1896.] water currents on the assimilation of aquatic plants. 87 



Experiments with Hottonia palustris. 



Only two experiments were made with this species : the results 

 agree with those obtained for Elodea. 



Experiment 11 : 10th June, 1895. 

 Hottonia. 



Experiment 12: loth August, 1895. 

 Hottonia. Old Tap-water. 



Experiments with Potamogeton bilupsii. 



This plant, which is said to be a cross between P. coriaceus and 

 P. plantagineus, happened to occur in convenient quantities in the 

 Botanic Garden and was therefore used. 



The results were of a conflicting character : in two experiments 

 in which freshly-drawn tap-water was used, the stirring un- 

 doubtedly produced an increase in the yield of gas. But in the 

 other ten experiments for which water was used which had stood 

 in an open vessel for twenty-four hours, the stirring produced 

 either increase or decrease or else was without effect on the yield 

 of gas. 



