I90 PLANT LIFE. 



above the locks on the Forth and Clyde Canal very 

 often contain floating stems of Poa jluitans. Sometimes 

 these stems extend three feet or more out from the bank, 

 and many Spirogyras and other Algae are attached to 

 them. These plants also entangle floating material of 

 all kinds, so that the shoreward side becomes suffi- 

 ciently firm to support mud-plants and even such grasses 

 as Poa annua. About three feet of land may in 

 this manner be added to the banks, and hence a 

 continual clearing of the canal becomes necessary. 

 The hardiest of these water-plants and the most 

 objectionable from a fisherman's point of view is 

 Elodea Canadensis. This multiplies so rapidly that it 

 seems able to choke out everything else ; and it often 

 fills shallow ponds with a dense mass of vegetation. 



Other characteristic water-plants occur, especially 

 in summer, in small streams and in shallow rivers, 

 or in those of a moderate depth. The various forms 

 of Ranunculus aquatilis and of Potamogeton must be 

 mentioned, as it is possible to trace in them regular 

 modifications, adapting them to the rapidity or slow- 

 ness of the current in which they are found. The 

 more rapid the current the longer and the finer divided 

 the leaves. When the Ranunculus is able to do so, it 

 forms undivided air leaves supported above the water. 



The reader will find that anyone of the marsh or 

 water plants which he studies in the field shows many 

 other interesting adaptations to its position. The 

 reproduction of these fresh-water plants is also peculiar. 

 Some of them have special arrangements for seed- 

 distribution. The Water-lily, for instance, has seeds 

 which are able to float, and which are also eaten and 

 probably scattered by water hens. Veronica Beccabunga, 

 whose long trailing stems occur chiefly in very small 



