4 Weiss, Submerged Vegetation of Lake Windermere. 



massed together, and would not interfere with the ground- 

 feeding of the fish. But the pebbly bottom, and to some 

 extent the plants above mentioned themselves, were 

 covered with a dense growth of a creeping fresh-water 

 Alga, CladopJiora, which I was told grew especially rapidly 

 in hot weather, and formed a close carpet over the bottom, 

 thus preventing the fish from getting at the worms, etc. 

 This bay was a favourite place for drawing up the nets, 

 and at the time when they were in constant use this 

 insidious vegetable growth was said to have been practi- 

 cally absent. 



A detailed description of the various forms of sub- 

 merged plants which interfere with the fishing, and their 

 methods of reproduction, is given as the measures to be used 

 in reducing this vegetation depend largely on the season 

 of flowering and their methods of vegetative reproduction. 



Probably one of the most persistent and harmful of 

 the submerged aquatics in Windermere is the Nitella 

 opaca^ Ag., belonging to the group of Characeae or 

 Brittleworts. This is found rooted in the softer, more 

 muddy, parts of the lake at varying depths from 6 to i6 

 feet, growing some i8 inches to 2 feet in height Like 

 many of the Characeae it smells very strongly of garlic 

 when taken from the water, but this particular species 

 can readily be distinguished, apart from its detailed 

 structure, by the tendency to become nearly black as the 

 plants get older. Nitella opaca grows frequeiitl}' in 

 very deep water, being less dependent upon light than 

 other Characeae. It is a very variable species, and the 

 particular form fuund in the regions of Windermere 

 mentioned above is probably the variety elongata of 

 Alexander Braun, which is generally found on the 

 bottom of large lakes, where it grows to considerable size 

 and covers very large areas, forming regular meadows. 



