Fresh Water Algae in Vicinity of Montreal 399 



covered by a thin layer of ice, for by this time 

 it was the end of October. The Elodea appeared to have 

 been killed by the low tempeprature, but the algae were 

 unhurt. Quantities of Spirogyra and CEdogonium were 

 found in the swamp near the street-car tracks. Clado- 

 phora, as usual, occurred along the edges of the river, 

 this alga showing a preference for well-aerated waters. 

 In general there was a constant association of Elodea 

 and filamentous forms. 



Preservation op Alg^:. 



While the majority of algas can be cultivated, or at 

 least kept alive in fresh water under suitable conditions 

 of light and temperature, some forms disintegrate and 

 disappear within a short time after being brought into 

 the laboratory. In order to secure those which might 

 otherwise have disappeared before they could be 

 identified, I preserved a sample of the freshly 

 gathered contents of each aquarium. For this 

 purpose I used a two per cent, solution of 

 potassium acetate, containing just enough acetate 

 of copper to make it faintly blue. This solution 

 which is much more satisfactory than formalin as a pre- 

 servative for alga?, gave the most excellent results with 

 nearly every form. Vaucheria was slightly plasmolysed 

 by it. This may be avoided by a method suggested by 

 Mr J. H- Nieuland". The plant should be killed 

 rapidly with three or four per cent, formalin, which 

 must be quickly and completely removed by repeatedly 

 washing the plant in water, after which it should be put 

 into glycerine to which a little thymol has been added. 

 Thus it will retain its color perfectly. 



Anabsena was also very difficult to preserve in this 

 solution, the filaments rapidly becoming disorganized 

 and breaking down. This was probably due to the copper 

 having been too strong. As Moore 13 has shown in 

 his experiments with copper as an algicide and disinfec- 



