SEPTEMBER 159 



XL 



A notable addition to the dietary of British water- 

 fowl was made about the middle of last cen- 



The Amerl- 

 tury through the introduction of Canadian can Pond- 



pondweed, then known to many botanists as weed ' 

 Anacharis alsinastrum, but in recent classification as 

 Elodea Canadensis. It is a unisexual plant and, so far 

 as known to me, only the female form has reached this 

 country ; wherefore no seeds are produced on this side 

 of the Atlantic. Even if they were so, it is not likely 

 that the reproduction and dissemination of the species 

 would be perceptibly accelerated, for every fragment of 

 the tangled steins that is broken off and floated away 

 is the sure founder of a new colony. 



This weed, which is not destitute of beauty both of 

 form and colour, behaves in a manner peculiar to itself 

 in British waters. So soon as a piece of it finds its 

 way into a lake or river with rich alluvial bottom, it 

 spreads with amazing rapidity and soon chokes up a 

 wide water area. A few years ago, I forget how many, 

 a sudden uprush of Elodea took place in Lochleven, 

 and despairing anglers wrote to the newspapers com- 

 plaining that the fishing in that famous loch had been 

 ruined for ever, unless means could be devised for 

 eradicating the pest. Having had experience of its 

 behaviour in our Sanctuary Loch, which is far smaller 

 than Lochleven, as it covers only between sixty and 

 seventy acres, I wrote a reassuring letter to the Scots- 

 man newspaper, bidding anglers believe that their 

 occupation was not gone, only suspended for a few 

 seasons. I ventured to predict that the weed would 



