VEGETATION OF STILL WATER 29 



(/) Pondweeds, chiefly Potamogeton natans. 



(b) Open water, with Diatoms and other Algae, chiefly Chara 

 and Nitella. 



Of these, the Reed association is the one that varies the most. 

 With the Scirpus lacustris, sometimes the dominant form, may 

 be associated the Common Reed, Phragmites communis (a true 

 grass), or a species of Equisetum (E. limosum). The Common 

 Reed, with its horizontal stem and vertical branches, is of great 

 service in enabling the plants to get out from the edge into more 

 open water. Other plants commonly found with the Reed 

 association are the Flowering Rush, the Water Plantain, and the 

 Arrowhead plants which also belong to running water. With 

 regard to the Water-Lily association, it is found in Switzerland 

 and Germany that the Yellow Water Lily succeeds the White. 

 The Quillwort may also be found in this belt. It is interesting 

 to note that the Duckweed, characteristic of ponds is not found 

 in lakes. 



Fresh-water lakes, to which the sea may have had access in 

 past geological ages, often have a flora of peculiar interest. The 

 shores of Lough Neagh yield the following maritime plants : the 

 Sea Scirpus, Field Cerastium, Stork's Bill, Hare's-foot Clover, 

 and Sandspurry. Many water plants, such as the Awlwort, 

 the Water Parsnip, the Elongated Carex, used to be found there, 

 but seem to have disappeared with the lowering of the level of 

 the lake. 



Many of the plants mentioned as characteristic of the edges 

 of lakes are also found in very gently flowing water in canals 

 and in back waters. The Creeping Scirpus, the Water Plantain, 

 the Arrowhead, Sweet Flag, the Flowering Rush are instances. It 

 would be easy to make records of the plants found by the side 

 of any of the numerous canals which intersect the country ; they 

 should be visited early in the summer, before vegetation begins 

 to decay, as they are not then very pleasant. 



(b) BOGS AND FENS. It is not always easy to distinguish a 



i bog from a marsh, the transition from one to the other being 



sometimes very gradual. To most minds the term " bog " 



. recalls soaky, peaty ground in the midst of a heather moor ; but 



