Pond Societies 



335 



bur-reed (Sparganium) , of bulrush (Scirpus), of spike- 

 rush (Eleocharis) , of water plantain (Alisma) , of arrow- 

 head (Sagittaria) , and arrow-arum (Peltandra, of pick- 

 erel-weed (Pontederia) , of manna grass (Glyceria), etc. 



2. The intermediate zone of surface aquatics will 

 include such as: 



(a). These rooted aquatics with floating leaves: 

 white water-lily (Castalia), spatterdock (Nymphasa), 

 water shield (Brasenia), pondweed (Potomogeton) , etc. 



FIG. 196. A spray of the sago pondweed, Potamogeton, coated with 

 slime-coat diatoms, its leaf tips bearing dwelling tubes of midge 

 larvse (Chironomus). 



