL-LEAVED POND- WEED (Potamogeton pec* 

 tinatus), Fig. 10, is a pretty grassy-looking plant, 

 and presents an agreeable change in the foliage 

 of the Aquavivarium. It is not a very common 

 plant, but it grows in the neighbourhood of 

 London. It is said to grow in the Serpentine, 

 and I have procured it from the canal in Regent's 

 Park. Another species is 



THE GRASSY POND- WEED (Potamogeton gramineus). 

 It has long linear leaves, and, like the last, forms 

 a good contrast with the broader-leaved species. 



THE CURLY POND-WEED (Potamogeton crispus) is 

 one of the most frequent species, occurring every- 

 where in ditches and ponds. It is at once dis- 

 tinguished by the waved curly form of its leaves, 

 and may be procured in most running ditches 

 and streams. 



THE DUCKWEEDS (Lemnacece) are a family of plants 

 not to be neglected for the Aquavivarium. 

 They are amongst the simplest of flowering 



