Reconquest of the Water 



Willows whose branches have drifted down stream 

 are also very useful, for by judicious planting of certain 

 kinds the channel can be kept in its place, as indeed 

 has been done on the Mississippi. 



Unfortunately in many of our rivers the water is 

 polluted by drainage ; in such cases one often notices 

 the long waving locks of a green Alga Cladophora, often 

 1 8 inches or 2 feet in length. These slimy masses 

 are detested by the fisherman, who still infrequently 

 catches a trout or grilse in some of these streams. 

 After a heavy flood they seem to disappear, probably 

 because the shingle stones rubbing against one another 

 rub them off, but they soon grow again. 



In very badly polluted streams, the whole of the 

 bottom and everything in the water is often covered by 

 dirty white waving tufts, which have a slimy and horrible 

 appearance. This is a fungus, Apodya lactea, and is a 

 sure sign of pollution. 12 



The Clyde below Glasgow, the Thames below London, 

 and other city rivers are inhabited by masses of bacteria, 

 which, however, purify the water and disappear as soon 

 as all the organic matter has been digested by them. 

 Such pollution is of course a waste of valuable organic 

 matter and dangerous to mankind. It is difficult to under- 

 stand how fish withstand such poisonous waters at all. 



A trout was discovered a few years ago apparently 

 trying to mount the steps at the Broomielaw in Glasgow. 

 Some kindly person put it in a bucket of fresh water, 

 and it was taken to the police station, where, however, 

 it died in spite of every care and attention. 



1 Webber. 2 Bonnier. 3 Henslow, Freidenfeldt, Massart. 



4 Wylie. 5 McCallum. 6 Oliver. 



7 Fruh and Schroter. 8 West. 9 Lyons. 



10 and n Geographical Journal, March 1900 and September 1902. 



12 Turnbull. 



139 



